Did A Shark Really Impregnate A Stingray? Experts Weigh In

HENDERSONVILLE, NC — Biology 101 never covered this. Charlotte, a dinner-plate sized round stingray at a North Carolina aquarium, turned up pregnant in what originally looked like some kind of immaculate conception.

Charlotte, estimated to be between 12 and 14 years of age, hasn’t shared her tank with a male ray in at least eight years, according to Brenda Ramer, executive director of the Team ECCO Aquarium & Shark Lab in Hendersonville

“Here’s our girl saying, ‘Hey, Happy Valentine’s Day! Let’s have some pups,’” Ramer said in an announcement of the ray’s pregnancy on Tuesday.

Originally, Ramer and her team thought Charlotte had a tumor that was “blowing up like a biscuit,” she told The Associated Press.

An ultrasound confirmed the happy and somewhat mystifying news that the ray is pregnant.

“We were all like, 'Shut the back door. There’s no way,'” Ramer said. “We thought we were overfeeding her. But we were overfeeding her because she has more mouths to feed.”

Determining how Charlotte was impregnated involved eliminating some intriguing but ultimately unlikely theories.

Female rays can store sperm for long periods of time, like self-contained sperm banks, and get pregnant when they want. They can also be pregnant by multiple mating partners, confounding the question of parentage.

The least likely is that the stingray was impregnated by a shark, Ramer told ABC affiliate WLOS.

“People have written and said well they can hold male sperm for years and I’m like, she’s never been around a male until we put those two little boys (sharks) in here,” Ramer told the news outlet.

Ramer and her team noticed bite marks on Charlotte that suggested she had gotten close with either Moe or Larry, the sharks in her tank. Sharks are known for complex mating behavior. To impregnate a female, a male often must bite her back, flanks and fins, sometimes inflicting nasty-looking wounds as they angle for a position to mate.

Even with those maneuvers, sharks and rays could not match up anatomically, even if their DNA was compatible to produce offspring, Kady Lyons, a research scientist at the Georgia Aquarium, told The Associated Press.

Demian Chapman, a senior scientist and director of the Mote Marine Laboratory and Aquarium in Sarasota, Florida, told Forbes that he thinks the odds of a shark impregnating the ray are about the same as “Elvis or Bigfoot of being the father — zero.”

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Researchers said a more likely explanation is parthenogenesis, a type of asexual reproduction in which cloned offspring develop from unfertilized eggs, meaning there is no genetic contribution by a male.

The mostly rare phenomenon can occur in some insects, fish, amphibians, birds and reptiles, but not mammals. Documented examples have included California condors, Komodo dragons and yellow-bellied water snakes.

“This is a very interesting phenomenon and quite cool considering it occurs across so many species of sharks and rays, but we don’t really know why this is so common across this group of animals and not others,” Lyons said, adding:

“We should set the record straight that there aren’t some shark-ray shenanigans happening here,” said Lyons, whose graduate work focused on the species.

The phenomenon is “very rare,” Ramer told The AP. “But it’s happening in the middle of the Blue Ridge Mountains in rural North Carolina, hundreds of miles from the ocean.”

When Charlotte does give birth, which could occur at any time, DNA testing will confirm if the pups, which could number as many as four, are of a mixed breed or clones of their mother.

Round stingrays like Charlotte are abundant on the Pacific coasts of southern California and Mexico, often resting on the ocean’s sandy bottom near the shoreline.

In the wild, they are typically the size of a small dinner plate, and their name comes from their circular shape. They come in all shades of brown. They eat small worms, crabs and mollusks, and they are preyed upon by certain types of sharks, seals and giant sea bass.

They’re well known to humans because of their painful sting, often resulting from a beachgoer's foot stepping on them. Southern California lifeguards encourage people to do the so-called stingray shuffle as they wade through the water, in large part because of round stingrays.

Lyons finds the species fascinating. For example, embryos in the womb are bathed in uterine milk that provides nutrients to help them develop.

“I'm glad the round stingray is getting the media attention that it deserves,” Lyons said. “It’s not necessarily as sexy as a white shark, but they do a lot of really neat stuff.”

The Associated Press contributed to this report.