Virus blamed in starfish die-off

The discovery could explain the deaths of millions of these sea creatures

This ochre sea star (Pisaster ochraceus) is one of at least 20 starfish species suffering from a mysterious die-off. Experts have now identified a virus as the likely culprit. Infection can transform the marine creatures into puddles of slime.

D. GORDON E. ROBERTSON/WIKIMEDIA COMMONS (CC BY-SA 3.0)

A virus may be responsible for turning starfish along the west coast of North America into puddles of slime.

Since June 2013, scientists have watched in horror as the dazzling marine creatures have experienced a startling and mysterious die-off. At least 20 species of starfish (also known as sea stars) have been affected. The epidemic has hit the Pacific coast of the United States, Canada and Mexico.

Experts now have linked the deaths to an infectious germ. It is called sea star-associated densovirus. The virus is a type of parvovirus commonly found in invertebrates. Parvo, which infects cats and dogs, is a related virus.

The newly identified virus can sicken healthy starfish. The germ is also more abundant in sick starfish than in healthy ones. Details appear in a study published November 17 in the Proceedings of the National Academy of Sciences.

The experts also have turned up the newly recognized germ in starfish preserved in alcohol since 1942. That suggests the virus has been around for decades. It is not yet clear what is causing the latest outbreak. However, the scientists said plankton, sea urchins and sand dollars could be spreading the germ. The virus also is found in marine sediments.

Power Words

epidemic  A widespread outbreak of an infectious disease that sickens many people (or other organisms) in a community at the same time.

germ  Any one-celled microorganism, such as a bacterium, fungal species or virus particle. Some germs cause disease. Others can promote the health of higher-order organisms, including birds and mammals. The health effects of most germs, however, remain unknown.

infectious  An adjective that describes a type of germ that can be transmitted to people, animals or other living things.

invertebrate   An animal lacking a backbone. About 90 percent of animal species are invertebrates.

marine   Having to do with the ocean world or environment.

plankton  A small organism that drifts or floats in the sea. Depending on the species, plankton range from microscopic sizes to organisms about the size of a flea. Some are tiny animals. Others are plantlike organisms. Although individual plankton are very small, they form massive colonies, numbering in the billions. The largest animal in the world, the blue whale, lives on plankton.

sediment  Material (such as stones and sand) deposited by water, wind or glaciers.

urchin   Small, spine-covered sea animals without eyes or limbs which are related to sand dollars and starfish.

virus  Tiny infectious particles consisting of RNA or DNA surrounded by protein. Viruses can reproduce only by injecting their genetic material into the cells of living creatures. Although scientists frequently refer to viruses as live or dead, in fact no virus is truly alive. It doesn’t eat like animals do, or make its own food the way plants do. It must hijack the cellular machinery of a living cell in order to survive.

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