Meeting Abstract

P2.81  Wednesday, Jan. 5  Are Anti-Predatory Defenses of Molluscan Egg Masses Adjustable? SEGARRA, Gabriel C*; PODOLSKY, Robert D; College of Charleston, Charleston SC gcsegarr@edisto.cofc.edu

Many molluscs, polychaetes, and arthropods deposit or carry their embryos in clutches. Opisthobranch gastropods, for example, typically deposit gelatinous masses of densely spaced embryos, which can be conspicuous and especially at risk for predation. Parental investment in defenses against predators could therefore increase embryo survival, and inducible defenses could provide a particular advantage when the presence and type of predators are highly variable. Egg masses of the sea slug Haminoea vesicula have been shown to deter predation by the purple shore crab Hemigrapsus nudus but not by the hermit crab Pagarus samuelis. It is unknown, however, whether the slug can adjust the level of defense invested in its egg masses or alter its reproductive pattern in response to chemical cues from predators. We hypothesized that the strength of the feeding deterrent in egg masses would depend on the presence and identity of crabs. To test this hypothesis, adult H. vesiculae were exposed to effluent of H. nudus, P. samuelis, or a seawater control. We predicted that egg masses laid in the presence of crabs would have a greater deterrent effect on crab predation, and that the effect would be stronger in the presence of the more risky predator, P. samuelis. We also predicted that, in the presence of crabs, investment in egg masses (mass, length, and embryo density) would decline. Our results did not strongly support either hypothesis: neither the strength of deterrence nor investment per egg mass was clearly related to the presence of crabs. Fewer egg masses, however, were produced in the presence of the more risky predator P. samuelis.