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Female Sharks Give Birth Without Mating


After studying sharks in captivity, many scientists had been confounded about how female sharks were capable of giving birth without having to mate. However, according to the report in the Independent, scientists have been able to use a form of paternity test to establish the reasons behind the fairly unique ability that female sharks have.

Paternity Test – Making the Breakthrough

According to the report in the Independent, a team of scientists based in Northern Ireland and the United States made a breakthrough when studying the Hammerhead sharks that they had in captivity. A hammerhead shark that they had been studying gave birth without having mated with a male and after a paternity test was carried out on the newly born shark, it was found to contain no trace of any paternal DNA. This allowed the scientist conducting the research to postulate that sharks are capable of reproducing asexually due to their use of the rare parthenogenesis method. Speaking to the Independent, Dr Paulo Prodohl, of Queens School of Biological Science, stated, “The findings were really surprising because as far as anyone knew, all sharks reproduced only sexually by a male and female mating, requiring the embryo to get DNA from both parents for full development, just like in mammals.” However, the use of a paternity test was able to show that this was resolutely not the case.

Paternity Test – Theories Behind the Mystery

The scientists behind the breakthrough regarding shark’s asexual abilities initially believed that the female shark could have got pregnant prior to being bought into captivity and had somehow stored the egg for 3 years before fertilising it in the aquarium. However, after a paternity test was carried out on the offspring, it was shown to display no paternal DNA whatsoever and the DNA only matched the mother’s; which rules out earlier mating or hybridisation. Unfortunately, however, this type of asexual reproduction may have negative implications for the continued health of shark populations. Speaking to the Independent, Dr Prodohl stated, “Unfortunately, this occurrence is not benign because it results in reduced genetic diversity in the offspring since there is no new genetic variation introduced from the paternal side. The resulting baby shark therefore gets a double-dose of genetic disadvantage.”

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