May 23 (Xinhuanet) -- 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 hammerhead shark swims in a large tank at the Georgia Aquarium in this 2005 file photo in Atlanta. Female sharks can fertilize their own eggs and give birth without sperm from males, according to a new study of the asexual reproduction of a hammerhead in a U.S. zoo.(Xinhua/Reuters Photo)
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
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.