The Archer Fish: A Wonder of Creation
The archer fish (Toxotidae jaculatrix, from ejaculator fish) –– named due to its expert archery skills–– is one of the most amazing types of fish known to humans (Smith, 1936). When first researched by scientists in the 1920s, researchers “could hardly believe their eyes” at its shooting ability (Pinney, 1977, p. 3). The existence of the fish was actually first reported by explorers in 1764, but scholars could not accept the reports of the existence of this amazing fish (Lüling, 1963, p. 100).
These seven-inch long fish are most well-known for accurately knocking insect prey out of overhanging vegetation with a jet of water six times more powerful than the fish’s muscles. To achieve their feat they must first position themselves in the water with their snout just breaking the water surface, leaving their eyes just below the surface. They then aim their jet spray by the use of their superbly designed binocular vision to accurately determine their prey’s location.
If one eye is damaged, their aiming skill is lost. The archer fish modulate their water jet’s velocity to create a single large water drop that strikes their prey with enormous force. This design avoids the requirement for specially designed internal structures to store large amounts of energy.
How the Water Gun Works
The water shot is produced by the fish compressing its hard bony tongue against the roof of its mouth, forcing water out the gun-barrel-like groove in the archer fish’s mouth roof by rapidly snapping their gill covers shut (Pinney, 1977, pp. 2-3). It usually accurately strikes its target on the first attempt at distances of up to 2 to 3 feet! To position itself to hit its target the fish is a versatile swimmer—it can even swim up and down and backwards to position itself to make its line of vision line up with its prey (Pinney, 1977, p. 3).
So complex was its design that the mechanism the archer fish uses to produce its water jet had been researched for decades. In 2011 scientists finally largely determined how it works (Vailati and Cerbino, 2012). They now know that a large amplification of the fishes’ muscular power occurs outside of the fish to cause a very powerful impact of the water jet with the prey. Alberto Vailati and his University of Milan colleagues have provided the first scientific explanation for how archer fish are able to generate such powerful jets to capture their prey. To study the mechanics of the water jet, the authors used high-speed video recordings of archer fish knocking insects out of plants.
They found that archer fish generate this power externally using water dynamics rather than by specialized internal organs. Some animals, such as chameleons and salamanders, store energy in their body’s collagen fibers and abruptly release their stored energy to project their tongues outward at high speeds. Previous research on archer fish have ruled out the use of these specialized organs as the source behind their powerful water jets.
Excellent vision in its typical muddy water environment is also critical to hit its target. To achieve this vision the archer’s eye retina is far more complex than that of most fish. The cones for daytime vision number only 8 or 9, but the rods for vision in muddy water, where they normally live, number a whopping 217. The archer fish vision ability is such that they can extinguish cigarettes with their water jet in total darkness! The archer fish must also solve the refraction problem, the bending of the light rays that occurs as the light rays enter the water, causing objects to appear where they are not. It achieves this feat with remarkable accuracy (Myers, 1952).
Practice Makes Perfect
As the young fish develop, they begin practicing on targets above the water in their natural habitat (Brodie, 2006, p. 218). The tiny fish first succeed in squirting their jet only a few inches high. As they mature they learn to shoot a stream of water as far as fifteen feet! Adult archer fish normally shoot down their insect prey at a range of less than a meter.
To strike its moving target, the fish must compensate for the target’s (the insect’s) speed and the changing angle between the fish and its target to determine the refracted level (how much the light is bent at the air-water boundary). They also must compensate for the effect of gravity on both the fish and the water stream (Brodie, 2006, p. 218).
These variables require computing a set of calculations that are done by human mathematicians using calculus. Research has also determined that archer fish learn to make these calculations by observing skilled fish practice their art. All of this is done by a “primitive cerebrum” which researchers have discovered is not primitive at all! (Brodie, 2006, p. 218).
The Problem of Archer Fish Evolution
If the archer fish gradually evolved its remarkable ability, it must have done so because it has helped their survival. Yet not one other fish that swims side-by-side with the archer, and also feed on the bottom in the water or on the surface, has also evolved this ability. Nor are any intermediates known. All fish either possess the compete set of biological systems to shoot insects out of the air, or lack the entire set.
Another major problem with the evolution explanation is that archer fish most often feed on insects it finds on or just below the water surface. It can even jump clear above the surface to take insects on the wing. It can also feed on insects that sink a few inches into the water (Schuster, et al., 2006). For this reason it does not need to shoot insects out of the air to survive, and can survive quite well without ever doing so. In fact, most of its food is usually obtained without ever using its water gun. It appears its archery ability is exercised mostly for sport or variety! Archer fish expert, Professor Lüling, recognized this problem writing: “Taxotes depends largely on food it finds on or below the [water’s] surface. It prefers insects that have fallen to the surface, but it will also take food that has sunk a few inches into the water. This raises an interesting question for evolutionary theory: Spouting, if it is so unimportant, can hardly have been a significant factor in the survival of the species or in selection and differentiation within the species.” (1963, p. 100)
Consequently, natural section cannot account for their amazing ability. Nor can evolution account for the unique ability of this marvelous little fish! Although normally existing in the waters of Australia and Southeast Asia, because of their unusual skill they are a popular attraction in aquariums throughout the world.
Brodie, Chris. 2006. “Watch and Learn: Benchwarming Pays Off for the Archer Fish.” American Scientist, 94(3):218.
Lüling, K. H. 1963. “The Archer Fish.” Scientific American, 209(1): 100-109. July.
Myers, George S. 1952. “How the Shooting Apparatus of the Archer Fish Was Discovered.” The Aquarium Journal, 23(10): 210-214; October.
Pinney, Roy. 1977. “The Amazing Archer Fish.” Scholastic Science World, 34(4): 2-3, October.
Schuster, Stefan, Saskia Wöhl, Markus Griebsch, and Ina Klostermeier. 2006. “Animal Cognition: How Archer Fish Learn to Down Rapidly Moving Targets.” Current Biology, 16:378-383, February 21.
Smith, Hugh M. 1936. “The Archer Fish.” Natural History, 38(1):2-11; June.
Vailati A, Zinnato L, Cerbino R. 2012. “How Archer Fish Achieve a Powerful Impact: Hydrodynamic Instability of a Pulsed Jet in Toxotes jaculatrix.” PLoS ONE 7(10): e47867.
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