The Antarctic midge might be smaller than a pea, but it’s the continent’s largest land animal–and only native insect. The midge has clearly evolved to survive in extreme conditions, yet a warming climate could threaten its existence, a new study finds.
Unlike temperate-zone midges that swarm around water, the Antarctic midge (Belgica antarctica) is flightless and lives in moist pockets of earth on the Antarctic peninsula and nearby islands. It also lives at a slower pace, taking 2 years to complete its life cycle and spending most of its life as a larva. The brown, wormlike juveniles “are not remarkable in appearance,” says Nicholas Teets, an insect physiologist at the University of Kentucky and an author of the study. “But they’re remarkable in their ability to survive stressful conditions.”
The midge has had 40 million years to perfect its survival strategy. It withstands the brutal winter temperatures the same way eccentric billionaires preserve themselves in science fiction movies—they freeze. To prevent internal tissue damage by ice crystals, overwintering larvae lose up to 70% of their body fluids. Once their bodies are frozen, the larvae spend about 6 months in a suspended state called diapause, during which they don’t eat, move, or do much of anything.
With Antarctica warming fast as a result of climate change, Teets and colleagues wondered how small changes in winter temperatures might affect the midges. To find out, they collected larvae from several islands off mainland Antarctica and placed them in incubators set at three temperatures: –5°C (representing a cold Antarctic winter), –3°C (a typical winter), and –1°C (a warm winter). After 6 months, the researchers found the larvae in the warm winter incubator had lower survival, slower movement, and smaller energy stores than those in the colder conditions, they reported in Functional Ecology earlier this month.
The depleted energy stores could spell trouble for midge reproduction. Larvae come out of diapause and quickly become adults that don’t have functional mouths, so they rely on their reserves to get through the breeding season. If warmer winters mean the larvae “burn through a lot more of [their] reserves … eventually, you’ll end up getting extinction from certain islands,” says entomologist Joshua Benoit of the University of Cincinnati, who was not involved in the work. Because Antarctica has few species that live only on land, the loss of just one could reshape the food web.
But, “It may not be all doom and gloom,” Teets says. “If the winter is both warmer and shorter, then they could start their feeding and growth cycle sooner in the summer,” making up for lost stores.
A next step, Teets says, is to monitor midge populations in the wild, and see how they are responding to changing temperatures. But he notes winter fieldwork in Antarctica—when the ground is frozen solid—is challenging, so it could take some time to document any changes.