Morphological sexual maturity by relative growth technique of Uca maracoani (Brachyura, Ocypodidae) from a tropical mangrove

Abstract

Despite of the existence of previous knowledge on the relative growth of U. maracoani for a population of southeastern Brazilian coast, the aim of the study was described and compare the relative growth patterns and sexual maturity of this species from Formoso River mangrove, state of Pernambuco, northeast Brazil, with data from other locations and of congeneric species. The crabs were monthly sampled manually, with a capture effort by one person colleting for 30 minutes at the low tide from April 2009 to March 2010. Crabs of both sexes were measured with a caliper at following dimensions: carapace width (CW), carapace length (CL), cheliped propodus length (CPL), cheliped propodus height (CPH) and abdomen width (AW). Additionally, males were also measured at their gonopod length (GL). The determination of morphological maturity was based on the relationship between the CPL vs. CW for males and AW vs. CW for females, which were the relations that best evidenced the beginning of the morphological sexual maturity for U. maracoani. The relationships CPL vs. CW and AW vs. CW evidenced positive allometry for juveniles and adult’s males and females. However, a negative allometry was observed in the relationship CL vs. CW and GL vs. CW for juveniles and adult’s males, AW vs. CW for adults’ males and, CPH vs. CW for adults’ females. The growth pattern shown by the female abdomen probably is related to egg incubation and the excessive growth observed at the male cheliped is probably related to reproductive process, because this appendage is used at the courtship and intra or inter specific agonistic interactions with other males.  The morphological sexual maturity of males was estimated at 15.8 mm CW (50% of males), with the smallest mature male measuring 17.34 mm, and the largest immature male 18.15 mm CW. Females reached morphological sexual maturity (50%) at 13.8 mm CW, with the smallest mature female at 15.43 mm CW and the largest immature female at 16.32 mm CW. The differential growth patterns between juvenile and adult phases, as well as the onset sexual maturity seem to have relationship with ontogenetic changes, which is mainly related to behavioral or reproductive traits. The growth pattern observed in the female's abdomen is probably related to hatching eggs while overgrowth shown in male cheliped should be related to reproductive processes, as this appendix is used in court and in specific interactions with other males.