Their massive globular eyes should have been a clue. It turns out dragonflies have souped-up colour vision that's better than anything ever seen in the animal world.
We humans have what's known as tri-chromatic vision, which means we see colours as a combination of red, blue and green. This is thanks to three different types of light-sensitive proteins in our eyes, called opsins. We are not alone: di-, tri- and tetra-chromatic vision is de rigueur in the animal world, from mammals to birds and insects.
Enter the dragonfly. A study of 12 dragonfly species has found that each one has no fewer than 11, and some a whopping 30, different visual opsins.
Ryo Futahashi of the National Institute of Advanced Industrial Science and Technology in Tsukuba, Japan, also found dragonflies use different opsins at different ages. For instance, the larvae of some species that hatch in sand tend to lack blue opsins. "This is probably because blue light does not reach them easily," he says.
Do all those extra opsins mean dragonflies see the rainbow differently to us? Probably. Other studies have found that dragonflies can see ultraviolet on top of blue, green and red. And it is thought that they can recognise polarised light coming off reflective surfaces like water. "It's likely that they have better colour discrimination than humans," says Futahashi.
Journal reference: PNAS, DOI: 10.1073/pnas.1424670112
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