Abstract
The objective of this study was to characterize the pattern of shell utilization by Paguristes tortugae, from infralittoral areas of Anchieta Island (Ubatuba, Sao 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.
Highlights
According to Conover (1978), the ability of hermit crabs to occupy and carry gastropod shells is one of the main reasons for their evolutionary success.Hermit crabs need increasingly larger shells during their life cycle, a fact that keeps them in constant activity searching for suitable shells (Bertness, 1981)
The hypothesis more commonly used to explain that shells are in short supply are that natural populations of crabs are often in smaller shells than preferred in laboratory experiments (Vance, 1972; Scully, 1979; Bertness, 1980), empty shells are often rare in the habitats that support hermit crab populations (Hazlett, 1970; Bertness, 1980) and, hermit crabs often have ritualized shell-exchange behavior that may be beneficial when shell resources are scarce (Carlon and Ebersole, 1995)
The objective of the present study was to characterize the pattern of shell utilization in the field by P. tortugae inhabiting the infralittoral area of Anchieta Island, Brazil investigating the factors that influenced the occupation of gastropodshell species by each sex and the morphometric relationships between hermit crabs and their shells assessed
Summary
According to Conover (1978), the ability of hermit crabs to occupy and carry gastropod shells is one of the main reasons for their evolutionary success.Hermit crabs need increasingly larger shells during their life cycle, a fact that keeps them in constant activity searching for suitable shells (Bertness, 1981). Several authors have studied shell occupation by hermit crabs in the field (Walters and Griffiths, 1987; Gherardi and Vannini, 1989; Gherardi, 1991; Negreiros-Fransozo and Fransozo, 1992; Manjón-Cabeza and García Raso, 1999; Martinelli et al, 1999; Bertini and Fransozo, 2000), and others have studied hermit crabs under laboratory conditions to verify the preference pattern by shells utilized (Lively, 1988; Hazlett, 1992; García and Mantelatto, 2001). Despite this background and considering the high number of hermit crab species described worldwide, few studies have evaluated comparatively shell occupation in the field and in laboratory conditions (see Mantelatto and García, 2000 for review)
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