Using aerobic exercise to evaluate sub-lethal tolerance of acute warming in fishes
|Author(s)||Blasco Felipe R.1, 2, Esbaugh Andrew J.3, Killen Shaun S.4, Rantin Francisco Tadeu1, Taylor Edwin W.1, 5, McKenzie David1, 6|
|Affiliation(s)||1 : Univ Fed Sao Carlos, Dept Physiol Sci, BR-13565905 Sao Carlos, SP, Brazil.
2 : Fed Univ Sao Carlos UFSCar, Sao Paulo State Univ, UNESP, Joint Grad Program Physiol Sci, Campus Araraquara, BR-14801903 Araraquara, SP, Brazil.
3 : Univ Texas Austin, Marine Sci Inst, Austin, TX 78373 USA.
4 : Univ Glasgow, Coll Med Vet & Life Sci, Inst Biodivers Anim Hlth & Comparat Med, Glasgow G12 8QQ, Lanark, Scotland.
5 : Univ Birmingham, Sch Biosci, Birmingham B15 2TT, W Midlands, England.
6 : Univ Montpellier, MARBEC, CNRS, Ifremer,IRD, F-34000 Montpellier, France.
|Source||Journal Of Experimental Biology (0022-0949) (Company Biologists Ltd), 2020-05 , Vol. 223 , N. 9 , P. jeb218602 (7p.)|
|WOS© Times Cited||16|
|Keyword(s)||CTmax, Oreochromis niloticus, Piaractus mesopotamicus|
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 (U-GT), where it first engaged the unsteady anaerobic swimming mode that preceded fatigue. After suitable recovery, each fish was exercised at 85% of their own U-GT and warmed 1 degrees 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 degrees 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.