Light it up!


 Fireflies have adapted to their nighttime niche through their use of bioluminescence. Males will take flight and emit flashes that vary species to species with respect to color, rate, length, and intensity of light pulse in order to attract a female. 


Organs producing the light are located on the underside of the posterior abdominal segments; more segments are luminous in the male and the light is brighter. Light is produced in a chemical reaction which occurs in the presence of oxygen between the compound luciferan and the enzyme luciferase. There are thousands of specialized cells in the abdomen of the firefly that lights up (lantern) called photocytes. The photocytes make the luciferan and luciferase. Mitochondria surround the photocytes. The nervous system doesn’t directly control the photocytes. The flash triggering nerve impulse goes to non-luminescent cells next to the photocytes. The impulse ends up triggering nitric oxide production. The nitric oxide is what stimulates the light production. It turns on the flash by temporarily stopping the oxygen consumption of the photocyte’s mitochondria. Oxygen can then diffuse farther into the interior of the photocyte, where it triggers the light-producing reaction between luciferan and luciferase. The flash turns off as the nitric oxide is used up and the mitochondria start to consume oxygen again. Learn more on nitric oxide and the control of firefly flashing by Barry A. Trimmer, June R. Aprille, and others by clicking here.

The light of the firefly is not only used for mating purposes, but it is also an aposematic signal. According to Paul R. Mooseman, Jr., Christopher K. Cratsley, and others, “bioluminescence of adult fireflies should indeed be considered in the context of a warning signal against bats, in addition to its relatively well-studied role in courtship.” Bats were used in their study because bats and fireflies are most active at the same time. Some species of firefly are chemically defended so the use of their bioluminescence would be a warning to bats, toads, and other animals. Learn more about their study on aposematic signals to insectivorous bats by clicking here.
In some species of firefly the larvae also glow or emit light. This is also thought to be a warning signal that they taste bad. Click here to learn more about the survival of firefly larvae by Karen Hsu.

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