Scientists recently discovered that massive populations of starfish have been dying along the Western Coast of the United States due to a mysterious disease that causes them to tear themselves apart. The creatures’ arms begin to twist and then literally crawl away from their body, often causing their insides to spill out. According to a report by PBS News, most starfish die within 24 hours of contracting the disease, and scientists are unsure of how to help.
These gruesome self-inflicted deaths were first noticed last year in just one species, the sunflower starfish, but since then the disease has spread to 12 species. Known as sea star wasting syndrome, the disease is characterized by white lesions on the arms of the starfish, and seems to affect the sunflower starfish and purple sea star more often than most.
‘The two species affected most are Pisaster ochraceus (purple sea star or ochre starfish) and Pycnopodia helianthoides (sunflower sea star)
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, and along the coast of California. The mortality rate is estimated at 95 per cent, and has also been documented along the East Coast when a smaller outbreak killed a number of sea stars last year.
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 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.
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 many scientists believe that an exotic pathogen is responsible for the deaths, a few have also speculated that ocean acidification or even climate change could be to blame. Either way, no one is sure what is causing the disease. Scientists are currently using various methods to better understand the problem and potential solutions. They have also appealed to citizens tp report any sightings of dead starfish and their exact location on social media sites using the hashtag #SickStarfish.