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This sneaky male fish steals eggs to clone itself

This sneaky male fish steals eggs to clone itself


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Photo by Isabel Catalao

For the first time, scientists have discovered a fish capable of cloning itself. The trickster in question is a small Portuguese fish that managed to steal an egg to do the deed.

While studying the reproductive habits of the Squalius alburnoides, researchers found a single fish (out of 261) that is a perfect genetic copy of its father. S. alburnoides is itself a hybrid of two fish, one of which is now extinct. The results are described in a study published today in Royal Society Open Science.

This is an example of androgenesis, or males reproducing without females. Females reproducing without males, called parthenogenesis, is more common — just look at this terrifying sawfish that managed to do it. For a long time, we thought androgenesis was impossible. It turns out that there are some ants and clams that can do it, but this fish is the most complex animal yet, and the first with vertebrae.

Because the process is so rare, we’re still not really sure how androgenesis happens. It might go something like his: the male produces sperm with twice the amount of genetic content as usual. Then it steals an egg, and somehow eliminates the egg’s genes. Or maybe the sperm is normal, but the genetic material in the egg is missing from the beginning. Or maybe two sperms fertilized an egg with missing genes.

There’s a reason this type of reproduction is uncommon: when you clone yourself, you reduce genetic variation — and that’s risky. If all the animals in a species are genetically very similar, the entire species is vulnerable to being wiped out if something big changes in their environment.

“In a lot of these cases, these bizarre types of reproduction seem to have arisen by two closely related species hybridizing at some point in their evolutionary history and something going really, really wrong with reproduction,” University of Edinburgh evolutionary biologist Laura Ross told The Scientist.

So, maybe this is not the happiest evolutionary origin story, but it is pretty cool that there’s one more animal that can reproduce all on its own.