Artificially Inseminating Sharks Reveals "Virgin Births" May Be More Common Than Thought

Some bamboo shark pups born of artificial insemination had fathers from far away while others didn't have a father. Image credit: Jay Harvey, Aquarium of the Pacific

A toothy predator with a thirst for blood might not be such an easy sell as a species in need, but sharks play a vital role in ocean ecosystems and protecting them is as worthy a conservation effort as any other. Under threat from fishing, pollution, and warming oceans, shark populations are in decline and a vital tool in ensuring their future is captive breeding programs.

In these programs, zoos and aquariums across the globe work together to matchmake male and female sharks in a way that promotes genetic diversity. This may mean pairing up sharks a long way from each other, so bringing the forecasted lovers together IRL can be a bit of an undertaking.

A new study published in the journal Scientific Reports was able to create 97 baby sharks (doo, doo, d’do d’do…) using artificial insemination. Some babies were born of parents from across the country while others turned out to have no father at all. The project aimed to hone shark artificial insemination as a tool so that geographical location was no longer an obstacle for “mating” as only the semen needed to be transported. The method could preserve genetic diversity while alleviating stress on traveling animals (though it turns out sharks on a highway are a thing in Texas).

Focusing on conveniently small whitespotted bamboo sharks (would you collect sperm from a great white?), the researchers first made sure that candidate mothers weren’t still carrying sperm from a past fling. Whitespotted bamboos lay so regularly that they’re known as “chickens of the sea”, so their output of infertile eggs could be used as an indicator that they were suitable for insemination.

"Mermaid purse" shark eggs can easily be checked to see if they're fertilized. Image credit: Callie Boatright, Aquarist Ripley's Aquarium

Next came the semen collection, 82 samples of which were taken from 19 sharks. How, you ask? “The short answer is very carefully,” lead author Jen Wyffels told IFLScience. “Although there are differences between shark species, in general, semen accumulates in paired ampullae or seminal vesicles located at the end of the reproductive tract, near the cloaca. Semen leaves the male through the urogenital papilla, which can be accessed from the cloaca. Semen can be collected using a catheter passed through the urogenital papilla or it can be expressed by applying pressure on the body overlying the ampullae/seminal vesicles.”

Some samples were given to female sharks in the area, while others were kept in cool storage and shipped off to females at Ripley’s Aquarium of the Smokies and the Aquarium of the Pacific in the US, journeys which took between 24 and 48 hours. Females were inseminated after being sedated in a procedure that took less than 10 minutes.

Four months later, tissue samples were taken from all the babies and their parents for DNA analysis. By matching up the babies to parental sperm samples, the researchers were able to ascertain that freshly collected semen was 27.6 percent effective compared to semen that had been cold-stored for 24 and 48 hours, which were 28.1 and 7.1 percent effective, respectively.

Shark hatchlings hanging outing out in a tube. Image credit: Photo by Jay Harvey, Aquarium of the Pacific

Interestingly, the analysis also revealed that two pups were born of parthenogenesis, where the mother reproduces on her own. “It may be more common than we think,” said researcher Kevin Feldheim who led the DNA analysis, in an email to IFLScience. “The first cases of parthenogenesis were discovered in an aquarium setting. In fact, every case but one has been discovered in an aquarium. Before this study, parthenogenesis had occurred in nine different aquariums (from seven different species of elasmobranchs).”

The researchers hope their work can broaden the reproductive opportunities for shark breeding programs. “There have been other reports on artificial insemination of sharks, but they include very few females,” said Wyffels in a statement. “In this study, we’re in the double digits and as a result, we could investigate different methods for preparing and preserving sperm for insemination. And a hatchling from shark parents that live almost 3,000 miles apart from sperm collected days in advance, that’s definitely a first.”


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