Scientists Find How Crickets Recover From Chill-Coma

A new study sheds light on how insects recover from chill-coma, which will help in managing agriculture and biodiversity in the wake of climate change, researchers say.

Chill-coma is the paralyzed state of the insects when they get exposed to unfavorable low temperatures. The insects appear to be dead, but are alive and unable to move. They lose their muscle function completely, but can become normal within seconds of return to favorable temperature conditions. 

A team of researchers from University of Western Ontario in Canada examined fall field crickets to study how they recover from chill-coma. They found that the recovery depends on resolving water and salt imbalances that show up when the insect is cold.

"Insects lose the ability to maintain proper water balance in the cold so when they are chilled, water and sodium move from the insect blood, called hemolymph, into their gut," says Heath MacMillan, a PhD student from University of Western Ontario. "This is bad for the insect because it concentrates potassium in the blood that remains, which leaves muscles unable to function."

MacMillan and his colleagues noticed that the crickets were able to restore normal hemolymph potassium concentration in order to make their muscles work again. This allowed the insects to move, but it does not mean that the physiology of the crickets have returned to normal, he says.

"Crickets still need to restore sodium and water balance," he explains. "We measured the metabolic cost of this reboot and found that the process increased a cricket's metabolic rate by as much as 50 per cent for a few hours."

Experts suggest that the study will help in predicting how different insects respond to varying temperatures. It will lead to better management of agriculture and biodiversity in a changing climate, they say.

The findings of the study, "Reestablishment of ion homeostasis during chill-coma recovery in the cricket Gryllus pennsylvanicus", are published in the journal Proceedings of the National Academy of Sciences (PNAS).