A tiger shark kept in Townsville performed a miracle that has biblical proportions. The specimen is a normal fish that breeds exactly like all other creatures of the sea. Usually, the breeding process cannot be performed without the involvement of two parents of different genders. However, this time the tiger shark took the world by surprise when she was able to procreate without any help from a male. This event signals how a species in dangerous times is able to adapt in order to protect its future.
The World Conservation Union had no choice but to officially recognize the zebra shark as an endangered species at a worldwide level. This critical situation is the result of many years of people hunting them down for commercial purposes. They represent a rich source of liver oil, meat, and fins for the market.
Leonie is one female zebra shark that resides in ReefHQ Aquarium, Townsville. She had reportedly given birth before to several dozens of pups at the beginning of the 2000s. However, she has been separated from her male partner since then. This major factor was nonetheless without importance for her as she proceeded to hatch three more babies in April 2016. At this time, she had been living without a partner for three years.
It was only recently that the scientific world acknowledged this event as a very rare asexual breeding. This happens when a female can hatch eggs without the help of a male. The study of this situation appeared as an article in the Scientific Reports publication on Monday.
The author of the paper, Dr. Christine Dudgeon, is a postdoctoral researcher who works at the University of Queensland in Australia. Although Leonie’s case is extremely rare, she isn’t so shocked about this natural evolution. This phenomenon is known as parthenogenesis reproduction, and it usually is common among invertebrates. However, this type of reproduction does not appear so often among large vertebrate species, like the zebra shark.
Other past cases proved to be false alarms of a parthenogenesis process. The females were able to store the sperm for later use. However, this did not happen with Leonie. When scientists tested the DNA of the pups, they found only cells from their mother. However, their asexual birth withheld from them important genetic material that usually comes from the male parent. This problem of genetic diversity that creates weaker specimens is the reason why asexual breeding is not encouraged by nature. However, in dangerous times when a species is threatened by extinction, the females find a way to practice reproduction.
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