New research shows that bioluminescence—a phenomenon in which organisms generate visible light through a chemical reaction—evolved many more times among marine fishes, and likely throughout the entire tree of life, than previously thought. In a study published in the journal PLOS ONE today, scientists from the American Museum of Natural History, St. Cloud State University, and the University of Kansas reveal that bioluminescence evolved 27 times in marine ray-finned fishes—and 29 times if sharks and rays are counted.
“Our findings completely change how we look at the evolution of bioluminescence across all life,” said John Sparks, curator-in-charge of the Museum’s Department of Ichthyology and a co-author of the paper, which is the first to explore how frequently bioluminescence evolved in vertebrates. “This suggests that we need to take a closer look at the evolution and diversification of other lineages with bioluminescent members.”
Most people are familiar with bioluminescence in fireflies, but the phenomenon is also found in bacteria, fungi, and in organisms throughout the ocean, where at certain depths, nearly all living things glow. One anglerfish species even has two ways to shine: glowing bacteria live in its lure, while the fish produce light from a chin barbel using their own chemical cocktail. It has generally been hypothesized that bioluminescence evolved independently about 40 times across the entire tree of life, but this new study suggests that is likely a drastic underestimate.
Different species use these biological lights in a variety of ways, including camouflage, communication, and hunting. The stoplight loosejaw, pictured above, has both red and blue/green light-producing organs, known as photophores, under its eyes. The shrimp that make up most of its diet cannot detect red light, so the loosejaw uses this “private” wavelength of light to hunt them without being seen.
The researchers also found that several inshore and deep-sea bioluminescent fish lineages that use bioluminescence for communication, feeding, and reproduction tend to be very species-rich. This finding suggests that bioluminescence may facilitate diversification, especially in the deep open ocean, a region without obvious barriers to reproduction.
The scientists are now are trying to identify specific genes associated with the production of bioluminescence in fish.