The giant Antarctic toothfish Dissostichus mawsoni is a large perciform fish belonging to the suborder Notothenioidei endemic to the inshore waters of the Southern Ocean encircling Antarctica (Eastman, 1993). It is very large fish often reaching 1 m in length and weighing between 34 and 55 kg (Dewitt et al., 1990), and living up to 50 years (Horn et al., 2003). The mean water temperature in the Southern Ocean year-round is -1.86°C, which is at or near the freezing point of seawater (Hunt et al., 2003). The toothfish is a well- studied animal displaying a number of biochemical and physiological adaptations to the cold (Williams et al., 1985; Eastman, 1993; Chen et al., 1997; Metcalf et al., 1999; Pointer et al., 2005). As a large fish, it has a large prominent eye (Fig. 5.1). Interestingly, no reports of lens cataracts have been noted in the literature during the approximately 40 years of study. Because of unique habitat of the toothfish, it is worth placing this animal in context of existing model systems, both from the perspective of its environment and its rele- vant general biology if we are to properly exploit the toothfish as a new model system for lens biology. THE ANTARCTIC ENVIRONMENT The Antarctic continent covers approximately 14 mil- lion km 2 and is the Southern-most of the earth’s land masses. It is oceanographically isolated from all other continental land masses by large amounts of open water. This isolation has allowed for the development of the Antarctic circumpolar current (ACC). The ACC has the largest volume of any oceanic current and extends from the ocean surface to the sea-floor (2000 ~ 4000 m). The ACC varies from 200 km to 1000 km wide (slightly deflected and compressed by the tip of South America) thereby representing a true physical barrier separating the fishes of the Southern Ocean from those of the rest of the world (Eastman, 1993). The temperature on the Antarctic continent itself is at or below 0°C, with the world’s lowest recorded temperature of -89.6°C reported at Vostok Station (USSR). In addition to being extremely cold year-round there is very little yearly precipitation, 40~100 cm per year on the coast with trace amounts at the South Pole The Antarctic Toothfish: A New Model System for Eye Lens Biology Andor J.Kiss Laboratory for Ecophysiological Cryobiology, Department of Zoology, Miami University, Oxford, OH 45056, USA The Antarctic Environment 48 Toothfish Biology 49 Lens Biochemistry 50 Lens Crystallin cDNA Sequences 52 Other Aspects of Toothfish Eye Biology 53 Strengths of the Toothfish as a Model System 53 References 54 OUTLINE 5 CHAPTER Animal Models in Eye Research © 2008, Elsevier Ltd. 48