January/February 2019^ DISCOVER^45
CLOCKWISE FROM LEFT: JAY SMITH; MICHAEL POLITO/LOUISIANA STATE UNIVERSITY; THOMAS SAYRE MCCHORD AND HANUMANT SINGH/WHOI AND NORTHEASTERN UNIVERSITY; CASEY YOUNGFLESH/STONY BROOK UNIVERSITY
Zero in ona Frog KillerA May study in Science
has revealed the
long-sought origin of
a catastrophic fungus
that’s making frogs, well, croak.
Populations of more than 200
amphibian species, mostly frogs,
began tumbling late last century. In
1999, researchers linked the deaths
to specific strains of the fungus
Batrachochytrium dendrobatidis,
or Bd, which attacks the animals’
skin. Frogs use their skin for
respiration, and the damage caused
by certain strains of Bd can disrupt
this function and lead to death.
It’s estimated that Bd has already
imperiled a third of the entire global
amphibian population.
For decades, scientists have
hunted for Bd’s geographic origin.
The Science study finally revealed
both Bd’s birthplace — the Korean
Peninsula — and a timeline for the
emergence of its deadly strains: 50
to 120 years ago.
The new research was the result
of a decade-long effort to sequence
scores of Bd genomes from six
continents and compare them
with previously published samples.
When the analysis was complete,
researchers identified four major Bdlineages, one of which was found
only on the Korean Peninsula.
The Korean lineage was more
genetically diverse than the other
three, suggesting the other lineages
originated from it, says Simon
O’Hanlon, an infectious disease
epidemiologist at Imperial College
London and co-author of the study.
Although Bd appears to have
existed for thousands of years on
the Korean Peninsula, there’s no
evidence that it caused any massive
die-offs before the 20th century,
when the lethal strains appear to
have evolved. Their emergence
coincided with an increase in
amphibian exports — for food,
traditional medicine and even pets
— from the region. Researchers
aren’t sure if Korean frogs have
a natural immunity to the deadly
strains, or if these particularly nasty
forms of Bd evolved after the fungus
spread beyond its ancestral home.however: The population there has
dropped by 70 percent over the last
few decades.
Scientists suspect climate
change is behind the decrease.
Sea ice, crucial to krill habitat,
is diminishing, while an uptick
in air temperature has brought a
lot of rain along the west coast.
“Rainstorms ood the nests and
can freeze the chicks,” says Lynch.
The penguin decline in the west
has made the Danger Islands
populations in the east all the
more signiicant. The islands
had not been considered for
environmental protection, says
Lynch, but thanks to her team’s
documentation of their robust
penguin colonies, the area is now
being considered for safeguarding.
“Where climate change has not
had major impact yet, we still have
biodiversity thriving,” says Lynch.
“We still have these amazing,
awe-inspiring animals.”Teensy-Weensy
A Brazilian fly,
Megapropodiphora
arnoldi, is the smallest fly
ever found, measuring
less than 2/100 of an inch.
But its comparatively
huge forelimbs inspired its
discoverer, Brian Brown of
the Natural History Museum
of Los Angeles County, to
name it after muscle-bound
Arnold Schwarzenegger
in January.TOP: BERT WILLAERT/NATURE PL.COM. INSET: ALEX HYATT/CSIRO LIVESTOCK INDUSTRIES’ AUSTRALIAN ANIMAL HEALTH LABORATORY.BOTTOM, CLOCKWISE FROM LEFT: B. BROWN; I. STRAZHNIK;T. HAYDEN/BIODIVERSITY DATA JOURNAL/JAN. 24, 2018 CC BY 4.0Globally, frogs are
being imperiled by
the fungus known
as Bd (inset).