Field Notes: Nature's Antifreeze
Walking from my truck into work last week, I noticed a frail looking insect flitting along the surface of the snow on the trail in front of me. On closer inspection, it was a stonefly. Stoneflies are small insects that live most of their lives in streams and rivers, emerging only to complete their reproductive life cycle. Like stone flies, many aquatic insects, including many flies, mosquitos, dragon flies and damselflies have a life cycle that is partly in water and partly above water. But, most of these species emerge and take flight in spring and early summer. Standing in the snow with my toes beginning to numb, I watched the tiny stone fly contentedly siting upon the bright white snow and wondered why it didn’t look as cold as I felt.
While hibernation is a well-known strategy for winter survival, other organisms possess unique biochemical adaptations that allow them to thrive and survive in wintery conditions. Antifreeze proteins are naturally found in multiple cold climate organisms and work by grabbing onto existing ice and preventing it from binding with more water particles. They block the crystallization of ice. First discovered in Antarctic fishes, antifreeze proteins have now been identified in over 120 cold water fish species and it is clear that these chemicals have evolved multiple times across lineages. The antifreeze proteins in Antarctic fishes lower the freezing point of their blood allowing them to survive even the coldest temperatures of the Southern Ocean. Some fish even live within insulated pockets of ice.
Locally, the stonefly I observed is just one of a list of insects that produces glycerol and antifreeze proteins to stay active through winter. Snow fleas, some tick species, a range of beetles and the larvae of many moths and butterflies use these chemicals to reach supercool temperatures before they are threatened with freezing. Resisting freezing is only effective down to certain temperatures. It allows organisms to interact with ice and live within snow where temperatures are regulated by the insulating forces of these frosty materials.
Extreme cold is still a threat. In regions where extreme temperatures are common, some insects and aquatic creatures use antifreeze-like ice binding proteins to control ice crystal formation in ways that don’t harm their cell structure and tissues. They undergo successful cryonic freezing! One extreme example is the Alaskan Upis beetle. It uses antifreeze proteins to stay active in temperatures down to -19 degrees Fahrenheit at which point its supercooled body fluid freezes without killing the insect. They can survive temperatures down to -100 degrees Fahrenheit in their frozen state.
With so much variety across organismal groups, the diversity of natural antifreeze and ice structuring proteins hold great intrigue for food science and medical researchers. Already, fish antifreeze proteins have been cultivated in laboratories and added to Popsicles and ice cream. They act to reduce crystallization if ice cream goes through a freeze/thaw cycle and can even increase the melting temp of our favorite frozen treats. Additional researchers are studying how to use the proteins to lengthen the shelf life of frozen foods and to extend cold tolerance in crop plants, increasing yields in colder climates. In medicine, antifreeze protein technologies are being developed to improve tissue preservation for transplant organs and during cold surgeries and to treat hypothermia and frostbite. Will these chemicals be the key to future cryogenics?
Who knows? But as you walk the forests this winter, look for the flitter of wings across the snow's surface and tiny moving specks near the base of trees. These active winter insects are taking advantage of one of nature's amazing technologies.