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Horseshoe crab
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<h2 id="phylogeny-and-evolution">Phylogeny and evolution</h2> <p>The fossil record of <a href="/facts/Xiphosura/C2JVjLpj">xiphosurans</a> extends back to the <a href="/facts/Late_Ordovician/BjMrLIEA">Late Ordovician</a>, or around 445 million years ago.<a class="footnote-ref" id="fnref:1" href="#fn:1"><sup>1</sup></a> For modern horseshoe crabs, their earliest appearance was approximately 250 million years ago during the <a href="/facts/Early_Triassic/oBgudq2V">Early Triassic</a>.<a class="footnote-ref" id="fnref:2" href="#fn:2"><sup>2</sup></a> Because they have seen little morphological change since then, extant (surviving) forms have been described as "<a href="/facts/Living_fossils/EujFvU2D">living fossils</a>".<a class="footnote-ref" id="fnref:3" href="#fn:3"><sup>3</sup></a> </p><p>Horseshoe crabs resemble <a href="/facts/Crustacean/PBobIVJP">crustaceans</a> but belong to a separate subphylum of the <a href="/facts/Arthropod/JKJLTFzp">arthropods</a>, <a href="/facts/Chelicerata/9YNa15kz">Chelicerata</a>. Horseshoe crabs are closely related to the extinct <a href="/facts/Eurypterid/w1GHNTAB">eurypterids</a> (sea scorpions), which include some of the largest arthropods ever to have existed, and the two may be <a href="/facts/Sister_group/pNNuVex4">sister groups</a>.<a class="footnote-ref" id="fnref:4" href="#fn:4"><sup>4</sup></a> The difficult-to-classify <a href="/facts/Chasmataspidid/Lb7jBaGv">chasmataspidids</a> are also thought to be closely related to horseshoe crabs.<a class="footnote-ref" id="fnref:5" href="#fn:5"><sup>5</sup></a><a class="footnote-ref" id="fnref:6" href="#fn:6"><sup>6</sup></a> </p><p>The <a href="/facts/Evolutionary_radiation/DDc0R6GS">radiation</a> of horseshoe crabs resulted in 22 known species, of which only 4 remain.<a class="footnote-ref" id="fnref:7" href="#fn:7"><sup>7</sup></a> The <a href="/facts/Atlantic_Ocean/EI4uChIb">Atlantic</a> species is sister to the three Asian species, the latter of which are likely the result of two divergences relatively close in time.<a class="footnote-ref" id="fnref:8" href="#fn:8"><sup>8</sup></a> The last common ancestor of the four extant species is estimated to have lived about 135 million years ago in the <a href="/facts/Cretaceous/nwKtFtKx">Cretaceous</a>.<a class="footnote-ref" id="fnref:9" href="#fn:9"><sup>9</sup></a> </p><p>Limulidae is the only extant <a href="/facts/Family_(biology)/qTrn6E8E">family</a> of the <a href="/facts/Order_(biology)/GKLJvIpt">order</a> <a href="/facts/Xiphosura/C2JVjLpj">Xiphosura</a>, and contains all four living <a href="/facts/Species/oDg6b96r">species</a> of horseshoe crabs:<a class="footnote-ref" id="fnref:10" href="#fn:10"><sup>10</sup></a><a class="footnote-ref" id="fnref:11" href="#fn:11"><sup>11</sup></a> </p> <ul><li><i><a href="/facts/Mangrove_horseshoe_crab/XwycKvzE">Carcinoscorpius rotundicauda</a></i>, the mangrove horseshoe crab, found in South and Southeast Asia</li> <li><i><a href="/facts/Atlantic_horseshoe_crab/lJlYkhfC">Limulus polyphemus</a></i>, the Atlantic or American horseshoe crab, found along the Atlantic coast of the United States and the Southeast Gulf of Mexico</li> <li><i><a href="/facts/Tachypleus_gigas/24wTm3oJ">Tachypleus gigas</a></i>, the Indo-Pacific, Indonesian, Indian, or southern horseshoe crab, found in South and Southeast Asia</li> <li><i><a href="/facts/Tachypleus_tridentatus/BkvjmNDK">Tachypleus tridentatus</a></i>, the Chinese, Japanese, or tri-spine horseshoe crab, found in Southeast and East Asia</li></ul> <h3>Genera</h3> <p>After Bicknell et al. 2021 and Lamsdell et al. 2020<a class="footnote-ref" id="fnref:12" href="#fn:12"><sup>12</sup></a><a class="footnote-ref" id="fnref:13" href="#fn:13"><sup>13</sup></a> </p> <ul><li><i><a href="/facts/Incertae_sedis/kWyo2wYR">Uncertain Placement</a></i> <ul><li>†<i>Albalimulus</i>? Bicknell & Pates, 2019<a class="footnote-ref" id="fnref:14" href="#fn:14"><sup>14</sup></a> <a href="/facts/Ballagan_Formation/v0D2AsXN">Ballagan Formation</a>, Scotland, Early <a href="/facts/Carboniferous/BRKlkYyd">Carboniferous</a> (<a href="/facts/Tournaisian/5fc51hec">Tournaisian</a>) (Considered Xiphosura <i>incertae sedis</i> by Lamsdell, 2020<a class="footnote-ref" id="fnref:15" href="#fn:15"><sup>15</sup></a>)</li> <li>†<i><a href="/facts/Casterolimulus/paRFmpaA">Casterolimulus</a></i> Holland, Erickson & O'Brien, 1975 Late Cretaceous (<a href="/facts/Maastrichtian/xRBafamu">Maastrichtian</a>) <a href="/facts/Fox_Hills_Formation/Cds9CD88">Fox Hills Formation</a>, North Dakota, USA (Inconsistently placed in this family)</li> <li>†<i><a href="/facts/Heterolimulus/LjP4qRTc">Heterolimulus</a></i> gadeai Vıa & Villalta, 1966 Alcover Limestone Formation, Spain, <a href="/facts/Middle_Triassic/Y0FBoqA8">Middle Triassic</a> (<a href="/facts/Ladinian/X9RUy1R2">Ladinian</a>)</li> <li>†<i><a href="/facts/Limulitella/u1J2lPzq">Limulitella</a>?</i> Størmer, 1952 Middle-Upper Triassic, France, Germany, Tunisia, Russia</li> <li>†<i>Sloveniolimulus</i> Bicknell et al., 2019 Strelovec Formation, Slovenia Middle Triassic (<a href="/facts/Anisian/ck89Rqhu">Anisian</a>)</li> <li>†<i>Tarracolimulus</i> Romero & Vıa Boada, 1977 Alcover Limestone Formation, Spain, Middle Triassic (Ladinian)</li> <li>†<i><a href="/facts/Victalimulus/AfX6TGwN">Victalimulus</a></i> Riek & Gill, 1971 <a href="/facts/Early_Cretaceous/5uWEJGYC">Lower Cretaceous</a> (<a href="/facts/Aptian/nXFfjnyR">Aptian</a>) Korumburra Group, NSW, Australia</li> <li>†<i>Yunnanolimulus</i> Zhang et al., 2009 Middle Triassic (Anisian), <a href="/facts/Guanling_Formation/5L69yvg5">Guanling Formation</a>, Yunnan, China</li> <li>†<i><a href="/facts/Mesolimulus/5MxFAkn2">Mesolimulus</a></i> Middle Triassic-Late Cretaceous England, Spain, <a href="/facts/Siberia/oaCoPEjF">Siberia</a>, Germany, Morocco</li> <li>†<i>Ostenolimulus</i> Lamsdell et al. 2021<a class="footnote-ref" id="fnref:16" href="#fn:16"><sup>16</sup></a> Early Jurassic (<a href="/facts/Sinemurian/D1W2Uwd9">Sinemurian</a>) <a href="/facts/Moltrasio_Formation/ExTRcY7a">Moltrasio Limestone</a>, Italy</li> <li>†<i>Volanalimulus</i> Lamsdell, 2020<a class="footnote-ref" id="fnref:17" href="#fn:17"><sup>17</sup></a> Early Triassic, Madagascar.</li></ul></li> <li>Subfamily Limulinae Leach, 1819 <ul><li>†<i>Crenatolimulus</i> Feldmann et al., 2011 Upper Jurassic (upper <a href="/facts/Tithonian/LbjgN2Yj">Tithonian</a>) Kcynia Formation, Poland. Lower Cretaceous (<a href="/facts/Albian/faHcmHDC">Albian</a>) <a href="/facts/Glen_Rose_Formation/0hAQpuSW">Glen Rose Formation</a>, Texas, USA</li> <li><i><a href="/facts/Limulus/QT4e4wkd">Limulus</a></i> <a href="/facts/Otto_Friedrich_M%25C3%25BCller/5MnognyI">O. F. Müller</a>, 1785 <a href="/facts/Pierre_Shale/dt1muVf7">Pierre Shale</a>, <a href="/facts/United_States/P0sCdLe5">United States</a>, Late Cretaceous (<a href="/facts/Maastrichtian/xRBafamu">Maastrichtian</a>), Atlantic North America, Recent</li></ul></li> <li>Subfamily Tachypleinae Pocock, 1902 <ul><li><i><a href="/facts/Carcinoscorpius/XwycKvzE">Carcinoscorpius</a></i> Pocock, 1902, Asia, Recent</li> <li><i><a href="/facts/Tachypleus/LjP4qRTc">Tachypleus</a></i> Leach, 1819 Upper Cretaceous (<a href="/facts/Cenomanian/atR50Pe7">Cenomanian</a>) Haqel and <a href="/facts/Sannine_Formation/6EkH3okw">Hjoula Konservat-Lagerstatten</a>, Lebanon, Upper <a href="/facts/Eocene/EYgI8Uco">Eocene</a> Domsen Sands, Germany, Asia, Recent</li></ul></li></ul> <h3>Phylogeny</h3> <p>The horseshoe crab's position within <a href="/facts/Chelicerata/9YNa15kz">Chelicerata</a> is complicated. However, most morphological analyses have placed them outside the <a href="/facts/Arachnid/xPJbsLga">Arachnida</a>.<a class="footnote-ref" id="fnref:18" href="#fn:18"><sup>18</sup></a><a class="footnote-ref" id="fnref:19" href="#fn:19"><sup>19</sup></a><a class="footnote-ref" id="fnref:20" href="#fn:20"><sup>20</sup></a><a class="footnote-ref" id="fnref:21" href="#fn:21"><sup>21</sup></a><a class="footnote-ref" id="fnref:22" href="#fn:22"><sup>22</sup></a> This assumption was challenged when a genetics-based <a href="/facts/Phylogenetic_tree/f5vVEpeY">phylogeny</a> found horseshoe crabs to be the sister group to the <a href="/facts/Ricinulei/QodJckDz">ricinuleids</a>, thereby making them an <a href="/facts/Arachnid/xPJbsLga">arachnid</a>.<a class="footnote-ref" id="fnref:23" href="#fn:23"><sup>23</sup></a> In response, a more recent paper has again placed horseshoe crabs as separate from the arachnids. This new study utilized both new and more complete <a href="/facts/Nucleic_acid_sequence/qAf4kTee">sequencing data</a> while also sampling a larger number of <a href="/facts/Taxon/caQC1e87">taxa</a>.<a class="footnote-ref" id="fnref:24" href="#fn:24"><sup>24</sup></a> </p><p> Below is a <a href="/facts/Cladogram/fWFYhUFo">cladogram</a> showing the internal relationships of Limulidae (modern horseshoe crabs) based on morphology. It contains both extant and extinct members.<a class="footnote-ref" id="fnref:25" href="#fn:25"><sup>25</sup></a></p> <table><tbody><tr><td>Limulidae</td><td rowspan="2"><table><tbody><tr><td></td><td rowspan="2"><table><tbody><tr><td></td><td rowspan="2"><table><tbody><tr><td></td><td rowspan="2"><table><tbody><tr><td></td><td rowspan="2"><table><tbody><tr><td></td><td rowspan="2"><table><tbody><tr><td>Tachypleinae</td><td rowspan="2"><table><tbody><tr><td></td><td rowspan="2"><p><i><a href="/facts/Carcinoscorpius_rotundicauda/XwycKvzE">Carcinoscorpius rotundicauda</a></i></p></td></tr><tr><td></td></tr><tr><td><i><a href="/facts/Tachypleus/LjP4qRTc">Tachypleus</a></i></td><td rowspan="2"><table><tbody><tr><td></td><td rowspan="2"><table><tbody><tr><td></td><td rowspan="2"><p><i><a href="/facts/Tachypleus_gigas/24wTm3oJ">Tachypleus gigas</a></i></p></td></tr><tr><td></td></tr><tr><td></td><td rowspan="2"><p>† <i>Tachypleus decheni</i></p></td></tr><tr><td></td></tr></tbody></table></td></tr><tr><td></td></tr><tr><td></td><td rowspan="2"><table><tbody><tr><td></td><td rowspan="2"><p>† <i>Tachypleus syriacus</i></p></td></tr><tr><td></td></tr><tr><td></td><td rowspan="2"><p><i><a href="/facts/Tachypleus_tridentatus/BkvjmNDK">Tachypleus tridentatus</a></i></p></td></tr><tr><td></td></tr></tbody></table></td></tr><tr><td></td></tr></tbody></table></td></tr><tr><td></td></tr></tbody></table></td></tr><tr><td></td></tr><tr><td></td><td rowspan="2"><p>† <i><a href="/facts/Heterolimulus/LjP4qRTc">Heterolimulus gadeai</a></i></p></td></tr><tr><td></td></tr></tbody></table></td></tr><tr><td></td></tr><tr><td></td><td rowspan="2"><p>† <i>Volanalimulus madagascarensis</i></p></td></tr><tr><td></td></tr></tbody></table></td></tr><tr><td></td></tr><tr><td>Limulinae</td><td rowspan="2"><table><tbody><tr><td></td><td rowspan="2"><table><tbody><tr><td></td><td rowspan="2"><p><i><a href="/facts/Limulus_polyphemus/lJlYkhfC">Limulus polyphemus</a></i></p></td></tr><tr><td></td></tr><tr><td></td><td rowspan="2"><p>† <i>Limulus coffini</i></p></td></tr><tr><td></td></tr></tbody></table></td></tr><tr><td></td></tr><tr><td><i>Crenatolimulus</i></td><td rowspan="2"><table><tbody><tr><td></td><td rowspan="2"><p>† <i>Crenatolimulus paluxyensis</i></p></td></tr><tr><td></td></tr><tr><td></td><td rowspan="2"><p>† <i>Crenatolimulus darwini</i></p></td></tr><tr><td></td></tr></tbody></table></td></tr><tr><td></td></tr></tbody></table></td></tr><tr><td></td></tr></tbody></table></td></tr><tr><td></td></tr><tr><td></td><td rowspan="2"><table><tbody><tr><td></td><td rowspan="2"><p>† <i>Keuperlimulus vicensis</i></p></td></tr><tr><td></td></tr><tr><td></td><td rowspan="2"><table><tbody><tr><td></td><td rowspan="2"><table><tbody><tr><td></td><td rowspan="2"><table><tbody><tr><td></td><td rowspan="2"><p>† <i><a href="/facts/Casterolimulus/paRFmpaA">Casterolimulus kletti</a></i></p></td></tr><tr><td></td></tr><tr><td></td><td rowspan="2"><p>† <i><a href="/facts/Victalimulus/AfX6TGwN">Victalimulus mcqueeni</a></i></p></td></tr><tr><td></td></tr></tbody></table></td></tr><tr><td></td></tr><tr><td></td><td rowspan="2"><p>† <i>Allolimulus woodwardi</i></p></td></tr><tr><td></td></tr></tbody></table></td></tr><tr><td></td></tr><tr><td><i><a href="/facts/Mesolimulus/5MxFAkn2">Mesolimulus</a></i></td><td rowspan="2"><table><tbody><tr><td></td><td rowspan="2"><p>† <i><a href="/facts/Mesolimulus/5MxFAkn2">Mesolimulus crespelli</a></i></p></td></tr><tr><td></td></tr><tr><td></td><td rowspan="2"><table><tbody><tr><td></td><td rowspan="2"><table><tbody><tr><td></td><td rowspan="2"><p>† <i><a href="/facts/Mesolimulus/5MxFAkn2">Mesolimulus walchi</a></i></p></td></tr><tr><td></td></tr><tr><td></td><td rowspan="2"><p>† <i><a href="/facts/Mesolimulus/5MxFAkn2">Mesolimulus tafraoutensis</a></i></p></td></tr><tr><td></td></tr></tbody></table></td></tr><tr><td></td></tr><tr><td></td><td rowspan="2"><p>† <i><a href="/facts/Mesolimulus/5MxFAkn2">Mesolimulus sibiricus</a></i></p></td></tr><tr><td></td></tr></tbody></table></td></tr><tr><td></td></tr></tbody></table></td></tr><tr><td></td></tr></tbody></table></td></tr><tr><td></td></tr></tbody></table></td></tr><tr><td></td></tr></tbody></table></td></tr><tr><td></td></tr><tr><td></td><td rowspan="2"><p>†<i> Tarracolimulus rieki</i></p></td></tr><tr><td></td></tr></tbody></table></td></tr><tr><td></td></tr><tr><td><i>Yunnanolimulus</i></td><td rowspan="2"><table><tbody><tr><td></td><td rowspan="2"><p>† <i>Yunnanolimulus henkeli</i></p></td></tr><tr><td></td></tr><tr><td></td><td rowspan="2"><p>† <i>Yunnanolimulus luopingensis</i></p></td></tr><tr><td></td></tr></tbody></table></td></tr><tr><td></td></tr></tbody></table></td></tr><tr><td></td></tr></tbody></table> <h3>Whole genome duplication</h3> <p>The <a href="/facts/Common_ancestor/bwEgMu7F">common ancestor</a> of <a href="/facts/Arachnid/xPJbsLga">arachnids</a> and <a href="/facts/Xiphosura/C2JVjLpj">xiphosurans</a> (the group that includes horseshoe crabs) underwent a <a href="/facts/Whole-genome_duplication/cgAIqgkG">whole-genome duplication</a> (WGD) event.<a class="footnote-ref" id="fnref:26" href="#fn:26"><sup>26</sup></a><a class="footnote-ref" id="fnref:27" href="#fn:27"><sup>27</sup></a> This was followed by at least two, possibly three, WGDs in a common ancestor of the living horseshoe crabs.<a class="footnote-ref" id="fnref:28" href="#fn:28"><sup>28</sup></a> This gives them unusually large <a href="/facts/Genome/tjhWET4V">genomes</a> for <a href="/facts/Invertebrate/3CyqCVnN">invertebrates</a> (the genomes of <i><a href="/facts/Mangrove_horseshoe_crab/XwycKvzE">C. rotundicauda</a></i> and <a href="/facts/Tachypleus_tridentatus/BkvjmNDK"><i>T. tridentatus</i></a> being approximately 1.72 Gb each).<a class="footnote-ref" id="fnref:29" href="#fn:29"><sup>29</sup></a> Evidence for the duplication events includes similarity in structure between chromosomes (<a href="/facts/Synteny/e50mAKmN">synteny</a>), and clustering of <a href="/facts/Homeobox_genes/bpvuuw3v">homeobox genes</a>. Over time, many of the duplicated <a href="/facts/Gene/e1swwPY6">genes</a> have changed through processes of <a href="/facts/Neofunctionalization/BCfPYEhz">neofunctionalization</a> or <a href="/facts/Subfunctionalization/0SDWfvcf">subfunctionalization</a>, meaning their functions are different from what they originally were.<a class="footnote-ref" id="fnref:30" href="#fn:30"><sup>30</sup></a> </p> <h3>Evolution of sexual size dimorphism</h3> <p>Several <a href="/facts/Hypothesis/gMABEJul">hypotheses</a> have been given as possible reasons why a size difference exists between male and female horseshoe crabs<a class="footnote-ref" id="fnref:31" href="#fn:31"><sup>31</sup></a> This phenomenon is known as <a href="/facts/Sexual_dimorphism/nx9wulFy">sexual size dimorphism</a> and results in the females having a larger average size than males.<a class="footnote-ref" id="fnref:32" href="#fn:32"><sup>32</sup></a> The existence of this trend is likely due to a combination of two things: </p> <ol><li>First, females take a year longer to mature and undergo an additional molt, giving them a larger average body size.<a class="footnote-ref" id="fnref:33" href="#fn:33"><sup>33</sup></a></li> <li>Second, larger female horseshoe crabs can house more eggs within their bodies. This lets them pass on more genetic material than smaller females during each mating cycle, making larger females more prevalent.<a class="footnote-ref" id="fnref:34" href="#fn:34"><sup>34</sup></a></li></ol> <h2 id="anatomy-and-physiology">Anatomy and physiology</h2> <h3>General body plan</h3> <p>Like all <a href="/facts/Arthropod/JKJLTFzp">arthropods</a>, horseshoe crabs have segmented bodies with jointed limbs, which are covered by a protective <a href="/facts/Arthropod_exoskeleton/HuUI5fse">cuticle</a> made of <a href="/facts/Chitin/Fo1f8b86">chitin</a>. They have heads composed of several segments, which eventually fuse as an embryo.<a class="footnote-ref" id="fnref:35" href="#fn:35"><sup>35</sup></a>: 518–522 </p><p>Horseshoe crabs are chelicerates, meaning their bodies are composed of two main parts (<a href="/facts/Tagma_(biology)/ElNc6GUo">tagma</a>): the <a href="/facts/Cephalothorax/0CER7JDU">cephalothorax</a> and the <a href="/facts/Opisthosoma/rXmmsVrX">opisthosoma</a>. The first tagma, the cephalothorax or <a href="/facts/Prosoma/0CER7JDU">prosoma</a>, is a fusion of the <a href="/facts/Cephalon_(arthropod_head)/CGElwBtl">head</a> and <a href="/facts/Thorax_(arthropod_anatomy)/YkvR8QJn">thorax</a>.<a class="footnote-ref" id="fnref:36" href="#fn:36"><sup>36</sup></a>: 555 This tagma is also covered by a large, semicircular, <a href="/facts/Carapace/8VnnWH2b">carapace</a> that acts like a shield around the animal's body. It is shaped like the hoof of a horse, giving this animal its common name.<a class="footnote-ref" id="fnref:37" href="#fn:37"><sup>37</sup></a>: 555 In addition to the two main tagmata, the horseshoe crab also possesses a long tail-like section known as the <a href="/facts/Telson/71eFnSJb">telson</a>.<a class="footnote-ref" id="fnref:38" href="#fn:38"><sup>38</sup></a>: 555 </p><p>In total, horseshoe crabs have 6 pairs of appendages on their <a href="/facts/Cephalothorax/0CER7JDU">cephalothorax</a>. The first of these are the <a href="/facts/Chelicerae/TAkw3S2g">chelicerae</a>, which give <a href="/facts/Chelicerata/9YNa15kz">chelicerates</a> their name. In horseshoe crabs, these look like tiny pincers in front of the mouth.<a class="footnote-ref" id="fnref:39" href="#fn:39"><sup>39</sup></a>: 555 Behind the chelicerae are the <a href="/facts/Pedipalp/mdd5FmrQ">pedipalps</a>, which are primarily used as legs. In the final molt of males, the ends of the pedipalps are modified into specialized, grasping claws used in mating.<a class="footnote-ref" id="fnref:40" href="#fn:40"><sup>40</sup></a>: 555 Following the pedipalps are three pairs of walking legs and a set of pusher legs for moving through soft sediment.<a class="footnote-ref" id="fnref:41" href="#fn:41"><sup>41</sup></a>: 555 Each of these pusher legs is <a href="/facts/Biramous/Lhs5yVca">biramous</a> or divided into two separate branches. The branch closest to the front bears a flat end that looks like a leaf. This end is called the flabellum. The branch towards the back is far longer and looks similar to a walking leg. However, rather than ending in just a claw, the back branch has four leaf-like ends that are arranged like a <a href="/facts/Petal/BcMcG97l">petal</a>.<a class="footnote-ref" id="fnref:42" href="#fn:42"><sup>42</sup></a>: 555 The final segment of the cephalothorax was originally part of the abdomen but fused in the embryo. On it are two flap-like appendages known as <a href="/facts/Chilaria/C2JVjLpj">chilaria</a>.<a class="footnote-ref" id="fnref:43" href="#fn:43"><sup>43</sup></a>: 556 If severed from the body, lost legs or the telson may slowly regenerate, and cracks in the body shell can heal.<a class="footnote-ref" id="fnref:44" href="#fn:44"><sup>44</sup></a> </p> <p>The <a href="/facts/Opisthosoma/rXmmsVrX">opisthosoma</a> or abdomen of a horseshoe crab is composed of several fused segments.<a class="footnote-ref" id="fnref:45" href="#fn:45"><sup>45</sup></a>: 556 Similar to a <a href="/facts/Trilobite/Tk8ppaKc">trilobite</a>, the abdomen is made up of three lobes: a medial lobe in the middle, and a pleural lobe on either side.<a class="footnote-ref" id="fnref:46" href="#fn:46"><sup>46</sup></a> Attached to the perimeter of each pleural lobe is a flat, serrated structure known as the flange. The flange on either side is connected by the telson embayment, which itself is attached to the medial lobe.<a class="footnote-ref" id="fnref:47" href="#fn:47"><sup>47</sup></a> Along the line where these lobes meet are six sets of indentations known as <a href="/facts/Apodeme/Wlmru4GW">apodeme</a>. Each of these serves as a muscle attachment point for the animal's twelve movable spines.<a class="footnote-ref" id="fnref:48" href="#fn:48"><sup>48</sup></a> </p><p>On the underside of the abdomen are several <a href="/facts/Arthropod_leg/Lhs5yVca">biramous</a> limbs. The branches closest to the outside are flat and broad, while the ones on the inside are more narrow.<a class="footnote-ref" id="fnref:49" href="#fn:49"><sup>49</sup></a>: 556 Closest to the front is a plate-like structure made of two fused appendages. This is the genital operculum and is where horseshoe crabs keep their <a href="/facts/Gonad/36BUam2x">reproductive organs</a>.<a class="footnote-ref" id="fnref:50" href="#fn:50"><sup>50</sup></a>: 556 Following the operculum are five pairs of <a href="/facts/Book_gill/LdAjv6HT">book gills</a>. While mainly used for breathing, horseshoe crabs can also use their book gills to swim.<a class="footnote-ref" id="fnref:51" href="#fn:51"><sup>51</sup></a>: 556 At the end of a horseshoe crab's abdomen is a long, tail-like spine known as a <a href="/facts/Telson/71eFnSJb">telson</a>. It is highly mobile and serves a variety of functions.<a class="footnote-ref" id="fnref:52" href="#fn:52"><sup>52</sup></a>: 556 </p> <h3>Nervous system</h3> <h4>Eyes</h4> <p>Horseshoe crabs have a variety of <a href="/facts/Eye/h3lbYU55">eyes</a> that provide them with useful visual information. The most obvious of these are two large <a href="/facts/Compound_eye/h3lbYU55">compound eyes</a> found on top of the <a href="/facts/Carapace/8VnnWH2b">carapace</a>. This feature is unusual, as all other living <a href="/facts/Chelicerata/9YNa15kz">chelicerates</a> have lost them in their <a href="/facts/Evolution/qE5amP6a">evolution</a>.<a class="footnote-ref" id="fnref:53" href="#fn:53"><sup>53</sup></a><a class="footnote-ref" id="fnref:54" href="#fn:54"><sup>54</sup></a> In adult horseshoe crabs, the compound eyes comprise around 1,000 individual units known as <a href="/facts/Ommatidium/T2jummw4">ommatidia</a>. Each ommatidium is made up of a ring of <a href="/facts/Photoreceptor_cell/Ap0DcW5N">retinal</a> and <a href="/facts/Chromatophore/lPNvER8t">pigment cells</a> that surround something known as the eccentric cell.<a class="footnote-ref" id="fnref:55" href="#fn:55"><sup>55</sup></a> This secondary visual cell gets its name from the way it behaves. The eccentric cell is coupled with the <a href="/facts/Dendrite/bwv8MABY">dendrites</a> of normal retinal cells so that when a normal cell <a href="/facts/Depolarization/qGX8lFXE">depolarizes</a> in the presence of <a href="/facts/Light/jeofpMn4">light</a>, the eccentric cell does too.<a class="footnote-ref" id="fnref:56" href="#fn:56"><sup>56</sup></a> </p><p>A horseshoe crab's <a href="/facts/Compound_eye/h3lbYU55">compound eyes</a> are less complex and organized than those of most other <a href="/facts/Arthropod/JKJLTFzp">arthropods</a>. <a href="/facts/Ommatidium/T2jummw4">Ommatidia</a> are arranged messily in what's been deemed an "imperfect hexagonal array" and have a highly variable number of <a href="/facts/Photoreceptor_cell/Ap0DcW5N">photoreceptors</a> (between 4 and 20) in their <a href="/facts/Retina/v0ISNX2S">retina</a>.<a class="footnote-ref" id="fnref:57" href="#fn:57"><sup>57</sup></a> Although each ommatidium typically has one eccentric cell, there are sometimes two, and occasionally more.<a class="footnote-ref" id="fnref:58" href="#fn:58"><sup>58</sup></a> All the eye's photoreceptors, both <a href="/facts/Rod_cell/mNd9Sf1E">rods</a> and <a href="/facts/Cone_cell/JoQeEzoF">cones</a>, have a single <a href="/facts/Photoreceptor_protein/xEa6hcY7">visual pigment</a> with a peak absorption of around 525 nanometers. This differs from <a href="/facts/Insects/IgDNvnUL">insects</a> or <a href="/facts/Decapoda/MycLb6mz">decapod crustaceans</a>, as their photoreceptors are sensitive to different spectrums of light.<a class="footnote-ref" id="fnref:59" href="#fn:59"><sup>59</sup></a> Horseshoe crabs have relatively poor vision, and to compensate for that, have the largest rods and cones of any known animal, about 100 times the size of humans'.<a class="footnote-ref" id="fnref:60" href="#fn:60"><sup>60</sup></a><a class="footnote-ref" id="fnref:61" href="#fn:61"><sup>61</sup></a> Furthermore, their eyes are a million times more sensitive to light at night than during the day.<a class="footnote-ref" id="fnref:62" href="#fn:62"><sup>62</sup></a> </p><p>At the front of the animal along the cardiac ridge are a pair of eyes known as <a href="/facts/Simple_eye_in_invertebrates/zV5g5Eqo">median ocelli</a>.<a class="footnote-ref" id="fnref:63" href="#fn:63"><sup>63</sup></a><a class="footnote-ref" id="fnref:64" href="#fn:64"><sup>64</sup></a> Their retina is even less organized than those of the compound eyes having between 5 and 11 <a href="/facts/Photoreceptor_cell/Ap0DcW5N">photoreceptors</a> paired with one or two secondary visual cells called arhabdomeric cells. Arhabdomeric cells are equivalent to eccentric cells as they function identically.<a class="footnote-ref" id="fnref:65" href="#fn:65"><sup>65</sup></a> The median ocelli are unique due to having two distinct <a href="/facts/Photoreceptor_protein/xEa6hcY7">visual pigments</a>. While the first functions similarly to the pigment in the compound eyes, the second has a peak absorption of around 360 nanometers, allowing the animal to see <a href="/facts/Ultraviolet/kncBUqn5">ultraviolet light</a>.<a class="footnote-ref" id="fnref:66" href="#fn:66"><sup>66</sup></a><a class="footnote-ref" id="fnref:67" href="#fn:67"><sup>67</sup></a> </p><p>Other, more rudimentary eyes in horseshoe crabs include the endoparietal ocelli, the two lateral ocelli, two ventral ocelli, and a cluster of <a href="/facts/Photoreceptor_cell/Ap0DcW5N">photoreceptors</a> on the abdomen and telson.<a class="footnote-ref" id="fnref:68" href="#fn:68"><sup>68</sup></a><a class="footnote-ref" id="fnref:69" href="#fn:69"><sup>69</sup></a> The endoparietal, lateral, and ventral ocelli are very similar to the median ocelli, except like the compound eyes, they only see in visual light with a peak absorbance of around 525 nanometers.<a class="footnote-ref" id="fnref:70" href="#fn:70"><sup>70</sup></a> The endoparietal eye further differs due to being a fusion of two separate <a href="/facts/Ocelli/zV5g5Eqo">ocelli</a>.<a class="footnote-ref" id="fnref:71" href="#fn:71"><sup>71</sup></a> This eye is found not far behind the median eyes and sits directly on the cardiac ridge.<a class="footnote-ref" id="fnref:72" href="#fn:72"><sup>72</sup></a> The two ventral ocelli are located on the underside of the <a href="/facts/Cephalothorax/0CER7JDU">cephalothorax</a> near the mouth and likely help to orient the animal when walking around or swimming.<a class="footnote-ref" id="fnref:73" href="#fn:73"><sup>73</sup></a> The lateral eyes can be found directly behind the <a href="/facts/Compound_eye/h3lbYU55">compound eyes</a> and become functional just before a horseshoe crab larvae hatch.<a class="footnote-ref" id="fnref:74" href="#fn:74"><sup>74</sup></a> The telson's photoreceptors are unique as they're spaced throughout the structure rather than located in a fixed spot. Together with <a href="/facts/Ultraviolet/kncBUqn5">UV</a>-seeing median ocelli, these photoreceptors have been found to influence the animal's <a href="/facts/Circadian_rhythm/rwQh0ClJ">circadian rhythm</a>.<a class="footnote-ref" id="fnref:75" href="#fn:75"><sup>75</sup></a> </p> <h3>Circulation and respiration</h3> <p>Like all <a href="/facts/Arthropod/JKJLTFzp">arthropods</a>, horseshoe crabs have an <a href="/facts/Open_circulation/WXwudzzc">open circulatory system</a>.<a class="footnote-ref" id="fnref:76" href="#fn:76"><sup>76</sup></a>: 558 This means that instead of using a system of closed-off <a href="/facts/Vein/I6ycr6gF">veins</a> and <a href="/facts/Artery/Y1Yj0jat">arteries</a>, gasses are transported through a <a href="/facts/Body_cavity/cPMtaaeC">cavity</a> called the hemocoel.<a class="footnote-ref" id="fnref:77" href="#fn:77"><sup>77</sup></a>: 558 The hemocoel contains <a href="/facts/Hemolymph/6tHgrY6c">hemolymph</a>, a fluid that fills all parts of the cavity and serves as the animal's blood.<a class="footnote-ref" id="fnref:78" href="#fn:78"><sup>78</sup></a>: 558 Rather than using <a href="/facts/Iron/DkICCKIC">iron</a>-based <a href="/facts/Hemoglobin/RsD1MzYA">hemoglobin</a>, horseshoe crabs transport <a href="/facts/Oxygen/acyn6o8r">oxygen</a> with a <a href="/facts/Copper/I8PEE8oX">copper</a>-based protein called <a href="/facts/Hemocyanin/kCxIlQW9">hemocyanin</a>, giving its <a href="/facts/Blood/03zEulkj">blood</a> a bright blue color.<a class="footnote-ref" id="fnref:79" href="#fn:79"><sup>79</sup></a>: 558 The blood also contains two types of cells: <a href="/facts/Amebocyte/RVIH4NoI">amebocytes</a> that are utilized in clotting, and cyanocytes that create <a href="/facts/Hemocyanin/kCxIlQW9">hemocyanin</a>.<a class="footnote-ref" id="fnref:80" href="#fn:80"><sup>80</sup></a>: 558 </p><p>Horseshoe crabs pump blood with a long, tubular <a href="/facts/Heart/fF4KSGdk">heart</a> located in the middle of their body.<a class="footnote-ref" id="fnref:81" href="#fn:81"><sup>81</sup></a>: 558 Like the hearts of <a href="/facts/Vertebrate/tT54FSTT">vertebrates</a>, the hearts of these animals have two separate states: a state of contraction known as <a href="/facts/Systole/5KDbjw4B">systole</a>, and a state of relaxation known as <a href="/facts/Diastole/keHgaxbF">diastole</a>.<a class="footnote-ref" id="fnref:82" href="#fn:82"><sup>82</sup></a>: 558 At the beginning of systole, <a href="/facts/Blood/03zEulkj">blood</a> leaves the heart through a large artery known as the aorta and numerous arteries parallel to the heart.<a class="footnote-ref" id="fnref:83" href="#fn:83"><sup>83</sup></a>: 558 Next, the arteries dump blood into large <a href="/facts/Sinus_(anatomy)/TdjefDG0">cavities of the hemocoel</a> surrounding the animal's <a href="/facts/Tissue_(biology)/H7CpML7A">tissues</a>. Larger cavities lead to smaller cavities, allowing the <a href="/facts/Hemocoel/WXwudzzc">hemocoel</a> to oxygenate all the animal's tissues.<a class="footnote-ref" id="fnref:84" href="#fn:84"><sup>84</sup></a>: 558 During diastole, blood flows from the hemocoel to a cavity known as the pericardial sinus. From there, blood re-enters the heart and the cycle begins again.<a class="footnote-ref" id="fnref:85" href="#fn:85"><sup>85</sup></a>: 558 </p><p>Horseshoe crabs breathe through modified swimming appendages beneath their abdomen known as <a href="/facts/Book_gills/LdAjv6HT">book gills</a>.<a class="footnote-ref" id="fnref:86" href="#fn:86"><sup>86</sup></a>: 556 While they appear smooth on the outside, the insides of these book gills are lined with several thin "pages" called lamellae.<a class="footnote-ref" id="fnref:87" href="#fn:87"><sup>87</sup></a>: 558 Each lamella is hollow and contains an extension of <a href="/facts/Hemocoel/WXwudzzc">hemocoel</a>, allowing gasses to diffuse between a Horseshoe crab's <a href="/facts/Blood/03zEulkj">blood</a> and external environment.<a class="footnote-ref" id="fnref:88" href="#fn:88"><sup>88</sup></a>: 558 There are roughly 80–200 lamellae present in each gill, with all ten of them giving the animal with a total breathing surface area of about two square meters.<a class="footnote-ref" id="fnref:89" href="#fn:89"><sup>89</sup></a>: 558 When underwater, the lamellae are routinely aerated by rhythmic movement of the book gills.<a class="footnote-ref" id="fnref:90" href="#fn:90"><sup>90</sup></a>: 558 These movements create a current that enters through two gaps between the <a href="/facts/Cephalothorax/0CER7JDU">cephalothorax</a> and abdomen and exits on either side of the <a href="/facts/Telson/71eFnSJb">telson</a>.<a class="footnote-ref" id="fnref:91" href="#fn:91"><sup>91</sup></a>: 558 </p> <h3>Feeding, digestion, and excretion</h3> <p>Horseshoe crabs first break up their food using <a href="/facts/Bristle/66z9yNmB">bristles</a> known as gnathobases located at the coxa or base of their <a href="/facts/Arthropod_leg/Lhs5yVca">walking limbs</a>.<a class="footnote-ref" id="fnref:92" href="#fn:92"><sup>92</sup></a>: 556 Gnathobases on the right and left legs form a cavity known as the food groove that begins near the pusher legs and extends to the animal's <a href="/facts/Mouth/WthDlXsC">mouth</a>.<a class="footnote-ref" id="fnref:93" href="#fn:93"><sup>93</sup></a>: 556 The end of the groove is closed off by the animal's <a href="/facts/Chilaria/C2JVjLpj">chilaria</a>.<a class="footnote-ref" id="fnref:94" href="#fn:94"><sup>94</sup></a>: 556 To break up any <a href="/facts/Food/RgNq6NAK">food</a>, each pair of coxa moves in the opposite direction parallel to the ones in front of and behind it.<a class="footnote-ref" id="fnref:95" href="#fn:95"><sup>95</sup></a>: 93 This motion happens while feeding and walking, pushing food towards the mouth.<a class="footnote-ref" id="fnref:96" href="#fn:96"><sup>96</sup></a>: 556–557 Horseshoe crabs catch soft prey with <a href="/facts/Chelae/nEQudqKl">claws</a> on their second to fifth legs and place them in the food groove to be ground up.<a class="footnote-ref" id="fnref:97" href="#fn:97"><sup>97</sup></a>: 94 For harder prey, Horseshoe crabs use a pair of stout, cuspid gnathobases (informally known as "nutcrackers") on the back of their sixth legs.<a class="footnote-ref" id="fnref:98" href="#fn:98"><sup>98</sup></a>: 94 After the food is sufficiently torn up, it is moved by the <a href="/facts/Chelicerae/TAkw3S2g">chelicerae</a> into the <a href="/facts/Mouth/WthDlXsC">mouth</a> for further <a href="/facts/Digestion/sjUBmhBS">digestion</a>.<a class="footnote-ref" id="fnref:99" href="#fn:99"><sup>99</sup></a> </p><p>Horseshoe crabs are some of the only living <a href="/facts/Chelicerata/9YNa15kz">chelicerates</a> with guts that can process solid food.<a class="footnote-ref" id="fnref:100" href="#fn:100"><sup>100</sup></a>: 556 Its digestive system is J-shaped, lined with a <a href="/facts/Cuticle/LWaIDBIG">cuticle</a>, and can be divided into three main sections: the foregut, midgut, and hindgut.<a class="footnote-ref" id="fnref:101" href="#fn:101"><sup>101</sup></a>: 556–557 The foregut is contained in the animal's <a href="/facts/Cephalothorax/0CER7JDU">cephalothorax</a> and comprises the <a href="/facts/Esophagus/XWa7WoWn">esophagus</a>, crop, and <a href="/facts/Gizzard/xGEzIoA5">gizzard</a>.<a class="footnote-ref" id="fnref:102" href="#fn:102"><sup>102</sup></a>: 557 The esophagus moves food from the mouth to the crop where it is stored before entering the gizzard.<a class="footnote-ref" id="fnref:103" href="#fn:103"><sup>103</sup></a>: 557 The gizzard is a muscular, toothed organ that serves to pulverize the food from the crop and regurgitate any indigestible particles.<a class="footnote-ref" id="fnref:104" href="#fn:104"><sup>104</sup></a>: 557 The foregut terminates in the <a href="/facts/Pyloric_sphincter/920mWuBz">pyloric valve and sphincter</a>, a muscular door of sorts that separates it from the midgut.<a class="footnote-ref" id="fnref:105" href="#fn:105"><sup>105</sup></a>: 557 </p><p>The midgut is composed of a short <a href="/facts/Stomach/Q4PPDGT6">stomach</a>, a long intestinal tube.<a class="footnote-ref" id="fnref:106" href="#fn:106"><sup>106</sup></a>: 557 Connected to the stomach are a pair of large, sack-like digestive ceca known as hepatopancreases.<a class="footnote-ref" id="fnref:107" href="#fn:107"><sup>107</sup></a>: 557 These ceca fill most of the <a href="/facts/Cephalothorax/0CER7JDU">cephalothoracic</a> and abdominal hemocoel and are where most <a href="/facts/Digestion/sjUBmhBS">digestion</a> and nutrient absorption takes place.<a class="footnote-ref" id="fnref:108" href="#fn:108"><sup>108</sup></a>: 557 Before and following digestion, the midgut lining (<a href="/facts/Epithelium/ecKHcHC3">epithelium</a>) secretes a <a href="/facts/Peritrophic_matrix/SMqB6CVE">peritrophic membrane</a> made of <a href="/facts/Chitin/Fo1f8b86">chitin</a> and <a href="/facts/Mucoprotein/komJuvgs">mucoproteins</a> that surrounds the food and later the <a href="/facts/Feces/r9HDKB8G">feces</a>.<a class="footnote-ref" id="fnref:109" href="#fn:109"><sup>109</sup></a>: 557 </p><p>Horseshoe crabs excrete waste through both their book gills and hindgut.<a class="footnote-ref" id="fnref:110" href="#fn:110"><sup>110</sup></a>: 558 Similar to many aquatic animals, horseshoe crabs have an <a href="/facts/Ammonotelic/qGH5b3od">ammonotelic metabolism</a> and eliminate ammonia and other small toxins through diffusion with their gills.<a class="footnote-ref" id="fnref:111" href="#fn:111"><sup>111</sup></a>: 558 After being processed in the midgut, waste is passed into a muscular tube known as the hindgut or <a href="/facts/Rectum/caqqyk2e">rectum</a> and then excreted from a <a href="/facts/Sphincter/tNRad48q">sphincter</a> known as the anus.<a class="footnote-ref" id="fnref:112" href="#fn:112"><sup>112</sup></a><a class="footnote-ref" id="fnref:113" href="#fn:113"><sup>113</sup></a>: 558 Externally, this opening is located on the bottom side of the animal right below its telson.<a class="footnote-ref" id="fnref:114" href="#fn:114"><sup>114</sup></a>: 558 </p> <h2 id="distribution-and-habitat">Distribution and habitat</h2> <p>In the modern day, horseshoe crabs have a relatively limited distribution.<a class="footnote-ref" id="fnref:115" href="#fn:115"><sup>115</sup></a> The three <a href="/facts/Asia/4IToYrrQ">Asian</a> species mainly occur in <a href="/facts/South_Asia/7gTqe3hY">South</a> and <a href="/facts/Southeast_Asia/VafwT517">Southeast Asia</a> along the <a href="/facts/Bay_of_Bengal/xqKAj4bJ">Bay of Bengal</a> and the coasts of <a href="/facts/Indonesia/vQnWU3IW">Indonesia</a>. A notable exception is the <a href="/facts/Tri-spine_horseshoe_crab/BkvjmNDK">tri-spine horseshoe crab</a>, whose range extends northward to the coasts of <a href="/facts/China/lTjIXY5p">China</a>, <a href="/facts/Taiwan/VcJoUD8w">Taiwan</a>, and <a href="/facts/Kyushu/eM5yaMe3">Southern Japan</a>.<a class="footnote-ref" id="fnref:116" href="#fn:116"><sup>116</sup></a> The American species lives from the coast of <a href="/facts/Nova_Scotia/RcmIvd1A">Nova Scotia</a> to the northern <a href="/facts/Gulf_of_Mexico/bGE5s57G">Gulf of Mexico</a>, with another population residing around the <a href="/facts/Yucat%25C3%25A1n_Peninsula/xGAcABhC">Yucatán Peninsula</a>.<a class="footnote-ref" id="fnref:117" href="#fn:117"><sup>117</sup></a> Extant horseshoe crabs generally live in <a href="/facts/Saline_water/Tgw5AgL8">salt water</a>, though one species, the <a href="/facts/Mangrove_horseshoe_crab/XwycKvzE">mangrove horseshoe crab</a> (<i>Carcinoscorpius</i>) is often found in more <a href="/facts/Brackish_water/f6z3UXCa">brackish</a> environments.<a class="footnote-ref" id="fnref:118" href="#fn:118"><sup>118</sup></a> </p> <h3>Past adaptation to freshwater</h3> <p>According to a phylogeny from 2015, now-extinct <a href="/facts/Xiphosura/C2JVjLpj">xiphosurans</a> traveled to <a href="/facts/Fresh_water/xMP2TxwI">freshwater</a> at least five times throughout history.<a class="footnote-ref" id="fnref:119" href="#fn:119"><sup>119</sup></a> This same transition happened twice in the horseshoe crabs <i><a href="/facts/Victalimulus/AfX6TGwN">Victalimulus</a></i> and <i><a href="/facts/Limulitella/u1J2lPzq">Limulitella</a></i>, with both inhabiting environments such as swamps and rivers.<a class="footnote-ref" id="fnref:120" href="#fn:120"><sup>120</sup></a> </p> <h2 id="behavior-and-life-history">Behavior and life history</h2> <h3>Diet</h3> <p>Horseshoe crabs eat primarily <a href="/facts/Annelid/PQvb7NAM">worms</a> and <a href="/facts/Mollusca/1elgknsQ">mollusks</a> living on the ocean floor. They may also feed on <a href="/facts/Crustacean/PBobIVJP">crustaceans</a> and even small <a href="/facts/Fish/fln4gH9V">fish</a>.<a class="footnote-ref" id="fnref:121" href="#fn:121"><sup>121</sup></a> Foraging usually takes place at night.<a class="footnote-ref" id="fnref:122" href="#fn:122"><sup>122</sup></a><a class="footnote-ref" id="fnref:123" href="#fn:123"><sup>123</sup></a> </p> <h3>Locomotion</h3> <p>Horseshoe crabs live a primarily <a href="/facts/Benthic_zone/N3lM6P7I">benthic</a> lifestyle, preferring to stay at the water's bottom. However, they're also known to swim.<a class="footnote-ref" id="fnref:124" href="#fn:124"><sup>124</sup></a> This behavior is widespread in young individuals or those traveling to the shore to <a href="/facts/Reproduction/nNu0F5Dy">breed</a>.<a class="footnote-ref" id="fnref:125" href="#fn:125"><sup>125</sup></a> Horseshoe crabs swim upside-down with their bodies pointed downwards at an angle. They use their <a href="/facts/Telson/71eFnSJb">telson</a> as a <a href="/facts/Rudder/w675HJUP">rudder</a>, changing direction towards where it moved.<a class="footnote-ref" id="fnref:126" href="#fn:126"><sup>126</sup></a> To swim, the animal's retracted legs move to the front of its <a href="/facts/Cephalothorax/0CER7JDU">cephalothorax</a>, extend, and stroke towards the back. This motion happens in unison with the genital operculum and the first three pairs of <a href="/facts/Book_gill/LdAjv6HT">book gills</a>.<a class="footnote-ref" id="fnref:127" href="#fn:127"><sup>127</sup></a> While the front appendages reset, the back two book gills perform a smaller stroke.<a class="footnote-ref" id="fnref:128" href="#fn:128"><sup>128</sup></a> </p><p>Horseshoe crabs have a variety of ways to right or flip themselves over.<a class="footnote-ref" id="fnref:129" href="#fn:129"><sup>129</sup></a> The most common method involves the animal arching its <a href="/facts/Opisthosoma/rXmmsVrX">opisthosoma</a> towards the <a href="/facts/Carapace/8VnnWH2b">carapace</a> and balancing its <a href="/facts/Telson/71eFnSJb">telson</a> on the substrate. The animal then moves the telson while beating its <a href="/facts/Arthropod_leg/Lhs5yVca">legs</a> and <a href="/facts/Book_gill/LdAjv6HT">gills</a>. This causes the animal to tilt and eventually flip over.<a class="footnote-ref" id="fnref:130" href="#fn:130"><sup>130</sup></a> Furthermore, horseshoe crabs can right themselves while swimming. This method involves the animal swimming to the bottom, rolling on its side, and touching the bottom with its pusher legs while still in the water column.<a class="footnote-ref" id="fnref:131" href="#fn:131"><sup>131</sup></a> </p> <h3>Growth and development</h3> <p>Baby horseshoe crabs begin their lives as a "trilobite larva", a name given due to their resemblance to a <a href="/facts/Trilobite/Tk8ppaKc">trilobite</a>.<a class="footnote-ref" id="fnref:132" href="#fn:132"><sup>132</sup></a>: 559 Upon hatching, <a href="/facts/Larva/GKo2FIew">larva</a> typically measure around 1 cm (1⁄2 in) long. Their <a href="/facts/Telson/71eFnSJb">telson</a> is small, and they lack three pairs of <a href="/facts/Book_gill/LdAjv6HT">book gills</a>.<a class="footnote-ref" id="fnref:133" href="#fn:133"><sup>133</sup></a>: 559 In all other respects, the larvae appear like minuscule adults.<a class="footnote-ref" id="fnref:134" href="#fn:134"><sup>134</sup></a>: 559 Baby horseshoe crabs can swim and burrow in sediment after emerging from their <a href="/facts/Egg/2a1McdtR">egg</a>.<a class="footnote-ref" id="fnref:135" href="#fn:135"><sup>135</sup></a>: 559 </p><p>As the larvae <a href="/facts/Moulting/2wdfTSL5">molt</a> into juveniles, their telson gets longer and they gain their missing book gills. Juveniles can attain a <a href="/facts/Carapace/8VnnWH2b">carapace</a> width of around 4 cm (1+1⁄2 in) in their first year. For each molt, the juvenile will grow about 33% larger.<a class="footnote-ref" id="fnref:136" href="#fn:136"><sup>136</sup></a> This process continues until the animal reaches its adult size.<a class="footnote-ref" id="fnref:137" href="#fn:137"><sup>137</sup></a> </p><p>When mature, female horseshoe crabs are typically 20–30% larger than males.<a class="footnote-ref" id="fnref:138" href="#fn:138"><sup>138</sup></a> The smallest species is the <a href="/facts/Mangrove_horseshoe_crab/XwycKvzE">mangrove horseshoe crab</a> (<i>C. rotundicauda</i>) and the largest is the <a href="/facts/Tachypleus_tridentatus/BkvjmNDK">tri-spine horseshoe crab</a> (<i>T. tridentatus</i>).<a class="footnote-ref" id="fnref:139" href="#fn:139"><sup>139</sup></a> </p><p>On average, males of <i>C. rotundicauda</i> are about 30 centimeters (12 inches) long, including a <a href="/facts/Telson/71eFnSJb">telson</a> that is about 15 cm (6 in), and a <a href="/facts/Carapace/8VnnWH2b">carapace</a> about 15 cm (6 in) wide.<a class="footnote-ref" id="fnref:140" href="#fn:140"><sup>140</sup></a> Some southern populations (in the <a href="/facts/Yucat%25C3%25A1n_Peninsula/xGAcABhC">Yucatán Peninsula</a>) of <i>L. polyphemus</i> are somewhat smaller, but otherwise, this species is larger.<a class="footnote-ref" id="fnref:141" href="#fn:141"><sup>141</sup></a> In the largest species, <i>T. tridentatus</i>, females can reach as much as 79.5 cm (31+1⁄4 in) long, including their telson, and up to 4 kg (9 lb) in weight.<a class="footnote-ref" id="fnref:142" href="#fn:142"><sup>142</sup></a> This is only about 10–20 cm (4–8 in) longer than the largest females of <i>L. polyphemus</i> and <i>T. gigas</i>, but roughly twice the weight.<a class="footnote-ref" id="fnref:143" href="#fn:143"><sup>143</sup></a><a class="footnote-ref" id="fnref:144" href="#fn:144"><sup>144</sup></a> </p> <h3>Reproduction</h3> <p>During the breeding season (spring and summer in the <a href="/facts/Northeastern_United_States/Xa8zQlkM">Northeast US</a>, year-round in warmer locations) horseshoe crabs migrate to shallow coastal waters.<a class="footnote-ref" id="fnref:145" href="#fn:145"><sup>145</sup></a> Nesting typically happens at <a href="/facts/High_tide/zNstvWPv">high tides</a> around <a href="/facts/Full_moon/NRMWFPh2">full</a> or <a href="/facts/New_moon/uab6r7yY">new moons</a>.<a class="footnote-ref" id="fnref:146" href="#fn:146"><sup>146</sup></a> When nesting, they spawn on beaches and <a href="/facts/Salt_marsh/yV4Afzoj">salt marshes</a>.<a class="footnote-ref" id="fnref:147" href="#fn:147"><sup>147</sup></a> </p><p>When mating, the smaller male clings to the back or <a href="/facts/Opisthosoma/rXmmsVrX">opisthosoma</a> of the larger female using specialized <a href="/facts/Pedipalp/mdd5FmrQ">pedipalps</a>.<a class="footnote-ref" id="fnref:148" href="#fn:148"><sup>148</sup></a> This typically leaves scars, allowing younger females to be easily identified.<a class="footnote-ref" id="fnref:149" href="#fn:149"><sup>149</sup></a> In the meantime, the female digs a hole in the <a href="/facts/Sediment/zsIH1A6U">sediment</a> and lays between 2,000 and 30,000 large <a href="/facts/Egg/2a1McdtR">eggs</a>.<a class="footnote-ref" id="fnref:150" href="#fn:150"><sup>150</sup></a>: 559 Unusual for <a href="/facts/Arthropod/JKJLTFzp">arthropods</a>, fertilization is done externally.<a class="footnote-ref" id="fnref:151" href="#fn:151"><sup>151</sup></a>: 559 In most species, procreation is done by both the main and additional "satellite males".<a class="footnote-ref" id="fnref:152" href="#fn:152"><sup>152</sup></a> Satellite males surround the main pair and may have some success fertilizing eggs.<a class="footnote-ref" id="fnref:153" href="#fn:153"><sup>153</sup></a> In <i><a href="/facts/Limulus/QT4e4wkd">L. polyphemus</a></i>, the eggs take about two weeks to hatch with shore birds eating many of them in the process.<a class="footnote-ref" id="fnref:154" href="#fn:154"><sup>154</sup></a> </p><p>Natural breeding of horseshoe crabs in captivity has proven to be difficult.<a class="footnote-ref" id="fnref:155" href="#fn:155"><sup>155</sup></a> Some evidence indicates that mating takes place only in the presence of the <a href="/facts/Sand/MdTIt0M8">sand</a> or <a href="/facts/Mud/F6nLmX47">mud</a> in which horseshoe crab <a href="/facts/Egg/2a1McdtR">eggs</a> have previously hatched.<a class="footnote-ref" id="fnref:156" href="#fn:156"><sup>156</sup></a> However, it is not known with certainty what the animals sense in the sand, how they sense it, or why they mate only in its presence.<a class="footnote-ref" id="fnref:157" href="#fn:157"><sup>157</sup></a> In contrast, <a href="/facts/Artificial_insemination/ccbKoyu4">artificial insemination</a> and induced spawning have been done since the 1980s.<a class="footnote-ref" id="fnref:158" href="#fn:158"><sup>158</sup></a> Additionally, <a href="/facts/Egg/2a1McdtR">eggs</a> and juveniles collected from the wild can easily be raised to adulthood in a captive environment.<a class="footnote-ref" id="fnref:159" href="#fn:159"><sup>159</sup></a><a class="footnote-ref" id="fnref:160" href="#fn:160"><sup>160</sup></a> </p> <h2 id="relationship-with-humans">Relationship with humans</h2> <h3>Consumption</h3> <p>Though they have little meat, horseshoe crabs are valued as a delicacy in some parts of <a href="/facts/East_Asia/D8yGVCQX">East</a> and <a href="/facts/Southeast_Asia/VafwT517">Southeast Asia</a>.<a class="footnote-ref" id="fnref:161" href="#fn:161"><sup>161</sup></a> The meat is white, has a rubbery texture similar to that of <a href="/facts/Lobster/c5eYu72w">lobsters</a>, and possesses a slightly salty aftertaste.<a class="footnote-ref" id="fnref:162" href="#fn:162"><sup>162</sup></a> Horseshoe crab can be eaten both raw and <a href="/facts/Cooking/YWVfGWD1">cooked</a>, but must be properly prepared to prevent <a href="/facts/Food_poisioning/9lxqlJqg">food poisoning</a>.<a class="footnote-ref" id="fnref:163" href="#fn:163"><sup>163</sup></a> Furthermore, only certain species can be eaten. There have been numerous reports of poisonings after consuming <a href="/facts/Mangrove_horseshoe_crab/XwycKvzE">mangrove horseshoe crabs</a> (<i>Carcinoscorpius rotundicauda</i>) as its meat contains <a href="/facts/Tetrodotoxin/hsEJAUwA">tetrodotoxin</a>.<a class="footnote-ref" id="fnref:164" href="#fn:164"><sup>164</sup></a> </p><p>While horseshoe crab meat is commonly prepared by <a href="/facts/Grilling/mVsgTQpL">grilling</a> or <a href="/facts/Stew/egswh6LU">stewing</a>, it can also be <a href="/facts/Pickling/lKvv4uJA">pickled</a> in vinegar or <a href="/facts/Stir_frying/hkdPVhI1">stir-fried</a> with <a href="/facts/Vegetable/j3AlDG64">vegetables</a>.<a class="footnote-ref" id="fnref:165" href="#fn:165"><sup>165</sup></a> Many recipes involve the use of various <a href="/facts/Spice/mIMfxvm7">spices</a>, <a href="/facts/Herb/EKCltNNF">herbs</a>, and <a href="/facts/Chili_pepper/DuuJkMdR">chilies</a> to give the dish more flavor.<a class="footnote-ref" id="fnref:166" href="#fn:166"><sup>166</sup></a> </p><p>In addition to their <a href="/facts/Meat/DUHTTM1d">meat</a>, horseshoe crabs are valued for their <a href="/facts/Egg/2a1McdtR">eggs</a>.<a class="footnote-ref" id="fnref:167" href="#fn:167"><sup>167</sup></a> Much like the meat, only the eggs of specific species can be eaten. The eggs of <a href="/facts/Mangrove_horseshoe_crab/XwycKvzE">mangrove horseshoe crabs</a> contain <a href="/facts/Tetrodotoxin/hsEJAUwA">tetrodotoxin</a> and will result in <a href="/facts/Food_poisioning/9lxqlJqg">food poisoning</a> if consumed.<a class="footnote-ref" id="fnref:168" href="#fn:168"><sup>168</sup></a> </p> <h3>Use in fisheries</h3> <p>In the <a href="/facts/United_States/P0sCdLe5">United States</a>, horseshoe crabs are used as bait to fish for <a href="/facts/Eel/B8DMEUpu">eels</a>, <a href="/facts/Whelk/zeyfvQ1X">whelk</a>, or <a href="/facts/Conch/Ie4rhJQx">conch</a>.<a class="footnote-ref" id="fnref:169" href="#fn:169"><sup>169</sup></a> Nearly 1 million crabs are harvested yearly for bait in the United States, dwarfing the biomedical mortality.<a class="footnote-ref" id="fnref:170" href="#fn:170"><sup>170</sup></a> However, fishing with horseshoe crab was banned indefinitely in <a href="/facts/New_Jersey/pI5k19S7">New Jersey</a> in 2008 with a moratorium on harvesting to protect the <a href="/facts/Red_knot/R94H8Yn7">red knot</a>, a shorebird that eats the crabs' eggs.<a class="footnote-ref" id="fnref:171" href="#fn:171"><sup>171</sup></a> A ban on catching female crabs was put in place in <a href="/facts/Delaware/4n4I3Rhu">Delaware</a>, and a permanent moratorium is in effect in <a href="/facts/South_Carolina/lQQX84IS">South Carolina</a>.<a class="footnote-ref" id="fnref:172" href="#fn:172"><sup>172</sup></a><a class="footnote-ref" id="fnref:173" href="#fn:173"><sup>173</sup></a> </p> <h3>Use in medicine</h3> <p>The blood of a horseshoe crab contains cells known as <a href="/facts/Amebocyte/RVIH4NoI">amebocytes</a>.<a class="footnote-ref" id="fnref:174" href="#fn:174"><sup>174</sup></a> These play a similar role to the <a href="/facts/White_blood_cell/vsDunUK0">white blood cells</a> of <a href="/facts/Vertebrate/tT54FSTT">vertebrates</a> in defending the organism against <a href="/facts/Pathogen/axMXtV1M">pathogens</a>.<a class="footnote-ref" id="fnref:175" href="#fn:175"><sup>175</sup></a> Amebocytes from the <a href="/facts/Blood/03zEulkj">blood</a> of <a href="/facts/Limulus/QT4e4wkd"><i>Limulus polyphemus</i></a> are used to make <a href="/facts/Limulus_amebocyte_lysate/M5BmAkYR">Limulus amebocyte lysate</a> (LAL), which is used for the detection of <a href="/facts/Bacteria/wC8xSCsU">bacterial</a> endotoxins in medical applications.<a class="footnote-ref" id="fnref:176" href="#fn:176"><sup>176</sup></a> There is a high demand for blood, the harvest of which involves collecting the animals, bleeding them, and then releasing them back into the sea.<a class="footnote-ref" id="fnref:177" href="#fn:177"><sup>177</sup></a> Most of the animals survive the process; mortality is correlated with both the amount of blood extracted from an individual animal and the stress experienced during handling and transportation.<a class="footnote-ref" id="fnref:178" href="#fn:178"><sup>178</sup></a> Estimates of mortality rates following blood harvesting vary from 3–15%<a class="footnote-ref" id="fnref:179" href="#fn:179"><sup>179</sup></a><a class="footnote-ref" id="fnref:180" href="#fn:180"><sup>180</sup></a> to 10–30%.<a class="footnote-ref" id="fnref:181" href="#fn:181"><sup>181</sup></a><a class="footnote-ref" id="fnref:182" href="#fn:182"><sup>182</sup></a><a class="footnote-ref" id="fnref:183" href="#fn:183"><sup>183</sup></a> Approximately 500,000 <i>Limulus</i> are harvested annually for this purpose.<a class="footnote-ref" id="fnref:184" href="#fn:184"><sup>184</sup></a> According to the biomedical industry, up to 30% of an individual's blood is removed. <a href="/facts/NPR/BohIW9Xg">NPR</a> disagrees with this claim, reporting that it "can deplete them of more than half their volume of blue blood".<a class="footnote-ref" id="fnref:185" href="#fn:185"><sup>185</sup></a> Bleeding may prevent female horseshoe crabs from being able to <a href="/facts/Spawn_(biology)/nYF12vfX">spawn</a> or may decrease the number of eggs they can lay.<a class="footnote-ref" id="fnref:186" href="#fn:186"><sup>186</sup></a> It has been found that harvesting blood from horseshoe crabs drastically impacts their percent daily activity, decreasing their overall movement.<a class="footnote-ref" id="fnref:187" href="#fn:187"><sup>187</sup></a> </p><p>The horseshoe crabs spend between one and three days away from the ocean before being returned.<a class="footnote-ref" id="fnref:188" href="#fn:188"><sup>188</sup></a> As long as the gills stay moist, they can survive on land for four days.<a class="footnote-ref" id="fnref:189" href="#fn:189"><sup>189</sup></a> Some scientists are skeptical that certain companies return their horseshoe crabs to the ocean at all, instead suspecting them of selling the horseshoe crabs as <a href="/facts/Fishing_bait/u82Xyvhh">fishing bait</a>.<a class="footnote-ref" id="fnref:190" href="#fn:190"><sup>190</sup></a> </p><p>The harvesting of horseshoe crab blood in the pharmaceutical industry is in decline.<a class="footnote-ref" id="fnref:191" href="#fn:191"><sup>191</sup></a> In 1986, <a href="/facts/Kyushu_University/duWa5tYG">Kyushu University</a> researchers discovered that the same test could be achieved by using isolated <a href="/facts/Limulus_clotting_factor_C/p94cHG4J">Limulus clotting factor C</a> (rFC), an enzyme found in LAL, as by using LAL itself.<a class="footnote-ref" id="fnref:192" href="#fn:192"><sup>192</sup></a> Jeak Ling Ding, a <a href="/facts/National_University_of_Singapore/vP3kw0ye">National University of Singapore</a> researcher, patented a process for manufacturing rFC; on 8 May 2003, synthetic isolated rFC made via her patented process became available for the first time.<a class="footnote-ref" id="fnref:193" href="#fn:193"><sup>193</sup></a> Industry at first took little interest in the new product, however, as it was patent-encumbered, not yet approved by regulators, and sold by a single manufacturer, <a href="/facts/Lonza_Group/qJ66ENDW">Lonza Group</a>.<a class="footnote-ref" id="fnref:194" href="#fn:194"><sup>194</sup></a> In 2013, however, Hyglos GmbH also began manufacturing its own rFC product.<a class="footnote-ref" id="fnref:195" href="#fn:195"><sup>195</sup></a> This, combined with the acceptance of rFC by European regulators, the comparable cost between LAL and rFC, and support from <a href="/facts/Eli_Lilly_and_Company/e5Pw7RmR">Eli Lilly and Company</a>, which committed to using rFC in lieu of LAL,<a class="footnote-ref" id="fnref:196" href="#fn:196"><sup>196</sup></a> is projected to all but end the practice of blood harvesting from horseshoe crabs.<a class="footnote-ref" id="fnref:197" href="#fn:197"><sup>197</sup></a> </p><p><a href="/facts/History_of_COVID-19_vaccine_development/U5zkc12k">Vaccine research and development</a> during the <a href="/facts/COVID-19_pandemic/0xTsh7Ut">COVID-19 pandemic</a><a class="footnote-ref" id="fnref:198" href="#fn:198"><sup>198</sup></a> has added an additional "strain on the American horseshoe crab."<a class="footnote-ref" id="fnref:199" href="#fn:199"><sup>199</sup></a><a class="footnote-ref" id="fnref:200" href="#fn:200"><sup>200</sup></a> In December 2019, a report of the <a href="/facts/US_Senate/VyzXHE01">US Senate</a> which encouraged the <a href="/facts/Food_and_Drug_Administration/rCEnh9WB">Food and Drug Administration</a> to "establish processes for evaluating alternative pyrogenicity tests and report back [to the Senate] on steps taken to increase their use" was released;<a class="footnote-ref" id="fnref:201" href="#fn:201"><sup>201</sup></a> <a href="/facts/People_for_the_Ethical_Treatment_of_Animals/2JMRqsKM">PETA</a> backed the report.<a class="footnote-ref" id="fnref:202" href="#fn:202"><sup>202</sup></a> </p><p>In June 2020, it was reported that <a href="/facts/U.S._Pharmacopeia/CyYDYG8m">U.S. Pharmacopeia</a> had declined to give rFC equal standing with horseshoe crab blood.<a class="footnote-ref" id="fnref:203" href="#fn:203"><sup>203</sup></a> Without the approval for the classification as an industry standard testing material, U.S. companies will have to overcome the scrutiny of showing that rFC is safe and effective for their desired uses, which may serve as a deterrent for usage of the horseshoe crab blood substitute.<a class="footnote-ref" id="fnref:204" href="#fn:204"><sup>204</sup></a> </p> <h2 id="conservation-status">Conservation status</h2> <p>Development along shorelines is dangerous to horseshoe crab <a href="/facts/Spawn_(biology)/nYF12vfX">spawning</a>, limiting available space and degrading habitat. <a href="/facts/Bulkhead_(barrier)/Mc1RPlpP">Bulkheads</a> can block access to intertidal spawning regions as well.<a class="footnote-ref" id="fnref:205" href="#fn:205"><sup>205</sup></a> </p><p>The population of <a href="/facts/Tachypleus_gigas/24wTm3oJ">Indo-Pacific horseshoe crabs</a> (<i>Tachypleus gigas</i>) in <a href="/facts/Malaysia/8zbUMzCP">Malaysia</a> and <a href="/facts/Indonesia/vQnWU3IW">Indonesia</a> has decreased dramatically since 2010. This is primarily due to overharvesting, as horseshoe crabs are considered a delicacy in countries like <a href="/facts/Thailand/GCUnN4JK">Thailand</a>. The individuals most likely to be targeted are <a href="/facts/Gravidity_and_parity/NU0Vs5uT">gravid</a> females, as they can be sold for both their <a href="/facts/Meat/DUHTTM1d">meat</a> and <a href="/facts/Egg/2a1McdtR">eggs</a>. This method of harvesting has led to an unbalanced sex ratio in the wild, something that also contributes to the area's declining population.<a class="footnote-ref" id="fnref:206" href="#fn:206"><sup>206</sup></a> </p><p>Because of habitat destruction for shoreline development, use in fishing, <a href="/facts/Plastic_pollution/oLNNHQrG">plastic pollution</a>, status as a culinary delicacy, and use in research and medicine, the horseshoe crab faces both <a href="/facts/Endangered_species/L7cIweSW">endangered</a> and <a href="/facts/Extinction/24p5NP2q">extinct</a> statuses. One species, the <a href="/facts/Tachypleus_tridentatus/BkvjmNDK">tri-spine horseshoe crab</a> (<i>Tachypleus tridentatus</i>), has already been declared locally extinct in <a href="/facts/Taiwan/VcJoUD8w">Taiwan</a>. Facing a greater than 90% decrease in <i>T. tridentatus</i> juveniles, it is suspected that <a href="/facts/Hong_Kong/4nAf3mqQ">Hong Kong</a> will be the next to declare tri-spine horseshoe crabs as extinct from the area. This species is listed as endangered on the <a href="/facts/IUCN_Red_List/8gemqCLu">IUCN Red List</a>, specifically because of the <a href="/facts/Overexploitation/35n60afL">overexploitation</a> and loss of critical habitat.<a class="footnote-ref" id="fnref:207" href="#fn:207"><sup>207</sup></a> </p><p>To preserve and ensure the continuous supply of horseshoe crabs, a breeding center was built in <a href="/facts/Johor/Rp1x21cf">Johor</a>, <a href="/facts/Malaysia/8zbUMzCP">Malaysia</a> where animals are bred and released back into the ocean in the thousands once every two years.<a class="footnote-ref" id="fnref:208" href="#fn:208"><sup>208</sup></a> It is estimated to take around 12 years before they are suitable for consumption.<a class="footnote-ref" id="fnref:209" href="#fn:209"><sup>209</sup></a> </p><p>A low horseshoe crab population in <a href="/facts/Delaware_Bay/mbQIQruo">Delaware Bay</a> is hypothesized to endanger the future of the <a href="/facts/Red_knot/R94H8Yn7">red knot</a>. Red knots, long-distance <a href="/facts/Migration_(ecology)/J3LuRgjq">migratory</a> shorebirds, feed on the protein-rich eggs during their stopovers on the beaches of New Jersey and Delaware.<a class="footnote-ref" id="fnref:210" href="#fn:210"><sup>210</sup></a> An effort is ongoing to develop adaptive-management plans to regulate horseshoe crab harvests in the bay in a way that protects migrating shorebirds.<a class="footnote-ref" id="fnref:211" href="#fn:211"><sup>211</sup></a> In 2023, the <a href="/facts/United_States_Fish_and_Wildlife_Service/kNLNl93B">US Fish and Wildlife Service</a> halted the harvesting of horseshoe crabs in the <a href="/facts/Cape_Romain_National_Wildlife_Refuge/fEDD8qmG">Cape Romain National Wildlife Refuge</a>, <a href="/facts/South_Carolina/lQQX84IS">South Carolina</a>, from March 15 to July 15 to aid their reproduction.<a class="footnote-ref" id="fnref:212" href="#fn:212"><sup>212</sup></a> This decision was influenced by the importance of horseshoe crab eggs as a food source for <a href="/facts/Migratory_bird/GvraPhgn">migratory birds</a>, the ongoing use of horseshoe crabs for bait, and the use of their <a href="/facts/Blood/03zEulkj">blood</a> in medical products.<a class="footnote-ref" id="fnref:213" href="#fn:213"><sup>213</sup></a> The ban supports the conservation goals of the refuge, spanning 66,000 acres (26,700 hectares) of marshes, beaches, and islands near Charleston.<a class="footnote-ref" id="fnref:214" href="#fn:214"><sup>214</sup></a> </p> <h3>Citations</h3> <h2 id="further-reading">Further reading</h2> <ul> <li>Arthropods portal</li></ul> <ul><li> <a href="/facts/Hugh_Chisholm/2vWblUBe">Chisholm H</a>, ed. (1911). "King-Crab". <i><a href="/facts/Encyclop%25C3%25A6dia_Britannica_Eleventh_Edition/mPElbCRY">Encyclopædia Britannica</a></i> (11th ed.). Cambridge University Press.</li></ul> <h2 id="external-links">External links</h2> <ul><li><a href="https://www.nytimes.com/2023/02/16/opinion/drug-safety-horsehoe-crab.html">When the Horseshoe Crabs Are Gone, We'll Be in Trouble. New York Times 2023</a></li> <li><a href="http://www.acciusa.com/bet/update/index.html">LAL Update</a></li> <li><a href="https://web.archive.org/web/20100721002111/http://www.sciencefriday.com/program/archives/201007164">Science Friday Video: horseshoe crab season</a></li> <li><a href="http://ocean.si.edu/blog/flu-season-thank-horseshoe-crab">Horseshoe crab at the Smithsonian Ocean Portal</a></li> <li><a href="http://www.horseshoecrab.org/med/med.html">The Horseshoe Crab – Medical Uses; The Ecological Research & Development Group (ERDG)</a></li> <li><a href="http://redknot.org/">RedKnot.org</a> <a href="https://web.archive.org/web/20140415233855/http://www.redknot.org/">Archived</a> 2014-04-15 at the <a href="/facts/Wayback_Machine/nmQ3a6JC">Wayback Machine</a> links to shorebird recovery sites, movies, events & other info on Red Knot rufa & horseshoe crabs.</li> <li><a href="http://thefreaky.net/freaky-and-weird/crab-bleeders/">Crab Bleeders</a> Article about the men who bleed horseshoe crabs for science.</li> <li><a href="http://naturedocumentaries.org/96/horseshoe-crabs-mating-Maine/">Day time mating of horseshoe crabs in Maine</a></li> <li><a href="https://www.theatlantic.com/science/archive/2018/05/blood-in-the-water/559229/">Sarah Zhang, The Last Days of the Blue-Blood Harvest, The Atlantic, May 9, 2018</a></li></ul> <h2 id="references">References</h2> <ol> <li id="fn:1"><p>David M. Rudkin, Graham A. Young & Godfrey S. Nowlan (2008). "The oldest horseshoe crab: a new xiphosurid from Late Ordovician Konservat-Lagerstätten deposits, Manitoba, Canada". Palaeontology. 51 (1): 1–9. Bibcode:2008Palgy..51....1R. doi:10.1111/j.1475-4983.2007.00746.x. <a href="https://doi.org/10.1111%2Fj.1475-4983.2007.00746.x" target="_blank">https://doi.org/10.1111%2Fj.1475-4983.2007.00746.x</a> <a href="#fnref:1" class="footnote-back-ref">↩</a></p></li> <li id="fn:2"><p>Lamsdell, James C.; McKenzie, Scott C. (1 August 2015). "Tachypleus syriacus (Woodward)—a sexually dimorphic Cretaceous crown limulid reveals underestimated horseshoe crab divergence times". Organisms Diversity & Evolution. 15 (4): 681–693. Bibcode:2015ODivE..15..681L. doi:10.1007/s13127-015-0229-3. S2CID 15196244. Archived from the original on 30 October 2022. Retrieved 2 January 2023. <a href="https://link.springer.com/article/10.1007/s13127-015-0229-3" target="_blank">https://link.springer.com/article/10.1007/s13127-015-0229-3</a> <a href="#fnref:2" class="footnote-back-ref">↩</a></p></li> <li id="fn:3"><p>Kin, Adrian; Błażejowski, Błażej (2 October 2014). "The Horseshoe Crab of the Genus Limulus: Living Fossil or Stabilomorph?". PLOS ONE. 9 (10): e108036. Bibcode:2014PLoSO...9j8036K. doi:10.1371/journal.pone.0108036. ISSN 1932-6203. PMC 4183490. PMID 25275563. <a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4183490" target="_blank">https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4183490</a> <a href="#fnref:3" class="footnote-back-ref">↩</a></p></li> <li id="fn:4"><p>Garwood RJ, Dunlop J (13 November 2014). "Three-dimensional reconstruction and the phylogeny of extinct chelicerate orders". PeerJ. 2: e641. doi:10.7717/peerj.641. PMC 4232842. PMID 25405073. <a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4232842" target="_blank">https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4232842</a> <a href="#fnref:4" class="footnote-back-ref">↩</a></p></li> <li id="fn:5"><p>Garwood RJ, Dunlop J (13 November 2014). "Three-dimensional reconstruction and the phylogeny of extinct chelicerate orders". PeerJ. 2: e641. doi:10.7717/peerj.641. PMC 4232842. PMID 25405073. <a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4232842" target="_blank">https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4232842</a> <a href="#fnref:5" class="footnote-back-ref">↩</a></p></li> <li id="fn:6"><p>Garwood RJ, Dunlop JA, Knecht BJ, Hegna TA (April 2017). "The phylogeny of fossil whip spiders". BMC Evolutionary Biology. 17 (1): 105. Bibcode:2017BMCEE..17..105G. doi:10.1186/s12862-017-0931-1. PMC 5399839. PMID 28431496. <a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5399839" target="_blank">https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5399839</a> <a href="#fnref:6" class="footnote-back-ref">↩</a></p></li> <li id="fn:7"><p>Lamsdell, James C. (4 December 2020). "The phylogeny and systematics of Xiphosura". PeerJ. 8: e10431. doi:10.7717/peerj.10431. ISSN 2167-8359. PMC 7720731. PMID 33335810. <a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7720731" target="_blank">https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7720731</a> <a href="#fnref:7" class="footnote-back-ref">↩</a></p></li> <li id="fn:8"><p>Kin, Adrian; Błażejowski, Błażej (2 October 2014). "The Horseshoe Crab of the Genus Limulus: Living Fossil or Stabilomorph?". PLOS ONE. 9 (10): e108036. Bibcode:2014PLoSO...9j8036K. doi:10.1371/journal.pone.0108036. ISSN 1932-6203. PMC 4183490. PMID 25275563. <a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4183490" target="_blank">https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4183490</a> <a href="#fnref:8" class="footnote-back-ref">↩</a></p></li> <li id="fn:9"><p>Nong, Wenyan; Qu, Zhe; Li, Yiqian; Barton-Owen, Tom; Wong, Annette Y. P.; Yip, Ho Yin; Lee, Hoi Ting; Narayana, Satya; Baril, Tobias; Swale, Thomas; Cao, Jianquan; Chan, Ting Fung; Kwan, Hoi Shan; Ngai, Sai Ming; Panagiotou, Gianni; Qian, Pei-Yuan; Qiu, Jian-Wen; Yip, Kevin Y.; Ismail, Noraznawati; Pati, Siddhartha; John, Akbar; Tobe, Stephen S.; Bendena, William G.; Cheung, Siu Gin; Hayward, Alexander; Hui, Jerome H. L. (2021). "Horseshoe crab genomes reveal the evolution of genes and microRNAs after three rounds of whole genome duplication". Communications Biology. 4 (1): 83. doi:10.1038/s42003-020-01637-2. PMC 7815833. PMID 33469163. <a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7815833" target="_blank">https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7815833</a> <a href="#fnref:9" class="footnote-back-ref">↩</a></p></li> <li id="fn:10"><p>Sekiguchi K (1988). Biology of Horseshoe Crabs. Science House. ISBN 978-4-915572-25-8. <a href="978-4-915572-25-8" target="_blank">978-4-915572-25-8</a> <a href="#fnref:10" class="footnote-back-ref">↩</a></p></li> <li id="fn:11"><p>Vestbo, Stine; Obst, Matthias; Quevedo Fernandez, Francisco J.; Intanai, Itsara; Funch, Peter (May 2018). "Present and Potential Future Distributions of Asian Horseshoe Crabs Determine Areas for Conservation". Frontiers in Marine Science. 5 (164): 1–16. doi:10.3389/fmars.2018.00164. <a href="https://doi.org/10.3389%2Ffmars.2018.00164" target="_blank">https://doi.org/10.3389%2Ffmars.2018.00164</a> <a href="#fnref:11" class="footnote-back-ref">↩</a></p></li> <li id="fn:12"><p>Bicknell RD, Błażejowski B, Wings O, Hitij T, Botton ML (March 2021). Zhang XG (ed.). "Critical re-evaluation of Limulidae uncovers limited Limulus diversity". Papers in Palaeontology. 7 (3): 1525–1556. Bibcode:2021PPal....7.1525B. doi:10.1002/spp2.1352. S2CID 233783546. <a href="/wiki/Bibcode_(identifier)" target="_blank">/wiki/Bibcode_(identifier)</a> <a href="#fnref:12" class="footnote-back-ref">↩</a></p></li> <li id="fn:13"><p>Lamsdell JC (4 December 2020). "The phylogeny and systematics of Xiphosura". PeerJ. 8: e10431. doi:10.7717/peerj.10431. PMC 7720731. PMID 33335810. <a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7720731" target="_blank">https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7720731</a> <a href="#fnref:13" class="footnote-back-ref">↩</a></p></li> <li id="fn:14"><p>Bicknell RD, Pates S (November 2019). "Xiphosurid from the Tournaisian (Carboniferous) of Scotland confirms deep origin of Limuloidea". Scientific Reports. 9 (1): 17102. Bibcode:2019NatSR...917102B. doi:10.1038/s41598-019-53442-5. PMC 6863854. PMID 31745138. <a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6863854" target="_blank">https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6863854</a> <a href="#fnref:14" class="footnote-back-ref">↩</a></p></li> <li id="fn:15"><p>Lamsdell JC (4 December 2020). "The phylogeny and systematics of Xiphosura". PeerJ. 8: e10431. doi:10.7717/peerj.10431. PMC 7720731. PMID 33335810. <a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7720731" target="_blank">https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7720731</a> <a href="#fnref:15" class="footnote-back-ref">↩</a></p></li> <li id="fn:16"><p>Lamsdell JC, Teruzzi G, Pasini G, Garassino A (29 April 2021). "A new limulid (Chelicerata, Xiphosurida) from the Lower Jurassic (Sinemurian) of Osteno, NW Italy". Neues Jahrbuch für Geologie und Paläontologie - Abhandlungen. 300 (1): 1–10. doi:10.1127/njgpa/2021/0974. ISSN 0077-7749. S2CID 234814276. Archived from the original on 28 June 2021. Retrieved 24 June 2021. <a href="http://www.schweizerbart.de/papers/njgpa/detail/300/98376/A_new_limulid_Chelicerata_Xiphosurida_from_the_Low?af=crossref" target="_blank">http://www.schweizerbart.de/papers/njgpa/detail/300/98376/A_new_limulid_Chelicerata_Xiphosurida_from_the_Low?af=crossref</a> <a href="#fnref:16" class="footnote-back-ref">↩</a></p></li> <li id="fn:17"><p>Lamsdell JC (4 December 2020). "The phylogeny and systematics of Xiphosura". PeerJ. 8: e10431. doi:10.7717/peerj.10431. PMC 7720731. PMID 33335810. <a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7720731" target="_blank">https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7720731</a> <a href="#fnref:17" class="footnote-back-ref">↩</a></p></li> <li id="fn:18"><p>Briggs, Derek E. G.; Siveter, Derek J.; Siveter, David J.; Sutton, Mark D.; Garwood, Russell J.; Legg, David (25 September 2012). "Silurian horseshoe crab illuminates the evolution of arthropod limbs". Proceedings of the National Academy of Sciences of the United States of America. 109 (39): 15702–15705. Bibcode:2012PNAS..10915702B. doi:10.1073/pnas.1205875109. ISSN 0027-8424. PMC 3465403. PMID 22967511. <a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3465403" target="_blank">https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3465403</a> <a href="#fnref:18" class="footnote-back-ref">↩</a></p></li> <li id="fn:19"><p>Lamsdell, James C. (18 January 2013). "Revised systematics of Palaeozoic 'horseshoe crabs' and the myth of monophyletic Xiphosura". Zoological Journal of the Linnean Society. 167 (1): 1–27. doi:10.1111/j.1096-3642.2012.00874.x – via Oxford Academic. <a href="https://academic.oup.com/zoolinnean/article/167/1/1/2420794" target="_blank">https://academic.oup.com/zoolinnean/article/167/1/1/2420794</a> <a href="#fnref:19" class="footnote-back-ref">↩</a></p></li> <li id="fn:20"><p>Legg, David A.; Sutton, Mark D.; Edgecombe, Gregory D. (30 September 2013). "Arthropod fossil data increase congruence of morphological and molecular phylogenies". Nature Communications. 4 (1): 2485. Bibcode:2013NatCo...4.2485L. doi:10.1038/ncomms3485. ISSN 2041-1723. PMID 24077329 – via Research Gate. <a href="https://www.researchgate.net/publication/257205419" target="_blank">https://www.researchgate.net/publication/257205419</a> <a href="#fnref:20" class="footnote-back-ref">↩</a></p></li> <li id="fn:21"><p>Garwood RJ, Dunlop J (13 November 2014). "Three-dimensional reconstruction and the phylogeny of extinct chelicerate orders". PeerJ. 2: e641. doi:10.7717/peerj.641. PMC 4232842. PMID 25405073. <a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4232842" target="_blank">https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4232842</a> <a href="#fnref:21" class="footnote-back-ref">↩</a></p></li> <li id="fn:22"><p>Garwood RJ, Dunlop JA, Knecht BJ, Hegna TA (April 2017). "The phylogeny of fossil whip spiders". BMC Evolutionary Biology. 17 (1): 105. Bibcode:2017BMCEE..17..105G. doi:10.1186/s12862-017-0931-1. PMC 5399839. PMID 28431496. <a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5399839" target="_blank">https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5399839</a> <a href="#fnref:22" class="footnote-back-ref">↩</a></p></li> <li id="fn:23"><p>Ballesteros, Jesús A; Sharma, Prashant P (27 March 2019). "A Critical Appraisal of the Placement of Xiphosura (Chelicerata) with Account of Known Sources of Phylogenetic Error". Systematic Biology. 68 (6): 896–917. doi:10.1093/sysbio/syz011. ISSN 1063-5157. PMID 30917194. <a href="https://doi.org/10.1093%2Fsysbio%2Fsyz011" target="_blank">https://doi.org/10.1093%2Fsysbio%2Fsyz011</a> <a href="#fnref:23" class="footnote-back-ref">↩</a></p></li> <li id="fn:24"><p>Lozano-Fernandez, Jesus; Tanner, Alastair R.; Giacomelli, Mattia; Carton, Robert; Vinther, Jakob; Edgecombe, Gregory D.; Pisani, Davide (24 May 2019). "Increasing species sampling in chelicerate genomic-scale datasets provides support for monophyly of Acari and Arachnida". Nature Communications. 10 (1): 2295. Bibcode:2019NatCo..10.2295L. doi:10.1038/s41467-019-10244-7. ISSN 2041-1723. PMC 6534568. PMID 31127117. <a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6534568" target="_blank">https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6534568</a> <a href="#fnref:24" class="footnote-back-ref">↩</a></p></li> <li id="fn:25"><p>Lamsdell JC (4 December 2020). "The phylogeny and systematics of Xiphosura". PeerJ. 8: e10431. doi:10.7717/peerj.10431. PMC 7720731. PMID 33335810. <a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7720731" target="_blank">https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7720731</a> <a href="#fnref:25" class="footnote-back-ref">↩</a></p></li> <li id="fn:26"><p>Shingate, Prashant; Ravi, Vydianathan; Prasad, Aravind; Tay, Boon-Hui; Garg, Kritika M.; Chattopadhyay, Balaji; Yap, Laura-Marie; Rheindt, Frank E.; Venkatesh, Byrappa (8 May 2020). "Chromosome-level assembly of the horseshoe crab genome provides insights into its genome evolution". Nature Communications. 11 (1): 2322. Bibcode:2020NatCo..11.2322S. doi:10.1038/s41467-020-16180-1. ISSN 2041-1723. PMC 7210998. PMID 32385269. <a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7210998" target="_blank">https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7210998</a> <a href="#fnref:26" class="footnote-back-ref">↩</a></p></li> <li id="fn:27"><p>Nong, Wenyan; Qu, Zhe; Li, Yiqian; Barton-Owen, Tom; Wong, Annette Y. P.; Yip, Ho Yin; Lee, Hoi Ting; Narayana, Satya; Baril, Tobias; Swale, Thomas; Cao, Jianquan; Chan, Ting Fung; Kwan, Hoi Shan; Ngai, Sai Ming; Panagiotou, Gianni (19 January 2021). "Horseshoe crab genomes reveal the evolution of genes and microRNAs after three rounds of whole genome duplication". Communications Biology. 4 (1): 83. doi:10.1038/s42003-020-01637-2. ISSN 2399-3642. PMC 7815833. PMID 33469163. <a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7815833" target="_blank">https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7815833</a> <a href="#fnref:27" class="footnote-back-ref">↩</a></p></li> <li id="fn:28"><p>Nong, Wenyan; Qu, Zhe; Li, Yiqian; Barton-Owen, Tom; Wong, Annette Y. P.; Yip, Ho Yin; Lee, Hoi Ting; Narayana, Satya; Baril, Tobias; Swale, Thomas; Cao, Jianquan; Chan, Ting Fung; Kwan, Hoi Shan; Ngai, Sai Ming; Panagiotou, Gianni (19 January 2021). "Horseshoe crab genomes reveal the evolution of genes and microRNAs after three rounds of whole genome duplication". Communications Biology. 4 (1): 83. doi:10.1038/s42003-020-01637-2. ISSN 2399-3642. PMC 7815833. PMID 33469163. <a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7815833" target="_blank">https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7815833</a> <a href="#fnref:28" class="footnote-back-ref">↩</a></p></li> <li id="fn:29"><p>Nong, Wenyan; Qu, Zhe; Li, Yiqian; Barton-Owen, Tom; Wong, Annette Y. P.; Yip, Ho Yin; Lee, Hoi Ting; Narayana, Satya; Baril, Tobias; Swale, Thomas; Cao, Jianquan; Chan, Ting Fung; Kwan, Hoi Shan; Ngai, Sai Ming; Panagiotou, Gianni (19 January 2021). "Horseshoe crab genomes reveal the evolution of genes and microRNAs after three rounds of whole genome duplication". Communications Biology. 4 (1): 83. doi:10.1038/s42003-020-01637-2. ISSN 2399-3642. PMC 7815833. PMID 33469163. <a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7815833" target="_blank">https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7815833</a> <a href="#fnref:29" class="footnote-back-ref">↩</a></p></li> <li id="fn:30"><p>Nong, Wenyan; Qu, Zhe; Li, Yiqian; Barton-Owen, Tom; Wong, Annette Y. P.; Yip, Ho Yin; Lee, Hoi Ting; Narayana, Satya; Baril, Tobias; Swale, Thomas; Cao, Jianquan; Chan, Ting Fung; Kwan, Hoi Shan; Ngai, Sai Ming; Panagiotou, Gianni (19 January 2021). "Horseshoe crab genomes reveal the evolution of genes and microRNAs after three rounds of whole genome duplication". Communications Biology. 4 (1): 83. doi:10.1038/s42003-020-01637-2. ISSN 2399-3642. PMC 7815833. PMID 33469163. <a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7815833" target="_blank">https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7815833</a> <a href="#fnref:30" class="footnote-back-ref">↩</a></p></li> <li id="fn:31"><p>Smith, Matthew Denman; Brockmann, H. Jane (1 October 2014). "The evolution and maintenance of sexual size dimorphism in horseshoe crabs: an evaluation of six functional hypotheses". Animal Behaviour. 96: 127–139. doi:10.1016/j.anbehav.2014.08.005. ISSN 0003-3472. <a href="https://www.sciencedirect.com/science/article/pii/S000334721400308X" target="_blank">https://www.sciencedirect.com/science/article/pii/S000334721400308X</a> <a href="#fnref:31" class="footnote-back-ref">↩</a></p></li> <li id="fn:32"><p>Smith, Matthew Denman; Brockmann, H. Jane (1 October 2014). "The evolution and maintenance of sexual size dimorphism in horseshoe crabs: an evaluation of six functional hypotheses". Animal Behaviour. 96: 127–139. doi:10.1016/j.anbehav.2014.08.005. ISSN 0003-3472. <a href="https://www.sciencedirect.com/science/article/pii/S000334721400308X" target="_blank">https://www.sciencedirect.com/science/article/pii/S000334721400308X</a> <a href="#fnref:32" class="footnote-back-ref">↩</a></p></li> <li id="fn:33"><p>Smith, Matthew Denman; Brockmann, H. Jane (1 October 2014). "The evolution and maintenance of sexual size dimorphism in horseshoe crabs: an evaluation of six functional hypotheses". Animal Behaviour. 96: 127–139. doi:10.1016/j.anbehav.2014.08.005. ISSN 0003-3472. <a href="https://www.sciencedirect.com/science/article/pii/S000334721400308X" target="_blank">https://www.sciencedirect.com/science/article/pii/S000334721400308X</a> <a href="#fnref:33" class="footnote-back-ref">↩</a></p></li> <li id="fn:34"><p>Smith, Matthew Denman; Brockmann, H. Jane (1 October 2014). "The evolution and maintenance of sexual size dimorphism in horseshoe crabs: an evaluation of six functional hypotheses". Animal Behaviour. 96: 127–139. doi:10.1016/j.anbehav.2014.08.005. ISSN 0003-3472. <a href="https://www.sciencedirect.com/science/article/pii/S000334721400308X" target="_blank">https://www.sciencedirect.com/science/article/pii/S000334721400308X</a> <a href="#fnref:34" class="footnote-back-ref">↩</a></p></li> <li id="fn:35"><p>Ruppert, Edward E.; Fox, Richard S.; Barnes, Robert D. (2004). Invertebrate zoology : a functional evolutionary approach. Internet Archive. Belmont, CA : Thomson-Brooks/Cole. ISBN 978-0-03-025982-1. <a href="978-0-03-025982-1" target="_blank">978-0-03-025982-1</a> <a href="#fnref:35" class="footnote-back-ref">↩</a></p></li> <li id="fn:36"><p>Ruppert, Edward E.; Fox, Richard S.; Barnes, Robert D. (2004). Invertebrate zoology : a functional evolutionary approach. Internet Archive. Belmont, CA : Thomson-Brooks/Cole. ISBN 978-0-03-025982-1. <a href="978-0-03-025982-1" target="_blank">978-0-03-025982-1</a> <a href="#fnref:36" class="footnote-back-ref">↩</a></p></li> <li id="fn:37"><p>Ruppert, Edward E.; Fox, Richard S.; Barnes, Robert D. (2004). Invertebrate zoology : a functional evolutionary approach. Internet Archive. Belmont, CA : Thomson-Brooks/Cole. ISBN 978-0-03-025982-1. <a href="978-0-03-025982-1" target="_blank">978-0-03-025982-1</a> <a href="#fnref:37" class="footnote-back-ref">↩</a></p></li> <li id="fn:38"><p>Ruppert, Edward E.; Fox, Richard S.; Barnes, Robert D. (2004). Invertebrate zoology : a functional evolutionary approach. Internet Archive. Belmont, CA : Thomson-Brooks/Cole. ISBN 978-0-03-025982-1. <a href="978-0-03-025982-1" target="_blank">978-0-03-025982-1</a> <a href="#fnref:38" class="footnote-back-ref">↩</a></p></li> <li id="fn:39"><p>Ruppert, Edward E.; Fox, Richard S.; Barnes, Robert D. (2004). Invertebrate zoology : a functional evolutionary approach. Internet Archive. Belmont, CA : Thomson-Brooks/Cole. ISBN 978-0-03-025982-1. <a href="978-0-03-025982-1" target="_blank">978-0-03-025982-1</a> <a href="#fnref:39" class="footnote-back-ref">↩</a></p></li> <li id="fn:40"><p>Ruppert, Edward E.; Fox, Richard S.; Barnes, Robert D. (2004). Invertebrate zoology : a functional evolutionary approach. Internet Archive. Belmont, CA : Thomson-Brooks/Cole. ISBN 978-0-03-025982-1. <a href="978-0-03-025982-1" target="_blank">978-0-03-025982-1</a> <a href="#fnref:40" class="footnote-back-ref">↩</a></p></li> <li id="fn:41"><p>Ruppert, Edward E.; Fox, Richard S.; Barnes, Robert D. (2004). Invertebrate zoology : a functional evolutionary approach. Internet Archive. Belmont, CA : Thomson-Brooks/Cole. ISBN 978-0-03-025982-1. <a href="978-0-03-025982-1" target="_blank">978-0-03-025982-1</a> <a href="#fnref:41" class="footnote-back-ref">↩</a></p></li> <li id="fn:42"><p>Ruppert, Edward E.; Fox, Richard S.; Barnes, Robert D. (2004). Invertebrate zoology : a functional evolutionary approach. Internet Archive. Belmont, CA : Thomson-Brooks/Cole. ISBN 978-0-03-025982-1. <a href="978-0-03-025982-1" target="_blank">978-0-03-025982-1</a> <a href="#fnref:42" class="footnote-back-ref">↩</a></p></li> <li id="fn:43"><p>Ruppert, Edward E.; Fox, Richard S.; Barnes, Robert D. (2004). Invertebrate zoology : a functional evolutionary approach. Internet Archive. Belmont, CA : Thomson-Brooks/Cole. ISBN 978-0-03-025982-1. <a href="978-0-03-025982-1" target="_blank">978-0-03-025982-1</a> <a href="#fnref:43" class="footnote-back-ref">↩</a></p></li> <li id="fn:44"><p>Castillo Y, Garabedian LA (26 April 2007). Limb Regeneration in Horseshoe Crabs (PDF) (B.S. thesis). Worcester Polytechnical Institute. Archived from the original (PDF) on 17 January 2023. Retrieved 2 June 2019. <a href="https://web.archive.org/web/20230117133923/https://web.wpi.edu/Pubs/E-project/Available/E-project-042607-102521/unrestricted/LimbRegenarationMQP2007LY.pdf" target="_blank">https://web.archive.org/web/20230117133923/https://web.wpi.edu/Pubs/E-project/Available/E-project-042607-102521/unrestricted/LimbRegenarationMQP2007LY.pdf</a> <a href="#fnref:44" class="footnote-back-ref">↩</a></p></li> <li id="fn:45"><p>Ruppert, Edward E.; Fox, Richard S.; Barnes, Robert D. (2004). Invertebrate zoology : a functional evolutionary approach. Internet Archive. Belmont, CA : Thomson-Brooks/Cole. ISBN 978-0-03-025982-1. <a href="978-0-03-025982-1" target="_blank">978-0-03-025982-1</a> <a href="#fnref:45" class="footnote-back-ref">↩</a></p></li> <li id="fn:46"><p>Bicknell RD, Błażejowski B, Wings O, Hitij T, Botton ML (March 2021). Zhang XG (ed.). "Critical re-evaluation of Limulidae uncovers limited Limulus diversity". Papers in Palaeontology. 7 (3): 1525–1556. Bibcode:2021PPal....7.1525B. doi:10.1002/spp2.1352. S2CID 233783546. <a href="/wiki/Bibcode_(identifier)" target="_blank">/wiki/Bibcode_(identifier)</a> <a href="#fnref:46" class="footnote-back-ref">↩</a></p></li> <li id="fn:47"><p>Bicknell RD, Błażejowski B, Wings O, Hitij T, Botton ML (March 2021). Zhang XG (ed.). "Critical re-evaluation of Limulidae uncovers limited Limulus diversity". Papers in Palaeontology. 7 (3): 1525–1556. Bibcode:2021PPal....7.1525B. doi:10.1002/spp2.1352. S2CID 233783546. <a href="/wiki/Bibcode_(identifier)" target="_blank">/wiki/Bibcode_(identifier)</a> <a href="#fnref:47" class="footnote-back-ref">↩</a></p></li> <li id="fn:48"><p>Bicknell RD, Błażejowski B, Wings O, Hitij T, Botton ML (March 2021). Zhang XG (ed.). "Critical re-evaluation of Limulidae uncovers limited Limulus diversity". Papers in Palaeontology. 7 (3): 1525–1556. Bibcode:2021PPal....7.1525B. doi:10.1002/spp2.1352. S2CID 233783546. <a href="/wiki/Bibcode_(identifier)" target="_blank">/wiki/Bibcode_(identifier)</a> <a href="#fnref:48" class="footnote-back-ref">↩</a></p></li> <li id="fn:49"><p>Ruppert, Edward E.; Fox, Richard S.; Barnes, Robert D. (2004). Invertebrate zoology : a functional evolutionary approach. Internet Archive. Belmont, CA : Thomson-Brooks/Cole. ISBN 978-0-03-025982-1. <a href="978-0-03-025982-1" target="_blank">978-0-03-025982-1</a> <a href="#fnref:49" class="footnote-back-ref">↩</a></p></li> <li id="fn:50"><p>Ruppert, Edward E.; Fox, Richard S.; Barnes, Robert D. (2004). Invertebrate zoology : a functional evolutionary approach. Internet Archive. Belmont, CA : Thomson-Brooks/Cole. ISBN 978-0-03-025982-1. <a href="978-0-03-025982-1" target="_blank">978-0-03-025982-1</a> <a href="#fnref:50" class="footnote-back-ref">↩</a></p></li> <li id="fn:51"><p>Ruppert, Edward E.; Fox, Richard S.; Barnes, Robert D. (2004). Invertebrate zoology : a functional evolutionary approach. Internet Archive. Belmont, CA : Thomson-Brooks/Cole. ISBN 978-0-03-025982-1. <a href="978-0-03-025982-1" target="_blank">978-0-03-025982-1</a> <a href="#fnref:51" class="footnote-back-ref">↩</a></p></li> <li id="fn:52"><p>Ruppert, Edward E.; Fox, Richard S.; Barnes, Robert D. (2004). Invertebrate zoology : a functional evolutionary approach. Internet Archive. Belmont, CA : Thomson-Brooks/Cole. ISBN 978-0-03-025982-1. <a href="978-0-03-025982-1" target="_blank">978-0-03-025982-1</a> <a href="#fnref:52" class="footnote-back-ref">↩</a></p></li> <li id="fn:53"><p>Battelle BA (December 2006). "The eyes of Limulus polyphemus (Xiphosura, Chelicerata) and their afferent and efferent projections". Arthropod Structure & Development. 35 (4): 261–274. Bibcode:2006ArtSD..35..261B. doi:10.1016/j.asd.2006.07.002. PMID 18089075. <a href="/wiki/Bibcode_(identifier)" target="_blank">/wiki/Bibcode_(identifier)</a> <a href="#fnref:53" class="footnote-back-ref">↩</a></p></li> <li id="fn:54"><p>"Anatomy: Vision – The Horseshoe Crab". Horseshoecrab.org. Retrieved 23 July 2024. <a href="http://www.horseshoecrab.org/anat/vision.html" target="_blank">http://www.horseshoecrab.org/anat/vision.html</a> <a href="#fnref:54" class="footnote-back-ref">↩</a></p></li> <li id="fn:55"><p>Battelle BA (December 2006). "The eyes of Limulus polyphemus (Xiphosura, Chelicerata) and their afferent and efferent projections". Arthropod Structure & Development. 35 (4): 261–274. Bibcode:2006ArtSD..35..261B. doi:10.1016/j.asd.2006.07.002. PMID 18089075. <a href="/wiki/Bibcode_(identifier)" target="_blank">/wiki/Bibcode_(identifier)</a> <a href="#fnref:55" class="footnote-back-ref">↩</a></p></li> <li id="fn:56"><p>Battelle BA (December 2006). "The eyes of Limulus polyphemus (Xiphosura, Chelicerata) and their afferent and efferent projections". Arthropod Structure & Development. 35 (4): 261–274. Bibcode:2006ArtSD..35..261B. doi:10.1016/j.asd.2006.07.002. PMID 18089075. <a href="/wiki/Bibcode_(identifier)" target="_blank">/wiki/Bibcode_(identifier)</a> <a href="#fnref:56" class="footnote-back-ref">↩</a></p></li> <li id="fn:57"><p>Battelle BA (December 2006). "The eyes of Limulus polyphemus (Xiphosura, Chelicerata) and their afferent and efferent projections". Arthropod Structure & Development. 35 (4): 261–274. Bibcode:2006ArtSD..35..261B. doi:10.1016/j.asd.2006.07.002. PMID 18089075. <a href="/wiki/Bibcode_(identifier)" target="_blank">/wiki/Bibcode_(identifier)</a> <a href="#fnref:57" class="footnote-back-ref">↩</a></p></li> <li id="fn:58"><p>Battelle BA (December 2006). "The eyes of Limulus polyphemus (Xiphosura, Chelicerata) and their afferent and efferent projections". Arthropod Structure & Development. 35 (4): 261–274. Bibcode:2006ArtSD..35..261B. doi:10.1016/j.asd.2006.07.002. PMID 18089075. <a href="/wiki/Bibcode_(identifier)" target="_blank">/wiki/Bibcode_(identifier)</a> <a href="#fnref:58" class="footnote-back-ref">↩</a></p></li> <li id="fn:59"><p>Battelle BA (December 2006). "The eyes of Limulus polyphemus (Xiphosura, Chelicerata) and their afferent and efferent projections". Arthropod Structure & Development. 35 (4): 261–274. Bibcode:2006ArtSD..35..261B. doi:10.1016/j.asd.2006.07.002. PMID 18089075. <a href="/wiki/Bibcode_(identifier)" target="_blank">/wiki/Bibcode_(identifier)</a> <a href="#fnref:59" class="footnote-back-ref">↩</a></p></li> <li id="fn:60"><p>"Anatomy: Vision – The Horseshoe Crab". Horseshoecrab.org. Retrieved 23 July 2024. <a href="http://www.horseshoecrab.org/anat/vision.html" target="_blank">http://www.horseshoecrab.org/anat/vision.html</a> <a href="#fnref:60" class="footnote-back-ref">↩</a></p></li> <li id="fn:61"><p>"Horseshoe Crabs, Limulus polyphemus". MarineBio.org. 18 May 2017. Archived from the original on 4 March 2024. Retrieved 8 March 2021. <a href="https://marinebio.org/species/horseshoe-crabs/limulus-polyphemus/" target="_blank">https://marinebio.org/species/horseshoe-crabs/limulus-polyphemus/</a> <a href="#fnref:61" class="footnote-back-ref">↩</a></p></li> <li id="fn:62"><p>Palumbi SR, Palumbi AR (23 February 2014). The Extreme Life of the Sea. Princeton University Press. ISBN 9781400849932. Archived from the original on 31 March 2022. Retrieved 12 November 2020 – via Google Books. <a href="9781400849932" target="_blank">9781400849932</a> <a href="#fnref:62" class="footnote-back-ref">↩</a></p></li> <li id="fn:63"><p>Battelle BA (December 2006). "The eyes of Limulus polyphemus (Xiphosura, Chelicerata) and their afferent and efferent projections". Arthropod Structure & Development. 35 (4): 261–274. Bibcode:2006ArtSD..35..261B. doi:10.1016/j.asd.2006.07.002. PMID 18089075. <a href="/wiki/Bibcode_(identifier)" target="_blank">/wiki/Bibcode_(identifier)</a> <a href="#fnref:63" class="footnote-back-ref">↩</a></p></li> <li id="fn:64"><p>"Anatomy: Vision – The Horseshoe Crab". Horseshoecrab.org. Retrieved 23 July 2024. <a href="http://www.horseshoecrab.org/anat/vision.html" target="_blank">http://www.horseshoecrab.org/anat/vision.html</a> <a href="#fnref:64" class="footnote-back-ref">↩</a></p></li> <li id="fn:65"><p>Battelle BA (December 2006). "The eyes of Limulus polyphemus (Xiphosura, Chelicerata) and their afferent and efferent projections". Arthropod Structure & Development. 35 (4): 261–274. Bibcode:2006ArtSD..35..261B. doi:10.1016/j.asd.2006.07.002. PMID 18089075. <a href="/wiki/Bibcode_(identifier)" target="_blank">/wiki/Bibcode_(identifier)</a> <a href="#fnref:65" class="footnote-back-ref">↩</a></p></li> <li id="fn:66"><p>Battelle BA (December 2006). "The eyes of Limulus polyphemus (Xiphosura, Chelicerata) and their afferent and efferent projections". Arthropod Structure & Development. 35 (4): 261–274. Bibcode:2006ArtSD..35..261B. doi:10.1016/j.asd.2006.07.002. PMID 18089075. <a href="/wiki/Bibcode_(identifier)" target="_blank">/wiki/Bibcode_(identifier)</a> <a href="#fnref:66" class="footnote-back-ref">↩</a></p></li> <li id="fn:67"><p>"Anatomy: Vision – The Horseshoe Crab". Horseshoecrab.org. Retrieved 23 July 2024. <a href="http://www.horseshoecrab.org/anat/vision.html" target="_blank">http://www.horseshoecrab.org/anat/vision.html</a> <a href="#fnref:67" class="footnote-back-ref">↩</a></p></li> <li id="fn:68"><p>Battelle BA (December 2006). "The eyes of Limulus polyphemus (Xiphosura, Chelicerata) and their afferent and efferent projections". Arthropod Structure & Development. 35 (4): 261–274. Bibcode:2006ArtSD..35..261B. doi:10.1016/j.asd.2006.07.002. PMID 18089075. <a href="/wiki/Bibcode_(identifier)" target="_blank">/wiki/Bibcode_(identifier)</a> <a href="#fnref:68" class="footnote-back-ref">↩</a></p></li> <li id="fn:69"><p>"Anatomy: Vision – The Horseshoe Crab". Horseshoecrab.org. Retrieved 23 July 2024. <a href="http://www.horseshoecrab.org/anat/vision.html" target="_blank">http://www.horseshoecrab.org/anat/vision.html</a> <a href="#fnref:69" class="footnote-back-ref">↩</a></p></li> <li id="fn:70"><p>Battelle BA (December 2006). "The eyes of Limulus polyphemus (Xiphosura, Chelicerata) and their afferent and efferent projections". Arthropod Structure & Development. 35 (4): 261–274. Bibcode:2006ArtSD..35..261B. doi:10.1016/j.asd.2006.07.002. PMID 18089075. <a href="/wiki/Bibcode_(identifier)" target="_blank">/wiki/Bibcode_(identifier)</a> <a href="#fnref:70" class="footnote-back-ref">↩</a></p></li> <li id="fn:71"><p>Battelle BA (December 2006). "The eyes of Limulus polyphemus (Xiphosura, Chelicerata) and their afferent and efferent projections". Arthropod Structure & Development. 35 (4): 261–274. Bibcode:2006ArtSD..35..261B. doi:10.1016/j.asd.2006.07.002. PMID 18089075. <a href="/wiki/Bibcode_(identifier)" target="_blank">/wiki/Bibcode_(identifier)</a> <a href="#fnref:71" class="footnote-back-ref">↩</a></p></li> <li id="fn:72"><p>Bicknell RD, Błażejowski B, Wings O, Hitij T, Botton ML (March 2021). Zhang XG (ed.). "Critical re-evaluation of Limulidae uncovers limited Limulus diversity". Papers in Palaeontology. 7 (3): 1525–1556. Bibcode:2021PPal....7.1525B. doi:10.1002/spp2.1352. S2CID 233783546. <a href="/wiki/Bibcode_(identifier)" target="_blank">/wiki/Bibcode_(identifier)</a> <a href="#fnref:72" class="footnote-back-ref">↩</a></p></li> <li id="fn:73"><p>"Anatomy: Vision – The Horseshoe Crab". Horseshoecrab.org. Retrieved 23 July 2024. <a href="http://www.horseshoecrab.org/anat/vision.html" target="_blank">http://www.horseshoecrab.org/anat/vision.html</a> <a href="#fnref:73" class="footnote-back-ref">↩</a></p></li> <li id="fn:74"><p>"Anatomy: Vision – The Horseshoe Crab". Horseshoecrab.org. Retrieved 23 July 2024. <a href="http://www.horseshoecrab.org/anat/vision.html" target="_blank">http://www.horseshoecrab.org/anat/vision.html</a> <a href="#fnref:74" class="footnote-back-ref">↩</a></p></li> <li id="fn:75"><p>Battelle BA (December 2006). "The eyes of Limulus polyphemus (Xiphosura, Chelicerata) and their afferent and efferent projections". Arthropod Structure & Development. 35 (4): 261–274. Bibcode:2006ArtSD..35..261B. doi:10.1016/j.asd.2006.07.002. PMID 18089075. <a href="/wiki/Bibcode_(identifier)" target="_blank">/wiki/Bibcode_(identifier)</a> <a href="#fnref:75" class="footnote-back-ref">↩</a></p></li> <li id="fn:76"><p>Ruppert, Edward E.; Fox, Richard S.; Barnes, Robert D. (2004). Invertebrate zoology : a functional evolutionary approach. Internet Archive. Belmont, CA : Thomson-Brooks/Cole. ISBN 978-0-03-025982-1. <a href="978-0-03-025982-1" target="_blank">978-0-03-025982-1</a> <a href="#fnref:76" class="footnote-back-ref">↩</a></p></li> <li id="fn:77"><p>Ruppert, Edward E.; Fox, Richard S.; Barnes, Robert D. (2004). Invertebrate zoology : a functional evolutionary approach. Internet Archive. Belmont, CA : Thomson-Brooks/Cole. ISBN 978-0-03-025982-1. <a href="978-0-03-025982-1" target="_blank">978-0-03-025982-1</a> <a href="#fnref:77" class="footnote-back-ref">↩</a></p></li> <li id="fn:78"><p>Ruppert, Edward E.; Fox, Richard S.; Barnes, Robert D. (2004). Invertebrate zoology : a functional evolutionary approach. Internet Archive. Belmont, CA : Thomson-Brooks/Cole. ISBN 978-0-03-025982-1. <a href="978-0-03-025982-1" target="_blank">978-0-03-025982-1</a> <a href="#fnref:78" class="footnote-back-ref">↩</a></p></li> <li id="fn:79"><p>Ruppert, Edward E.; Fox, Richard S.; Barnes, Robert D. (2004). Invertebrate zoology : a functional evolutionary approach. Internet Archive. Belmont, CA : Thomson-Brooks/Cole. ISBN 978-0-03-025982-1. <a href="978-0-03-025982-1" target="_blank">978-0-03-025982-1</a> <a href="#fnref:79" class="footnote-back-ref">↩</a></p></li> <li id="fn:80"><p>Ruppert, Edward E.; Fox, Richard S.; Barnes, Robert D. (2004). Invertebrate zoology : a functional evolutionary approach. Internet Archive. Belmont, CA : Thomson-Brooks/Cole. ISBN 978-0-03-025982-1. <a href="978-0-03-025982-1" target="_blank">978-0-03-025982-1</a> <a href="#fnref:80" class="footnote-back-ref">↩</a></p></li> <li id="fn:81"><p>Ruppert, Edward E.; Fox, Richard S.; Barnes, Robert D. (2004). Invertebrate zoology : a functional evolutionary approach. Internet Archive. Belmont, CA : Thomson-Brooks/Cole. ISBN 978-0-03-025982-1. <a href="978-0-03-025982-1" target="_blank">978-0-03-025982-1</a> <a href="#fnref:81" class="footnote-back-ref">↩</a></p></li> <li id="fn:82"><p>Ruppert, Edward E.; Fox, Richard S.; Barnes, Robert D. (2004). Invertebrate zoology : a functional evolutionary approach. Internet Archive. Belmont, CA : Thomson-Brooks/Cole. ISBN 978-0-03-025982-1. <a href="978-0-03-025982-1" target="_blank">978-0-03-025982-1</a> <a href="#fnref:82" class="footnote-back-ref">↩</a></p></li> <li id="fn:83"><p>Ruppert, Edward E.; Fox, Richard S.; Barnes, Robert D. (2004). Invertebrate zoology : a functional evolutionary approach. Internet Archive. Belmont, CA : Thomson-Brooks/Cole. ISBN 978-0-03-025982-1. <a href="978-0-03-025982-1" target="_blank">978-0-03-025982-1</a> <a href="#fnref:83" class="footnote-back-ref">↩</a></p></li> <li id="fn:84"><p>Ruppert, Edward E.; Fox, Richard S.; Barnes, Robert D. (2004). Invertebrate zoology : a functional evolutionary approach. Internet Archive. Belmont, CA : Thomson-Brooks/Cole. ISBN 978-0-03-025982-1. <a href="978-0-03-025982-1" target="_blank">978-0-03-025982-1</a> <a href="#fnref:84" class="footnote-back-ref">↩</a></p></li> <li id="fn:85"><p>Ruppert, Edward E.; Fox, Richard S.; Barnes, Robert D. (2004). Invertebrate zoology : a functional evolutionary approach. Internet Archive. Belmont, CA : Thomson-Brooks/Cole. ISBN 978-0-03-025982-1. <a href="978-0-03-025982-1" target="_blank">978-0-03-025982-1</a> <a href="#fnref:85" class="footnote-back-ref">↩</a></p></li> <li id="fn:86"><p>Ruppert, Edward E.; Fox, Richard S.; Barnes, Robert D. (2004). Invertebrate zoology : a functional evolutionary approach. Internet Archive. Belmont, CA : Thomson-Brooks/Cole. ISBN 978-0-03-025982-1. <a href="978-0-03-025982-1" target="_blank">978-0-03-025982-1</a> <a href="#fnref:86" class="footnote-back-ref">↩</a></p></li> <li id="fn:87"><p>Ruppert, Edward E.; Fox, Richard S.; Barnes, Robert D. (2004). Invertebrate zoology : a functional evolutionary approach. Internet Archive. Belmont, CA : Thomson-Brooks/Cole. ISBN 978-0-03-025982-1. <a href="978-0-03-025982-1" target="_blank">978-0-03-025982-1</a> <a href="#fnref:87" class="footnote-back-ref">↩</a></p></li> <li id="fn:88"><p>Ruppert, Edward E.; Fox, Richard S.; Barnes, Robert D. (2004). Invertebrate zoology : a functional evolutionary approach. Internet Archive. Belmont, CA : Thomson-Brooks/Cole. ISBN 978-0-03-025982-1. <a href="978-0-03-025982-1" target="_blank">978-0-03-025982-1</a> <a href="#fnref:88" class="footnote-back-ref">↩</a></p></li> <li id="fn:89"><p>Ruppert, Edward E.; Fox, Richard S.; Barnes, Robert D. (2004). Invertebrate zoology : a functional evolutionary approach. Internet Archive. Belmont, CA : Thomson-Brooks/Cole. ISBN 978-0-03-025982-1. <a href="978-0-03-025982-1" target="_blank">978-0-03-025982-1</a> <a href="#fnref:89" class="footnote-back-ref">↩</a></p></li> <li id="fn:90"><p>Ruppert, Edward E.; Fox, Richard S.; Barnes, Robert D. (2004). Invertebrate zoology : a functional evolutionary approach. Internet Archive. Belmont, CA : Thomson-Brooks/Cole. ISBN 978-0-03-025982-1. <a href="978-0-03-025982-1" target="_blank">978-0-03-025982-1</a> <a href="#fnref:90" class="footnote-back-ref">↩</a></p></li> <li id="fn:91"><p>Ruppert, Edward E.; Fox, Richard S.; Barnes, Robert D. (2004). Invertebrate zoology : a functional evolutionary approach. Internet Archive. Belmont, CA : Thomson-Brooks/Cole. ISBN 978-0-03-025982-1. <a href="978-0-03-025982-1" target="_blank">978-0-03-025982-1</a> <a href="#fnref:91" class="footnote-back-ref">↩</a></p></li> <li id="fn:92"><p>Ruppert, Edward E.; Fox, Richard S.; Barnes, Robert D. (2004). Invertebrate zoology : a functional evolutionary approach. Internet Archive. Belmont, CA : Thomson-Brooks/Cole. ISBN 978-0-03-025982-1. <a href="978-0-03-025982-1" target="_blank">978-0-03-025982-1</a> <a href="#fnref:92" class="footnote-back-ref">↩</a></p></li> <li id="fn:93"><p>Ruppert, Edward E.; Fox, Richard S.; Barnes, Robert D. (2004). Invertebrate zoology : a functional evolutionary approach. Internet Archive. Belmont, CA : Thomson-Brooks/Cole. ISBN 978-0-03-025982-1. <a href="978-0-03-025982-1" target="_blank">978-0-03-025982-1</a> <a href="#fnref:93" class="footnote-back-ref">↩</a></p></li> <li id="fn:94"><p>Ruppert, Edward E.; Fox, Richard S.; Barnes, Robert D. (2004). Invertebrate zoology : a functional evolutionary approach. Internet Archive. Belmont, CA : Thomson-Brooks/Cole. ISBN 978-0-03-025982-1. <a href="978-0-03-025982-1" target="_blank">978-0-03-025982-1</a> <a href="#fnref:94" class="footnote-back-ref">↩</a></p></li> <li id="fn:95"><p>Manton, Sidnie Milana (1977). The arthropoda : habits, functional morphology, and evolution. Internet Archive. Oxford [Eng.] : Clarendon Press. ISBN 978-0-19-857391-3. <a href="978-0-19-857391-3" target="_blank">978-0-19-857391-3</a> <a href="#fnref:95" class="footnote-back-ref">↩</a></p></li> <li id="fn:96"><p>Ruppert, Edward E.; Fox, Richard S.; Barnes, Robert D. (2004). Invertebrate zoology : a functional evolutionary approach. Internet Archive. Belmont, CA : Thomson-Brooks/Cole. ISBN 978-0-03-025982-1. <a href="978-0-03-025982-1" target="_blank">978-0-03-025982-1</a> <a href="#fnref:96" class="footnote-back-ref">↩</a></p></li> <li id="fn:97"><p>Manton, Sidnie Milana (1977). The arthropoda : habits, functional morphology, and evolution. Internet Archive. Oxford [Eng.] : Clarendon Press. ISBN 978-0-19-857391-3. <a href="978-0-19-857391-3" target="_blank">978-0-19-857391-3</a> <a href="#fnref:97" class="footnote-back-ref">↩</a></p></li> <li id="fn:98"><p>Manton, Sidnie Milana (1977). The arthropoda : habits, functional morphology, and evolution. Internet Archive. Oxford [Eng.] : Clarendon Press. ISBN 978-0-19-857391-3. <a href="978-0-19-857391-3" target="_blank">978-0-19-857391-3</a> <a href="#fnref:98" class="footnote-back-ref">↩</a></p></li> <li id="fn:99"><p>"Digestion: The Digestive Tract". Horseshoecrab.org. 7 August 2024. Retrieved 7 August 2024. <a href="https://horseshoecrab.org/anat/gut.html" target="_blank">https://horseshoecrab.org/anat/gut.html</a> <a href="#fnref:99" class="footnote-back-ref">↩</a></p></li> <li id="fn:100"><p>Ruppert, Edward E.; Fox, Richard S.; Barnes, Robert D. (2004). Invertebrate zoology : a functional evolutionary approach. Internet Archive. Belmont, CA : Thomson-Brooks/Cole. ISBN 978-0-03-025982-1. <a href="978-0-03-025982-1" target="_blank">978-0-03-025982-1</a> <a href="#fnref:100" class="footnote-back-ref">↩</a></p></li> <li id="fn:101"><p>Ruppert, Edward E.; Fox, Richard S.; Barnes, Robert D. (2004). Invertebrate zoology : a functional evolutionary approach. Internet Archive. Belmont, CA : Thomson-Brooks/Cole. ISBN 978-0-03-025982-1. <a href="978-0-03-025982-1" target="_blank">978-0-03-025982-1</a> <a href="#fnref:101" class="footnote-back-ref">↩</a></p></li> <li id="fn:102"><p>Ruppert, Edward E.; Fox, Richard S.; Barnes, Robert D. (2004). Invertebrate zoology : a functional evolutionary approach. Internet Archive. Belmont, CA : Thomson-Brooks/Cole. ISBN 978-0-03-025982-1. <a href="978-0-03-025982-1" target="_blank">978-0-03-025982-1</a> <a href="#fnref:102" class="footnote-back-ref">↩</a></p></li> <li id="fn:103"><p>Ruppert, Edward E.; Fox, Richard S.; Barnes, Robert D. (2004). Invertebrate zoology : a functional evolutionary approach. Internet Archive. Belmont, CA : Thomson-Brooks/Cole. ISBN 978-0-03-025982-1. <a href="978-0-03-025982-1" target="_blank">978-0-03-025982-1</a> <a href="#fnref:103" class="footnote-back-ref">↩</a></p></li> <li id="fn:104"><p>Ruppert, Edward E.; Fox, Richard S.; Barnes, Robert D. (2004). Invertebrate zoology : a functional evolutionary approach. Internet Archive. Belmont, CA : Thomson-Brooks/Cole. ISBN 978-0-03-025982-1. <a href="978-0-03-025982-1" target="_blank">978-0-03-025982-1</a> <a href="#fnref:104" class="footnote-back-ref">↩</a></p></li> <li id="fn:105"><p>Ruppert, Edward E.; Fox, Richard S.; Barnes, Robert D. (2004). Invertebrate zoology : a functional evolutionary approach. Internet Archive. Belmont, CA : Thomson-Brooks/Cole. ISBN 978-0-03-025982-1. <a href="978-0-03-025982-1" target="_blank">978-0-03-025982-1</a> <a href="#fnref:105" class="footnote-back-ref">↩</a></p></li> <li id="fn:106"><p>Ruppert, Edward E.; Fox, Richard S.; Barnes, Robert D. (2004). Invertebrate zoology : a functional evolutionary approach. Internet Archive. Belmont, CA : Thomson-Brooks/Cole. ISBN 978-0-03-025982-1. <a href="978-0-03-025982-1" target="_blank">978-0-03-025982-1</a> <a href="#fnref:106" class="footnote-back-ref">↩</a></p></li> <li id="fn:107"><p>Ruppert, Edward E.; Fox, Richard S.; Barnes, Robert D. (2004). Invertebrate zoology : a functional evolutionary approach. Internet Archive. Belmont, CA : Thomson-Brooks/Cole. ISBN 978-0-03-025982-1. <a href="978-0-03-025982-1" target="_blank">978-0-03-025982-1</a> <a href="#fnref:107" class="footnote-back-ref">↩</a></p></li> <li id="fn:108"><p>Ruppert, Edward E.; Fox, Richard S.; Barnes, Robert D. (2004). Invertebrate zoology : a functional evolutionary approach. Internet Archive. Belmont, CA : Thomson-Brooks/Cole. ISBN 978-0-03-025982-1. <a href="978-0-03-025982-1" target="_blank">978-0-03-025982-1</a> <a href="#fnref:108" class="footnote-back-ref">↩</a></p></li> <li id="fn:109"><p>Ruppert, Edward E.; Fox, Richard S.; Barnes, Robert D. (2004). Invertebrate zoology : a functional evolutionary approach. Internet Archive. Belmont, CA : Thomson-Brooks/Cole. ISBN 978-0-03-025982-1. <a href="978-0-03-025982-1" target="_blank">978-0-03-025982-1</a> <a href="#fnref:109" class="footnote-back-ref">↩</a></p></li> <li id="fn:110"><p>Ruppert, Edward E.; Fox, Richard S.; Barnes, Robert D. (2004). Invertebrate zoology : a functional evolutionary approach. Internet Archive. Belmont, CA : Thomson-Brooks/Cole. ISBN 978-0-03-025982-1. <a href="978-0-03-025982-1" target="_blank">978-0-03-025982-1</a> <a href="#fnref:110" class="footnote-back-ref">↩</a></p></li> <li id="fn:111"><p>Ruppert, Edward E.; Fox, Richard S.; Barnes, Robert D. (2004). Invertebrate zoology : a functional evolutionary approach. Internet Archive. Belmont, CA : Thomson-Brooks/Cole. ISBN 978-0-03-025982-1. <a href="978-0-03-025982-1" target="_blank">978-0-03-025982-1</a> <a href="#fnref:111" class="footnote-back-ref">↩</a></p></li> <li id="fn:112"><p>"Digestion: The Digestive Tract". Horseshoecrab.org. 7 August 2024. Retrieved 7 August 2024. <a href="https://horseshoecrab.org/anat/gut.html" target="_blank">https://horseshoecrab.org/anat/gut.html</a> <a href="#fnref:112" class="footnote-back-ref">↩</a></p></li> <li id="fn:113"><p>Ruppert, Edward E.; Fox, Richard S.; Barnes, Robert D. (2004). Invertebrate zoology : a functional evolutionary approach. Internet Archive. Belmont, CA : Thomson-Brooks/Cole. ISBN 978-0-03-025982-1. <a href="978-0-03-025982-1" target="_blank">978-0-03-025982-1</a> <a href="#fnref:113" class="footnote-back-ref">↩</a></p></li> <li id="fn:114"><p>Ruppert, Edward E.; Fox, Richard S.; Barnes, Robert D. (2004). Invertebrate zoology : a functional evolutionary approach. Internet Archive. Belmont, CA : Thomson-Brooks/Cole. ISBN 978-0-03-025982-1. <a href="978-0-03-025982-1" target="_blank">978-0-03-025982-1</a> <a href="#fnref:114" class="footnote-back-ref">↩</a></p></li> <li id="fn:115"><p>Lamsdell JC (4 December 2020). "The phylogeny and systematics of Xiphosura". PeerJ. 8: e10431. doi:10.7717/peerj.10431. PMC 7720731. PMID 33335810. <a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7720731" target="_blank">https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7720731</a> <a href="#fnref:115" class="footnote-back-ref">↩</a></p></li> <li id="fn:116"><p>Lamsdell JC (4 December 2020). "The phylogeny and systematics of Xiphosura". PeerJ. 8: e10431. doi:10.7717/peerj.10431. PMC 7720731. PMID 33335810. <a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7720731" target="_blank">https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7720731</a> <a href="#fnref:116" class="footnote-back-ref">↩</a></p></li> <li id="fn:117"><p>Lamsdell JC (4 December 2020). "The phylogeny and systematics of Xiphosura". PeerJ. 8: e10431. doi:10.7717/peerj.10431. PMC 7720731. PMID 33335810. <a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7720731" target="_blank">https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7720731</a> <a href="#fnref:117" class="footnote-back-ref">↩</a></p></li> <li id="fn:118"><p>"Carcinoscorpius rotundicauda, mangrove horseshoe crab". SeaLifeBase. 2010. Retrieved 23 April 2011. <a href="http://www.sealifebase.org/Summary/SpeciesSummary.php?ID=25" target="_blank">http://www.sealifebase.org/Summary/SpeciesSummary.php?ID=25</a> <a href="#fnref:118" class="footnote-back-ref">↩</a></p></li> <li id="fn:119"><p>Lamsdell, James C. (November 2015). Zhang, Xi-Guang (ed.). "Horseshoe crab phylogeny and independent colonizations of fresh water: ecological invasion as a driver for morphological innovation". Palaeontology. 59 (2): 181–194. Bibcode:2016Palgy..59..181L. doi:10.1111/pala.12220. ISSN 0031-0239. <a href="https://onlinelibrary.wiley.com/doi/10.1111/pala.12220" target="_blank">https://onlinelibrary.wiley.com/doi/10.1111/pala.12220</a> <a href="#fnref:119" class="footnote-back-ref">↩</a></p></li> <li id="fn:120"><p>Lamsdell, James C. (November 2015). Zhang, Xi-Guang (ed.). "Horseshoe crab phylogeny and independent colonizations of fresh water: ecological invasion as a driver for morphological innovation". Palaeontology. 59 (2): 181–194. Bibcode:2016Palgy..59..181L. doi:10.1111/pala.12220. ISSN 0031-0239. <a href="https://onlinelibrary.wiley.com/doi/10.1111/pala.12220" target="_blank">https://onlinelibrary.wiley.com/doi/10.1111/pala.12220</a> <a href="#fnref:120" class="footnote-back-ref">↩</a></p></li> <li id="fn:121"><p>"Horseshoe Crabs". MarineBio Conservation Society. 18 May 2017. Archived from the original on 4 March 2024. Retrieved 23 January 2022. <a href="https://www.marinebio.org/species/horseshoe-crabs/limulus-polyphemus/" target="_blank">https://www.marinebio.org/species/horseshoe-crabs/limulus-polyphemus/</a> <a href="#fnref:121" class="footnote-back-ref">↩</a></p></li> <li id="fn:122"><p>Whitaker, David. "Horseshoe Crabs". South Carolina Department of Natural Resources. Retrieved 26 April 2024. <a href="https://www.dnr.sc.gov/marine/pub/seascience/horseshoecrab.html" target="_blank">https://www.dnr.sc.gov/marine/pub/seascience/horseshoecrab.html</a> <a href="#fnref:122" class="footnote-back-ref">↩</a></p></li> <li id="fn:123"><p>"Horseshoe Crab". National Wildlife Federation. Retrieved 12 April 2024. <a href="https://www.nwf.org/Educational-Resources/Wildlife-Guide/Invertebrates/Horseshoe-Crab" target="_blank">https://www.nwf.org/Educational-Resources/Wildlife-Guide/Invertebrates/Horseshoe-Crab</a> <a href="#fnref:123" class="footnote-back-ref">↩</a></p></li> <li id="fn:124"><p>Vosatka, ed. (1970). "Observations on the Swimming, Righting, and Burrowing Movements of Young Horseshoe Crabs, Limulus Polyphemus". The Ohio Journal of Science. 70 (5): 276–283. hdl:1811/5558. <a href="/wiki/Hdl_(identifier)" target="_blank">/wiki/Hdl_(identifier)</a> <a href="#fnref:124" class="footnote-back-ref">↩</a></p></li> <li id="fn:125"><p>Vosatka, ed. (1970). "Observations on the Swimming, Righting, and Burrowing Movements of Young Horseshoe Crabs, Limulus Polyphemus". The Ohio Journal of Science. 70 (5): 276–283. hdl:1811/5558. <a href="/wiki/Hdl_(identifier)" target="_blank">/wiki/Hdl_(identifier)</a> <a href="#fnref:125" class="footnote-back-ref">↩</a></p></li> <li id="fn:126"><p>Vosatka, ed. (1970). "Observations on the Swimming, Righting, and Burrowing Movements of Young Horseshoe Crabs, Limulus Polyphemus". The Ohio Journal of Science. 70 (5): 276–283. hdl:1811/5558. <a href="/wiki/Hdl_(identifier)" target="_blank">/wiki/Hdl_(identifier)</a> <a href="#fnref:126" class="footnote-back-ref">↩</a></p></li> <li id="fn:127"><p>Vosatka, ed. (1970). "Observations on the Swimming, Righting, and Burrowing Movements of Young Horseshoe Crabs, Limulus Polyphemus". The Ohio Journal of Science. 70 (5): 276–283. hdl:1811/5558. <a href="/wiki/Hdl_(identifier)" target="_blank">/wiki/Hdl_(identifier)</a> <a href="#fnref:127" class="footnote-back-ref">↩</a></p></li> <li id="fn:128"><p>Vosatka, ed. (1970). "Observations on the Swimming, Righting, and Burrowing Movements of Young Horseshoe Crabs, Limulus Polyphemus". The Ohio Journal of Science. 70 (5): 276–283. hdl:1811/5558. <a href="/wiki/Hdl_(identifier)" target="_blank">/wiki/Hdl_(identifier)</a> <a href="#fnref:128" class="footnote-back-ref">↩</a></p></li> <li id="fn:129"><p>Vosatka, ed. (1970). "Observations on the Swimming, Righting, and Burrowing Movements of Young Horseshoe Crabs, Limulus Polyphemus". The Ohio Journal of Science. 70 (5): 276–283. hdl:1811/5558. <a href="/wiki/Hdl_(identifier)" target="_blank">/wiki/Hdl_(identifier)</a> <a href="#fnref:129" class="footnote-back-ref">↩</a></p></li> <li id="fn:130"><p>Vosatka, ed. (1970). "Observations on the Swimming, Righting, and Burrowing Movements of Young Horseshoe Crabs, Limulus Polyphemus". The Ohio Journal of Science. 70 (5): 276–283. hdl:1811/5558. <a href="/wiki/Hdl_(identifier)" target="_blank">/wiki/Hdl_(identifier)</a> <a href="#fnref:130" class="footnote-back-ref">↩</a></p></li> <li id="fn:131"><p>Vosatka, ed. (1970). "Observations on the Swimming, Righting, and Burrowing Movements of Young Horseshoe Crabs, Limulus Polyphemus". The Ohio Journal of Science. 70 (5): 276–283. hdl:1811/5558. <a href="/wiki/Hdl_(identifier)" target="_blank">/wiki/Hdl_(identifier)</a> <a href="#fnref:131" class="footnote-back-ref">↩</a></p></li> <li id="fn:132"><p>Ruppert, Edward E.; Fox, Richard S.; Barnes, Robert D. (2004). Invertebrate zoology : a functional evolutionary approach. Internet Archive. Belmont, CA : Thomson-Brooks/Cole. ISBN 978-0-03-025982-1. <a href="978-0-03-025982-1" target="_blank">978-0-03-025982-1</a> <a href="#fnref:132" class="footnote-back-ref">↩</a></p></li> <li id="fn:133"><p>Ruppert, Edward E.; Fox, Richard S.; Barnes, Robert D. (2004). Invertebrate zoology : a functional evolutionary approach. Internet Archive. Belmont, CA : Thomson-Brooks/Cole. ISBN 978-0-03-025982-1. <a href="978-0-03-025982-1" target="_blank">978-0-03-025982-1</a> <a href="#fnref:133" class="footnote-back-ref">↩</a></p></li> <li id="fn:134"><p>Ruppert, Edward E.; Fox, Richard S.; Barnes, Robert D. (2004). Invertebrate zoology : a functional evolutionary approach. Internet Archive. Belmont, CA : Thomson-Brooks/Cole. ISBN 978-0-03-025982-1. <a href="978-0-03-025982-1" target="_blank">978-0-03-025982-1</a> <a href="#fnref:134" class="footnote-back-ref">↩</a></p></li> <li id="fn:135"><p>Ruppert, Edward E.; Fox, Richard S.; Barnes, Robert D. (2004). Invertebrate zoology : a functional evolutionary approach. Internet Archive. Belmont, CA : Thomson-Brooks/Cole. ISBN 978-0-03-025982-1. <a href="978-0-03-025982-1" target="_blank">978-0-03-025982-1</a> <a href="#fnref:135" class="footnote-back-ref">↩</a></p></li> <li id="fn:136"><p>Cartwright-Taylor L, Lee J, Hsu CC (2009). "Population structure and breeding pattern of the mangrove horseshoe crab Carcinoscorpius rotundicauda in Singapore" (PDF). Aquatic Biology. 8 (1): 61–69. doi:10.3354/ab00206. Archived (PDF) from the original on 1 August 2020. Retrieved 27 January 2020. <a href="https://www.int-res.com/articles/ab2009/8/b008p061.pdf" target="_blank">https://www.int-res.com/articles/ab2009/8/b008p061.pdf</a> <a href="#fnref:136" class="footnote-back-ref">↩</a></p></li> <li id="fn:137"><p>Cartwright-Taylor L, Lee J, Hsu CC (2009). "Population structure and breeding pattern of the mangrove horseshoe crab Carcinoscorpius rotundicauda in Singapore" (PDF). Aquatic Biology. 8 (1): 61–69. doi:10.3354/ab00206. Archived (PDF) from the original on 1 August 2020. Retrieved 27 January 2020. <a href="https://www.int-res.com/articles/ab2009/8/b008p061.pdf" target="_blank">https://www.int-res.com/articles/ab2009/8/b008p061.pdf</a> <a href="#fnref:137" class="footnote-back-ref">↩</a></p></li> <li id="fn:138"><p>Zaldívar-Rae J, Sapién-Silva RE, Rosales-Raya M, Brockmann HJ (2009). "American horseshoe crabs, Limulus polyphemus, in México: open possibilities". In J.T. Tanacredi, M.L. Botton, D.R. Smith (eds.). Biology and Conservation of Horseshoe Crabs. Springer. pp. 97–113. ISBN 9780387899589. <a href="9780387899589" target="_blank">9780387899589</a> <a href="#fnref:138" class="footnote-back-ref">↩</a></p></li> <li id="fn:139"><p>"About the Species". The Horseshoe Crab. Archived from the original on 12 February 2007. Retrieved 26 June 2018. <a href="http://www.horseshoecrab.org/nh/species.html" target="_blank">http://www.horseshoecrab.org/nh/species.html</a> <a href="#fnref:139" class="footnote-back-ref">↩</a></p></li> <li id="fn:140"><p>Srijaya TC, Pradeep PJ, Mithun S, Hassan A, Shaharom F, Chatterji A (2010). "A New Record on the Morphometric Variations in the Populations of Horseshoe Crab (Carcinoscorpius rotundicauda Latreille) Obtained from Two Different Ecological Habitats of Peninsular Malaysia". Our Nature. 8 (1): 204–211. doi:10.3126/on.v8i1.4329. <a href="https://doi.org/10.3126%2Fon.v8i1.4329" target="_blank">https://doi.org/10.3126%2Fon.v8i1.4329</a> <a href="#fnref:140" class="footnote-back-ref">↩</a></p></li> <li id="fn:141"><p>Zaldívar-Rae J, Sapién-Silva RE, Rosales-Raya M, Brockmann HJ (2009). "American horseshoe crabs, Limulus polyphemus, in México: open possibilities". In J.T. Tanacredi, M.L. Botton, D.R. Smith (eds.). Biology and Conservation of Horseshoe Crabs. Springer. pp. 97–113. ISBN 9780387899589. <a href="9780387899589" target="_blank">9780387899589</a> <a href="#fnref:141" class="footnote-back-ref">↩</a></p></li> <li id="fn:142"><p>Manca A, Mohamad F, Ahmad A, Sofa MF, Ismail N (2017). "Tri-spine horseshoe crab, Tachypleus tridentatus (L.) in Sabah, Malaysia: the adult body sizes and population estimate". Journal of Asia-Pacific Biodiversity. 10 (3): 355–361. doi:10.1016/j.japb.2017.04.011. <a href="https://doi.org/10.1016%2Fj.japb.2017.04.011" target="_blank">https://doi.org/10.1016%2Fj.japb.2017.04.011</a> <a href="#fnref:142" class="footnote-back-ref">↩</a></p></li> <li id="fn:143"><p>"Horseshoe Crab (Limulus polyphemus)". WAZA. Archived from the original on 3 July 2017. Retrieved 26 June 2018. <a href="https://web.archive.org/web/20170703001436/http://www.waza.org/en/zoo/choose-a-species/invertebrates/other-aquatic-invertebrates/limulus-polyphemus" target="_blank">https://web.archive.org/web/20170703001436/http://www.waza.org/en/zoo/choose-a-species/invertebrates/other-aquatic-invertebrates/limulus-polyphemus</a> <a href="#fnref:143" class="footnote-back-ref">↩</a></p></li> <li id="fn:144"><p>Jawahir AR, Samsur M, Shabdin ML, Rahim KA (2017). "Morphometric allometry of horseshoe crab, Tachypleus gigas at west part of Sarawak waters, Borneo, East Malaysia". AACL Bioflux. 10 (1): 18–24. <a href="#fnref:144" class="footnote-back-ref">↩</a></p></li> <li id="fn:145"><p>"Facts About Horseshoe Crabs and FAQ". Florida Fish and Wildlife Conservation Commission. Archived from the original on 4 June 2023. Retrieved 19 January 2020. <a href="https://myfwc.com/research/saltwater/crustaceans/horseshoe-crabs/facts/" target="_blank">https://myfwc.com/research/saltwater/crustaceans/horseshoe-crabs/facts/</a> <a href="#fnref:145" class="footnote-back-ref">↩</a></p></li> <li id="fn:146"><p>"Facts About Horseshoe Crabs and FAQ". Florida Fish and Wildlife Conservation Commission. Archived from the original on 4 June 2023. Retrieved 19 January 2020. <a href="https://myfwc.com/research/saltwater/crustaceans/horseshoe-crabs/facts/" target="_blank">https://myfwc.com/research/saltwater/crustaceans/horseshoe-crabs/facts/</a> <a href="#fnref:146" class="footnote-back-ref">↩</a></p></li> <li id="fn:147"><p>Sasson, Daniel A; Chabot, Christopher C; Mattei, Jennifer H; Brunson, Jeff F; Hall, Fletcher K; Huber, Jeanette H; Kasinak, Jo-Marie E; McShane, Cole; Puckette, Paul T; Sundin, Gary; Kingsley-Smith, Peter R; Kendrick, Michael R (April 2024). "The American horseshoe crab ( Limulus polyphemus ) spawns regularly in salt marshes". Frontiers in Ecology and the Environment. 22 (5). Bibcode:2024FrEE...22E2738S. doi:10.1002/fee.2738. ISSN 1540-9295. <a href="https://doi.org/10.1002%2Ffee.2738" target="_blank">https://doi.org/10.1002%2Ffee.2738</a> <a href="#fnref:147" class="footnote-back-ref">↩</a></p></li> <li id="fn:148"><p>"Facts About Horseshoe Crabs and FAQ". Florida Fish and Wildlife Conservation Commission. Archived from the original on 4 June 2023. Retrieved 19 January 2020. <a href="https://myfwc.com/research/saltwater/crustaceans/horseshoe-crabs/facts/" target="_blank">https://myfwc.com/research/saltwater/crustaceans/horseshoe-crabs/facts/</a> <a href="#fnref:148" class="footnote-back-ref">↩</a></p></li> <li id="fn:149"><p>"The Horseshoe Crab, limulus polyphemus: 200 Millions Years of Existence, 100 Years of study". 2002. Archived (PDF) from the original on 11 November 2020. Retrieved 3 February 2020. <a href="http://nsmn1.uh.edu/dgraur/popbio/horseshoe%20crab,%20Limulus%20polyphemus%20200%20million%20years%20of%20existence,%20100%20years%20of%20study.pdf/" target="_blank">http://nsmn1.uh.edu/dgraur/popbio/horseshoe%20crab,%20Limulus%20polyphemus%20200%20million%20years%20of%20existence,%20100%20years%20of%20study.pdf/</a> <a href="#fnref:149" class="footnote-back-ref">↩</a></p></li> <li id="fn:150"><p>Ruppert, Edward E.; Fox, Richard S.; Barnes, Robert D. (2004). Invertebrate zoology : a functional evolutionary approach. Internet Archive. Belmont, CA : Thomson-Brooks/Cole. ISBN 978-0-03-025982-1. <a href="978-0-03-025982-1" target="_blank">978-0-03-025982-1</a> <a href="#fnref:150" class="footnote-back-ref">↩</a></p></li> <li id="fn:151"><p>Ruppert, Edward E.; Fox, Richard S.; Barnes, Robert D. (2004). Invertebrate zoology : a functional evolutionary approach. Internet Archive. Belmont, CA : Thomson-Brooks/Cole. ISBN 978-0-03-025982-1. <a href="978-0-03-025982-1" target="_blank">978-0-03-025982-1</a> <a href="#fnref:151" class="footnote-back-ref">↩</a></p></li> <li id="fn:152"><p>"Facts About Horseshoe Crabs and FAQ". Florida Fish and Wildlife Conservation Commission. Archived from the original on 4 June 2023. Retrieved 19 January 2020. <a href="https://myfwc.com/research/saltwater/crustaceans/horseshoe-crabs/facts/" target="_blank">https://myfwc.com/research/saltwater/crustaceans/horseshoe-crabs/facts/</a> <a href="#fnref:152" class="footnote-back-ref">↩</a></p></li> <li id="fn:153"><p>"Facts About Horseshoe Crabs and FAQ". Florida Fish and Wildlife Conservation Commission. Archived from the original on 4 June 2023. Retrieved 19 January 2020. <a href="https://myfwc.com/research/saltwater/crustaceans/horseshoe-crabs/facts/" target="_blank">https://myfwc.com/research/saltwater/crustaceans/horseshoe-crabs/facts/</a> <a href="#fnref:153" class="footnote-back-ref">↩</a></p></li> <li id="fn:154"><p>"Facts About Horseshoe Crabs and FAQ". Florida Fish and Wildlife Conservation Commission. Archived from the original on 4 June 2023. Retrieved 19 January 2020. <a href="https://myfwc.com/research/saltwater/crustaceans/horseshoe-crabs/facts/" target="_blank">https://myfwc.com/research/saltwater/crustaceans/horseshoe-crabs/facts/</a> <a href="#fnref:154" class="footnote-back-ref">↩</a></p></li> <li id="fn:155"><p>Funkhouser D (15 April 2011). "Crab love nest". Scientific American. 304 (4): 29. Bibcode:2011SciAm.304d..29F. doi:10.1038/scientificamerican0411-29. <a href="/wiki/Scientific_American" target="_blank">/wiki/Scientific_American</a> <a href="#fnref:155" class="footnote-back-ref">↩</a></p></li> <li id="fn:156"><p>Funkhouser D (15 April 2011). "Crab love nest". Scientific American. 304 (4): 29. Bibcode:2011SciAm.304d..29F. doi:10.1038/scientificamerican0411-29. <a href="/wiki/Scientific_American" target="_blank">/wiki/Scientific_American</a> <a href="#fnref:156" class="footnote-back-ref">↩</a></p></li> <li id="fn:157"><p>Funkhouser D (15 April 2011). "Crab love nest". Scientific American. 304 (4): 29. Bibcode:2011SciAm.304d..29F. doi:10.1038/scientificamerican0411-29. <a href="/wiki/Scientific_American" target="_blank">/wiki/Scientific_American</a> <a href="#fnref:157" class="footnote-back-ref">↩</a></p></li> <li id="fn:158"><p>Brown, George Gordon; Clapper, David L. (1981). Procedures for maintaining adults, collecting gametes, and culturing embryos and juveniles of the horseshoe crab, Limulus polyphemus L. Internet Archive. Washington, D.C. : National Academy Press. ISBN 978-0-309-03134-9. <a href="978-0-309-03134-9" target="_blank">978-0-309-03134-9</a> <a href="#fnref:158" class="footnote-back-ref">↩</a></p></li> <li id="fn:159"><p>Chen Y, Lau CW, Cheung SG, Ke CH, Shin PK (2010). "Enhanced growth of juvenile Tachypleus tridentatus (Chelicerata: Xiphosura) in the laboratory: a step towards population restocking for conservation of the species". Aquatic Biology. 11: 37–40. doi:10.3354/ab00289. <a href="https://doi.org/10.3354%2Fab00289" target="_blank">https://doi.org/10.3354%2Fab00289</a> <a href="#fnref:159" class="footnote-back-ref">↩</a></p></li> <li id="fn:160"><p>Carmichael, Ruth H.; Brush, Erik (2012). "Three decades of horseshoe crab rearing: a review of conditions for captive growth and survival". Reviews in Aquaculture. 4 (1): 32–43. Bibcode:2012RvAq....4...32C. doi:10.1111/j.1753-5131.2012.01059.x. ISSN 1753-5123 – via Wiley Online Library. <a href="https://onlinelibrary.wiley.com/doi/10.1111/j.1753-5131.2012.01059.x" target="_blank">https://onlinelibrary.wiley.com/doi/10.1111/j.1753-5131.2012.01059.x</a> <a href="#fnref:160" class="footnote-back-ref">↩</a></p></li> <li id="fn:161"><p>"Can You Eat Horseshoe Crab and How Does It Taste? - American Oceans". 31 October 2022. Retrieved 13 July 2024. <a href="https://www.americanoceans.org/blog/can-you-eat-horseshoe-crab/" target="_blank">https://www.americanoceans.org/blog/can-you-eat-horseshoe-crab/</a> <a href="#fnref:161" class="footnote-back-ref">↩</a></p></li> <li id="fn:162"><p>"Can You Eat Horseshoe Crab and How Does It Taste? - American Oceans". 31 October 2022. Retrieved 13 July 2024. <a href="https://www.americanoceans.org/blog/can-you-eat-horseshoe-crab/" target="_blank">https://www.americanoceans.org/blog/can-you-eat-horseshoe-crab/</a> <a href="#fnref:162" class="footnote-back-ref">↩</a></p></li> <li id="fn:163"><p>"Can You Eat Horseshoe Crab and How Does It Taste? - American Oceans". 31 October 2022. Retrieved 13 July 2024. <a href="https://www.americanoceans.org/blog/can-you-eat-horseshoe-crab/" target="_blank">https://www.americanoceans.org/blog/can-you-eat-horseshoe-crab/</a> <a href="#fnref:163" class="footnote-back-ref">↩</a></p></li> <li id="fn:164"><p>Kanchanapongkul, J.; Krittayapoositpot, P. (June 1995). "An epidemic of tetrodotoxin poisoning following ingestion of the horseshoe crab Carcinoscorpius rotundicauda". The Southeast Asian Journal of Tropical Medicine and Public Health. 26 (2): 364–367. ISSN 0125-1562. PMID 8629077. <a href="/wiki/ISSN_(identifier)" target="_blank">/wiki/ISSN_(identifier)</a> <a href="#fnref:164" class="footnote-back-ref">↩</a></p></li> <li id="fn:165"><p>"Can You Eat Horseshoe Crab and How Does It Taste? - American Oceans". 31 October 2022. Retrieved 13 July 2024. <a href="https://www.americanoceans.org/blog/can-you-eat-horseshoe-crab/" target="_blank">https://www.americanoceans.org/blog/can-you-eat-horseshoe-crab/</a> <a href="#fnref:165" class="footnote-back-ref">↩</a></p></li> <li id="fn:166"><p>"Can You Eat Horseshoe Crab and How Does It Taste? - American Oceans". 31 October 2022. Retrieved 13 July 2024. <a href="https://www.americanoceans.org/blog/can-you-eat-horseshoe-crab/" target="_blank">https://www.americanoceans.org/blog/can-you-eat-horseshoe-crab/</a> <a href="#fnref:166" class="footnote-back-ref">↩</a></p></li> <li id="fn:167"><p>"Can You Eat Horseshoe Crab and How Does It Taste? - American Oceans". 31 October 2022. Retrieved 13 July 2024. <a href="https://www.americanoceans.org/blog/can-you-eat-horseshoe-crab/" target="_blank">https://www.americanoceans.org/blog/can-you-eat-horseshoe-crab/</a> <a href="#fnref:167" class="footnote-back-ref">↩</a></p></li> <li id="fn:168"><p>Kungsuwan A, Suvapeepan S, Suwansakornkul P, Shida Y, Suvapeepan S, Suwansakornkul P, Hashimoto K (1987). "Tetrodotoxin in the Horseshoe Crab Carcinoscorpius rotundicauda Inhabiting Thailand" (PDF). Nippon Suisan Gakkaishi. 53 (2): 261–266. doi:10.2331/suisan.53.261. Archived from the original on 1 August 2020. Retrieved 21 April 2014. <a href="https://www.jstage.jst.go.jp/article/suisan1932/53/2/53_2_261/_pdf" target="_blank">https://www.jstage.jst.go.jp/article/suisan1932/53/2/53_2_261/_pdf</a> <a href="#fnref:168" class="footnote-back-ref">↩</a></p></li> <li id="fn:169"><p>"N.J. law protects horseshoe crabs". UPI. 25 March 2008. Archived from the original on 27 July 2018. Retrieved 27 July 2018. <a href="https://www.upi.com/NJ-law-protects-horseshoe-crabs/55701206482051/" target="_blank">https://www.upi.com/NJ-law-protects-horseshoe-crabs/55701206482051/</a> <a href="#fnref:169" class="footnote-back-ref">↩</a></p></li> <li id="fn:170"><p>"N.J. law protects horseshoe crabs". UPI. 25 March 2008. Archived from the original on 27 July 2018. Retrieved 27 July 2018. <a href="https://www.upi.com/NJ-law-protects-horseshoe-crabs/55701206482051/" target="_blank">https://www.upi.com/NJ-law-protects-horseshoe-crabs/55701206482051/</a> <a href="#fnref:170" class="footnote-back-ref">↩</a></p></li> <li id="fn:171"><p>"N.J. law protects horseshoe crabs". UPI. 25 March 2008. Archived from the original on 27 July 2018. Retrieved 27 July 2018. <a href="https://www.upi.com/NJ-law-protects-horseshoe-crabs/55701206482051/" target="_blank">https://www.upi.com/NJ-law-protects-horseshoe-crabs/55701206482051/</a> <a href="#fnref:171" class="footnote-back-ref">↩</a></p></li> <li id="fn:172"><p>"Horseshoe crab sanctuary advocates say DNREC must enforce harvesting rules". Delaware First Media. Retrieved 23 August 2024. <a href="https://www.delawarepublic.org/show/the-green/2024-04-05/horseshoe-crab-sanctuary-advocates-say-dnrec-must-enforce-harvesting-rules" target="_blank">https://www.delawarepublic.org/show/the-green/2024-04-05/horseshoe-crab-sanctuary-advocates-say-dnrec-must-enforce-harvesting-rules</a> <a href="#fnref:172" class="footnote-back-ref">↩</a></p></li> <li id="fn:173"><p>"Horseshoe crab". SC DNR species gallery. Archived from the original on 31 March 2016. Retrieved 6 June 2011. <a href="http://dnr.sc.gov/marine/mrri/acechar/speciesgallery/Invertebrates/HorseshoeCrab/index.html" target="_blank">http://dnr.sc.gov/marine/mrri/acechar/speciesgallery/Invertebrates/HorseshoeCrab/index.html</a> <a href="#fnref:173" class="footnote-back-ref">↩</a></p></li> <li id="fn:174"><p>Rupert, Edward E.; Fox, Richard S.; Barnes, Robert D. (2004). Invertebrate zoology : a functional evolutionary approach. Internet Archive. Belmont, CA : Thomson-Brooks/Cole. p. 558. ISBN 978-0-03-025982-1. <a href="978-0-03-025982-1" target="_blank">978-0-03-025982-1</a> <a href="#fnref:174" class="footnote-back-ref">↩</a></p></li> <li id="fn:175"><p>"The horseshoe crab and public health". HorseshoeCrab.org. Archived from the original on 21 October 2001. Retrieved 5 April 2011. <a href="http://www.horseshoecrab.org/med/med.html" target="_blank">http://www.horseshoecrab.org/med/med.html</a> <a href="#fnref:175" class="footnote-back-ref">↩</a></p></li> <li id="fn:176"><p>"The horseshoe crab and public health". HorseshoeCrab.org. Archived from the original on 21 October 2001. Retrieved 5 April 2011. <a href="http://www.horseshoecrab.org/med/med.html" target="_blank">http://www.horseshoecrab.org/med/med.html</a> <a href="#fnref:176" class="footnote-back-ref">↩</a></p></li> <li id="fn:177"><p>Hurton L (2003). Reducing post-bleeding mortality of horseshoe crabs (Limulus polyphemus) used in the biomedical industry (PDF) (M.Sc. thesis). Virginia Polytechnic Institute and State University. hdl:10919/36231. Archived from the original on 22 June 2013. Retrieved 20 September 2020. <a href="https://web.archive.org/web/20130622155603/http://scholar.lib.vt.edu/theses/available/etd-12172003-122534/unrestricted/HurtonThesis.pdf" target="_blank">https://web.archive.org/web/20130622155603/http://scholar.lib.vt.edu/theses/available/etd-12172003-122534/unrestricted/HurtonThesis.pdf</a> <a href="#fnref:177" class="footnote-back-ref">↩</a></p></li> <li id="fn:178"><p>Hurton L (2003). Reducing post-bleeding mortality of horseshoe crabs (Limulus polyphemus) used in the biomedical industry (PDF) (M.Sc. thesis). Virginia Polytechnic Institute and State University. hdl:10919/36231. Archived from the original on 22 June 2013. Retrieved 20 September 2020. <a href="https://web.archive.org/web/20130622155603/http://scholar.lib.vt.edu/theses/available/etd-12172003-122534/unrestricted/HurtonThesis.pdf" target="_blank">https://web.archive.org/web/20130622155603/http://scholar.lib.vt.edu/theses/available/etd-12172003-122534/unrestricted/HurtonThesis.pdf</a> <a href="#fnref:178" class="footnote-back-ref">↩</a></p></li> <li id="fn:179"><p>"Crash: A Tale of Two Species – The Benefits of Blue Blood – Nature – PBS". PBS. 10 June 2008. Archived from the original on 10 October 2008. Retrieved 31 August 2017. <a href="http://www.pbs.org/wnet/nature/crash-a-tale-of-two-species-the-benefits-of-blue-blood/595/" target="_blank">http://www.pbs.org/wnet/nature/crash-a-tale-of-two-species-the-benefits-of-blue-blood/595/</a> <a href="#fnref:179" class="footnote-back-ref">↩</a></p></li> <li id="fn:180"><p>Eisner, Chiara (10 June 2023). "Coastal biomedical labs are bleeding more horseshoe crabs with little accountability". NPR. Archived from the original on 10 June 2023. Retrieved 10 June 2023. <a href="https://www.npr.org/2023/06/10/1180761446/coastal-biomedical-labs-are-bleeding-more-horseshoe-crabs-with-little-accountabi" target="_blank">https://www.npr.org/2023/06/10/1180761446/coastal-biomedical-labs-are-bleeding-more-horseshoe-crabs-with-little-accountabi</a> <a href="#fnref:180" class="footnote-back-ref">↩</a></p></li> <li id="fn:181"><p>The Blood Harvest Archived 2014-07-24 at the Wayback Machine The Atlantic, 2014. <a href="https://www.theatlantic.com/technology/print/2014/02/the-blood-harvest/284078/" target="_blank">https://www.theatlantic.com/technology/print/2014/02/the-blood-harvest/284078/</a> <a href="#fnref:181" class="footnote-back-ref">↩</a></p></li> <li id="fn:182"><p>Carmichael RH, Botton ML, Shin PK, Cheung SG, eds. (2015). Changing Global Perspectives on Horseshoe Crab Biology, Conservation and Management. Springer International Publishing. <a href="#fnref:182" class="footnote-back-ref">↩</a></p></li> <li id="fn:183"><p>Chesler C. "Medical Labs May Be Killing Horseshoe Crabs". Scientific American. Archived from the original on 9 June 2016. Retrieved 10 May 2018. <a href="https://www.scientificamerican.com/article/medical-labs-may-be-killing-horseshoe-crabs/" target="_blank">https://www.scientificamerican.com/article/medical-labs-may-be-killing-horseshoe-crabs/</a> <a href="#fnref:183" class="footnote-back-ref">↩</a></p></li> <li id="fn:184"><p>Chesler C. "The Blood of the Crab". Popular Mechanics. No. 13 April 2017. Archived from the original on 4 May 2019. Retrieved 16 April 2017. <a href="http://www.popularmechanics.com/science/health/a26038/the-blood-of-the-crab/" target="_blank">http://www.popularmechanics.com/science/health/a26038/the-blood-of-the-crab/</a> <a href="#fnref:184" class="footnote-back-ref">↩</a></p></li> <li id="fn:185"><p>Eisner, Chiara (10 June 2023). "Coastal biomedical labs are bleeding more horseshoe crabs with little accountability". NPR. Archived from the original on 10 June 2023. Retrieved 10 June 2023. <a href="https://www.npr.org/2023/06/10/1180761446/coastal-biomedical-labs-are-bleeding-more-horseshoe-crabs-with-little-accountabi" target="_blank">https://www.npr.org/2023/06/10/1180761446/coastal-biomedical-labs-are-bleeding-more-horseshoe-crabs-with-little-accountabi</a> <a href="#fnref:185" class="footnote-back-ref">↩</a></p></li> <li id="fn:186"><p>Eisner, Chiara (10 June 2023). "Coastal biomedical labs are bleeding more horseshoe crabs with little accountability". NPR. Archived from the original on 10 June 2023. Retrieved 10 June 2023. <a href="https://www.npr.org/2023/06/10/1180761446/coastal-biomedical-labs-are-bleeding-more-horseshoe-crabs-with-little-accountabi" target="_blank">https://www.npr.org/2023/06/10/1180761446/coastal-biomedical-labs-are-bleeding-more-horseshoe-crabs-with-little-accountabi</a> <a href="#fnref:186" class="footnote-back-ref">↩</a></p></li> <li id="fn:187"><p>Anderson, Rebecca L.; Watson, Winsor H.; Chabot, Christopher C. (2013). "Sublethal Behavioral and Physiological Effects of the Biomedical Bleeding Process on the American Horseshoe Crab, Limulus polyphemus". The Biological Bulletin. 225 (3): 137–151. doi:10.1086/BBLv225n3p137. ISSN 0006-3185. PMC 4079546. PMID 24445440. <a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4079546" target="_blank">https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4079546</a> <a href="#fnref:187" class="footnote-back-ref">↩</a></p></li> <li id="fn:188"><p>"The Horseshoe Crab - US Fish and Wildlife Service" (PDF). Archived (PDF) from the original on 2 September 2020. Retrieved 10 July 2020. <a href="https://www.fws.gov/northeast/pdf/horseshoe.fs.pdf" target="_blank">https://www.fws.gov/northeast/pdf/horseshoe.fs.pdf</a> <a href="#fnref:188" class="footnote-back-ref">↩</a></p></li> <li id="fn:189"><p>"The Horseshoe Crab - US Fish and Wildlife Service" (PDF). Archived (PDF) from the original on 2 September 2020. Retrieved 10 July 2020. <a href="https://www.fws.gov/northeast/pdf/horseshoe.fs.pdf" target="_blank">https://www.fws.gov/northeast/pdf/horseshoe.fs.pdf</a> <a href="#fnref:189" class="footnote-back-ref">↩</a></p></li> <li id="fn:190"><p>Chesler C (9 June 2016). "Medical Labs May Be Killing Horseshoe Crabs". Scientific American. Archived from the original on 9 June 2016. Retrieved 3 November 2017. <a href="https://www.scientificamerican.com/article/medical-labs-may-be-killing-horseshoe-crabs/" target="_blank">https://www.scientificamerican.com/article/medical-labs-may-be-killing-horseshoe-crabs/</a> <a href="#fnref:190" class="footnote-back-ref">↩</a></p></li> <li id="fn:191"><p>Iwanaga S, Morita T, Miyata T, Nakamura T, Aketagawa J (1 August 1986). "The hemolymph coagulation system in invertebrate animals". Journal of Protein Chemistry. 5 (4): 255–268. doi:10.1007/bf01025424. ISSN 0277-8033. S2CID 84664449. <a href="/wiki/Doi_(identifier)" target="_blank">/wiki/Doi_(identifier)</a> <a href="#fnref:191" class="footnote-back-ref">↩</a></p></li> <li id="fn:192"><p>Iwanaga S, Morita T, Miyata T, Nakamura T, Aketagawa J (1 August 1986). "The hemolymph coagulation system in invertebrate animals". Journal of Protein Chemistry. 5 (4): 255–268. doi:10.1007/bf01025424. ISSN 0277-8033. S2CID 84664449. <a href="/wiki/Doi_(identifier)" target="_blank">/wiki/Doi_(identifier)</a> <a href="#fnref:192" class="footnote-back-ref">↩</a></p></li> <li id="fn:193"><p>"PyroGene : Licensing Success". National University of Singapore. 8 May 2003. Archived from the original on 14 May 2018. Retrieved 1 September 2018. <a href="https://web.archive.org/web/20180514164959/http://www.nus.edu.sg/ilo/news%26events/newsletter0312.html" target="_blank">https://web.archive.org/web/20180514164959/http://www.nus.edu.sg/ilo/news%26events/newsletter0312.html</a> <a href="#fnref:193" class="footnote-back-ref">↩</a></p></li> <li id="fn:194"><p>Eisner, Chiara (10 June 2023). "Coastal biomedical labs are bleeding more horseshoe crabs with little accountability". NPR. Archived from the original on 10 June 2023. Retrieved 10 June 2023. <a href="https://www.npr.org/2023/06/10/1180761446/coastal-biomedical-labs-are-bleeding-more-horseshoe-crabs-with-little-accountabi" target="_blank">https://www.npr.org/2023/06/10/1180761446/coastal-biomedical-labs-are-bleeding-more-horseshoe-crabs-with-little-accountabi</a> <a href="#fnref:194" class="footnote-back-ref">↩</a></p></li> <li id="fn:195"><p>Eisner, Chiara (10 June 2023). "Coastal biomedical labs are bleeding more horseshoe crabs with little accountability". NPR. Archived from the original on 10 June 2023. Retrieved 10 June 2023. <a href="https://www.npr.org/2023/06/10/1180761446/coastal-biomedical-labs-are-bleeding-more-horseshoe-crabs-with-little-accountabi" target="_blank">https://www.npr.org/2023/06/10/1180761446/coastal-biomedical-labs-are-bleeding-more-horseshoe-crabs-with-little-accountabi</a> <a href="#fnref:195" class="footnote-back-ref">↩</a></p></li> <li id="fn:196"><p>Eisner, Chiara (10 June 2023). "Coastal biomedical labs are bleeding more horseshoe crabs with little accountability". NPR. Archived from the original on 10 June 2023. Retrieved 10 June 2023. <a href="https://www.npr.org/2023/06/10/1180761446/coastal-biomedical-labs-are-bleeding-more-horseshoe-crabs-with-little-accountabi" target="_blank">https://www.npr.org/2023/06/10/1180761446/coastal-biomedical-labs-are-bleeding-more-horseshoe-crabs-with-little-accountabi</a> <a href="#fnref:196" class="footnote-back-ref">↩</a></p></li> <li id="fn:197"><p>Zhang S (9 May 2018). "The Last Days of the Blue-Blood Harvest". The Atlantic. Archived from the original on 8 September 2018. Retrieved 1 September 2018. <a href="https://www.theatlantic.com/science/archive/2018/05/blood-in-the-water/559229/" target="_blank">https://www.theatlantic.com/science/archive/2018/05/blood-in-the-water/559229/</a> <a href="#fnref:197" class="footnote-back-ref">↩</a></p></li> <li id="fn:198"><p>Pavid, Katie (3 December 2020). "Horseshoe crab blood: the miracle vaccine ingredient that's saved millions of lives". Natural History Museum. Retrieved 29 June 2024. <a href="https://www.nhm.ac.uk/discover/horseshoe-crab-blood-miracle-vaccine-ingredient.html" target="_blank">https://www.nhm.ac.uk/discover/horseshoe-crab-blood-miracle-vaccine-ingredient.html</a> <a href="#fnref:198" class="footnote-back-ref">↩</a></p></li> <li id="fn:199"><p>Iovenko, Chris (17 December 2021). "The fight to save horseshoe crabs from the biomedical industry". The Verge. Archived from the original on 18 December 2021. Retrieved 29 June 2024. <a href="https://www.theverge.com/2021/12/17/22840263/horseshoe-crab-blood-medical-industry-controversy" target="_blank">https://www.theverge.com/2021/12/17/22840263/horseshoe-crab-blood-medical-industry-controversy</a> <a href="#fnref:199" class="footnote-back-ref">↩</a></p></li> <li id="fn:200"><p>Eisner, Chiara (10 June 2023). "Coastal biomedical labs are bleeding more horseshoe crabs with little accountability". NPR. Archived from the original on 10 June 2023. Retrieved 10 June 2023. <a href="https://www.npr.org/2023/06/10/1180761446/coastal-biomedical-labs-are-bleeding-more-horseshoe-crabs-with-little-accountabi" target="_blank">https://www.npr.org/2023/06/10/1180761446/coastal-biomedical-labs-are-bleeding-more-horseshoe-crabs-with-little-accountabi</a> <a href="#fnref:200" class="footnote-back-ref">↩</a></p></li> <li id="fn:201"><p>"S. Rept. 116-110 - Agriculture, Rural Development, Food and Drug Administration, and Related Agencies Appropriations Bill, 2020". United States Congress. Archived from the original on 15 April 2020. Retrieved 18 January 2020. <a href="https://www.congress.gov/congressional-report/116th-congress/senate-report/110/1" target="_blank">https://www.congress.gov/congressional-report/116th-congress/senate-report/110/1</a> <a href="#fnref:201" class="footnote-back-ref">↩</a></p></li> <li id="fn:202"><p>"PETA Statement: U.S. Spending Bill". PETA. 20 December 2019. Archived from the original on 15 April 2020. Retrieved 18 January 2020. <a href="https://www.peta.org/media/news-releases/peta-statement-u-s-spending-bill/" target="_blank">https://www.peta.org/media/news-releases/peta-statement-u-s-spending-bill/</a> <a href="#fnref:202" class="footnote-back-ref">↩</a></p></li> <li id="fn:203"><p>Fox, Alex. "The Race for a Coronavirus Vaccine Runs on Horseshoe Crab Blood". Smithsonian Magazine. Archived from the original on 8 June 2020. Retrieved 9 June 2020. <a href="https://www.smithsonianmag.com/smart-news/race-coronavirus-vaccine-runs-horseshoe-crab-blood-180975048/" target="_blank">https://www.smithsonianmag.com/smart-news/race-coronavirus-vaccine-runs-horseshoe-crab-blood-180975048/</a> <a href="#fnref:203" class="footnote-back-ref">↩</a></p></li> <li id="fn:204"><p>"Drugs standards group nixes plan to kick pharma's crab blood habit". Reuters. 30 May 2020. Archived from the original on 9 June 2020. Retrieved 9 June 2020. <a href="https://www.reuters.com/article/us-lonza-crabs-idUSKBN2360MB" target="_blank">https://www.reuters.com/article/us-lonza-crabs-idUSKBN2360MB</a> <a href="#fnref:204" class="footnote-back-ref">↩</a></p></li> <li id="fn:205"><p>"Conservation". ERDG. Archived from the original on 9 May 2016. Retrieved 19 May 2016. <a href="http://www.horseshoecrab.org/con/con.html" target="_blank">http://www.horseshoecrab.org/con/con.html</a> <a href="#fnref:205" class="footnote-back-ref">↩</a></p></li> <li id="fn:206"><p>John A, Shin PK, Botton ML, Gauvry G, Cheung SG, Laurie K (1 January 2021). "Conservation of Asian horseshoe crabs on spotlight". Biodiversity and Conservation. 30 (1): 253–256. Bibcode:2021BiCon..30..253J. doi:10.1007/s10531-020-02078-3. PMC 7651794. PMID 33191986. <a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7651794" target="_blank">https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7651794</a> <a href="#fnref:206" class="footnote-back-ref">↩</a></p></li> <li id="fn:207"><p>John A, Shin PK, Botton ML, Gauvry G, Cheung SG, Laurie K (1 January 2021). "Conservation of Asian horseshoe crabs on spotlight". Biodiversity and Conservation. 30 (1): 253–256. Bibcode:2021BiCon..30..253J. doi:10.1007/s10531-020-02078-3. PMC 7651794. PMID 33191986. <a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7651794" target="_blank">https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7651794</a> <a href="#fnref:207" class="footnote-back-ref">↩</a></p></li> <li id="fn:208"><p>"Horseshoe crab business still a hit despite pandemic". The Star. 13 December 2020. Archived from the original on 23 April 2021. Retrieved 18 July 2021. <a href="https://www.thestar.com.my/news/nation/2020/12/13/horseshoe-crab-business-still-a-hit-despite-pandemic" target="_blank">https://www.thestar.com.my/news/nation/2020/12/13/horseshoe-crab-business-still-a-hit-despite-pandemic</a> <a href="#fnref:208" class="footnote-back-ref">↩</a></p></li> <li id="fn:209"><p>"Horseshoe crab business still a hit despite pandemic". The Star. 13 December 2020. Archived from the original on 23 April 2021. Retrieved 18 July 2021. <a href="https://www.thestar.com.my/news/nation/2020/12/13/horseshoe-crab-business-still-a-hit-despite-pandemic" target="_blank">https://www.thestar.com.my/news/nation/2020/12/13/horseshoe-crab-business-still-a-hit-despite-pandemic</a> <a href="#fnref:209" class="footnote-back-ref">↩</a></p></li> <li id="fn:210"><p>"Red knots get to feast on horseshoe crab eggs". Environment News Service. 26 March 2008. Archived from the original on 24 September 2015. Retrieved 19 January 2011. <a href="http://www.ens-newswire.com/ens/mar2008/2008-03-26-093.html" target="_blank">http://www.ens-newswire.com/ens/mar2008/2008-03-26-093.html</a> <a href="#fnref:210" class="footnote-back-ref">↩</a></p></li> <li id="fn:211"><p>"Critter Class Hodge Podge (Horseshoe crabs and Wooly Bears)" (PDF). The Wildlife Center. 26 October 2011. Archived (PDF) from the original on 2 April 2015. Retrieved 9 March 2015. <a href="http://wildlifecenter.org/sites/default/files/cam_archives/26OCT_Hodge-Podge.pdf" target="_blank">http://wildlifecenter.org/sites/default/files/cam_archives/26OCT_Hodge-Podge.pdf</a> <a href="#fnref:211" class="footnote-back-ref">↩</a></p></li> <li id="fn:212"><p>Whittle, Patrick (10 August 2023). "Harvest of horseshoe crabs, needed for blue blood, stopped during spawning season in national refuge". AP News. Archived from the original on 12 August 2023. Retrieved 12 August 2023. <a href="https://apnews.com/article/horseshoe-crab-blood-harvest-shutdown-refuge-1838caabdbd94d0d80a0c67f74a01caf" target="_blank">https://apnews.com/article/horseshoe-crab-blood-harvest-shutdown-refuge-1838caabdbd94d0d80a0c67f74a01caf</a> <a href="#fnref:212" class="footnote-back-ref">↩</a></p></li> <li id="fn:213"><p>Whittle, Patrick (10 August 2023). "Harvest of horseshoe crabs, needed for blue blood, stopped during spawning season in national refuge". AP News. Archived from the original on 12 August 2023. Retrieved 12 August 2023. <a href="https://apnews.com/article/horseshoe-crab-blood-harvest-shutdown-refuge-1838caabdbd94d0d80a0c67f74a01caf" target="_blank">https://apnews.com/article/horseshoe-crab-blood-harvest-shutdown-refuge-1838caabdbd94d0d80a0c67f74a01caf</a> <a href="#fnref:213" class="footnote-back-ref">↩</a></p></li> <li id="fn:214"><p>Whittle, Patrick (10 August 2023). "Harvest of horseshoe crabs, needed for blue blood, stopped during spawning season in national refuge". AP News. Archived from the original on 12 August 2023. Retrieved 12 August 2023. <a href="https://apnews.com/article/horseshoe-crab-blood-harvest-shutdown-refuge-1838caabdbd94d0d80a0c67f74a01caf" target="_blank">https://apnews.com/article/horseshoe-crab-blood-harvest-shutdown-refuge-1838caabdbd94d0d80a0c67f74a01caf</a> <a href="#fnref:214" class="footnote-back-ref">↩</a></p></li> </ol>