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La Jolla’s Birch Aquarium eagerly awaits seadragon babies after mom transfers nearly 100 eggs to male mate

A male seadragon at Birch Aquarium is carrying nearly 100 eggs on its tail.
(Birch Aquarium)

Video: The rarely seen occurrence is a ‘learning experience’ that may help scientists foster breeding of the marine creatures.

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Much like the arrival of a human baby, the expected arrival of baby seadragons at La Jolla’s Birch Aquarium is cause for frequent check-ins, bated breath and excitement.

For the caregivers at Birch Aquarium, the thrilling but tense time started Jan. 9 when a female weedy seadragon released nearly 100 eggs to her male partner, which will carry them for the next four to six weeks. The aquarium’s hope is to raise the babies into adults.

Birch Aquarium associate curator Leslee Matsushige said she was “celebrating in my soul” when the egg transfer happened.

“We’re elated to be able to witness this at the aquarium,” said Jenn Nero Moffatt, senior director of animal care, science and conservation. “It’s extremely rare for seadragons to breed in captivity, so this is a monumental milestone for all of our staff.”

The closest that Birch — at UC San Diego’s Scripps Institution of Oceanography — had come to a successful egg transfer before this was in 2020, when five eggs were released and two of them hatched. But that transfer took place behind the scenes. This is the first time a seadragon has laid eggs on the public side of the aquarium.

“We have been working with seadragons since 1996,” Nero Moffatt said. “Since then, we have learned so much about caring for these creatures and invested a lot in our breeding program. From the lighting to the rock work, everything has been strategically designed with breeding seadragons in mind.”

Birch opened its Seadragons & Seahorses enclosure in 2019, and it features one of the world’s largest seadragon habitats.

Like seahorses, seadragon males — not females — are responsible for carrying the eggs.

Seadragon egg transfer has been documented only once in the wild and happens in captivity only a few times a year around the world.

“This is the first time we have seen an egg transfer with that many” at Birch, Matsushige said. “It’s huge for us and a success story for us.

“Every time there is an egg transfer or babies hatch, that provides more information that we can share. ... It provides information that shows what is working or what we need to change to help foster breeding in the future.”

An egg transfer is quick but occurs only after the seadragons participate in an elaborate courtship “dance.”

Matsushige said she suspected an egg transfer may be imminent but didn’t want to get her hopes up. In the weeks before, Matsushige said, she observed the seadragons’ courting rituals in the enclosure.

“They do this sort of dance with each other — they swim side by side and turn their tails out as if they were a mirror of each other,” she said. “Then they started going through this egg transfer dance, which is a little different — they swim upward and their tails cross and the female releases her eggs that theoretically are going to stick to both sides of the male’s tail.”

A male seadragon carries eggs transferred from a female at Birch Aquarium.
(Birch Aquarium)

In this case, the female weedy seadragon produced around 100 eggs and released them to her receptive male partner. Once that happens, the male fertilizes the eggs and they stick to his tail for the remainder of their gestation.

The male’s tail skin forms cups around each of the eggs so they don’t fall off, Matsushige said. Ideally they will hatch from his tail and emerge as three-quarter-inch seadragons. That process takes about five days.

“That’s what we like to see happen,” Matsushige said.

In watching the transfer process, Birch scientists noticed that the area of the male seadragon that receives the eggs turns fluorescent under blue light, “which we never knew previously,” Matsushige said.

The area where they are released from the female also fluoresces. “We haven’t studied this much, but I wonder if that is so they can see each other better or help them line up the egg transfer,” Matsushige said. “It’s really interesting.”

“It’s extremely rare for seadragons to breed in captivity, so this is a monumental milestone for all of our staff.”

— Jenn Nero Moffatt, Birch Aquarium

The next step is helping the eggs develop so as many as possible can hatch, she said. Only a small percentage of the eggs are likely to hatch, which is why so many are laid.

“There are no guarantees ... so we are cautious at every stage,” Matsushige said.

Because the seadragons typically are found only in the grassy and kelp-filled waters of southern Australia, where it is currently summer, the water temperature in their enclosure will be gradually increased to mimic the conditions in which the eggs would develop and hatch naturally.

“Everything that happens is a learning experience,” Matsushige said. “We monitor the day these egg transfers take place, the time of year, the conditions, to see if there could be any kind of trend. This is all informational.”

The ultimate goal, she said, is to have successful egg transfers and hatching more frequently.

“If we can get better at this and this can happen again and more consistently, that would be ideal,” Matsushige said. “We want this to happen on a regular basis. We need to be able to raise them in captivity because there could be a time that the numbers would decline [and] we could raise them and release them into the wild. So we need to know how to do that before there is a problem.”

With a maximum length of 18 inches, weedy and leafy seadragons tend to have a 10- to 12-year life span.

“We build exhibits for our breeding program to get better and better,” Matsushige said, “This [egg transfer] confirms what is possible.”

The seadragons are on view at Birch Aquarium at 2300 Expedition Way. The male seadragon carrying the eggs is often in the back of the enclosure. To learn more, visit aquarium.ucsd.edu. ◆