Predation of Glossiphonia weberi (Blanchard, 1897) on the Invasive Snail Physella acuta (Draparnaud, 1805) in the Presence of an Alternative Prey

The North American freshwater snail Physella acuta has invaded and colonized a wide range of freshwater habitats, globally. Resembling other invasive species, P. acuta has several negative impacts on the invaded freshwater ecosystems, which calls for its regulation, preferably through biological control. The malacophagous leech Glossiphonia weberi, native to West Bengal, India, had been previously reported as a potential biocontrol agent of P. acuta. In this experiment, we observed the predation potential and prey preference of G. weberi on P. acuta in the presence of a native snail, Gyraulus convexiusculus. The results suggest that in all instances, G. weberi consumed less G. convexiusculus compared to P. acuta. In complex habitats, G. weberi showed significant prey preference to P. acuta except in the habitat characterized by the presence of pebbles. The complex habitats bear a significant (p < 0.05) negative impact only in the case of predation on P. acuta when present with conspecific but not in heterospecific prey conditions. Therefore, G. weberi qualifies as a useful biological control agent that can affect the colonization and expansion of the invasive snail P. acuta, even in the presence of alternative prey.