 Counter @-@ illumination means producing light to match a background that is brighter than an animal 's body or military vehicle ; it is a form of active camouflage . It is notably used by some species of squid , such as the firefly squid and the midwater squid . The latter has light @-@ producing organs ( photophores ) scattered all over its underside ; these create a sparkling glow that prevents the animal from appearing as a dark shape when seen from below . Counterillumination camouflage is the likely function of the bioluminescence of many marine organisms , though light is also produced to attract or to detect prey and for signalling . 
