Infestation of Lymnaea stagnalis by digenean flukes in the Jeziorak Lake.

The low number of articles on naturally trematode-infected snails results from the difficulty to obtain the quantitatively representative material. The main aim of our study was to check which age (size) groups of snails are the most susceptible to trematode invasion. Furthermore, we examined in which season the parasite prevalence is the highest. We collected Lymnaea stagnalis individuals in a nearshore zone of the Jeziorak Lake (the longest Polish lake located in northern Poland). The shell height of the snails was measured and the infestation by trematode larvae was determined. The logistic regression has shown that parasite prevalence increased significantly with the snail size (with the individuals >30 mm being the most infected), the distance from the beginning of the year (i.e., month) and the vicinity of summer.