There's a bit of a mystery going on at the Aquarium and Shark Lab in Hendersonville, North Carolina, after a stingray became pregnant despite no male stingrays being present. While an interesting mystery in its own right, the case has drawn extra attention after suggestions by the head of the aquarium that the stingray could have been impregnated by a shark.
"Our stingray, Charlotte, is expecting! We have held this close to our hearts for over 3 months," Team ECCO, which runs the aquarium, announced on Facebook alongside ultrasound scans. "The really amazing thing [i]s we have no male ray!"
There are of course a few options for how rays could become pregnant without the presence of a male. Some species of ray can store sperm for later use, but no male stingrays have been kept in the tank with Charlotte at all, Brenda Ramer, founder and executive director of Team ECCO, told ABC 13 News.
However, there were males of another species in there with her, leading to the unlikely (but not completely out of the realms of possibility) claim that a shark could have impregnated her.
"In mid-July 2023, we moved two 1-year-old white spot bamboo males (sharks) into that tank. There was nothing we could find definitively about their maturation rate, so we did not think there would be an issue," said Ramer. "We started to notice bite marks on Charlotte, but saw other fish nipping at her, so we moved fish, but the biting continued."
During mating, male sharks – including bamboo sharks – bite the females in order to get into position, suggesting to the team that this might be an explanation. Hybrids are possible, though generally between two genetically similar species that have not long diverged, and there are no documented cases of sharks breeding with stingrays.
"I'm going to stop this misinfo in its tracks," Dr Noah Bressman, assistant professor of physiology at Salisbury University, explained on Bluesky. "Sharks [and] rays are as distantly related as humans [and] snakes, so a snake knocking up a human is just as likely as a shark knocking up a ray."
Hybrids of species that parted ways long ago have been discovered, though they are incredibly rare. In 2020, a team found a hybrid of an American paddlefish and a Russian sturgeon, two species that last shared an ancestor in the Jurassic era.
But there is a much more likely explanation for the mystery. Though rays can reproduce sexually, in rarer cases they can develop an embryo without fertilization, known as parthenogenesis, a term which stems from the Greek words for “virgin birth”. Birth by this method, though still uncommon, happens every now and then. In fact, one shark at the aquarium has given birth via parthenogenesis 14 times.
Though it is rarer in rays, it is still much more likely than what would be the first known hybrid of this kind. Either way, it's still exciting, and we will have our answer soon, with the ray expected to give birth by the end of the week, and the team planning DNA tests on the pups afterward.
"We're either going to have partho babies," Ramer added, "or we're going to have some kind of a potential mixed breed, and we're waiting for Jeff Goldblum to show up because we are Jurassic Park right now!"