Using aerobic exercise to evaluate sub-lethal tolerance of acute warming in fishes

Blasco, F.R., Esbaugh, A.J., Killen, S. , Rantin, F.T., Taylor, E.W. and McKenzie, D.J. (2020) Using aerobic exercise to evaluate sub-lethal tolerance of acute warming in fishes. Journal of Experimental Biology, 223, jeb218602. (doi: 10.1242/jeb.218602) (PMID:32381588) (PMCID:PMC7225124)

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Abstract

We investigated whether fatigue from sustained aerobic swimming provides a sub-lethal endpoint to define tolerance of acute warming in fishes, as an alternative to loss of equilibrium (LOE) during a critical thermal maximum (CTmax) protocol. Two species were studied, Nile tilapia (Oreochromis niloticus) and pacu (Piaractus mesopotamicus). Each fish underwent an incremental swim test to determine gait transition speed (UGT), where it first engaged the unsteady anaerobic swimming mode that preceded fatigue. After suitable recovery, each fish was exercised at 85% of their own UGT and warmed 1°C every 30 min, to identify the temperature at which they fatigued, denoted as CTswim. Fish were also submitted to a standard CTmax, warming at the same rate as CTswim, under static conditions until LOE. All individuals fatigued in CTswim, at a mean temperature approximately 2°C lower than their CTmax. Therefore, if exposed to acute warming in the wild, the ability to perform aerobic metabolic work would be constrained at temperatures significantly below those that directly threatened survival. The collapse in performance at CTswim was preceded by a gait transition qualitatively indistinguishable from that during the incremental swim test. This suggests that fatigue in CTswim was linked to an inability to meet the tissue oxygen demands of exercise plus warming. This is consistent with the oxygen and capacity limited thermal tolerance (OCLTT) hypothesis, regarding the mechanism underlying tolerance of warming in fishes. Overall, fatigue at CTswim provides an ecologically relevant sub-lethal threshold that is more sensitive to extreme events than LOE at CTmax.

Item Type:Articles
Status:Published
Refereed:Yes
Glasgow Author(s) Enlighten ID:Killen, Professor Shaun
Authors: Blasco, F.R., Esbaugh, A.J., Killen, S., Rantin, F.T., Taylor, E.W., and McKenzie, D.J.
College/School:College of Medical Veterinary and Life Sciences > Institute of Biodiversity Animal Health and Comparative Medicine
Journal Name:Journal of Experimental Biology
Publisher:Company of Biologists
ISSN:0022-0949
ISSN (Online):1477-9145
Copyright Holders:Copyright © 2020 Published by The Company of Biologists Ltd
First Published:First published in Journal of Experimental Biology 223: jeb218602
Publisher Policy:Reproduced under a Creative Commons License

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Project CodeAward NoProject NamePrincipal InvestigatorFunder's NameFunder RefLead Dept
167015The Influence of Individual Physiology on Group Behaviour in Fish SchoolsShaun KillenNatural Environment Research Council (NERC)NE/J019100/1Institute of Biodiversity, Animal Health and Comparative Medicine