Meeting Abstract
The Mountain Tailed Frog, Ascaphus montanus is a cryophile that is associated with permanent mountain streams in the Northwestern United States. Although unknown, adults likely overwinter in the fast moving streams, but to do so they would need to survive extended bouts of subzero temperatures. Previous work has described the frog’s ability to supercool to low temperatures and survive freezing. The purpose of this study was to determine tissue level indicators of freeze tolerance, namely cryoprotectant concentrations and wet mass. Winter acclimated frogs cooled from 2°C at 0.2°C h-1 and then held at -1°C until they spontaneously froze or had a small ice chip placed on their pack to inoculate freezing after 3 days. After being held at -1 °C for seven days, they were then removed, double pithed and the gracilis and gastrocnemius muscles, heart, and liver were removed on ice. Water content of the liver was determined after a portion of the tissue was blotted dry, weighed and dried in an oven at 60 C°. Water content significantly increased after freezing. Urea and Glycerol concentration were below detectable limits of the assay. Glucose concentrations did not change in response to freezing but were elevated compared to acclimatized individuals of other species. Based on the known literature and previous work it seems that this species can survive in high sub-zero temperatures found in its aquatic environment. These data suggest that the frogs may survive freezing in conditions likely found in their stream habitat and may use a combination of supercooling and freeze tolerance to overwinter.
