Worms are diverse bilateral animals characterized by long cylindrical bodies without limbs or usually eyes. They range from microscopic sizes to over 58 meters, like the marine nemertean Lineus longissimus, and include species such as the African giant earthworm Microchaetus rappi. While many worms occupy parasitic niches inside other animals, free-living worms inhabit marine, freshwater, or underground environments. Historically classified under the obsolete taxon Vermes by Linnaeus, worms include various invertebrates such as annelids, nematodes, and flatworms, as well as some legless vertebrates like slowworms. The term "helminth" commonly refers to parasitic roundworms and tapeworms in medicine.
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Further information: Vermes and Animal § History of classification
In taxonomy, "worm" refers to an obsolete grouping, Vermes, used by Carl Linnaeus and Jean-Baptiste Lamarck for all non-arthropod invertebrate animals, now seen to be polyphyletic. In 1758, Linnaeus created the first hierarchical classification in his Systema Naturae.4 In his original scheme, the animals were one of three kingdoms, divided into the classes of Vermes, Insecta, Pisces, Amphibia, Aves, and Mammalia. Since then the last four have all been subsumed into a single phylum, the Chordata, while his Insecta (which included the crustaceans and arachnids) and Vermes have been renamed or broken up. The process was begun in 1793 by Lamarck, who called the Vermes une espèce de chaos (a sort of chaos)5 and split the group into three new phyla, worms, echinoderms, and polyps (which contained corals and jellyfish). By 1809, in his Philosophie Zoologique, Lamarck had created 9 phyla apart from vertebrates (where he still had 4 phyla: mammals, birds, reptiles, and fish) and molluscs, namely cirripedes, annelids, crustaceans, arachnids, insects, worms, radiates, polyps, and infusorians.6 Chordates are remarkably wormlike by ancestry.7
Informal grouping
In the 13th century, worms were recognized in Europe as part of the category of reptiles that consisted of a miscellany of egg-laying creatures, including "snakes, various fantastic monsters, lizards, assorted amphibians", as recorded by Vincent of Beauvais in his Mirror of Nature.8 In everyday language, the term worm is also applied to various other living forms such as larvae, insects, millipedes, centipedes, shipworms (teredo worms), or even some vertebrates (creatures with a backbone) such as blindworms and caecilians. Worms include several groups. The three main phyla are:
- Platyhelminthes, includes the flatworms, tapeworms, and flukes. They have a flat, ribbon- or leaf-shaped body with a pair of eyes at the front. Some are parasites.
- Nematoda, contains the threadworms, hookworms and other roundworms. Threadworms may be microscopic, such as the vinegar eelworm, or more than 1-metre (3 feet) long. They are found in damp earth, moss, decaying substances, fresh water, or salt water. Some roundworms are also parasites: the Guinea worm, for example, gets under the skin of the feet and legs of people living in tropical countries.
- Annelida, consists of the segmented worms, with bodies divided into segments or rings. Among these worms are the earthworms and the bristle worms of the sea.
Familiar worms include the earthworms, members of phylum Annelida. Other invertebrate groups may be called worms, especially colloquially. In particular, many unrelated insect larvae are called "worms", such as the railroad worm, woodworm, glowworm, bloodworm, butterworm, inchworm, mealworm, silkworm, and woolly bear worm.
Worms may also be called helminths, particularly in medical terminology when referring to parasitic worms, especially the Nematoda (roundworms) and Cestoda (tapeworms). Hence, "helminthology" is the study of parasitic worms. When a human or an animal, such as a dog or horse, is said to "have worms", it means that it is infested with parasitic worms, typically roundworms or tapeworms. Deworming is a method to kill off the worms that have infected a human or animal by giving anthelmintic drugs.
"Ringworm" is not a worm at all, but a skin fungus.
Lobopodians are an informal grouping of extinct panarthropods from the Cambrian to the Carboniferous that are often called worms or "worm-like animals" despite having had legs in the form of stubby lobopods. Likewise, the extant Onychophora are sometimes called velvet worms despite possessing stubby legs.
Society and culture
See also: List of fictional worms and Fictional depictions of worms
Wyrm was the Old English term for carnivorous reptiles ("serpents") and mythical dragons. "Worm" has also been used as a pejorative epithet to describe a cowardly, weak or pitiable person.
Worms can also be farmed for the production of nutrient-rich vermicompost.
See also
- Helminthology
- Nematology
- Sea worm, lists various types of marine worms
- Worm cast
- Worm charming
- Vermeology
Explanatory notes
References
"Cornwall – Nature – Superstar Worm". BBC. 7 April 2009. https://www.bbc.co.uk/cornwall/content/articles/2009/04/07/nature_worm_feature.shtml ↩
"Worm Digest - The Mighty Worm". 2 October 2005. Archived from the original on 19 February 2009.; https://web.archive.org/web/20090219141951/http://www.wormdigest.org/index.php?option=com_content&task=view&id=102&Itemid=2 ↩
Carwardine, Mark (1995). The Guinness book of animal records. Enfield: Guinness Publishing. p. 232. ISBN 978-0851126586. 978-0851126586 ↩
Linnaeus, Carl (1758). Systema naturae per regna tria naturae: secundum classes, ordines, genera, species, cum characteribus, differentiis, synonymis, locis (in Latin) (10th ed.). Holmiae (Laurentii Salvii). Archived from the original on 10 October 2008. Retrieved 22 September 2008. /wiki/Carl_Linnaeus ↩
The prefix une espèce de is pejorative.[5] ↩
Gould, Stephen Jay (2011). The Lying Stones of Marrakech. Harvard University Press. pp. 130–134. ISBN 978-0-674-06167-5. 978-0-674-06167-5 ↩
Brown, Federico D.; Prendergast, Andrew; Swalla, Billie J. (2008). "Man is but a worm: Chordate origins". Genesis. 46 (11): 605–613. doi:10.1002/dvg.20471. PMID 19003926. https://doi.org/10.1002%2Fdvg.20471 ↩
Franklin-Brown, Mary (2012). Reading the world: encyclopedic writing in the scholastic age. Chicago London: The University of Chicago Press. p. 223;377. ISBN 9780226260709. 9780226260709 ↩