sharks fertilizing eggs

Female sharks can give "virgin birth" -- fertilizing their own eggs without sperm from males, according to research published Wednesday in the Royal Society's Biology Letter.

A sexual reproduction is common in some insect species, rarer in reptiles and fish, and has never been documented in mammals. Shark experts said this was the first comfirmed case in a shark of parthenogenesis.

The joint Northern Ireland-U.S. research in the Royal Society's peer-reviewed journal analyzed the DNA of a shark born in 2001 in the Henry Doorly Zoo in Omaha, Nebraska.

The shark was born in a tank with three potential mothers, none of whom had contact with a male hammerhead for at least three years.