Starfish Limbs Mysteriously Torn Apart by Unknown Disease

Starfish limbs mysteriously torn apart by unknown disease

Millions of starfish (a.k.a. sea stars) across the West Coast of America have been dying in the droves, in recent months. Reportedly, an unknown disease is currently spreading through the starfish population – a pathology that culminates in rapid infection and the loss of the creatures’ limbs, essentially, tearing them apart. Marine biologists are now fearful that the disruption to the population of starfish will have an unfortunate, knock-on impact that adversely impacts the entire marine ecosystem.

Ochre Starfish and Sunflower Seastar Adversely Affected

According to KCTS9’s EarthFix, researchers first began to take note of the disease at a place dubbed Starfish Point, located on Washington’s Olympic Peninsula. Divers are reported to have identified thousands of dying starfish in Howe Sound and Vancouver Harbour. Ultimately, the deaths have extended along much of the West Coast of the United States. Director of the US Geological Survey’s National Wildlife Health Center Johnathan Sleeman recently highlighted the two species most affected – the ochre starfish (Pisaster Ochraceus) and the sunflower seastar (Pycnopodia helianthoides).

The ochre starfish is relatively commonplace along the West Coast, from Alaska to the warmer waters off the coast of California. Adult members of the species tend to occupy mussel beds and dampened surfaces along rocky shores, but can be found at much greater depths; meanwhile, juveniles are often found within the crevices between rocks. Although most ochre starfish are purple, some are yellow, orange, or brown in color.

Sunflower seastar creatures are the largest of all the world’s starfish, possessing arm spans that reach up to one meters in length with up to 24 limbs that are lined with powerful suckers. These predatory echinoderms feed on a wide variety of invertebrates and have a geographical distribution similar to ochre starfish.

Lesion found on a starfish infected
Photo of a starfish with one missing limb. Image credit: Nathaniel Fletcher.

Ultimately, when both ochre starfish and sunflower seastars are infected by the, as yet, unknown disease, they develop white lesions along their arms. These lesions then advance along the breadth of the entire creature. Scientists have taken to observing the deaths of infected starfish and have found starfish ripping themselves apart, once the disease has spread sufficiently.

Starfish have the ability to shed their limbs as a means of defense against predation, but infected creatures remain too vulnerable and weak; they become incapable of regenerating their arms and, therefore, their innards spill forth, triggering death within a single day. The unidentified pathology – at least in the interim – has recently been termed “sea star wasting syndrome.”

The severity of the situation is becoming increasingly apparent, with entire starfish populations having been eradicated in Puget Sound and along the coast of California. The mortality is estimated to be as high as 95 percent.

Hunting for the Cause of “Sea Star Wasting Syndrome”

Scientists are currently struggling to determine the definitive cause of the alarming pathology. Speaking to Agence France-Presse, Chair of the Department of Ecology and Evolutionary Biology Pete Raimondi, based at the University of California, Santa Cruz, conjectures that the starfish are encountering infection from a parasite, a virus or bacteria that compromises their immune system. The visible damage that is seen spreading across the starfish is theorized to result from a secondary infection taking hold.

However, this phenomenon is not merely isolated to the West Coast. Similar deaths were witnessed on the East Coast, during 2013.

Drew Harvell, a marine epidemiologist from Cornell University, recently explained the predicament that researchers typically face. She indicated that studying disease outbreaks in marine organisms is more difficult than investigating the same situation in terrestrial creatures, as marine organisms are “… out of sight and out of mind.” However, Harvell and colleagues have been afforded a head-start and have been granted funding from the National Science Foundation to look into the epidemic, while Raimondi is involved in maintaining a website on sea star wasting syndrome.

Thus far, Harvell has removed some of the limbs of healthy starfish, under anesthetic, and sent them to an expert in microbial biology – Ian Hewson. Hewson will be performing DNA-sequencing and metagenomics to determine whether there are any differences in infectious agents present between healthy and unhealthy starfish specimens.

Starfish are particularly important members of marine ecosystems, since they consume barnacles, mollusks, mussels and many other small sea creatures, and are considered indicators of overall marine life. In the absence of starfish, the mussel population can experience a massive surge in numbers, thereby having a big impact on the rest of the ecosystem. In addition, sea otters and a variety of birds consume starfish.

By James Fenner

Sources:

AFP
KCTS9 EarthFix
University of California, Santa Cruz
AquaBlog

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