Biological Oddity: A Lab Made Lizard Reproduces By Cloning Itself

It’s a story that can make any respectable biologist go pale. A team of researchers based in Kansas have come up with a cross that can give birth by laying eggs that don’t need to be fertilized by a male, essentially a process of cloning.

‘Species’, ‘Speciation’ and an Exception

In biological sciences, a species’ is defined as a group of similar individuals that can interbreed and produce fertile offsprings. Speciation’, or the creation of new species from existing ones, involves gathering of sufficient genetic variation, so that interbreeding between two different species’ cannot produce an offspring, or at least, not a fertile one. (Take the example of a lion and a hedgehog. After suppressing the initial laughter peals, think about the fact that they cannot interbreed because they are genetically too different. A lion and a tiger are much closer cousins. They can, in fact, breed, but the offspring they produce a tigon (tiger and lioness) or a liger (lion and tigress) is incapable of breeding itself, i.e. it is infertile. Thus, there is a barrier to genetic exchange.

There is an exception to this rule. Whiptail lizards, native to New Mexico, have evolved by interspecific breeding. They are an all-female species. They reproduce by something called parthogenesis‘, literally meaning virgin birth’. This occurs very rarely in the world of vertebrates, but is more common amongst invertebrates.

Aspidoscelis exsanguis
A. exanguis, a species of the whiptail lizard, used for the experiment

And we have cloning…

The research team has demonstrated the artificial fertilization of an egg from a parthogenetic female Aspidoscelis exsanguis (picture above) with a sperm from a male of the species, Aspidoscelis inornata. (For science buffs, the female egg was triploid containing chromosomes in triplets, rather than in singlets – and the sperm was haploid, i.e. containing singlet chromosomes. The resulting zygote was tetraploid.) The resulting offsprings also had parthogenetic (self-birthing) capabilities. They can not only lay eggs, which need not be fertilized, but, crucially, also retain the genetic identity of the hybridization. They can, thus, clone.

The lizard offsprings are reportedly healthy and are in their third generation.

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