Female Zebra Shark Reproduces Asexually
The animal kingdom offers amazing insights into our understanding of sexuality and gender. The latest development comes from Australia, where a female zebra shark has managed to produce live offspring asexually.
Though rare, so-called “virgin births” have been reported before—an eagle ray and a boa constrictor, for example, both in captivity. But this is the first time a female shark has been observed reproducing asexually after having a mate.
The shark, named Leonie, lived with a male partner at the Reef HQ aquarium in Queensland from 2006 to 2012. After she had several litters the old-fashioned way, Leonie was put into a separate tank to help scale back the aquarium’s breeding program.
Two years later, Leonie and one of her female pups, Lolly, both laid eggs and staff noticed some of them had embryos. Last year, Leonie and Lolly laid eggs again, and this time, three of Leonie's eggs and two of Lolly's evolved into live hatchlings.
Christine Dudgeon, a biologist studying the case, says there are two possible explanation: "One was sperm storage, which has been documented in several occasions. Sharks have been known to store sperm from male sharks for extended periods of time."
The other explanation is parthenogenesis, or asexual reproduction. Dudgeon says a genetic analysis of the hatchlings indicates elevated homozygosity, meaning more genes are identical, pointing to the likelihood of asexual reproduction.
"It was definitely a surprise," Hamish Tristram, a senior aquarist with Reef HQ, told CNN. "She had been mating successfully for several years, and there was nothing much published about such large animals switching reproductive strategy so quickly."
Zebra sharks, also known as leopard sharks, were once widespread in tropical areas around the globe, but they've become endangered by overfishing and degradation of their coral reef habitat. Still, while Leonie’s ability is fascinating, it’s not the ideal way to procreate: “The genetic diversity of animals gets greatly reduced using this reproductive method," said Dudgeon. "Long term, they need to diversify to help them adapt to their environment."

The next step is to wait for the offspring to mature and see if they can reproduce sexually themselves, something that has yet to be observed in such cases.