Iguana's Rare 'Virgin Birth' Shocks Zoo Keepers

A casque-headed iguana has given birth to eight babies in northern England - without any contact with a male, via a phenomenon called parthenogenesis.

Credit: Telford Exotic Zoo

"When we confirmed the eggs were fertile without any contact with a male, our jaws hit the floor," zoo owner Scott Adams told the BBC. "For us, it's a powerful reminder that life finds a way in the most unexpected circumstances."

What is parthenogenesis? It's a type of asexual reproduction, in which females create offspring without fertilisation from male sex cells. The unfertilised eggs develop into embryos that are genetic clones of the mother. Basically, the female clones herself.

It actually predates sexual reproduction, which evolved to introduce more genetic variation. It's more common in plants or invertebrates than vertebrates - but it has been observed among fish, snakes, sharks, lizards, and even birds. What is "mind-boggling is that parthenogenesis isn't even that rare", said the Smithsonian Institution's National Museum of Natural History. It was first documented in Komodo dragons in 2006, but has since been seen in all "vertebrate lineages" except mammals.

After a baby swell shark was born in a Louisiana aquarium that houses only females flummoxed marine experts and raised the possibility that the species may not require such earthly pleasures to produce offspring, The Guardian went looking for other occurances and spoke Colin Stevenson, head of education at Crocodiles of the World, who said: "Komodos are famous for it. They can reproduce normally, but every now and again, they pop out a parthenogenetic one. The trick is to work out what kicks it off."

So what kicks it off? "In general, we think parthenogenesis is a last-ditch effort for a female to pass on its genes, so when a female is isolated from conspecific males, she is able to undergo parthenogenesis," Kevin Feldheim of Chicago's Field Museum told NPR.

"How parthenogenesis kicks in or what cues the females use to begin the process remains to be discovered."