Comunidade de Nematoda em diferentes ambientes límnicos

Abstract

This study was conducted at the São Francisco River basin, and the following hypothesis were tested: (1) distinct bodies of water in a limnic system represent different habitats and, consequently, display different Nematoda assemblies with different structures; (2) the multivariate structure of Nematode assemblies differ according to the heteronegeity of the sedimentary habitat. Field sampling took place in six habitats from a hidrgraphic basin: in the main course of the basing four habitats were sampled: vegetated sand (VGS), non-vegetated sand (NVS), vegetated mud (VGM), and non-vegetated mud (NVM). Sampling also took place in marginal lagoons (MGL) and in and effluent of the basin’s main river (BCR). 39 taxas of Nematoda were registered in all of the studied habitats, being 38 genera and also individuals belonging to the Dorylaimida order, for which it wasn’t possible to identify the genus. Among there taxa, the genera Anonchus, Ironus, Paramonohystera and Microlaimus were the most abundant. The highest value for the number of genera was registered in the VGS habitat (26) and the lowest in NVS (5). The total density values of the Nematoda ranged from 35,52 and 3803,8 ind./10cm² for the habitats LVG and LGM, respectively. The total length of the Nematoda varied between 95,55 (Paramonohystera) and 2675 μm (Ironus), while the width oscilated between 9,45 (Microlaimus) e 50,4 μm (Ironus). The values of the length/width ratio (l/w) varied between 12,4 (MGL) e 70,77 (VGS). In that way, it can be concluded that habitats with different environmental caracteristics might have same importance for the mtorphometry and maintenance of the system’s diversity, being noted that, the caracteristics of the sediment, such as the silte+clay proportion, average size, assimetry, curtosis and selection of the sediment’s grains influenced directly the morphometry and structure of the studied Nematoda groups. Even though the Nematoda’s morphometry was influenced by various physical caracteristics of the sediment and by the different food supplies, it was possible to observe in whitch general manner the morphometry of the Nematode is influenced by collective of integrated environment factors.