distribution of the Brahminy Blind Snake, or Flowerpot
Snake (Indotyphlops braminus), which has been also been
introduced to many parts of the world, including
Australia.
There are certainly adaptive benefits for facultative
parthenogenesis too, such as when populations become
fragmented and isolated, and there are few opportunities
for a female to encounter a male. Facultative partheno-
genesis has been documented in Komodo Dragons
(Varanus komodoensis) and snakes, including the early-
diverging taxa - boids and pythons - as well as more
‘advanced’ lineages. Parthenogenesis in these cases
typically occurs after normal meiosis when a haploid
polar body - a byproduct of oogenesis that usually
degenerates - essentially acts as a sperm, fusing with the
ova, activating it and restoring diploidy. Offspring
produced in this way are half clones of their mother; their
genomes are completely homozygous, and they should be
capable of sexual reproduction. A paper published in 2017
detailed the case of a female Green Anaconda (Eunectes
murinus) at Ueno Zoo, Japan, which was found to have
two fully-developed female neonates and 17 undeveloped
eggs in her oviduct, despite being isolated from males for
eight years and two months. DNA analyses of her
offspring, as well as those from offspring produced eight
years prior, revealed that her current progeny had been
produced parthenogenetically, whereas her previous
offspring had been produced through sexual reproduction,
thus confirming the first case of facultative parthenogene-
sis in the genus.
‘
Green Anaconda. (Eunectes murinus).
Image by Patrick K. Campbell.
‘
DNA analyses confirmed
the anaconda’s progeny
had been produced
parthenogenetically.
Most proven cases of facultative parthenogenesis have
(predictaby) been from captive individuals that have
popped out babies or eggs despite no history of an
opportunity to get frisky with a male. It is therefore not
known how commonly this strategy is employed
naturally, however facultative parthenogenesis has been
discovered in wild North American pit vipers.
The most recent reported case of parthenogenesis was the
subject of a paper published in June 2019 by scientists
from the Smithsonian Conservation Biology Institute,
Smithsonian’s National Zoo, St. Louis Zoo, and, closer to
home, the University of the Sunshine Coast. In 2006, a
four-month-old female Asian Water Dragon
(Physignathus cocincinus) arrived at the Smithsonian’s
National Zoo from the St. Louis Zoo, where she was born.
This individual was never meant to be a mum: the plan
was to display her as an ambassador for the species. She
was kept in an enclosure without any males, yet in 2009
she started laying eggs. Whilst it’s not uncommon for
agamids to lay eggs without having been bred with a
male, usually these are infertile. The staff at the zoo
discarded the first few clutches, but in 2015 zookeepers
were requested to incubate all eggs laid by females not
partnered with males, as part of a study investigating
sperm storage and potential parthenogenesis. Upon
candling the first clutch removed for incubation, develop-
ing embryos were seen. Although none of the eggs from
the first two clutches survived, on August 24, 2016, a little
‘Mini-Me’ of mum emerged from the third clutch. To
clinch the case that this was truly a parthenogenetically-
produced offspring, scientists took a DNA swab from the