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, 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
Mature cunner from combined men and women was caught which have hoop barriers when you look at the summer 2013 in the Conception Bay (47°37?42? Letter, 52°51?31? W), Newfoundland, Canada. Brand new seafood have been relocated to carrying tanks at Sea Sciences Center (OSC), Art gallery School out-of Newfoundland, given circulate-courtesy, temperature-managed seawater (8–10°C) and you will met with a winter season photoperiod (eleven L : 13 D). The seafood was basically provided to satiation weekly which have chopped herring.
Teenager cunner out-of mixed sexes was basically the fresh new 2013 youngsters out-of nuts-stuck parents out-of Placentia Bay (47°42?47? N, 53°58?06? W) and you may Conception Bay, Newfoundland. Spawning, hatching and rearing took place from the OSC at the fifteen°C and you may several L : several D photoperiod. Three months just Spanisch Dating kostenlos before tests, juveniles was in fact moved to carrying tanks, supplied with flow-as a consequence of, temperature-regulated seawater (8–10°C) lower than a winter photoperiod (eleven L : 13 D), and you will given dead pellets (Gemma; Skretting, St Andrews, NB, Canada).
2. Question and methods
An eleven L : 13 D photoperiod was used in the research as it happen inside southeastern Newfoundland, when cunner is actually effective however, getting ready to go into dormancy (October; water temperature: approx. 9°C and cooling) or in cold weather dormancy (February; approx. 0°C) [31–33]. Tests was in fact conducted ranging from , when you look at the normal Newfoundland dormancy several months (November–June) .