For tens of millions of years, the wingless mosquito Belgica antarctica has perfected the art of freezing itself to penetrate Antarctica’s darkest and coldest winter months, carving an exclusive niche as the continent’s only native insect.
As climate change pushing polar temperatures ever higher, this hard-earned set of survival skills could ironically be damaging to its existence, potentially putting it on the brink of extinction.
Laboratory experiments conducted by a team of researchers from the US, UK and South Africa showed that warmer winters in the frozen south had a major impact on the insect’s movements and energy storage, increasing the likelihood that it would see another summer. was endangered.
Usually less than an inch from tip to tail, the tiny arthropod also holds the unlikely position of being the largest animal in the country to never put a toe in the ocean. The entire life cycle — usually spent in one of four larval states — takes place amid damp beds of moss and algae, munching on the green and rotting detritus.
Even these humble havens freeze during Antarctica’s bitter winters, trapping precious moisture and threatening to turn the little critters into popsicles. So to fend off the cold, the mosquito developed a clever strategy to avoid death and bide its time.
To protect against the trauma caused by ice crystals piercing its tissues, the mosquito slowly dehydrates itself. Under the right circumstancesindividuals have a good chance of getting through the summer even after losing as much as three quarters of the moisture.
That good chance strongly depends on the humidity and whether it rehydrates with water vapor from the air or absorbs it directly from liquid water. Even small changes in environmental conditions can make a big difference in survivability.
In the Antarctic Peninsula – a region relatively rich in biodiversity – microclimates like that of the mosquito tend to fluctuate somewhere between -5 and 0 degrees Celsius (23 and 32 Fahrenheit). Protected by layers of snow and ice, temperatures in the atmosphere above can plummet, with little effect on the mosquito’s mossy garden.
With temperatures on the peninsula steadily rising by as much as half a degree every decade, those relatively sheltered conditions could change. Higher temperatures can mean more precipitation, so more snow, thicker insulation and less chance of freezing in winter.
To see exactly what effect this would have on B. antarcticathe researchers collected mosquito larvae from the vicinity of a station on Anvers Island, at the very tip of the Antarctic Peninsula.
These specimens were then sent back to a lab in the US, where they spent six months under subtly different winter conditions, ranging from a chilly -5 degrees Celsius to a balmy -1 degree. Different types of substrate, such as moss and algae, were also tested.
When thawed in ice water, the survivors were examined for signs of movement, tissue damage and energy stores of carbohydrates, fats and proteins.
That small temperature difference had a profound effect on the mosquito’s recovery. Under normal circumstances, about half of the insects survived. Warmed up only a few degrees, only a third survived. Energy reserves also varied considerably, holding more fat and protein reserves in cold conditions than in warmer ones.
“These results are consistent with locomotor activity levels, where larvae from the warm winter regime were slowest, possibly due to energy drain,” the researchers note in their report†
“With limited time prior to pupation after winter, and as an adult B. antarctica lack of functional mouthparts, depletion of energy supply during late larval stages would likely have irreversible effects on energy available for reproduction.”
It’s hard to say what the long-term impact would be if temperatures continue to rise. Depending on the stresses of climate change, it could be a minor inconvenience or a blow that wipes out entire populations.
There is, however, a possible silver lining: warmer, winters can also be shorter, giving the mosquito more time to gather larger stores during the summer months.
Whether this behavioral check offsets the negative impact of a warming environment remains to be measured.
With record heat waves by breaking the poles, the only insect that calls Antarctica home could become another victim of our rapidly changing climate.
This research was published in Functional Ecology†
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