doi:10.1038/nindia.2010.88 Published online 30 June 2010
The brilliant flashes of light from the abdomen of a firefly have been a source of inspiration for poets and scientists alike throughout history. The almost lossless chemical reactions involved in firefly chemoluminescence, traditionally studied by biochemists, have recently attracted the attention of physicists.
Now, two Indian scientists from the Department of Electronics and Communication Technology at the University of Gauhati in Assam have discovered that the flashes become a continuous glow when the insect is anaesthetized.
Anurup Gohain and Subhash Rajbongshi demonstrated this by forcing the firefly Luciola praeusta Kiesenwetter to inhale ethyl acetate vapour, and found that within minutes the flashes turned to a constant glow. Time-resolved experiments showed that this continuous light was actually composed of a train of tiny pulses, each lasting for around two microseconds.
"The existence of pulses within the apparent 'd.c.' light comes as a big surprise," say the researchers. The nature of the pulses suggests that an oscillatory chemical reaction continues at the microsecond timescale in the abdominal lantern of the anaesthetized firefly. The researchers propose that ethyl acetate inhibits the respiration of mitochondria, thereby ensuring a continuous oxygen supply to the luciferin-containing organelles.
"Thus, the oscillating chemical reaction goes on uninterrupted while the firefly is in an unconscious state," they say. However, further work is required to determine the mechanism of this chemoluminescent reaction.