Shell selection by the tropical hermit crab Calcinus tibicen (Herbst, 1791) (Anomura, Diogenidae) from Southern Brazil

Abstract

Shell preferences, as shown by laboratory choice experiments, are important determinants of shell utilization under natural conditions. Size and shell species preferences of the hermit crab Calcinus tibicen were determined for the three most occupied [ Stramonita haemastoma (Linnaeus, 1767), Leucozonia nassa (Gmelin, 1791) and Pisania auritula (Link, 1807)] shell species along the rocky shore of Grande beach, Ubatuba, Brazil, taking into account the sexual condition of the individuals. All experiments were conducted under laboratory conditions using a glass aquarium where the hermit crabs (independent on their sex condition) were placed naked with a large number of shells of appropriate sizes. The chosen shells were determined after 72 h. The preferred shell species and size were determined by regression analysis. C. tibicen showed no significant choice among the three gastropod shell species. Shell size experiments revealed that the preference of hermit crabs was strongly associated with shell weight and internal volume. The shell adequacy index (SAI) decreased with increasing crab size and showed that the population was occupying relatively adequate shells (SAI=0.99±0.19). The present data lead us to conclude that shell selection by hermit crabs involves individual and sexual preferences taking into account the shell features that best provide protection and survival, principally in the rocky intertidal studied area, characterized by intense wave action.