About a week ago, the New England Aquarium in the US announced that a “virgin” anaconda had given birth during the winter. The aquarium does not have a male anaconda. Yet Anna, a green anaconda, gave birth to a few babies in January, two of which have survived. In scientific terminology, it is know as parthenogenesis.
How it happens
The Encyclopedia Britannica defines parthenogenesis as “a reproductive strategy that involves development of a female (rarely a male) gamete (sex cell) without fertililisation. It occurs commonly among lower plants and invertebrate animals (particularly rotifers, aphids, ants, wasps and bees) and rarely among higher vertebrates”. A gamete is the egg in females and the sperm in males. In animals, parthenogenesis means development of an embryo from an unfertilised egg cell.
Many species that reproduce through parthenogenesis do not reproduce sexually. Others switch between the two modes taking cues from the environment. Anna is a higher vertebrate, which is why the birth of her two babies has been met with so much surprise.
The term parthenogenesis is a amalgam of the Greek words parthenos meaning virgin and genesis meaning origin. About 2,000 species are known to reproduce through parthenogenesis, which is one of the known means of asexual reproduction. Grafting (of plants) is also a type of asexual reproduction.
Clones of mother
Babies born through parthenogenesis are clones of the mother, as has now been confirmed by the aquarium through DNA tests. Parthenogenetic offspring tend to be clones of the parent because there has been no exchange and rearrangement of genetic information with another individual as happens in case of a sexual reproductive process. Each of Anna’s babies is a tiny Anna in every possible way. Many of the babies, though, were stillborn. Since the birth in January, only two have finally survived. Stillbirth is common in parthenogenesis. In some species, offspring born by parthenogenesis from a mother can also be male but it lacks one X chromosome.
Rare in snakes
This is only the second known case of parthenogenesis in green anacondas. It is not unknown in snakes, but undocumented enough to make it to scientific journals. In 2018, researchers from the University of Adelaide reported in the Royal Society Open Science Journal about facultative (optional) pathenogenesis in elapid snakes (Elapidae), which include well-known taxa such as cobras, mambas, taipans and sea snakes. In 1998, researchers from the Kansas State University reported that a copperhead snake that had been in captivity and without any male contact for three years had given birth to two female offspring by parthenogenesis.