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The Invisible Glow: An Illuminating Look at the World of Biofluorescence

In 2015, a remarkable discovery was made by divers off the coast of the Solomon Islands. Although it wasn’t a new species, something novel–and peculiar–was learned about an existing one, the hawksbill sea turtle: that its shell reflected blue light in a way that reflected a beautiful, kaleidoscopic array of neon reds and greens.

The ability to reflect light in this manner is different from bioluminescence, where certain animals can produce a natural illumination of their own, either chemically or by other means. Creatures like the hawksbill sea turtle rely on a different, and equally unique mechanism of nature called biofluorescence that allows the reflection of certain kinds of light in remarkable ways. Several other species also do this, ranging from varieties of deep ocean fish and sharks, to certain crustaceans, corals, and even scorpions.

A scorpion fluoresces under blue light (Wikimedia Commons).

In fact, more than 180 different species are known to possess bioflourescence, the latest among them being puffins. The discovery was made by Jamie Dunning, a Ph.D. student at the University of Nottingham, whose discovery was shared with existing data (previously unreported) from professor Tony Diamond at the University of New Brunswick, Canada. Diamond noticed the same unique characteristic on puffin beaks years earlier, National Geographic reports.

In 2014, a study by the American Museum of Natural History (AMNH) that appeared in PLOS One detailed the dozens of known varieties of fish that possess bioflourescence, which at that time had only been discovered in invertebrates and other less mobile aquatic species.

The Chain catshark’s biofluorescence becomes visible under blue light.

According to John Sparks, co-author and a curator of the AMNH’s Department of Ichthyology:

“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. 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.”

Bioflourescence may not appear to be as exciting as animals that actually produce light themselves, although what it tells us about the way our world looks to non-human species is just as important. For instance, certain varieties of ocean fish possess natural yellow filters that allow their eyes to block blue light. This causes certain types of bioflourescent ocean animals to glow, and thus be more readily apparent.

The world of many ocean fish, in other words, is probably far colorful and illuminating than it would be to the human eye.

Bioflourescence is, of course, just one way that various species see the world very differently from humans. Our beloved cats and dogs populating neighborhoods throughout the world are capable of night vision that far exceeds what humans are able to see. Many other animals that have evolved to exist and function nocturnally also possess increased night vision, which involves the presence of naturally occurring reflector systems in the eyes of nocturnal species called tapetum lucidum. This allows retinal cells that are sensitive to light an increased degree of photoreception conducive to seeing in low-light settings.

In either case, the world as humans see it is far from different from that of many of our animal kindred; it only serves as a reminder to the varying perspectives, and beautiful diversity, this planet has to offer… at least to those willing (or able) to see it!


Micah Hanks is a writer, podcaster, and researcher whose interests cover a variety of subjects. His areas of focus include history, science, philosophy, current events, cultural studies, technology, unexplained phenomena, and ways the future of humankind may be influenced by science and innovation in the coming decades. In addition to writing, Micah hosts the Middle Theory and Gralien Report podcasts.
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