Biologia populacional e distribuição de Uca rapax (Smith, 1870) (Crustacea, Decapoda, Ocypodidae) no manguezal de Jabaquara/Paraty - RJ

Abstract

The population biology and distribution were studied in one population of the crab Uca rapax (Smith, 1870) in the mangrove Jabaquara/Paraty, Rio de Janeiro, Brazil (23º14'12,8"S e 44º42'37,1"W). Two collectors captured the crabs monthly (from July 2007 to June 2008) during 15 minutes by procedure of capture per unit effort in low tide periods in six transects. Sediment samples from all the transects were collected to determine particle size and organic matter. A total of 3093 specimes were collected, being 2067 males, 1026 females (148 ovigerous females). The sex ratio differed significanthy from: 1:1 (male: female) and the frequency distribution was uni-modal. The males attained a larger size than the females.The major cheliped is the left one in 53.27% of males. Ovigerous females accounted only about 14.42% of the population. Ovigerous females was most abundant during the warmer months of the year (Spring-summer). Individual fecundity varied from 420 to 22960 eggs (5544 + 4365,57). Mean eggs size was 0.268 + 0.047 mm, varying from 0.187 to 0.392 mm, while the mean volume was 0.009 mm3. The regression analysis show that the number of eggs increases linearly with the increase of the carapace width. The results indicated that distribution of population can be explained by its relationship with the sediment thickness. U rapax were collected, primarily in areas with the sand and high concentrations of organic matter.