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 [10,18]. 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, 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
Mature cunner away from blended genders was indeed seized having hoop barriers for the june 2013 when you look at the Conception Bay (47°37?42? N, 52°51 https://datingranking.net/local-hookup/savannah/?31? W), Newfoundland, Canada. The fish was gone to live in holding tanks within Ocean Sciences Center (OSC), Art gallery College away from Newfoundland, provided with disperse-thanks to, temperature-regulated seawater (8–10°C) and you can met with a cold weather photoperiod (11 L : 13 D). The new fish were given in order to satiation weekly which have sliced herring.
Teenager cunner from combined men and women was indeed the newest 2013 offspring out-of insane-stuck parents out-of Placentia Bay (47°42?47? Letter, 53°58?06? W) and you will Conception Bay, Newfoundland. Spawning, hatching and you will rearing taken place at the OSC on 15°C and twelve L : several D photoperiod. Three months ahead of tests, juveniles was basically gone to live in holding tanks, supplied with flow-through, temperature-controlled seawater (8–10°C) lower than a wintertime photoperiod (eleven L : 13 D), and you will given inactive pellets (Gemma; Skretting, St Andrews, NB, Canada).
dos. Topic and techniques
An enthusiastic 11 L : thirteen D photoperiod was applied on analysis because happens inside the southeastern Newfoundland, whenever cunner are productive however, preparing to get into dormancy (October; ocean temperature: approx. 9°C and you can air conditioning) or in winter season dormancy (February; approx. 0°C) [31–33]. Studies have been presented ranging from , inside normal Newfoundland dormancy several months (November–June) .