Scientists Are on a Mission to Save These 24-Armed, Bike-Wheel-Sized Sea Creatures

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Sunflower sea stars — voracious predators that feed on mussels and sea urchins — are succumbing to a strange wasting disease that has devastated populations of sea stars along the West Coast. (Dennis Wise/University of Washington)

Jason Hodin hauls up a rope that's hanging from a dock in the waters off San Juan Island in the Pacific Northwest. At the end is a square, sandwich-size Tupperware container, with mesh-covered holes in the sides to let water flow through. Hodin pulls off the lid and peers inside at some crushed bits of shell. He points to some reddish-orange dots.

"See that? That little dot right there in front of my finger?" Hodin says. "That's a juvenile sea star that's about a month old."

It's only the size of a poppy seed. But when this baby is all grown up, it could be as big as a manhole cover. That's because this is Pycnopodia helianthoides, aka the sunflower sea star. It's one of the biggest sea stars in the world, with an arm span that can be more than 3 feet across, and it used to be a common sight in the waters off the West Coast.

Now, though, it's critically endangered and is being driven toward extinction by a mysterious, devastating disease.

This is why Hodin and his colleagues at the University of Washington's Friday Harbor Laboratories have spent the last two years figuring out how to raise this species in captivity. It's an act of desperation born out of the hope that someday, lab-grown sunflower sea stars could be reintroduced into places where this species has disappeared.

Jason Hodin, research scientist at the University of Washington's Friday Harbor Laboratories, works in the sea star captive rearing lab. The sunflower sea star breeding program is a partnership between the university and the Nature Conservancy. (Dennis Wise/University of Washington)

This voracious predator used to prowl the waters across a nearly 2,000-mile range, from Alaska to Baja California. Their brightly colored bodies — which come in vivid shades of orange, pink, blue and green — would move along the seafloor on as many as 24 arms, gobbling up mussels and scallops and sea urchins. Their consumption of sea urchins, in particular, helped to protect vital forests of kelp, which are home to numerous marine species.


In recent years, however, populations of the sunflower sea star have declined by 80% to 100%. In California, "sunflower sea stars are more than 95% gone," Hodin says. "Some people think that they are entirely extinct in the wild down there. I've heard scattered reports of people maybe seeing a few."

This species seems particularly susceptible to a wasting disease that's hit more than 20 sea star species since 2013. Hodin says the sick sea stars are horrible to behold. "I witnessed it, and it's not pretty," he says. "They really do kind of like dissolve into a pile of goo."

In 2019, Hodin says, the Nature Conservancy approached him about the possibility of setting up a program to breed sunflower sea stars. He'd already been interested in the basic science of sea stars because of the way they are able to transform themselves from bilaterally symmetrical larvae to juveniles with five-sided symmetry. He agreed to try raising large numbers of sunflower sea stars to adulthood, even though no one had tried to do anything like this before.

Adult sunflower sea stars feed on mussels at the Friday Harbor Laboratories. Shells from earlier meals collect at the bottom of the tank. The sea star on the bottom, called Charlotte, is the mother of the lab's 1-year-old juvenile stars. (Dennis Wise/University of Washington)

"For this species in particular, there were very few published efforts to raise them at all, even through embryo or larval stages," Hodin says.

He didn't know the answer to some of the most basic questions, such as what did this species eat early on? And how fast could it grow?

"Nobody knows how to age a sea star, so you see something in the wild and you have no idea how old it is," Hodin says. "It could be 2 years old. It could be 50. It could be 100."

His team started by taking some sunflower sea stars from the wild. About 30 of these giants now live outside the lab in large, burbling tanks.

"I didn't really anticipate how exuberant their behaviors are," Hodin says. "You get to know them, and you get to know them individually. We noticed early on that we could tell them apart by their color patterns. And we gave them names."

A lot of their names are linked to their colors. Prince, for example, has arms with tips that are purple.

An arm of an adult sunflower sea star has numerous orange and white tube feet that it uses for walking, breathing and sensing. (Dennis Wise/University of Washington)

"This here's Deep Blue, and she's our biggest," researcher Fleur Anteau says as she feeds the sea stars by gently tucking mussels under their arms. "Some of them, when I open the cage, will basically really start moving their arms to the surface, like Olga here. Some of them are a little shyer."

Even the shy ones suddenly come to life once they clutch a mussel. They hunch over the prey so they can swallow it whole. "When food comes, then you really see the predator come out," Anteau notes.

Pointing to the red eye spot at the end of each arm, she adds, "They're looking at you. They don't have eyes like us, but they can see a light-and-dark kind of vision."

This lab has figured out how to get sperm and eggs from the wild-caught adults and grow up their offspring. The oldest sea stars they've produced are now nearly a year and a half, and they are about 3 inches across.

The lab only has about a dozen young sea stars that have reached this stage. But considering how little was known at the start — and the fact that they had to work out their techniques during a pandemic that restricted who could go to the lab — Hodin says he feels lucky to have gotten that many.

"We're assuming that by next year, they might be reproductive, based on ones that we've seen in the field," Hodin says. "It's good news that they can grow relatively quickly."

Left: Hodin, the research scientist who is leading the captive rearing program, prepares to view sea star larvae under a microscope. Right: Sunflower sea star larvae, born in mid-January, are seen under a microscope. The dark oval shapes are stomachs. (Dennis Wise/University of Washington)

Having learned the tricks needed to raise these sea stars, the research team's new goal is to produce up to 1,000 more young stars. The lab is full of glass pickle jars that contain larvae, and food containers that hold the poppy seed-size juveniles.

Hodin says that first, lab-grown sea stars could be put into the local waters, where their parents came from, to test how well they fare in the wild. If that goes well, it might be possible in the coming years to try to restore populations off the California coast.

But the danger of sea star wasting disease could still be out there.

"I would say at the outset that it's critical to understand more about what's killing them before trying to put them back," says Drew Harvell, a professor emeritus with Cornell University who is also a researcher at the Friday Harbor Laboratories.

Currently, she says, scientists disagree on the nature of the killer. Some blame an infectious agent, such as a virus, while others point to warming oceans or other environmental changes.

"It's extremely controversial," says Harvell, author of a book called Ocean Outbreak: Confronting the Rising Tide of Marine Disease. She believes there's a lot of evidence that sea star wasting disease is infectious.

This month, she and her colleagues are starting new lab experiments to test that idea. In a fish pathogen lab, extracts from sick sea stars will be injected into seemingly healthy ones. She'll be using sunflower sea stars since they are so susceptible.

"These are difficult experiments to get to run consistently, and so if you try to do them with a species that is somewhat resistant, sometimes just nothing happens," Harvell says.

Even if scientists never are able to figure out what causes this illness, she says, eventually it could still be worth trying some kind of reintroduction of captive-bred sea stars to the wild.

"At some point we would just have to probably go forward," Harvell says, "even though scientifically that wouldn't be the very best plan."

Hodin wishes he knew whether the sea stars his lab is raising are susceptible to the disease. He's constantly on the lookout for any signs that his beloved animals are falling ill. "We hope they don't get it obviously," he says.

He uses a pair of tweezers to tenderly feed a tiny mussel to one of the young sea stars. It curls its arm around the treat.

"Their adult-like behaviors are starting to emerge at these small sizes, and that's been really fascinating to watch," says Hodin, who adds he feels a deep attachment to all of the animals that he's raised. "I think of myself as their foster parent. I'm caring for them and trying to optimize their growth and watching them grow."


He says he even dreams about them. Just the night before, he'd dreamed of being surrounded by water in a house-size version of one of their tanks.

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