How terrible is the only insect that can live in Antarctica?

Compared to the Arctic, Antarctica is much more desolate . More than 95% of its area is covered by ice and snow all year round. The Drake Passage, the widest strait in the world, separates Antarctica from other continents in the Southern Hemisphere. The Antarctic Circumpolar Current is like an invisible barrier that isolates warm currents from Antarctica.

This desolation is also reflected in the diversity of insects: there are more than 2,000 known species of insects in the Arctic, but there is only one native insect in Antarctica , the Antarctic midge ( Belgica antarctica ).

Although the name contains "mosquito", the Antarctic midge actually belongs to the Chironomidae family, and is not the mosquito we are familiar with that bites people. The adult Antarctic midge also has no wings and mouthparts for sucking blood. (Image source: wiki)

As early as the end of the 19th century, the Belgian Antarctic Expedition first discovered this chironomid near the Gerlache Strait on the Antarctic Peninsula. As the sampling range of subsequent researchers gradually extended southward, the distribution range of Antarctic chironomids also expanded all the way south, exceeding 69° south latitude. But from beginning to end, only this native insect was found in the Antarctic Circle.

Survival is not easy

If you want to live in Antarctica, the cold is the biggest challenge. Even if you don't go deep into the vicinity of the South Pole, the winter temperature can reach tens of degrees below zero in the Antarctic Peninsula, which is at a relatively low latitude (within the Antarctic Circle). Fortunately, thick ice and snow can sometimes be an excellent thermal insulation material. The land here is blown by strong winds of more than ten meters per second, and the polar night will experience 19 hours of darkness every day. For most of their lives, Antarctic midges hide in the soil under the ice and snow, enjoying the warmth of the ice and snow .

Measurement data show that in the soil about 1 cm deep, the temperature will not drop below -2 degrees Celsius for more than 300 days a year, and even on the coldest days, it will not drop below -5 degrees Celsius.

Even in sub-zero temperatures, the Antarctic midge has a way to avoid being frozen into ice . Their hemolymph (the "blood" of insects) contains natural antifreeze , the main components of which are erythritol, glucose and trehalose. The principle is similar to spreading salt on the streets in winter to melt snow. These ingredients can lower the freezing point of the liquid in the Antarctic midge's body, preventing it from forming deadly ice crystals in the body that damage tissues, especially cell structures.

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In addition to the cold, Antarctica has another fatal problem that is easily overlooked - lack of water . The continuous sub-zero temperature not only means that body fluids will freeze, but also turns almost all possible liquid water into a solid state. Water is the source of life, but ice is not. In a cold environment, most organisms cannot use solid ice. But Antarctic midges not only have a strong ability to resist dehydration, they can even use this.

Unlike the main way for organisms in the desert to resist drought - reducing water evaporation. Antarctic midges use the difference in vapor pressure between the body and the outside world to put themselves into a " protective dehydration state ." Researchers have conducted tests in the laboratory and found that in the most extreme cases, Antarctic midges can tolerate nearly 70% dehydration . In contrast, humans will suffer cognitive impairment after losing 2% of their body weight in water.

More importantly, under extreme dehydration conditions, the concentration of "antifreeze" in the hemolymph and intracellular fluid increases, which can further reduce the melting point and avoid freezing. The entire dehydration process is very rapid, and when the environment warms and the humidity increases, the Antarctic midge larvae can quickly "rehydrate" - the larvae can endure at least 4 dehydration-rehydration cycles to adapt to natural humidity fluctuations.

Aligning breeding season

Even if the Antarctic midge can ensure that it does not turn into a piece of ice, in such a harsh environment, every energy expenditure still needs to be carefully calculated - hibernation becomes a very cost-effective option.

For many invertebrates, there are generally two types of dormancy. One is called quiesce , a process that is a bit like hibernation in snakes and is mainly driven by external environmental conditions . When the external environment is harsh enough, such as when it is cold to a certain degree, the body will quickly stop unnecessary life activities and quickly enter a quiescent state. At this time, insects only need a small amount of nutrients to sustain life. When spring comes, the body can quickly recover and regain vitality.

The other type of hibernation is not so "casual". It is written in the "original code" of organisms and is called diapause . When the larvae develop to a certain extent, they will actively stop developing and enter another dormant state. At this time, the cell division of the larvae is almost stagnant, and the metabolism is greatly slowed down until the "program conditions" that meet the requirements for terminating dormancy are met. Generally speaking, insects tend to only adopt one strategy between diapause and dormancy, but a recent study published in Scientific Reports found that Antarctic midges combine these two methods to survive the harsh winter in Antarctica.

The life span of Antarctic midges is about 2 years, most of which exist as larvae. In the first winter, the second-instar larvae will enter a dormant period. The advantage of the dormant period is flexibility . Once the environment is suitable, they can quickly recover and seize every opportunity to grow.

However, in the winter of the second year, when the Antarctic midges enter the final stage of larvae and should be preparing to pupate into adults, they are not in a hurry. Researchers have found that at this time, the larvae of the Antarctic midges will stop developing and enter a dormant period. This forced dormant stage will end with the beginning of low temperatures in winter, at which time the larvae will slowly begin to pupate, transform into adults, and reproduce the next generation in the summer of the second year.

Mating Antarctic midges (Image source: RE Lee/Iryna Kozeretska et al., 2021)

This seemingly time-wasting practice is actually a special measure taken by Antarctic midges to seize the precious breeding season.

After the Antarctic midge emerges from its pupa, the adult can only survive for less than 10 days. They need to find the same age within a few days to complete mating and give birth to offspring. Therefore, the dormancy "program" written in their genes becomes the key to ensure that they can become adults at the same time and align their breeding seasons .

In the summer of the second year, female Antarctic midges lay eggs wrapped in mucus in mosses and soil (the mucus also has the effect of resisting dehydration and keeping warm). The egg-laying process will damage the abdomen of female Antarctic midges, so most of them will die soon after laying their only batch of eggs. After about 40 days, these eggs will hatch new Antarctic midge larvae, which will once again demonstrate their survival skills in the frozen environment.

A new life cycle begins again.

References

[1]https://www.nature.com/articles/s41598-025-86617-4

[2]https://www.eurekalert.org/news-releases/1072917

[3]https://onlinelibrary.wiley.com/doi/10.1111/1744-7917.12925

[4]https://www.nature.com/articles/ncomms5611

[5]https://besjournals.onlinelibrary.wiley.com/doi/full/10.1111/1365-2435.12229

[6]https://www.uc.edu/news/articles/2019/02/n2069513.html

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Source: Global Science (ID: huanqiukexue)

Editor: Zhong Yanping

Proofread by Xu Lailinlin

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