Two centimeters. Put it on a coin and it does not reach the edge.
There is a floor under how small a fish can get, and it is set by physics rather than by ambition. Eyes need a minimum number of cells to resolve anything, gills need enough surface for a body whose oxygen demand rises as it shrinks, and a brain, a gut and a set of gonads all have to fit. Below about eight millimeters almost nothing works, and the world's smallest fish sit right on that line. At two centimeters this one is not a record holder, but it is deep into the range where being a vertebrate stops being straightforward.
What it gets in return is a habitat with no competition and almost no predators: the interior of the reef, the cracks and voids inside rubble and coral rock, which is a three-dimensional maze that nothing larger can enter. Most of the fish species on a reef live in there rather than on it, and most of them are never seen.
This one is coffee brown, which is what the name cappuccino refers to, it lives in this sea and nowhere else, and it was described only in the last twenty years.
- two centimeters long, one of the smallest fish in this catalogue
- coffee brown, which is what the species name refers to
- inside crevices and rubble, never in the open
- found in the Red Sea and nowhere else
Why it's threatened
Threats to this species are currently unknown.
Threat classification from the IUCN Red List.
