Stingray's mystery pregnancy leads to Aussie vet's wild theory

The female stingray fell pregnant despite the aquarium having no males in residence.

A pregnant stingray doesn't usually attract global attention but the mystery of how Charlotte the ray became impregnated in a US aquarium holding no males has bamboozled observers the world over.

Staff at the North Carolina facility initially kept the pregnancy news under wraps as they sought answers, but confirmation from experts, including Melbourne aquarium vet specialist Dr Robert Jones, that the animal could indeed have been impregnated by a shark encouraged the information to be shared online.

"Our stingray, Charlotte, is expecting! We have held this close to our hearts for over three months," staff from the Aquarium & Shark Lab by Team ECCO wrote before hosting a livestream offering further details.

Charlotte the stingray in the Aquarium & Shark Lab in North Carolina.
Charlotte the stingray's mystery pregnancy has Aussie vet Dr Robert Jones believing she has been impregnated by a shark. Source: Facebook

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

Theories of stingray pregnancy explored

Staff believe there are two plausible ways the stingray could have become pregnant, with the first involving some form of asexual reproduction where eggs develop without fertilisation — creating a clone of Charlotte. However, stingrays are not known to do this.

The ultrasound shows a bump in the stingray's abdomen.
Staff at the aquarium initially thought the stingray's swelling was cancerous and they carried out ultrasounds. Source: Facebook

The most likely explanation is the stingray mated with one of the two one-year-old male sharks which were placed in her tank mid-last year.

"We moved two one-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 in the livestream.

As time went on staff noticed bite marks on Charlotte — a known sign of shark mating. It is this information which points to Jones' and aquarium staff's reasoning that one of the sharks is responsible for her pregnancy.

The birth of the pups is expected any day now, and DNA tests will determine if the young are half-shark.

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