Mother knows best, even when stressed? Effects of maternal exposure to a stressor on offspring performance at different life stages in a wild semelparous fish
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The environment mothers are exposed to has resonating effects on offspring performance. In iteroparous species, maternal exposure to stressors generally results in offspring ill-equipped for survival. Still, opportunities for future fecundity can offset low quality offspring. Little is known, however, as to how intergenerational effects of stress manifest in semelparous species with only a single breeding episode. Such mothers would suffer a total loss of fitness if offspring cannot survive past multiple life stages. We evaluated whether chronic exposure of female sockeye salmon (Oncorhynchus nerka) to a chase stressor impaired offspring performance traits. Egg size and early offspring survival were not influenced by maternal exposure to the repeated acute stressor. Later in development, fry reared from stressed mothers swam for shorter periods of time but possessed a superior capacity to re-initiate bouts of burst swimming. In contrast to iteroparous species, the mechanisms driving the observed effects do not appear to be related to cortisol, as egg hormone concentrations did not vary between stressed and undisturbed mothers. Sockeye salmon appear to possess buffering strategies that protect offspring from deleterious effects of maternal stress that would otherwise compromise progeny during highly vulnerable stages of development. Whether stressed sockeye salmon mothers endow offspring with traits that are matched or mismatched for survival in the unpredictable environment they encountered is discussed. This study highlights the importance of examining intergenerational effects among species-specific reproductive strategies, and across offspring life history to fully determine the scope of impact of maternal stress.
KeywordsBurst swimming Egg cortisol Intergenerational effects Sockeye salmon Oncorhynchus nerka
All research conformed to protocols approved by the University of British Columbia Committee on Animal Care (#A11 0215) and met the Canadian Council for Animal Care guidelines. We thank members of UBC’s Pacific Salmon Ecology and Conservation Laboratory, Chehalis First Nation, DFO Cultus Lake Salmon Research Laboratory, DFO Environmental Watch, and undergraduate volunteers for fish collection and offspring rearing, and G. Raby, two anonymous reviewers and Marc Mangel for helpful manuscript comments. S.G.H. is funded by a Natural Sciences and Engineering Research Council (NSERC) Discovery and Strategic grant, and the Ocean Tracking Network. N.M.S. was funded by an NSERC graduate scholarship, and C.T.M. was funded by an NSERC undergraduate student research award (USRA).
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