Breakthrough in Sea Star Cryopreservation

San Diego Zoo Wildlife Alliance, Sunflower Star Laboratory, Omaha’s Henry Doorly Zoo and Aquarium, Aquarium of the Pacific, and partners continue work to save sunflower stars from extinction.

MOSS LANDING, Calif., (June 17, 2025) – In a groundbreaking effort, a team of conservation partners froze, thawed, and settled larval giant pink stars (Pisaster brevispinus) into juveniles, the first time this process has been completed with a species of sea star. This success serves as a model for utilizing frozen larvae as a conservation tool for sea star recovery, including the critically endangered sunflower sea star (Pycnopodia helianthoides).

This first-of-its-kind achievement was the result of significant collaborative efforts from numerous partner institutions. Adult giant pink stars were spawned and their gametes cross-fertilized by scientists at the Aquarium of the Pacific, resulting in thousands of viable larvae. These larvae were cryopreserved in San Diego Zoo Wildlife Alliance’s Frozen Zoo® by the organization’s reproductive sciences team, with the assistance of protocols developed by partners at Omaha’s Henry Doorly Zoo and Aquarium. The frozen larvae were transferred to conservation nonprofit Sunflower Star Laboratory, where they were thawed, grown through their larval stage, and settled into juvenile sea stars. 

The larval freezing process has since been replicated with larvae from adult sunflower stars held at the Alaska Sea Life Center, and University of Washington’s Friday Harbor Labs, with the cryopreserved larvae held at Omaha’s Henry Doorly Zoo and Aquarium.

A larval giant pink star is suspended in a water droplet emerging from a pipette. Courtesy of Patrick Webster

Cryopreservation allows for frozen larvae of these species to be held in storage for extended periods of time, affording more flexibility in creating or expanding efforts to grow sea stars under human care, and increasing the genetic diversity of individuals in the ‘biobank’, both key factors for accelerating sea star recovery efforts.

This collaboration is part of the Association of Zoos and Aquariums (AZA) SAFE Sunflower Sea Star Program, a multi-faceted program that incorporates objectives related to ex situ aquaculture, research, reintroduction/field work, and education/outreach. 

By successfully settling cryopreserved giant pink star larvae, this team laid the groundwork for similar efforts focused on the sunflower star. Sunflower stars are a critically endangered species of sea star that serves as a keystone predator in kelp forest ecosystems, and cryopreservation is a critical tool for enhancing recovery efforts for this species.

Sunflower stars help provide balance to kelp forest ecosystems by eating and scaring urchins and other native species that graze on kelp. In 2013-2014, Sea Star Wasting Syndrome, one of the largest marine disease outbreaks on record, decimated populations of sunflower stars across their former range from Alaska to Baja California, rendering the species functionally extinct in California. In their absence, urchin populations have skyrocketed, and kelp forests have declined precipitously across much of the state, in part due to the impact of urchin overgrazing.

The novel larval cryopreservation and settlement process developed by these partners will accelerate the pace of sunflower star recovery, providing hope for building kelp forest resilience in California and along the Pacific coast.

Media Contacts:
● San Diego Zoo Wildlife Alliance | Claire Sweeney, publicrelations@sdzwa.org
● Sunflower Star Laboratory | Reuven Bank, reuven@sunflowerstarlab.org
● Aquarium of the Pacific (Long Beach, CA) | Marilyn Padilla, mpadilla@lbaop.org
● Omaha’s Henry Doorly Zoo and Aquarium | Jacey Kallsen, jacey.kallsen@omahazoo.com