69.6 Saturday, Jan. 5 Relationships between hemoprotein expression and cardiovascular physiology of Antarctic notothenioids: form, function, and future implications. BEERS, J.M.; Stanford University firstname.lastname@example.org
Antarctic notothenioid fishes have been exploited by scientists for decades as classic Krogh-style models with which to study cold-adapted physiological traits. Some of the most fascinating discoveries have come from studies focused on one particular group of notothenioids, the white-blooded icefishes (Family: Channichthyidae). Noted for their complete lack of hemoglobin, and also myoglobin in some species, these animals have partially compensated for the loss of oxygen-binding proteins by utilizing several enhanced cardiovascular features. One such characteristic is the presence of vast blood vessel networks, evidenced most strikingly in the eyes. Findings have shown that retinal vascular densities are inversely correlated to the amount of hemoglobin in the blood, thus suggesting a relationship between heme protein expression and oxygen supply/demand in the highly aerobic retina. Interestingly, data indicate that the development of the elaborate vascular patterns that we see in the eyes of present day icefishes may have arisen via a cellular route of nitric oxide-mediated angiogenesis. Implications for this finding hold importance because this cell signaling pathway is fundamental to most, if not all, vertebrate animals, and thereby allows us to explore questions that may have potential biomedical applications. Furthermore, the unique cardiovascular physiology of icefishes may prove costly because the adaptations for life in the stably cold, well-oxygenated waters of the Southern Ocean might reduce the tolerance of these fish to high temperature. Indeed, icefish have significantly lower thermal tolerance than their red-blooded counterparts, which could place these animals in a precarious position with regard to future climatic warming.