New Hypothesis Links Firefly Bioluminescence to Oxygen Levels

A genomic analysis disproved the popular theory regarding the origin of firefly lights. Many species of beetles in the Lampyridae family, commonly known as fireflies, have been proposed to emit bright lights that formerly served as a warning to predators about the toxicity of fireflies before being repurposed as a mating signal.

This would also explain the glowing of eggs, larvae, and pupae. Ying Zhen and associates challenged conventional knowledge by creating a firefly family tree and tracking the development of lucibufagins, the chemical compounds that give fireflies their toxic nature. In addition to two related species, the team collected new samples of 16 different Lampyridae species from various locations throughout China. These samples were analyzed in conjunction with previously collected specimens and genetic data.

The authors assembled genomic-level data from 41 species. Using liquid chromatography-mass spectrometry, they also searched for lucibufagins for each species. The researchers were able to demonstrate that while bioluminescence is widespread throughout the entire family of fireflies, lucibufagins are restricted to a single subfamily. This finding strongly suggests that the toxin evolved after the development of bioluminescence.

What then caused fireflies to start glowing? It has previously been demonstrated that luciferin, the bioluminescence substrate of fireflies, possesses antioxidant qualities. Researchers led by Ying Zhen discovered that the evolution and diversification of firefly ancestors occurred during a historical period when atmospheric oxygen levels were rising from a historical low following the Toarcian Oceanic Anoxic Event.

The authors also point out that bioluminescence in glowing millipedes is believed to have first evolved to cope with oxidative stress in hot, dry environments, and the authors speculate that fireflies may have taken a similar evolutionary route.