[Ecology of Lymnaea truncatula Müller, intermediate host of Fasciola hepatica Linné in the microclimate of Tozeur (southeast of Tunisia)].

Systematic visits were carried out in the traditional Tozeur' oasis (Tunisia), in 1997/1998 in order to study the ecology of Lymnaea truncatula as well as its density in relation to habitat characteristics in the hydrographical networks of the oases. Lymnaea truncatula was enumerated on 1 m2 surface by habitat, according to the quadrat method. Samples of soil, irrigation and draining water were also analysed. The density of Lymnaea truncatula detected in autumn was constantly higher. It depends on the nature of the habitat: 54.8% in the secondary irrigation canals, 34.8% in those of draining, 7.6% in the seguia and 2.9% in the principal draining canal. Ecological factors--permanent dampness, suitable luminosity, basic pH of soil and water, temperature between 10 and 28 degrees C--contribute to the multiplicity of snails.