Pregnant male sea dragon at UCSD’s Birch Aquarium might produce bounty of babies

A male weedy sea dragon on Tuesday carries approximately 80 to 100 eggs on his tail
(Nelvin C. Cepeda/The San Diego Union-Tribune)

This is the first time the aquarium was able to coax a female sea dragon to release large numbers of eggs that were captured and put in a “brood pouch” by a male.


For the first time, UC San Diego’s Birch Aquarium has coaxed a female weedy sea dragon into transferring a large number of eggs to a male sea dragon who could give birth to a bounty of babies.

On Monday, aquarium staff discovered that one of its males is carrying about 100 bright pink eggs in the “brood pouch” on its tale. Many will become fully formed and born in four to six weeks.

It is an oddity of nature — and a scientific leap for the Birch, which is part of the Scripps Institution of Oceanography.

Scientists say that sea dragons, sea horses and pipefish are the only animals on Earth whose males get pregnant and give birth.

Birch made a tiny bit of progress cultivating them in 2020. A female sea dragon transferred five eggs to a male, resulting in two babies. But only now has the La Jolla aquarium done this broadly with female sea dragon, which are capable of producing 200 to 300 eggs.

“I was blown away and started cheering,” said Leslee Matsushige, associate curator at Birch. “We’ve been working on this for so long.

The Birch first imported sea dragons from the Dallas World Aquarium in 1996 as part of its education and conservation efforts. Getting them to reproduce has been no small trick, mostly because it is hard to replicate the environment of sea dragons, which are best known for silently flitting about in the seaweed beds and rocky reefs of southern Australia.

“We’ve gone through a lot of trial and error, learning how to keep them healthy,” Matsushige said Tuesday. “Most fish will try to reproduce if they are happy.”

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Egg transfer among sea dragons

The aquarium has done such things as fine-tune the creature’s diet, adding vitamins and probiotics and monitoring their calories.

The Birch also tinkered with lighting and rock work to get things just right.

The goal is to get the sea dragons ready for reproduction, which begins with a courtship in which the lithe fish mimic each other’s movements in a “mirror dance”.

The female then produces eggs that are released and captured by the tale of the male, where they will stay until they hatch.

Matsushige said Birch will be ready if the pregnant male produces a lot of babies.

“We would have to provide a lot of food, but we would do it,” she said. “We would make room for them. This is a good problem to have.”

The pregnant male is currently visible in the aquarium’s sea dragon habitat.

The weedy sea dragon parents swim together at the Birch Aquarium Tuesday.
The weedy sea dragon parents swim together at the Birch Aquarium Tuesday.
(Nelvin C. Cepeda/The San Diego Union-Tribune)