Infrequently studied coral species are seldom mentioned as host organisms of associated fauna. Here we report on the stony coralAgaricia tenuifoliaDana, 1848 hosting a gall crab (Cryptochiridae) for the first time. This coral-dwelling crab was observed at the southern coast of Bonaire in the Dutch Caribbean. Based on the shape of the dwelling, and the host specificity of cryptochirids, the crab is tentatively identified asOpecarcinus hypostegus (Shaw & Hopkins, 1977).
In order to demonstrate how scleractinian corals contribute to marine biodiversity by their host function, information on associated fauna was gathered during a biological survey at St. Eustatius, eastern Caribbean. This knowledge is especially urgent for a host coral such as Helioseris cucullata (Agariciidae), which has undergone strong declines in abundance at various Caribbean localities and has a poor record of associated fauna. New records of H. cucullata as host are presented for the coral gall crab Opecarcinus hypostegus (Cryptochiridae), the Christmas tree worm Spirobranchus giganteus (Serpulidae) and an unidentified serpulid tube worm of the genus Vermiliopsis. A second association record is reported for the coral barnacle Megatrema madreporarum (Pyrgomatidae). Coral-associated copepods were not found on H. cucullata despite a search for these animals. The new records were compared with previous records of other host coral species that showed elements of the same associated fauna. The present findings indicate that new discoveries concerning Caribbean coral reef biodiversity can still be made during field expeditions by targeting the assemblages of associated fauna of specific benthic host species.