Extreme Temperature Resilience Conferred by Antifreeze Biomolecules in Distant Taxa

Poikilotherms must overcome many stresses, including fluctuating temperatures of their environment. Upper lethal temperatures (ULTs) of cold adapted insect species in winter have not been previously examined. Consequently, given the recent increases in winter freeze-thaw cycles and warmer winters due to climate change, it became of interest to determine if ambient temperatures during thaws were approaching ULTs during the cold seasons. Larvae of the beetle, Dendroides canadensis, had higher 24- and 48-hour ULT₅₀ (the temperature at which 50% mortality occurred) in winter compared to summer. Additionally, larvae of the beetle, Cucujus clavipes clavipes, and the cranefly, Tipula trivittata, also had higher ULTs in winter compared to summer. With the decreased high temperature tolerance as the season progresses from winter to summer, it was observed that environmental temperatures are closest to upper lethal temperatures in spring. One possible explanation for increased winter high temperature survivorship could be the presence of antifreeze proteins in D. canadensis. This was shown to be the case as transgenic fruit flies, Drosophila melanogaster, expressing individual AFP genes from D. canadensis had increased high temperature survivorship.

The presence of thermal hysteresis factors has not been identified in marine mammals. The bowhead whale Balaena mysticetus is an endemic whale in the Arctic and spends most of its time in or near sea ice where the water temperature can be -1.8°C. Thermal hysteresis activity, indicative of the presence of antifreeze proteins or antifreeze glycolipids, was detected in the skin of bowhead whales collected from the arctic ocean near Barrow Alaska. The whale thermal hysteresis producing factor is a protein.

Insects produce various cryoprotectants including antifreeze proteins (AFPs), antifreeze glycolipids (AFGLs), polyols such as glycerol, and sugars such as trehalose in response to winter. These adaptations could be used to improve current protocols for cryopreservation of human cells, tissues or organs for use in transplant surgery or for research purposes. AFGLs from insects, larvae of the cranefly, T. trivittata and the stag beetle, Ceruchus piceus, and mannose-xylose disaccharides based on the carbohydrate component of the insect AFGL, resulted in enhanced cell viability of rat aorta cells after cryopreservation.