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By Peter Rejcek
Antarctic insect focus of new NSF-funded project
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.
Debugging Belgica
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.
Lamps heat up soil on a mesh screen, sending the larvae
into the pan of cold water below, making them easier to
capture.
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. [See previous article from Nov. 26, 2006
]
“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 wintering over 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.
Comparative studies
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.
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