A female zebra shark gives birth to three babies, all alone!
It was in an Australian aquarium that a female zebra shark laid eggs that contained embryos without having been fertilized. If this mode of reproduction has already been observed in Nature, it is a first for this species.
Leonie is a female zebra shark from the Townsville Aquarium in Queensland, Australia. Nothing exceptional so far, but the beauty surprised everyone a few weeks ago by giving birth to three pups without having been fertilized. While this is not the first time that such a miracle has occurred, Leonie’s case remains unique.
Reproducing alone is possible. Parthenogenesis is a form of single parent reproduction in which embryos develop in the absence of fertilization. This is a rare phenomenon, but some vertebrates are nevertheless able to reproduce asexually. On the other hand, most often the accounts of these parthenogeneses relate to females who have never had a male sexual partner. However, here, Leonie became capable of reproducing alone after having had descendants with a male from which she was separated. The female shared her environment for several years with a male and had different viable litters with him before being separated in 2012, the aquarium having decided to reduce its breeding program.
It is therefore a first for this species. “Cases of non-sexual reproduction at the start of sexual maturity have already been observed in sharks, rays and especially in reptiles,” Christine Dudgeon, biologist at the University of Queensland, told Guardian Australia. “But this is the first time this has happened after sexual reproduction.” While she has not had contact with other males since 2012, Leonie therefore still had three pups in 2016, knowing that female sharks can store sperm up to four years old. Only genetic testing showed that baby sharks only had DNA from their mothers. This is “a severe case of inbreeding,” added the scientist.
According to the researchers, this rare phenomenon may be an illustration of the evolution of species to allow females to reproduce despite a shortage of males. This was particularly the case after the various mass extinctions that sharks have successfully crossed for 400 million years. But this strategy is not always a win-win: individuals from such a mode of reproduction are often sterile.