Opisthobranch Overview 

 What Is An Opisthobranch

           An opisthobranch is marine gastropod characterized by two pairs of oral tentacles, horn-like olfactory organs called 
        rhinophores, and significantly reduced or absent shell and no operculum.  They are hermaphroditic and most have 
        highly specialized diets. Most are benthic and occur in the intertidal and subtidal zones. Individuals within 
        Opisthobranchia are commonly called sea slugs, sea hares, bubble shells, dorids, sea angels, and sea butterflies.   

        Currently, the phylogeny within Opisthobrancia is under review; 
        however, one system breaks the subclass into seven orders.
        Opisthobranchs utilize several methods of defense, including camouflage, 
        warning coloration, behavioral strategies, and chemical defense.  
        Some nudibranchs even incorporate nematocysts from from their prey 
        into their bodies.  Although not necessarily a defensive mechanism,
        they are known to regenerate missing body parts as well.      
        The anatomy of opisthobranchs varies among the diferent orders and 
        species.  Nudibranchs most commonly occur in to variations of two basic
        forms.  Below are two schematics characterizing the two most commonly
        regarded nudibranch forms.   Cerata are dorsal projections which may house the digestive organ, act as a respiratory 
        organ, and contain stolen nematocysts.   Rhinophores are sensory organs used in navigation and feeding.  Tubercles
        are small bumps on the dorsal surface.  A branchial plume is a respiratory organ.

        For more information about nudibranchs or other opisthobranchs, please visit the references and links page for a 
        list of books and web sites containing pertinent information.                                                                                      .  


Class: Gastropoda
Subclass: Opisthobranchia
Order: Cephalaspidea
This webpage is part of the UWT Marine Ecology 2008 Class Project.      Created June 06, 2008 by Sarah Mangum