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Early burrower may have been worm
By Devin Powell
Worms may have first burrowed into
mud more than 550 million years ago.
The tunnels they apparently created in
the seafloor, preserved in fossilized sediments, could be the earliest example of
animals churning up the ground.
That newly plowed seafloor in turn
might have helped to spur the rise of
new kinds of macroscopic life late in
the Ediacaran period— just before the
Cambrian explosion produced most of
the major animal groups around today.
“We think that Ediacaran organisms diversified as a reaction to habitat
remodeling by … burrowing,” says paleontologist Dima Grazhdankin, coauthor
of a new study published online March
19 in Geology.
Grazhdankin and colleagues found the
fossils in central Siberia, in rock that had
once been mud deep underwater. Tiny,
crescent-shaped traces cutting through
five centimeters of former sediment
looked like small tunnels made by crea-
tures scooping and flinging dirt from
front to back.
Crescent-shaped trace fossils in mud-
stone, shown in a horizontal slice, could
be tunnels dug by primitive worms.
The appearance of bioturbation so
early could even have had a planetwide
impact, says Shuhai Xiao, a paleontologist at Virginia Tech in Blacksburg. But
previous evidence of bilaterians this
early in the fossil record has been controversial, and Xiao says he still needs some
convincing. Since none of the densely
packed traces in the rock crisscross, he
wonders whether the patterns are burrows at all — or simply the imprint of a
creature that died an inglorious death in
Europe bat pest
White-nose syndrome in
U.S. is less virulent strain
By Janet Raloff
The fungal species wiping out hibernating American bats also strikes their
European kin — although it doesn’t kill
them. But that’s not because the European strain of the white-nose syndrome
fungus is less virulent, a new study finds.
“The European version is even nastier than the North American one,” says
Craig Willis, a wildlife biologist at the
University of Winnipeg in Manitoba.
The finding emerged from a trial infecting 36 healthy Canadian little brown bats
with the fungus Geomyces destructans.
Half of the animals got fungus isolated
from North America, the others fungus
from Europe. All animals quickly developed white-nose syndrome, a disease
named for the mask of threadlike fungal
growths it leaves on bat faces. Harder to
see but more devastating, G. destructans
eats through the skin of a bat’s wings and
begins digesting inner tissue.
Bats receiving the European strain of
the fungus died about a month sooner
than those infected with the American strain, Willis and colleagues report
online April 9 in the Proceedings of the
National Academy of Sciences. These
findings suggest the American strain is a
recent immigrant from Europe. Because
the naïve populations the strain encounters in North America die so easily, Willis
suspects that the American strain of the
fungus has evolved to be less deadly.
Jeff Foster, a wildlife disease ecolo-
gist at Northern Arizona University in
Flagstaff, agrees. His team compared the
entire genetic blueprint of G. destructans
from both continents, confirming they
are nearly identical. But slight genetic
variability showed up among strains
from Europe, with no variability in those
from North America. That suggests the
fungus arrived in America recently.