Assassins and apples : the environmental constraints of two snails that threaten Australian aquatic systems

Abstract

Context : Alien freshwater snails pose a substantial risk to Australian native aquatic biota. Aims : This study aims to determine the thermal and salinity ranges of two introduced species within Australia, Pomacea sp. and Anentome sp., to facilitate predictions of their potential geographic range should they become widely established. Methods : Laboratory tests were conducted to assess behavioural responses of snails to altered temperature or salinity after different acclimation regimes. Key results : After acclimation at 25°C, Pomacea sp. had a median activity range of 13.5-38°C and Anentome sp. of 12-38.5°C. Higher acclimation temperatures produced observable effects, whereas lower acclimation temperatures did not. Salinity tolerances differed, with Pomacea sp. remaining active at up to 8 parts per thousand (ppt) (after acclimation at 25°C), with acclimation at 20°C resulting in a lower salinity tolerance. By contrast, Anentome sp. snails were active at up to 5 ppt after low salinity acclimation, demonstrating enhanced salinity tolerance compared with non-salinity acclimations. Conclusions : These results showed that both snails are capable of surviving temperatures and salinities that would allow invasion into subtropical and warm-temperate Australian aquatic systems. Implications : Free from the constraints of natural predators, competitors, and parasites, these snails should be of great concern to biosecurity agencies in Australia.