Living Supersoakers: Archerfish Spit Water to Kill Prey

Asia's zebra-striped archerfish are the animal world's living supersoakers, spitting water at their prey with remarkable power and precision, a new study describes.

The aptly-named archerfish can shoot down unsuspecting prey - some as far away as 6.5 feet (2 meters) - off their leafy perches simply using subtle shifts in the position of their mouths. According to the study, published in the journal Current Biology, they are the only fish known to use adjustable jets of water as tools.

Researchers at the University of Beyreuth, Germany say that it's the force and accuracy of these kill shots that are the key to an archerfish's success. The fish have "very little to shoot at," researcher Stefan Schuster said in a press release. "It pays to be able to powerfully hit prey over a wide range of distances."

Schuster and his colleague, Peggy Gerullis, recorded nine trained archerfish to squirt water at targets between 8 inches and 2 feet away. The target training sessions revealed that the time needed before water accumulates at the jet tip isn't fixed. Rather, archerfish "make adjustments to ensure that a nice drop of water forms just before impact," the researchers reported.

Previous research had found that the fish gather the water between the tongue and the roof of the mouth, forming a shape like that of a fun barrel. This new study shows that archerfish tweak this technique by changing the cross-section of their mouth opening to form a more precise jet of water - a talent that would presumably require a lot of brain power.

"One of the last strongholds of human uniqueness is our ability to powerfully throw stones or spears at distant targets," Schuster explained. "This is really an impressive capability and requires - among many fascinating aspects - precise time control of movement. It is believed that this ability has forced our brains to become bigger, housing many more neurons to afford the precision. With the many neurons around, they could be used for other tasks apart from applying them for powerful throws. It is remarkable that the same line of reasoning could also be applied to archerfish."

These target shooters may inspire improved adjustable jets, which are used in many industries, but the biggest problem with that, Schuster says, "is how to modify the abrasive properties of a jet. Usually this is done by modulating the release pressure or by varying the abrasives added to the jet. We are not aware of someone actually using a dynamically adjustable valve."