Meeting Abstract
Winter dormancy (an inactive, fasting, slow metabolism state) is used by certain fishes to endure the frigid and food-poor winter and thus persist at poleward latitudes. However, little is known about the mechanisms and drivers of winter dormancy. Temperature affects physiological and biochemical processes, with performance being facilitated at temperatures close to the thermal optimum (Topt) and constrained at the thermal extremes. We hypothesized that winter dormancy is a response to constraints of low temperature on physiological performance. We measured the thermal sensitivity of three key physiological performance metrics (burst swim performance, maximum metabolic rate, and aerobic scope) in the winter-dormant cunner (Tautogolabrus adspersus), which we determined enters dormancy below 7.3±0.6°C. Performance was measured after (i) acute exposure to temperatures between 2-26°C or (ii) long-term acclimation (5+ weeks) to 2, 5, 8, 11, and 14°C. As expected, performance declined with cooling below the Topt in both exposure groups. In acutely exposed fish, the thermal sensitivity of performance was much greater below the dormancy threshold temperature than above, suggesting a major constraint of cold. However, at 2°C, acclimated cunner had greater performance compared to acutely exposed cunner; thermal sensitivity of acclimated fish was lower than acutely exposed fish (Q10 of 1.1-2.0 vs. 3.9-4.3 between 2-8°C, respectively). Thus, dormant cunner compensate for effects of winter cold on swimming and aerobic performance, similar to cold-active species. We conclude that thermal constraints on anaerobic swim performance and aerobic metabolism are not major drivers of winter dormancy in fishes.
