Look into a living Pocillopora head and you will usually find them: one male and one female snapping shrimp, and alongside them a pair of small crabs. They are not lodgers. They are the reason the coral is still standing.
When a crown-of-thorns starfish climbs onto a coral that has its guards, the crabs go for its tube feet and spines while the shrimp snaps at it, and the starfish gives up and moves to an easier colony. Work on Pacific reefs during outbreaks found guarded Pocillopora colonies surviving while unguarded ones a meter away were stripped to bare skeleton. The shrimp gets shelter and a share of the coral's mucus; the coral gets a standing army of four.
The pair holds one colony and defends it against other shrimp of its own kind as fiercely as against the starfish. They can live ten years in there, which for an animal under three centimeters long is a remarkable run, and it is the same coral for most of it.
- lives deep inside branching Pocillopora, in a male and female pair
- translucent body under reddish-brown mottling
- one claw enlarged into a snapping claw, the other small
- a coral head with shrimp in it clicks continuously
- up to 2.7 cm
