To investigate the puzzle of whether metabolic rate depression is involved in winter dormancy in fishes, we studied the cunner (Tautogolabrus adspersus), an abundant western North Atlantic wrasse. Like other temperate wrasses [16,29,30], cunner are winter-dormant: they seek refuge within the substrate and become inactive when the ocean cools below approximately 5°C in autumn, and emerge at approximately 5°C the following early summer [31–33]. This winter dormancy in cunner has been associated with a large decrease in metabolic rate that occurs rapidly (within hours) below 5°C and is maintained over the winter [ten,18]. The Q10 of metabolic rate over the transition from active to dormant temperatures has been reported to be greater than 10 in cunner, as in other winter-dormant wrasses , whereas at warmer active temperatures, the Q10 is between 2 and 3, a typical value for fishes [10,34]. Based on this, and consistent with simultaneous reductions in tissue protein synthesis and suppression of appetite and digestion [33,36,37], metabolic rate depression has been implicated as a central component of winter dormancy in cunner. Using cunner as a model, we investigated the hypothesis that the mechanism underlying the energy savings (i.e. low metabolic rate) of winter dormancy in fishes is not metabolic rate depression, but rather a behavioural reduction in activity. We carried out three experiments Ann Arbor hookup website using automated optical respirometry to allow for multi-day, high-resolution monitoring of whole-animal oxygen consumption rate ( ; a proxy for metabolic rate) even at frigid temperatures. In experiment 1, we examined the influence of acute exposure to low winter temperature on the diel cycle of metabolic rate. In experiment 2, we examined the effect of acute exposure to darkness and low temperature, which are characteristic of the winter refuge, on the diel cycle of metabolic rate and spontaneous activity (measured simultaneously). In experiment 3, we investigated whether chronic acclimation to low temperature can trigger a metabolic rate depression. If metabolic rate depression is involved in winter dormancy, we predicted that the thermal sensitivity (i.e. Q10) of metabolic rate would remain high at all times when cooled below approximately 5°C, including when fish are at rest (i.e. at their SMR at night, as cunner are active during the day ). Alternatively, if reduced activity explains energy savings under winter dormancy, then the thermal sensitivity of metabolic rate during resting periods would indicate physico-chemical effects alone (Q10 ? 2–3) regardless of acute or chronic cold exposure and, in experiment 2, variation in activity would largely explain variation in metabolic rate.
(a) Dogs
Adult cunner out-of combined sexes had been caught that have hoop traps when you look at the summer 2013 inside the Conception Bay (47°37?42? N, 52°51?31? W), Newfoundland, Canada. This new seafood have been moved to carrying tanks within Water Sciences Hub (OSC), Memorial College away from Newfoundland, provided with disperse-because of, temperature-controlled seawater (8–10°C) and you will exposed to a winter photoperiod (eleven L : 13 D). The seafood have been given to help you satiation regular with chopped herring.
Juvenile cunner from combined men and women have been the 2013 kids out-of crazy-caught moms and dads of Placentia Bay (47°42?47? Letter, 53°58?06? W) and you can Conception Bay, Newfoundland. Spawning, hatching and you may rearing took place during the OSC at fifteen°C and you may twelve L : several D photoperiod. 3 months in advance of tests, juveniles was indeed transferred to holding tanks, supplied with circulate-through, temperature-controlled seawater (8–10°C) less than a cold weather photoperiod (11 L : thirteen D), and you can given dry pellets (Gemma; Skretting, St Andrews, NB, Canada).
2. Topic and techniques
A keen eleven L : thirteen D photoperiod was applied regarding the data as it happen from inside the southeastern Newfoundland, whenever cunner is effective but preparing to go into dormancy (October; ocean temperature: approx. 9°C and you may cooling) or in winter season dormancy (February; approx. 0°C) [31–33]. Studies was indeed conducted between , in the normal Newfoundland dormancy months (November–June) .