POSTINGESTIVE CONSEQUENCES OF CONSUMING SECONDARY METABOLITES IN SEA HARES (GASTROPODA, OPISTHOBRANCHIA)

Secondary metabolites of plants and animals often deter feeding by pot ential consumers; whether they also have negative post-ingestive conse quences is debated, We fed three secondary metabolites to the sea hare Aplysia juliana and two to A, kurodai, at approximately 1% of the dry mass of their diet, Luffariellolide, a sponge secondary metabolite, a nd malyngamide B, a cyanophyte metabolite, significantly reduced the g rowth of Aplysia juliana; pachydictyol A, a brown algal metabolite, ha d no effect on growth, Previous studies have shown that blood-glucose concentrations of sea hares are affected by many types of stress, Bloo d-glucose concentrations of Aplysia juliana were affected by secondary metabolites in the diet; however, this effect was not correlated with the toxicity (effect on growth) of the metabolites, Aplysia juliana s equestered pachydictyol A and malyngamide B in the digestive gland at c. 1.5% dry mass, an order of magnitude higher than luffariellolide. P atterns of growth of Aplysia kurodai fed luffariellolide and pachydict yol A were similar to those of Aplysia juliana, but were not statistic ally significant, Blood-glucose concentrations of Aplysia kurodai were not significantly affected by secondary metabolites, Aplysia kurodni sequestered pachydictyol A and luffariellolide at similar concentratio ns, as did Aplysia juliana. We conclude that some secondary metabolite s may reduce the growth of sea hares, but that blood-glucose concentra tions offer little prospect for use as an indicator of this stress.