Repeatability of standard metabolic rate, active metabolic rate and aerobic scope in young brown trout during a period of moderate food availability.
ABSTRACT Standard metabolic rate (SMR) and active metabolic rate (AMR) are two fundamental physiological parameters providing the floor and ceiling in aerobic energy metabolism. The total amount of energy available within these two parameters confines constitutes the absolute aerobic scope (AAS). Previous studies on fish have found SMR to closely correlate with dominance and position in the social hierarchy, and to be highly repeatable over time when fish were provided an ad libitum diet. In this study we tested the temporal repeatability of individual SMR, AMR and AAS, as well as repeatability of body mass, in young brown trout (Salmo trutta L.) fed a moderately restricted diet (0.5-0.7% fish mass day⁻¹). Metabolism was estimated from measurements of oxygen consumption rate (M(.)(O₂)) and repeatability was evaluated four times across a 15-week period. Individual body mass was highly repeatable across the entire 15 week experimental period whereas residual body-mass-corrected SMR, AMR and AAS showed a gradual loss of repeatability over time. Individual residual SMR, AMR and AAS were significantly repeatable in the short term (5 weeks), gradually declined across the medium term (10 weeks) and completely disappeared in the long term (15 weeks). We suggest that this gradual decline in repeatability was due to the slightly restricted feeding regime. This is discussed in the context of phenotypic plasticity, natural selection and ecology.
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ABSTRACT: Measurements of aerobic scope [the difference between minimum and maximum oxygen consumption rate ( and , respectively)] are increasing in prevalence as a tool to address questions relating to fish ecology and the effects of climate change. However, there are underlying issues regarding the array of methods used to measure aerobic scope across studies and species. In an attempt to enhance quality control before the diversity of issues becomes too great to remedy, this paper outlines common techniques and pitfalls associated with measurements of , and aerobic scope across species and under different experimental conditions. Additionally, we provide a brief critique of the oxygen- and capacity-limited thermal tolerance (OCLTT) hypothesis, a concept that is intricately dependent on aerobic scope measurements and is spreading wildly throughout the literature despite little evidence for its general applicability. It is the intention of this paper to encourage transparency and accuracy in future studies that measure the aerobic metabolism of fishes, and to highlight the fundamental issues with assuming broad relevance of the OCLTT hypothesis.Journal of Experimental Biology 08/2013; 216(Pt 15):2771-2782. · 3.24 Impact Factor
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ABSTRACT: Full text available at http://jeb.biologists.org/lookup/doi/10.1242/jeb.082925 Metabolic rates of aquatic organisms are estimated from measurements of oxygen consumption rates (MO2) through swimming and resting respirometry. These distinct approaches are increasingly used in eco- and conservation physiology studies; however, few studies have tested whether they yield comparable results. We examined whether two fundamental MO2 measures, standard metabolic rate (SMR) and maximum metabolic rate (MMR), vary based on the method employed. Ten bridled monocle bream (Scolopsis bilineatus) were exercised using (1) a critical swimming speed (Ucrit) protocol, (2) a 15 min exhaustive chase protocol and (3) a 3 min exhaustive chase protocol followed by brief air exposure. Protocol (1) was performed in a swimming respirometer whereas protocols (2) and (3) were followed by resting respirometry. SMR estimates in swimming respirometry were similar to those in resting respirometry when a three-parameter exponential or power function was used to extrapolate the swimming speed-MO2 relationship to zero swimming speed. In contrast, MMR using the Ucrit protocol was 36% higher than MMR derived from the 15 min chase protocol and 23% higher than MMR using the 3 min chase 1 min air exposure protocol. For strong steady (endurance) swimmers, such as S. bilineatus, swimming respirometry can produce more accurate MMR estimates than exhaustive chase protocols because oxygen consumption is measured during exertion. However, when swimming respirometry is impractical, exhaustive chase protocols should be supplemented with brief air exposure to improve measurement accuracy. Caution is warranted when comparing MMR estimates obtained with different respirometry methods unless they are cross-validated on a species-specific basis.Journal of Experimental Biology 03/2013; · 3.24 Impact Factor
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ABSTRACT: Abstract Repeatability is an important concept in evolutionary analyses because it provides information regarding the benefit of repeated measurements and, in most cases, a putative upper limit to heritability estimates. Repeatability (R) of different aspects of energy metabolism and behavior has been demonstrated in a variety of organisms over short and long time intervals. Recent research suggests that consistent individual differences in behavior and energy metabolism might covary. Here we present new data on the repeatability of body mass, standard metabolic rate (SMR), voluntary exploratory behavior, and feeding rate in a semiaquatic salamander and ask whether individual variation in behavioral traits is correlated with individual variation in metabolism on a whole-animal basis and after conditioning on body mass. All measured traits were repeatable, but the repeatability estimates ranged from very high for body mass (R = 0.98), to intermediate for SMR (R = 0.39) and food intake (R = 0.58), to low for exploratory behavior (R = 0.25). Moreover, repeatability estimates for all traits except body mass declined over time (i.e., from 3 to 9 wk), although this pattern could be a consequence of the relatively low sample size used in this study. Despite significant repeatability in all traits, we find little evidence that behaviors are correlated with SMR at the phenotypic and among-individual levels when conditioned on body mass. Specifically, the phenotypic correlations between SMR and exploratory behavior were negative in all trials but significantly so in one trial only. Salamanders in this study showed individual variation in how their exploratory behavior changed across trials (but not body mass, SMR, and feed intake), which might have contributed to observed changing correlations across trials.Physiological and Biochemical Zoology 04/2014; 87(3):384-96. · 2.46 Impact Factor