Our retinas contain four different types of light-sensing photoreceptor cells: rods, which detect low levels of light, and three cone cell types which detect red, blue and green wavelengths of light. These allow us to see in (relative) black and white when it’s dark, and in vibrant colour when it’s lighter. The wavelengths that different animals can see varies quite considerably, and this broadly depends on how many different opsins (a light-reactive protein found across the animal kingdom) are expressed from the animal’s genome which detect different wavelengths of light. Humans and most primates have three, birds usually have four, and some snakes have just two. However, it was recently discovered by Ryo Futahashi and colleagues that some species of dragonflies have up to 33 different opsin genes in their genomes! While this doesn’t necessarily mean they can see 33 different colours, having spare copies of some of the genes might allow for evolutionary innovations and changes to these, without risking losing their colour vision to mutations. This discovery puts dragonflies on a level footing with Stomatopods (mantis shrimps) which have between 15 and 33 opsin genes and are widely regarded as the most complex eyes in the animal world.
Image: Lauren Sumner-Rooney