Relative growth and sexual maturity of Trichodactylus borellianus (Decapoda: Trichodactylidae) from the Middle Paraná River

WILLINER V.; TORRES M. V.; CARVALHO D. A

San José

Congreso; Summer Meeting; 2013

The Crustacean Society and Latin American Association of Carcinology

Some dimensions of the crustacean body can grow at different rates than others and result in relative dimensions of two body parts. In this study it was compared the relative growth of some bodies dimensions, related with the sexual dimorphism, compared to cephalothorax width (CW) of the freshwater crab Trichodactylus borellianus. A regression model with segmented relationship was used to verify if there is relative growth among these measurements. The resulted break-point could infer the CW at which crabs reach the sexual maturity. Organisms were collected in ponds of the Middle Paraná River. In the lab, the sex was determined and the cephalothorax width was measured. In males, the length (LC), height (HC) and thickness (TC) of right and left chelae and gonopod length (GL) was taken. In females, the abdomen width (AW) was measured. The values of left chelae did not show break-point. All others showed positive allometry with the exception of the GL. In females the AW inferred a sexual maturity around 7.3 ± 0.4 mm of CW. In males, the results varied ranging from 5.9 ± 0.3 mm to 7.4 ± 0.1 mm of CW for GL and TC, respectively. The AW and GL indicates that each sex reaches sexual maturity at different sizes. It is possible that the accelerated growth of the male gonopod could be a strategy to fecundate older females early. However, the positive allometry of all right chelae dimension may increase the mating chance of larger males.