Without male shark insemination, female sharks can have children? On December 14, 2001, a female hammerhead shark in a zoo in the United States gave birth to a child after three years of no contact with a male shark, and this small shark shocked the world.
But hammerhead sharks generally give birth to children in 9-10 months of pregnancy, and the 3 female hammerhead sharks in the aquarium are all 3 years ago, and this baby shark was never conceived before coming to the zoo.
Because the 3 sharks that came at that time were not sexually mature, if there were sperm in the body, the sperm could only survive for five months at most, and they could not get pregnant.
Someone once joked that the water in this aquarium was not drawn from the daughter's country?
Of course, this is even more unlikely, so could it be that one of the other two sharks is hermaphrodite, that is, has two reproductive systems?
After all, there are indeed many animals in nature like this, even humans, a British medical journal has reported that there is a newborn with both male and female reproductive organs, part of the cell has XY chromosome, and some of the chromosome is XX, doctors speculate that it is possible that when the child is in the womb, it is likely that two different embryos are embedded in the process of development.
But according to the researchers' identification, it was confirmed that the other two sharks were not hermaphrodites.
After the baby shark was attacked and killed by other sharks, the scientists analyzed the DNA of the baby shark's carcass and found that the baby shark had only half of the mother's genes, and no father's genes.
So the only answer is that sharks can reproduce unisexually (parthenogenesis).
In 2002, in an aquarium in Detroit, the United States, a female white-spotted bamboo shark who had not been exposed to male sharks for 6 years gave birth to 2 children, which not only proved that shark unisexual reproduction is not unique, but also not only hammerhead sharks can reproduce unisex. Even the daughters they give birth to unisexual reproduction are able to reproduce as parthenogenetically.
Deming Kempman, a marine biologist at the State University of New York at Stony Brook, has studied the female leopard shark known as "Zebedee" at the Sail Hotel in Dubai, which has been undergoing unisexual reproduction for 4 consecutive years.
It first spawned in 2007, when experts in Dubai felt that these eggs could not hatch small sharks, after all, there were no male sharks in the pool, but to their surprise, these eggs actually hatched sharks.
But this mode of reproduction is not a good thing for sharks, because it can only be regarded as an emergency mechanism to ensure that they can help the population maintain a certain number when the population density is too low.
"When female sharks adopt this method of reproduction, they reproduce significantly fewer offspring than the sexual reproduction method after mating with male sharks," Kempman said. ”
And in the process of unisexual reproduction, in order to avoid the birth of children and the mother's genes are exactly the same, the DNA of the baby shark will undergo some recombination, but this is still not as good as sexual reproduction, in the long run, the genetic diversity of the shark population will decrease, and the immune system of the newborn baby shark will also decline.
With the large number of sharks hunted by humans, which has caused a sharp decline in the number of sharks in some areas, biologist Paul Proder believes that in this case, if the female shark can not choose enough males, the phenomenon of unisexual reproduction will continue or continue to increase, which may cause a further decline in shark populations.
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