Friday, May 4, 2012

Sharks Virgin Birth

In 2001 a Hammerhead shark was born at the Henry Doorly Zoo in Nebraska with three potential mothers in the same tank. All had been in captivity for at least three years. The birth of the shark baffled scientists for years. Some scientists thought one of them might have mated before being captured and stored the sperm for fertilization. Some scientist believed that sharks might be able toreproduce asexually through a rare method known as parthenogenesis (a direct development without the need of a sperm). Many were skeptical but in late 2007 scientists confirmed this through DNA testing. After they determined which of the three females was the mother they subtracted the mother’s contribution from the offspring and in this particular case after the DNA was subtracted there was nothing left. The researchers were forced to conclude that the pup had no father, making this he first documented case of asexual reproduction of a shark.

Interesting Fact: In 2008 Scientists confirmed a second virgin birth of a shark at the Virginia Aquarium & Marine Science Center. A 5-foot, 94-pound Atlantic blacktip shark died of stress-related complications related to her unknown pregnancy. During the necropsy a 10-inch shark pup was found surprising aquarium officials. DNA testing on the embryonic pup proved that the pup carried no genetic material from a male.