[ Watch the Video: Strange Lights In The Deep, Dark Ocean? ]
Brett Smith for redOrbit.com – Your Universe Online
A new study in the journal PLOS ONE has revealed biofluorescence in over 180 fish species and opened the door to the discovery of new fluorescent proteins that could be used in biomedical research. When organisms biofluoresce, they absorb light, convert it, and send it back out as a different color.
“We’ve long known about biofluorescence underwater in organisms like corals, jellyfish, and even in land animals like butterflies and parrots, but fish biofluorescence has been reported in only a few research publications,” said study author John Sparks, a curator in the American Museum of Natural History’s Department of Ichthyology. “This paper is the first to look at the wide distribution of biofluorescence across fishes, and it opens up a number of new research areas.”
Most fish inhabit a world that is colored in various shades of dark blue, as deeper and deeper water absorbs more and more visible light in the other parts of the spectrum. Recently, researchers have found that many fish absorb these small amounts of dark blue light and re-emit it in neon colors.
The study team said their work was inspired by observations of a green eel fluorescing off of Little Cayman Island in the Caribbean Sea. To further explore this phenomenon, the researchers conducted four nighttime expeditions near the Bahamas and the Solomon Islands. During their dives, the team stimulated biofluorescence in the fish using high-intensity blue lights. Because the resulting biofluorescence was invisible to the human eye, the researchers used customized underwater cameras that allowed them to see the fish glow while swimming on the reef.
“By designing scientific lighting that mimics the ocean’s light along with cameras that can capture the animals’ fluorescent light, we can now catch a glimpse of this hidden biofluorescent universe,” said study author David Gruber, a research associate at the American Museum of Natural History. “Many shallow reef inhabitants and fish have the capabilities to detect fluorescent light and may be using biofluorescence in similar fashions to how animals use bioluminescence, such as to find mates and to camouflage.”
The most recent expedition, conducted from the research vessel Alucia, involved the scientists performing technical scuba dives and sending a three-person submersible vessel down nearly 3,300 feet.
The team discovered a menagerie of biofluorescent fish, particularly among irregular patterned, well-camouflaged species living in and among the coral reefs. The study team was able to identify over 180 species of biofluorescent fish, including species-specific patterns among close relatives. The researchers also discovered that many of these fish species have yellow filters in their eyes, which could allow them to see the fluorescent displays that are normally invisible.
The study team suggested that the fluorescence could be used to allow communication between individuals within a species while staying camouflaged to predators. This would be particularly important during full moons, when some species have a tendency to mate.
“The cryptically patterned gobies, flatfishes, eels, and scorpionfishes—these are animals that you’d never normally see during a dive,” Sparks said. “To our eyes, they blend right into their environment. But to a fish that has a yellow intraocular filter, they must stick out like a sore thumb.”
The study team noted that additional investigation could eventually yield new florescent proteins for a range of scientific uses.
“The discovery of green fluorescent protein in a hydrozoan jellyfish in the 1960s has provided a revolutionary tool for modern biologists, transforming our study of everything from the AIDS virus to the workings of the brain,” Gruber said. “This study suggests that fish biofluorescence might be another rich reservoir of new fluorescent proteins.”