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

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 fo r the three most occupied [Stramonita haemastoma (Linnaeus, 1767), Leucozon ia nassa (Gmelin, 1791) and Pisania auritula (Link, 1807)] shell species al ong the rocky shore of Grande beach, Ubatuba, Brazil, taking into account t he sexual condition of the individuals. All experiments were conducted unde r laboratory conditions using a glass aquarium where the hermit crabs (inde pendent on their sex condition) were placed naked with a large number of sh ells of appropriate sizes. The chosen shells were determined after 72 h. Th e preferred shell species and size were determined by regression analysis. C. tibicen showed no significant choice among the three gastropod shell spe cies. Shell size experiments revealed that the preference of hermit crabs w as strongly associated with shell weight and internal volume. The shell ade quacy index (SAD decreased with increasing crab size and showed that the po pulation was occupying relatively adequate shells (SAI = 0.99 +/- 0.19). Th e present data lead us to conclude that shell selection by hermit crabs inv olves individual and sexual preferences taking into account the shell featu res that best provide protection and survival, principally in the rocky int er-tidal studied area, characterized by intense wave action. (C) 2001 Elsev ier Science B.V. All rights reserved.