title: Consequences of experimental cortisol manipulations on the thermal biology of the checkered puffer (Sphoeroides testudineus) in laboratory and field environments.
abstract: Anthropogenic climate change is altering temperature regimes for coastal marine fishes. However, given that temperature changes will not occur in isolation of other stressors, it is necessary to explore the potential consequences of stress on the thermal tolerances and preferences of tropical marine fish in order to understand the thresholds for survival, and predict the associated coastal ecological consequences. In this study, we used exogenous cortisol injections to investigate the effects of a thermal challenge on checkered puffers (Sphoeroides testudineus) as a secondary stressor. There were no significant differences between control and cortisol-treated fish 48h following cortisol treatment for swimming ability (using a chase to exhaustion protocol), blood glucose concentrations or standard metabolic rate. In the lab, control and cortisol-treated puffers were exposed to ambient (29.1±1.5°C), ambient +5°C (heat shock) and ambient -5°C (cold shock) for 4h and to evaluate the consequences of abrupt temperature change on puff performance and blood physiology. Following cold shock, control fish exhibited increases in cortisol levels and weak 'puff' performance. Conversely, fish dosed with cortisol exhibited consistently high cortisol levels independent of thermal treatment, although there was a trend for an attenuated cortisol response in the cortisol-treated fish to the cold shock treatment. A 20-day complementary field study conducted in the puffer's natural habitat, a tidal creek in Eleuthera, The Bahamas, revealed that cortisol-injected fish selected significantly cooler temperatures, measured using accumulated thermal units, when compared to controls. These results, and particularly the discrepancies between consequences documented in the laboratory and the ecological trends observed in the field, highlight the need to establish the link between laboratory and field data to successfully develop management policies and conservation initiatives with regards to anthropogenic climate change.
authors.affiliation: Fish Ecology and Conservation Physiology Laboratory, Department of Biology, Carleton University, 1125 Colonel By Drive, Ottawa, Ontario, Canada K1S 5B6. Electronic address: felicia.stlouis@gmail.com.
authors.forename: F
authors.initials: F
authors.lastname: Cull
authors.affiliation: Department of Natural Resources and Environmental Sciences, University of Illinois, Champaign, IL 61801, USA. Electronic address: suski@illinois.edu.
authors.forename: C D
authors.initials: CD
authors.lastname: Suski
authors.affiliation: Department of Natural Resources and Environmental Sciences, University of Illinois, Champaign, IL 61801, USA; Cape Eleuthera Institute, Eleuthera, Bahamas. Electronic address: aaronshultz@ceibahamas.org.
authors.forename: A
authors.initials: A
authors.lastname: Shultz
authors.affiliation: Department of Environmental Conservation, University of Massachusetts Amherst, 160 Holdsworth Way, Amherst, MA 01003, USA. Electronic address: danylchuk@eco.umass.edu.
authors.forename: A J
authors.initials: AJ
authors.lastname: Danylchuk
authors.affiliation: Department of Psychology, Neuroscience, and Behaviour, McMaster University, 1280 Main Street West, Hamilton, Ontario, Canada L8S 4L8. Electronic address: coconn@mcmaster.ca.
authors.forename: C M
authors.initials: CM
authors.lastname: O'Connor
authors.affiliation: Department of Biology, The College of The Bahamas, Box F-2766, Freeport, Grand Bahama, Bahamas. Electronic address: kmurchie@cob.edu.bs.
authors.forename: K J
authors.initials: KJ
authors.lastname: Murchie
authors.affiliation: Fish Ecology and Conservation Physiology Laboratory, Department of Biology, Carleton University, 1125 Colonel By Drive, Ottawa, Ontario, Canada K1S 5B6; Institute of Environmental Science, Carleton University, 1125 Colonel By Drive, Ottawa, Ontario, Canada K1S 5B6. Electronic address: steven_cooke@carleton.ca.
authors.forename: S J
authors.initials: SJ
authors.lastname: Cooke
mesh_terms: D000818:Animals; D001444:Bahamas; D001786:Blood Glucose; D058639:Cold-Shock Response / Q000187:drug effects*; D018869:Heat-Shock Response / Q000187:drug effects*; D006854:Hydrocortisone / Q000494:pharmacology*; D013550:Swimming; D013696:Temperature; D023721:Tetraodontiformes / Q000378:metabolism / Q000502:physiology*
chemical_list: D001786:Blood Glucose; D006854:Hydrocortisone
keywords: Coastal environment; Cold shock; Heat shock; Stress physiology; Temperature