Bioluminescence for Countershading

The squid nurtures the bacteria to use the light they produce to countershade—a form of camouflage—against moonlight. The squid hunt at night and countershading hides them from their prey and perhaps predators.

A glowing Bobtail squid is camouflaged against moonlight. A view below the squid looking up to the moonlight. The looping animation fades between the non-glowing squid's dark silhouette against the moonlight and the glowing squid blending in with its surroundings.