A group of mollusks which includes the sea slugs and sea hares. They have a small or absent shell and are typically brightly colored with conspicuous external gills.
Subclass Opisthobranchia, class Gastropoda‘The latter group includes radically modified animals, the Opisthobranchia and Pulmonata, which undergo detorsion and essentially re-evolve bilateral symmetry.’
- ‘In fact, as with the Opisthobranchia, shell reduction has occurred independently a number of times in different lineages.’
- ‘However, as with Tritonia, many other members of the subclass Opisthobranchia also exhibit swimming behavior.’
- ‘In the traditional classification system, the class Gastropoda has been divided into three subclasses, Prosobranchia, Pulmonata, and Opisthobranchia.’
- ‘The differences in protoconch shape may prove insufficient to differentiate Allogastropoda and shell-bearing Opisthobranchia.’
Modern Latin (plural), from opistho-‘to the rear’ + brankhia ‘gills’.