April 2020, ScientificAmerican.com 53sheets waxed and waned across the continent as ice
ages came and went across millions of years. Species
such as Tullbergia are also stretching our ideas about
the limits of biology, reinforcing the notion that even
the cruelest environments on Earth can often sustain
complex animal life.
ICE AGE IMMIGRANTS
antarctica is known for its penguins and seals, but these
animals live only on its coastline, fed by a rich food web
of phytoplankton, fish and krill. Those iconic species
cannot survive in the continent’s interior, an area larg-
er than the U.S. and Mexico combined, about 98 per-
cent of which is blanketed in glacial ice sheets.
But starting around 1900, scientists began to find
that ice-free patches of ground, kilometers in from the
coast, were inhabited by animals of a different kind:
tiny springtails, mites, worms and wingless flies called
midges. These creatures required water and often
inhabited small patches of lichens or moss on north-
facing slopes, where 24-hour summer sunlight melted
snow and dampened the soil. Scientists gradually
found them in colder and drier places, farther inland.
In 1964 entomologist Keith Wise flew to Shackleton
Glacier to see if he could find animals in one of the
most secluded inland places on the continent. On
December 13 he skied several kilometers up the glacier
from camp until he arrived at the bottom of the Mount
Speed ridge. Snowmelt trickled down a cliff, wetting
the soil at its base. There Wise found two species of
springtails: gray Antarctophorus subpolaris, which he
had seen before in other places, and ghostly white Tull
bergia, new to science.
In the decades after Wise’s discovery, scientists tried
to piece together a rough history of the landscape where
Tullbergia was found. Seafloor sediments revealed that
Antarctica had experienced 38 ice ages in the past five
million years. During those freezes its glaciers thick-
ened, rising inland and cloaking many of the mountain
slopes that are exposed today. Temperatures were
5 degrees C to 10 degrees C colder than at present. Most
researchers assumed the rising ice sheets “more or less
wiped everything out,” says Steven Chown, a polar ecol-
ogist at Monash University in Melbourne, Australia.
Scientists reasoned that once an ice age ended, the
glaciers thinned, slumping downhill and exposing moreRESEARCHERS
scoop up soil
samples ( 1 )
containing Tull-
bergia on the
scree slopes
of Mount Speed
( 2 ), along Shack
leton Glacier in
Antarctica.2© 2020 Scientific American