Implications of aquatic hypothermia for dive performance in the semi-aquatic muskrat, Ondatra zibethicus.

摘要

The “adaptive hypothermia” hypothesis predicts that hypothermia, via the Q₁₀ effect, reduces whole-body oxygen consumption by depressing metabolism of cooled tissues. This hypothesis has gained prevalence in large part due to published reports of dramatic body cooling in free-ranging animals foraging in cold water. Because the evidence to date implicating hypothermia as an oxygen sparing strategy is largely circumstantial, I undertook an investigation of the influences of mild hypothermia on the semi-aquatic muskrat diving voluntarily in a laboratory setting.; Pre-chilling elicited no overt behavioural changes to diving in adult muskrats. In fact, the only impact of hypothermia on the aquatic behaviour of adults was a tendency for hypothermic individuals to spend more total time immersed in cold water (P = 0.006).; Post-dive excess VO₂ was higher for pre-chilled than for normothermic muskrats in short dives only. This discrepancy was eliminated for longer (2 min) dives, suggesting that a comparable or maximal dive response was achieved in both groups during longer dives, regardless of T_b.; In the youngest cohort tested (200–400 g), hypothermia was associated with elevated VO₂ and decreased diving during continuous immersion. (Abstract shortened by UMI.)