Look into a cave with a torch and count how many of the animals in it are banded red and white. The shrimp, the squirrelfish, several of the crabs: the same two colors, over and over, in the same place.
It is not coincidence and it is not mimicry. Red is invisible below a few meters, so red pigment is a cheap way to be dark. White breaks the outline into pieces. Put them in bands and you get an animal that, in the dim blue light of a cave mouth, reads as a set of disconnected pale fragments against black rock, which is close to the best result available. Under a torch the same animal is a candy stick, which is a problem for the shrimp and a gift to photographers.
The cave itself is the other half. It is dark, current-fed, predator-poor and permanently available, and the animals that specialize in it converge on the same solutions from completely different families.
This one is a four-centimeter banded shrimp that spends the day deep in the rock and comes out over the reef after dark.
- bold red and white banding along the body and legs
- long white antennae
- deep in caves by day, out on the reef at night
- up to 4 cm
