Reviving Hope: San Diego Zoo’s Breakthrough in Saving the Critically Endangered Sunflower Sea Star In a groundbreaking scientific achievement, the San Diego Zoo Wildlife Alliance has made history by hatching dozens of larvae belonging to a critically endangered sea star species. Thanks to advancements in reproductive cell cryopreservation technology, the zoo’s reproductive sciences team successfully used thawed frozen sperm to fertilize eggs of the sunflower sea star – a magnificent 24-armed starfish that once thrived along the Pacific Coast. The sunflower sea star is one of approximately 20 species that suffered immensely from a wasting syndrome linked to climate change, resulting in the loss of over 90% of its population. This magnificent species, which once roamed the Pacific coast from Baja to Alaska in numbers exceeding five billion, now faces near-extinction. Scientists estimate that only 600 million sunflower sea stars remain worldwide, and in California, they are considered “functionally extinct” by the Wildlife Alliance. The catastrophic impact of the wasting syndrome not only devastated the sea stars but also disrupted the delicate balance of the ecosystem. With the sea star population decimated, purple urchins – a prey species for sea stars – have proliferated and overgrazed vital kelp forests. This has had far-reaching consequences, including coastal erosion, loss of recreational spaces, and a significant impact on carbon sequestration. Motivated by the urgent need to recover this species, the Wildlife Alliance’s reproductive sciences team joined forces with the Sunflower Star Laboratory and Dr. Jason Hodin, senior scientist at Friday Harbor Laboratories. Their objective was to explore if cryopreservation technology could help replenish even a fraction of the dwindling sunflower sea star population. To initiate the experiment, the Wildlife Alliance’s Frozen Zoo, part of the Wildlife Biodiversity Bank, collected and preserved nearly 200 vials of sperm from four male sea stars spawned at the Birch Aquarium at the Scripps Institute of Oceanography. These preserved sperm samples were then used to fertilize eggs, resulting in a remarkable 90% success rate in successful egg development using reproductive cell cryopreservation technology. Importantly, scientists noted that the offspring from cryopreserved sperm developed similarly to those from fresh sperm. Several offspring have even reached the half-inch juvenile stage, demonstrating promising signs of survival and growth. Throughout this groundbreaking process, scientists have been careful to monitor genetic diversity. By preserving natural variances in genes, the stars have a better chance of adapting to future ecological stressors. This attention to genetic diversity provides the best possible chance for the sunflower sea stars to overcome extinction threats. The success of cryopreservation technology represents a significant step in identifying new recovery pathways to safeguard the sunflower sea stars from extinction. However, research into the factors contributing to the wasting syndrome and efforts to treat its symptoms are equally critical. Disease ecologists will continue their investigations, while quarantined aquarists at the Oregon Coast Aquarium are making progress in treating the disease’s symptoms. The revival of hope for the sunflower sea star is a testament to the power of scientific innovation and collaboration. By combining cutting-edge techniques with a deep dedication to conservation, the San Diego Zoo Wildlife Alliance and its partners are paving the way for the recovery of this extraordinary species. Let us celebrate this milestone and remain steadfast in our commitment to preserving the rich biodiversity of our oceans for generations to come.