Role reversal: Male sea horses carry babies

You wanted to know

"Why do sea horses transfer the eggs from the female to the male?" asked a camper from Lake County Forest Preserve's Fishing Camp at Libertyville's Independence Grove forest preserve.

Pipefish, sea dragons and sea horses are the daddies of the animal world, all offshoots of the Syngnathidae family. Females from these species pass off their eggs to the males. These dads tuck the eggs into their brood pouches, fertilize them and nurture them until they are ready for birth.

For the pipefish, it means dad takes on about a dozen eggs and delivers newborns in about 10 days. He might snack on a few by absorbing some eggs while they're in his pouch, and both pipefish moms and dads might eat their offspring.

Male sea dragons have a brood patch on their tales. The moms deposit about 250 pink eggs on the brood patch. The dads, after holding onto their babies for a nine-week pregnancy, only deliver 5 percent of the offspring.

In a complete reversal, sea horse fathers act like mothers when it comes to birth, and sea horse babies, called fry, are mini-adults, said Tse-Lynn Loh, postdoctoral research associate at Chicago's Shedd Aquarium.

"What we would think of as sea horse babies are actually miniature versions of adult sea horses, independent from birth and receive no further parental care," Loh said. "Newborns of most species measure between seven and 12 millimeters, and the number of young released averages about 100 to 200 for most species, but can be as low as five for the smaller species or as high as 1,500."

It's still not entirely known why males carry the babies.

"Sex role reversals, such as seen in sea horses, are very rare in the animal kingdom and scientists are still researching the reasons why this happens in sea horses and their relatives," Loh said.

She explained that sea horse moms and dads give their offspring immunities. By comparison, only moms have that ability among humans.

Sea horses live in the sea grasses and coral reefs. Not only do they have a surprising appearance - a mini horse-head attached to a shrimplike body - they have skin instead of scales, their eyes see independently and they are not great swimmers. More research needs to be conducted to better understand these creatures and how they are adapting to environmental and human threats.

Loh is working on sea horse distribution maps in Thailand to help estimate population trends through Shedd Aquarium partner Project Seahorse, and she co-founded a marine conservation program with a citizen sea horse monitoring project in Singapore.

"I like investigating human impacts on natural ecosystems, so studying sea horses and how the wildlife trade affects natural populations was a good fit," she said.

"A fisherman in Cambodia asked if I was a feminist, because I work on sea horses and male sea horses get pregnant. I do support equal opportunities for all regardless of gender, but that's not why I started working on sea horses."

Loh explained her fascination with the horse-headed sea creature.

"I started working on coral reefs during my honors thesis at university in Singapore while studying animal biology and have loved marine biology ever since. I continued with a Ph.D. in marine biology in the U.S., researching how angelfishes and parrotfishes affect sponges and corals on the reef," she said.

Loh's typical day at the office may be spent in the waters of a Thai beach with ancient temples spiking above the village landscape. Her field work has provided rare opportunities.

"One of the coolest finds was seeing seven sea horses hitching a ride on a sea urchin while diving off Pattaya, Thailand," she said. "A few months before I had surveyed the Andaman coast of Thailand with a colleague for two months and found eight sea horses. That was our entire field season there, on one sea urchin."

Teens can learn more about sea horses or any other species at the Shedd Aquarium in the teen learning lab at no charge. There are even more educational opportunities for teens interested in marine study. See www.sheddaquarium.org/Learning-Experiences/Teen-Programs for more information.

Check it out

Cook Memorial Public Library District in Libertyville suggests these titles on sea horses and sea dragons. Books from the following list can be found at Cook Park Library in Libertyville, Aspen Drive Library in Vernon Hills, or on the bookmobile that supports the entire district.

• "The Life Cycle of a Sea Horse" by Bobbie Kalman

• "The Sea Dragon" by Miriam Gross

• "Project Seahorse" by Pamela Turner

• "Sea Horses and Sea Dragons" by Mary Jo Rhodes and David Hall

• "Sea Horse: The Shyest Fish in the Sea" by Chris Butterworth

• "Seahorse Fry" by Ruth Owen

• "Seahorses, Sea Dragons, and Pipefish" by Twig C. George