It is difficult to believe that other organisms do not perceive the world as we see it. As humans, we are able to see just a narrow band of all the electromagnetic radiation that arrives to the Earth from the Sun. We can see within the so-called “visible spectrum”, i.e. the human visible spectrum (400-700 nm). However, many other animals, including birds and insects, can perceive other wavelengths out of the human visible spectrum. The ultraviolet radiation (with wavelengths below 300 nm) is one of the most interesting, perhaps because we are not able to perceive it. Many birds and most insects can see ultraviolet, and they can use it for finding food or communicate to other individuals.
Dragon- and damselflies, as most of the insects, can see ultraviolet and even near infrared. Interestingly enough, recent studies have shown that dragonflies show one of the largest diversification of opsin genes, which code for proteins involve in colour vision. Using eye electrophysiology, we can study and estimate the sensitivity peaks of animal eyes. The extracellular recording, or electroretinogram, is a very easy procedure which, however, requires large doses of patience and accuracy.
The method consists on introducing an electrode on the animal eye. When the eye is stimulated with the right wavelength, the membrane of the eye photoreceptor depolarises, and the change in the membrane potential is recorded by the electrode. The signal goes now through an amplifier, a noise eliminator and an oscilloscope, letting us to record the signal. If we stimulate the eye with different wavelengths, for example, covering from the ultraviolet till the near infrared, we are able to record how responsive the eye is along the desired light spectrum.
I did this in eyes of the damselflies Calopteryx splendens and Calopteryx virgo, as part of a study on visual ecology of predator-prey systems. I found four sensitivity peaks, one for ultraviolet, one for blue, one for green, and a potential fourth one for red (Fig. 1). However, there were no differences between the species, the sexes, or the dorsal and ventral part of the eye. With this new information, I am now able to model how the damselfly eyes perceive their own body and wing colorations.
Wanna know more??? http://onlinelibrary.wiley.com/doi/10.1111/1365-2435.12769/abstract