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Cyclodius ungulatus
H. Milne Edwards, 1834

Hoof-Clawed Reef Crab

Joshua Gaschk (2014)


Fact Sheet



Physical Description


Life History & Behaviour

Anatomy & Physiology

Evolution & Systematics

Biogeographic Distribution

Conservation & Threats

References & Links



Cyclodius ungulatus is an exosymbiont of corals relying on them for protection against predation and in turn provide a cleaning service for their hosts (Stella et al. 2014).They are often observed living and grazing on hard corals confirming some sort of symbiotic relationship however any specific coral preference is unknown due to lack of research. Because the chelae ends of C. ungulatus are flat and hoof-like in structure with a large gap between the closed propodus and dactyl it could be hypothesised that the claw isn’t used in the defence of the crab or the host coral but purely for cleaning and feeding purposes. Corals like Pocillopora damicornis and P. verrucosa that were studied by Chang et al. in 1987, for their mutualistic relationships with crab species, would be ideal as the hard structure of the stony corals provide great protection. Though it is possible for this crab to share in this symbiotic relationship with corals, it can often be found rummaging amongst coral debris, rocky rubble or in fouling communities. The innate defences of the Hoof-clawed reef crab, their rubble-like camouflage and toxicity, suggest this is a natural habitat though their presence could be due to eviction from host corals (Stella et al.2014; Llewellyn and Endean 1988).