The influence of environmental temperature on the thermal tolerance of Antarctic notothenioid fishes

• Main Author: Bilyk, Kevin
• Other Authors: DeVries, Arthur L., Cheng, Chi-Hing C., Fuller, Rebecca C., Kwast, Kurt E.
• Language: English
• Published: 2011
• Subjects: Notothenioid; Antarctica; Antarctic Fish; Freeze Avoidance; Heat Tolerance; Critical Thermal Maximum; Antarctic; Southern Ocean; The Antarctic; New Zealand; Antarc*
• Online Access: http://hdl.handle.net/2142/24397

The evolution of the Antarctic notothenioid fishes in the chronically cold waters of the Southern Ocean has resulted in a remarkably narrow thermal tolerance shared among most extant species. While most of these fishes have the capacity to accommodate the physiological challenges of low temperature, they show a greatly reduced tolerance to heat relative to fishes native to warmer waters. Though predominantly distributed in the Southern Ocean, today the Antarctic notothenioids are largely divided by their geographic distributions between three regionally endemic ichthyofaunas in the high-latitude High Antarctic Zone (HAZ), the lower-latitude Seasonal Pack-ice Zone, and cold-temperate waters of southern South America and the South Island of New Zealand. However, the extent to which regional differences in ice abundance and temperature affect the thermal tolerance of their endemic fishes is poorly understood. Within the Southern Ocean the Antarctic notothenioids are largely split between the constantly freezing High-Antarctic Zone (HAZ) and the more thermally variable Seasonal pack-Ice Zone (SPZ). For these fishes, the lower boundary of their thermal tolerance is effectively determined by their capacity for freeze avoidance and limited by their circulating levels of antifreeze proteins (AFPs). To investigate the differences in freeze avoidance between these regions’ endemic ichthyofaunas blood serum freezing points were measured in 11 of the 14 species of the Antarctic icefishes (family Channichthyidae). While the icefishes are a small monophyletic group within the suborder Notothenioidei, they mirror the larger group’s divisions in geographic distribution and lifestyle making this family a useful system for understanding the larger group. Within this family, blood serum freezing point was negatively correlated with the latitude of species’ geographic distributions with the three SPZ species showing the highest freezing points. Either equal to or higher than the freezing point of seawater, these serum freezing ...