Chemical defence of the mediterranean alga Caulerpa taxifolia: variations in caulerpenyne production

Caulerpenyne (Cyn) is the major secondary metabolite involved in the chemical defence of Caulerpa taxifolia. A fast chromatography technique for Cyn quantification in algal samples of fronds and stolons collected monthly at Cap Martin (France), from depth of 5–30 m, is reported. Temperature influenced Cyn production in this alga of subtropical origin and the maximum concentration was in fronds at 5 m depth in summer period when the water temperature rose above 19°C. The amount of Cyn decreased at increasing depths and Cyn concentrations were always higher in fronds than in stolons. Variations in Cyn concentration explained seasonal changes in (1) feeding behaviour of the sea urchin Paracentrotus lividus and (2) biomass of fouling organisms of C. taxifolia. Tropical strains of this alga always contain less Cyn than the mediterranean strain. Geographical, seasonal, depth and intraplant variations of Cyn concentrations are discussed versus influences of biotic and abiotic factors.