Physiology of the Apple Snail Pomacea maculata: Aestivation and Overland Dispersal

Abstract

Apple snails, in the genus Pomacea, have gained considerable notoriety for their impact on invaded habitats. Louisiana is currently under invasion by Pomacea maculata, which represents a potential threat to the state's valuable plants and cash crops. Insight into the physiology of the invasive snail may assist in developing control measures and enhance our understanding of the processes of adaptation and coevolution that accompany introductions. This paper addresses the capacity, extent, and means by which aquatic apple snails in Louisiana tolerate aerial exposure, as well as the factors that contribute to desiccation tolerance in P. maculata. Invasive P. maculata in Louisiana survived about 10 months of aestivation before 50% mortality was incurred, during which body mass was reduced by only about 30%; mortality and loss of body mass were positively correlated during aestivation. Size affects the loss of body mass in snails under 20 grams. Relative humidity interfered with the induction of aestivation, but it did not significantly affect the loss of body mass. Invasive apple snails in Louisiana also demonstrated the inclination and ability to sustain travel for at least three hours over dry land, at a rate of two meters per hour. The results of this study show that P. maculata is well adapted for survival in the absence of water. The ability to sustain travel over land and to endure long periods of aerial exposure suggests that the dry-down of infested bodies of water would not significantly impact populations of P. maculata in Louisiana.

Keywords: C, control; LT50, time required to reach 50% mortality; O, operculum; RH, relative humidity; S, shell.