Optimum temperature in juvenile salmonids: Connecting subcellular indicators to tissue function and whole-organism thermal optimum

: Anttila K, Casselman M, Schulte P, Farrell A

: 2013

: Physiological and Biochemical Zoology

: 2

: 86

: 2

: 245

: 256

: 12

: 1522-2152

DOI: https://doi.org/10.1086/669265(external)

: http://api.elsevier.com/content/abstract/scopus_id:84874399253(external)

Temperature affects processes at all levels of biological organization, but it is unclear whether processes at different levels have similar thermal optima (T). Here, we compare the T for aerobic scope, a whole-organism measure of performance, with both the Arrhenius breakpoint temperature for maximum heart rate (HR-ABT), a measure of tissue level performance, and the temperature at which AMP-activated protein kinase (AMPK) is phosphorylated in the heart, an indicator of an increase in dependence on anaerobic energy metabolism at the cellular level in juvenile rainbow trout Oncorhynchus mykiss. The T for aerobic scope was 19°C, with aerobic scope being maintained at ≥90% of maximum (termed a "T window") from 16.5° to 20.5°C. HR-ABT occurred at, 17.6°±0.3°C while the profile of AMPK phosphorylation started to change from baseline at 19°C, suggesting that these processes have similar thermal sensitivities as a fish is warmed to T. The effects of temperature on AMPK phosphorylation were also measured in coho salmon Oncorhynchus kisutch hearts and compared with previously published values for HR-ABT and aerobic scope T. AMPK phosphorylation in coho hearts began to change at temperatures above 17°C, which again is comparable with the published T for aerobic scope (17°C) and HR-ABT (16.5°±0.2°C) in these individuals. Thus, the thermal sensitivity of these subcellular, tissue, and whole-organismfunctions are highly correlated in both rainbow trout and coho salmon and may depend on each other. © 2013 by The University of Chicago. All rights reserved.