The role of choline in metamorphic induction of Phestilla (Gastropoda, Nudibranchia)

Abstract

1. Larval metamorphosis in the nudibranch Phestilla sibogae occurs within 24 hr of exposure to an extract of their coral prey or after 2–3 days of exposure to choline chloride; the percentage response of groups of larvae is dose-dependent with both metamorphic inducers. 2. If precompetent larvae are continuously exposed to coral extract, they habituate and do not metamorphose when competent; this does not occur in response to choline. 3. Larvae habituated to coral inducer can still metamorphose in response to choline; exposure to choline prior to competence does not interfere with coral-extract induction. 4. No synergism occurs between low concentrations of the two inductive agents. 5. We conclude: (a) the sites of action of the two metamorphic inducers are different; (b) the receptor for the coral product is present before competence, but the process involving choline arises at about the time of competence; (c) the role of choline probably lies in the neurological events of metamorphic activation.