Differential predation on marine invertebrate larvae by two benthic predators

Planktotrophic larvae of polychaetes, echinoids, asteroids, gastropods and cirripeds were preyed upon differentially in the laboratory by 2 filter-feeding benthic predators, the ascidian Styela gibbsii and the mussel Mytilus edulis. Differences in predation rate are attributed in part to larval defense mechanisms. Presumed structural defenses (veliger shell, naupliar spines, trochophore setae) were ineffective against the predators investigated. Echinoderm larvae, which had no apparent structural defenses, had the highest survival. S. gibbsii displayed a higher frequency of siphon closure when exposed to echinopluteus larva homogenate than in seawater controls. This is considered preliminary evidence for chemical defense mechanisms possessed by these larvae.