LEARNED PREDATOR RECOGNITION IN A FRESHWATER SNAIL, POMACEA CANALICULATA

The involvement of associative learning in predator recognition has not been clear in aquatic invertebrates, including molluscs, due to confounding effects of sensitization. The freshwater apple snail, Pomacea canaliculata, displays an alarm response (crawling above the waterline) when exposed to crushed conspecifics or some predators. We conducted two series of experiments to investigate whether the apple snail learns to avoid predators. In the first experiment, hatchlings were conditioned simultaneously to crushed conspecifics and either a live carp, Cyprinus carpio, or a turtle, Chinemys reevesii, and subsequently exposed to the same predator without crushed conspecifics. Irrespective of the predator species used, the alarm response was significantly higher in conditioned snails than in unconditioned snails. Thus, the snail is able to avoid predators by learning, in a broad sense. In the second experiment, designed to distinguish associative learning from sensitization, we conditioned hatchlings to crushed conspecifics and either a carp or a turtle. The hatchlings were subsequently exposed to one or other of the predators. Hatchlings that were conditioned to a predator displayed significantly higher alarm response when later exposed to the same predator than another predator, suggesting that the snail can recognize predators by associative learning.