title: Metabolic depression in cunner (Tautogolabrus adspersus) is influenced by ontogeny, and enhances thermal tolerance.
abstract: To examine the effect of ontogeny on metabolic depression in the cunner (Tautogolabrus adspersus), and to understand how ontogeny and the ability to metabolically depress influence this species' upper thermal tolerance: 1) the metabolic rate of 9°C-acclimated cunner of three size classes [0.2-0.5 g, young of the year (YOY); 3-6 g, small; and 80-120 g, large (adult)] was measured during a 2°C per day decrease in temperature; and 2) the metabolic response of the same three size classes of cunner to an acute thermal challenge [2°C h(-1) from 10°C until Critical Thermal Maximum, CTMax] was examined, and compared to that of the Atlantic cod (Gadus morhua). The onset-temperature for metabolic depression in cunner increased with body size, i.e. from 5°C in YOY cunner to 7°C in adults. In contrast, the extent of metabolic depression was ∼80% (Q10 = ∼15) for YOY fish, ∼65% (Q10 = ∼8) for small fish and ∼55% (Q10 = ∼5) for adults, and this resulted in the metabolic scaling exponent (b) gradually increasing from 0.84 to 0.92 between 9°C to 1°C. All size classes of cunner had significantly (approximately 60%) lower routine metabolic rates at 10°C than Atlantic cod. However, there was no species' difference in the temperature-induced maximum metabolic rate, and this resulted in factorial metabolic scope values that were more than two-fold greater for cunner, and CTMax values that were 6-9°C higher (∼21 vs. 28°C). These results: 1) show that ontogeny influences the temperature of initiation and the extent of metabolic depression in cunner, but not O2 consumption when in a hypometabolic state; and 2) suggest that the evolution of cold-induced metabolic depression in this northern wrasse species has not resulted in a trade-off with upper thermal tolerance, but instead, an enhancement of this species' metabolic plasticity.
authors.affiliation: Department of Ocean Sciences, Memorial University of Newfoundland, St. John's, Newfoundland and Labrador, Canada.
authors.forename: Nick I
authors.initials: NI
authors.lastname: Kelly
authors.affiliation: Department of Ocean Sciences, Memorial University of Newfoundland, St. John's, Newfoundland and Labrador, Canada.
authors.forename: Abdullah
authors.initials: A
authors.lastname: Alzaid
authors.affiliation: Department of Ocean Sciences, Memorial University of Newfoundland, St. John's, Newfoundland and Labrador, Canada.
authors.forename: Gordon W
authors.initials: GW
authors.lastname: Nash
authors.affiliation: Department of Ocean Sciences, Memorial University of Newfoundland, St. John's, Newfoundland and Labrador, Canada.
authors.forename: A Kurt
authors.initials: AK
authors.lastname: Gamperl
mesh_terms: D000064:Acclimatization / Q000502:physiology*; D000818:Animals; D003080:Cold Temperature; D004734:Energy Metabolism / Q000502:physiology*; D004777:Environment; D048389:Gadus morhua / Q000378:metabolism / Q000502:physiology*; D006339:Heart Rate / Q000502:physiology; D006358:Hot Temperature; D010101:Oxygen Consumption / Q000502:physiology*; D010473:Perciformes / Q000378:metabolism / Q000502:physiology*; D012119:Respiration; D015996:Survival Rate