title: Supraphysiological cortisol elevation alters the response of wild bluegill sunfish to subsequent stressors.
abstract: Wild fish are frequently exposed to multiple stressors, but the influence of previous or ongoing stress on an animal's subsequent response is poorly understood. Using wild-caught bluegill sunfish (Lepomis macrochirus) as a model, we used exogenous hormone implants to experimentally raise circulating cortisol in a group of fish for ∼10 days. We also maintained sham-treated and control groups of fish. We subjected all animals to a secondary stressor in the form of either a heat challenge or fasting challenge. We compared survival, body condition, and plasma-borne indicators of physiological status among cortisol-treated, sham-treated, and control groups following the secondary stressor. In order to compare short- and long-term effects of cortisol treatment, we initiated the secondary stressor either 4 or 30 days following initial cortisol treatment. Cortisol-treated fish succumbed to the fasting challenge sooner than sham-treated and control fish at both 4 and 30 days. Interestingly, cortisol-treated fish lost equilibrium sooner than sham-treated and control fish during the heat challenge when conducted at 30 days, but not at 4 days. These results demonstrate that multiple simultaneous stressors have cumulative effects on bluegill sunfish. Furthermore, these results demonstrate that supraphysiological cortisol doses alter the long-term responses of bluegill sunfish to additional challenges, even after apparent recovery. Such cumulative and long-term effects may be an important factor in mediating the response of wild animals to natural and anthropogenic stressors, and should be considered in ecological studies.
authors.affiliation: Fish Ecology and Conservation Physiology Laboratory, Department of Biology, Carleton University, Ottawa, Ontario, Canada.
authors.forename: Sarah H
authors.initials: SH
authors.lastname: McConnachie
authors.forename: Constance M
authors.initials: CM
authors.lastname: O'Connor
authors.forename: Kathleen M
authors.initials: KM
authors.lastname: Gilmour
authors.forename: George K
authors.initials: GK
authors.lastname: Iwama
authors.forename: Steven J
authors.initials: SJ
authors.lastname: Cooke
mesh_terms: D000818:Animals; D006854:Hydrocortisone / Q000097:blood / Q000502:physiology*; D010473:Perciformes / Q000097:blood / Q000502:physiology*; D013312:Stress, Physiological; D013997:Time Factors
chemical_list: D006854:Hydrocortisone