A giant manta ray, measuring more than 1.8m (6ft) wide, has become the first of its kind to be born in captivity, scientists have claimed.

The baby, a female, was born on Saturday in a huge fish tank at the Okinawa Churaumi Aquarium, Japan.

Footage of the birth shows the youngster unfolding like a carpet from her mother before spreading her fins and swimming around.

News of the new manta has generated huge interest in Japan and its birth, which was recorded by the aquarium, was broadcast nationwide by TV channel NHK on Sunday.

Officials say the birth will provide an invaluable opportunity for researchers to study the little-known species.

Aquarium spokesman, Minoru Toda, said: "My heart was heavy at first because I thought it had been still-born, but we were so relieved when she finally started swimming around. Now we have to make sure the baby grows in good health."

Giant manta rays, the world's largest species of ray, can grow up to 7.6m (25ft) in diameter and feed on plankton and small fish throughout the world's tropical oceans.

Scientists believe they have evolved from other bottom-feeding species and have adapted to become filter feeders in the open ocean, allowing them to grow much bigger.

The mantas are most commonly black on their backs and white underneath. Their distinctive diamond shape and pectoral fins allow them to glide through the water.

Keepers at the aquarium have admitted they will now have to rely on intuition to care for the new baby, as knowledge surrounding its development is so limited.

The mother manta, which was brought to the aquarium in 1998 after being caught in a fishing net about 1,000 miles southwest of Tokyo, was pregnant for 374 days. She was successfully mated with a male manta at the aquarium on June 8 2006.

Previously, the successful breeding of the species in captivity has proved difficult due to a combination of factors.

Paul Hale, curator of the London Aquarium, said: "Improved water quality, capturing techniques and bigger aquariums have all combined to create a better chance of breeding success.

"Capturing mantas while keeping their stress levels to a minimum is very tricky. It's now done by first using nets and then hoisting the manta into a large holding vessel on a ship.

"Other factors have been the improved technology of water filtration systems to create a more comfortable environment, as well as the building of aquariums which are actually big enough to keep mantas in. As far as I'm aware this is a world first."

Noriyasu Suzuki, an official at the Izu-Mito Sea Paradise commercial aqua zoo in western Japan, also believes that this is the first birth in captivity. "I've never heard of any other case before," he said. "Aquariums that raise manta rays are rare to begin with because they get so big."