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Extreme Dads at the Tennessee Aquarium
Seahorses take fatherhood to a whole new level

CHATTANOOGA, Tenn. (May 27, 2003) - Forget about those modern dads who change diapers or get up for midnight feedings. Seahorse dads take parenting to a whole new level - they actually go through pregnancy and give birth!

It may sound like science fiction (or the basis for a bad comedy), but males undergoing pregnancy is a fact of life for seahorses.

“Admittedly, it is strange and as far as we know, seahorses are the only species in which the males actually undergo pregnancy,” said Thom Demas, Tennessee Aquarium Curator of Fishes.

Demas, along with aquarists Shelly Scott and Natalie Fisher, care for the hundreds of seahorses at the Aquarium. Although they spend a great deal of time observing these mysterious sea creatures, no one really knows why it is the seahorse dads, and not the moms, who carry the children.

“There are theories,” Demas said. “But there’s not much research regarding seahorses. Many aspects of their lives remain a mystery.”

Still, recent studies have allowed researchers to learn a lot about seahorse courtship, mating and reproduction. It all begins with a slow, dance-like promenade through the sea grass. With his head bowed, the male seahorse performs an elaborate dance around the female, often wrapping his tail around her or mimicking her movements. The male often changes color, his body becoming lighter while his spine area darkens. During this mysterious mating dance, he opens his empty pouch to the female. The female then raises her head and intertwines her tail with his.

“The ritual can last up to nine hours and resembles a ballet,” Demas said. “The seahorse pair travels up the water column as the female transfers eggs to the male seahorse’s pouch on his abdomen, where he fertilizes the eggs and goes through the pregnancy.”

Each fertilized egg embeds into the lining of his pouch, where tissue grows around the eggs and supplies them with oxygen throughout the pregnancy. This tissue does not supply nutrients to the eggs; the main source of nutrition is in the egg yolk.

In many fish species, both male and female provide parental care, Demas explained. Usually this involves guarding the eggs from potential predators and fanning the eggs to make sure they get enough oxygen and stay clean, he said. Seahorses are the most extreme example of fathers providing care. They provide oxygen through a capillary network in the pouch, transfer nutrients, and control the pouch environment so that it changes during the pregnancy to become more like salt water.

The male seahorse carries the eggs for 10 to 30 days, depending on the species and water temperature. The babies, which may number more than 1,500 depending on the species, emerge as tiny replicas of the adults, ready to begin life on their own.

Most seahorse pairs are monogamous - once a male and female form a pair bond, they mate exclusively during the breeding season. Again, scientists aren’t sure why they pair bond, and monogamy is unusual in the animal word. However, some theorize that seahorse pairs that stay together get better and better at raising offspring.

“I think it’s a case of practice makes perfect,” Demas said.

Which leads to another unusual aspect of seahorse reproduction: males usually get pregnant again immediately after giving birth!

“Sometimes an egg transfer will take place with a few minutes of the male giving birth,” he said. “Sometimes they wait a little longer, but the males are almost always pregnant again within 24 hours of giving birth.”

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The Tennessee Aquarium inspires wonder and appreciation for the natural world. Admission is $14 per adult and $7.50 per child, ages 3-12. Each ticket purchased helps support Aquarium conservation programs. The IMAX® 3D Theater is next door to the Aquarium. Ticket prices are $7.75 per adult and $5.25 per child. Aquarium/IMAX combo tickets are $18 for adults and $10.50 for children. Advance tickets may be purchased online at www.tnaqua.org or by phone at 1-800-262-0695. The Aquarium, located on the banks of the Tennessee River in Chattanooga, is a non-profit organization. Open every day except Thanksgiving and Christmas, the Aquarium and IMAX are accessible to people with disabilities. Members enjoy unlimited visits and other benefits. Call 267-FISH to join.