Antifreeze glycoprotein in a “southern” population of atlantic tomcod, Microgadus tomcod

Abstract

1. 1. A Long Island, New York population of the Atlantic tomcod, Microgadus tomcod, initiated antifreeze glycopeptide production in late fall (water temperatures were about 10°C). 2. 2. Significant quantities occurred in midwinter specimens exposed to ice covered marine field conditions and sub-zero temperatures. 3. 3. Increased antifreeze activity over a 3 month period was indicated by an increase in the total freezing point depression from 0.53 to 0.83°C. 4. 4. A reliable estimate of antifreeze activity is the difference between the freezing and melting temperatures of tomcod plasma samples; termed, thermal hysteresis. 5. 5. This thermal hysteresis increased from 0.05°C to approx. 0.5°C in midwinter samples; a value markedly greater than that measured in a comparable New Brunswick tomcod population.