Chemical defense in tropical green algae, order Caulerpales

Forty marine algae of the order Caulerpales were chemically investigated. Virtually all produce toxic secondary metabolites of a unique and unprecedented class. These metabolites are generally Linear terpenoids, but unusual structural features such as aldehydes and bis-enol acetate functional groups make these compounds uruque. The conlpounds are tonc or deterrent toward microorganisms, sea urchin larvae, and herbivous fishes, and when incorporated into diets at naturally occurring concentrations cause mortality in juvenile conch. Concentrations of bioactive metabolites were found to show httle variation in different plant parts such as blades, shpes and holdfasts. Young growlng tips and reproductive structures contained higher concentrahons than mature plant tissues on a dry weight and ash-free dry weight basis. Chemical variation, both qualitahve and quantitative, was observed in different populations of the same species. In the cases examined, algae growing in areas known to have the highest herbivory produced the greatest concentrations and varieties of secondary metabolites. Based upon these observations and pnor feeding preference data, we conclude that chemical defense IS a major factor In the sumval of marine algae within this order.