Meeting Abstract

P2.3  Sunday, Jan. 5 15:30  Goldilocks and the three shells: when the home is just right for the hermit crab Pagurus granosimanus SCHAPIRO, D.*; IYENGAR, V.K.; SUMMERS, A.P.; Kalamazoo College; Villanova University; University of Washington David.Schapiro10@kzoo.edu

Hermit crabs rely on gastropod shells for temporary homes, as these shells protect their vulnerable, uncalcified abdomens from predators and competing crabs. Previous studies have shown that a lack of adequate housing significantly reduces growth, reproduction and feeding rates. It is known that hermit crabs use a combination of tactile, visual and chemosensory cues to examine new shells, and preferences are often species specific. Here we used a rapid prototyping technique to explore the morphological preferences of hermit crabs in the absence of any other cues. The hermit crab Pagurus granosimanus was given a binary choice of two shell sizes from one of three gastropod species of very different morphologies. Shells were scaled at 1% intervals and 3-D printed in plaster infiltrated with cyanoacrylate to mimic natural shell material. Live hermit crabs were de-shelled and given a choice between synthetic shells of different sizes. Hermit crabs were able to distinguish a 5% size increase and 9% size decrease in aperture in Oxystele shells when compared with their corresponding natural shells. With Turritella shells, crabs detected a 7% size increase and 10% size decrease, while in Haustellum shells, crabs detected a 6% size increase and 11% size decrease. With all observed preferences, hermit crabs chose their current shell size over enlarged or undersized shells with the exception of Turritella shells, where an oversized shell was preferred. Hermit crabs were capable of detecting a difference of just 789 microns in shell operculum size. There was no clear relationship between hermit crab mass and natural shell mass. This study suggests that tactile cues such as shell aperture size play a much more important role in shell selection than mass and that crabs are capable of very fine distinctions in morphology. Additionally, hermit crabs are more willing to select undersized shells than oversized ones.