In the deep sea the chance of finding a mate is much reduced due to the dark conditions and vast open spaces. Bioluminescence can aid in an organisms plight to find a partner maintaining a stable population of these deep water species. Bellow are a few species that employ different methods in order to attract a mate:-
Anglerfish are a classic example of sexual dimorphism. The females are large and have a bioluminescent esca which appears to be used as a lure for both prey and males alike. The males on the other hand have no lure and are small with large eyes relative to their body size (Young 1983). It is likely that the male is drawn to the female by the lure although it has been suggested that chemical cues may also be used (Bertelsen, 1951).
Leachia pacifica is a species of cranchiid squid that also displays sexual dimorphism (Young 1975). At sexual maturity a photogenic organ will develop at the tip of the third arm of the females. She will then dive down to depths of over 1200m followed by the males. The female can control the light emitted by a flap which has the ability to cover the light organ. It is assumed that a male is attracted by the patterns of light the females produce (Young 1983).
Ostracods of the genera Vargula attract a mate based on bright courtship signals of luminescence being squirted into the water (Herring 2000). Each male has a can be uniquely identified by the frequency and timing of the release of the fluid (Morin 1986). The females linger below the display until she has picked out a male, at which point she will swim up to meet him and copulation will occur (Herring 2000).
Vertical migrations occur in Odontosyllis enopla (Fischer & Fischer 1995). It is during these migrations, that the females will swarm and secrete a luminescent slime to attract the males and signal that they are ready to release their eggs. The position of the moon will determine when this swarming will occur. The males will then gather around the females and release their sperm, producing short flashes as they gather (Fischer & Fischer 1995).