A disease known as sea star wasting syndrome has killed many ochre sea stars while others of the same species have been unaffected, but the ones who survive have almost no genetic differences from the ones who do not. A recent study by Oregon State University showed that ochre sea stars – which are native to the Pacific Ocean – don’t possess genes resistant to the disease, making scientists uncertain that the species will be resilient enough to survive in the future.
In 2013, a wasting syndrome epidemic believed to be the most devastating marine wildlife disease event in history began. 20 species of sea stars all along the west coast were affected – the ochre sea stars declined anywhere from 50% to 94% along the Oregon Coast during the three years the epidemic lasted.
Twisted or missing arms, lesions, loss of grip on rocks, and disintegration were among the symptoms researchers noted in the study of the ochre sea stars, also known as the purple ochre. Only the ones without any symptoms present were marked as ‘healthy,’ or ‘normal looking.’
Researchers say it’s due to climate change, which has been putting an increasing level of stress on marine ecosystems.
“As a result of that stress, marine diseases have become more prevalent over the last few decades. Disease outbreaks cause changes in ecosystems’ community structure and the age distribution within species,” said Andrea Burton, who led the study. “A lot of marine taxa have suffered severe declines in population because of outbreaks.”
So why do some stay healthy while others succumb to the disease?
“Through a number of genomic techniques, we found that genomic differentiation between normal-looking and wasting sea stars was very low,” said Burton. “With little genetic variation to propel adaptation, we definitely have even more concerns regarding how this species of sea star will fare in future outbreaks.”
Burton said while the genetic resistance is weak, they were able to identify genomic regions with some degree of disease resistance that could possibly have cumulative effects on the sea star, but it needs to be researched further.
“Assessing the potential for natural population resilience is a huge piece of predicting the long-term prospects for affected species and all of the species and communities they influence,” said Burton. “Examining genomic variation in natural populations can help answer the question of whether a species has the genetic makeup to withstand diseases on its own.”
By Momoko Baker
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