Sharks are capable of 'virgin birth,' study finds
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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.
The joint Northern Ireland-U.S. research, being published today in the Royal Society's peer-reviewed Biology Letter journal, analyzed the DNA of a shark born in 2001 in the Henry Doorly Zoo in Omaha, Neb.
The shark was born in a tank with three potential mothers, none of whom had had contact with a male hammerhead for at least three years.
Analysis of the baby shark's DNA found no trace of any chromosomal contribution from a male partner. Shark experts said this was the first confirmed case in a shark of parthenogenesis, which means "virgin birth."
Asexual reproduction is common in some insects, rarer in reptiles and fish, and has never been documented in mammals.
The list of animals documented as capable of the feat has grown along with the numbers being raised in captivity — but until now, sharks were not considered a likely candidate.
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, and three years would be exceptional, they agreed.
The lack of any paternal DNA in the baby shark ruled out this possibility.
"We were all very skeptical about these reports, about the possibility of a so-called virgin birth in a shark, because sharks have this unusual ability to store sperm for months if not years," said Bob Hueter, director of the Center for Shark Research at the Mote Marine Laboratory in Sarasota, Fla.
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