Between 2012 and 2015 the starfish were wiped out by a mystery virus that effectively melted their bodies, in what has been described as one of the biggest marine mass-mortality events on record.

It’s thought possible that the culprit was a densovirus that had lain dormant until being activated by climate change.

Hardest hit were ochre starfish (Pisaster ochraceus), with 81% of their population killed, and the intertidal eco-system was expected to be seriously affected by their sudden absence.

But now scientists from the Universities of California and Rhode Island have reported that the emergence of a generation of ochre stars resistant to the virus began as early as late 2013, soon after the peak of the outbreak.

Comparing starfish DNA from before and after the epidemic, they found that today’s ochre star juveniles all possessed a gene resistant to the virus, concluding that the threat to the species’ survival had triggered a process of natural selection.

After the epidemic had peaked there was a 74-fold increase in the number of surviving ochre-star juveniles, says the report, which appears in Proceedings of the National Academy of Sciences.

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