The Antarctic midge may be smaller than a pea, but it is Antarctica's largest land-only animal and its only native insect. A study recently published in Functional Ecology found that Antarctic midges have evolved to survive in extreme conditions, but climate warming may pose a threat to them.
Unlike temperate zone midges that live in groups in the water, Antarctic midges mainly live in the humid areas of the Antarctic Peninsula and nearby islands. They live a slower pace, with a life cycle of up to two years, and spend most of their time in larval form.
Nicholas Teets, an insect physiologist at the University of Kentucky and one of the authors of the study, said that these brown worm-like larvae "may not look outstanding, but their ability to survive under pressure is excellent."
Midges have spent 40 million years perfecting their survival strategies. They can withstand harsh winter temperatures. To prevent ice damage to their internal tissues, overwintering larvae lose up to 70% of their body fluids. Once the body "freezes," the larvae spend about six months in a suspended state called diapause. During this time, they won't eat, move, or do anything else.
As Antarctica warms rapidly due to climate change, Teets and colleagues wanted to know how small changes in winter temperatures would affect Antarctic midges.
To this end, the research team collected Antarctic midge larvae from several islands near the Antarctic continent and placed them in incubators with three temperatures: -5°C (a cold Antarctic winter), -3°C (a typical winter) and -1℃ (warm winter).
Earlier this month, researchers reported that six months after placing Antarctic midge larvae in incubators, they found that larvae in the "warm winter" incubators had lower survival rates, moved slower, and had smaller energy stores.
Depletion of stored energy could spell trouble for Antarctic midge reproduction. This is because after the larvae recover from diapause, they quickly turn into adults without functional mouths and must rely on their own energy reserves to survive the breeding season.
Entomologist Joshua Benoit of the University of Cincinnati, who was not involved in this work, said that if mild winters "'burn out' more larval refuges, then these larvae will eventually become extinct on some islands."
Because so few species live on land in Antarctica, the loss of even one species could reshape the food chain.
But "it may not be all doom and gloom". "If winters are both warm and short, Antarctic midges can start feeding earlier in the summer, entering the growth cycle and making up for lost reserve energy," Teets said.
Teets said the next step is to monitor Antarctic midge populations in the wild to see how they fare. Respond to temperature changes. But he points out that winter fieldwork in Antarctica is challenging, so documenting any changes may take some time.
Source: Chinese Science Journal
