PUKALIDE, A WIDELY DISTRIBUTED OCTOCORAL DITERPENOID, INDUCES VOMITING IN FISH

Tissue and extractable metabolites from the subtropical gorgonian Lept ogorgia virgulata (Coelenterata: Anthozoa: Octocorallia: Gorgonacea) i nduce vomiting in a variety of fish species. To elucidate the chemical bases of this phenomenon, experiments were undertaken with purified p ukalide, a cembranoid diterpene that comprises as much as 0. 1-0. 5% o f the wet tissue weight of L. virgulata. When incorporated into artifi cial foods at concentrations corresponding to the levels found in L. v irgulata, pukalide induced emesis when delivered orally to killifish ( Fundulus heteroclitus). The threshold dose for pukalide-induced emesis was 0.05 mg/g fish body weight. Control pellets devoid of pukalide di d not induce vomiting. The emetic effect of pukalide was dose-dependen t, as fish ingesting more than 0. 100 mg pukalide/g body weight exhibi ted a significantly higher incidence of vomiting than fish ingesting l ower doses of pukalide (G = 5.5, df = 1, P < 0. 025). The elapsed time between ingestion of pukalide-containing pellets and emesis was signi ficantly longer in fish that ingested marginally emetic doses of pukal ide (Kruskal-allis H = 4.00, significant with P < 0.05). Although not markedly unpalatable to fish, pukalide may function in nature as a def ensive toxin by inducing emesis and learned aversion in potential octo coral predators.