Use of partially predated gastropod shells, shell choice behavior, and symbionts of Pagurus longicarpus from Long Island, New York

Hermit crabs possess soft, twisted abdomens and typically depend on empty gastropod shells for protection from predators and desiccation. Hermit crabs are found worldwide, living predominately in marine environments. Pagurus longicarpus is the most abundant hermit crab species in intertidally marine waters of Long Island. Field collections of P. longicarpus documented for the first time that these hermit crabs inhabit shells with snail soft tissue still present, suggesting occupation of recently predated shells. The objectives of this research were to: (1) determine the shell species used by P. longicarpus and the symbiont communities supported by these hermit crabs, (2) determine whether P. longicarpus and/or Libina emarginata can prey on Littorina littorea, (3) determine whether P. longicarpus prefers intact or partially predated snail shells, and (4) determine prevalence of partially predated snail shell use and fate of snail tissue.;I found that P. longicarpus occupied six and seven shell species along the north and south shores of Long Island, respectively. The symbiont communities were not significantly different between the two shores but there were differences in abundance of four symbiont species. Hydractinia symbiolongicarpus was found in high abundance at both shores. The north shore exhibited more Crepidula sp. and Polydora websteri; while the south shore had more Balanus sp. and Lepidonotus sublevis. In the laboratory, L. emarginata were able to pull the operculum off without damaging shells, leaving shells with tissue still intact. P. longicarpus were not able to predate on live, healthy snails. Based on these findings, L. emarginata appear to be the crab that was predating on snails in the field. Hermit crab shell preferences differed based on whether they are with conspecifics or isolated. When in communal tanks, hermit crabs preferred partially predated snail shells to empty and original shells. Original shells and empty shells were occupied with more frequency than partially predated shells in isolated tanks. The use of partially predated snails may allow the hermit crab population in some areas flourish. Since empty gastropod shells are the limiting factor in many populations, the use of a new shell choice will benefit the livelihood of hermit crabs.