The effect of maternal stress on early life history traits and performance in salmonids
Date
2023-11-23
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Abstract
During the upstream spawning migration of Pacific salmon, circulating cortisol concentration increases to mobilize energy stores. Pacific salmon contend with a gauntlet of stressors that can further elevate cortisol concentrations in response to stressful stimuli. Consequently, plasma cortisol concentrations measured in maternal fish that have reached their spawning grounds may reflect their recent stress history. Despite studies mimicking the maternal transfer of cortisol to the eggs, how natural variation in maternal cortisol concentrations shapes offspring phenotypes is unclear. Therefore, I assessed whether stress in maternal salmonids alters the growth and stress performance of their offspring via increased cortisol deposition in the eggs. Specifically, I tested whether high concentrations of circulating cortisol in maternal fish reduced embryo survival, and fry growth and stress performance. Eggs from 101 wild coho salmon (Oncorhynchus kisutch) females were collected from three rivers in the interior Fraser River watershed, British Columbia, Canada. The eggs were fertilized and reared until the fry stage at a hatchery. High egg cortisol concentration increased offspring mortality at the eyed stage. Interestingly, the surviving free-swimming fry had enhanced growth, resulting in larger size, and heightened cortisol stress response. The corresponding increase in the transcript abundance of genes related to growth and stress axis functioning in the fry suggest that high maternal cortisol concentrations programmed offspring for faster growth and heightened stress reactivity during early development. To test whether high egg cortisol concentrations specifically causes the phenotypic variation such as that observed in coho salmon, I manipulated steroid concentrations in the eggs of 10 maternal rainbow trout (Oncorhynchus mykiss) by immersion in water-borne cortisol during fertilization. Cortisol treatments increased egg steroid concentrations; however, neither the developmental trajectory nor the stress performance of fry differed statistically among treatments. Therefore, the utility of egg cortisol concentration as a biomarker of offspring developmental performance may be dependent on the life history of the animal. Overall, maternal cortisol concentration seems to act as a cue that prepares the offspring of wild coho salmon for stressful environments.
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Keywords
maternal stress, cortisol, Pacific salmon
Citation
Lazaro-Côté, A. (2023). The effect of maternal stress on early life history traits and performance in salmonids (Doctoral thesis, University of Calgary, Calgary, Canada). Retrieved from https://prism.ucalgary.ca.