for National Geographic News
A hammerhead shark born in a Nebraska zoo in 2001 was the result of a so-called virgin birth, new DNA evidence shows.
The finding marks the first confirmed case of a female shark fertilizing her own eggs and giving birth without sperm from a male, a process known as parthenogenesis.
"We were very surprised to find parthenogenesis in a shark," said Mahmood Shivji, director of the Guy Harvey Research Institute at Florida's Nova Southeastern University.
"It has been found in other vertebrates, birds, snakes, reptiles, even some bony fishes, but it has never been described in sharks and rays or in mammals," he added.
Shivji is the co-author of a study detailing the findings that was published yesterday in the journal Biology Letters.
The baby bonnethead shark, a type of hammerhead, was born at the Henry Doorly Zoo in Omaha, Nebraska.
It was killed within hours of its birth by a stingray in the same tank.
Scientists were able to match the baby's DNA with one of three potential mothers in the tank.
But none of these females had had any contact with a male for more than three years.
Scientists at first believed the birth had come about as a result of a female shark's well-documented ability to store sperm for months.
"But that assumed the mother had actually copulated in the wild when she was a baby," before being taken to the tank in 1998, Shivji said. "That was not likely."
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