Evolution seems to know no bounds when it comes to shaping organisms in a way that's meant to help them survive and reproduce — a process that often leads to some pretty bizarre characteristics and behaviors. And now, thanks to the work of biologists Niclas Kolm and Göran Arnqvist, we can add another example to the list.

In a classic and literal case of bait-and-switch, male swordtail characins, a small fish found in Trinidad and Venezuela, use their tasty-looking ant-shaped appendages to lure and then mate with females.


Ed Yong writes in Discover Magazine:

The male characin has a small bean-shaped patch attached to his gill flaps by a thin thread. When he swims, he holds these ‘flags' against his body. When he encounters a female, he flares one of them out in front of her. The female clearly thinks that the flag is food, for she bites at it vigorously. While she's occupied, the male sidles across and impregnates her with his sperm.

Unlike many other fish, which shoot sperm and eggs into the water, characins fertilise each other internally, just like us. The male, however, doesn't have any sort of penetrating organ, so he needs to bump into the female just so. And his bizarre ornament ensures that she's in exactly the right place.


Ed Yong has a lot more to say about this discovery, including its significance for evolution and speciation — so read the whole thing. You'll also want to read the study, which was published in Current Biology.

Image courtesy Discover Magazine.