opisthobranch /ɵˈpɪsθəbɹæŋk/adjective 2noun 1forms 1 adjective2 •Placed behind the heart. •Having gills placed behind the heart.For example, the antitumour depsipeptide kahalalide F was isolated from the opisthobranch mollusc Elysia rufescens, and is used by both the mollusc and its dietary alga Bryopsis spp. — 2016 noun1 •A gastropod with gills behind the heart, formerly thought to belong to a single group. formsopisthobranchs
