Seeing stars, sperm and millions of spawn after a Valentine’s Day rendezvous

On Valentine’s Day, Melissa Torres hung red tinsel hearts around a shallow pool at her workplace, the Birch Aquarium at Scripps Institution of Oceanography in La Jolla, California. She and her colleagues were arranging some sort of romantic encounter, and the stakes were high. . The happy couple, a pair of sunflower starfish, belonged to a species that has almost disappeared due to climate change.

Sunflower starfish are a far cry from their smaller pink cousins ​​you might know from Finding Nemo and SpongeBob SquarePants. They have up to 24 arms and can grow to a diameter of more than one meter. They are also voracious hunters, preying on sea urchins that live among the 100-foot-tall algae stalks that make up the kelp forests of the Pacific Northwest.

“In a perfect world without climate change, they would keep the ecology of the kelp forests in perfect ecological balance,” Ms Torres said. But in 2013 a mass of warm water 1,600 kilometers wide nicknamed the Blob formed in the northern Pacific Ocean. As a result of the heat, a strange wasting condition began to spread among the sunflower starfish population. Since then a an estimated 90 percent of all sunflower starfish have perished. In California and Oregon they have been declared functionally extinct.

Without starfish to keep sea urchin populations in check, the sea urchins eat too much of the giant algae in the kelp forests. It is a big problem, Ms. Torres said, because the algae “not only provide homes and food for animals, but also food and carbon storage for people.”

As of 2019, the Birch Aquarium is part of a broad network of aquariums and research centers focused on sunflower starfish conservation, beginning with efforts to breed healthy, genetically diverse starfish in captivity. At this stage of the project, Ms Torres and her team wanted to see if they could fertilize starfish eggs with both fresh and frozen sperm.

When starfish reproduce, it’s an impersonal affair: They release clouds of eggs and sperm into the water. Ms Torres injected a male and a female with an enzyme that caused them to release eggs and sperm, and then she and her colleagues waited – two hours for the male and four hours for the female.

Once both animals were successfully produced, “we were jumping and screaming and hugging each other and panicking,” she said. The team collected the yield from the starfish and then used it to fertilize the eggs.

In addition to the fresh sperm, the team repeated the procedure with frozen sperm from the same male that had been stored at the Frozen Zoo, a cryogenic facility at the San Diego Zoo. The team experimented with semen samples stored at both –112 and –320 degrees Fahrenheit; both tests, as well as the fresh sperm, were found to be able to fertilize the fresh eggs.

The experiments resulted in millions of fertilized eggs, which the team distributed to the Birch Aquarium and several of its partners, including the Aquarium of the Pacific and the California Academy of Sciences.

But even with this successful fertilization project, the future of sunflower starfish is in jeopardy due to the warming climate. Still, this recent milestone provides proof-of-concept of captive breeding methods, says Doug Pace, an associate professor at California State University, Long Beach. Dr. Pace studies the ability of sunflower starfish to survive at different temperatures, and he works with researchers examining the genetic blueprints of different populations. It’s possible that this work will reveal the genes needed for “a sunflower star that can handle the challenging conditions of the future,” he said.

As of last week, the fertilized eggs at the Birch Aquarium had progressed into the larval stage of development, as evidenced by their ability to eat the algae they were fed. “You can see pink stomachs in each little larva,” Ms. Torres said. They don’t yet have arms or other recognizable features of starfish, “but they are growing.”