ECOLOGICAL PHYSIOLOGY OF OVERWINTERING IN HATCHLING BLANDING’S TURTLES (Emydoidea blandingii): INSIGHTS INTO ANOXIA TOLERANCE AND FREEZE TOLERANCE
Abstract (Summary)These studies address the ability of hatchling Blanding’s turtles (Emydoidea blandingii Holbrook, 1838) to overwinter in terrestrial and aquatic environments. Currently, it is not known where these hatchlings overwinter or how they survive different environmental stresses in each habitat. In addition, this is the first on antioxidant responses to freezing and anoxia in hatchling turtles, and survival times during freezing and anoxia among species of turtles. First, cold-hardiness and dehydration resistance were studied to determine if hatchlings could overwinter in a terrestrial environment. Hatchlings were susceptible to dehydration and could not rely on supercooling because of a lack of resistance to inoculation. However, hatchlings had a well developed ability to survive freezing at -3.5°C for 72 h. If hatchlings overwinter in terrestrial environments, they probably overwinter in moist areas that limit dehydration and promote freezing at a high sub-zero temperature. The second study examined whether hatchling Blanding’s turtles could overwinter in aquatic habitats. The average survival time was 13 d for hatchlings submerged in anoxic water. Approximately one third of the hatchlings died during 75 d of normoxic submergence, but the cause of mortality was unclear. Mortality during hypoxic submergence was likely caused by metabolic acidosis, which resulted from accumulated lactate. Unlike the case with adult turtles, our hatchlings did not increase plasma calcium and magnesium, nor did they sequester lactate within the shell. Our results suggest that hatchling E. blandingii are not particularly well suited to hibernation in hypoxic aquatic habitats. The third study examined relationships between anoxia tolerance and freeze tolerance among several species of hatchling turtles. Freeze tolerance capacity was not necessarily associated with anoxia tolerance. Although lactate concentrations increased during freezing, they were much lower than the concentrations reached during anoxia. Also, liver catalase activity increased in most species following anoxia and freezing exposure, which suggests that constitutive activities of antioxidants are probably insufficient to metabolize increased reactive oxygen species formation during reoxygenation. In conclusion, although a functional anoxia develops during freezing, the accumulation of lactate does not limit survival.
School Location:USA - Ohio
Source Type:Master's Thesis
Date of Publication:01/01/2004