Biofluorescence, that is, when an organism absorbs light, re-emitting it at a different wavelength (not to be confused with bioluminescence , which is when a living organism produces and emits light), had only been observed in a species of salamander and three species of frogs. However, a new study by researchers Jennifer Lamb and Matthew Davis from St Cloud State University, Minnesota (USA) has shown us that this feature is much more widespread than we thought.
The scientists examined 32 species of amphibians, including salamanders, newts, frogs and caecilians under blue or ultraviolet light, and found that biofluorescence occurred in all of them. And it is likely to occur in many more, as explained by the authors in the study published in the journal Scientific Reports.
Each of the species they analyzed was illuminated in some way, since their skin, muscles, bones and other parts of the body glowed in neon green and orange tones, which showed that it is also common for amphibians to glow in Darkness. They also found the ability present at various stages of life, from tadpoles to adults.
In the past, biofluorescence has been observed in many animals, from jellyfish and corals to sharks and turtles; Normally studies have focused on aquatic animals, but it is clear that amphibians that generally lead a semi-terrestrial life, although always in humid places, are also included in this group of animals with particular qualities. The trait was much less known in land animals, until now.
The researchers were surprised to find even non-colored species in normal light reacting similarly under blue light. It is an example of the Cauca river caecilian, a gray, limbless aquatic amphibian that glowed bright green in blue light.
What practical use can biofluorescence have in animals?
Aside from making them pretty, biofluorescence can also have some practical uses for amphibians. It could help them to locate themselves in low light conditions, creating more contrast between amphibians and their environment – since their eyes contain rod cells that are sensitive to green or blue light – to serve as a camouflage tool, to imitate the appearance of predators or even to mate, depending on the situation, scientists have explained.
“One of the most exciting aspects of this work was that with each species we examined we were always discovering something new that could bring new insights into the life history and biology of amphibians around the world,” Lamb said. “The eastern tiger salamander ( Ambystoma tigrinum) was the first species of salamander we studied for biofluorescence, and when we saw the bright, intense green light emitted by its yellow spots, each of us let out an expression of collective surprise! “.
How do they get biofluorescence?
The findings suggest that this happens through various mechanisms thanks to the presence of fluorescent proteins in the skin, secretions such as mucous membranes, minerals in the bones or even in the urine. Some of the amphibians also have chromatophores, or cells that contain pigment and reflect light.
Referencia: Salamanders and other amphibians are aglow with biofluorescence, Scientific Reports (2020). DOI: 10.1038/s41598-020-59528-9 , https://www.nature.com/articles/s41598-020-59528-9
