US aquarium suspects shark to have caused stingray's mysterious pregnancy

A stingray named Charlotte at a North Carolina aquarium is expecting babies, and staff believes it could have been impregnated by a shark as there were no male stingrays in her tank, Daily Mail reported.

In September, the Aquarium and Shark Lab by Team ECCO discovered Charlotte's swelling, which they initially suspected was cancer, but after ultrasounds, they discovered she was pregnant with multiple pups.

"We have been doing ultrasound on our ray, Charlotte, since September, when she began to swell. We documented multiple 'growths' internally and initially thought she had a cancer," staff member Ramer said.

There are two possible explanations for Charlotte's mystery pregnancy: parthenogenesis, where eggs develop independently without fertilisation and create a clone of the mother.

"I reached out to Dr. Rob Jones, the aquarium vet, and he identified the growths as eggs," said Ramer. "We have no male ray. He said there have been few cases of parthenogenesis in rays."

The other reason, staff believe, may have been a male shark placed in her tank in mid-July.

"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," Ramer said.

"We started to notice bite marks on Charlotte, but saw other fish nipping at her, so we moved fish, but the biting continued."

Bite marks on fin edges indicate mating in sharks, another employee explained, adding that Charlotte had several bites on her fin edges.

Charlotte’s pups will undergo DNA testing once they arrive in the next few days to determine if they are mixed breed or clones of their mother.

The gestation period for a stingray is typically three to four months.

Stingrays are flattened fish, closely related to sharks, belonging to the Elasmobranchs group. They have no bones in their body and a flexible cartilage skeleton.

They are ovoviviparous, hatching from eggs held within their bodies. Many stingrays live alone and only come together for breeding and migration.