Countershading is a form of concealing coloration in which the upper surfaces of the body are more darkly pigmented than the unilluminated lower areas, giving the body a more uniform darkness and a lack of depth relief.
Another clue can lead to the recognition of an organism: its three-dimensional form, which causes the unilluminated portion of the body to be in shadow. Countershading is a form of coloration in which the upper surfaces of the body are more darkly pigmented than the unilluminated lower areas, giving the body a more uniform darkness and a lack of depth relief. Widespread among vertebrates, countershading is frequently superimposed over camouflage and disruptive colorations.
The light-producing organs, or photophores, of many deepwater fishes provide a unique form of countershading. Photophores occur in bands along the lower parts of the sides and are directed downward. Deepwater fishes live in the twilight zone of the sea, in which the illumination is too weak to allow little more than a silhouette of prospective prey sighted by a predator from below. The downward-projecting photophores may provide countershading by obliterating the silhouette when it is viewed by a predator from below.
Credit : Britannica
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