According to Washington Post article a team of American and Irish researchers have discovered that some female sharks can reproduce alone. Scientists say that the female hammerhead shark kept in a Nebraska zoo for three years without any contact with a male shark had given birth to a pup:
A team of American and Irish researchers have discovered that some female sharks can reproduce without having sex, the first time that scientists have found the unusual capacity in such an ancient vertebrate species.
Their report that sharks can reproduce asexually through the process known as parthenogenesis is being published online today in the British journal Biology Letters. Researchers have observed parthenogenesis 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.
