US stingray falls pregnant despite having no mate

Charlotte - a round stingray like the one pictured above - could give birth in the next two weeks

A stingray called Charlotte is pregnant despite not sharing her tank with a male for at least eight years.

Charlotte is a rust-coloured round stingray that has spent most of her life in an aquarium in North Carolina.

Staff originally thought that Charlotte's pregnancy was a tumour after noticing a growing lump on her back.

She could have as many as four young in the next two weeks, according to the aquarium's owner.

The pregnancy is likely due to a phenomenon called parthenogenesis.

This is a form of asexual reproduction where a female egg is fertilized without the sperm from a male. 

The process can occur in some species like insects, reptiles and even some fish.

Dr Kady Lyons, a research scientist for Georgia Aquarium, who is not involved with the North Carolina aquarium, spoke to the Associated Press and said Charlotte's pregnancy was the only documented example she was aware of for this species.

Dr Lyons explained that these animals are not cloning themselves. Instead, a female's egg fuses with another cell, triggering cell division which leads to the creation of an embryo.