Sharks give birth without males

A zebra shark in Australia unexpectedly gave birth to three babies without a male .

The zebra shark Leonie (scientific name Stegostoma fasciatum) met his mate in 1999 in an aquarium in Townsville, Australia. They fell in love with each other and had more than two dozen children before the male was moved to another place in 2012.

From then on, Leonie did not have any heterosexual relationships. Until the strange thing happened in early 2016, Leonie unexpectedly gave birth to three young children.

Because of curiosity, Christine Dudgeon - a graduate student at the University of Queensland in Brisbane (Australia) and colleagues began to delve into the research in hopes of finding a satisfactory answer.

One of the three baby sharks was born in the absence of a father.

The assumption is that Leonie has stocked her ex partner's sperm and reused it for later conception. However, this was quickly dismissed when scientists did an experiment soon after and found that these baby sharks carried only their mother's genes. This means that these children are born in asexual reproduction .

Several other heterosexual species also have asexual reproductive abilities such as turkeys, Komodo dragons, snakes and rays. However, most of these species have never reproduced in a sexual form (ie mating with males). Therefore, Leonie's own child even though he had previously mated with a male, is considered rare. Previously only eagle and snake-stingray rays were able to convert from sexual reproduction to asexual. There are few cases where the opposite is true.

In sharks, asexual reproduction may occur when the female eggs are fertilized by a inbreeding cell. The ability to reproduce sexually may be a mechanism of survival in the absence of males, but it also has many limitations such as reducing transmission diversity, poor adaptability.

However, in the short term, it can be said that this is the best temporary way to maintain the race."That might be a waiting mechanism. The mother's gene is passed on to female sharks until a male is to breed," Dudgeon said.