Biology subjects

Asheim, E. R.

Publications and source records attributed to Asheim, E. R..

6 recordsLinked to original sources

bioRxiv2022

Temperature and dietary energy content influence female maturation age and egg nutritional content in Atlantic salmon

The environment experienced by a female influences reproductive traits in many species of fish. Environmental factors such as temperature and diet are not only important mediators of female maturation and reproduction but also of egg traits and offspring fitness through maternal provisioning. In this study, we use three-year-old, tank-reared, Atlantic salmon from two Finnish populations to investigate the effect of temperature and diet on maturation and egg traits. We show that a temperature difference of 2{degrees}C is sufficient to delay maturation in female Atlantic salmon whereas a 22% reduction in dietary energy content had no effect on maturation. Diet did not influence the body size, condition, or fecundity of the mature females or the size or protein content of the eggs. However, a higher energy diet increased egg lipid content. Neither female body size nor condition were associated with egg size or fat/protein composition. Our results indicate that female salmon that have a poorer diet in terms of energy content may have a reproductive disadvantage due to lower energy provisioning of eggs. This disadvantage has the potential to translate into fitness consequences for their offspring.

ecology↗

bioRxiv2022

Water salinity does not affect acute thermal tolerance (CTmax) in zebrafish (Danio rerio)

Tolerance against acute warming is an essential trait that can determine how organisms cope during heatwaves, yet the mechanisms underlying it remain elusive. Water salinity has previously been shown to modulate thermal tolerance and may therefore provide clues towards these limiting mechanisms. Here we tested whether short (2 hours) and long (10 days) term exposure to different water salinities (0-5 ppt) affected acute thermal tolerance in zebrafish (N=269). We found that water salinity did not affect the thermal tolerance of zebrafish at either time point, indicating that salinity does not affect the mechanism limiting acute thermal tolerance limits in zebrafish. We did, however, observe unexpected behaviour during the CTmax test in a subset of fish in the highest salinity treatment after 10 days (3 ppt), indicating some form of salinity-driven disturbance during warming.

physiology↗

bioRxiv2022

Adipose tissue mitochondrial respiration in Atlantic salmon: implications for sex-dependent life-history variation

Adipose tissue is essential for energy homeostasis, with mitochondria having a central role in its function. Mitochondria-mediated white adipose tissue dysfunction has been linked to several metabolic disorders in humans but surprisingly little is known about natural variation in mitochondrial function in wild animal populations, and its evolutionary significance. Early sexual maturation (low age-at-maturity) in Atlantic salmon (Salmo salar) is promoted by higher adiposity and has a strong genetic association with the vgll3 locus. This makes Atlantic salmon a convenient wild model to study the potential role of mitochondria-mediated adipose tissue processes in relation to the timing of maturation. Yet, mitochondrial respiration has not been measured in the adipose tissue in fish, and the lack of data is restricting the development of informed hypotheses. Here, using 13 Atlantic salmon individuals reared in common-garden conditions, we first verified the feasibility of measuring mitochondrial respiration in the adipose tissue. As expected, the respiration level was generally low, but nonetheless we successfully quantified its biological variation in the adipose tissue. Next, we analysed the potential association of mitochondrial respiration with mitochondrial DNA (mtDNA) content, adipocyte size, sex, and the vgll3 genotype. Despite low samples sizes, mitochondrial respiration, leak respiration, and coupling capacity (P/E ratio) were marginally significantly decreased in immature females carrying with the vgll3 early maturation compared to the alternative genotype. Based on these results, we suggested two new hypotheses on how the coupling capacity of oxidative phosphorylation could be linked with the timing of maturation via adiposity and pave the way to study the mechanistic relationships between life-history variation and mitochondrial bioenergetics in wild populations.

physiology↗

bioRxiv2022

Strong effects of temperature, population and age-at-maturity genotype on maturation probability for Atlantic salmon in a common garden setting

O_LIAge at maturity is a key life history trait and involves a trade-off between survival risk and reproductive investment, has close connections to fitness, and is an important factor for population structures. Temperature can have a dramatic influence on life history in ectotherms, but this influence may differ between populations. While an increasing number of studies have examined population-dependent reactions with temperature, few have investigated this in the context of maturation timing. C_LIO_LIAtlantic salmon is a highly relevant study species for improving understanding of this topic as it displays considerable variation in life-history strategies, including maturation timing. Additionally, a large amount of this variation in maturation timing has been associated with a genomic region including the strong candidate gene vgll3, but the effect of this gene in the context of different environments and populations has not been studied. C_LIO_LIUsing a large-scale common-garden experiment, we find strong effects of temperature, population, and vgll3 genotype on maturation in 2-year-old male Atlantic salmon. Observed maturation probability was 4.8 times higher in individuals reared at a mean temperature of 8.6{degrees}C compared to 6.9{degrees}C. This temperature effect was population-specific and was higher in the southern population compared to the northern population, potentially due to a higher intrinsic growth in the southern population as well as growth-temperature interaction. C_LIO_LIThe early-maturation vgll3*E associated with a significantly higher maturation probability, but there was no vgll3-interaction with temperature or population. C_LIO_LIBoth body condition and body mass associated strongly with maturation; the body-condition association was stronger in fish carrying the vgll3*E allele, and the body mass association was only present in the warm treatment. C_LIO_LIOur findings demonstrate that the relative effect of vgll3 on maturation timing is similar for two populations and two thermal environments and gives new perspectives on the relative effect of vgll3 compared to such influences. Additionally, we show that populations can vary in their response to temperature change in terms of maturation timing, and that high intrinsic growth could potentially be associated with higher thermal sensitivity for life history variation. C_LI

evolutionary biology↗

bioRxiv2021

Standard metabolic rate does not associate with age-at-maturity genotype in juvenile Atlantic salmon

Atlantic salmon (Salmo salar) is a species with diverse life-history strategies, to which the timing of maturation contributes considerably. Recently, the genome region including the gene vgll3 has gained attention as a locus with a large effect on salmon maturation timing, and recent studies on the vgll3 locus in salmon have indicated that its effect might be mediated through body condition and accumulation of adipose tissue. However, the cellular and physiological pathways leading from vgll3 genotype to phenotype are still unknown. Standard metabolic rate is a potentially important trait for resource acquisition and assimilation and we hypothesized that this trait, being a proxy for the maintenance energy expenditure of an individual, could be an important link in the pathway from vgll3 genotype to maturation-timing phenotype. As a first step to studying links between vgll3 and the metabolic phenotype of Atlantic salmon, we measured the standard metabolic rate of 150 first year Atlantic salmon juveniles of both sexes, originating from 14 different families with either late maturing or early maturing vgll3 genotypes. No significant difference in mass-adjusted standard metabolic rate was detected between individuals with different vgll3 genotypes, indicating that juvenile salmon of different vgll3 genotypes have similar maintenance energy requirements in the experimental conditions used and that the effects of vgll3 on body condition and maturation are not strongly related to maintenance energy expenditure in either sex at this life stage. Summary statementWe show that vgll3, a gene known to have significant effects on Atlantic salmon (Salmo salar) life-history strategy, does not associate with standard metabolic rate in salmon juveniles.

genetics↗

bioRxiv2021

Genetic coupling of life-history and aerobic performance in juvenile Atlantic salmon

A better understanding of the genetic and phenotypic architecture underlying life-history variation is a longstanding aim in biology. Theories suggest energy metabolism determines life-history variation by modulating resource acquisition and allocation trade-offs, but the genetic underpinnings of the relationship and its dependence on ecological conditions have rarely been demonstrated. The strong genetic determination of age-at-maturity by two unlinked genomic regions (vgll3 and six6) makes Atlantic salmon (Salmo salar) an ideal model to address these questions. Using more than 250 juveniles in common garden conditions, we quantified the covariation between metabolic phenotypes -standard and maximum metabolic rates (SMR and MMR), and aerobic scope (AS) - and the life-history genomic regions and tested if food availability modulates the relationships. We found that the early maturation genotype in vgll3 was associated with higher MMR and consequently AS. Additionally, MMR exhibited physiological epistasis; it was decreased when late maturation genotypes co-occurred in both genomic regions. Contrary to our expectation, the life-history genotypes had no effects on SMR. Further, food availability had no effect on the genetic covariation, suggesting a lack of genotype-by-environment interactions. Our results provide insights on the key organismal processes that link energy use at the juvenile-stage to age-at-maturity, indicating potential mechanisms by which metabolism and life-history can coevolve.

evolutionary biology↗