Unmasking the Pacific's Sea Star Killer

Researchers have identified the cause of an illness that is leaving starfish populations in shambles. The disturbing disease, which makes starfish lose their limbs and exude their own organs, is being caused by a newly discovered virus that is sweeping through invertebrates.

That's at least according to a study recently published in the journal Proceedings of the National Academy of Sciences, which profiles the virus that has caused the largest die-off of sea stars ever recorded.

Researchers first noticed the die-off in 2013, affecting at least 20 species of sea stars along the Pacific coast. Since the mass death's discovery, experts have been scrambling to reveal what is behind it.

"I was driving off the University of California, Santa Barabara campus in January and came across hundreds of sea stars that were contorted and disintegrating," co-author Kevin Lafferty, a specialist in marine diseases, said in a recent release.  "It looked like a battlefield. I've seen no sea stars since."

According to lead author Ian Hewson, a microbiologist at Cornell University, identifying the root of a disease that was so recently noticed does not come easy.

"There are 10 million viruses in a drop of seawater," he explained in a statement, "so discovering the virus associated with a marine disease can be like looking for a needle in a haystack." (Scroll to read on...)

According to the study, Hewson and his colleagues analyzed both live samples and deceased samples from the past century - collected from museum starfish and other seafloor invertebrates.

They eventually identified Sea Star Associated Densovirus (SSaDV) virus as the microbe responsible for Sea Star Wasting Disease (SSWD) - a first of its kind among sea stars.

Stunningly, the researchers found that the virus has actually been quietly circulating around the Pacific for the last 72 years - detected in preserved sea stars collected in 1942, 1980, 1987, and 1991. However, why the disease saw this sudden and disastrous boom remains to be seen.

The authors of the study suggest that the disease may have recently risen to epidemic levels because of sea star overpopulation, environmental changes, or mutation of the virus.

This research lays the groundwork for understanding how the virus kills sea stars and what triggers outbreaks. The stakes are high, according to Hewson, as the sea star is a keystone seafloor predator in the Pacific.