Evolution of an Oxygen-Binding Hemoprotein in a Unique Environment: Myoglobin in the Hemoglobinless Antarctic Icefishes

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Sidell, Bruce D.
Antarctic organisms and ecosystem; Ecology and Evolutionary Biology
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For approximately the last 40 million years, a unique fish fauna has been evolving in the frigid seas surrounding Antarctica. Physiological function of these water-breathing animals has demanded many adaptations to ensure proper metabolism and regulation of biochemical processes at cell temperatures of about OoC. Among the polar fishes, one family is particularly unusual, the Channichthyid icefishes. Species in this family lack hemoglobin in their circulating blood and, at least the majority, do not possess the intracellular respiratory protein, myoglobin, that is normally responsible for enhancing movement of oxygen through aerobic muscle tissues. The PI's have recently found two species of icefish, Pseudochaenichthys georgianus and Chionodraco rastrospinosus, however, that express myoglobin, but only in one tissue - heart ventricle. The metabolism of all icefish species is highly aerobic and is based largely on the combustion of fatty fuels as energy sources. The field work will consist of a combination of trawling from R/V Polar Duke to capture icefish species and laboratory work at Palmer Station using tissues from these animals. At Palmer Station they will conduct experiments and prepare purified, fixed and or frozen material for shipment back to our CONUS laboratory for further analyses. Our overall goals are: 1) to test whether to determine myoglobin protein remains physiologically significant at the cold body temperatures of Antarctic fishes, 2) to reconstruct the evolution of the myoglobin gene within the icefish family and, 3) to identify the mechanisms controlling expression of myoglobin within icefish and related species.