Onset of sexual maturity and relative growth of the freshwater crab Trichodactylus fluviatilis (Trichodactyloidea) in south-eastern Brazil

Abstract

The main purpose of this study was to provide an estimate for the onset of morphological sexual maturity in the freshwater crab Trichodactylus fluviatilis, from a population located in south-eastern Brazil, based on the relative growth relationships, as well as the characterization of “handedness”. Monthly collections were carried out at night, from January 2006 to January 2007, in a small water body. In the laboratory, the crabs were sexed; the following body structures were measured and the estimate of onset of sexual maturity was given by the logistic function, as y = a/(1 + be ^{− cx} ), for 50% of the population to reach the adult phase (CW₅₀carapace width). Right propodus length and abdomen width were the best-fit relationships to represent the onset of sexual maturity for males and females, respectively. Based on the logistic function, the onset of sexual maturity was estimated to occur at around 18 mm CW for both sexes. The relative growth recorded for this species is consistent with the model for brachyuran crabs (Hartnoll RG. 1982, Growth. In: Bliss, DE, editor. The biology of Crustacea: embryology, morphology and genetics. New York: Academic Press. p. 111–196), except for the abdomen growth, which is likely to be an adaptive condition related to protection of the newly hatched young.

Keywords:

• Trichodactyloidea
• epimorphic development
• reproduction

Acknowledgments

The authors are indebted to Janet Reid for her constructive comments on early drafts of the manuscript, and help with English language, to their colleagues at the LabBMar – UNITAU, during the field surveys, and to the Universidade de Taubaté for allocating their facilities and providing financial support. All sampling in this study have been conducted with applicable state and federal laws. V.J. Cobo is also grateful to the Universidade de Taubaté for financial support (Process # 251/2001-PRPPG). D.J.M. Lima is grateful to CNPq-PIBIC (Process # 106126/2006-7) for financial support for his undergraduate grant.