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 Billings free hookup 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) Pet

Adult cunner out-of blended sexes was basically caught having hoop traps from inside the summer 2013 for the Conception Bay (47°37?42? Letter, 52°51?31? W), Newfoundland, Canada. The new fish had been transferred to carrying tanks at the Ocean Sciences Centre (OSC), Art gallery College of Newfoundland, supplied with disperse-owing to, temperature-managed seawater (8–10°C) and you will confronted by a cold temperatures photoperiod (11 L : thirteen D). The fresh new seafood was basically given so you’re able to satiation weekly with sliced herring.

Teenager cunner of combined men and women was the fresh new 2013 children out of wild-stuck parents out-of Placentia Bay (47°42?47? N, 53°58?06? W) and Conception Bay, Newfoundland. Spawning, hatching and you will rearing taken place during the OSC during the fifteen°C and you can a dozen L : 12 D photoperiod. Three months in advance of experiments, juveniles had been moved to carrying tanks, provided with disperse-using, temperature-regulated seawater (8–10°C) below a winter season photoperiod (11 L : thirteen D), and you will provided deceased pellets (Gemma; Skretting, St Andrews, NB, Canada).

dos. Issue and methods

An eleven L : thirteen D photoperiod was utilized from the analysis as it happen in the southeastern Newfoundland, whenever cunner is energetic however, preparing to enter dormancy (October; water heat: approx. 9°C and you will cooling) or perhaps in winter months dormancy (February; approx. 0°C) [31–33]. Experiments have been presented between , for the normal Newfoundland dormancy several months (November–June) .