Southern Bobtail Squid | Euprymna tasmanica
Bobtail squid have bioluminescent bacteria within their bodies. These glowing bacteria are then used as camouflage by the bobtail squid to mimic the moonlight at night and to eliminate their own shadows, thereby protecting against predators in what is a great example of a symbiotic relationship.
What might be even more impressive is that the bobtail squid can actually control the brightness of the glow caused by the bioluminescent bacteria within them. They have special light organs inside of their mantles that act as filters for the light, allowing them to adjust their glow to match the moonlight.