Unisexual salamanders in the genus Ambystoma appear to be the only creatures in the world that reproduce the way they do. Researchers know how, but the why is still being figured out.
Katy Greenwald: These are all pond breeding salamanders. They are really abundant in the Great Lakes. They are gene thieves. They're stealing DNA from other species. It is known as kleptogenesis. They are usually just called the unisexual complex or the unisexual Ambystoma. They are not a species, actually, because they break all the rules of what a species should be able to do.
They are a really unique lineage. As far as we know there is nothing else in the world that reproduces in this way. They are five or six million year old group of animals. As a biologist, you learn all these rules and intro bio and then you learn about these things that just break the rules. In the water, the males will produce sperm at offers, which are little sperm packets that they sort of put down on on leaves and sticks and things like that in the pond.
And the females will pick those up internally in their cloaca and there's internal fertilization, and then they'll lay fertilized eggs, which will develop into larvae just like tadpoles do in frogs. And these unisex rules will be in the same ponds at the same time as these normal sexually reproducing species. And they will actually pick up the sperm at offers that are produced by the males of the other species that just triggers egg development.
So their eggs are laid and they develop, but they don't actually include any of the males genetic material and they produce offspring that just have the same DNA as the mom. But a smaller proportion of the time they actually do add the males genomes, and so then the offspring come out with extra chromosomes. So they can have anywhere from two to five full sets of chromosomes from up to five different species.
And these salamanders seem to have the benefits of asexuality in that they're all female. Their populations can grow really fast, but they have this mechanism to add additional genetic variation that they're able to grab from these species that they coexist with.
If there's one thing that we learn from studying biodiversity, it's that there is amazing variation in nature. There are all kinds of species reproducing in all kinds of ways, using all kinds of different approaches. And I think that's something we could certainly learn from in human society, that valuing and celebrating that diversity is a great part of being a biologist.