Date of Award

Fall 2021

Publication Type

Thesis

Degree Name

M.Sc.

Department

Biological Sciences

Keywords

Egg cortisol, Maternal stress, Chinook salmon, Sex-specific effects

Supervisor

O. Love

Supervisor

D. Higgs

Rights

info:eu-repo/semantics/openAccess

Abstract

Assessing the intergenerational effects of maternal stress is important for predicting how offspring will respond to changing environments. The overall aim of my thesis was to quantify the effects of maternal state on maternally derived egg cortisol and determine whether this variation in egg cortisol impacts Chinook salmon offspring performance and fitness in a sex-specific way. I quantified within-female changes in maternal energetics and reproductive metrics that I linked to egg quality and ultimately embryo survival. I found egg cortisol increases with increasing maternal plasma cortisol, and increases further as plasma cortisol levels rise with each day that eggs are retained after ovulation. Following an experimental exposure of eggs to varying biologically relevant cortisol doses, subsequent offspring were exposed to a post-natal environmental stressor (low water depths) or control conditions (normal water depths). Both males and females in the low water environment consistently exhibited lighter body masses, but fish exposed to higher levels of egg cortisol developing in low water conditions exhibited the smallest body size regardless of sex. Offspring energetic demand and stress responsiveness in relation to treatments were only affected in females. Males showed a longer-term effect of both the cortisol and environmental treatments on compensatory growth in salt water compared to females. Interestingly, treatments and their interactions did not significantly affect survival in either sex. Results from my thesis indicate that increases in maternal cortisol lead to increases in egg cortisol that can impact embryo survival and have sex-specific effects on offspring phenotype and performance. As environments continue to change rapidly and become more unpredictable, it is timely to further determine the importance of maternal stress effects in coping with environmental change.

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