81 Percent Died But They Are Evolving and Coming Back

81% of the population of sea stars died after being struck by wasting disease. Now they are fighting back by changing their genes.


Just five years after a wasting disease swept California starfish populations, killing many of the creatures, scientists have discovered a microevolution in one species of sea star that helped it survive.

The microevolution shows how the sea stars rapidly responded to the onslaught of wasting disease with a genetic shift, according to a UC Merced study published late June in Proceedings of the National Academy of Sciences.

And it gave scientists a rare opportunity to study and document how a species might change in a short period of time.

Lauren Schiebelhut, the lead author of the study, was a graduate student at UC Merced in 2012, when she started collecting DNA samples from ochre sea stars, or Pisaster ochraceus, as part of a project on their genetic structure that also examined how juvenile ochre sea stars move around in the open ocean before returning to normal habitats, she said.

About a year later, 81 percent of the population was dead — taken out by sea star wasting disease, which turns the normally rigid starfish into gooey blobs, according to a news release from UC Merced. It was one of the largest mass mortality events recorded in a keystone marine species, according to the study. […]

Researchers sampled adult starfish who survived the disease, as well as juvenile sea stars who returned from the open ocean to their normal habitat during the height of the disease.

Scientists were looking for a “parallel shift,” meaning that they were looking for a similar change between all original adults and surviving adults, as well as between original adults and the returning juveniles, or recruits.

“We were able to rule out that it was just random genetic change and it was most likely natural selection because we saw the same shift in the adults and the recruits,” she said.

Full article can be read on San Luis Obispo’s website.

Fascinating, isn’t it? The sea stars won’t stop surprising you, learn about 10 Sea Star fun facts!