Home Acknowledgments Conventions Glossary Maps References Links Articles Thumbnails Species list	Opisthobranchia The subclass Opisthobranchia includes gastropod mollusks that have bilateral symmetry and a tendency toward reduction or loss of the shell. There are nine orders that have been found in Hawaiian waters: Acteonoidea, Cephalaspidea, Thecosomata, Gymnosomata, Anaspidea, Sacoglossa, Tylodinoidea, Pleurobranchomorpha and Nudibranchia. Two orders, the Acochlidea and Rhodopemorpha, have not been recorded from Hawaii. However, they include small worm-like species that live interstitially in sand or in algal turf so could easily have been missed. For the number of known species in each group see: table. Acteonoidea Cephalaspidea Thecosomata no photo available Gymnosomata Anaspidea Sacoglossa Tylodinoidea Pleurobranchomorpha Nudibranchia Order Nudibranchia The order Nudibranchia includes species that lack shells and have various forms of secondary gills. All are carnivores. It is divided into four suborders: Doridacea, Dendronotacea, Arminacea, and Aeolidacea. Hawaiian nudibranchs represent about 57% of the opisthobranch species found in the islands. Doridacea Dendronotacea Arminacea Aeolidacea To display thumbnail images of all the Hawaiian sea slugs on one page for quick identification, click here. ___________________________________________ Opisthobranch Look-alikes Several other taxa are often mistaken for opisthobranchs. The following links provide a brief treatment of the most common as an aid to identification. sea cucumbers flatworms velutinids cowries & relatives onchidiids galeommatids benthic ctenophores polychaetes ___________________________________________ Opisthobranch relatives Several families usually listed as prosobranchs and currently placed in the lower Heterobranchia (previously Heterostropha) have been considered part of the Opisthobranchia or closely related to them in the past. The following links provide a brief treatment of some of these families. Pyramidellidae Architectonicidae, etc
	Thumbnails Species list Top