A new study published in the Cell Press journal Current Biology this week describes how archerfish are more adaptable and skillful target-shooters than previously believed.
Researchers have known for a while now that the fish hunts by shooting jets of water at insects, spiders, and even small lizards. But now they can confirm archerfish also use water as a tool, making them the first known tool-using animal to change the hydrodynamic properties of a free jet of water, according to a Cell Press news release.
"The predominant impression from our field work in Thailand over several years is that there is very little to actually shoot at, so it's important for the fish to be efficient," says Stefan Schuster of the University of Bayreuth in Germany, according to the release. "It pays to be able to powerfully hit prey over a wide range of distances."
Schuster and Peggy Gerullis were able to make the discovery by training fish to hit different targets that ranged from 20 to 60 centimeters from a precise location.
The duo then monitored different aspects of jet production and propagation as the fish showed what they could do.
The studies helped reveal that the time needed before water masses up at the jet tip isn't fixed. Instead, archerfish make adjustments to make sure that a nice drop of water forms right before impact.
Archerfish achieve this by modulating the dynamics of changes in the cross-section of their mouth opening, according to the release. Timing adjustments that the fish must make to hit their targets are comparable to the "uniquely human" ability of powerful throwing, according to the release.
"One of the last strongholds of human uniqueness is our ability to powerfully throw stones or spears at distant targets," Schuster says. "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."
There is a chance that the mechanism the fish uses to control water with such precision could also find application in human-built nozzles, Schuster said, mentioning that adjustable jets are big business in a number of industries, like medicine, according to the release.
"The biggest problem is how to modify the abrasive properties of a jet," Schuster said. "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."
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