Many creatures in the sea glow in the depths of the deepest trenches of the oceans. Bioluminescence is even observed in some marine bacteria, which emit a steady light once they have attained a certain level of concentration of organic particles in ocean waters, which is known as quorum sensing.
In a new article published in the journal Proceedings of the National Academy of Sciences (PNAS), researchers at the Hebrew University of Jerusalem discovered that light emitted by the bacteria attracts predators, generally zooplankton, which ingest the bacteria but are unable to digest them. The bacteria continue to grow inside the zooplankton, which are then attacked by their own predators, fish, which can easily spot the glowing zooplankton.
In the laboratory, nocturnal fish easily ingested glowing plankton, while they were not attracted to the zooplankton which had undergone genetic mutations to prevent the glowing.
The bacteria even survived the passage through the fish. Once they reach the digestive system, the marine bacteria have reached their goal, since it’s full of nutrients.
The phenomenon of quorum sensing that regulates the bacterial bioluminescence explains that zooplankton realize that the light in the water indicates the presence of a rich source of organic material, material on which the bacteria grow. The zooplankton take the risk of becoming glowing themselves, since food is rare and exposing themselves to the relatively rare presence of predatory fish is worthwhile.
Reference: “Bacterial bioluminescence as a lure for marine zooplankton and fish” by Margarita Zarubin, Shimshon Belkin, Michael Ionescu and Amatzia Genin, 27 December 2011, Proceedings of the National Academy of Sciences.