Dragonflies see the world in a way beyond human limits. Scientists discovered that these insects can detect extremely deep red light, even edging into near-infrared, as a result of a specialized visual protein strikingly similar to the one found in human eyes.
This ability likely helps them spot mates mid-flight by picking up subtle differences in reflected light.
About 3,000 extant species of dragonflies are known. Most are tropical, with fewer species in temperate regions. Adult dragonflies are characterised by a pair of large, multifaceted, compound eyes, two pairs of strong, transparent wings.
An adult dragonfly’s compound eyes have nearly 24,000 ommatidia each. The compound eyes of insects are composed of units called ommatidia. An ommatidium contains a cluster of photoreceptor cells surrounded by support cells and pigment cells.
Within these cells there is a specific protein called opsin. This responds to light at around 720 nm. This wavelength lies beyond the deepest red that humans can normally see.
The human eye contains opsins too. Human vision relies on these proteins in the eye to perceive different colours. There are three main types, each tuned to blue, green, or red wavelengths, which together enable full colour vision.
Why Deep Red Vision Matters for Dragonflies
Scientists from Osaka Metropolitan University proposed that this heightened sensitivity helps dragonflies find mates. To explore this idea, they examined reflectance, which refers to how much light a surface reflects. In Gomphidae dragonflies, reflected light plays a key role in how individuals appear to one another.
Their measurements revealed clear differences between males and females in how they reflect red to near-infrared light. This suggests that males may rely on these subtle visual cues to quickly identify females while flying.
Future Medical Application?
The scientists also uncovered a key detail that could make this discovery useful in technology and medicine. They identified a single position in the opsin protein that determines how it responds to light. By modifying this position, they were able to shift the protein’s sensitivity further toward longer wavelengths, bringing it closer to the infrared range.
The researchers proceeded to engineer a version of the protein that reacts to even longer wavelengths and demonstrated that cells containing this modified opsin can be activated by near-infrared light.
This work could be valuable in optogenetics, a field that uses light-sensitive proteins to control and study cells in living tissue. As longer wavelengths of light can penetrate deeper into the body, a protein that responds to near-infrared light could allow researchers to reach cells that are otherwise difficult to access.
The research appears in the journal Cellular and Molecular Life Sciences, titled “Dragonfly red opsins share a common tuning mechanism with mammalian red opsins and further enhancement of near-infrared sensitivity.”
