Thermal Tolerance of Japanese Mystery Snails

Abstract

One aspect of climate change is an increase in global temperatures, which can impact the range and spread of
organisms. Therefore, studying the heat tolerance of invasive species can help predict their spread under a changing
climate. Japanese Mystery Snails (Heterogen japonica) are invasive freshwater snails from Japan that are highly
adaptable, rapidly reproduce, and lack predators, which are all traits which make them successful invaders. We collected
Japanese Mystery Snails from three different sites in Virginia and Maryland. We then placed 20 individuals and broods
from 10 females per site into individual containers in three temperature treatments (35℃,40℃,45℃) and a control on a
laboratory bench (25℃) in incubators for seven days. Snails were first acclimated to the treatment temperatures at 1℃/
24 hours to prevent thermal shock. We then observed snails daily for mortality for seven days. Results show that the
maximum temperature H. japonica can tolerate for a week is between 35℃ and 40℃. At 45℃, there was 100%
mortality rate after only 24 hours for both juveniles and adults. At 40℃, there was 100% mortality on the first and
second day for juveniles and adults, respectively. At 35℃, the snails could survive for the full seven days. Heterogen
japonica’s tolerance is higher temperatures may indicate an advantage and allow for further spread. Their relatively high
water temperature tolerance, along with other aspects of their biology, suggests that expansion into more southern
water bodies in the United States is possible and managers should be alert.