నైరూప్య

Demography of Thiara riqueti (Grateloup) (Mesogastropoda, Thiaridae) in Response to Temperature and Salinity

Jiang Ping Wang, Chung Yao Cheng, Hsin Chi and Yih Tsong Ueng

Both temperature and salinity significantly affected the demographic traits of the snail Thiara riqueti (Grateloup) (Mesogastropoda, Thiaridae). At 5% salinity, snails survived less than a week and no reproduction occurred. At 10ºC, the mean longevity of the snail was about 10 days and no reproduction was observed. At 18ºC, total longevity ranged from 4.1 to 19.8 weeks, and only minor reproduction was observed at 1% salinity. The longevity at 10 and 18ºC, however, is sufficient for the snail to survive the short, mild winter period in Taiwan. At 25ºC and 30ºC, reproduction was observed at all salinities (except at 25ºC and 0.2% salinity). At 30ºC, the intrinsic rates of increase were  0.1236, 0.1502, 0.1081 and 0.094 for salinity 1.0%, 2.0%, 2.5% and 3.0%, respectively. The net reproductive rate at 30ºC ranged from 0.92 to 56.3 offspring per individual. Although T. riqueti was reported as a freshwater snail, our results indicate that it is euryhaline in Taiwan.