This fish shoots insects off leaves and corrects for light bending
Archerfish knock insects off overhanging plants with a jet of water spat from a grooved mouth, reaching prey up to about 3 metres above the surface. Adults nearly always hit on the first try, even though light bends as it crosses from air into water and distorts where the target seems to be.
The family, Toxotidae, is small: ten species split between two genera, Toxotes and Protoxotes, the second revived in a 2022 study because of its deep genetic split from the first. Most live in freshwater streams, ponds and wetlands, though two or three tolerate the brackish water of estuaries and mangroves. They turn up across a broad arc of warm waters, with northern Australia and India near its two ends. They are deep-bodied and flattened from side to side, usually around 12 to 18 centimetres long, although the largescale archerfish can reach 40. Their closest relatives turn out to be the beachsalmons, whose mouths have similar internal features.
The weapon is plumbing rather than muscle alone. The fish turns its eye so the prey's image lands on a specific patch of the retina, pushes its lips just to the surface, and presses its tongue against a groove in the roof of its mouth to form a narrow tube. Snapping the gill covers shut forces water through. The stream is shaped so that its tail moves faster than its head, and the trailing water catches up to form a heavy blob just before impact; the fish adjusts that timing to the distance. Because it both uses and shapes the water, it counts among the few tool-making animals. Shots average about 74 degrees from horizontal but stay accurate anywhere from 45 to 110.
Skill has to be learned. Juveniles begin firing at about 2.5 centimetres long and miss a lot, so they hunt in small schools, raising the chance that someone scores. A 2006 experiment suggested that archerfish improve simply by watching a skilled shooter, which would mean translating another fish's angle and distance into their own. They also change how they shoot when rivals are in view, probably because another archerfish might steal the prize.
They are opportunists too, leaping to snatch insects within reach and firing jets into silt to flush out buried prey. Whether aerial or underwater shooting came first is unknown; the two may have evolved together, an example of exaptation. A fossil species from Eocene rocks in Sumatra looks almost modern apart from an extra dorsal spine or two.
Source: Archerfish
