April 27, 2021
Just a few days shy of the first day of spring, scientists at Friday Harbor Laboratories on San Juan Island had reason to celebrate.
Dozens of juvenile sea stars, no bigger than a poppy seed, had successfully metamorphosed from floating larvae to mini star — the important first step toward becoming an adult. Between now and then, these sunflower sea stars, the largest sea star species in the world, will grow up to 24 arms and a colorful body the size of a serving platter.
These young animals represent the first attempt to raise sunflower sea stars in captivity. The species, once abundant from Alaska to Southern California, was nearly destroyed by a mysterious wasting disease that has affected many sea stars in the ocean, but none so catastrophic as the sunflower star. In December, the species was listed as critically endangered by the International Union for Conservation of Nature, prompting a new focus on recovery efforts — including captive breeding.
The underside of an adult sunflower sea star at UW Friday Harbor Laboratories.Dennis Wise/University of Washington
The project, a partnership between the University of Washington and The Nature Conservancy, aims to learn more about sunflower sea stars and explore eventual reintroduction to the wild, if determined to be advisable. The research team currently is raising sea stars in several phases of development, including newly born larvae, mini juveniles and fully grown adults.
“What we’re attempting to do here is to raise a new generation of sea stars in the lab,” said Jason Hodin, research scientist at Friday Harbor Labs who is leading the captive rearing efforts for the UW. “We’re hoping that our efforts can help in the process of recovery of the sunflower sea star and, ultimately, recovery of the health of ecosystems like the kelp forests that are under threat right now.”
- Sunflower sea star larvae, born in mid-January, seen under a microscope. The dark oval shapes are stomachs.
- Juvenile sunflower sea stars on the bottom and along the side of a container in the lab. These roughly one-year-old sea stars were the first group to be born in captivity at UW Friday Harbor Laboratories
- The underside of adult sunflower sea stars, feeding on mussels. More than two dozen adult sunflower stars make up a breeding colony at the University of Washington’s Friday Harbor Laboratories on San Juan Island, where researchers are rearing sea stars in captivity in collaboration with The Nature Conservancy.
Left to right: Sunflower sea star larvae, about a month old, seen under a microscope; one-year-old juvenile sea stars; adult sea stars (click on each image to enlarge). Dennis Wise and Kiyomi Taguchi/University of Washington.
Kelp forests are already facing increased pressure from marine heat wave events and, combined with exploding sea urchin populations, these threats contribute to an uncertain future for the kelp forest ecosystems that provide important habitat for thousands of marine animals while supporting coastal economies.
Before the wasting disease took hold in 2013, sunflower sea stars were common from Baja California, Mexico, to Alaska and were important predators, especially for purple sea urchins. Now, with 90% of the sunflower sea star population gone and other factors, sea urchins have multiplied and are feeding on, and decimating, kelp forests.
Research assistant Fleur Anteau, front, checks on year-old juvenile sunflower sea stars in the UW lab as research scientist Jason Hodin, back, examines month-old sea star larvae under a microscope.Dennis Wise/University of Washington
“The loss of this important predator has left an explosion of purple urchins unchecked and has contributed to devastated kelp forests along the West Coast, making this ecosystem more vulnerable and less resilient to the stressors it’s already facing,” said Norah Eddy, associate director of The Nature Conservancy’s California Oceans Program. Eddy and senior scientist Walter Heady are working with the UW team to advance the sea star captive breeding program.
The UW research team first collected about 30 healthy adult sea stars from among the last-known wild colonies in the Salish Sea. Each adult star has a unique color pattern and was named, affectionately, by researchers based on its physical characteristics. For example, “Clooney” is named for his silver hairlike features, “Fanta” is bright orange, and “Prince” boasts purple tips on each arm.
Every two days the adult stars devour wild mussels and clams collected near San Juan Island, and the researchers are confident the animals know when feeding time is based on their behavior and activity levels.
Adult sunflower sea stars feeding on mussels at UW Friday Harbor Laboratories. The stars suck out and ingest the soft tissues of mussels, then discard the shells, which collect at the bottom of the tank.Dennis Wise/University of Washington
About a year ago, Hodin and collaborators successfully bred several adult stars, and they soon discovered the challenge of raising the early juvenile stages — a feat never previously accomplished for this species, and for very few types of sea stars at all. After a challenging year of trial and error, they saw 14 juveniles cross the one-year mark, proving the likelihood they will make it to adulthood. The stars are expected to be fully grown adults after two or three years, but even that isn’t certain for a species that has never before been grown in captivity and is hard observe over time in the wild.
A one-year-old juvenile sunflower sea star crawling across the bottom of a container in the lab, shown with a human hand underneath, for scale.Kiyomi Taguchi/University of Washington
“Unless an organism lays down signs of yearly growth, like tree rings, it’s hard to know how old it is,” Hodin said. “For sunflower stars, we’ll only know that through raising them in the lab or going out year after year to a population and trying to measure the same stars.”
This past January, the researchers applied what they had learned from the first round and successfully produced tens of thousands of new larvae. The tiny critters, living in mason jars and seen clearly only under a microscope, are being raised in varying water temperatures, in part to test whether the species can survive warmer ocean temperatures expected under climate change.
The first few larvae to undergo the dramatic metamorphosis process into juvenile form — essentially the mini version of an adult — were raised at warmer temperatures, which is a positive sign for the sunflower sea star to recover in the midst of a warming world, Hodin said.
“These are not typical ocean temperatures around here, and yet their apparent success indicates that the larvae at least are robust to temperature increases expected with climate change,” Hodin explained.
Sunflower sea star larvae, born in mid-January, seen under a microscope at about a month old. The dark oval is a stomach. Polarized light reveals a glowing, branch-like shape, which is the start of the sea star’s adult skeleton.Dennis Wise/University of Washington
The first step of this project is to learn as much about the life cycle and biology of the sunflower sea star, which is only a step away from extinction in the wild. There are no specific plans for reintroduction yet, and any future effort would involve more discussion among scientists and permission from wildlife agencies, Hodin said.
“If we can raise them in the lab, it might be possible to reintroduce them to the wild in areas where they’ve disappeared,” he said. “In the meantime, we’re learning more every day from these first-ever lab-raised sunflower stars.”
This research is funded by The Nature Conservancy.
For more information, contact Hodin at larvador@uw.edu and Heady at wheady@tnc.org. If you’re interested in supporting the UW’s sunflower sea star captive rearing efforts, visit the “Stars for the Sea” giving page.
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