Parthenogenesis in sharks
In 2001 a hammerhead shark gave birth, even though no mating had ever taken place. The baby died after three days and this was considered an isolated case. But now researchers have shown that sharks use this reproduction strategy more often.
Parthenogenesis is also called virginal reproduction. The eggs start dividing without having been fertilized. This always results in daughters who are genetically identical to the mother. An international team of researchers had the 2001 case in mind when a white-spotted bamboo shark laid eggs in the Detroit Zoo aquarium. The female had never had contact with a male in her adult life and the researchers believed her eggs were unfertilized. But to everyone’s surprise, two viable young were born. They stayed in the aquarium for five years before they were transferred to another aquarium. Research showed that the young were genetically identical to their mother.
The team thinks that sharks may have saved themselves from extinction by reproducing through parthenogenesis. Sharks have inhabited the planet for hundreds of millions of years and by parthenogenesis even an isolated group of females could reproduce.