Last year, ecologists were surprised by the sudden disappearance of starfish, also known as the sea star, along the West Coast of North America. The starfish were dying en masse, but the cause of the death was not known. Scientists called the plague “sea star wasting syndrome” (SSWD). It began with the detachment of the marine species’ arms, and made them look wasted, thin, dried out and inflated.

starfish

Starfish killer named SSaDV

Scientists partially blamed global warming. But a new study published in the Proceedings of the National Academy of Sciences has revealed that the plague was actually caused by a virus. Led by Ian Hewson, researchers went through several possibilities such as protozoa, fungi and bacteria. But finally they discovered that a virus called Sea Star Associated Densovirus (SSaDV) was the main culprit. The virus killed almost 100% of the starfish it infected.

Researchers said that the transmission of the virus might be facilitated by climate change. They were able to isolate the virus in the laboratory and infect a healthy starfish with it. But how does the virus spread? Scientists said that it spreads through water when the sea stars feed or gather together. However, it’s not a new virus. The SSaDV was detected in starfish and other species as early as 1942. The environmental impact of the virus is still unclear.

It was a difficult job

Scientists started their experiment by accumulating sunflower starfish, and supplied them with filtered, UV-treated seawater. Then they compared the tissues of non-infected sunflowers with the infected ones. They found the presence of the genome of a new virus. Researchers put the sunflower starfish in different tanks, each supplied with filtered, UV-treated seawater.

Next, they took tissues of infected starfish and injected the tissue sample to the sunflower sea stars. Finally, they found out the virus responsible for the mass killing. Finding the cause of the starfish death was a challenging job considering the fact that there could be thousands of different types of viruses in a single drop of water.