Archerfish are capable of shooting a stream of water with great accuracy, and new research shows how the animal accomplishes the task. Jets of water shoot from the mouths of archerfish, aimed toward their intended prey.
Researchers discovered archerfish use the streams of water as tools during the hunt. By sticking their mouths barely above the surface of the water, the fish can shoot jets at insects of small lizards sitting on limbs and branches above the water. Prey can be targeted by the fish, from a distance of over six feet.
Biologists have long known that archerfish form a barrel between the roof of their mouth and tongue in order to produce the jets. This new research reveals the animals modulate the streams in order to focus the water into a slug shape just before impact. This could suggest significant brain power is utilized in properly shaping the aquatic blast.
"One of the last strongholds of human uniqueness is our ability to powerfully throw stones or spears at distant targets. 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," Stefan Schuster of the University of Bayreuth in Germany, said.
Other fish are also known to use tools in the wild. These include the Pacific orange-dotted turkfish, which crushes shells of clams using rocks. This is the first time a fish has been known to use streams of water as a tool. They are the only animal known to change the nature of freely-flowing streams of water.
In the study, the animals were trained to fire jets of water at black spheres at distances greater than those previously studied. Three sets of targets were set up at eight, 16 and 24 inches away from the animal. The fish were provided with treats of black flies for each successful strike. Researchers discovered that shots meant to travel greater distances were expelled over longer periods of time than when the target was closer. The amount of time water was expelled from the mouth of the fish for an additional 3.4 milliseconds for every 3.9 feet of distance.
Archerfish also continually adapt the shape of their mouths, creating a unique active nozzle that could be an inspiration for water jet cutters and other industrial equipment.
Photo analysis of the shots showed the streams focusing into a bullet-like shape that added to the force of initial impact on the target.
Archerfish, and their use of water jets was detailed in the journal Current Biology.
