Giraffes at the Safari Park
November 27, 2023

News Release

San Diego Zoo Wildlife Alliance 
Public Relations 


Breakthrough for Critically Endangered Sea Star Recovery: Cryogenically Preserved Specimens Produce Offspring

SAN DIEGO (Nov. 27, 2023) – When a mysterious illness called “sea star wasting syndrome” decimated 95% of the sunflower sea star population, and some 20 other sea star species along the Pacific Coast from Baja to Alaska in 2013, scientists rallied to understand the factors that caused such a massive wasting event. Now as part of the greater recovery initiative, in a scientific first, dozens of baby sunflower sea stars were hatched and are thriving thanks to a breakthrough in reproductive cell cryopreservation technology.  

For the first time, researchers with the San Diego Zoo Wildlife Alliance’s reproductive sciences team, in collaboration with Sunflower Star Laboratory and Dr. Jason Hodin, senior scientist at Friday Harbor Laboratories, successfully froze sunflower sea star sperm, thawed it and fertilized eggs that resulted in larvae developing with up to 90% success.        

“We were excited to take on a new challenge for our lab and with the advice from Dr. Mary Hagedorn at Smithsonian Institution, and her years of experience cryopreserving coral sperm, we were able to achieve immediate success,” said Nicole Ravida, laboratory manager for San Diego Zoo Wildlife Alliance. 

“The successful reproduction of dozens of sunflower sea stars through cryopreservation is an exciting step forward for sea star recovery efforts,” said Ravida. “Cryopreservation is one method reproductive scientists can contribute to the preservation of gene diversity in sunflower sea star populations.” 

Sunflower sea stars, which are ​​under review for the federal Endangered Species Act as a threatened species, were among starfish species hardest hit by the wasting syndrome, where over a matter of hours, stars disintegrate into nothing, said Ashley Kidd, Sunflower Star Lab Conservation Aquaculture project manager. Scientists from a variety of institutions coming together to bring their own area of expertise to the recovery of the species is essential, she said. 

“Partnerships are key to conservation efforts to recover the sunflower sea star, and the San Diego Zoo Wildlife Alliance’s Reproductive Sciences team is honored to provide the cryopreservation skills and tools to help advance cryopreservation techniques for this species,” Ravida said. 

Hodin at Friday Harbor Laboratories agreed that the results are promising.  

"As far as we can tell, the offspring resulting from fertilization with cryopreserved sperm developed the same as those coming from fresh sperm,” Hodin said. “We now have several that have made it to the half-inch juvenile stage and are still going strong." 

SDZWA also recently collaborated with Birch Aquarium at Scripps Institution of Oceanography to collect and cryopreserve 197 vials of sperm from four males spawned at the aquarium for storage in the SDZWA Wildlife Biodiversity Bank Frozen Zoo™. 

“The SDZWA's reproductive and cryopreservation team have given sunflower star recovery a valuable tool for conservation that will enhance what culture ​​work that has already been developed,” Kidd said. “To further support restoration of the species, we believe the ability to preserve unique genetic traits from the remaining population that spans thousands of miles will give them the best chance at adapting to future stressors by maintaining genetic diversity for potential recovery programs.” 

Kidd said successful reproduction through cryopreservation is logistically easier to manage broodstock and ensure diverse pairing for genetic diversity.  

The sunflower sea star can have up to two dozen arms spanning in excess of 3 feet. They naturally occurred along ​​the entire Pacific coast of North America, but, from 2013-2018, 95% of the population died from a wasting event and are considered functionally extinct in California, Oregon and coastal Washington, where only a handful of sea stars have been observed over the past few years, Kidd said. It is estimated that 5.6 billion sunflower stars perished. 

“The catastrophic wasting wasn’t only bad news for the sea stars, it upset the critical balance of the ecosystem, allowing purple urchins typically hunted by sea stars to ​​over-graze the aquatic kelp forests,” Kidd said.  "Kelp forests are highly productive ecosystems vital to supporting diverse marine populations; they provide coastal protection from wave erosion, provide places to recreate and are essential to carbon sequestration.” 

Kidd said global experts in population genetics, husbandry, early life history and behavior ecology are continuing to work together to identify recovery pathways. Disease ecologists continue their research into the variables behind wasting disease – warming ocean temperatures, bacteria, a virus, or all of the above. Quarantine aquarists at Oregon Coast Aquarium are nonetheless making headway in treating wasting symptoms with sea stars in human care, she said.  

“This advancement in freezing reproductive cells to potentially safeguard against the extinction of sunflower sea stars has energized the team for future work with endangered marine invertebrates,” Ravida said. 


About San Diego Zoo Wildlife Alliance  
San Diego Zoo Wildlife Alliance, a nonprofit conservation leader, inspires passion for nature and collaboration for a healthier world. The Alliance supports innovative conservation science through global partnerships. Through wildlife care, science expertise and collaboration, more than 44 endangered species have been reintroduced to native habitats. Annually, the Alliance reaches over 1 billion people, in person at the San Diego Zoo and San Diego Zoo Safari Park, and virtually in 150 countries through media channels including San Diego Zoo Wildlife Explorers television program in children’s hospitals in 13 countries. Wildlife Allies – members, donors, guests – make success possible.

All visual assets provided by SDZWA are intended solely for use by journalistic news media agencies only. For commercial usage, please submit a request to SDZWA's Licensing Department.

Link includes:

  • Photo and video of sea star program