Tidbit -- an Atlantic blacktip shark at the Virginia Aquarium & Marine Science Center -- was found through DNA testing to have carried a pup that contained no genetic material from a male, the Journal of Fish Biology said.

The testing was conducted after Tidbit died in May 2007.The pup died in utero along with its mother.

Tidbit's pregnancy is the second documented case of a virgin birth, or "parthenogenesis," wrote Demian Chapman, a shark scientist with the Institute for Ocean Conservation Science at the State University of New York at Stony Brook.

Chapman documented the first virgin shark birth in a hammerhead at Henry Doorly Zoo in Omaha, Neb., in May.

"I'm sure this happens in the wild, but haven't been able to prove it yet," Chapman told the Los Angeles Times.

Some scientists have suggested virgin births may be a last-ditch way for severely depleted shark populations to reproduce if their numbers fall so low that males cannot find females, the Times said.

Chapman is writing a book on sharks' often brutal and sometimes deadly sex acts.

"It's taken us a long time to figure out that a female doesn't need a male," Chapman told the Times. "You couldn't blame them for reproducing asexually because the sex is often quite violent."