Bioluminescence has only been observed in three classes of mollusks: Cephalopoda, Gastropoda, and Bivalvia. Bioluminescence is widely spread among cephalopods, but much rarer among the other classes of mollusk. Most species of biolumenescent mollusk that have been discovered are found in the ocean with the exception of the genera Latia and Quantula found in freshwater and terrestrial habitats respectively; however, more recent research has discovered luminescence in the Phuphania genus. It is hypothesized that terrestrial mollusks that use bioluminescence developed it as a strategy to deter predation. The green color emanated by the mollusk's photocytes is thought to be the most visible color to nocturnal predators.