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Born to shine

Firefly: light-flashing requires less energy than flying

ART FARMER / WIKIMEDIA COMMONSFirefly: light-flashing requires less energy than flyingART FARMER / WIKIMEDIA COMMONS

Fireflies need a lot more energy to fly than to light up their abdomens. Researchers in Taiwan and Switzerland used X-ray microscopy and high-resolution tomography to map out and generate a three-dimensional view of the network of microscopic, branching tubes (tracheoles) that make up the respiratory system of these insects. Then, they measured oxygen consumption, an indicator of energy expenditure, each time that individual fireflies from two species – Luciola terminalis and L. cerata – were stimulated to flash their lights. A firefly’s twinkle expends less energy than other activities, such as flying, which burns up 140 times more oxygen. The amount of oxygen consumed for light-flashing was only 37% higher than when the insects were at rest (Physical Review Letters, in press). According to the researchers, this low consumption of oxygen is a result of how tracheoles are structured around a firefly’s special light-emitting cells (photocytes). The tracheoles are optimized to generate maximum light using the least possible amount of oxygen. “Our study generated an important side-product: evidence that firefly abdomens are optimized for light-flashing,” the researchers wrote. “The rate of oxygen diffusion from the tracheoles is similar to the rate of oxygen consumption in bioluminescence.”