A look at the trending polka-dot tree frog that’s been catching everybody’s eyes with its newly discovered bright blue and green glow!

There has been a lot of talk about a fascinating frog as of late. A fluorescent frog, in fact! Scientists are excited, and science news sites like Nature and Chemistry World have covered this excitement. So much mystery! So many questions! Why has the polka-dot tree frog (Hypsiboas punctatus) attracted such a grand amount of attention, though? The answer lies in the biochemistry behind the amphibian’s glow.

The mysteries of the fluorescent trait

Fluorescence in animals isn’t a new topic but is a rarity. It’s not surprising zoologists aren’t carrying around a black-light wherever their job takes them. However, during a recent study, Carlos Taboada and his team did and found that the polka-dot tree frog glowed a bright blue-green. In the study, they weren’t expecting this color. The frogs produce biliverdin, a chemical that, when bound to a certain protein, fluoresces a faint red (1). The real culprits behind the frog’s glow are molecules previously only found in certain plants.

This is a first in the animal world. Other fluorescent animals use proteins or polyenic chains as fluorophores, per Maria Gabriela Lagorio. At this point, no one is sure why these creatures glow beyond speculation. Perhaps it’s for communication. Maybe it’s camouflage. It could be a trait meant to attract mates. Many agree that this recent discovery could reveal the secrets behind why these animals evolved this way. This also means that more questions have been brought up than answered.

One such question is how the frog fluoresces. The frog is responsible for “18−29% of the total emerging light under twilight and nocturnal scenarios,” the abstract of the study says (2). It’s already been found that H. punctatus uses a compound structure, previously known only to be in plants, to glow. On top of that, it’s not a protein or polyenic chain like other fluorescent animals. The main compound contributing to its ‘light’ is called Hyloin-L1, two other contributors called Hyloin-L2 and Hyloin-G1 (3). Because of the structure of the compound, isoquinoline, the glow is visible to the human eye Andrew Beeby says. The question is how did the little amphibian evolve differently than other known fluorescent animals?

The backstory of isoquinolines

Isoquinoline alkaloids play a significant role in our society. They can be used in many ways, from aesthetic to medical. Morphine, for example, is commonly known isoquinoline.  They can also be used as antibacterial, antimalarial, and anti-HIV components (4). Isoquinolines are also known to be used in pesticides, dyes, and paints. A certain isoquinoline-structured compound has been found to be a neurotoxin linked to Parkinson’s disease. Understanding this family of compounds could not only help us find answers for the current phenomena of the polka-dot tree frog but also aid humans.

Compounds that are found in plants that are isoquinoline-based prove to be of use as well. Berberine is one example which is useful for treating heart failure. Plants that produce isoquinolines create them through biosynthesis, a natural process, unlike many compounds we currently use. Luckily, we don’t exclusively use synthetic processes but rather use the plants themselves for medicine.

Understanding why and when it evolved like this could help us do numerous things. For one, considering the fluorophore H. punctatus uses could help human life since many isoquinolines have proven beneficial in various ways. There will be many studies put into play to find the secrets behind fluorescent animals. Already, scientists are planning to consider many, many more frogs to see if they glow and if so what is the cause behind it. Maybe biochemists and other researchers will find that the isoquinolines behind the polka-dot tree frogs fluorescence could be useful in medicine and create a way to synthesize the compounds.

To conclude…

What is clear is that this discovery is huge for not just the researchers and news outlets, but the general population of animal and science lovers! There could be so much more we can speculate on right now because of the fluorescent polka-dot tree frog than only what we can see with a black-light. The discovery of how the frog fluoresces could lead to more understanding about fluorescent animals. Researchers now speculate that the fluorescence of H. punctatus contributes to their vision; perhaps some of the already known animals utilize it for the same reason? Don’t forget about what possibilities may arise from research of the isoquinolines the frog produces. It’ll be fascinating to see what scientists find out next and what sort of secrets they will unearth.

Cover image coming soon.

Bibliography

  • (1) Nowogrodzki, Anna. “First fluorescent frog found.” com 13 March 2017: 297. News Article. 13 March 2017. <http://www.nature.com&gt; .
  • (2) Taboada, Carlos, et al. “Naturally occurring fluorescence in frogs.” Proceedings of the National Academy of Sciences of the United Sates (2017). Academic Journal. 13 March 2017. <http://www.pnas.org&gt; .
  • (3) King, Anthony. Fluorescent frog first down to new molecule. 13 March 2017. Royal Society of Chemistry. News article. 14 March 2017. <https://www.chemistryworld.com&gt; .
  • (4) Shi, Jun. Isoquinoline Alkaloids. Presentation. La Jolla, CA, and Jupiter, FL: The Scripps Research Institute, 2006. PDF Document.
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