Vertical spatial behaviour patterns of Lymnaea truncatula in relation with origin of snails, infection with Fasciola hepatica, and experimental environment

Ethological studies were carried out on three Moroccan populations of Lymnaea truncatula of which two of them were living in a flooding irrigation system (Tassila, Oued Massa valley) and the third in a nonirrigated habitat. Most of the Tassila snails were found in the deep water zone. Two factors significantly influenced the presence of snails in this zone : the water current velocity, and parasitic infection of the molluscs. In the presence of other factors (lack of food, the presence of the snail Physa acuta ), the L. truncatula were recovered more frequently in zones outside of the water and just beneath the water’s surface. Despite the modifications noted in snail distribution, Bulinus truncatus did not appear to be a competitor. Lastly, habitat drying resulted in partial or complete burrowing of 50 % of snails.