Jacforus xuxian sp. nov., a new species of xanthid crab (Brachyura, Xanthidae) from the coral reefs of the South China Sea, and its potential symbiotic relationship with Ophionereis porrecta (Echinodermata, Ophiuroidea)

Abstract A new species of the family Xanthidae MacLeay, 1838, has been discovered in the coral reefs of the Xisha Islands, South China Sea. Jacforus xuxian sp. nov. can be distinguished from the previously sole species of the genus, J. cavatus (Rathbun, 1907), by its broader and flatter carapace, rounded anterolateral lobes, and slender and sinuous G1. All specimens of the new species were found co-occurring with the brittle star Ophionereis porrecta . Three out of the four specimens were specifically located sharing narrow burrows with individual O. porrecta , which may suggest a newly discovered symbiotic relationship.