Bandit Coral Crab

Tetralia nigrolineata

Kingdom: Animalia
Phylum: Arthropoda
Subphylum: Crustacea
Class: Malacostraca
Order: Decapoda
Family: Tetraliidae
Genus: Tetralia
Species: Tetralia nigrolineata

The bandit coral crab (Tetralia nigrolineata) is a tiny guard crab with a dark 'bandit mask' band across its front, living in branching Acropora corals. Its smooth, rounded body is usually pale cream or tan, edged with a thin black line.

It measures only about 1 cm across and lives in pairs deep within its host coral. Like other coral guard crabs, it feeds on coral mucus and in return defends the colony from coral-eating predators, pinching at their tube feet or soft parts.

Branching Acropora on reef flats and slopes in the Philippines is where this crab lives. It stays hidden deep in the branches, so a torch and some patience are needed to spot its distinctive masked face.

Photo: Borja Fierro-Leva, CC BY 4.0, via iNaturalist