Two baby anaconda have been born into an Amazon exhibit at the New England Aquarium that has only adult females of the world’s largest snake species.
DNA testing has confirmed that the 2-foot-long, green anaconda youngsters are the product of nonsexual reproduction. The extremely rare reproductive strategy is called parthenogenesis, which translated from its Greek word origins means virgin birth.
Parthenogenesis is much more common in the plant and insect worlds. This process, which allows a female organism to replicate itself without fertilization from a male, is extremely rare among vertebrate species. Parthenogenesis has been documented in a limited number of lizard, shark, bird, and snake species. This is the second known confirmed case of parthenogenesis in green anaconda, as three were born at a zoo in the United Kingdom in 2014.
Earlier this past winter, the newborn snakes were unexpectedly discovered by Aquarium staff in the rainforest exhibit. Biologists discovered in January that 8-year-old Anna, a 10-foot adult anaconda weighing about 30 pounds, was still in the process of delivering more young, most of which were stillborn, which is quite common in parthenogenesis among vertebrate species. Initially, three babies survived, but one died of within a couple of days. Since then, the other two juveniles have thrived.
Aquarium veterinarians immediately expected parthenogenesis, but they had some detective work to do to rule out other possibilities. Anaconda do not have any difficulty reproducing in aquarium settings, which is why the Aquarium’s popular Amazon exhibit features three adult females.
Physical exams were already on the schedule, so the anaconda snakes were closely checked to reconfirm their gender. Also ruling out a delayed embryo implantation was on the list, if there had been a previous exposure to a male. But Anna’s life history was well known. She had been born in the care of a certified reptile organization and had come to the Aquarium as a very young animal with no exposure to adult males. The ruling out process had eliminated any other suspects but parthenogenesis, yet testing the DNA was the only way to have a positive confirmation. Aquarium veterinarians sent off tissue samples for analysis.
Many weeks later, the results acknowledged what most Aquarium staff had suspected that Anna had reproduced nonsexually, or by parthenogenesis, which also occurs in the wild.
The next most popular question is, “Are the young clones of Anna?” There can be different kinds of parthenogenesis, many of which do not yield exact DNA copies of their mother. However, the limited genetic sequencing done for these two young snakes shows complete matches on all the sites tested. These two young appear to be genetic copies or clones of the mother.
The anaconda youngsters are not yet on exhibit and are still being care for behind the scenes. They eat about once a week. The two have differing personalities; the thinner of the two juveniles is laid back, while the heavier juvenile is more apt to explore and check out its surroundings by sniffing out items with its tongue.
The two have been held every day of their short lives. Aquarium staff want the snakes to be used to people and handling, as it makes it much easier to perform checkups and other procedures when they get much bigger.
Image: Aquarium Biologist Tori Babson holds one of the two juvenile anacondas while talking with members of the media.