Palatability of invertebrate larvae to corals and sea anemones

Risk of larval mortality is an underlying theme in debates and models concerning the ecology and evolution of the differing reproductive characteristics among marine benthic invertebrates. In these discussions, predation is often assumed to be a major source of larval mortality. Previous studies, focused primarily on planktotrophic larvae, suggested that marine larvae generally were susceptible to, and poorly defended against, planktivorous fishes and invertebrates. Larval-planktivore interactions involving larger and more conspicuous lecithotrophic larvae that are typical of many brooding sessile invertebrates have not been well studied. This lack of data for diverse larval types has hindered testing broad generalities about marine larvae and planktivore prey-preferences. This study demonstrates that lecithotrophic larvae of many Caribbean and temperate western Atlantic invertebrates are distasteful to co-occurring corals and anemones. These larval predators frequently rejected larvae of sponges (6 of 9 species), gorgonians (7 of 9 species), corals (3 of 3 species), hydroids (2 of 2 species) and a bryozoan. Larvae of three temperate colonial ascidians were readily consumed. Frequencies of survivorship for larvae captured but rejected by corals and anemones were generally high and, in 20 of 24 assays, were not statistically different from those of unattacked control larvae. Levels of metamorphosis (when it occurred) of rejected larvae also rarely differed significantly from those of unattacked controls. These results provide further evidence that larval palatability to predators may not be as high as once thought, particularly for brooded larvae of sessile colonial invertebrates. The means by which larvae may avoid or deter predators, and the demographic consequences for marine invertebrates and for the evolution of invertebrate life-history patterns, need to be assessed.