P3.93 Friday, Jan. 6 Factors affecting the drilling and feeding behavior of Lewis’ moon snail, Euspira lewisii (Gastropoda: Naticidae) NEWEL, M.S.*; BOURNE, G.B.; University of Calgary, Alberta; Bamfield Marine Sciences Centre, British Columbia email@example.com
Euspira lewisii, the largest extant naticid gastropod, displays a stereotypical naticid feeding behavior while preying almost exclusively on bivalves. After capturing a clam, E. lewisii drills a beveled hole through the clam’s shell using its radula. Typically the drill hole is found near the umbo. Our previous experiments on snails collected from Barkley Sound, British Columbia, maintained in our Calgary laboratory together or in isolation and fed ‘littleneck’ clams (native Protothaca staminea or introduced Venerupis philippinarum), which are natural prey species that have also been used by other researchers. We found that in many instances without completing the drill hole snails smothered their prey within the envelop of pedal mucus used to restrain them, and then fed on the ‘gaping’ clam. Recently, others have reported that given a choice, E. lewisii appear to select thinner-shelled clams. Yet another report suggested that a related species (E. fortunei) preferentially drills the left valve of its prey. Using our extensive collection of post-feeding clam shells (primarily V. philippinarum), we conducted a morphometric analysis of the shells and their respective drill holes. We also examined a representative sample of live clams. We found that drill holes were relatively equally distributed among the left and right valves. However, drill-hole site fidelity decreased as the snail’s health declined and in some cases when different clam species were provided. Since prey capture requires extensive manipulation, certain aspects of morphology (e.g., relative density) may provide E. lewisii with cues of the profitability of their potential prey.