Boa constrictor has ‘virgin birth’

Thursday, November 4, 2010

WASHINGTON - Scientists have discovered that female boa constrictors can produce offspring without mating - a rare phenomenon among vertebrates.

Researchers at the North Carolina State University the finding shows that the babies produced from this asexual reproduction have attributes previously believed to be impossible.

Large litters of all-female babies produced by the “super mom” boa constrictor show absolutely no male influence - no genetic fingerprint that a male was involved in the reproductive process. All the female babies also retained their mother’s rare recessive color mutation.

This is the first time asexual reproduction, known as parthenogenesis, has been attributed to boa constrictors, said lead author Dr Warren Booth, an NC State postdoctoral researcher in entomology.

He said the results may require scientists to re-examine reptile reproduction, especially among more primitive snake species like boa constrictors.

Normally, snake sex chromosomes are different from those in mammals - female boa constrictors have a Z and a W chromosome, while male boas have two Z chromosomes.

Yet in the study, all the female babies had two W chromosomes - something that was thought to be impossible.

According to Booth, such WW females could be produced only through complex manipulation in lab settings, and even then only in fish and amphibians.

Adding to the oddity is the fact that within two years, the same boa mother produced not one, but two different snake broods of all-female WW-chromosome babies, all having the mother’s rare colour mutation.

Incidents of virgin births have often been attributed to absence of males. But the mother’s two virgin birth litters were produced while she was being housed with male snakes, and she had previously given birth to litters after mating with a male.

Booth, who doubts that the rare births were caused by environmental changes, said asexual reproduction in snakes could be more common than people think.

“Reproducing both ways could be an evolutionary ‘get-out-of-jail-free card’ for snakes,” he said.

A reptile keeper and snake breeder, Booth now owns one of the young females from the study.

When the all-female snake babies reach sexual maturity in a few years, Booth wants to examine whether they will eventually mate with a male, or reproduce asexually, or do both as their mother did.

But because of their WW chromosomes, any offspring they produce will be female, he said.

The study is published online in Biology Letters, a Royal Society journal. (ANI)

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