Virgin Dragons and Fossil Sharks

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This is more of a catch-up post than anything else. A few months back, it was announced that Flora, a Komodo dragon had laid fertile eggs even though she had never been with a male dragon. Now, just last week, it was announced that the eggs hatched.

The overall story is interesting, for it shows that parthenogenesis is more common in reptiles than previously thought (the original suggestion for this came from a timber rattlesnake [Crotalus horridus] that also gave birth to young without the aid of a male). Surprisingly the story doesn’t mention the sex of the babies. Reptiles that have genetic sex determination, rely on ZW and ZZ chromosomes. Unlike mammals, though, the heterogametic sex is female (i.e. they have the ZW chromosomes). This means that in a parthenogenic clutch of eggs, the choice of chromosomes is either ZZ (male), or WW (infertile), but never ZW. As such, all parthenogenic hatchling reptiles and birds, are male (there are exceptions for certain all parthenogenic species, but they create all females by doubling [tripling] their chromosomes). This has implications for colonization. A parthenogenic female can give birth to male offspring, which can then mate back to the mother (nasty, I know), and produce a more even sex ratio and a more stable blood line. Perhaps it’s because males are the heterogametic sex in mammals, that parthenogenesis is not found in this group. A female that can only give birth to other females, is far less likely to make a lasting line in new environments.

The second bit of interesting news, comes from Japan, where scientists report the discovery of a rare ancient shark. The frilled shark (Chlamydoselachus anguineus) is a rare site, as it usually lives hundreds of meters below the surface. The video that Reuters (and other news outlets) has, is stunning to watch. The shark almost looks like an animatronic piece of Hollywood fiction. It was unfortunate that this female didn’t survive. Hopefully we will be able to capture footage of healthier individuals in the future.

That’s it for now.


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