Effects of salinity stress on the oxygen consumption and ammonia excretion rates of the invasive fresh snail Pomacea canaliculata

Pomacea canaliculata (Lamark 1822) is one of the 100 worst alien invasive species in the world. To date, P. canaliculata snails have been mainly studied in freshwater areas, such as paddy fields, canals, ditches, rivers, and lakes, whereas there have been only a few studies on the potential risk of P. canaliculata spreading to salty water areas. In order to investigate the response differences of small, medium, and large P. canaliculata snails to salt stress, we determined the oxygen consumption rate and ammonia excretion rate of the three differently sized snails under five salinity treatments (0, 2.5, 5.0, 7.5, and 10.0 g·L^-1) using the hydrostatic method. The results showed that salinity, snail size, and their interactions had significant effects on the oxygen consumption and ammonia excretion rates of the snails (P < 0.001). The oxygen consumption and ammonia excretion rates of the studied snails reached a peak at 2.5 g·L^-1 salinity. However, between 2.5-10.0 g·L^-1 salinity, they gradually decreased as the salinity increased. There was a negative correlation between oxygen consumption rate or ammonia excretion rate, and the dry meat weight (oven-dried at 65℃ for 48 h) of the snails. The oxygen consumption rate and the ammonia excretion rate followed the order small snails > medium snails > large snails. The oxygen-nitrogen ratio (O/N) for P. canaliculata ranged from 5.80 to 30.46, reaching a peak when the salinity was 2.5 g·L^-1, and then gradually decreased as the salinity increased. There were no significant differences in the O/N among the three differently sized P. canaliculata snails compared to the control group when the salinity was 2.5-7.5 g·L^-1. This study showed that the snails could survive for a short period of time in a saline environment with a salinity below 7.5 g·L^-1.