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 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 hookup Anchorage 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) Pets
Mature cunner from blended men and women were seized which have hoop traps into the summer 2013 during the Conception Bay (47°37?42? Letter, 52°51?31? W), Newfoundland, Canada. This new fish was in fact moved to holding tanks on Sea Sciences Hub (OSC), Memorial University from Newfoundland, supplied with disperse-because of, temperature-regulated seawater (8–10°C) and confronted with a wintertime photoperiod (eleven L : 13 D). Brand new seafood have been fed to satiation once a week with sliced herring.
Teenager cunner from blended men and women had been brand new 2013 little ones regarding insane-stuck moms and dads away from Placentia Bay (47°42?47? N, 53°58?06? W) and you will Conception Bay, Newfoundland. Spawning, hatching and you can rearing occurred at the OSC from the 15°C and 12 L : twelve D photoperiod. 90 days just before experiments, juveniles were transferred to carrying tanks, provided with disperse-through, temperature-regulated seawater (8–10°C) lower than a winter season photoperiod (eleven L : thirteen D), and you will fed dead pellets (Gemma; Skretting, St Andrews, NB, Canada).
2. Point and methods
A keen eleven L : thirteen D photoperiod was used on analysis because it takes place inside the southeastern Newfoundland, whenever cunner is productive but preparing to enter dormancy (October; water temperatures: approx. 9°C and cooling) or perhaps in winter dormancy (February; approx. 0°C) [31–33]. Experiments was held anywhere between , from inside the normal Newfoundland dormancy several months (November–June) .
