Meeting Abstract

P1.80  Thursday, Jan. 3  Tests for palatability and feeding deterrence in egg masses of nine species of opisthobranch gastropods LEWIS, S.M.*; PODOLSKY, R.D.; College of Charleston, SC; College of Charleston, SC smlewis@edisto.cofc.edu

Many gastropods reproduce by encapsulating embryos inside egg masses or capsules. Often conspicuous to predators due to size, location, or color, egg masses can experience a high predation risk. As a result, embryos within egg masses may benefit from chemical defenses against predation. We tested for chemical defenses in egg masses of nine species of opisthobranch gastropod from the northeast Pacific. We created a set of agarose baits that included or omitted, in all combinations, a palatable food source (squid) and an egg mass homogenate. This set of baits was presented to individuals of three crab predators (Hemigrapsus nudus, Oregonia gracilis, and Pagurus samuelensis). By comparing the relative consumption of different baits we tested whether egg masses were treated as a food resource or as a feeding deterrent. Egg masses of three gastropod species (Haminoea vesicula, Melanochalmys diomedea, and Phylaplysia taylori) were treated as a feeding deterrent by at least one crab species, while egg masses of seven gastropod species (Doris montereyensis, Phyllaplysia taylori, Haminoea vesicula, Haminoea callidigenata, Melibe leonina, Tritonia diomedea, Gastropteron pacificum, and Melanochlamys diomedea) were treated as a food resource by at least one crab species. Predators differed dramatically in their responses to baits: H. nudus treated three species of egg mass as feeding deterrents and four as a food resource; O. gracilis treated one species as a deterrent and none as a food resource; and P. samuelensis treated none as a deterrent and six as a food resource. These results suggest that some egg masses may gain protection from being unpalatable to predators, but that predators vary in their sensitivity to these potential defenses.