Archive for Wednesday, May 23, 2007

Study: Female sharks can reproduce asexually

May 23, 2007

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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 Wednesday 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 contact with a male hammerhead for at least three years.

The baby was killed within hours of its birth by a stingray in the same tank. Analysis of its 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 is derived from Greek and means "virgin birth."

Asexual reproduction is common in some insect species, 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.

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