Distribuição e estrutura populacional das espécies de Uca Leach, 1814 (Crustacea, Decapoda, Ocypodidae) no manguezal de Itacuruçá - RJ

Abstract

This study was conducted in the Itacuruçá Mangrove, Sepetiba Bay, Rio de Janeiro, Brazil, with the objective to investigate the distribution and population structure of the Genus Uca Leach, 1814. Sampling was performed in five areas from June/05 to May/06, using the capture effort per unit. Sediment samples from all the areas were collected to determine particle size, organic matter, phosphor and heavy metal analyses. Eight species were collected, U. victoriana which were recorded only in the State of Espírito Santo; U. rapax was the more abundant species and U. vocator the rarer. The results indicated that distribution of the crabs can be explained by its relationship with the sediment thickness. U. leptodactyla, U. rapax, U. vocator, U. mordax and U. uruguayensis were collected, primarily in areas with the sand and low concentracion of organic matter. U. thayeri, U. cumulanta and U. victoriana were collected, primarily in muddy areas with high concentrations of organic matter. U. rapax and U. leptodactyla were the species which were more versatile in habitat colonization. A total of 2580 crabs were obtained of which 1465 males and 1100 were nonovigerous females. Only 15 ovigerous females were collected during the study. The size of the crabs in the Itacuruçá´s Mangrove were the smallest size than those found in other Brazilian mangroves. However, the males attained a larger size than the females. The size frequency distribution was unimodal for the majority of the species, the only exceptions being U. thayeri and U. vocator which didn t show the defined pattern. Males were most abundant in the larger size classes. The sex ratio differ significant from 1:1 propotion (male: female), with the exception of U. leptodactyla which most of the time had a higher frequency of males.