Male-less Reproduction: Strange Biological Switch Observed In Shark For The First Time

This zebra shark (Stegostoma fasciatum) does not need a man. After spending years away from his partner, Leonie produced three healthy offsprings. Before being isolated, she lived with a partner for 12 years and they produced more than a dozen offsprings.

Christine Dudgeon at the University of Queensland in Brisbane, Australia, and her colleagues wanted to find an explanation.

New Scientist said that one of their hypotheses is that Leonie has stored the sperm of her previous mate and has used it to fertilize her eggs. But analysis showed otherwise. In fact, the DNA of the offspring was all traced back to Leonie.

The other hypothesis is parthenogenesis or asexual reproduction. This behavior, as mentioned by CNN, is a reproductive strategy thought to aid survival during periods of isolation. While it has been observed previously in other vertebrates such as other sharks, this is the first time female shark has been observed switching from sexual to asexual reproduction.

As of this time, only an eagle ray and a boa constrictor, both held in captivity, had experienced the same unusual biological which Leony had undergone.

The mechanism of the switch remains mysterious, but what is clear is that it endangers the animal's lineage as it does not promote genetic diversity. Leonie's offsprings would likely produce the same way she did. In fact, one of her offsprings, Lolly, already did. Popular Science said that lack of genetic diversity makes a population more vulnerable to diseases and mutations.

"One theory is that in the wild, if for some reason males can't have contact with the females for one breeding season, they can keep their lineage going for one or two seasons [through asexual reproduction], until they can reproduce the traditional way," said Hamish Tristram, a senior aquarist with Reef HQ, where Leonie and her offsprings are kept.

"[But] 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."

IUCN Red List highlighted zebra sharks as an endangered species and is protected under the Malaysian Fisheries Act.

Findings were detailed in a report published in Scientific Reports.