The West Atlantic Hoary Rubble Crab, Banareia palmeri, Behaves Like a Corallivore

Various photographs of the West Atlantic hoary rubble crab, Banareia palmeri (Rathbun, 1894), published on the internet show individuals being perched on branching octocorals. This habitat relationship has not been given attention in the scientific literature. The crab belongs to the brachyuran decapod family Xanthidae, which includes other species that associate with corals and zoantharians. Other aspects of the biology of B. palmeri, such as its diet, are unknown. During a night dive in Bonaire, an individual of B. palmeri was observed cutting off the tip of a sea rod, Pseudoplexaura sp., and pulling the loose fragment to its hiding place. The crab has also been observed in association with other octocoral species, such as Gorgonia ventalina Linnaeus, 1758. Close examination of the crab’s claws revealed that the inner edges resemble saws by bearing tooth-like structures with sharp edges, which explains how this animal is able to cut through the coral’s soft tissue and horny axis. These findings suggest that the crab is an expert in clipping octocoral branches, which may explain why some sea rod branches can be observed missing their original rounded tips and have regenerated pointy ends instead. Considering the octocoral’s regeneration capacity, it would be relevant to study how fast these branch tips are able to heal and whether fragments escaping from the crab’s claws are able to survive. Future examination of the crab’s gut contents and aquarium experiments may be able to provide more information about its dietary preferences.