Flat Rock Crab

Percnon planissimum

The Flat Rock Crab, a member of the Percnidae family, inhabits the tropical Indo-Pacific region, extending from Somalia to the Cocos Islands, the Philippines, and the Kermadec Islands. Divers are likely to encounter this species in shallow reef environments, as it is typically found at depths ranging from 1 to 6 meters. Its presence is often noted in reef-associated habitats, where it blends into the rocky substrate. This species is part of the order Decapoda, known for their distinct mating behaviors. The Flat Rock Crab engages in a precopulatory courtship ritual, utilizing olfactory and tactile cues for indirect sperm transfer. Divers encountering the Flat Rock Crab should be cautious, as it is noted to be poisonous if eaten. However, it poses no threat to divers observing it in its natural habitat. The species has not been evaluated for conservation status by the IUCN, leaving its population trends and threats largely unknown.