The effects of temperature acclimation and acute temperature variation on oxygen consumption were determined for the pleurocerid snail Lithasia obovata (Say, 1829), a prosobranch restricted to the Ohio River and its tributaries' main stems. Snails were divided into two treatment groups and acclimated to constant temperatures (either 15 or 25 °C). Following acclimation, oxygen consumption rates for each animal were recorded at both 15 and 25 °C. Oxygen consumption rates did not differ between the two treatments at either temperature. Lithasia obovata exhibits no metabolic temperature compensation, as determined by acclimation Q10 (Q10acc). Because of the thermal inertia of the Ohio River (which does not change more than 1 °C day1), L. obovata is not exposed to rapid, large changes in water temperature and, thus, has little need for adjusting to short-term changes in ambient temperatures. We then examined the published literature and compared the acute Q10 and Q10acc values of L. obovata and other freshwater prosobranch snails to those of freshwater pulmonate snails. Acute Q10 and Q10acc values for pulmonates are lower than those exhibited by L. obovata and other prosobranchs; this result suggests that pulmonates have a greater compensatory capacity in response to both seasonal and diurnal temperature fluctuations. In addition, we compared the current geographic ranges of both gastropod groups in North America. Many pulmonates currently have considerably larger geographic ranges. Larger geographic ranges and greater compensatory capacities are important attributes in light of anticipated climate change impacts on freshwater ecosystems. Our results suggest that compared to pulmonates, North American freshwater prosobranchs generally are more at risk from additional environmental stresses arising from a warmer climate.
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Vol. 34 • No. 1