Background In the darkness of the ocean, an impressive number of taxa have evolved the
capability to emit light. Many mesopelagic organisms emit a dim ventral glow that matches
with the residual environmental light in order to camouflage themselves (counterillumination
function). Sharks use their luminescence mainly for this purpose. Specific lateral marks have
been observed in Etmopteridae sharks (one of the two known luminous shark families)
suggesting an inter/intraspecific recognition. Conversely, dorsal luminescence patterns are …