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

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Showing Revision 3 created 07/10/2015 by Mary Beth Strawn.

  1. ♪ (music playing) ♪

  2. (Moises Bernal) There were three females
  3. of brownbanded bamboo sharks
    here at the academy.
  4. And they were acquired in 2007
    from the Aquarium of the Pacific.
  5. 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
  12. is that there's one unfertilized egg
  13. that actually starts developing normally
  14. until it becomes a pup.
  15. Parthenogenesis is actually
    really common in the natural world
  16. but when we did the genetic testing,
  17. what we did is that we compared
    the three females
  18. with that pup and we actually found
    that the pup
  19. was the most dissimilar
    organism of the three.
  20. He was so, so dissimilar
    that we couldn't even tell
  21. which of the females was the mother.
  22. We think that that genetic information
    actually came from a father.
  23. That's where the story
    gets really interesting
  24. because what we think happened
  25. is that the female actually stored sperm
  26. from one of the males
    at the Aquarium of the Pacific
  27. for a really long period of time.
  28. Actually, sperm storage is not
    a well-known strategy
  29. but it's fairly common for insects.
  30. And in the case of vertebrates,
    it happens very often in snakes.
  31. And this is really exciting
    because what we think happened
  32. is that one female stored
    sperm for 45 months
  33. and that's the longest amount of time
  34. that we know any shark storing sperm.
  35. So those two strategies are actually
    found in solitary species
  36. in which encounters between
    males and females
  37. are actually very rare.
  38. In the case of sharks,
    there's a lot of questions
  39. about conservation when we touch
    this topic of parthenogenesis
  40. and sperm storage.
  41. And the reason behind this is that
    with dwindling shark populations,
  42. encounters between males and females
    may actually become
  43. even more rare.
  44. And in those cases, a lot of scientists
    think that parthenogenesis
  45. might become more common.
  46. If parthenogenesis becomes more common,
    you may have a population
  47. with several individuals
    but all those individuals
  48. are going to be very,
    very similar to each other.
  49. That means that genetic diversity
  50. is actually going to be
    very, very reduced.
  51. So sperm storage is actually a strategy
    that allows that maintenance
  52. of that healthy genetic diversity
  53. that's going to help sharks
    be here on planet earth
  54. for many more years to come.
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