‘Virgin' captive python gives birth despite having no male contact — a first for species

Posted at 11:59 AM, Oct 24, 2014

Scientists at the Louisville Zoo in Kentucky are trying to solve a new evolutionary mystery after a female python gave birth to several healthy babies, despite having no contact with a male for over two years.

Call it an immaculate reptilian conception.

“I’ve been privileged to see a lot of fascinating things in my career, but I would certainly say this is one of the more unusual,” said Bill McMahan, curator of ectotherms at the Louisville Zoo.

In June 2012, Thelma, a 200-pound reticulated python, laid 61 eggs without mating — a first in over 100 years of the world’s largest snake breed being held in captivity. An extensive study into the unorthodox pregnancy was published this July in the Biological Journal of the Linnean Society, the world’s oldest biological journal.

Although a facultative parthenogenesis — or virgin birth, to the layperson — in a reticulated python had never been recorded before Thelma, who’s now 11 years old, McMahan said it’s unlikely to pick up a lot of attention in the biological community.

“I suspect it will raise a few eyebrows but I don’t think it will be completely stunning only because they’ve discovered this in other species in recent years,” he said, citing the Komodo dragon as an example.

One of the healthy pythons Thelma gave birth to at the Louisville Zoo. (Photo: Louisville Zoo)

Other large snakes have also experienced the phenomenon, according to the report “New insights on facultative parthenogenesis in pythons,” which was co-authored by McMahan and seven other researchers.

The report indicates that in 1997, a Burmese python, held in isolation from male contact, gave birth to several clutches of viable eggs at the Artis Zoo in The Netherlands. However, “Zoo policy prohibited the incubation of these eggs to full term,” according to the report.

When Thelma’s eggs were discovered, employees at the Louisville Zoo were not going to let history slip by them.

“We were presented with a clutch of 61 eggs and when we went to pull the eggs they looked pristine. Normally the eggs begin to crinkle and indent after two weeks — these were fertile eggs though,” McMahan said. Eventually, several of the eggs were destroyed due to malformations, but on Sept. 12, 2012, six healthy females were hatched.

“We’re thrilled to be part of a discovery like this,” said Kyle Shepherd, media and public relations director for the Louisville Zoo.

So how do the experts explain Thelma’s mysterious pregnancy?

“In a process termed terminal fusion automixis, cells known as polar bodies behave like sperm and fuse with the egg, triggering cell division and further development,” McMahan said Thursday.

Biologists across the globe are now working to better understand this latest mystery of evolutionary theory. Perhaps the answer is as simple as Jeff Goldblum’s famous line from the 1993 film Jurassic Park.

“Life finds a way.”

Clint Davis is a writer for the E.W. Scripps National Desk. Follow him on Twitter @MrClintDavis.