In the seas around Indonesia lives an unusual fish, the Great Sunda Chameleon Fish. The fish is named after the Great Sunda islands, which include Borneo, Sumatra, and Java. As the reader can judge from the name, this fish can change its colour at will to fit in with its surroundings. However, this is only half the story…
The chameleon fish is a solitary fish and doesn’t usually swim in shoals. A fully grown adult is about twenty inches long with a girth of roughly eight inches, at least that’s the size when it’s in the natural state. If the chameleon fish feels threatened or wants to swim with other fish for a while, it can puff itself up to twice its natural girth and add around 3 – 4 inches to its length, by allowing sea water into some naturally spongy chambers along its body.
By behaving this way, the chameleon fish can assume the colour and size of about 50 other species of fish in the surrounding seas, all of them much larger and more imposing than the Chameleon Fish. The fish can maintain this disguise for up to eight hours, before they have to revert to their normal size. If a chameleon fish is caught by fishermen, it will change colour every two minutes, something which alarms the people of the area, who invariably believe the fish is the devil’s work and will throw it back into the sea.
Extract from Animals Evolution Forgot