Bioluminescence in Squid

Bioluminescence is a fairly common characteristic among squid and cuttlefish. In fact, 63 out of the 100 genres contain species with this capability. Light production in cephalopods can be either autogenic, produced intrinsically by the organism itself, or bacteriogenic, produced extrinsically by bacterial symbionts. It is possible for a species to display one or both of these types of luminescence, depending on their physiology. Three main sources of luminescence exist among squid:

photophores

symbiotic bacteria

Bioluminescent secretions