OPEN The Journal of experimental biology | 18 May 2020
L Závorka, B Koeck, TA Armstrong, M Soğanci, A Crespel and SS Killen
While evidence suggests that warming may impact cognition of ectotherms, the underlying mechanisms remain poorly understood. A possible, but rarely considered mechanism is that metabolic response of ectotherms to warming associate with changes in brain morphology and functioning. Here we compared aerobic metabolism, volume of brain, boldness, and accuracy of maze solving of common minnows (Phoxinus phoxinus) acclimated for eight months to either their current optimal natural (14 °C) or warm (20 °C) water temperature. Metabolic rates indicated increased energy expenditure in warm acclimated fish, but also at least partial thermal compensation as warm acclimate fish maintained high aerobic scope. Warm acclimated fish had larger brain than cool acclimated fish. Volume of dorsal medulla relative to the overall brain size was larger in warm than cool acclimated fish, but proportion of other brain regions did not differ between the temperature treatments. Warm acclimated fish did not differ in boldness but did more errors than cool acclimated fish in exploring the maze across four trials. Inter-individual differences in numbers of exploration errors were repeatable across the four trials of the maze test. Our findings suggest that in warm environments, maintaining a high aerobic scope which is important for the performance of physically demanding tasks, can come at the cost of changes in brain morphology and impairment of the capacity to explore novel environments. This trade-off could have strong fitness implications for wild ectotherms.
* Data courtesy of Altmetric.com