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 Researchers said on Thursday they have ruled out some possible
culprits including fungi, some parasites and certain other
microorganisms and are taking a hard look at whether viruses or
bacteria may be to blame.
The starfish, also called sea stars, are being obliterated by an
unexplained wasting disease that causes white lesions to appear
before the animal's body sags and ruptures and it spills out its
internal organs.
"The magnitude of it is very concerning. There's the potential that
some of these species could actually go extinct," said Cornell
University ecologist Drew Harvell, one of the scientists involved in
the loosely organized search for a cause.
Harvell said she is concerned because the mysterious pathogen is
affecting 18 different West Coast species along their entire range.
Pathogens that affect an animal's range in such a way like a fungus
that has targeted frogs can be particularly damaging, she said.
The disease appeared last year and is showing no indication of
abating. "I wish we had a sign that it was petering out, but believe
me it definitely is not," Harvell said.
The scientists seem to have more questions than answers.
"What is it that has caused this? Where did it come from? If it's
exotic, how did it get here? Is it something that's likely to be
repeated?" asked Pete Raimondi, chairman of the Department of
Ecology and Evolutionary Biology at the University of California,
Santa Cruz.
Raimondi expressed concern that the disease that is killing the
starfish could be a harbinger of bad things to come for other marine
species. "This is a really difficult disease in lots of ways because
it's very virulent," Raimondi said.
The researchers noted that starfish were the victims of previous
diseases in past decades that reduced their numbers, but the current
one is more serious.
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The scientists are wondering whether the starfish have been infected
by a virus, bacterium or something else unwittingly imported to the
region or whether a pathogen already present somehow became more
dangerous, Raimondi added. Scientists prefer to call the animal a
sea star rather than a starfish because these marine creatures are
not fish but rather echinoderms, cousins of sand dollars, sea
cucumbers and sea urchins. Most have five arms, although some have
many more.
They are remarkably durable creatures, and when healthy are able to
regenerate lost limbs. They are predators and use suction to pull
shells apart to get at the soft body inside. When the shells are
pried opened, the starfish pushes its stomach out of its body and
into the prey, secreting enzymes that digest the victim's soft body
parts.
They are significant predators in their ecosystems, the scientists
said.
"These animals are really important ecologically. If they do go
extinct, or at least ecologically extinct for some period of time,
there undoubtedly would be some really huge impacts on the
ecosystems that they live in," said Bruce Menge, a marine community
ecologist at Oregon State University.
(Reporting by Will Dunham; editing by Andrew Hay)
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