sea spider

sea spider
any member of the arthropod class Pycnogonida, marine invertebrates with eight long walking legs attached to a small body consisting of a cephalothorax and vestigial abdomen.

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▪ Pycnogonida
also called  Pycnogonid,  

      any of the spiderlike marine animals comprising the class Pycnogonida (also called Pantopoda) of the phylum Arthropoda. Sea spiders walk about on the ocean bottom on their slender legs or crawl among plants and animals; some may tread water.

      Most pycnogonids have four pairs of long legs attached to four trunk segments. The body size ranges from 3 millimetres (1/8 inch) in tropical shallow-water species to 50 centimetres (20 inches) in deepwater species. The mouth, a triangular opening at the end of an elaborate suctorial appendage (proboscis), is often longer and larger than the body. Adult pycnogonids either suck the juices from soft-bodied invertebrates or browse on hydroids (phylum Cnidaria) and bryozoans. The four simple eyes are often lacking in the deepwater species. The digestive and reproductive systems have branches that go to the legs.

      Sexes are separate, and fertilization is apparently external. The males carry the eggs on a special pair of legs until they hatch. Many species have larval or juvenile stages that are parasitic in cnidarians or mollusks, but they are not important economically. Nervous and circulatory systems are simple, and there are apparently no respiratory or excretory systems.

      Classification within the group is based on the presence or absence of various anterior appendages. There are no clear ordinal divisions within the living genera, which are grouped in about a dozen families. There are more than 600 described living species and at least one fossil species from the Jurassic Period (about 136,000,000 to 190,000,000 years ago).

      Pycnogonids are sometimes also called whip scorpions.

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Universalium. 2010.

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Look at other dictionaries:

  • Sea spider — Sea spi der (Zo[ o]l.) (a) Any maioid crab; a spider crab. See {Maioid}, and {Spider crab}, under {Spider}. (b) Any pycnogonid. [1913 Webster] …   The Collaborative International Dictionary of English

  • sea spider — n. PYCNOGONID …   English World dictionary

  • Sea spider — Taxobox name = Sea spiders image width = 250px regnum = Animalia phylum = Arthropoda subphylum = Chelicerata classis = Pycnogonida ordo = Pantopoda classis authority = Latreille, 1810 subdivision ranks = Families subdivision = Ammotheidae… …   Wikipedia

  • sea spider — sea′ spi der n. ivt any marine arthropod of the class Pycnogonida, having a short, slender body and four to six pairs of long legs • Etymology: 1660–70 …   From formal English to slang

  • sea spider — noun Date: 1855 any of various small long legged marine arthropods (class Pycnogonida) that superficially resemble spiders …   New Collegiate Dictionary

  • sea spider — noun Any arthropod in the taxonomic class Pycnogonida …   Wiktionary

  • sea spider — /ˈsi spaɪdə/ (say see spuyduh) noun a slender, carnivorous, marine, eight legged arthropod, as Pycnogonum littorale of northern African coasts …  

  • sea spider — noun any of various small spiderlike marine arthropods having small thin bodies and long slender legs • Syn: ↑pycnogonid • Hypernyms: ↑arthropod • Member Holonyms: ↑Pycnogonida, ↑order Pycnogonida …   Useful english dictionary

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  • spider — noun 1》 an eight legged predatory arachnid with an unsegmented body consisting of a fused head and thorax and a rounded abdomen, most kinds of which spin webs in which to capture insects. [Order Araneae.]     ↘used in names of other arachnids,… …   English new terms dictionary

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