Zebra Urchin Crab

Zebrida adamsii

Kingdom: Animalia
Phylum: Arthropoda
Subphylum: Crustacea
Class: Malacostraca
Order: Decapoda
Family: Pilumnidae
Genus: Zebrida
Species: Zebrida adamsii

The zebra urchin crab (Zebrida adamsii) is a striking little crab with bold zebra-like stripes that lives among the spines of sea urchins. Its stripes, usually brown or purple on white, run in the same direction as the urchin's spines, helping it blend in.

It reaches about 1-2 cm across and has a flattened carapace with pointed edges. Clinging to its host with hooked legs, it grazes on the urchin's tissue and spines, often leaving a bare patch where it sits. It usually lives on fire urchins and other sea urchins, sometimes with a mate.

The zebra urchin crab is a favourite muck-diving find in the Philippines, where guides check urchins on the sand for it. Because its hosts can be venomous, it is best photographed without getting too close.

Photo: Kai Squires, CC BY 4.0, via iNaturalist