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Kristin Aquilino, a scientist at the University of California, Davis, knows that expectations are only disappointments in disguise. For the past decade she has led the school’s white abalone captive breeding program, which aims to bring the marine mollusk back from the brink of extinction.
Last June, he and his colleagues deported snails held in captivity at Davis, on the California coast, to the Cabrillo Marine Aquarium in Los Angeles. Others were released into laboratories and aquariums around Southern California; This was the largest white abalone spawn attempt to date. But when he tried to lure them into the air with what he called a love potion (a mixture of seawater and hydrogen peroxide), the snails vanished in their tanks, emitting occasional bubbles but no eggs or sperm. Four hours later, Dr. Aquilino canceled. (Simultaneous attempts at other sites also failed.)
Awful, he said. “There’s a lot of human effort, but there’s no way they’re showing up today.”
After fishermen consumed 99 percent of the white abalone from the wild in the 1970s, sea snails are clinging to a slimy thread. Dr. Despite the urgency of reintroducing these and other endangered aquatic snails, further reproduction of them in the lab is still a guessing game, Aquilino says.
Now, a published study Thursday in the magazine Frontiers in Marine Science provides an improved tool for determining which abalone will breed. Using noninvasive ultrasound, a decades-old medical technology, the technique could raise the hopes of successful captive breeding efforts and ultimately help restore the endangered abalone in the wild.
“If we can use this method, we can really make a big difference and strategically target animals to encourage them to spawn,” said David Witting, a fisheries biologist at the National Oceanic Atmospheric Administration who specializes in abalone recovery. not included in the study. “We’re going to take the more advantage we can get. Spawning animals is really key to the whole process of rescuing them.”
Dr. For Aquilino, the method offers a glimmer of hope.
“The first time I saw the ultrasound images of my kids, I saw my family’s future,” she said. “When I see ultrasound images of this abalone, I see the future of an entire species.”
Seven species of abalone — sea snails with colorful, domed shells — have historically called the west coast of North America home. Animals help the ecosystems in which they live by protecting kelp forests, feeding marine mammals, and improving the health of reefs.
But for most of the 20th century, divers and fishermen consumed several species of abalone. Other than white abalone, black abalone succumbed to a disease called wilting syndrome, and pinto abalone in the northern Pacific has suffered from overharvesting and habitat degradation. In the wild, abalone sucks in long-distance relationships: They need to be close together to reproduce because snails send their gametes into the water column to fertilize. By the 1990s, endangered species were so few that scientists realized they needed to intervene.
But breeding them in captivity is a big challenge. There’s no clear clue when they’re ready to reproduce. Researchers have traditionally examined snails visually by separating them from the surface they’ve been sucking on, and then looking for a slit between their sticky feet and their shells to find a protrusion under the animal’s gonad’s milky skin. Based on how large the gonad is, scientists give the animal a score: plump protrusions are more abundant than smaller ones.
“HE IS a little Josh Bouma, program director of abalone at the Restoration Fund in Washington State, heads the captive breeding program for the endangered pinto abalone.
But visual quizzes can be massively inaccurate. The gonads surround their stomach, so the score can be misleading if the snail has just eaten a large meal. Researchers can also take a more accurate tissue sample, but that would kill the snail. Using Abalone in any way – including removing it from aquarium tanks – is enough to stress them out and can kill their mood.
On the other hand, ultrasound is non-invasive.
The idea of using ultrasound in these snails first appeared in 2019. Jackson Gross, a fisheries expert at the University of California, Davis, used ultrasound in finned fish such as sturgeon to study their reproductive habits. He stumbled upon a youtube video having a veterinarian slide an ultrasound probe into the bottom of a land snail. If it worked for land snails, wouldn’t it work for sea snails like abalone as well?
Dr. Postdoctoral researcher Sara Boles, working with Gross, discovered a way to do ultrasound on abalone without removing it from their tank by holding the device up to its sticky feet. This quickly produced clear images of their swollen or drooping gonads on a laptop connected to the ultrasound probe.
In the new study, Dr. Boles and colleagues examined more than 200 abalones and scored the thickness of their gonads on a scale of 1 to 5 to determine which ones were most likely to spawn. With ultrasound images, the gonad comes into focus: the stomach appears as a dark, cone-shaped substance and the slightly lighter gonad surrounds it.
For now, these images may provide an easy way to score animals, but Dr. Gross and colleagues want to confirm whether gonad thickness is also associated with reproductive success.
Dr. Boles in his efforts to breed white abalone, Dr. He’s already used ultrasound to help Aquilino. Last spring, Dr. After visually scoring the aquilino animals, Dr. Boles brought the ultrasound to his lab.
Dr. Of the eight white abalones that Boles scored highest after ultrasound examination, five spawned; some snails with slightly lower ratings also did. The method is already helping researchers review their methods of assessing which abalone is most ready to breed.
Dr. “It’s just another way to ensure we have the best of the best,” Boles said.
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