Distribuição de caranguejos Trichodactylidae (Crustacea, Brachyura) em alagados do Pantanal Mato-Grossense (Brasil) e sua correlação com a proximidade do rio Cuiabá e cobertura vegetal

Abstract

There are few papers about crabs in the Pantanal area and that works are mainly with carcinofauna of rivers and lakes. Pantanal is the biggest floodplain of the world, located in a sedimentary basin in the central portion of South America, with around 138 km² of area. There are two season, the rainy and dried, with the flooding period starting in January and finish in April. In this present paper, the distribution of the crabs is studied in temporarily flooded habitats between Cuiabá and São Lourenco Rivers, in the Pantanal of Mato Grosso State, both tributary of the Paraguay River. The collect period was in rainy season, daily between 22/02/08 to 03/03/08. The environmental and animal data were collect using 20 plots with 25 m² each, and a siege net with 3 mm of mesh size and captured crabs with beach seine of the same mesh. The vegetation was removed and washed inside of the plots to extract the associated fauna. The habitats were differentiated according to the phytophisionomy, the availability of animal shelter, the type of the submerse plant structures and the distance of the Cuiabá River. The effect of these variables over abundance of crabs associated to the habitats was verified by Kruskall-Wallis test and by linear regression. The mean density of the crabs was 0,63 individuals/m² and the juvenile stage was predominant. It was sampled three of the most abundant species among the six Trichodactylidae species that occur in the region. The correlation was positive to the availability of submerse plant structures, specially grass cover, and negative to the distance of the river. These results show that migration and dispersion to the flooded areas reduces with the distance of the river and concentrates in native or exotic grasses. Probably for the crabs, the gramineae has same ecological role in the flooded areas as the macrophytes have in the perennial water bodies.