Diaphanous Hatchetfish - Sternoptyx diaphana
There are approximately 40 species of marine hatchetfish, all with similar shapes, but varying in size from less than a silver dollar to almost six inches long. The upward-facing (but non-telescopic) eyes and downward-slanting mouth are characteristic of the Sternoptychinae family.
Like many deep-sea creatures, the hatchetfish have bioluminescent photophores on their body - unlike most other deep-sea creatures, though, the hatchetfish directly utilizes their bioluminescence in how they disguise themselves.
The low levels of light that they give off on the bottom half of their body reflect against their silvery scales, giving predators below them the impression that the only thing above is the sky (even if the sky might be thousands of meters above). Complimentary to that camouflage, the upper half of the hatchetfish is more darkly colored, giving predators above the impression that there’s nothing but open ocean below them. This type of camouflage is called “counterillumination”.
Résultats des campagnes scientifiques accomplies sur son yacht par Albert Ier, prince souverain de Monaco. Albert I, Prince of Monaco, 1911.