By Reese Green
As we lace up our boots, pull on brightly colored jackets, and stuff our hands into gloves to combat the cold, insects are undergoing a far more dynamic, chemically driven process. Insects prepare for freezing temperatures gradually through several internal physical changes. Crickets can lower the temperature at which their bodies freeze, decrease the amount of freezable water in their bodies and lower their rate of metabolism. However, these ingenious coping mechanisms pose potential health problems when sustained for long periods of time and can result in the buildup of toxins and cellular damage. Crickets and other freeze tolerant insects have developed a carefully coordinated system to both protect them from the cold and prevent them from doing damage to their own bodies. These complicated processes behind freeze tolerance could offer a potential model for how to safely preserve live tissues in extreme conditions and may apply to the future of cryopreservation.
Janita Toxopeus, a corresponding author at the University of Colorado, led a recent study on insect freeze tolerance. Her group developed a program to provoke freeze tolerance in crickets, specifically in Gryllus veletis. They decreased the temperature and the daylight time to mimic a natural, autumnal habitat. After a six week period, they discovered the crickets that successfully acclimated to freezing temperatures produced lightweight chemicals called cryoprotectants. These chemicals prevent cellular damage when something is frozen.
They then focused on how gene expression changed as a cricket’s body composition prepared for colder temperatures. The scientists found no differences in expression after the cricket had acclimated, suggesting these internal adjustments may be a response to environmental factors, and not clearly set within the crickets’ DNA.
However, changes in DNA expression do coordinate with some freeze tolerance mechanisms. Insects become freeze tolerant as the cold season approaches, altering how membranes and proteins are constructed, by incorporating heat shock proteins, antifreeze proteins, and aquaporins to prevent damage. The combination of environmental and genetic responses suggest crickets have both preventative and mitigative tactics to handle cold temperatures.
This study suggests the pathways underlying insect freeze tolerance are much more complicated than perhaps originally supposed. Although crickets may seem like a very small case study, understanding how organisms interact with and survive in harsh environments can have a wide range of applications. However far off it may be, studying freeze tolerance in live organisms may serve as a potential pathway to refining our own techniques in cryopreservation, and lead to improved technology for preserving sperm, eggs, and organ donations.
References:
Toxopeus, J., Des Marteaux, L. E., & Sinclair, B. J. (2018, October 26). How crickets become freeze tolerant: The transcriptomic underpinnings of acclimation in Gryllus veletis. Retrieved February 6, 2019, from https://www.sciencedirect.com/science/article/pii/S1744117X18300753#!