Evidence of Circadian Rhythm, Oxygen Regulation Capacity, Metabolic Repeatability and Positive Correlations between Forced and Spontaneous Maximal Metabolic Rates in Lake Sturgeon Acipenser fulvescens

Abstract

Animal metabolic rate is variable and may be affected by endogenous and exogenous factors, but such relationships remain poorly understood in many primitive fishes, including members of the family Acipenseridae (sturgeons). Using juvenile lake sturgeon (Acipenser fulvescens), the objective of this study was to test four hypotheses: 1) A. fulvescens exhibits a circadian rhythm influencing metabolic rate and behaviour; 2) A. fulvescens has the capacity to regulate metabolic rate when exposed to environmental hypoxia; 3) measurements of forced maximum metabolic rate (MMRF) are repeatable in individual fish; and 4) MMRF correlates positively with spontaneous maximum metabolic rate (MMRS). Metabolic rates were measured using intermittent flow respirometry, and a standard chase protocol was employed to elicit MMRF. Trials lasting 24 h were used to measure standard metabolic rate (SMR) and MMRS. Repeatability and correlations between MMRF and MMRS were analyzed using residual body mass corrected values. Results revealed that A. fulvescens exhibit a circadian rhythm in metabolic rate, with metabolism peaking at dawn. SMR was unaffected by hypoxia (30% air saturation (O2sat)), demonstrating oxygen regulation. In contrast, MMRF was affected by hypoxia and decreased across the range from 100% O2sat to 70% O2sat. MMRF was repeatable in individual fish, and MMRF correlated positively with MMRS, but the relationships between MMRF and MMRS were only revealed in fish exposed to hypoxia or 24 h constant light (i.e. environmental stressor). Our study provides evidence that the physiology of A. fulvescens is influenced by a circadian rhythm and suggests that A. fulvescens is an oxygen regulator, like most teleost fish. Finally, metabolic repeatability and positive correlations between MMRF and MMRS support the conjecture that MMRF represents a measure of organism performance that could be a target of natural selection.

Measuring maximum and standard metabolic rates using intermittent‐flow respirometry: a student laboratory investigation of aerobic metabolic scope and environmental hypoxia in aquatic breathers

“…The procedures on fish described below were approved by University of Copenhagen, Denmark, and University of Manitoba, Canada (Svendsen et al , , ). Oncorhynchus mykiss was used for experimentation because the species is readily available from commercial hatcheries.…”

Phenotypic differences between the sexes in the sexually plastic mangrove rivulus fish (Kryptolebias marmoratus)

“…Following background reading, the first focal individual, still in its home container, was chased with the blunt end of a fish net handle for 5 min, similar to previous studies (Svendsen et al, 2012(Svendsen et al, , 2014. Immediately afterwards, the focal individual was transferred into the respirometry chamber and the AutoResp software was set to run a single 5 s flush, 120 s wait and 180 s measurement cycle.…”

“…Using the interpolation, the estimated microbial respiration was subtracted from each measure of metabolic rate (Norin and Malte, 2011). SMR was estimated using metabolic rate data collected over 16 h. Similar to previous studies (Svendsen et al, 2014;Rosewarne et al, 2016), the median of the lowest 10 measurements of metabolic rate with an R 2 value ≥0.92 (calculated by AutoResp software) was used as an estimate of SMR for each individual fish. Aerobic scope (AS), the difference between MMR and SMR (Sandblom et al, 2014), also was calculated for individuals with both MMR and SMR measurements.…”

Risk in a changing world: environmental cues drive anti-predator behaviour in lake sturgeon (Acipenser fulvescens) in the absence of predators

“…This is especially true of young sturgeon, that forage actively during the night and reduce activity during the day to avoid visual predators (Richmond & Kynard, 1995). Furthermore, Lake Sturgeon metabolic rate has been linked to decreases in light levels (Svendsen et al, 2014). Turbidity may therefore provide cover from visuallyguided predators, allowing sturgeon to increase foraging activity in darker turbid environments relative to brighter clear-water environments.…”