Tunicate

A tunicate is an exclusively marine <a href="/facts/Invertebrate/3CyqCVnN">invertebrate</a> animal, a member of the <a href="/facts/Subphylum/TQopDJJ5">subphylum</a> Tunicata . This grouping is part of the <a href="/facts/Chordata/AldL6ARm">Chordata</a>, a <a href="/facts/Phylum/ELT3Jyax">phylum</a> which includes all animals with <a href="/facts/Dorsal_nerve_cord/Ko6h3gqM">dorsal nerve cords</a> and <a href="/facts/Notochord/wvmmQPj1">notochords</a> (including <a href="/facts/Vertebrates/tT54FSTT">vertebrates</a>). The subphylum was at one time called Urochordata, and the term urochordates is still sometimes used for these animals.
Despite their simple appearance and very different adult form, their close relationship to the vertebrates is certain. Both groups are chordates, as evidenced by the fact that during their mobile larval stage, tunicates possess a <a href="/facts/Notochord/wvmmQPj1">notochord</a>, a hollow <a href="/facts/Dorsal_nerve_cord/Ko6h3gqM">dorsal nerve cord</a>, <a href="/facts/Pharyngeal_slit/fTR32SUN">pharyngeal slits</a>, post-anal tail, and an <a href="/facts/Endostyle/l8E7q1EW">endostyle</a>. They resemble a <a href="/facts/Tadpole/GFl3NasU">tadpole</a>.
Tunicates are the only chordates that have lost their <a href="/facts/Myomere/lnLb2k09">myomeric</a> segmentation, with the possible exception of the seriation of the gill slits. However, <a href="/facts/Doliolida/I0Gx70wW">doliolids</a> still display segmentation of the muscle bands.
Some tunicates live as solitary individuals, but others replicate by <a href="/facts/Budding/TEB3zXxB">budding</a> and become <a href="/facts/Colony_(biology)/b5QfltwY">colonies</a>, each unit being known as a <a href="/facts/Zooid/c3cJ1zeT">zooid</a>. They are marine <a href="/facts/Filter_feeder/hmVLwWB5">filter feeders</a> with a water-filled, sac-like body structure and two tubular openings, known as siphons, through which they draw in and expel water. During their <a href="/facts/Aquatic_respiration/9AxdMGnc">respiration</a> and feeding, they take in water through the incurrent (or inhalant) siphon and expel the filtered water through the excurrent (or exhalant) siphon. Adult ascidian tunicates are <a href="/facts/Sessility_(zoology)/f0xV4VV1">sessile</a>, immobile and permanently attached to rocks or other hard surfaces on the ocean floor. <a href="/facts/Thaliacea/a1Sd47DL">Thaliaceans</a> (pyrosomes, doliolids, and salps) and <a href="/facts/Larvacean/q1S7DWcT">larvaceans</a> on the other hand, swim in the <a href="/facts/Pelagic_zone/D6heJr5f">pelagic zone</a> of the sea as adults.
Various species of <a href="/facts/Ascidiacea/Vkqqavut">ascidians</a>, the most well-known class of tunicates, are commonly known as <a href="/facts/Sea_squirt/Vkqqavut">sea squirts</a>, sea pork, sea livers, or <a href="/facts/Sea_tulip/9cloDDk0">sea tulips</a>.
The earliest probable species of tunicate appears in the fossil record in the early <a href="/facts/Cambrian_period/jIfzKtod">Cambrian period</a>.

Tunicate open-in-new

Tunicate