Parthenogenesis

A shark in a Nebraska aquarium was proven to give birth through parthenogenesis through new DNA studies. I saw this a few days ago and meant to post on it and had forgotten until I saw a post by Brian Beutler which pointed out that it was oddly blogged with little comment by Jonah Goldberg in the Daily Corner, as Beutler postulated on consequences for a literal interpretation of the bible. I cannot say what Goldberg's intention was in bringing this up, but it is the first pop- science related post I have ever seen Goldberg make.

Anyways the whole thing got me reading a bit and I am now able to answer my own question as to why the Komodo Dragon produced a clutch of male lizards as opposed to an entire clutch of females.

I had originally asked ...

If anyone can shed some light on why parthenogenesis always results in all male clutches please do share as I do not understand why this is neccessarily true. If parthenogenesis were to happen in humans, the offspring would have to be female. I know that varanids lack a X-chromosome like most mammals, but why all males? It makes sense from an evolutionary standpoint, but the cell biology is confusing.

I had assumed that the offspring would all be females as they contain only the genetic material of the mother, but was stuck on mammalian biology. New Mexico whiptail lizards which reproduce entirely by parthenogenesis are all female, as would be required if that this is the sole method of reproduction, so I assumed that Varanids would be the same in the reptile world. Turns out the answer is that instead of an XX (female) XY (male) sex determination like whiptails, Varanids have a WZ (female) ZZ (male) WW (non-viable) sex determination. I do not know if temperature plays a role in sex determination in either of these genus like it was shown in Pagona vitticeps.

Image used under creative commons license: sponng