Thermal Tolerance of Antarctic Notothenioid Fishes Correlates with Level of Circulating Hemoglobin

AbstractThe West Antarctic Peninsula region is experiencing some of the most rapid elevations in temperature of any marine environment. We assessed thermal tolerance of white- and red-blooded Antarctic notothenioid fishes inhabiting these waters, using a modified critical thermal maximum (CTmax) design. Temperature was elevated acutely from ambient at a constant rate of 3.6°C h−1, and CTmax was defined as the temperature where animals lost righting response. CTmax temperatures of white-blooded icefishes Chionodraco rastrospinosus (C) and Chaenocephalus aceratus (C) were significantly lower than those of red-blooded fishes Gobionotothen gibberifrons (C) and Notothenia coriiceps (C). Lepidonotothen squamifrons, a red-blooded species with low hematocrit, exhibited a CTmax (C) that was significantly lower than that of the other red-blooded animals and similar to that of icefishes. A strong relationship between CTmax and hematocrit () suggests that the oxygen-carrying capacity of blood may partially dictate ac...