The scientists, writing in the Proceedings of the National Academy of Sciences, report laboratory experiments strengthen a long-held theory that marine bacteria light up to obtain a free ride to other areas of the ocean in the digestive tracts of larger creatures, ScienceNews.org reported Tuesday.
Numbers of deep-sea species, from bacteria to fish to squid, are bioluminescent, generating light inside their bodies through chemical reactions.
Margarita Zarubin, at the Interuniversity Institute for Marine Sciences in Eilat, Israel, put luminescent bacteria in a tank and watched as smaller animals were attracted to them as a food source, ignoring other bacteria genetically modified to be unable to glow.
When shrimp that were beginning to glow from ingesting the bacteria were presented to predator cardinal fish along with shrimp that were not glowing, the cardinal fish ate only the glowing fish.
When the researchers tested the fish feces they found the bioluminescent bacteria had passed unscathed through the fish guts and come out intact.
The whole process spreads the bacteria through the water faster than they could move on their own, Zarubin said.