Will Dunham PlanetArk 18 Nov 14;
Scientists investigating a huge die-off of starfish along North America's Pacific coast have identified a virus they say is responsible for a calamitous wasting disease that has wiped out millions of the creatures since it first appeared last year.
The scientists said on Monday they identified the pathogen as the Sea Star Associated Densovirus, or SSaDV, after ruling out other possible culprits including certain bacteria, protozoans and fungi.
More than 20 species of starfish, also called sea stars, from southern Alaska to Baja California are dying from a wasting disease that causes white lesions to appear before the animal's body sags, ruptures and spills out its internal organs.
"They basically fall apart into a pile of goo on the bottom of the seafloor," said Cornell University biological oceanographer and microbial ecologist Ian Hewson, who led the study in the journal Proceedings of the National Academy of Sciences.
SSaDV is a parvovirus, a tiny form of virus that can cause illness in animals and people.
The researchers detected it in older starfish samples, museum specimens from as early as 1942. They said it may have been present at low levels for years and only recently became a large-scale threat due to some kind of viral mutation, environmental trigger, starfish overpopulation or other factor.
"It's probably the largest epidemic in marine wildlife that we know of," Cornell ecologist Drew Harvell said.
"That's the million-dollar question in all this: Why now? What is it that changed that created the conditions for this outbreak? And we don't have the answer to that. But certainly a viral mutation would be one explanation," Harvell added.
The disease was first spotted in June 2013 and has shown no signs of slowing.
"There are 10 million viruses in a drop of seawater, so discovering the virus associated with a marine disease can be like looking for a needle in a haystack," Hewson said.
"Not only is this an important discovery of a virus involved in a mass mortality of marine invertebrates, but this is also the first virus described in a sea star."
Scientists prefer calling them sea stars rather than starfish because they are not fish but rather echinoderms, cousins of sand dollars, sea cucumbers and sea urchins. Most have five arms, although some have more.
The disappearance of so many starfish threatens to disrupt coastal ecosystems because they are important predators in the waters between the shoreline and open sea, the researchers said.
(Editing by Sandra Maler)
Virus blamed for starfish deaths along US Pacific Coast
AFP Yahoo News 18 Nov 14;
A mysterious virus affecting starfish along the US Pacific coast causes the limbs of the sea stars to …
Washington (AFP) - A mysterious plague that has killed off millions of starfish along the US Pacific Coast since 2013 is now believed to be a virus that causes the creatures to melt, US researchers said Monday.
Known as densovirus, the microorganism has been found in diseased and dead starfish, and is the likely culprit for the massive upsurge in deaths, said the report in the Proceedings of the National Academy of Sciences.
The virus causes the limbs of starfish, or sea stars, to pull apart and their skin to waste away, and has been wreaking havoc on populations from Baja, California, to southern Alaska.
Ian Hewson of Cornell University led the genomic analysis on sea star associated densovirus (SSaDV), a type of parvovirus commonly found in invertebrates.
"There are 10 million viruses in a drop of seawater, so discovering the virus associated with a marine disease can be like looking for a needle in a haystack," said Hewson, a professor of microbiology.
"Not only is this an important discovery of a virus involved in a mass mortality of marine invertebrates, but this is also the first virus described in a sea star."
Researchers found the virus present at low levels in museum samples of sea stars collected in 1942, 1980, 1987 and 1991.
Overpopulation, pollution or mutations in the virus could have contributed to its sudden surge to epidemic proportions, the study found.
Densovirus has also turned up in water filters from public aquariums, sea urchins and brittle stars.
More research is needed to find out what triggers outbreaks, said co-author Drew Harvell, a professor of ecology and evolutionary biology.
"It's the experiment of the century for marine ecologists," said Harvell.
"It is happening at such a large scale to the most important predators of the tidal and sub-tidal zones. Their disappearance is an experiment in ecological upheaval the likes of which we've never seen."
The study was funded by the National Science Foundation (NSF) and Cornell University's David R. Atkinson Center for a Sustainable Future.
