Cope’s gray treefrog Dryophytes chrysoscelis maintains cellular integrity during freezing by adjusting membrane composition and by accumulating cryoprotective compounds
Elizabeth Evans Yokum
Only a few species of vertebrate animals can survive seasonal bouts of cold temperatures by tolerating repeated whole-body freezing and thawing. Of this unique groups, Cope’s gray treefrog Dryophytes chrysoscelis, can survive freezing and thawing of up to 70% of its body fluids. The objective of this study is to investigate two possible mechanisms that may contribute to cellular freeze competence: changes to lipid composition of the cell membrane, and synthesis and distribution of molecules that protect against freeze-induced damage (cryoprotectants). It is hypothesized that cells modify the lipid (phospholipid and cholesterol) content of their membranes in ways that affect membrane fluidity and thereby optimize cell function at cold temperatures. Preliminary 1H NMR analysis indicates that phospholipid distribution, fatty acid composition, and cholesterol all vary between warm and cold acclimated groups in membranes prepared from liver tissue. It is further hypothesized that glycerol, glucose, and urea serve as cryoprotectants in gray treefrogs; these compounds can help to maintain cellular fluid volumes, prevent intracellular freezing, and support molecular structures in freeze tolerant animals. Compared to animals that were cold acclimated only, accumulation of cryoprotectants is expected to increase in animals frozen and thawed once (single freeze-thaw) and further increase in animals frozen and thawed three times (repeated freeze-thaw). Results indicate that plasma, liver, and skeletal muscle concentrations of glycerol and glucose are elevated in both groups of frozen and thawed treefrogs, but no significant differences were detected between the two groups. Both membrane lipid remodeling and cryoprotectant accumulation likely contribute to cellular and organismal freeze competence in D. chrysoscelis. Further investigation of these (and other) mechanisms will help to elucidate the physiological underpinnings of vertebrate freeze tolerance.
Jeremy M. Erb, Carissa M. Krane, Matthew W. Wascher
Primary Advisor's Department
Stander Symposium project, College of Arts and Sciences
United Nations Sustainable Development Goals
"Cope’s gray treefrog Dryophytes chrysoscelis maintains cellular integrity during freezing by adjusting membrane composition and by accumulating cryoprotective compounds" (2022). Stander Symposium Projects. 2447.