Bombadier Beetle

Fantasy Fact: Dragons breathed fire.

Scientific Inspiration: Many animals produce light. The chemical light produced by bioluminescence is found in many marine animals — jellyfish, comb-jellies, fish, crustaceans, bacteria, and others. Light is produced to search for prey or to lure them within reach, to hide from predators, or deter or confuse them, for navigation, and to find a mate. Bioluminescence on land is less common, but glowworms and fireflies (actually a species of beetle) are familiar.

Bioluminescence is "cold light," or light that is efficiently produced by biochemical processes without heat production. No actual animal, apart from man, uses fire. The nearest is the bombardier beetle (Brachinus). This animal has evolved a remarkable defensive system: it emits a rapid burst of scalding, irritating chemicals in the face of its attacker.

The process is complex. Cells in the tip of the beetle's abdomen produce hydrogen peroxide (H2O2) and substances called hydroquinones, which are stored in a reservoir. This reservoir is connected to a thick-walled reaction chamber by a valve, controlled by a sphincter muscle. The reaction chamber is lined with cells that secrete enzymes. When the reactive mixture of hydrogen peroxide and hydroquinones is passed into the reaction chamber, the enzymes break down the H2O2, releasing copious free oxygen, and catalyzing the oxidation of the hydroquinones. The reaction generates enough heat to bring the volatile mixture to boiling point and vaporizes much of it. This greatly increases the pressure within the reaction vessel, forcing the valve shut (preventing backfires) and expelling the mixture explosively through openings in the tip of the abdomen.