Data For: Diet changes thermal acclimation capacity, but not acclimation rate in a marine ectotherm (Girella nigricans) during warming

Global climate change is increasing thermal variability in coastal marine
environments and the frequency, intensity, and duration of marine
heatwaves. At the same time, food availability and quality are being
altered by anthropogenic environmental changes. Marine ectotherms often
cope with changes in temperature through physiological acclimation, which
can take several weeks and is a nutritionally demanding process.
Here, we tested the hypothesis that different
ecologically relevant diets (omnivorous, herbivorous,
carnivorous) impact thermal acclimation rate and capacity, using a
temperate omnivorous fish as a model (opaleye; Girella
nigricans). We measured acute thermal performance curves for
maximum heart rate because cardiac function has been observed to set upper
thermal limits in ectotherms. Opaleye acclimated rapidly after
raising water temperatures, but their thermal limits and acclimation rate
were not affected by their diet. However, the fish’s acclimation capacity
for maximum heart rate was sensitive to diet, with fish in the herbivorous
treatment displaying the smallest change in heart rate throughout
acclimation. Mechanistically, ventricle fatty acid composition differed
with diet treatment and was related to cardiac performance in ways
consistent with homoviscous adaptation. Our results suggest that
diet is an important, but often overlooked, determinant of thermal
performance in ectotherms on environmentally relevant timescales.