Chemical and structural defenses of Caribbean gorgonians {Pseudoptero-gorgia spp.)- I- Development of an in situ feeding assay

Abstract

An in situ method was developed to assess the deterrent effects of various bioactive terpenes and calcitic sclerites which are hypothesized to function as chemical and structural defenses in gorgonian corals. Assays on coral reefs demonstrated that the crude lipid extracts of the Caribbean gorgonians Pseudopterogorgia acerosa and P. rigida, as well as the purified terpenoids curcuhydroquinone and curcuquinone from P. ngida, deterred natural predators at concentrations below their normal levels in gorgonian tissues. Assays conducted with purified sclerites from P. acerosa showed that the sclerites, alone, also function effectively to reduce predation on otherwise palatable foods. This in situ bioassay allows for precise dosage control and its utility in separating chemlcal and structural aspects of defense is demonstrated.