Biologia populacional de Uca victoriana no manguezal de Itacuruçá/Coroa Grande, Baía de Sepetiba, RJ.

Abstract

Uca victoriana von Hagen, 1987 is a crab belonging to the family Ocypodidae typical from intertidal zones, characterized by a strong sexual dimorphism. This current study was elaborate in order to evaluate the information about biology of the population, more specifically about population structure, spatial distribution, and reproductive aspects of U. victoriana from mangrove of Itacuruçá / Coroa Grande located in Sepetiba Bay, RJ. Three transects were established with three areas on the right bank of the Draga river, and each area containing 10 m long and 2.25 m wide. Crabs were collected monthly during the period of November 2010 to October 2011. The animals were collected using a quadrat of 30 x 30 cm, performing three random replicates in each plot. In laboratory, the animals were separated by sex and it were taken biometric measurements such as carapace width, carapace length, abdomen width, height of the larger chelipod, length of the larger chelipod and length of the gonopod. Sediment samples were collected in three transects to determine the granulometric composition. It was collected a total of 529 individuals in the study period, of which 89 were males, 97 females non-ovigerous, 16 ovigerous females and 327 juveniles. In the population structure the frequency distribution of males and females was unimodal. The average size of the female LC was 5,64 ± 1,73 mm and 4,97 ± 1,53 mm for males. The analysis of size comparison between sexes showed that females are significantly larger (U = 23741.5, p <0.001) than males. The overall sex ratio of population was 1,94:1, predominantly males. In spatial distribution, there was a greater abundance of animals in the area 2, where the predominance of juveniles, ovigerous females and non-ovigerous females was not superior to other transects. The average size of the ovigerous females was 6.67 ± 0.60 mm, ranging from 5.38 to 7.70 mm. Mean fecundity was 424 ± 186 eggs, with a range from 211 to 886 eggs. The average size of the eggs was 0.292 ± 0.011 mm, with a width 0.27 to 0.30 mm. Recruitment occurred in April. The morphological maturity of females was estimated for the size 5.0 mm and 5.9 mm for males. It follows that the U. victoriana population from mangrove studied, showed to be stable, showing juveniles during all of the months. The distribution of U. victoriana was not influenced by temperature or granulometric, suggesting that other factors, for example, the abundance of trees or biologic factors could influence their distribution in the mangrove. The fecundity found in this population correlates with the females size, as occurs in most brachyuran. The reproductive period was seasonal, with higher frequency of ovigerous females in the months of September and October.