As Ian Malcolm famously said, "life finds a way."
Aquarium keepers in Australia realised that back in June last year when a captive leopard shark gave birth to three pups—without having had any contact with a male for years.
The 20-something shark at Reef HQ Great Barrier Reef Aquarium in Townsville laid 41 eggs without a father. Three of them hatched into healthy pups, all female.
The pups were named Cleo, CC, and Gemini. Their mother is called Leonie.
Although this phenomenon of "virgin birth" is quite rare, it's not unheard of in sharks. Virgin births have been observed in bonnethead sharks, a type of small hammerhead, in the wild. And they have been recorded in a number of captive sharks over the years, as well as many other types of animals, from snakes to invertebrates.
"We have seen this process, called parthenogenesis, in a number of shark species, particularly in aquaria," says George Burgess, a shark expert with the Florida Museum of Natural History.
At first, scientists thought the pregnancies were due to females storing up sperm from past mating encounters, something they can do for years. But that was disproven after several sharks gave birth with no access to males at all. The females reproduced without mating.
"I think it happens when they get pushed into an evolutionary corner, like in an aquarium with no males around," says Burgess.
The upside is that life finds a way. The downside is loss of the genetic diversity that comes from mixing the DNA of two parents. Although there can be some reshuffling of a mother's DNA during a virgin birth, the opportunities are more limited than with two parents.
The resulting pups may be less able to fight off infections or deal with life's challenges.
Leopard sharks (Triakis semifasciata) are small sharks that live along the western coast of North America. They typically measure four to five feet (1.2 to 1.5 meters) long and are covered with large spots, giving them their name. They are often found in shallow water, sometimes in schools, and feed on fish and invertebrates.
"Sharks never cease to amaze us," Burgess says.
Update 17.01.2017 The amazing process of Leonie's parthenogenesis has just been described in the journal Scientific Reports . Researchers who documented her sexual change say this finding has implications for conservation because it shows how flexible the sharks' reproductive system is. Next up, more questions are yet to be answered by following the development of Leonie's pups.
“You lose genetic diversity with generations of asexual reproduction, so we’ll be seeing if these offspring can mate sexually themselves,” says lead author of the study Dr Christine Dudgeon.
Leonie is actually a member of the endangered zebra shark species (Stegostoma fasciatum). These sharks start out with quite pronounced stripes that develop into spots later on, hence they are also commonly referred to as leopard sharks.
This story was first published on 30 June 2016.