Whip Coral Xeno Crab

Xenocarcinus tuberculatus

Kingdom: Animalia
Phylum: Arthropoda
Subphylum: Crustacea
Class: Malacostraca
Order: Decapoda
Family: Epialtidae
Genus: Xenocarcinus
Species: Xenocarcinus tuberculatus

The whip coral xeno crab (Xenocarcinus tuberculatus) is a slender spider crab that lives on sea whips and black corals, matching their colour and banding almost perfectly. Its elongated, pointed carapace is lined with small bumps, and it may be red, orange, yellow or white with pale stripes depending on its host.

Usually only 1-2 cm long, it lies flat along the stem of its whip coral, legs tucked in, so that it looks like part of the coral itself. It feeds on mucus, plankton and particles trapped on the coral, and it rarely leaves its host.

Sea whips on walls and slopes in the Philippines regularly host this little crab. Finding one means slowly following a whip coral from base to tip, often with a torch, and macro photographers prize it for its graphic stripes.

Photo: Dan Schofield, CC BY 4.0, via iNaturalist