Counter-illumination
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Counter-illumination is a method of active camouflage seen in marine animals such as firefly squid and midshipman fish, and in military prototypes, producing light to match their backgrounds in both brightness and wavelength.
Counter-illuminating photophores illuminating the underside of the hatchetfish Argyropelecus olfersii
Photophores on a lanternfish, the most common deep sea fish worldwide
Photophores on a nocturnal midshipman fish, whose bioluminescence halves its rate of predation
Diffused lighting camouflage prototype, not quite complete and set to maximum brightness, installed on HMS Largs in 1942
Firefly squid
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The firefly squid, also commonly known as the sparkling enope squid or hotaru-ika in Japan, is a species of squid in the family Enoploteuthidae. W. scintillans is the sole species in the monotypic genus Watasenia.
Diagram illustrating the basic features of a generic squid. The mantle, eyes, arms, tentacles, buccal membrane, and typical suckers are all shown in this diagram.
Boiled firefly squid, as served at a restaurant. Firefly squid are caught in bulk during spawning on the shores of Japan and are offered in many restaurants and grocery stores.