Image: Boa constrictor
Warren Booth
The mother boa constrictor gave birth, twice, to a total of 22 caramel-colored females, one of which appears in this photo.
By
updated 11/3/2010 10:54:00 AM ET 2010-11-03T14:54:00

A boa constrictor mother has given "virgin birth" to 22 female offspring, all of which have no father and are half-clones of their mother, according to new research.

The discovery adds boa constrictors to the list of animals that can give fatherless birth. The list so far includes other snakes, at least three species of sharks, the Komodo dragon and some other monitor lizards, certain termites, and more.

Researchers now even think some dinosaurs may have given virgin birth, since this phenomenon has now been reported in all lineages of jawed vertebrates, except mammals, and in a number of invertebrate species.

"Only with the development and application of molecular tools have we truly begun to understand how common this form of reproduction may be," lead author Warren Booth told Discovery News.

Booth, a research associate at North Carolina State University's Department of Entomology, and his team first suspected something was up when the mother boa constrictor gave birth, twice, to a total of 22 caramel-colored females. The males housed with the female did not carry the gene for this recessive color trait.

The scientists next extracted and analyzed DNA from skins shed by the mother, the males and the caramel-colored offspring. This DNA fingerprinting, functioning like a paternity test, determined that the offspring exhibited a sex chromosomal arrangement of WW, "something never before naturally observed," Booth said.

He explained that male snakes have the sex chromosomal arrangement ZZ, while females are ZW. Numerous prior studies concluded that the WW pairing was not viable.

"Our work essentially upends decades of scientific theory on reptile reproduction," said Booth.

He and his colleagues believe the births happened as a result of what's known as automatic parthenogenesis.

"Basically, like sexual reproduction, the offspring here received one set of the mother's chromosomes when they split during the egg production process," he explained. "However, instead of combining with a sperm that would contain the complementary second set of chromosomes from the father, the egg fuses with a copy of itself, stimulating embryonic development."

The findings are published in the latest Royal Society Biology Letters.

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Gordon Schuett, whose lab at Georgia State University first described parthenogenesis in snakes, told Discovery News that he agrees with the conclusions made in the new study, "mostly because (the researchers) provide compelling molecular data."

Schuett further expressed surprise "that there was evidence of viable WW females, which is unknown in snakes and other reptiles."

The mother boa constrictor described in the latest study was not technically a virgin, since she had previously produced a litter sexually. The scientists think boa females may therefore have the ability to alternate between sexual and asexual reproduction.

"One other interesting fact about these snakes is that if the offspring can reproduce sexually, all offspring they produce will be female," Booth said. "They are genetically incapable of producing male offspring. Only by their female offspring can males be produced again."

Aside from resulting in a possible slew of females, "virgin births" could harm genetic diversity within species because what is essentially occurring is "an extreme form of inbreeding," according to Booth.

Given that such births may be common for many animals, he hopes zoos and other keepers of rare and endangered reptiles will now more carefully monitor reproductive events.

© 2012 Discovery Channel

Explainer: 10 peeks at sex in the wild

  • Image: scroll fragment
    Jerome Maison  /  AP file / Warner Independent Pictures

    Emperor penguins endure some the harshest conditions on the planet — the Antarctic winter — to satisfy their primal urge for sex. The annual ritual begins with a days-long, up to 75-mile slog to their inshore breeding grounds. Once there, an elaborate courtship of calls and poses reunites old mates and enables young lovers to form lasting bonds.

    Copulation itself occurs under the cover of the dark of the polar night. Then the true sign of their devotion begins: Males huddle together to incubate the eggs as the females waddle back out to sea to feast, fattening up to provide for their newly hatched young. Once she returns, males depart in the first of a tradeoff that may, eventually, allow for healthy offspring.

    Click on the "Next" label for nine more peeps at sex in the wild.

    - John Roach, msnbc.com contributor

  • Captive pandas require help to get it on

    Image: Pandas
    Wichai Taprieu  /  AP file

    In the wild, biologists say pandas get it on without too much of a hitch. But since the wild population in China's mountain forests hovers around just 1,600, there's a push to boost the panda population in zoos around the world. And that's where the problems lie. Many pandas lack interest in their arranged mates and some inexperienced males who give it the old college try fail to engage the proper body part. As an aid, some zoo keepers attempt to arouse the bears and teach them appropriate technique with specially made DVDs, a.k.a. panda porn. When that fails — and it often does — artificial insemination is considered a last resort. These tricks combined with a better understanding of what makes the panda libido tick are beginning to pay off. The captive population has boomed in recent years.

  • Male macaques groom for sex

    Image: Japanese Macaque monkeys
    Shuji Kajiyama  /  AP

    Male macaques groom females in exchange for sex, according to a study that examined the market underpinnings of monkey sex. According to the research, based on 20-months of observation in an Indonesian nature reserve, a female is three times more likely to mate with a male if he grooms her first. Supply and demand also comes into play: Males spend more time grooming when competition for female attention is greater. Scientists refer to this practice as a biological market.

  • Male antelopes play hard to get

    Image: Antelopes
    Jakob Bro-Jorgensen / Zoological Society of London

    For highly-desired male topi antelopes in Africa, the frenzied six-week-long mating season is exhausting. Any given female is receptive for about a day, thus she wants to mate as many times as possible, especially with the fittest males. This creates intense competition for high quality antelope sperm, allowing those that possess it to be picky. A study of the phenomenon found the choosy males deliberately select the least mated females and fend off aggressive females they've already mated with. The aggressive female in the center of this image is attacking the male on the left as another female eyes the scene.

  • Sumatran rhinos tussle before they tango

    Image: Newborn rhino
    Tom Uhlman  /  AP

    Mating for the typically solitary and territorial Sumatran rhinoceros is a drawn-out affair. Studies of the critically endangered species in captivity show that when a female becomes receptive to a male's approach, she'll exhibit increased urine spraying, tail raising and swinging, and vocalizations. Foreplay includes head and genital butting, which can be a bit too much when a female isn't quite ready to tango with a young and aggressive male. But when the tussle is successful, a male will mount, often riding his mate for up to an hour. The image here shows the results of a successful mating at the Cincinnati Zoo. Such captive breeding efforts are a silver lining for conservationists hoping to keep the Sumatran rhino alive — just 300 are thought to remain in the wild.

  • Burliest walrus bulls get the harem

    Image: Walrus
    Liz Labunski  /  AP

    With a cacophony of clicks, clacks, whistles, and bellows, male walruses swim around the chilly Arctic waters vying for the attention of ice-bound females. Males will also fight off other males that get too close, sending the loser packing. Once the fussing and fighting is done, female harems surround the burliest males in the water for an underwater romp. Though scientists know little about what actually happens under the cover of the waves, they do know walruses are endowed with the mammal world's largest penis bone, called a baculum, which extends up to 30 inches.

  • Dolphin mating is brief, but bountiful

    Image: drainage channel
    Noaa  /  NOAA

    For playful dolphins, mating seems just like another carefree and pleasurable way to pass away the day. Along with some typical male posturing for access to females, there's plenty of chasing, rubbing, nuzzling and stroking that constitutes as foreplay. The belly-to-belly copulation act itself lasts less than a minute, though is often repeated several times over the course of an hour.

  • Virgin female spiders risk all for a big mate

    Image: archaeological site in Masada

    For some male spiders, sex is the ultimate sacrifice: females eat them as part of the reproductive ritual. But among the East African blood-gorging jumping spider Evarcah culicivora, shown here, males possess the coital-infused cannibalistic urge. Nevertheless, female virgins opt to be deflowered by bigger males before settling in with a small guy for the long haul. Scientists suspect females gamble with their fate once in hopes of producing larger, fitter offspring, but decide not to double down after the flirtation with danger.

  • Sappy sex for beetles of all sizes

    Kensuke Okada

    As this picture shows, Japanese sap beetles come in big, medium, and small sizes. Generally, in the beetle world, mating success is only bestowed on males with the biggest bodies because they can beat out the competition with brute force. Big sap beetles successfully employ this strategy, but when they do, the medium guys take to the air with their extra long wings and survey for sites where big males are absent. But the little guys have the biggest testicles. This allows them to hang with the big guys and sneak sex behind their backs. Since the little beetles have such big testes, they produce more competitive sperm, upping their chances at siring offspring when they get a shot.

  • Cycads have 'hot' plant sex

    Irene Terry  /  Univ. of Utah

    Hot sex has ancient roots. The males in a group of plants called cycads, which have been around for at least 250 million years, get all hot and bothered as a means to compel pollen-covered insects deep in their cones to flee forth and find a female to pollinate, according to scientists. The plants begin the process by emitting a fragrance that lures little insects called thrips into their cones. After a few hours of the thrips feasting and rolling around in there, the cycads heat up as much as 25 degrees Fahrenheit, which turns their sweet smelling fragrance into a stench. The thrips flee, some landing on benign-smelling female cycads and thus completing the pollination cycle.

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