Meeting Abstract
P3.139 Tuesday, Jan. 6 Eat and run: Predator preference for and escape responses by potential hosts of the snail Crepidula adunca (Mollusca, Gastropoda) PETCHLER, E.M.*; IYENGAR, E.V.; Muhlenberg College, Allentown PA; Muhlenberg College, Allentown PA ep233887@muhlenberg.edu
When a species strictly associates with only one host, despite the presence of many similar alternatives, the question arises as to what selection pressures are driving the specificity of this symbiosis. The suspension-feeding, epibiotic, marine snail Crepidula adunca is found almost exclusively on the host snail Calliostoma ligatum in the San Juan Islands, Washington. This fidelity is especially surprising considering that other potential hosts, including the similarly-shaped, confamilial snail Margarites pupillus, exist in the same habitat. We investigated whether predator preference for hosts other than C. ligatum may have contributed to the evolution of C. adunca‘s specialization on C. ligatum. The sea stars Pisaster ochraceus and Leptasterias hexactis, the crabs Cancer productus and Cancer oregonensis, and the snail Lirabuccinum dira are the dominant predators that co-occur with Crepidula adunca. Of these, Leptasterias hexactis is the most voracious predator of both C. ligatum and M. pupillus, and contact with L. hexactis causes a violent reaction in individuals of these species of snails. Leptasterias hexactis prefers to consume Margarites pupillus, the snail not utilized by Crepidula adunca, rather than the host Calliostoma ligatum. This preference is not just due to differences in escape behaviors between the snails, because the sea star consumes more individuals of M. pupillus than C. ligatum when the snails are prevented from moving. Other anti-predatory behaviors, such as running speed and defensive tactics may also contribute to higher rates of predation for M. pupillus compared with C. ligatum. Thus, host choice by Crepidula adunca is likely due, at least in part, to relative risks of predation for the various host species.
