Pretty Fireflies

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Have you ever wondered how fireflies glow in the dark and why do they glow? They make use of bioluminescence!

Bioluminescence is the ability of living things to emit light. It is found in many marine animals, both invertebrates (e.g., some cnidarians, crustaceans, squid) and vertebrates (some fishes); some terrestrial animals (e.g., fireflies, some centipedes); some fungi and bacteria (photo at left).

Fireflies use their flashes to attract mates or prey. The pattern differs from species to species. In one species, the females sometimes mimic the pattern used by females of another species. When the males of the second species respond to these "femmes fatales", they are eaten!

The firefly is capable of producing a "cold light" containing no ultra violet rays, with a wavelength from 510 to 670 nanometers, pale yellowish or reddish green in color, with a lighting efficiency of 96%.

There are more than 2000 species of firefly, found in temperate and tropical environments around the world. Many species can be found in marshes or in wet, wooded areas where their larvae have more abundant sources of food.

The luminescence involves a luciferin (a light-emitting substrate), a luciferase (an enzyme that catalyzes the reaction), ATP (the source of energy) and molecular oxygen. Generally, the more ATP is available, the brighter the light.

How fireflies turn their luminescent organs — called lanterns — on:

1.The luminescent cells of the lanterns are close to cells at the end of the tracheoles (that bring oxygen to — and take carbon dioxide away from — the insect's tissues).
2. These cells contain nitric oxide synthase (NOS), the enzyme that liberates the gas nitric oxide (NO) from arginine.
3. Nerve impulses activate the release of NO from these cells.
4. The NO diffuses into the lantern cells and inhibits cellular respiration in the mitochondria (probably by blocking the action of cytochrome c oxidase)
5. With cellular respiration inhibited, the oxygen content of the cells increases.
6. This turns on light production in the peroxisomes that contain luciferase and luciferin-ATP (the ATP is generated when the lanterns are dark).
7. The quick decay of NO probably contributes to the short duration of the flash.