Occurrence of Cruzia tentaculata Larvae in the Land Snail Megalobulimus abbreviatus—Influence of Natural Parasite Load on Snail Physiology

The nematode Cruzia tentaculata is reported here for the first time in the land snail Megalobulimus abbreviatus in southern Brazil. The snails were infected with a high prevalence of larvae up to the L3 stage (68.6%). Cysts were located mainly in the mantle (pulmonary cavity) and the nerve ring. No other helminths were identified in the collected snails. Some physiological aspects were compared between snails infected with L3 larvae and non-infected snails and among infected animals with different parasite loads. No differences were found in hemolymph protein, glucose, or urea content between L3-infected and non-infected snails, nor among animals with different parasite loads. Discontinuous lesions in the rectum associated with the presence of encapsulated larvae were visible in animals with high parasite loads and were more frequent in adult animals. All analyses were carried out during the breeding season; however, the albumen glands of mature snails had a smaller volume in those with higher parasite loads. Ovotestis weight was also significantly negatively correlated with parasite load. Snail reproductive capacity could, therefore, be partially impaired but only for individuals with higher parasite loads. Considering only the measured parameters, natural infection by C. tentaculata does not appear to affect intermediary metabolism of M. abbreviatus. A greater number of larvae and greater severity of tissue injuries are more frequently observed in older snails.