Who's the father? Stingray's pregnancy baffles aquarium with no males to mate

A female stingray at a North Carolina aquarium is pregnant, leaving staffers puzzled over how a fish living without a male companion is reproducing.

The Aquarium & Shark Lab by Team ECCO in Hendersonville announced in a Facebook post on Tuesday that its stingray Charlotte is expecting.

But, according to the aquarium, there's something fishy about the pregnancy because they don't have any male stingrays in the tank.

Still, there are two possible explanations for this "once in a lifetime science mystery." One way is a very rare process called parthenogenesis, in which the eggs develop on their own without fertilization and create a clone of the mother, according to BJ Ramer, founder and director of the aquarium.

Ramer told NBC affiliate WRAL that they began doing ultrasounds on Charlotte in September when she started to "swell." The aquarium's vet identified the growth as eggs and said noted that despite the absence of a male ray, "there have been few cases of parthenogenesis in rays."

The second explanation for Charlotte's pregnancy is bit more weird science. Ramer said the stingray may have mated with a male shark that was added to the tank in July.

"In mid-July 2023, we moved two 1-year-old white spot bamboo males into that tank. There was nothing we could find definitively about their maturation rate, so we did not think there would be an issue," Ramer told the station. "We started to notice bite marks on Charlotte, but saw other fish nipping at her, so we moved fish, but the biting continued."

According to SeaWorld, sharks bite females on the fins during the mating process to hold onto them. Ramer said Charlotte had several bites on her edges of her fin.

Charlotte is believed to be carrying up to four pups and could deliver at any time. A DNA test will be done after the pups are born to reveal whether they are a cross of breeds or a clone of the mother.