Abstract
Temperature is one of the most important abiotic factors regulating development and biological processes in ectotherms. By 2050, climate change may result in temperature increases of 2.1-3.4°C in Manitoba, Canada. Lake sturgeon, Acipenser fulvescens, from both northern and southern populations in Manitoba were acclimated to 16, 20 and 24°C for 30days, after which critical thermal maximum (CTmax) trials were conducted to investigate their thermal plasticity. We also examined the effects of temperature on morphological and physiological indices. Acclimation temperature significantly influenced the CTmax, body mass, hepatosomatic index, metabolic rate and the mRNA expression of transcripts involved in the cellular response to heat shock and hypoxia (HSP70, HSP90a, HSP90b, HIF-1α) in the gill of lake sturgeon. Population significantly affected the above phenotypes, as well as the mRNA expression of Na+/K+ ATPase-α1 and the hepatic glutathione peroxidase enzyme activity. The southern population had an average CTmax that was 0.71 and 0.45°C higher than the northern population at 20 and 24°C, respectively. Immediately following CTmax trials, mRNA expression of HSP90a and HIF-1α was positively correlated with individual CTmax of lake sturgeon across acclimation treatments and populations (r = 0.7, r = 0.62, respectively; P < 0.0001). Lake sturgeon acclimated to 20 and 24°C had decreased hepatosomatic indices (93 and 244% reduction, respectively; P < 0.0001) and metabolic suppression (27.7 and 42.1% reduction, respectively; P < 0.05) when compared to sturgeon acclimated to 16°C, regardless of population. Glutathione peroxidase activity and mRNA expression Na+/K+ ATPase-α1 were elevated in the northern relative to the southern population. Acclimation to 24°C also induced mortality in both populations when compared to sturgeon acclimated to 16 and 20°C. Thus, increased temperatures have wide-ranging population-specific physiological consequences for lake sturgeon across biological levels of organization.
Highlights
Across Canada, mean annual and seasonal temperatures have increased between 1.7 and 2.3◦C from 1948 to 2016, with the largest increases occurring in northern Canada (Zhang et al, 2019; Vincent et al, 2015)
In order to ensure the success of these stocking programmes, and to preserve lake sturgeon throughout their natural range, it is necessary to understand the effects of different environmental temperatures on the survival and physiology of sturgeon from diverse populations
This study has demonstrated significant population-specific physiological effects following 30 days of acclimation to relevant environmental temperatures and those that may be anticipated within the lifetime of sturgeon currently being released (Manitoba Hydro, 2015)
Summary
Across Canada, mean annual and seasonal temperatures have increased between 1.7 and 2.3◦C from 1948 to 2016, with the largest increases occurring in northern Canada (Zhang et al, 2019; Vincent et al, 2015). By 2050, mean annual water temperatures within Manitoba, where several endangered populations of lake sturgeon exist, are projected to increase by 2.1–3.4◦C (Manitoba Hydro, 2015). As lake sturgeon are a long-lived species, which may require as long as 18– 28 years to mature (COSEWIC, 2006; Scott and Crossman 1998), individuals in Manitoba today may live to see the effects of increased environmental temperatures, such as those projected for 2050. Their progeny will most certainly experience elevated temperatures. We know little regarding the potential effect that increased rearing temperatures may have on thermal physiology of lake sturgeon throughout development and post-release
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