Nice Shot! Archerfish Use Complex Process to Turn Water Into Tool

Image: Archerfish target their prey with jets of water they spit from their mouths
Archerfish target their prey with jets of water they spit from their mouths. Ingo Rischawy / Schuster lab, University of Bayreuth

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Asia's zebra-striped archerfish "shoot" their prey with streams of water that they use as a tool, a new study finds. Archerfish aren't the only fish that use tools; the Pacific orange-dotted tuskfish uses rocks to crush clamshells. But archerfish are the only fish known to use adjustable jets of water as tools, according to the new study, published Thursday in the journal Current Biology.

The fish can shoot land-based prey — including insects, spiders and even lizards — off of leaves and branches and into the water from a distance of up to 6.5 feet (2 meters) away. Previous research had found that the fish gather the water between the tongue and the roof of the mouth, forming a gun-barrel-like shape before spitting it out in powerful streams. In the new study, the researchers found that the fish focus the water into a powerful point before impact.

Study researcher Stefan Schuster, an animal physiologist at Germany's University of Bayreuth, and his colleagues trained archerfish to shoot at small black spheres dangling over their tanks, using flies as rewards for a hit. They adjusted the targets so that the fish had to shoot from a distance of 8 inches (20 centimeters), 16 inches (40 cm) and 24 inches (60 cm). The fish managed to focus their jets of water so that a thick slug (like a bullet) formed right before the stream hit the prey. The fish moved their mouths continuously throughout the process, creating a sort of "active nozzle" for shooting water.

— Stephanie Pappas, LiveScience contributor

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