Yet not, the fresh new you can easily part away from behavioural modulation out of metabolism in dormant 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, 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 men and women have been caught with hoop traps in the summer 2013 for the Conception Bay (47°37?42? N, 52°51?31? W), Newfoundland, Canada. The latest fish have been transferred to carrying tanks within Ocean Sciences Hub (OSC), Art gallery College out-of Newfoundland, given flow-as a consequence of, temperature-regulated seawater (8–10°C) and you may neue spanische Singles Dating Seiten confronted with a wintertime photoperiod (11 L : thirteen D). Brand new fish was in fact provided to help you satiation weekly having chopped herring.

Juvenile cunner from blended men and women was the brand new 2013 kids regarding insane-trapped mothers regarding Placentia Bay (47°42?47? N, 53°58?06? W) and you may Conception Bay, Newfoundland. Spawning, hatching and you can rearing happened from the OSC at fifteen°C and you can several L : several D photoperiod. Three months ahead of experiments, juveniles was indeed moved to carrying tanks, provided with disperse-as a result of, temperature-regulated seawater (8–10°C) significantly less than a cold temperatures photoperiod (11 L : 13 D), and you may fed lifeless pellets (Gemma; Skretting, St Andrews, NB, Canada).

2. Topic and techniques

A keen eleven L : thirteen D photoperiod was applied from the investigation as it happens for the southeastern Newfoundland, whenever cunner is productive however, preparing to get into dormancy (October; sea temperatures: approx. 9°C and you will cooling) or even in wintertime dormancy (February; approx. 0°C) [31–33]. Experiments was in fact presented ranging from , during the typical Newfoundland dormancy period (November–June) .