Not much bugs Belgica
Antarctic insect focus of new NSF-funded project
Posted January 29, 2010
Richard Lee stretches his long frame onto the cold, sharp rocks that turn every step on Torgersen Island into a potential ankle-twisting misadventure. His head tilts close to the ground, as if he is about to settle down for a nap, using the dried mat of Prasiola crispa as a pillow. Instead, he carefully flips over the Antarctic green algae to reveal a squirming mass of what appear to be black ants.
They’re insects all right, but no species of ant lives this far south, here on one of the many granite and basalt islets that mark the southern extreme of the Palmer Archipelago off the west coast of the Antarctic Peninsula. These are adult Belgica antarctica, a flightless midge endemic to the continent. The wingless flies are ubiquitous on the islands near Palmer Station, the small U.S. Antarctic Program research base on Anvers Island.
“We have seen more adults than we have ever, ever seen before on all of the islands. Every place we’ve gone. It’s just amazing,” Lee exclaims repeatedly as he and other members of the “buggers” team turn over rocks and algae mats looking for what the entomologists like to say is Antarctica’s biggest terrestrial animal.
The larger fauna like Adélie penguins and elephant seals only spend part of their lives on solid land. So, at a maximum length of about 7 millimeters, Belgica earns its boasting right as Antarctica’s largest land animal a bit by default.
“An amazing number of adults,” David Denlinger agrees, scooping up the mud underneath a rock with a metal spoon and dropping the dark-colored dirt in a Ziploc bag. “But where are the larvae?”
Today the Belgica larvae not on Torgersen, or Torgy, as the station personnel refer to the island, a short boat ride away from the base. The team digs up a few more of the adults, returns the earth to a semblance of its former state, and piles back into an inflatable Zodiac boat. They figure nearby Humble Island, where they’ve had their best success, will save the day’s fieldwork.
Going to extremes
Lee and Denlinger are the principal investigators on a four-year grant from the National Science Foundation’s Office of Polar Programs to study Belgica and its unique cold tolerance abilities.
Both men call Ohio home. Lee is the director of the Laboratory of Ecophysicological Cryobiology at Miami University. His lab is interested in how different critters tolerate the cold, from amphibians to microorganisms. Lee’s specialty is bugs, and his acquaintance with Belgica goes back nearly 30 years when he first visited Palmer Station as a post-doctoral fellow at the University of Houston.
On that trip, he and his colleagues first characterized the stress tolerances of this unique midge — its ability to survive extreme desiccation, losing nearly all its moisture, and survive freezing temperatures that would kill most other related species. Those data were the foundation of a grant proposal that brought Lee back to this remote research outpost on an NSF grant beginning in 2005.
“Now we’re coming back after the molecular revolution with entirely new techniques to look at mechanisms and how they tolerate these stresses,” Lee explains.
He teamed up with longtime colleague Denlinger, a professor in the Department of Entomology at The Ohio State University. An expert in insect diapause — basically how a bug hibernates — Denlinger is interested in understanding the biological mechanics of how critters like Belgica know winter is coming.
It made perfect sense that the two scientists should go to the extreme limits of where insects can survive and still thrive — this wind-blasted region where dark clouds often blanket the region in a Seattle-like dreariness — to learn more about the ultimate winter slumber party.
Belgica is a member of the order Diptera, which includes mosquitoes and flies. They are found only on the Antarctic Peninsula and in a variety of diverse microhabitats, from the small clumps of Prasiola and grasses found on the rocky islands to the well-fertilized mud near penguin rookeries and elephant seal wallows.
Belgica enjoys such a wide range of habitats, filling every conceivable niche, by virtue of its lone terrestrial supremacy. “There are no other competitors down here, nothing even closely related,” Lee says. “They have no predators, no parasites that we know of.”
The midges have a two-year life cycle. They spend most of it as worm-like larvae, up to 6 millimeters long, eating all the bacteria, detritus and algae they can. They molt into adults in the summer, enjoying a brief flowering, two weeks at most, to mate and lay eggs. The eggs, looking like tiny dried tomato seeds, hatch after a week and the new larvae begin feeding.
The team’s arrival in the first year of its new grant timed remarkably well with the emergence of the adults. The scientists have never encountered this kind of abundance before.
“The party will be over pretty soon for them,” says Denlinger, who, like Lee and probably most entomologists, enjoyed a childhood fascination for insects. “Most people I know outgrow that at some point; some of us don’t.”
The team’s research has shown that midges can tolerate the loss of up to 70 percent of their body water. But its major finding from the first grant period between 2005 and 2007 was that Belgica could keep feeding and growing despite the fact that it is in cellular survival mode 24/7. Its heat shock proteins — proteins whose “expression” increases when cells are exposed to elevated temperatures or other stress — are working all the time.
“That’s absolutely not the dogma everywhere else in the world,” Lee says while making a final walk around the northeastern half of Torgersen. “When you turn on those proteins, you stop making everything else. You’re in a survival mode … Down here they’re obviously growing and feeding. At the same time, they’re producing high levels of heat-shock proteins.”
Denlinger adds, “We think having those heat shock proteins on all the time is probably a very important thing for them to survive in these types of environments.”
Weathering the winter
Now Lee and Denlinger are back after about a two-year hiatus with two graduate students and a former member of Lee’s lab with a new grant to collect new specimens to answer a new set of questions.
Foremost among the fresh mysteries for the entomologists is learning more about how Belgica spends the winter in Antarctica. Its freeze tolerance is at work year-round, but possibly enhanced in the colder, dark winter months.
Freeze tolerance in another Antarctic arthropod, Cryptopygus antarcticus, involves cryoprotective dehydration. The tiny springtail, which jumps around like a flea but is not a true insect, gradually loses water and dries out, lowering its freezing point. In the lab, Belgica demonstrates a similar ability.
“That’s never been shown before in a true insect,” Lee notes. The lab is one thing; but does it happen in nature? Perhaps it varies by the microhabitat, he suggests, so that in wetter areas the polar midge simply freezes while in drier patches it cryoprotectively dehydrates.
In a future field season, he says, someone from the team will return to the islands after the summer season, perhaps as late as May, to learn more about that process.
The finch effect
Another goal is to determine just how genetically homogenous Belgica is among the different islands it inhabits. Being wingless, its ability to disperse geographically is pretty limited but not impossible. The wind could help spread it across the closely spaced islands. And they can float on the water as well as a lifejacket.
But it’s more likely that Belgica is a homebody, having probably lived in Antarctica for millions of years, fragmented geographically. The scientists want to know if the relative isolation between islands produces significant genetic differences among the populations.
“It’s sort of like what Darwin saw with his finches, where you have little populations on different islands that are in some ways evolving into different species. We’re going to look for evidence of that occurring in Belgica,” explains Nick Teets, a PhD student who works with Denlinger.
“We’re trying to get populations from as [distant] islands as we can to see if there might be some incipient speciation going on,” Denlinger adds, saying that the team hopes to sequence the Belgica genome in the next year or so to target their research on specific genes involved in over-wintering adaptations.
Climate change concerns?
Teets is also conducting experiments that look at the effects of cyclic cold on the insects — whether repeated freezing and thawing affect survival or stress response.
“It goes along with the whole global warming theme,” he says, explaining that while the general trend of climate change will be increased temperatures over the long term, it will be accompanied by wild shifts in shorter-term climate.
Lee doesn’t think hardy Belgica has too much to worry about from climate change. Temperature loggers placed near Belgica microhabitats during their previous fieldwork recorded a wide range of temperatures over the summer and winter. The larvae can also move up and down in the substrate as surface conditions dictate to protect themselves.
That could explain the absence of the larvae right now on Torgy. The island seems especially dry, the tufts of Prasiola brittle and crisp. When wet, the algal mats ribbon out, Lee notes.
The hunch about Humble at first turns up disappointing results. Master’s student Yuta Kawarasaki is enjoying the most luck, gathering up the eight-legged mite, Alaskozetes antarcticus, which lives in large colonies on relatively dry stones.
He wants the mites and springtails for various comparative studies to Belgica. More specifically, he wants to test whether the little animals’ levels of ATP, adenosine triphosphate, go up as temperature drops. ATP is the chemical energy of the cell that powers its metabolic activities.
ATP levels usually fall with temperature in temperate species that live in warmer climes. But there’s evidence that cold-loving critters actually increase their ATP levels when the mercury drops.
“We don’t know what that exactly means yet but we want to test if that holds true in Antarctic species,” says Kawarasaki, who works with Lee at Miami University.
Fondness for fieldwork
This is Kawarasaki's first trip to the Antarctic.
“It’s fabulous. It’s supposed to be work, but it’s fun, so I don’t know if I should call it work,” he says with his nose almost literally on the frozen ground, scraping mites off a rock and into a small vial.
Juanita Constible seems equally happy to be rolling in the cold Antarctic mud, pulling up rocks and squinting for Belgica larvae in the impressions. A former lab manager and science education writer for the Ecophysiological Cryobiology Lab at Miami University, Constible is a trained wildlife biologist who now works for the National Wildlife Federation as a scientific advisor.
In addition to offering another pair of field hands, Constible maintains the team’s blog for the expedition, explaining the science and uploading photos that show life at a research station, reachable after a four-day cruise across open ocean from southern Chile.
“I just feel incredibly lucky to be here,” she says.
It’s hard not to share that feeling. White noise here is the braying of Adélie penguins and the burping and gurgling of elephant seals piled on top of one another like gigantic slugs, sounding like an underground sewer pipe about to burst.
Still, the work isn’t too sexy. “It’s not just about coming to Antarctica,” Constible notes. “I’m crawling around in muck and seal poo.”
But it turns out to be a good place to crawl around and get slimy. A small snow pack at the top of a short down slope provides just enough snowmelt to moisten the soil below. The larvae are everywhere. Soon the rest of the team is prone, quickly filling up their plastic bags.
Several thousand specimens will be sent stateside for additional lab work, where they can survive for more than a year in a refrigerator with a little Prasiola from home and the occasional spray of water.
A momentary scuffle between adult penguins creates enough of a ruckus for everyone to look and turn, and then they’re back at the business of collecting tiny creatures that could reveal some big discoveries about cold adaptation.
“It’s the little things that run the world — bacteria microbes, phytoplankton — all this other stuff, the bigger animals, are just superfluous,” Lee says.
NSF-funded research in this story: Richard Lee, Miami University, Award No. 0837559; and David Denlinger, The Ohio State University, Award No. 0837613.
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