Relative growth and morphological sexual maturity of Panopeus occidentalis Saussure, 1857 (Brachyura; Panopeidae) in Cananéia, São Paulo

Abstract

Decapods of infra order Brachyura show several morphological specializations, such as the dorsoventrally compressed carapace, with lateral expansion; the abdomen bending; and a rigid and developed exoskeleton. Such changes resulted in a great success in the conquest of new environments and a consequently large number of species from this group. Only the first pair of pereopods is chelated and developed in Brachyurans, which helps in defense, food searching and for males in courtship rituals and female handling of during copulation. The study of relative growth compares the size between two body structures, so the rigid carapace of crabs is an advantage for this type of study since it allows precise measurements needed for the study. The equation used in the relative growth analysis is a function power represented by "Y = a.xb", where "b" indicates the type of allometry or isometry when relating two dimensions. This study aims to estimate the size at which individuals of P. occidentalis become morphologically able for reproduction, using relative growth study tools.