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Komodo Dragons: Immaculate Conception pt. 2

Komodo dragon is listed (or ranked) 3 on the list Immaculate Conception: Animals That Have Virgin Births

Another fascinating case of Parthenogenesis.

Parthenogenesis in Komodos is thought to have evolved in response to their remote environment, where mates may not always be accessible, rather than due to captivity, like sharks. The offspring, do derive all their genetic material from their mother but unlike other animals, rather than being strictly clones, half of the genes the female would normally contribute to sexual reproduction are instead doubled-up and passed onto her offspring. Hence, the offspring derives all its genes from the mother, but they are not a duplicate of her genome. 

Komodos have a curious twist in their sex determination. Although we think of females being XX (that is, having two X chromosomes) and males as being XY, it’s the other way around in these giant monitor lizards. Two identical sex chromosomes make a male Komodo, and two different ones make a female. Biologists label the Komodo’s sex chromosomes as W and Z, so ZZ makes a male and WZ makes a female. In other words, a female Komodo dragon can produce a perfectly healthy male, all by herself.

Fun fact: Embryos of some reptiles–notably crocodiles and turtles–don’t have any sex chromosomes; rather, the incubation temperature dictates their gender.


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