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Helgol Mar Res (2009) 63:169175 DOI 10.1007/s10152-009-0144-0
ORIGINAL ARTICLE
Use of pleopod morphology to determine sexual dimorphism and maturity in hermit crabs: Isocheles sawayai as a model
Marina Zilio Fantucci Renata Biagi Fernando Luis Mantelatto
Received: 25 June 2008 / Revised: 17 December 2008 / Accepted: 9 January 2009 / Published online: 3 February 2009 Springer-Verlag and AWI 2009
Abstract In the Anomura, studies on growth patterns are infrequent, possibly because the heterogeneity of the group, especially in terms of morphology, makes it diYcult to construct generalized growth models. Particularly hermit crabs are an interesting group to evaluate aspects of growth, because of their unique body. Isocheles sawayai, a hermit crab found only in the western Atlantic Ocean, poorly known with respect to its sexual dimorphism and maturity, was investigated here based on morphometry. Monthly collections (July 2001 through June 2003) were made from a shrimp Wshing boat in the Caraguatatuba region on the northern coast of the state of So Paulo, Brazil. The specimens were measured and weighed, and had their sex checked. Throughout the sampling period, 374 specimens of I. sawayai were collected (11.23% nonovigerous females, 6.69% ovigerous females, 79.41% males and2.67% intersexes). The size at which morphological sexual maturity was reached by both sexes ranged from 4.0 to4.3 mm shield length, according to the relative growth and the size of the smallest ovigerous female. Sexual dimor-
phism was shown by males, which were signiWcantly larger than females, and by diVerences in growth pattern between the sexes, especially for relationships that involved the pleopods, which is related to their diVerent functions in males and females. The present study is one of the Wrst to use pleopod morphometry to determine sexual maturity and dimorphism in hermit crabs, especially for species with intersexuality such as I. sawayai.
Keywords Anomura Diogenidae Relative growth
Introduction
In spite of the undisputed importance and prominence of the Anomura in the evolutionary context (Cunningham et al. 1992) and the large number of described species, relatively little research has been done on hermit crabs, particularly with respect to sexual maturity and dimorphism; this may be attributed to their lack of commercial value. Studies on the growth patterns of anomurans are even less frequent, possibly because of the heterogeneity of the group,...