any small marine invertebrate of the class Pterobranchia (phylum Hemichordata). Pterobranchs are found mainly in the Southern Hemisphere, but a few species occur in northern waters. The pterobranch body, like that of the related acorn worm (q.v.), can be divided into three regions: a proboscis (i.e., a tubular sucking organ); a collar with tentacles used to filter food, usually small planktonic plants and animals, from the surrounding water; and a trunk containing a U-shaped gut. There are three genera of pterobranchs. Two of them, Rhabdopleura and Cephalodiscus, live in secreted tubes, organized into a colonial structure called a coenecium. The third genus, Atubaria, lives on hydroids. All three genera are rare. About 21 species have been described.

      Most species form colonies of genetically identical individuals (called zooids) that arise from asexual budding. Pterobranchs may be descended from extinct marine animals called graptolites, a group that flourished in the oceans roughly 300 million to 500 million years ago.

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Universalium. 2010.

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  • pterobranch — [ tɛrə(ʊ)braŋk] noun Zoology a minute tube dwelling colonial acorn worm of a class (Pterobranchia) found chiefly in deep water …   English new terms dictionary

  • pterobranch — ptero·branch …   English syllables

  • pterobranch — ˈterəˌbraŋk noun ( s) Etymology: New Latin Pterobranchia : a member of the order Pterobranchia …   Useful english dictionary

  • Graptolite — Taxobox name = Graptolites fossil range = fossil range|510|350Mid Cambrian to Lower Carboniferous image width = 260px image caption = Fossil graptolite Tetragraptus fruticosus from the Ordovician of Australia regnum = Animalia phylum =… …   Wikipedia

  • hemichordate — /hem i kawr dayt/, Zool. adj. 1. belonging or pertaining to the chordates of the phylum Hemichordata, comprising small, widely distributed, marine animals, as the acorn worms. n. 2. a hemichordate animal, having a vertebratelike hollow nerve cord …   Universalium

  • Chordate — Chordata Temporal range: Early Cambrian – Recent, 540–0 Ma …   Wikipedia

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  • Hemichordaten — Kiemenlochtiere Eichelwurm (Saccoglossus sp.) Systematik Reich: Tiere (Animalia) Unterreich …   Deutsch Wikipedia

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