Shell selection, utilization and predation in the hermit crab Clibanarius panamensis stimpson in a tropical mangrove estuary

Patterns of shell selection and utilization in the hermit crab Clibanarius panamensis Stimpson were studied in a small mangrove estuary in the Gulf of Nicoya, Costa Rica. Three common gastropod species potentially provided shells for hermit crab occupation: Thais kioquiformis Duclos, Littoraria varia (Sowerby) and L. fasciata (Gray). Crabs were found to occupy both L. varia and Thais in proportions greater than the relative abundances of snail populations. L. fasciata snails were abundant in the field but crabs did not occupy this shell species. Laboratory selection experiments determined a shell preference order of Thais > L. varia > L. fasciata. Shell morphological and strength measurements indicated that shell antipredator characteristics decreased in the order Thais > L. varia > L. fasciata. In field and laboratory predation experiments, vulnerability generally reflected this order. Predation intensity also varied seasonally, possibly reflecting abundances of predatory fishes and crustaceans. This study is consistent with the hypothesis that predation is an important selective pressure influencing shell selection and utilization by C. panamensis.