Spatial distribution of fiddler crabs (genus Uca) in atropical mangrove of northeast Brazil

Abstract

The influence of abiotic factors on the spatial distribution of the fiddler crabs Uca leptodactyla, U. maracoani,U. rapax and U. thayeri was studied in a tropical mangrove of northeast Brazil. Eight transects were delimited in a mangrovearea of the Pacoti River. On each transect, three 0.25 m2squares were sampled during spring low tide periods from September2003 to August 2004. The sediment of the squares at each transect was analysed for grain size, organic matter and humidity.Morphology of the second maxilliped was studied considering the number of spoon-tipped setae to help explain the ecologicaldistribution of the species. U. leptodactyla and U. rapax were found living in medium sand, U. thayeri was collected in fine andvery fine sand, while U. maracoani was found living in very fine sand. U. leptodactyla showed a negative correlation withorganic matter and humidity while U. thayeri showed a positive correlations for both factors. U. maracoani and U. rapaxwerenot correlated with organic matter or humidity. The analysis of the second maxilliped revealed that U. leptodactyla and U. rapaxshow a high quantity of spoon-tipped setae while U. maracoani and U. thayeri show a greater quantity of plumose setae.