Archer fish shoot water jets with enough force to knock prey.


The water-pistol is a harmless toy for children, but apparently it can be a lethal weapon too. This particular species of fish makes use of water jets and the laws of physics to aim at and stun its prey.

The aptly named archer fish employs a unique process to hunt land based insects and small animals – it aims, spits, and stuns. It lurks under the surface of the water, waiting for unsuspecting insects to land nearby. Then, it spits out water jets at a great force, instantly killing the prey. The entire process takes just one-tenth of a second.

An archer fish can bring down insects as far as three meters above the water’s surface. Once it selects the prey, it rotates its eyes so that the prey’s image falls on a particular part of the eye. Then it presses its tongue against the groove on the roof of its mouth to form a narrow channel, and contracts its gill covers to issue a powerful jet of water through the channel. The power of this shot can be altered for prey of different sizes. The jet can be up to five meters long.

Surprisingly, research has showed that the force of the water that hits the insects is much higher than the force at which it leaves the archerfish. Which means the water gains speed, instead of losing it. This is opposite to how a ball or bullet behaves when it is fired.

For years, scientists believed the archerfish had specialized internal muscles or organs that helped it spit very hard. But thanks to research done by physicists from the University of Milan, we now know that this isn’t the case. In fact, the fish’s forceful strike is formed externally, using water dynamics.

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