Meeting Abstract
Winter dormancy (an inactive, fasting, slow metabolism state) is used by certain fishes to endure the frigid and food-poor winter and persist at poleward latitudes. However, little is known about the mechanisms and drivers of winter dormancy. We hypothesized that winter dormancy arises because of severe constraints on physiological performance at frigid temperatures. To test this, we measured the thermal sensitivity of fitness-linked physiological performance (burst swimming, metabolic rate, and aerobic scope) and related biochemical characteristics (metabolite levels and enzyme activities) in the winter-dormant cunner (Tautogolabrus adspersus), which enters dormancy below 7.4°C on average. Performance was measured after acute exposure to 2-26°C and after acclimation (≥5 weeks) to 2-14°C. As expected, performance declined with cooling below the thermal optimum in both exposure groups. In acutely exposed fish, the thermal sensitivity of all performance traits was greater below the dormancy threshold temperature than above, suggesting a major constraint of cold. However, at 2°C, acclimated cunner had greater performance and lower thermal sensitivity compared to acutely exposed cunner (Q10 of 1.1-2.0 vs. 3.9-4.3 between 8-2°C, respectively). Thus, dormant cunner show partial compensation of swimming and aerobic performance in winter cold temperatures, similar to cold-active species. However, compensation of metabolic enzyme activities did not underlie the whole-animal performance compensation. We conclude that thermal constraints on anaerobic exercise and aerobic performance are not major drivers of winter dormancy in cunner.
