Some Female Animals Don't Need Males To Reproduce, Scientists Find Out

An Asian water dragon hatched from an egg at the Smithsonian National Zoo, and her keepers were shocked. Why? Her mother had never been with a male water dragon.

Photo Insert: Parthenogenesis has been best documented in animals kept in zoo settings, like the Asian water dragon at the National Zoo.

Through genetic testing, zoo scientists discovered the newly hatched female, born on Aug. 24, 2016, had been produced through a reproductive mode called parthenogenesis, Mercedes Burns wrote for The Conversation on Dec. 27, 2021.

Parthenogenesis is a Greek word meaning "virgin creation," but specifically refers to female asexual reproduction. While many people may assume this behavior is the domain of science fiction or religious texts, parthenogenesis is surprisingly common throughout the tree of life and is found in a variety of organisms, including plants, insects, fish, reptiles, and even birds.

Because mammals, including human beings, require certain genes to come from sperm, mammals are incapable of parthenogenesis.

Sexual reproduction involves a female and a male, each contributing genetic material in the form of eggs or sperm, to create unique offspring. The vast majority of animal species reproduce sexually, but females of some species are able to produce eggs containing all the genetic material required for reproduction.

Females of these species, which include some wasps, crustaceans, and lizards, reproduce only through parthenogenesis and are called obligate parthenogens.

A larger number of species experience spontaneous parthenogenesis, best documented in animals kept in zoo settings, like the Asian water dragon at the National Zoo or a blacktip shark at the Virginia Aquarium.

Spontaneous parthenogens typically reproduce sexually but may have occasional cycles that produce developmentally ready eggs.

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