How did an aquarium stingray get pregnant without a mate?

Charlotte, a stingray at a small North Carolina aquarium, is taking a DIY strategy to breeding.

Stingray in aquarium

A stingray at a small aquarium in Hendersonville, NC, has grow to be pregnant — regardless of dwelling in a tank with out male rays.

The seemingly miraculous occasion has sparked on-line hypothesis that the expectant stingray, Charlotte, could also be pregnant by one of many smaller sharks sharing her tank on the aquarium and shark lab. However consultants say that equal to strategies that lion and wolf infants may very well be “lee-wolves” (“wolves”?), that is terribly unlikely.

In actual fact, shark-ray infants can be extra dramatic than that, says Damian Chapman, director of the Florida Mote Marine Laboratory and Aquarium’s Shark and Ray Conservation Program. The final frequent ancestor of cats and canine lived about 45 million years in the past. Sharks and rays separated from one another a minimum of 300 million years in the past, in keeping with a 2021 paper within the journal Rising Biology.

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There’s one other rationalization for Charlotte’s impending motherhood, although, and it is no much less unusual: she virtually definitely impregnated herself, a phenomenon often known as parthenogenesis.

“A number of species of sharks and rays are recognized to breed like this in captivity,” stated Chapman, who studied the primary recognized phenomenon. Parthenogenesis in a hammerhead sharkWhich occurred in 2001 “We even have proof that one species of ray is doing this within the wild.”

Charlotte, a spherical stingray (Urobatis halleriIn line with the aquarium and shark lab run by the nonprofit instructional group Workforce ECCO, she has a noticeable child bump (seen each on her backside and on her again) and may give delivery at any time. Being pregnant was confirmed by ultrasound. Georgia Aquarium analysis scientist Cady Lyons stated Charlotte can be the primary recognized spherical stingray to bear parthenogenesis. “It is nice that we have now one other documented case of this in a brand new species,” Lyons stated.

Researchers do not totally perceive why parthenogenesis happens or what triggers it. Here is how the method works: Inside the feminine physique, cell division produces intercourse cells, or gametes. This division, known as meiosis, ends in the formation of the egg, which might ultimately be fertilized by a sperm, and three extra cells known as the polar physique. Half of the gene complement wanted to create a brand new organism is contained within the egg and every polar physique. In parthenogenesis, a polar physique fuses with a fertilized egg, triggering the formation of an embryo.

That is completely different than cloning, warns Lyons, which might create a precise copy of the mom ray. In parthenogenesis, since each the egg and the polar physique include a part of the mom’s genome, the offspring are much less genetically numerous than their mom. Some parthenogenetic species get round it by doubling their genes earlier than dividing their intercourse cells: the species whiptail lizards Aspidocellis This fashion simply get alongside wonderful replica. However for a lot of different species that sometimes bear parthenogenesis, the offspring is probably not as robust, Lyons says. “You’ll be able to consider them as a high-born particular person,” he provides.

Even the easy round stingray is unusual to breed. Feminine stingrays mate with a number of males within the spring and provides delivery to litters with a number of completely different fathers three to 4 months later, Lyons stated. And so they bathe their fetuses in a form of nourishing uterine fluid, not in contrast to mammalian milk, that provides them the vitality to outlive after they emerge. At delivery, infants are lower than three inches in diameter—the diameter of a baseball—and are able to fend for themselves.

“They’re tremendous lovely,” Lyons stated.

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