Across the South Pole’s frozen expanse, there lives only one purely terrestrial animal: a tiny insect called the Antarctic midge. This flightless creature, just 0.2 inches long, has eked out an existence in one of the world’s most unforgiving climates for some 30 million years, since its home continent split off from South America.
Researchers have studied these midges for decades, documenting their impressive resistance to extreme conditions. But it was never clear how they endured the frigid polar winter. Now researchers at Japan’s Osaka University have uncovered the physiological mechanism behind Belgica antarctica’s mastery of the cold — one that’s never been observed in any other species.
Cold Temperatures for an Insect
Like hibernating bears, many insects slow their bodily processes during the tough winter months. But for them dormancy comes in two distinct flavors. The first, called quiescence, relies on environmental cues — when temperatures plummet, metabolism automatically tapers off. The second, called diapause, is genetically programmed to kick in at a specific stage in biological development, regardless of what the weather’s doing.
Quiescence and obligate diapause have different advantages, and most insect species opt for one or the other. The Antarctic midge, however, employs both during its two-year life cycle. It’s an unprecedented combination. Lead author Mizuki Yoshida, now a postdoctoral researcher at Ohio State University, explains that this helps them make the most of the short summers.
It’s an ingenious strategy. During their first winter, midges go with quiescence because it “enables a swift transition between active and inactive lifestyles,” as Yoshida and her colleagues wrote. They wake up whenever temperatures rise above a certain threshold, allowing them to maximally exploit these balmy periods for feeding and growth.
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Going Dormant for Development
That works great for the first year, when every individual is just wandering alone in search of a meal. But the second winter complicates things: Once it’s over, an entire generation must come out at once, ready to reproduce in the few days they have left on Earth. If they aren’t synchronized, it could spell doom for the species.
The problem is that thousands of midges don’t necessarily mature at the same rate. If they were all plunged into quiescence without warning one autumn day, due to a sudden drop in temperature, they’d be caught in various stages of development. And then, come summer, they’d emerge in those various stages, many of them still sexually immature.
Obligate diapause solves this by ensuring that the whole population goes dormant just before pupation, the final transformation from larva to adult. Each midge follows its own timeline, with late bloomers waiting longer than their precocious counterparts to bed down for the winter. That way they all emerge on the same developmental schedule when the snow melts, and glorious reproductive success ensues.
Surviving Extreme Conditions
No other insect is known to switch between quiescence and obligate diapause. But under the right circumstances it seems like a logical game plan, given the peculiar demands of an inhospitably cold environment. In fact, Yoshida suggests that it could be a common strategy for species living not just in Antarctica, but also in Arctic and alpine zones.
It may be a while till that’s confirmed, though, considering it took the Osaka team 6 years to establish a method for rearing Antarctic midges in the lab (ironically for such hardy creatures, Yoshida says it was difficult to determine what temperatures they preferred).
So for now they stand in a class of their own — and their adaptability is “a testament,” as the authors put it, “to the resilience of this species in the face of extreme challenges.”
Read More: What the Mysterious Bloop Taught Us About Antarctica
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Cody Cottier is a contributing writer at Discover who loves exploring big questions about the universe and our home planet, the nature of consciousness, the ethical implications of science and more. He holds a bachelor’s degree in journalism and media production from Washington State University.
