Cold Tolerance and Physiological Response of Natural Overwintering Pomacea canaliculata in South China.

Pomacea canaliculata (Lamarck 1822), a freshwater gastropod indigenous to lower Del Plata Basin of Argentina, has become the most destructive and invasive rice pests in south China since its introduction in the 1980s. In Guangdong, the main production areas for double rice, most of P. canaliculata overwinter in paddy field ditches after late-rice harvesting in mid-November and diapause to temporarily to avoid the damaging effects of extreme low temperatures. This pest aroused from diapause and migrated to the paddy field after early-rice reviving in next late March. Overwintering and cold tolerance of natural P. canaliculata have a non-negligible impact on population dynamics and distribution in the following year. We tested the supercooling capability, levels of cryoprotectant synthesis, activity of antioxidant defense system (antioxidant enzymes and reduced glutathione), and degree of oxidative damage (concentration of malondialdehyde as an index of lipid peroxidation) monthly, using natural P. canaliculata samples with a size-gender structure (i.e., juveniles, female, and male adults) from experimental ponds during the period of mid-November to the following April. P. canaliculata survived the winter with a monthly death rate of 7%-16.5% in coldest January. The supercooling point (SCP) of overwintering P. canaliculata decreased initially before increasing subsequently with monthly changes in water temperature. P. canaliculata accumulated a high glycogen content before December, which depleted towards the end of January, while lipid content reached peak in January and depleted since February. Activity of antioxidant defense system of P. canaliculata exhibited significant monthly differences and showed relatively higher size heterogeneity than monthly variations. The results contribute to the knowledge of adaptability in overwintering P. canaliculata and help to understand the mechanism of the invasive success of this species.