Abstract
Potamopyrgus antipodum has been found in thermal waters only at temperatures below 28°c. Experimental work indicates that 28°c represents the temperature at which snail activity is first curtailed when temperatures are progressively raised. Although the reduction in available oxygen found at high temperatures appears to have some effect on snail activity, the increase in temperature itself is the major factor depressing activity and consequently limiting snail distribution. No difference in the temperature at which activity is reduced has been found between snails living at different environmental temperatures. When temperature was raised 1°c/24 hours, heat death occurred at 30–32°c.