Clever girl! Why did it take 6 years to confirm this event of parthenogenesis, even though 79% of Americans insist that certain human beings can do it?
A female hammerhead shark was mysteriously born at Omaha's Henry Doorly Zoo in December 2001, in a tank that held three adult, female hammerheads but no males.
Although the three females had been caught before they reached sexual maturity and held in captivity for more than three years, researchers initially thought one of them had stored sperm from a male shark before fertilizing an egg. But the team -- which included scientists at Nova Southeastern University in Florida, Queen's University Belfast and the Omaha zoo -- determined that the baby shark's genetic makeup perfectly matched one of the females in the tank, with no sign of a male parent.
Nova Southeastern's Guy Harvey Research Institute director Mahmood Shivji -- one of the paper's authors -- said he and his colleagues determined that a byproduct formed when sharks produce eggs, known as a sister polar body, had fused with an unfertilized egg to produce the baby shark, whose DNA had only half as much genetic variability as the mother.
"Yes, indeed this is a virgin birth," Shivji said in an interview.
Researchers have observed parthenogenesis [the ability to give birth without having sex] in certain species of birds, reptiles, amphibians and bony fishes, but the new finding suggests that vertebrates' ability to reproduce without sex evolved much earlier than scientists had thought.
Wednesday, May 23, 2007
From the San Francisco Chronicle:
Posted by Lizzie at 11:40 AM