Relative growth, sexual maturity and handedness in the ghost shrimp callichirus major (Decapoda: Callianassidae) from the southwestern atlantic

Summary: Biometric studies provide valuable information about changes associated with the growth and sexual maturity of living organisms. We analysed sexual dimorphism, allometric growth, sexual maturity and handedness in the ghost shrimp Callichirus major at Gonzaga beach, Brazil, where the catches of this species have been prohibited since 1992. To this end, a total of 544 individuals of C. major were collected during 12 months of sampling. Males were significantly smaller than females, denoting sexual dimorphism with respect to body size. The analysis of allometric growth between chelar carpus length and carapace length (CL) revealed a positive allometric relationship in juveniles of both sexes and adult males, but a negative allometry in adult females. Overall, our results showed the existence of two main growth phases related to sexual maturity, with a similar transition point for males (15.0 mm CL) and females (16.0 mm CL). Heterochely and homochely were registered in shrimp from both sexes, but in males heterochely occurred to a higher degree and was predominant (86.9%), whereas in females homochely was slightly more frequent (59.3%). The consequences of sexual dimorphism in terms of body size and chelipeds in the mating system of C. major are discussed in this study.