A METAMORPHIC INDUCER IN THE OPISTHOBRANCH HAMINAEA-CALLIDEGENITA - PARTIAL-PURIFICATION AND BIOLOGICAL-ACTIVITY

Larvae of Haminaea callidegenita (Mollusca:Cephalaspidea) were induced to metamorphose by a compound found in the gelatinous matrix composin g most of the egg mass. A functionally similar compound isolated from adult tissue also induced metamorphosis in H. callidegenita larvae. Op isthobranchs are frequently induced to metamorphose by a specific prey item or a substrate characteristic of the adult habitat, but this is the first known instance of metamorphosis occurring in response to a c ompound produced by adult conspecifics. The inducer was purified from egg mass jelly (EMJ) by high pressure liquid chromatography (HPLC) and was found to be smaller than 1000 Da, polar, non-proteinaceous, and v ery stable. We isolated a compound of identical activity from egg mass es produced by four other opisthobranch species, suggesting that the s ame or chemically similar compounds are intrinsic to opisthobranch egg masses. However, only H. callidegenita larvae metamorphosed in respon se to EMJ. Competent larvae of five other mollusc species did not resp ond to the partially purified EMJ inducer but did respond to a specifi c substrate associated with each species. The presence of the inducer within the egg mass causes an unusual developmental pattern in H. call idegenita, a poecilogonous species that produces both swimming veliger and crawling juvenile offspring.