Synopsis

How Oxygen Kindles Fireflies

Physics 7, s147
X-ray images of the light-emitting organs in fireflies clarify the mechanism by which oxygen controls the insects’ luminescence.

To communicate and find mates, fireflies produce light flashes through a luminescence process whose chemistry is well known: in the presence of oxygen, an enzyme acts on the compound luciferin (Latin for “light-bringer”), triggering an oxidation reaction that is accompanied by light emission. Determining the mechanism that regulates the oxygen supply has been difficult because the tracheal network that carries the gas to the light-emitting organs, known as photocites, has features as small as 100 nanometers (nm), finer than the resolving power of most microscopes. Now, Yeukuang Hwu at the Academia Sinica and the National Cheng Kung University, Taiwan, and co-workers have used tomographic and microscopy techniques with 20-nm resolution to image the insects’ organs and derive oxygen flux estimates that support a specific supply mechanism.

The researchers designed their experiment to test two leading hypothesis for the oxygen supply mechanism. The first revolves around the firefly’s production of nitric oxide (NO) inside the photocites: before a flash, the gas soaks the mitochondria—organelles that, fed by oxygen, control energy production in cells— suppressing their activity and leaving extra oxygen available for bioluminescence. The second conjecture proposes that circulating fluid in the tracheal network rises or ebbs to control oxygen. The authors’ experiments, carried out at Taiwan’s synchrotron light source, provided evidence for the first theory: x-ray images of the tracheal system in live insects showed no fluid inside the tracheal system. By measuring the tracheal geometries with high resolution, the researchers were able to estimate how much gas could diffuse from the tracheal network to tissues, yielding values consistent with the NO hypothesis.

This research is published in Physical Review Letters.

–Matteo Rini


Subject Areas

Biological Physics

Related Articles

A Less Invasive Approach to Rheology Measurements
Biological Physics

A Less Invasive Approach to Rheology Measurements

Researchers have demonstrated a method of probing a soft material’s properties that could allow them to capture those properties more accurately and for smaller systems than current methods. Read More »

Bacteria That Shove Harder, Move Further
Biological Physics

Bacteria That Shove Harder, Move Further

Simulations show that the harder bacteria in a swarm push against one another, the more likely they are to go on long “walks.” Read More »

Discrete or Continuum? It Matters for Cells
Statistical Physics

Discrete or Continuum? It Matters for Cells

A new model shows that the properties of waves produced in a cell-signaling process strongly depend on whether the cells are considered to be discrete entities or a collective mass. Read More »

More Articles