The fish that can sense electric colours

"“I don't want to be human ! I want to see gamma rays, I want to hear X-rays, and... and I want to smell dark matter !"

With their electro-sense they can estimate distances, distinguish forms and materials, differentiate between dead and living objects. And more than that: Within fractions of a second, they can recognize whether mosquito larvae, their favourite food, are hiding in the gravel or sand at the bottom of their habitat. They can do this with considerable accuracy, largely ignoring the larvae of other insects.

Living organisms... also modify the shape of the electric pulses. But even this signal change depends on distance, size and position. The combination of the two signal characteristics could solve these problems. The human eye works in a similar fashion: Its retina contains receptors for red, green and blue light. Our brain then uses the "mixing ratio" to calculate the colour of the object we see. And this remains largely constant, no matter how large or far away the object in question is.

It is clear that the animals have two different types of electric receptors. One only measures the intensity of the signal, the other additionally measures its shape. "We have now been able to demonstrate that the fish uses the relation between these two measurements to identify their prey," explains Prof. Dr. Gerhard von der Emde, who led the study.