“In the well-illuminated terrestrial and shallow water environments visual signals play a very important part in sexual recognition, attraction and mate selection.” (Herring 2007)
It does not take much to realise that in the deep-sea, where no ambient light penetrates, visual aids to sexual selection could not work without the use of point bioluminescence. It is thought that bioluminescence for sexual communication is the only time dimorphism can occur within a species. The simplest dimorphism would be the bioluminescence of the ovaries in females but not the testes in males (Herring 2007). Some copepods have shown glandular dimorphism with the smaller males showing decreased numbers of glands with some reports of a differing pattern and distribution of these glands too (Herring 2007).
The ostracod Vargula species, and other members of the genus, have very elaborate bioluminescent courtship displays. These are based on repeated puffs of luminescence into the water. The males can be identified by the frequency and timing of these puffs (Herring 2000).