Distribution of freshwater snails in the temporary pond of Annasser in Ouergha watershed, Morocco

Abstract

The main goal of this investigation was to study the systematic, description and distribution of freshwater molluscs in the Annasser lakes located in Ouergha watershed (Morocco). The semi-quantitative surveys carried out between September 2002 and December 2005 has focused on four selected stations in the temporary pond. The choice of these stations was based on the molluscan data available, physical structure of the pond, structure associated vegetation, species diversity in each station and the maximum coverage area of the pond. Eight species of freshwater molluscs were collected in the malacological survey. The specific diversity of aquatic snails are positively correlated with the heterogeneity and complexity of natural vegetation and type of substrate of the temporary pond. Indeed, the malacological fauna of the study area is characterized by species of alluvial sedimentation (Physa acuta and Lymnaea peregra), species typical of stagnant environments rich in organic matter (Succinea debilis, Pisidium casertanum, Pisidium personatum and Pisidium nitidum) and finally species with affinities for river annexes (Lymnaea truncatula and Ancylus fluviatilis).