Archer fish are fast head computers

Decision on the strategy for quarrying takes 40 milliseconds

With a sophisticated hunting technique, the shooter fish capture their food. © Volker Runkel, Schuster Laboratory, University of Erlangen-Nuremberg
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Tropical shooter fish are known as skilled hunters. They shoot their prey with a targeted jet of water, which they can shoot at high pressure over distances of up to two meters. However, to feed them, the fish have to make a number of highly complex decisions - a process that, according to a new study, takes place in a surprisingly small network of nerve cells in the brain. The biologists report on their experiments in the current issue of the science journal Science.

If riflemen hit their feed animals with a stream, the killed insect falls into the water and is easy prey for its hunter. But the competition does not sleep: To prevent other fish from chasing the prey, the shooter must predict as accurately as possible, at which point his food will hit the water surface, and drive it at lightning speed. The shooter fish make this decision in just a few moments - on average 40 milliseconds.

Shot angle and position of the prey unimportant

Information such as the angle of the shot or the position of the prey before the launch is of no importance for the calculations, say the zoologists Stefan Schuster and Thomas Schlegel of the University of Erlangen-Nuremberg. The fish are based solely on the movement of insects in the case. This is shown by experiments of the Erlangen scientists, in which, among other things, the fish could only see their food when it fell into the water.

First calculations already on the retina?

Even if two prey objects started at the same time, the fish quickly decided for the one to which they had to travel a shorter distance. The shooter fish always responded with equal speed to their prey. Based on these results, Schuster and Schlegel assume that this process takes place in a very small neural circuit, the first calculations may even take place on the retina.

(idw - University Erlangen-Nürnberg, 21.01.2008 - DLO) Display