THE SWIMMING WATER PISTOL
THE SWIMMING WATER PISTOL
Image source: By Ltshears - Own work, CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=6610377
2. Archer fishes occur from India to the Philippines and northern Australia.
3. Can live in pure sea water to pure fresh water.
4. The archerfish’s coloring can vary, but they are typically silvery with 6 or 7 black spots or vertical bands of varying size lining their sides. The bands help camouflage the fish in the shadows of mangrove vegetation.
5. They have narrow, knife-shaped bodies and are flat at the top. Their mouths are large and point upwards. This is ideal for hunting at the surface of the water.
6. Male and female archerfish look the same.
7. The archerfish has a long groove along the top of its mouth. When it presses its tongue against the roof of its mouth and compresses (squeezes together) its gill covers, it can propel water at its target, sometimes as far as 5 feet away.
8. They have large eyes located very close to their mouths, giving them very good binocular vision (using both eyes at the same time). Studies have shown that they are able to judge distances and the angle of light refraction (bending of light) very accurately.
9. Archerfish travel in groups called shoals. A shoal is similar to a school of fish, except a school moves in a coordinated fashion, and a shoal is a group that remains together for social reasons or for hunting.
10. Because of the position and construction of their eyes, archerfish can see in 3 dimensions. They can also adjust their aim to account for the distortion (change in the usual shape) that happens when they look at an insect outside of the water. They learn that there is less distortion when they are directly below their prey, and tend to position themselves accordingly.
11. "Toxotes", the genus name, is Greek for archer; "jaculatrix", the species name, is Latin for a female javelin thrower.
12. The WWII Submarine USS Archerfish was named after this sharp shooting fish.
13. In Singapore’s Kew Gardens, archerfish are kept in ponds of water lilies to keep down the insect population.
Image source: By Pearson Scott Foresman - Archives of Pearson Scott Foresman, donated to the Wikimedia Foundation→This
file has been extracted from another file: PSF A-50002.png, Public Domain,
15. When an archer fish locates a prey sitting on a leaf or flying low over the water, it may try to shoot it down with a drop of water by spitting at great speed. An adult can spit up to about three metres and hit a fly more than a metre away -quite impressive for a fish that rarely reaches 20 centimetres in length.
16. The secret to the Archer fish's success is that it lines up its sight with the prey from a position directly underneath the prey. From this vantage point, light from the prey travels directly to the fish's eye without undergoing a change in direction. Since the light is traveling along the normal to the surface, it does not refract; the light passes straight through the water to the fish's eyes.
17. But as the Archer fish sights along the normal, there is no refraction and no visual distortion of the image. From this ideal position, the Archer fish is able to hit its prey time after time. The secret of the Archer fish is to use its understanding of the physics of refraction of light. The Archer fish knows that refraction is less when sighting along the normal. Now that's physics for better living. Like all fish, the Archer fish has spent its life living in schools; and there's no better place than a school to learn about the physics of refraction.