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 those affected. 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 in some places, but not others. It starts with the emergence of lesions, followed by body fragmentation and death. In 2014 it was suggested that the disease is associated with a densovirus now known as the sea star-associated densovirus (SSaDV); however, sea star wasting disease is still not fully understood. Sea star wasting disease or starfish wasting syndrome is a disease of starfish and several other echinoderms that appears sporadically, causing mass mortality of those affected. 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 in some places, but not others. It starts with the emergence of lesions, followed by body fragmentation and death. In 2014 it was suggested that the disease is associated with a densovirus now known as the sea star-associated densovirus (SSaDV); however, sea star wasting disease is still not fully understood. Typically the first symptom of sea star 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 sea star loses its grip on the substrate. 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 disintegrated, 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 sea star 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. In July 2013, populations of sea stars declined rapidly on the east coast of the United States between New Jersey and Maine. There had been a great increase in sea star numbers three years earlier, though in 2013 they were dying off. No cause for the mysterious deaths was apparent. On the Pacific coast, a meltdown of sea stars was first found in ochre stars and sunflower stars in Howe Sound, British Columbia. In late August, the disease had also been found stretching from Alaska to the border of Mexico. At the beginning of September 2013, a mass die-off of sea stars was reported off the coast of British Columbia. The sea bed was littered with disintegrating sunflower stars (Pycnopodia helianthoides), their detached arms and discs. Another species also suffering mortalities was the morning sun star (Solaster dawsoni), but no cause for the deaths was apparent. If they were caused by infection or toxins, the two species might have affected each other because the diet of each includes sea stars. In spring/summer 2013, reports of sea stars experiencing wasting symptoms came from Vancouver, B.C. and from southern and central California. Observations of symptoms spread throughout California, Washington and southern Canada throughout 2013, but sea star wasting disease did not begin affecting sea stars in the intertidal zone in Oregon until spring 2014. The relatively high resolution of understanding of the pattern of disease spread came from marine scientists working along the coast, but also from citizen scientists visiting the coast and uploading their observations, of where they saw sea stars both with and without disease symptoms, to an online sea star wasting observation log database.