How Did an Aquarium Stingray Get Pregnant without a Mate?

By Stephanie Pappas

A stingray in a small aquarium in Hendersonville, N.C., has grow to be pregnant—regardless of dwelling in a tank with no male ray. 

This seemingly miraculous occasion has stirred up on-line hypothesis that the anticipating stingray, Charlotte, could have been impregnated by one of many small sharks that share her tank on the Aquarium & Shark Lab. However consultants say that’s terribly unlikely, on par with suggesting {that a} lion and a wolf may have child “li-wolves” (“wolvions”?).

In actual fact, shark-ray infants could be much more dramatic than that, says Demian Chapman, director of the shark and ray conservation program at Mote Marine Laboratory & Aquarium in Florida. The final widespread ancestor of cats and canine lived round 45 million years in the past. Sharks and rays diverged from each other no less than 300 million years in the past, in accordance with a 2021 paper in the journal Developmental Biology.

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There’s one other rationalization for Charlotte’s impending motherhood, although, and it’s not a lot much less bizarre: she nearly actually impregnated herself, a phenomenon often called parthenogenesis.

“Fairly quite a lot of species of shark and rays are identified to breed like that in captivity,” says Chapman, who studied the primary identified case of parthenogenesis in a hammerhead shark, which occurred in 2001. “We even have proof of 1 species of ray doing it within the wild.”

Charlotte, a spherical stingray (Urobatis halleri), has a noticeable child bump (seen on each her underside and her again) and will give beginning at any time, in accordance with the Aquarium & Shark Lab, which is run by the nonprofit academic group Group ECCO. The being pregnant was confirmed by ultrasound. Charlotte could be the primary identified spherical stingray to have undergone parthenogenesis, says Kady Lyons, a analysis scientist on the Georgia Aquarium. “It’s form of cool that we have now one other documented case of this in a brand new species,” Lyons says.

Researchers don’t absolutely perceive why parthenogenesis occurs or what triggers it. Right here’s how the method works: Inside the feminine’s physique, cell division creates intercourse cells, or gametes. That division, known as meiosis, ends in the egg, which may ultimately be fertilized by a sperm, and three further cells known as polar our bodies. The egg and every polar physique every include half of the complement of genes wanted to make a brand new organism. In parthenogenesis, a polar physique fuses with the unfertilized egg, triggering it to type an embryo.

That is totally different than cloning, Lyons cautions, which might create an actual copy of the mom ray. In parthenogenesis, as a result of each the egg and the polar physique include solely parts of the mom’s genome, the infants find yourself much less genetically numerous than their mom. Some parthenogenetic species get round this by doubling up their genes earlier than they cut up their intercourse cells: whiptail lizards of the genus Aspidoscelis get along just fine reproducing in this way. However for a lot of different species that solely often bear parthenogenesis, offspring won’t be as strong, Lyons says. “You possibly can consider them as a extremely inbred particular person,” she provides.

Even typical spherical stingray replica is quirky. Feminine stingrays mate with a number of males within the spring and three to 4 months later give beginning to litters with a number of totally different fathers, Lyons says. And so they bathe their fetuses in a form of nutritious uterine fluid, not not like mammal milk, that provides them a survival enhance after they emerge. At beginning, the infants are lower than three inches in diameter—in regards to the diameter of a baseball—and are able to fend for themselves.

“They’re tremendous lovable,” Lyons says.