Feeding of the leech Glossiphonia weberi on the introduced snail Pomacea bridgesii in India

Abstract

The predation potential of the indigenous leech Glossiphonia weberi on the snail Pomacea bridgesii, introduced in India, was evaluated in the laboratory. Snails used belonged to the size-classes £ 3.0, 3.1 –5.0, 5.1 –7.0 and 7.1 –9.0 mm in shell height, using them both separately and together (mixed) in combinations. In each experiment lasting 24 h a single leech belonging to the size-classes 2.0 –3.9, 4.0 –5.9, 6.0 –7.9, 8.0 – 9.9 and 10.0 –11.9 mm in length was used. Except the 4.0 –5.9 mm size-class, leeches were able to capture and kill P. bridgesii irrespective of latter’s size; the predation, however, was confined to snails £ 3.0 mm. The rate of predation varied with the size of the predator and the prey, and a leech was able to kill a maximum of three snails per day. In India, in nature G. weberi feeds mostly on the pulmonate snail, Lymnaea (Radix) luteola. Experimental studies, however, revealed that G. weberi prefers the snails P. bridgesii and L .( R) luteola at the same rate from amongst the many other either less or not-preferred native operculate and non-operculate snails.