Sea star wasting disease

Sea star wasting disease or starfish wasting syndrome is a disease of starfish and several other echinoderms that appears sporadically, causing mass mortality of affected starfish. There are around 40 different species of sea stars that have been affected by this disease. The disease seems to be associated with raised water temperatures. It starts with the emergence of lesions, followed by body fragmentation and death. In 2014 it was shown that the disease is associated with a densovirus now known as the sea star-associated densovirus (SSaDV).

Typically the first symptom of starfish wasting disease is white lesions that appear on the surface of the starfish and spread rapidly, followed by decay of tissue surrounding the lesions. Next the animal becomes limp as the water vascular system fails and it is no longer able to maintain its internal hydrostatic balance. The body structure begins to break down, signs of stretching appear between the arms which may twist and fall off, and the animal dies. The arms may continue to crawl around for a while after being shed. Progression of these events can be rapid, leading to death within a few days.

A deflated appearance can precede other morphological signs of the disease. All of these symptoms are also associated with ordinary attributes of unhealthy stars and can arise when an individual is stranded too high in the intertidal zone (for example) and simply desiccates. "True" wasting disease will be present in individuals that are found in suitable habitat, often in the midst of other individuals that might also be affected.

The final result is a white, mushy blob, which no longer seems to be a sea star.

The 1972 plague was the first notable case of Sea Star Wasting Disease. Scientists noticed a rapidly declining population of common starfish (Asterias rubens) occurring off the east coast of the United States. The symptoms were that the starfish became limp and lost limbs until finally melting into a white mucus like paste.

In 1978 large numbers of the predatory starfish Heliaster kubiniji succumbed to a wasting disease in the Gulf of California. At the time it was suspected that high water temperatures were a causal factor. This starfish became locally extinct in some parts of the gulf and some populations had still not recovered by the year 2000. Because this starfish is a top-level predator, its disappearance had profound effects on the ecosystem. In the Channel Islands off the coast of California, ten species of starfish were recorded as being affected as well as three species of sea urchins, two brittle stars and a sea cucumber, all of which experienced large population declines.

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