UNLIKE TERRESTRIAL HERMIT CRABS, MARINE HERMIT CRABS DO NOT PREFER SHELLS PREVIOUSLY USED BY CONSPECIFICS

摘要

Gastropod shells represent an essential resource for hermit crabs (Decapoda, Anomura). In many cases, hermit crabs acquire used shells from conspecifics who previously occupied the shell. Terrestrial hermit crabs (Coenobita compressus H. Milne Edwards, 1836) strongly prefer used shells. Here we test whether marine hermit crabs (Pagurus samuelis (Stimpson, 1857)) also exhibit a preference for used shells by providing them with matched pairs of (1) a used shell (previously occupied by either the choosing crab itself or by a conspecific) versus (2) a brand new shell (freshly derived from a predated gastropod). Unlike terrestrial hermit crabs, marine hermit crabs showed no preference for used shells (either their original shell or a shell from a conspecific). We suggest the divergent shell preferences of marine and terrestrial hermit crabs relate to the contrasting natural selection pressures in the sea versus on land. In particular, the used shells of terrestrial hermit crabs are architecturally remodeled by prior occupants and these remodeled shells represent a superior resource on land. In contrast, marine hermit crabs never remodel shells, and for them a used shell may be less protective than a new shell against the many specialized shell predators in the ocean