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[uh-pis-thuh-brangk] /əˈpɪs θəˌbræŋk/
any gastropod mollusk of the order Opisthobranchia, as the sea slugs, sea butterflies, and sea hares, characterized by a vestigial or absent mantle and shell and two pairs of tentacles.
of or relating to the opisthobranches.
Also, opisthobranchiate
[uh-pis-thuh-brang-kee-it, -eyt] /əˌpɪs θəˈbræŋ ki ɪt, -ˌeɪt/ (Show IPA)
1850-55; < New Latin Opisthobranchia the subclass; see opistho-, branchia Unabridged
Based on the Random House Dictionary, © Random House, Inc. 2015.
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Examples from the web for opisthobranch
  • Natural products of opisthobranch molluscs: a biological review.
British Dictionary definitions for opisthobranch


any marine gastropod of the class Opisthobranchia (or Opisthobranchiata), in which the shell is reduced or absent: includes the pteropods, sea hares, and nudibranchs
Word Origin
via New Latin from Greek opisthen behind + -branch
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition
© William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins
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Encyclopedia Article for opisthobranch

any marine gastropod of the approximately 2,000 species of the subclass Opisthobranchia. These gastropods, sometimes called sea slugs, breathe either through gills, which are located behind the heart, or through the body surface. The shell and mantle cavity are reduced or lacking. Larval asymmetry may give way to bilateral symmetry in the adult through a partial untwisting of the embryonic viscera. Reproduction is hermaphroditic-i.e., both male and female reproductive organs occur in one individual.

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Encyclopedia Britannica, 2008. Encyclopedia Britannica Online.
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