Relative growth and determination of morphological sexual maturity of the fiddler crab Uca thayeri Rathbun (Crustacea, Ocypodidae) in two mangrove areas from Brazilian tropical coast

The aim of this paper was to study the relative growth and the morphological sexual maturity of Uca thayeri from two mangrove areas of the State of Pernambuco, Northeast Brazil. The crabs were manually collected monthly at the Ariquinda and Mamucabas Rivers, during spring low tide, from April 2008 to March 2009. Crabs were measured at the following dimensions: carapace width (CW); carapace length (CL); cheliped propodus length (CPL); abdomen width (AW) and gonopod length (GL). The growth was described by the equation y = a x b . The sexual maturity was estimated through a logistic equation. A total of 2,711 individuals of U. thayeri were collected. Females presented larger CW than males, an adaptation to increase the production of eggs. In the relationship CPL vs. CW, males showed positive allometric and females, negative allometric growth. On the other hand, in the relationship AW vs. CW, males showed negative allometric and females, positive allometric growth. This pattern is a reflex of the growth of the cheliped in males and of the abdomen in females, due to their sexual functions. Males reached maturity at larger sizes than females in both mangroves areas, probably due to their greater investment in somatic growth, while females spend their energy in the reproductive process.