TOLDEO BLADE (Ohio) 13 March 06 Mates are optional: Toledo Zoo lizards, snakes reproduce without males (Jenni Laidman)
One can say a couple things about virgin birth: It's not common. It's not easy to explain. And it's not out of the question.
R. Andrew Odum, herpetology curator at the Toledo Zoo, held a thumb-size egg in front of a bright light and marveled. Inside, there was a lizard-in-the-making, a little bit bigger than the last time he looked. There was an embryo in a second egg, too, but that one didn't look as robust.
Lizard eggs are hardly an event in the zoo's herpetology department. But these eggs were special. They were made by a female lizard who hasn't been with a male in the year she's been in the Toledo Zoo.
Could it be that one of the zoo's luxurious jewel-green Chinese water dragons is reproducing like a virgin?
Almost.
Had the eggs survived the entire incubation period, there is a good chance they would have been the second virgin birth reported in lizards. The embryos died earlier this month.
Mr. Odum's search of the scientific literature revealed one other report of a captive lizard that reproduced without the help of a male.
"I believe they're probably the only ones to have come to light so far,'' said David Chiszar, a professor at the University of Colorado at Boulder.
Mr. Chiszar has a particular interest in these virgin births. He was one of the co-authors of a 1997 paper in the journal, Herpetological Natural History, about a surprising series of virgin births in four different snake species. Mr. Odum was another of the co-authors, reporting a virgin birth in an Aruba Island rattlesnake at the Toledo Zoo.
Scientists don't call these events virgin births. The correct term is facultative parthenogenesis, and it refers to a birth without the help of a male in a species that usually reproduces sexually.
The fact that these species normally produce sexually is an important distinction, because among reptiles and amphibians, there are the few oddball types that only reproduce asexually. In fact, one of them, a form of blue-spotted salamander, lives in northwest Ohio. This species is all female. She produces eggs with double the genetic material of a normal egg, meaning she need not wait for sperm to provide her offspring with a full complement of genes.
But facultative parthenogenesis takes place in females not known to play such tricks. And usually, it comes as a surprise.
Take the story of the Sri Lankan pit viper at the Toledo Zoo. It hadn't seen a male for years. Then one day a keeper moves the pit viper cage only to be pelted by a baby viper falling from atop the mesh cover on the viper tank.
Pit vipers are poisonous. Since pit vipers are viviparous - meaning the babies are born live - there were no eggs to tip off the keepers that it was time to be on the lookout for baby snakes. It's unlikely the keeper was in any danger, since the baby's cute little fangs were probably too small to break skin. But still, what if the little viper had slithered away and grown a bit before its keeper encounter?
"The day that occurred, we initiated a new policy here that any enclosure with a venomous viviparous species of snake has to have a containment level good enough to contain a baby, even though it hasn't seen a male,'' Mr. Odum said.
The zoo also saw virgin birth in an Aruba Island rattlesnake that hadn't seen a male since it was just a few inches long.
The specific mechanics of these virgin births isn't known, nor can anyone say whether this happens in the wild, nor can one do more than speculate as to why the virgin births occur.
Scientists look to the turkey for clues as to what may be going on in these snakes and lizards. Yes, believe it or not, turkeys can have virgin births too. If you remember that birds and reptiles share some common ancestor, it might not be as weird as it sounds.
Toledo Zoo lizards, snakes reproduce without males