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Midwater Squid, Abralia veranyi

A photo of a squid using bioluminescence to hide in the deep sea.
E. Widder, ORCA, www.teamorca.org

Glowing photophores are visible on this midwater squid (Abralia veranyi) viewed from below at low light levels. We think of light as a way to see in the dark. But many species use it to help them hide. This adaptation is called counterillumination. Seen from below, an animal might stand out as a dark shape against the brighter water above. By glowing on its underside, it can blend in. Watch a video of scientists describing their encounters with bioluminescent animals in the deep sea