The effects of population and thermal acclimation on the growth, condition and cold responsive mRNA expression of age‐0 lake sturgeon (Acipenser fulvescens)

Abstract

In Manitoba, Canada, wild lake sturgeon (Acipenser fulvescens) populations exist along a latitudinal gradient and are reared in hatcheries to bolster threatened populations.We reared two populations of lake sturgeon, one from each of the northern and southern ends of Manitoba and examined the effects of typical hatchery temperatures (16 C) as well as 60-day acclimation to elevated rearing temperatures (20 C) on mortality, growth and condition throughout early development. Additionally, we examined the cold shock response, which may be induced during stocking, through the hepatic mRNA expression of genes involved in the response to cold stress and homeoviscous adaptation (HSP70, HSP90a, HSP90b, CIRP and SCD). Sturgeon were sampled after 1 day and 1 week following stocking into temperatures of 8, 6 and 4 C in a controlled laboratory environment. The southern population showed lower condition and higher mortality during early life than the northern population while increased rearing temperature impacted the growth and condition of developing northern sturgeon. During the cold shock, HSP70 and HSP90a mRNA expression increased in all sturgeon treatments as stocking temperature decreased, with higher expression observed in the southern population. Expression of HSP90b, CIRP and SCD increased as stocking temperature decreased in northern sturgeon with early acclimation to 20 C. Correlation analyses indicated the strongest molecular relationships were in the expression of HSP90b, CIRP and SCD, across all treatments, with a correlation between HSP90b and body condition in northern sturgeon with early acclimation to 20 C. Together, these observations highlight the importance of population and rearing environment throughout early development and on later cellular responses induced by cold stocking temperatures.

Elevated temperatures reduce population-specific transcriptional plasticity in developing lake sturgeon (Acipenser fulvescens)

“…In early developmental stages, different phenotypes and developmental trajectories can emerge from genetically distinct populations exposed to similar environmental change, based, in part, on differences in transcriptome plasticity. Induced molecular responses to stressors often differ between populations, likely as a result of differences in transcriptional plasticity, and may be indicative of long-term fitness and survival consequences if phenotypes cannot be adequately altered in early life to allow individuals to persist in changing environments (Whitehead et al, 2012; Bugg et al, 2020; Mundy et al, 2020; Bugg et al, 2021).…”

“…Since the 1950’s however, habitat loss and degradation associated with dams and other barriers have become the most prominent threats to populations and the species’ persistence (Cleator et al, 2010; COSEWIC 2017; Van der Lee and Koops, 2021). Temperatures in the northern range for lake sturgeon are also increasing faster than the global average (projected 2.1-3.4°C increase by 2050; Manitoba Hydro, 2015), which may further limit suitable habitat, and imperil these endangered subarctic populations as water temperatures exceed their thermal limits (Vincent et al, 2015; Zhang et al, 2019; Bugg et al, 2021).…”

“…Increasing environmental temperatures directly influence the development, metabolism, transcriptomic responses, and survival of northern populations of lake sturgeon under laboratory conditions and may contribute to observed declines in wild stocks (Bugg et al, 2020; Bugg et al, 2021). Indirectly, elevating temperatures may increase environmental hypoxia and the susceptibility of lake sturgeon to environmentally prevalent bacterial or viral pathogens, which may be transmitted horizontally between individuals or vertically across generations (LaPatra et al, 1994; Georgiadis et al, 2001; Fujimoto, 2018; Clouthier et al, 2020).…”

“…Sturgeons may be especially susceptible to the combined effects of increasing temperature, hypoxic environments, and pathogens in early development, when mortality is often high (> 90%; Caroffino et al, 2010) and sturgeon have limited immune responses and ability to escape stressful environments (Webb, 1986; Peake et al, 1997; Schindler, 2001; Breau et al, 2011; Deslauriers and Kieffer, 2012; Gradil et al, 2014 a,b; Verhille et al, 2014). However, despite these vulnerabilities in early development, sturgeon have successfully persisted for hundreds of millions of years in ever-changing environments, evolving elaborate polyploid genetic complexity, and demonstrating high levels of phenotypic plasticity in early development, with the potential for increased underlying inducible transcriptional plasticity (Braasch and Postlethwait, 2012; Trifonov et al, 2016; Bugg et al, 2020; Bugg et al, 2021; Penman, 2021; Yoon et al, 2021; Brandt et al, 2021, Brandt et al, 2022). Therefore, early development represents a crucial window to examine lake sturgeon responses to thermal acclimation, when exceptionally plastic responses may be anticipated (Burggren, 2018; Barley et al, 2021).…”

“…Here we used RNAseq to investigate transcriptomic responses to increased environmental temperatures in the gills of two latitudinally separated and genetically distinct populations of developing lake sturgeon (McDougall et al, 2017; Bugg et al, 2020). As sturgeons are ancestral polyploid species, with highly variable genomic architecture and phenotypic plasticity (Braasch and Postlethwait, 2012; Trifonov et al, 2016; Bugg et al, 2021), we expected these populations of lake sturgeon to respond uniquely to the temperature treatments. We examined the gill mRNA transcript abundance in n = 36 individuals from three thermal acclimation treatments in the northern and southern population of lake sturgeon within Manitoba.…”