Science, Now + Beyond

Jeff Goldblum was right: Life DOES find a way

A female shark has produced three eggs despite having no contact with a mate in three years.

Humans need to have sex to reproduce, but some organisms don’t. These include aphids, stick insects, and at times, even komodo dragons. Hammerhead and blacktip sharks have also been shown to undergo a form of asexual reproduction, called parthenogenesis, in the absence of a male mate. This discovery, however, is just a little more special.

The Discovery: What happened?

Last year, Dr Christine Dudgeon, a researcher at the University of Queensland, was looking after some sharks at a facility called Reef HQ Aquarium, when she noticed something very interesting. In April of 2016,  one of her charges, a leopard shark named Leonie, had managed produced three eggs without a male partner. From these eggs, three baby leopard sharks hatched. Researchers at the University of Queensland thought Leonie may have had sperm from a previous mate stored somewhere in her body. However, upon DNA testing, it was found that Leonie’s three babies only had her DNA. She had managed to reproduce asexually.

Leopard sharks are an endangered species.
Attribution: http://www.elasmodiver.com/Leopard%20Shark%20Pictures.htm

Why is this so cool?

Leonie had a mate, but the two were separated three years (or mating seasons ago). Other types of sharks have been shown to reproduce asexually if a male had not been available – AND they had never had contact with a male before. Leonie is the first known instance of a leopard shark reproducing asexually in the years following successful mating seasons. All three pups are female, as parthenogenesis creates offspring that are genetically identical to their mother.

Parthenogenesis in sharks vs. normal reproduction.
Attribution: http://www.nova.edu

Dr Dudgeon believes Leonie adapted to her circumstances of not having a male around – and adaptation comes about because of natural selection, an evolutionary process. “This has big implications for conservation and shows us how flexible the shark’s reproductive system really is,” Dr Dudgeon said. “What we want to know now is could this occur in the wild and, if so, how often does it? One reason why we haven’t seen it before could be because we haven’t been looking for it. It might be happening in the wild but it’s never been recorded in this species before.”

The Next Step

Leopard sharks are an endangered species, and this discovery could potentially hold the key to removing them from this list. Of course, more research needs to be done before a plan can be drawn up and implemented. Now that Leonie’s pups have been born, Dr Dudgeon will follow them until they reach maturity. This means she will be able to conduct more tests to see if they can reproduce “normally”, with other male sharks. This is important, as asexual reproduction decreases genetic diversity in animal populations. A thriving population of animals requires both numbers and genetic diversity, not just one or the other. Shark populations, in particular, are in danger as a result of climate change and overfishing.

With this information in tow, researchers will be better equipped to tackle this pressing issue. And hopefully, in time, we may be able to see these beautiful creatures grow and thrive in the world’s seas. This is, after all, where they belong.