A red fish in a cave is a black fish. That is not a figure of speech: it is what the water does to light.
Water absorbs the long wavelengths first. Red is gone by about five meters, orange by ten, yellow by twenty, and what is left below that is blue-green. A red animal has no red light to reflect, so it goes dark gray, then black, and disappears into the shadow it is sitting in. Put a torch on it and the color jumps back instantly, which is why these caves look completely different on a photograph than they do to the eye.
So red is one of the cheapest ways for a small fish to be invisible in dim water, and reef caves are full of red animals for exactly that reason: this dottyback, the soldierfish and squirrelfish above it, the shrimps under the ledge below.
This one is under five centimeters, with a red-orange head shading into a darker body, and it lives in the 🌊 Red Sea and nowhere else. You will almost certainly find it with a light rather than by eye.
The genus. Chlidichthys Smith 1953 - ichthys (fish). ETYFish
The species. Chlidichthys rubiceps Lubbock 1975 - ruber (red) + ceps (head). ETYFish
- red-orange head grading into a darker body
- tiny, under 5 cm
- inside caves and under overhangs, rarely in the open
- up to 4.5 cm
Why it's threatened
Threats to this species are currently unknown.
Threat classification from the IUCN Red List.
