3.2 Wednesday, Jan. 4 Ecological physiology of the Antarctic Trematomus fishes: effect of temperature and ice on freeze avoidance FIELDS, L.G.*; DEVRIES, A.L.; University of Illinois at Urbana-Champaign; University of Illinois at Urbana-Champaign email@example.com
The frigid waters of the Southern Ocean encompass a range of habitats. The high latitudes can experience year-round ice cover whereas the lower latitudes have only seasonal ice cover in many places and more drastic seasonal temperature changes. Fishes of the genus Trematomus that colonized the Southern Ocean occupy niches ranging from bottom dwelling and ice-avoiding, to the sub-ice platelet layer. Although regarded primarily as a high latitude group because of their abundance, Trematomus species are also found in the lower latitudes of the Antarctic Peninsula and South Shetland Islands but in smaller numbers. Freeze avoidance in the Antarctic notothenioids is linked to the presence of antifreeze glycoproteins (AFGPs) and antifreeze potentiating protein (AFPP), both of which adsorb to endogenous ice crystals, inhibiting their growth. Both high and low latitude Trematomids possess AFGP and AFPP, but the relative concentration and contributions to the hysteresis freezing points differ depending upon a number of environmental factors. High latitude specimens of T. bernacchii, inhabiting the anchor/ice platelet layer, have the lowest freezing points (-2.14°C) and highest levels of AFGP and AFPP (53.56mg/mL) while T. loennbergii, a benthic species inhabiting the ice-free deep water, has the highest freezing points (-1.46°C) and lowest levels (39.89mg/mL). The same species inhabiting the low latitude waters have moderately reduced hysteresis freezing points (-1.64°C, -1.02°C) and reduced antifreeze protein levels (40.88mg/mL, 30.02mg/mL) for T. bernacchii and T. loennbergii respectively. How the geographic range and environmental factors associated with range such as seasonal temperature fluctuations and presence of ice has influenced their freeze avoidances is discussed.