According to recent research, biofluorescence is relatively widespread among populations of marine fish species. According to the study, which was published in the journal PLOS ONE, the biofluorescent trait could serve a critical role in communication and avoiding detection.
Biofluorescent Fish A Rare Source of Scientific Study
Biofluorescent protein discovery has changed the face of experimental biology. Most fluorescent proteins have been recovered from cnidarians. Derived from the Greek work “cnidos,” meaning stinging nettle, these phenomenally diverse animals inhabit much of the world’s oceans, from the tropics to the poles.
However, recently, researchers have found that fluorescent proteins are phenotypically widespread, and have been observed in cartilaginous and bony fish. It was only very recently, in 2013, that a fluorescent fatty-acid-binding protein was extracted from an eel, by a group of Japanese researchers led by Akiko Kumagai.
Many marine fish dwell in spectrally restricted domains of low light intensity. At great depths, the red, orange, yellow and green components of sunlight are removed. The authors explain that this leaves a very narrow band of blue light, between a wavelength of 470 and 480 nanometers, resulting in an environment that is spectrally restricted when compared to terrestrial environments. Therefore, this presents a novel opportunity for organisms to harness the powers of biofluorescence.
Biofluorescence occurs when an organism absorbs electromagnetic radiation at a specific wavelength and then, subsequently, transforms this energy and emits it at a longer, lower energy wavelength.
The property has been widely reported in scleractinian corals (a.k.a stony corals) – marine creatures that possess a tough skeleton, and are now facing gradual decline. Prior research studies have suggested, in scleractinia, that biofluorescence can aid in providing photoprotection, antioxidation and visual contrast, to name just a few beneficial uses. However, thorough investigation into the function of biofluorescence in fish has yet to be carried out.
The researchers, led by a group of scientists from the American Museum of Natural History, conducted a series of dives using high-intensity blue lighting; in doing so, they collected a variety of specimens from shallow to deep habitats. All collections from the reef dives were digitally imaged, upon return, and scanned for fluorescence. Analysis of these collections was also complemented with field studies of specimens available from the aquarium trade.
The Benefits of Biofluorescence in Marine Fish
Ultimately, the team identified over 180 species of biofluorescent fish from 50 different fish families. Associate Professor of Biology at Baruch College David Gruber, who acted as the study’s co-author, recently explained how his team used specific lighting that mimicked the conditions of the ocean – along with specialist cameras – to gain insight into the “hidden biofluorescent universe.” In a recent press release, Gruber briefly considers some of the potential applications of this visually-striking ability:
“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.”
Fish can absorb light and re-emit it in red, orange and green, releasing light in similar fashion to other organisms within the same habitat, including corals and jellyfish. The study group suggest that, since fish are known to possess yellow lenses or cornea filters – functioning as long pass filters – many populations could achieve enhanced visual perception from biofluorescence, down in the dark depths of the oceans. This camouflage provides the fish with the capacity to avoid predation and, potentially, remain unseen when hunting prey.
The authors contend that biofluorescence could serve a purpose in communication and mating – something that has been previously noted in parrots, for example. In addition, they speculate that the “visual contrast and patterns” of these fish might facilitate a particular species’ ability to remain camouflaged against the reef in shallow, sunlight waters.
Co-lead author John Sparks, an ichthyologist at the American Museum of Natural History, explains that such biofluorescence has previously been witnessed in many terrestrial creatures, including parrots and butterflies. However, reports of this characteristic are relatively sparse in academic literature.
In concluding, the researchers suggest that the fluorescent proteins identified in fish could be used for future biomedical research applications, and speculate that biofluorescent marine fish will become the focus of future research studies.
By James Fenner