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← Science Today: Mysterious Shark Birth | California Academy of Sciences

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Showing Revision 1 created 07/10/2015 by Eva D..

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  2. There were three females
    of brownbanded bamboo sharks
  3. here at the academy.
  4. And they were acquired in 2007
    from the Aquarium of the Pacific,
  5. and what happened is
    that one of those females
  6. actually produced one egg
    that started developing normally.
  7. There were no males here.
  8. And in January, 2012 that pup was born.
  9. At first we thought that this
    was a case of parthenogenesis.
  10. Parthenogenesis is known
    in popular literature as virgin birth.
  11. And what happens in parthenogenesis
    is that there's one unfertilized egg
  12. that actually starts developing normally
  13. until it becomes a pup.
  14. Parthenogenesis is actually
    really common in the natural world
  15. but when we did the genetic testing,
  16. what we did is that we compared
    the three females
  17. with that pup and we actually found
    that the pup
  18. was the most dissimilar
    organism of the three.
  19. He was so, so dissimilar
    that we couldn't even tell
  20. which of the females was the mother.
  21. We think that that genetic information
    actually came from a father.
  22. That's where the story
    gets really interesting
  23. because what we think happened
    is that the female actually stored sperm
  24. from one of the males
    of the Aquarium of the Pacific
  25. for a really long period of time.
  26. Actually sperm storage is not
    a well-known strategy
  27. but it's fairly common for insects.
  28. And in the case of vertebrates,
    it happens very often in snakes.
  29. And this is really exciting
    because what we think happened
  30. is that one female stored
    sperm for 45 months
  31. and that's the longest amount of time
  32. that we know any shark storing sperm.
  33. So those two strategies are actually
    found in solitary species
  34. in which encounters between
    males and females
  35. are actually very rare.
  36. In the case of sharks,
    there's a lot of questions
  37. about conservation when we touch
    this topic of parthenogenesis
  38. and sperm storage.
  39. And the reason behind it is that
    with dwindling shark populations,
  40. encounters between males and females
    may actually become even more rare.
  41. And in those cases, a lot of scientists
    think that parthenogenesis
  42. might become more common.
  43. If parthenogenesis becomes more common,
    you may have a population
  44. with several individuals
    but all those individuals
  45. are going to be very,
    very similar to each other.
  46. That means that genetic diversity
    is actually going to be very, very reduced.
  47. So sperm storage is actually a strategy
    that allows that maintenance
  48. of that healthy genetic diversity.
  49. That's going to help sharks
    be here on planet earth
  50. for many more years to come.
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