Temporal analysis of the weight/carapace width relationship and the condition factor in Uca mordax (Smith, 1870) (Crustacea, Decapoda, Ocypodidae) in the Igaraçu River, Parnaíba, PI, Brazil

Abstract

Crabs of the genus Uca Leach, 1814 are widely distributed along the Brazilian coast and play an important ecological role in the estuarine ecosystem in soil bioturbation, nutrient cycling and by serving as a food source for other organisms. This study analyzed the relationship of wet weight/carapace width and the temporal dynamics of the condition factor of the crab Uca mordax (Smith, 1870). The crabs were sampled manually on the bank of the Igaraçu River (02°53’58”S; 41°46’49”W) from September 2009 to June 2011, in the dry and rainy seasons. A total of 602 crabs (449 males and 153 females) were analyzed. The carapace width (CW) and the wet weight (WW) were determined for each individual. The biometric data obtained were submitted to a regression analysis using the power equation (y=axb). The CW/WW relationship for males was expressed by the equation WW=0.00011CW3.441, and for females by WW=0.000183.211. The condition factor was determined for each month and compared between the sexes. The females showed a 1.6 higher degree of fattening than the males. In the rainy season the females showed an isometric increase in weight, while the other relationships (males during the dry and rainy seasons and females in the dry season) showed a positive allometric increase. There was no significant difference in the degree of fattening between males and females.