opisthobranch

== English == === Etymology === From opistho- +‎ branchia. === Pronunciation === IPA(key): /ɵˈpɪsθəbɹæŋk/ === Noun === opisthobranch (plural opisthobranchs) (zoology) A gastropod with gills behind the heart, formerly thought to belong to a single group. ==== Derived terms ==== === Adjective === opisthobranch (not comparable) (of gills) Placed behind the heart. Antonym: prosobranch (of a gastropod) Having gills placed behind the heart. Antonym: prosobranch