Bioluminescence in Noctiluca is caused by a luciferin-luciferase reaction. Luciferin is a light-emitting molecule, while luciferase is an enzyme that catalyzes the oxidation of luciferin, resulting in the emission of light. This reaction takes place within specialized structures called scintillons or photocytes present in the cytoplasm of Noctiluca cells.

When a Noctiluca cell is stimulated by physical disturbances, such as waves, mechanical agitation, or even the movement of nearby organisms, it triggers the luciferin-luciferase reaction. The specific mechanism of this stimulation is not fully understood, but it involves changes in the cellular environment that cause calcium ions (Ca2+) to increase in concentration.

The increased Ca2+ levels activate the luciferase enzyme, which then catalyzes the oxidation of luciferin to produce light. The emitted light has a characteristic blue-green color and is visible at night, giving Noctiluca its bioluminescent glow.

It's worth noting that while the exact biochemical details may differ slightly among different Noctiluca species, the overall process of bioluminescence involving a luciferin-luciferase reaction remains consistent.