Stingray pregnant in aquarium with no male companions

A stingray in a North Carolina aquarium is pregnant – despite not sharing a tank with a male of her species for at least eight years.

Charlotte, who has spent much of her life in a tank at the Aquarium and Shark Lab in Hendersonville in the Appalachian Mountains, is expected to give birth to up to four pups in the next two weeks.

Experts have said it would have been impossible for her to have mated with one of the five small sharks that share her tank.

The cause is parthenogenesis – a rare type of asexual reproduction in which offspring develop from unfertilised eggs which can occur in some insects, fish, amphibians, birds and reptiles, but not mammals.

A female’s egg fuses with another cell, triggers cell division and leads to the creation of an embryo.

Documented examples have included California condors, Komodo dragons and yellow-bellied water snakes.

Kady Lyons, a research scientist at the Georgia Aquarium in Atlanta, said Charlotte’s pregnancy is the only documented example she is aware of for round stingrays, although other kinds of sharks, skates and rays have had these kinds of pregnancies in human care.

“I’m not surprised, because nature finds a way of having this happen,” she said.

“We don’t know why it happens. Just that it’s kind of this really neat phenomenon that they seem to be able to do.

“We should set the record straight that there aren’t some shark-ray shenanigans happening here.”

Charlotte lives in a tank about 2,200 gallons and Brenda Ramer, executive director of the lab which encourages children to take an interest in science, said they are hoping to get a tank nearly twice that size to accommodate her offspring and install live cameras.

She said lab staff first thought Charlotte had a tumour when they noticed a lump on her back that was “blowing up like a biscuit” before an ultrasound revealed the pregnancy.

“We were all like, ‘Shut the back door. There’s no way’,” she said.

“We thought we were overfeeding her. But we were overfeeding her because she has more mouths to feed.

“It is very rare to happen. But it’s happening in the middle of the Blue Ridge Mountains in rural North Carolina, hundreds of miles from the ocean.”