Five years ago millions of starfish were wiped out by a mysterious virus from North America’s coasts. Now scientists have announced a remarkable reversal. According to a new study this species has evolved genetic resistance to the virus who shot it. The scientists showed how after the worst period of the epidemic, there was a 74-fold increase in the number of juveniles surviving among ochre stars, one of the species hardest hit by the sea star wasting disease.
Researchers describe the epidemic’s outbreak as «one of the largest marine mass mortality events on record», but how the virus killed so many starfishes is still unknown. According to scientist the virus could probably have proliferated because of climate change impacts. The epidemic is noticed since 2013, over 80% of ochre stars died. The episode was even more dangerous because of the role that starfishes have in ecosystems, in which they are a keystone of intertidal areas along the west coast.
In 2013, when the epidemic started to be really worrying, the Vancouver Aquarium biologist Jeff Marliave told a Seattle radio that «The sick ones tend to just fall apart in front of your eyes; an arm will actually break off and crawl away».
Now scientists compared data from starfishes’ DNA before and after the epidemic and they found that the new exemplars share a gene resistant to the virus: the virus itself provokes a process of natural selection.
A researcher from the Smithsonian Institution, called Chris Mah, said: «When you’ve removed a whole bunch of them, you’ve shifted the whole genetic diversity of that population». «In other words, to put it in human terms, if you wiped out a huge chunk of the human species, – Mah explained – you would change the genetic makeup of humans».
However the lead author of this new paper, Lauren Schiebelhut showed concern for «marine disease, extreme environmental events, and the frequency of those». «If we have too many extreme events in a row, – Schiebelhut said – maybe that becomes more challenging for species to respond to».