Environmental factors affecting the increase of cold hardiness in the apple snail Pomacea canaliculata (Gastropoda: Ampullariidae)

Abstract

The cold hardiness of the apple snail, Pomacea canaliculata, which infests Japanese paddy fields, shows seasonal fluctuations. We investigated the environmental factors that influence this cold hardiness. Snails showed a great increase in cold hardiness under cold acclimation, when they were kept in water or wrapped in a dry or moist towel. Snails incubated at 25°C in a dry or moist towel also showed a certain increase in cold hardiness. Field-collected snails that were given sufficient food before incubation at 25°C in water showed an increase in cold hardiness, but starved snails did not. Photoperiod had no influence on cold hardiness. We compared the factors increasing cold hardiness among molluscs inhabiting different environments.