Over tens of millions of years, the wingless midge Belgica antarctica has perfected the technique of freezing itself in order to survive Antarctica's darkest and harshest winter months, carving itself an exclusive position as the continent's only native insect.
As climate change raises arctic temperatures, this hard-earned combination of survival abilities may be damaging to its own existence, perhaps driving it to extinction.
Warmer winters in the freezing south had a significant influence on the insect's motions and energy storage, compromising its chances of seeing another summer, according to laboratory trials done by a team of researchers from the United States, the United Kingdom, and South Africa.
The itty-bitty arthropod, which is usually less than a centimeter in length from tip to tail, also happens to be the biggest animal on land that has never set foot in the sea. It spends its whole life cycle, primarily in one of four larval phases, on damp beds of moss and algae, chewing on the greenery and decomposing garbage.
During Antarctica's harsh winters, even these simple havens freeze over, trapping crucial moisture and threatening to turn the tiny animals into popsicles. So, in order to survive the cold, the midge devised a smart plan to escape death and bide its time.
The midge steadily desiccates itself as a defense against the stress produced by ice crystals piercing its tissues. Individuals have a fair chance of surviving summer under the correct conditions, even after losing up to three-quarters of their moisture.
That good possibility is heavily dependent on humidity and whether it rehydrates via water vapor from the air or directly from liquid water. Even little changes in environmental circumstances can have a significant impact on survival rates.
Microclimates like those occupied by the midge tend to hover between -5 and 0 degrees Celsius in the Antarctic Peninsula, an area particularly rich in species (23 and 32 Fahrenheit). Temperatures can drop in the sky above, protected by layers of snow and ice, with no effect on the midge's mossy garden.
With temperatures on the peninsula rising at a rate of up to half a degree every decade, such comparatively sheltered circumstances may be changing. Higher temperatures may result in more precipitation, which means more snow, greater insulation, and a lower risk of winter freezing.
The researchers collected midge larvae from the surroundings of a station on Anvers Island, near the extreme point of the Antarctic Peninsula, to investigate what effect this might have on B. antarctica.
These specimens were subsequently sent to a facility in the United States, where they spent six months living in subtly varied wintery circumstances ranging from -5 degrees Celsius to -1 degrees Celsius. A variety of substrates, including moss and algae, were also examined.
After defrosting in cold water, the survivors were inspected for evidence of movement, tissue damage, and carbohydrate, fat, and protein energy reserves.
The minor temperature change has a significant impact on the midge's recuperation. Under normal conditions, around half of the insects survived. A measly third survived after being warmed by a few degrees. Energy storage also differed dramatically, with cold temperatures retaining more fat and protein stores than warm conditions.
"These results correspond with locomotor activity levels, where larvae from the warm winter regime were slowest, potentially due to energy drain," the researchers write in their article.
"With limited time prior to pupation after winter, and as adult B. antarctica lack functional mouthparts, energy store depletion during late larval instars would likely have irreversible consequences on the energy available for reproduction."
It's difficult to determine what type of long-term impact this would have if temperatures continue to climb. Depending on the strains caused by climate change, it might be a small annoyance or a devastating blow that wipes out whole communities.
However, there may be a silver lining: warmer winters may be shorter, giving the midge more opportunity to amass greater reserves over the summer months.
It remains to be seen if this behavioral check mitigates the detrimental effects of global warming.
With record heatwaves slamming the poles, the sole insect that lives in Antarctica may become yet another casualty of our rapidly changing climate.
This research was published in Functional Ecology.
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