Exercise in the Cold: High Energy Turnover in Antarctic Fish

Abstract

Antarctic fishes inhabit one of the world’s coldest marine habitats. At high latitudes the temperatures in the Southern Ocean are close to the freezing point of seawater at −1.86 °C and display little seasonal variation. The thermal conditions in the Antarctic have been relatively constant for several million years. The inhabiting fish fauna has therefore become highly specialized under the permanent cold conditions of this habitat which is reflected in a generally low upper lethal temperature of Antarctic fish at 5–6 °C [1]. In contrast to cold stenothermal polar fish, eurythermal boreal species must be able to survive a broader temperature range. While these species may be exposed to similarly cold water temperatures around 0 °C during winter, thermal conditions during summer require an elevated upper lethal temperature limit. On the other hand, eurythermal species are able to confine high cost metabolic activities like growth and reproduction to more favor able warmer seasons. Hence, acclimation to seasonal cold in eurythermal temperate species as opposed to adaptation to cold stenothermal conditions at high latitudes is associated with different requirements for the organism and may therefore result in distinct physiological features.