A mysterious disease is killing off the West Coast's enormous sunflower sea star, so researchers have launched an ambitious effort to breed this species in captivity.

Transcript

A MARTINEZ, HOST:

The sunflower sea star can be as big as a manhole cover. It could also have up to 24 armed. Now, the species used to be common off the west coast of the United States. I stress used to be because in recent years, it's nearly disappeared, the victim of a deadly wasting disease. NPR's Nell Greenfieldboyce went to an island off the coast of Washington to see how researchers are trying to save it.

NELL GREENFIELDBOYCE, BYLINE: Jason Hodin hauls up a rope that's hanging off a dock into the water. At the end is a square, Tupperware container, the kind you might use for a sandwich. This one has holes cut into the sides that are covered with a fine mesh to let water flow through. Hodin pulls off the lid. And we peer inside. There's some crushed shells and some tiny, reddish-orange dots.

JASON HODIN: Like that guy right there. See that little dot right there in front of my finger? That's a juvenile sea star. He's about a month old.

GREENFIELDBOYCE: It's the size of a poppy seed. Baby sunflower sea stars like this one are what Hodin and his colleagues are figuring out how to raise here on San Juan Island in the Pacific Northwest at the University of Washington's Friday Harbor Labs. In the wild, sunflower sea stars are being wiped out. For example, Hodin says, in California...

HODIN: Sunflower stars are more than 95% gone. Some people think that they're entirely extinct in the wild down there. I've heard scattered reports of people maybe seeing a few.

GREENFIELDBOYCE: The culprit is a mysterious wasting disease. No one knows what causes it. Since 2013, it's been hitting a bunch of sea star species hard on both the West and the East Coast. Hodin says the sick sea stars are horrible to behold.

HODIN: They really do kind of, like, dissolve into a pile of goo.

GREENFIELDBOYCE: And sunflower sea stars seem to be the most affected. So in 2019, the Nature Conservancy approached Hodin about setting up a program to breed this species in captivity with a goal of someday reintroducing it into locations where it's disappeared. He and his colleagues first took some sunflower sea stars from the wild. About 30 of these giants now live at the lab in burbling outdoor tanks. Researchers like Fleur Anteau recognized them as individuals.

FLEUR ANTEAU: This here's Deep Blue, and she's our biggest.

GREENFIELDBOYCE: A lot of their names are linked to their colors. Like Prince has arms with tips that are purple. These sea stars can be orange, pink, green. The colors are so bright, they almost glow like the creatures are lit from within.

ANTEAU: So some of them, when, you know, I open the cage, will start moving their arms to the surface, like Olga here. And some of them are a little shier.

GREENFIELDBOYCE: Even the shy ones suddenly come to life as she tucks tasty mussels under their arms. They hunch over the prey so they can swallow it whole.

ANTEAU: When food comes, then you really see the predator come out.

GREENFIELDBOYCE: Sunflower sea stars are predators, voracious ones. They normally crawl along the sea floor and gobble up sea urchins, keeping their populations in check and helping to protect kelp forests. This lab has figured out how to get sperm and eggs from the wild caught adults and grow up their offspring in the lab. The oldest they've produced are nearly a year and a half. They're about three inches across.

HODIN: We're assuming that by next year, they might be reproductive. Based on ones that we've seen in the field, the smaller ones that we know are reproductively mature.

GREENFIELDBOYCE: Hodin's lab is working to produce hundreds of young sunflower sea stars like these. He says, these could first be tested in local waters, where their parents came from, to see how well they fare in the wild. Then someday, maybe they could go into places where sea star populations have vanished. But the danger may still be out there.

DREW HARVELL: I would say at the outset that it's critical to understand more about what's killing them before trying to put them back.

GREENFIELDBOYCE: Drew Harvell is a research scientist at Friday Harbor Labs and professor emeritus at Cornell University. She thinks the cause could be an infectious agent. Other scientists blame warming ocean waters or other environmental changes.

HARVELL: It is extremely controversial. There is not agreement.

GREENFIELDBOYCE: She's starting new lab experiments this month to test the idea that it's infectious. Extracts from six sea stars will be injected into seemingly healthy ones. She'll be using sunflower sea stars since they're so susceptible. Meanwhile, at Hodin's lab, he's constantly on the lookout for any signs that his beloved animals are falling ill. I watch him use a pair of tweezers to tenderly feed a tiny mussel to one of the young ones. It curls its arm around the treat.

HODIN: They're our foster kids. And we're responsible for them. We take a lot of care in trying to make sure that they stay alive.

GREENFIELDBOYCE: He says he even dreams about them. The night before, he dreamed of being surrounded by water in a house-sized version of one of their tanks.

Nell Greenfieldboyce, NPR News. Transcript provided by NPR, Copyright NPR.

Tags: sea stars  wasting disease