Virgin Birth - but it's a Shark and a Mouse

"Virgin births are possible in female sharks, according to a new study that found a captive female bonnethead shark had reproduced without having been near a male in three years." reports the ABC today.

Director of the Henry Doorly Zoo in Nebraska, Dr Lee Simmons, was surprised when one of the three female bonnetheads gave birth to a 20 centimetre long offspring. Unfortunately it died the same day after being injured by a stingray in the same exhibit. The pup was sent to the Guy Harvey Research Institute at Nova Southeastern University for analysis where it was found that it had no paternal DNA. It also had half of its mother's genetic diversity, indicating the mother gave birth through a non-sexual mode of reproduction known as automatic parthenogenesis. This involves the female creating an egg that contains 50% of the mother's genes, which was then fertilised by a tiny, genetically similar cell called a sister polar body.

While fish, insects and birds have been known to reproduce in this way, it was thought to not occur in mammals. However, today's issue of the journal Nature reports that a team led by Dr Tomohiro Kono from the Tokyo University of Agriculture have produced a fatherless mouse, which they have called Kaguya, after a mythological Japanese princess.

Lest this gives hopes to advocates of a completely lesbian lifestyle, their research only further confirms the necessity of a male partner in mammalian reproduction. Australian embryologist, Professor Patrick Tam, from the University of Sydney's Children's Medical Research Institute, says that the mouse, the only success from 28 other attempts, was only born because one of the female genes responsible for "imprinting" the DNA was first removed.

The gene H19 was deleted in the donor egg before transferring its genetic material into the recipient egg. This gene, only expressed in females, is in a general region of the genome that is important in embryonic development. The researchers reported, "The results suggest that paternal imprinting prevents parthenogenesis, ensuring that the paternal contribution is obligatory for the descendant." According to Tam this means that "males are not dispensable in the natural situation."