Mysterious plague causes starfish to rip off their arms - and scientists don't know why



The arms of infected starfish begin to twist and then ‘crawl’ away from the creature’s body, until they tear off and the animal’s insides spill out

Divers and scientists first noticed the horrific disease off the coast of Washington state but there have been sightings elsewhere too



Mystery disease prevents the creatures from growing new arms like healthy starfish and they die within approximately 24 hours

A mysterious disease is causing starfish to tear themselves to pieces.



The arms of infected starfish begin to twist and then ‘crawl’ away from the creature’s body, until they tear off and the animal’s insides spill out.



Divers and scientists first noticed the horrific disease off the coast of Washington state, but sightings of dead starfish have been reported as far north as Alaska and in southern California.

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A mysterious disease is causing starfish to tear themselves to pieces. The arms of infected starfish begin to twist and then 'crawl' away from the creature's body, until they tear off (pictured)

The disease prevents the creatures from growing new arms like healthy starfish and they die within approximately 24 hours, according to a report by PBS News.



Starfish have been dying by the millions in recent months along the U.S. west coast, worrying biologists who say the sea creatures are key to the marine ecosystem.



Scientists first started noticing the mass deaths in one species – the sunflower starfish - in June 2013, but the disease, which has been dubbed sea star wasting syndrome - has now spread to 12 species.



Different types of starfish are affected, from wild ones along the coast to those in captivity, according to Jonathan Sleeman, director of the US Geological Survey's National Wildlife Health Centre.





Scientists first started noticing the mass deaths in one species - the sunflower starfish - in June 2013, but the disease, which has been dubbed sea star wasting syndrome - has now spread to 12 species. A healthy sunflower starfish is pictured

'The two species affected most are Pisaster ochraceus (purple sea star or ochre starfish) and Pycnopodia helianthoides (sunflower sea star),' he wrote in a statement in December.

The sunflower starfish is considered among the largest of all the species and can span more than a metre in diameter.



The most commonly observed symptoms of the suspected disease are white lesions on the arms of the starfish.

The lesions spread rapidly, resulting in the loss of the arm. The infection consumes the creature's entire body and tears itself to pieces.



Entire populations have been wiped out in Puget Sound off the coast of Washington state, in the Salish Sea off Canada's British Columbia as well as along the coast of California. The mortality rate is estimated at 95 per cent.



Divers and scientists first noticed the horrific disease off the coast of Washington state in the Pugnet Sound, but sightings of dead starfish have been reported as far north as Alaska and in southern California

Ben Miner, a biology professor at Western Washington University, collected healthy starfish and those showing symptoms of the disease to study in his laboratory At first, the starfish twist their arms into knots and then legions form on their skin, before the arm tears away from the body (pictured)

WHAT DOES THE 'DISEASE' DO?

The most commonly observed symptoms of the suspected disease are white lesions on the arms of the starfish.



The lesions spread rapidly, resulting in the loss of the arm.



The arms of infected starfish begin to twist and then ‘crawl’ away from the creature’s body.



They tear off but appear to keep crawling for a short time.



As the animal loses more arms its insides spill out.



The creatures typically dies within 24 hours of the symptoms appearing and they rip themselves apart.



One diver said the scene under the waves near the coastline of Seattle was reminiscent of something from a horror film as there are ‘bodies everywhere’.

One diver said the scene under the waves was reminiscent of something from a horror film as there are ‘bodies everywhere’.



Scientists who have spent decades studying the local ecosystem have yet to identify the cause.



'What we currently think is likely happening is that there is a pathogen, like a parasite or a virus or a bacteria, that is infecting the sea stars and that compromises in some way their immune system,' Pete Raimondi, chair of the department of ecology and evolutionary biology, at the University of California, Santa Cruz, told AFP.



The creatures are thought to become more susceptible to bacteria which is ‘causing a secondary infection that causes most of the damages that you see.'



Ben Miner, a biology professor at Western Washington University collected healthy starfish and those showing symptoms of the disease to study in his laboratory.



He told PBS News that he came across arms and piles of deteriorating sea stars off the coast of North Seattle.



At first, the starfish twist their arms into knots and then lesions form on their skin. Their arms then crawl away from their own body until they tear off and the animal’s insides spill out, he explained.

‘They start ripping themselves apart,’ he said.

The animals destroy themselves within 24 hours of the symptoms appearing. Here is all that was left of one animal that tore itself apart

The 2013 phenomenon has not been observed solely along the West Coast as a smaller outbreak also killed East Coast sea stars last year, leading a few scientists to speculate that ocean acidification or even climate change could be to blame, while most think an exotic pathogen is attacking the animals.



Previous cases were believed to be associated with warmer waters - starfish have sensitive skin and prefer cooler water - but most scientists do not believe this to be the case this time around.

Biologists are worried about the decline of the sea creatures, which are key to the marine ecosystem. A stock image of the sunflower starfish is pictured

When the die-offs happened previously, the geographic span of the infections was much smaller and far fewer sea stars were affected.

In 1983, an epidemic nearly wiped out the Pisaster ochraceus from tidal pools along the southern coast of California.

Another, smaller die-off in 1997 may have been caused by warmer waters in an El Nino year, scientists said.

'Sea stars are important because 'they play a key role in this ecosystem on the West Coast,' Dr Raimondi said.



Starfish eat mussels, barnacles, snails, molluscs and other smaller sea life, so their health is considered a measure of marine life on the whole in a given area.



Dr Sleeman said that when starfish decline in number, 'the mussel population has the potential to dramatically increase, which could significantly alter the rocky intertidal zone.'



While starfish make up an important component of the base of the ocean food chain and are considered a top predator, they are in turn eaten by other starfish, shorebirds, gulls, and sometimes sea otters.



In an effort to find out what is causing the mass deaths, scientists are collecting reports from the public, taking specimens to the lab for analysis and doing genetic sequencing to find out whether a toxin or an infection may be to blame.

