In the Classroom
How do fish in the Southern Ocean keep from freezing?


Adaptation Studies of Major Organ & Tissue Systems

Many unusual characteristics of fishes of the Antarctic have been described as "adaptations" to their chronically cold environment. However, we know little to nothing about how these characteristics evolved from the original temperate notothenioid fishes of the Sub-Antarctic. For example, one can ask whether the traits of the Antarctic fishes are truly adaptive or, perhaps, merely persistent characteristics that are shared by their temperate relatives. We are addressing this issue by comparing the regulation of blood pressure and tissue blood flow of representative Sub- and High-Antarctic notothenioid fishes. We will also evaluate the regulation of the expression of hemoglobin and myoglobin in the Sub-Antarctic species for comparison with the extensive work performed on High-Antarctic notothenioids.

One unusual family of Antarctic notothenioids, the "icefishes" (16 species in the family Channichthyidae) does not express hemoglobin at all. Furthermore, they do not produce blood cells similar to our red blood cells (erythrocytes). However, there have been intriguing reports that one member of the family, Channichthys rhinoceratus, actually produces large quantities of hemoglobinless erythrocytes. We will revisit these reports when we capture specimens of this species.