Hatchetfish
Depth: 600 m · Twilight Zone
The hatchetfish is thin and silvery like the blade of a hatchet. Along its belly it carries little lights that glow exactly as bright as the light from above. That erases its own shadow and makes it invisible to hunters below.
For scientists
Marine hatchetfish (Sternoptychidae) are masters of counter-illumination: photophores on the belly match the brightness and color of the faint surface light, so no silhouette is left when seen from below. Their upward-pointing tubular eyes scan the brighter sky for the shadows of prey. Their mirror-like flanks reflect side light and dissolve the body outline.
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