Biology
Bioluminescence and Counter-Illumination in Midwater Cephalopods
Quick fact
Many midwater squid and octopus have rows of light-producing organs (photophores) on their undersides that emit light matching the intensity and color of downwelling sunlight, effectively erasing their silhouette from predators below—a strategy called counter-illumination.
Why this is interesting
Cephalopods are masters of disguise—they can change color, texture, and even shape. But in the deep ocean's twilight zone, where sunlight barely reaches, some have evolved an even more astonishing trick: they produce their own light to hide.