By
Vedrana Simičević, New Scientsts, 6/22/17—Olms, amphibious salamanders
that live in the western Balkans and Italy – are extreme divers,
reaching depths in excess of 100 metres in dark lakes inside limestone
caves.
A team of divers and biologists has now found the curious creature 113 metres below the surface of such a lake in Croatia.
“This was the deepest finding of the olm ever recorded,” says team leader Petra Kovač-Konrad.
Proteus anguinus is commonly dubbed the “human fish” because of its pinkish pale skin, and the creatures were once believed to be baby dragons. They are noted for their slow lifestyle and long lifespan: these blind animals can live up to a century.
Little
is known about olms, and it is a race against time to find out more as
the salamanders’ underground habitat is being contaminated by pollution
from human activities on the surface. The animals are notoriously
difficult to observe in their natural habitat, except through the
complex and dangerous skill of cave diving – although technology may be
about to change that.
Croatian and international cave divers have found five new olm habitats in the past six years as part of the project run by Croatian association Hyla.
The lake where the creature was seen at record depth, Zagorska pec, is
of particular interest as, unusually, several specimens have turned up
there.
“We
spotted specimens at many different depths in the lake, which confirms
the assumption that depth of the water isn’t the stress factor for the
olms,” Kovač-Konrad says. “We also noticed that olms prefer specific
parts of the cave system with less stressful conditions, such as slower
water flow or bigger amount of sediment.”
Recent discoveries of potential new habitats have been made using environmental DNA from cave water once it surfaces, and there are efforts to breed olms in captivity.
Most observations of their behaviour involve captive animals, mainly in
underground laboratories such as the ones in Postojna or Tular caves in
Slovenia.
“Study
of the olms in greater depths is extremely important, especially when
done by divers focused on conservation,” says biologist Gregor Aljančič,
head of the Tular cave laboratory. He suspects the olm will be found
even deeper than the current record. “Our previous findings indicate
that Proteus can withstand significant pressure.”
But
it could be that the depths cave divers can reach will be the main
determiner of how far down we find olms, says speleologist and biologist
Gergely Balázs, of the international Proteus Project based in Bosnia and Herzegovina.
As
for conserving the animals, information about their geographical spread
will be more important than knowledge of the depths they can live at,
he says.
“In
some caves all across the olm’s distribution range you would see only
one, and in other places you would see 200 of them during a dive,” says
Balázs. “And there are some places where you can’t find any, but we
still don’t know why.”
Balázs’s team is now trying to install infrared cameras in the caves to film the olms going about their business.
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