Could dolphin be the result of a scientific success?

SeaWorld's newest baby dolphin could be a scientific breakthrough.
The Atlantic bottlenose is the first creature in a zoological park successfully bred for a specific sex, SeaWorld officials announced yesterday.

SeaWorld scientists bred this female dolphin by using sperm processed by a Colorado company with patented technology in sex-selection techniques for animals. Animal reproduction experts with Busch Entertainment Corp., the owner of SeaWorld, accomplished the feat by using sperm processed to maximize the chances of getting a female dolphin.

If they and other scientists can repeat the outcome, their sex-selection methods may help thousands of zoological institutions worldwide to better manage the male-to-female ratio of their animal collections. The technology could also aid efforts to save threatened and endangered species.

"We want to be leaders in the responsible management of species" in zoological parks such as zoos, aquariums and theme parks, said Justine O'Brien, a member of the SeaWorld team that produced the female dolphin.

In October 2004, O'Brien and fellow SeaWorld scientist Todd Robeck artificially inseminated a bottlenose dolphin named Sandy. They used sperm processed by a special machine that selected cells with the female-producing X chromosome.

The cells were sorted by XY Inc. of Fort Collins, Colo., which specializes in sex-selection techniques for animals. The company has a patented technology that it developed with Colorado State University and the U.S. Department of Agriculture.

On Oct. 6, Sandy delivered the baby, which weighed 40 pounds and measured nearly 4 feet long. The calf has not been named.

SeaWorld did not immediately examine the baby to determine its sex because that would have disrupted the crucial mother-calf bonding process, said curator Bill Hoffman. After two months of waiting, veterinarians were able to visually confirm that the calf is a female, he said.

During the experiment, which involved artificially inseminating three female dolphins, the scientists determined that it was optimal to give Sandy 350 million sperm cells. The other two dolphins received different doses of sperm and did not become pregnant.

The biologists also had to figure out how to keep dolphin sperm alive in liquid form and how to freeze it for transport and later use.

The Busch and SeaWorld experts will try to duplicate the sex-selection process next spring, O'Brien said.

Being able to choose an offspring's sex is significant, he said. By balancing the male-to-female ratio of their animal collections, zoological parks can produce social groupings similar to those in the wild.

For instance, breeding among wild horses requires just one dominant stallion for several females. To duplicate this composition in a zoo setting, scientists would breed more females than males.
Dolphins, elephants and several other species that reproduce naturally in captivity at zoological parks tend to produce more male babies, said Barbara Durrant, head of reproductive physiology at the Conservation and Research for Endangered Species center in San Diego.

The leading theory for this sex disparity is that high-nutrition diets provided by zoological institutions trigger more male offspring, she said. For example, laboratory experiments have found that mice fed high-quality diets produce more male than female babies.