Pattern of shell utilization by the hermit crab Paguristes tortugae (diogenidae) from Anchieta Island, southern Brazil

Abstract

The objective of this study was to characterize the pattern of shell utilization by Paguristes tortugae, from infralittoral areas of Anchieta Island (Ubatuba, Sāo Paulo State, Brazil) using the percentage of the different shell types occupied and the morphometric relationship between hermit crabs and occupied shells. Specimens were collected monthly (January to December 1998) by SCUBA diving. The animals and the shells were measured and weighed. A total of 2,429 hermit crabs were captured occupying 21 species of gastropod shells. The shells more occupied were Pisania auritula (35.49%), Cerithium atratum (27.83%), Morula nodulosa (12.70%) and Leucozonia nassa (6.83%), respectively. There was differential shell occupation between sexes: males and ovigerous females occupied in higher percentage P. auritula shells while the non-ovigerous females occupied C. atratum. Regression analysis showed best correlation between the size of the crabs (shield length) and shell dry weight. This study showed that shell occupation by P. tortugae involves inter- and intraspecific competition as well as shell type availability in the field.