Shell utilization pattern of the hermit crab Calcinus tibicen (Diogenidae) from southern Brazil

The purpose of this study was to determine the shell utilization pattern of Calcinus tibicen using the percentage of the different shell types that were occupied, the morphometric relationship between hermit crabs and occupied shells, as well as shell availability based on the empty shells and living gastropods observed. Specimens were collected at two-month intervals from January to November 1998 along the rocky shore of Praia Grande, Ubatuba, using a specific methodology adapted to the irregular surface of the area. Of 1,069 shells collected, empty shells were less frequent (4.11%) than shells occupied by either hermit crabs (23.11%) or living gastropods (72.78%). A total of 247 hermit crabs were captured occupying seven of the twelve shell species collected in the field. Only Stramonita haemastoma was occupied in significant numbers (71.26%); There was a differential shell utilization pattern between sexes; males were most abundant in S. haemastoma shells while the ovigerous females occupied Leucozonia nassa. Regression analysis showed a close correlation between the dimensions of the crabs and the utilized shells. In this study, shell occupation by C. tibicen varied as a function of shell type availability, with intraspecific differences in occupation patterns also occurring.