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 http://datingranking.net/local-hookup/albuquerque 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 out-of combined men and women was basically grabbed that have hoop traps during the june 2013 during the Conception Bay (47°37?42? Letter, 52°51?31? W), Newfoundland, Canada. This new fish were relocated to carrying tanks during the Sea Sciences Centre (OSC), Memorial School away from Newfoundland, given circulate-through, temperature-controlled seawater (8–10°C) and you may confronted with a winter months photoperiod (11 L : thirteen D). Brand new fish had been fed to help you satiation regular with sliced herring.
Juvenile cunner off blended genders was the 2013 young ones out of wild-trapped moms and dads from Placentia Bay (47°42?47? Letter, 53°58?06? W) and you may Conception Bay, Newfoundland. Spawning, hatching and you may rearing occurred during the OSC on fifteen°C and a dozen L : 12 D photoperiod. Three months prior to studies, juveniles have been relocated to holding tanks, supplied with flow-as a consequence of, temperature-regulated seawater (8–10°C) around a cold temperatures photoperiod (eleven L : 13 D), and you will fed lifeless pellets (Gemma; Skretting, St Andrews, NB, Canada).
dos. Procedure and techniques
An eleven L : thirteen D photoperiod was used on the investigation since it occurs from inside the southeastern Newfoundland, whenever cunner try effective but getting ready to enter dormancy (October; sea temperatures: approx. 9°C and air conditioning) or in cold temperatures dormancy (February; approx. 0°C) [31–33]. Studies was used between , in the regular Newfoundland dormancy months (November–June) .