James Bruggers

@jbruggers

Zoo's discovery marks first known virgin birth for a reticulated python.

Virgin births among snakes and some other species isn't so rare after all

Reticulated pythons are the world's largest snakes.

Who needs males?

Not the world's largest snakes, and the Louisville Zoo has the reticulated python to prove it.

Zoo officials said Thursday that one of their female reticulated pythons, Thelma, gave birth to six baby pythons without the aid of a male python. She shared exhibit space only with another female python, Louise.

Go figure.

The zoo did, with the help of a University of Tulsa expert — assistant professor of biological sciences Warren Booth, who has been documenting phenomenon of virgin birth in other snakes in recent years.

While the concept of virgin birth may be well known from the Bible, through the story of Mary and Jesus, that's not science.

But it turns out that science is finding a growing number of female animals that normally reproduce sexually can also get it done without males, with an initial discovery in the 1890s involving domestic pigeons, Booth said.

"It's not a rare event," he said. "It actually appears to be very common."

Domestic chickens and turkeys, Komodo dragons, hammerhead sharks, even some song birds have demonstrated the ability to reproduce asexually, with a flurry of new discoveries in the last decade as genetic analysis has improved, he said.

But until the zoo's Thelma popped out a clutch of 61 eggs two years ago, and the Tulsa research team was able to study the genetics of the mother and its six surviving offspring, it had never been documented before in that species, said the zoo's Bill McMahan. He's curator of ectotherms, which are animals that depend external sources of body heat.

"I think this has probably occurred before, but maybe was attributed to (male) sperm storage or retention," McMahon said.

"The public probably isn't very well aware of this," said Anthony J. Lentz, chair of the Bellarmine University Department of Biology. "But it is pretty neat."

Zoo officials said that with Thelma, it worked something like this: The reproduction occurred through a process known as terminal fusion automixis, where certain cells known as polar bodies behave like sperm. They fuse with an egg and trigger cell division and development, completing what biologists call parthenogenesis.

The offspring are half clones, with genetic material only from the mother instead of a normal mix of genes from the mother and a male.

It's a "very extreme form of inbreeding," which can be a problem genetically, especially over the long term, Booth said.

Booth said the unconventional reproductive strategy could be useful, helping a species survive during a shortage of males, but the offspring would need to eventually find a mate to maintain genetic diversity.

Booth and seven researchers, including McMahan, co-authored a research paper on whole thing that was published in June in the Biological Journal of the LinneanSociety, titled "New insights on facultative parthenogensis in pythons." The paper detailed the genetic analysis that confirmed the finding.

The zoo is caring for the six young pythons, members of a species that can grow to 25 feet long and weigh 300 pounds, though they are not on exhibit, said Kyle Shepherd, zoo spokeswoman. Booth said he hopes to collaborate with the zoo again by studying them as they grow.

Shepherd said zoo officials are pleased to participate. "Anytime you can be a part of contributing to the canon of what the world knows about a certain species it's a great day (and) a great year," she said.

As for mammals ... while there's that biblical story of virgin birth, there's no scientific evidence of asexual reproduction ever among mammals in nature, though scientists have done it with mice in a lab setting, Booth said.

Mammals, including humans, are just too complicated, Booth said.

"The mother and father must contribute specific genes to create a viable offspring," he said.

Reach reporter James Bruggers at (502) 582-4645 or on Twitter at @jbruggers.