Originating in Central Africa, Peters' elephantnose fish (Gnathonemus petersii), finds its bearings by means of weak electrical fields. Scientists from the University of Bonn have now been able to show how well this works. In complete darkness the animals can even distinguish the material of objects at a distance or dead organisms from living ones. The results have now been published in the Journal of Experimental Biology.
The fish, which is as long as a cigar, hovers with its head inclined, close to the gravel-covered bed. While it swims forward slowly, its trunk-like elongated chin sweeps steadily from right to left, always at a distance of a few millimetres from the bottom. This way the fish behaves like treasure hunters searching for buried gold coins on the beach with their metal detector. Basically, this is precisely what the fish is doing. Hidden in the sediment there are large numbers of dead nematocera larvae waiting for it, its favourite food.
Zoologists from the University of Bonn have hidden the larvae there. 'We wanted to see whether it can find them and if the answer is yes, then down to what depth,' Professor Gerhard von der Emde explains. 'It', that is the African Peters' elephantnose fish. Yet its characteristically shaped chin does not work like a particularly sensitive nose. Instead, it contains more than 500 electric sensors with which it senses its surroundings. With this sense the animal has conquered the night. During the day it hides, only under cover of darkness does it goes searching for food.
The chin of Peters' elephantnose fish is basically its eye. In its tail is the corresponding torch. Via mutated muscle cells it produces regular electrical pulses of a few volts with it. 80 times per second the fish switches this little battery on and off for the blink of an eye. 'At the same time it measures the electrical field which builds up around it via sensors in the skin,' explains Professor von der Emde. Nearby
|Contact: Professor Gerhard von der Emde|
University of Bonn