Zebra Urchin Crab

(Zebrida adamsii)

Zebra Urchin Crab (Zebrida adamsii)

Images taken at Lembeh, and Ambon, Indonesia

• Smooth surface with minimal spines compared with many pilumnid crabs.

• Carapace wider than long.

2. Distinctive Zebra Color Pattern

• Bold alternating dark brown/black and white transverse bands across the carapace and legs.

• The striping continues across chelipeds and walking legs, giving the species its common name.

• This pattern also provides camouflage among sea urchin spines.

3. Specialized Walking Legs

• Long, slender pereiopods adapted for moving between urchin spines.

• Terminal segments have curved dactyli with gripping ability to hold onto spines.

4. Chelipeds (Claws)

• Relatively small claws compared with many crabs.

• Symmetrical and smooth with fine setae.

• Used primarily for feeding on mucus, debris, or parasites on the host urchin.

5. Body Flattening

• The crab is slightly dorsoventrally flattened, allowing it to move through dense urchin spines without being dislodged.

6. Eye and Orbital Features

• Well-developed eye stalks.

• Eye orbits relatively shallow and not heavily armed with spines.

7. Habitat

One of the most useful identification clues is its obligate association with sea urchins, particularly:

• Diadema setosum

• Diadema savignyi

The crab usually sits between the spines or near the oral surface of the urchin.