Seahorse Fathers Take Reins in Childbirth

Stentor Danielson
National Geographic News
June 14, 2002

It's true that male seahorses never play catch with their children or help them with their homework. But they do outdo human dads on one count: Male seahorses undergo pregnancy and give birth to their sons and daughters.

The trait is unique in these strange and fascinating fish that inhabit tropical and temperate coastal waters worldwide.

Seahorses, which range from less than an inch to a foot (one to 30 centimeters) in length, have evolved a series of unusual adaptations—a prehensile tail for clinging to underwater vegetation, a tubelike mouth for sucking in tiny crustaceans, and protective bony plates in their skin. There are 32 species of seahorse, all in the genus Hippocampus.

"They're such an unusual-looking fish, people sometimes don't realize they're real fish," said Alison Scarratt, curator of fishes at the National Aquarium in Baltimore.

The aquarium is currently featuring "Seahorses: Beyond Imagination," an exhibit about seahorses, pipefish, and sea dragons that will end next year. Scarratt said it has been the most successful exhibit in the history of the Baltimore Aquarium, which opened in 1981.

Although the bony plates covering its body make the seahorse unpalatable to most other animals, its survival is under threat from human predation, especially for use in traditional medicines.

No statistical data on seahorse populations is available because relatively little research on seahorses has been done until recently, but fishers have reported a decline in the number and size of seahorses they catch, according to a network of scientists from various institutions who conduct research under a program called Project Seahorse.

Breeding seahorses in captivity is a problem, in part because the babies are so tiny it's hard to keep them alive. The marine scientists in Baltimore are working to develop effective methods that will help ensure the creature's survival.

Male Contractions

The male seahorse has a pouch on its stomach in which to carry babies—as many as 2,000 at a time. A pregnancy lasts from 10 to 25 days, depending on the species.

The reproductive process begins when a male and a female seahorse do daily pre-dawn dances, intertwining their tails and swimming together. Eventually they engage in a true courtship dance, which can last as long as eight hours. It ends with the female depositing her eggs in the male's pouch.

"Their mating ritual is quite beautiful," said Sarah Foster, a research biologist at McGill University in Montreal who is involved in Project Seahorse.

Scientists think the courtship behavior is designed to synchronize the movements of the two animals so that the male can receive the eggs when the female is ready to deposit them. The eggs are then fertilized in the dad's pouch.

Continued on Next Page >>


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