Meeting Abstract

P3.174  Tuesday, Jan. 6  He is heavy & he aint my brother: Marine snails catching a ride IYENGAR, EV*; PETCHLER, E; HUTCHINSON, KA; Muhlenberg College; Muhlenberg College; Muhlenberg College iyengar@muhlenberg.edu

Symbiotic interactions beg the question as to the degree to which the guest has specialized on a particular host and the relative costs and benefits of the association to each participant. On San Juan Island, Washington, the suspension-feeding marine snail Crepidula adunca is found almost solely residing in a characteristic, external location on the body whorl of the snail host Calliostoma ligatum. Numerous other hosts are available, including Margarites pupillus, a sympatric snail in the same taxonomic family as Calliostoma with a similar shell shape. Field transects indicated that individuals of Crepidula in the San Juans reside on Calliostoma more than on any other host. The incidence of infection across sites ranged to >80%, with an average epibiont load of up to >3 individuals per host, representing an addition of >7% of the body weight of the host. In laboratory choice experiments, individuals of Crepidula preferred Calliostoma hosts to the other common potential hosts, including hermit crabs in Calliostoma shells. Crepidula did not show a preference for intact versus sanded Calliostoma shells. These results suggest that the cue used by Crepidula to identify an appropriate host is likely from live Calliostoma tissue or is in Calliostomas shell and rapidly degrades post-mortem. In general, predators (two species of sea stars, two species of crabs, one snail) did not eat many Calliostoma, whether they were infected with Crepidula or not. Thus, Crepidulas presence does not confer a protective benefit to Calliostoma against the common predators. This symbiotic interaction is likely parasitic, as the additional weight and surface area from Crepidula epibionts likely result in energetic costs for the Calliostoma host and no benefit for the host has been identified.