Female sharks give "virgin birth"

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.

Before the study, many shark experts had presumed that the Nebraska birth involved a female shark's well-documented ability to store sperm for a lengthy period of time. Doing this for six months is common, while three years would be exceptional, they agreed.

But analysis of the baby shark's DNA found no trace of any chromosomal contribution from a male partner.

In general, all sharks reproduce only sexually by a male and female mating, requiring the embryo to get DNA from both parents for full development, just like in mammals.

Xinhuanet – May 23, 2007