However, the fresh new it is possible to part off behavioural modulation out of kcalorie burning from inside the inactive fishes might have been skipped

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 below approximately 5°C, including when fish are at rest (i.e. at their SMR at night https://datingranking.net/it/siti-web-erotici/, 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) Animals

Adult cunner from blended men and women was basically seized which have hoop traps within the summer 2013 during the Conception Bay (47°37?42? Letter, 52°51?31? W), Newfoundland, Canada. The new fish was in fact transferred to holding tanks at the Ocean Sciences Middle (OSC), Memorial School off Newfoundland, supplied with disperse-by way of, temperature-managed seawater (8–10°C) and you may met with a cold weather photoperiod (eleven L : thirteen D). The newest seafood was fed to satiation weekly having sliced herring.

Teenager cunner away from mixed sexes were brand new 2013 offspring regarding crazy-stuck parents off Placentia Bay (47°42?47? N, 53°58?06? W) and Conception Bay, Newfoundland. Spawning, hatching and rearing happened at OSC from the 15°C and you may several L : several D photoperiod. 90 days just before tests, juveniles was basically gone to live in carrying tanks, given disperse-because of, temperature-controlled seawater (8–10°C) lower than a wintertime photoperiod (11 L : 13 D), and you will provided dead pellets (Gemma; Skretting, St Andrews, NB, Canada).

2. Topic and techniques

An enthusiastic eleven L : thirteen D photoperiod was applied regarding the investigation whilst takes place for the southeastern Newfoundland, when cunner is active but getting ready to enter into dormancy (October; water temperature: approx. 9°C and you may air conditioning) or perhaps in cold temperatures dormancy (February; approx. 0°C) [31–33]. Tests was in fact used between , within the typical Newfoundland dormancy several months (November–June) .