Like the guy who slings darts in the pub, archerfish aren't exactly known for having great aim. But these fish are remarkable at what they do – blasting insect prey from the sky or off a perch with a jet of water. "They have a really cool ability to hit these distant aerial targets," says Jessica Techet, an associate professor at the University of Illinois who studies the fish.
Techet and her colleagues have now uncovered how the fish do it. They observed the fish in a tank seeded with tiny particles that were illuminated by laser light, visible only in near-infrared. High-speed video revealed that the fish spotted the particles and used their body motions to calculate the speed and direction of the falling prey. The fish then determined how to spit at the target based on its estimated movement in midair.
The researchers found that the predictive C-start decisions were driven exclusively by information sampled during the initial movements of dislodged prey, not from any other a priori cues (Fig. 1). The resulting accuracy was comparable to that achieved by halfbeaks when they are competing with each other for the same prey.
Unlike sharks and dolphins, which generate their jumping power by swimming up from the depths, the archerfish uses their tail to create acceleration in midair. This allows them to hit their targets with astonishing accuracy over a wide range of speeds and directions from the starting point of their leap, Techet notes in a Feb. 21 article in the journal Current Biology.