By SHUNSUKE KIMURA/ Staff Writer
January 18, 2021 at 15:55 JST
A genij-botaru firefly (Shunsuke Kimura)
Researchers have shed new light on the color of the glow that fireflies gave off about 100 million years ago by re-creating the luminescent enzyme from one the species possess today.
The beetles glowed a dark green during the Cretaceous Period, compared with a range of colors from yellow to green emitted by their modern-day counterparts, according to a study by researchers at Chubu University, Nagahama Institute of Bio-Science and Technology and other institutions.
“We were able to re-create a colorful sight that has disappeared for a long time,” a researcher said.
About 2,200 species of fireflies are believed to exist today, and they all have the same substance called luciferin that makes them glow. But the color of the light ranges from yellow to green because each species has a different amino acid sequence of luciferase, a luminescent enzyme that numbers some 550 amino acids.
Lampyridae, a family of beetles to which fireflies belong, is thought to have been able to glow since it first appeared on Earth during the Cretaceous Period, about 100 million years ago, according to the research team.
In the study, the researchers applied a method called “ancestral sequence reconstruction” to determine how the amino acid sequence of fireflies' luciferase changed over time by using genetic information of the enzyme that about 30 modern species have. They successfully traced the amino acid sequence back to the one from some 100 million years ago.
The researchers then reproduced luciferase the ancestral firefly had and mixed it with luciferin. The chemical reaction caused the substance to glow a dark green. They said they were able to re-create the luminescence color with a 93.5 percent accuracy, according to their calculation.
Fireflies also have toxins and the greenish light they emit is considered a warning to predators. The species is believed to have evolved to glow in various colors as the emission of light also became a means of communication between males and females.
“Fireflies began emitting different colors as they diverged from the species that glows a dark green,” said Yuichi Oba, a professor of bioluminescence at Chubu University. “Further studies may reveal how their light emission evolved.”
The study was published in the U.S. scientific journal Science Advances: (https://advances.sciencemag.org/content/6/49/eabc5705).
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