• A spotted salamander (Ambystoma maculatum). Image by John Clare, CC BY-NC-ND 2.0 (Flickr)Source: Flickr
A population of unisexual salamanders has been found to grow back their tails 1.5 times faster than their heterosexual relatives.
Signe Dean

5 May 2016 - 2:30 PM  UPDATED 5 May 2016 - 2:30 PM

Nature always finds a way - and sometimes that way is rather unexpected. In the Great Lake region in North America there’s a thriving and widespread matriarchy going by largely unnoticed, and that matriarchy is comprised of salamanders.

These all-female salamanders belong to the genus Ambystoma and have a unique method of asexual reproduction called ‘kleptogenesis’: the lady salamanders steal sperm from nearby salamander species, and use that to trigger development in their eggs without actually using the genetic material from the sperm.

Biologists have found this intriguing, because typically a lack of genetic diversity would mean such a population should fizzle out very quickly. But it appears that all-female Ambystoma have been around for about five million years, making them the most ancient unisexual vertebrates known.

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Genetically they’re strange creatures - unlike humans and most other animals who carry two sets of chromosomes, one from each parent (called ‘diploid’), the salamanders are ‘polyploid’, meaning they have more than two sets of chromosomes.

In fact, they carry up to five times more genetic material than a typical salamander. It's thought that they’ve picked it up along the way, presumably when the occasional egg actually incorporates the dad’s chromosomes as well.

Salamanders are most famous for their amazing ability to grow back whole body parts, so in a recent study at Ohio State University scientists decided to compare the regeneration capacity between unisexual salamanders and regular salamanders collected in the same local area.

"I was wondering what makes them thrive, and there are some things that might point to them regenerating body parts at faster rates," says Monica Saccucci, who led the study as an undergrad and now studies medicine at the University of Cincinnati.

It became clear quite quickly that these all-female salamanders are perfectly fine without men. The ones in the study grew their tails 36% faster than their regular, sexually reproducing counterparts. The results were recently published in the Journal of Zoology.

Scientists think the most likely explanation for this could be the polyploid nature of their genes - with more genetic material swishing around their cells, unisexuals could indeed be more efficient.

"More genomes means more genes which produce more RNA which make proteins and that causes a much faster pipeline to producing more tissue," says study co-author Robert Denton.

Salamanders rely on their tails a lot - for swimming and for distracting predators - so having faster regeneration rates is a boost to their survival. And without the added messiness of having to mate, these all-female salamanders are probably set to continue thriving and outcompeting their neighbours.

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