Female Shark Gets Pregnant on Her Own, No Male Required

By Eliza Strickland | October 10, 2008 4:41 pm

blacktip sharkA female blacktip shark in a Virginia aquarium got pregnant despite the fact that no male blacktip sharks shared her tank in her eight years of residency, researchers say. This is the second documented case of asexual reproduction, or parthenogenesis, among sharks; the first example of a shark “virgin birth” occurred with a hammerhead shark in a Nebraska zoo. The new findings suggest that the previous event wasn’t a marine miracle. “This first case was no fluke,” Demian Chapman, a shark scientist and lead author of the second study, said in a statement. “It is quite possible that this is something female sharks of many species can do on occasion” [AP].

Now scientists are debating whether asexual reproduction is a backup method for female sharks that can’t find a mate, or whether the pregnancy was a developmental aberration that occurs from time to time. Chapman argues for the first camp: “The reason this has happened in captivity isn’t because there’s a change in their reproductive biology,” he explains. “It is more likely to happen if female sharks aren’t having enough dates,” he says. “These females did it because they were in captivity and ovulating” [Science News].

But others say that since the shark didn’t produce a normal litter of four to six pups, the pregnancy could have been an anomaly. “The fact that only one shark embryo was formed may suggest that this is more a case of an egg developmental aberration rather than a physiological response to the lack of a mate,” said [shark expert Robert] Hueter [National Geographic News].

The pregnancy came to light in a mournful way. The shark, named Tidbit, died when she was tranquilized for a routine trip to the vet, and a subsequent autopsy revealed that she was carrying one shark pup that was nearly ready to be born. A genetic test revealed that the pup contained no DNA from a male. Chapman explains that during egg production, a female shark produces four cells. Only one of these becomes the egg. Another of the four is called “the sister polar body,” which is a close genetic match to the egg. During parthenogenesis, according to Chapman, “the sister polar body fuses with the egg and injects its chromosomes into it. Therefore, it acts like a sperm and triggers the development of an embryo,” he said [Discovery News].

The finding was written up in the Journal of Fish Biology [subscription required], and researchers say they hope to answer some of the remaining questions about the process soon; they’re currently investigating another reported case of parthenogenesis in a white spotted bamboo shark in Chicago. While the researchers are excited to learn more about the shark’s asexual trick, they caution that the ability shouldn’t be counted on to save shark populations, which are plummeting around the globe. Parthenogenesis reduces genetic diversity, and the resultant offspring may have more risk of genetic defects, Chapman says. “This is not the great white hope for the shark population…. This is not a solution to overfishing,” he says [Science News].

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Image: Matthew D. Potenski

CATEGORIZED UNDER: Living World
  • Trocisp

    Jesus Shark.

    Need I say more?

  • http://thetechrecruiter.com kyle Locke

    Thanks. Its what I was searchin for.

  • http://onlinedating.8baiduo.com Julianna Guill

    Nice, I think it could be interesting to add some more entries following this one, and probably it’s not only me having this opinion. Cheers!

  • http://clubneko.net Nick

    I think you mean “Mary Shark” but whatever. The baby would be the Jesus Shark. :)

    And may I add a LOL for the gentleman with the “great white hope for the shark population” pun.

  • http://www.squidoo.com/how-to-get-pregnant-safe dipesh14

    It makes me uncomfortable when someone just reaches out and pats my belly..Then I have some people touch my belly and it seems totally natural. So for me It depends on who it is. I’ve had 1 person ask if she may touch my belly in 34 weeks of pregnancy and it made my day that she would have enough respect to ask…

  • http://autolitterbox.liveautomatic.com Catgenie 120

    Pretty neat story! Obviously, regardless of circumstance, evolution will find a way!

  • http://www.squidoo.com/how-to-get-pregnant-and-getting-pregnant holistic pregnancy

    Don’t think this is a pregnancy miracle at all. Probably these sharks are just storing sperm for years like other animals can do. The no male DNA present in the pups thing is a little puzzling, though.

  • http://www.compressionstockings.com/medi.php Support Socks

    Very interesting story! I was unaware that sharks could reproduce asexually. I am curious to read about more research done on this topic. Also, I wonder how the pups will turn out without any male DNA. Very exciting news!

  • http://bestpregnant.net Pregnancy Information

    The information you write is very useful. Keep writing and I’ll come back another time.

    Thank you

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