Female shark left without a male for three years finds way to get pregnant

Tests on the pups’ cells showed they only carried their mother’s DNA

A leopard shark in Australia has made history after it became the first of its species to be observed switching from reproducing with a male to creating offspring completely asexually.

The research about Leonie the leopard shark's asexual reproduction has been published in Scientific Reports​, documenting a world first in this switch between normal and asexual reproduction.

Leonie had produced a number of litters at Townsville’s Reef HQ Aquarium in Queensland, but was separated from her male partner Leo in 2013 due to issues with space after its breeding programme was reduced.

But in April 2016 Leonie laid three eggs that hatched into leopard shark pups, also known as zebra sharks, the Brisbane Times reports.

The aquarium shared the news on its Facebook page last year, telling followers it was pleased to announce the arrival of Cleo and CC, two “healthy beautiful baby female leopard shark pups”.

At first, researchers believed Leonie the leopard shark had laid her eggs after storing the sperm from her partner Leo over the three year period, a method that has been previously documented in sharks.

But following DNA tests, the researchers discovered the pups only carried cells from Leonie. “Genetic testing of Cleo has conclusively shown that she is the parthenogenic offspring of Leonie,” the post read.

Parthenogenesis is process of reproduction without fertilization. Leonie’s is the first case of this species observed switching from reproducing by mating with a male to reproducing asexually.

Dr Dudgeon at the University of Queensland, told the Guardian that there have been cases recorded of female sharks reproducing asexually where they have never previously reproduced sexually with a mate. But, she said, Leonie's case marks a world first: "The onset of asexual reproduction with the onset of maturity has been documented before with sharks, and rays, and particularly with reptiles, but what we have shown for the first time is the switch."

Leopard sharks are an endangered species. Dr Dudgeon told ABC: “This is an extreme form of inbreeding, and the fact that these animals can survive, at lease for short periods of time, with this highly reduced genetic diversity really challenges the way we think about reproduction,” she said.

The researchers will now study the pups for the next six years until they reach maturity, to observe how they reproduce.