Hydroids (Cnidaria, Hydrozoa) of Baa Atoll (Indian Ocean, Maldives Archipelago)
Résumé
This study provides the first description of hydroid species and communities in Baa Atoll. 22 stations from 0 to 30 meters depth (except one at 50) were visited based on contrasted geomorphology, and 568 benthic specimens collected. Preliminary results provided a provisional list of 115 species, of which 100 are new records for the Maldives Archipelago. The hydroid fauna of Baa Atoll consists of 74% leptothecates and 26% antoathecates, and represents 26 families and 43 genera. Besides the Eudendriidae (7 spp), the most speciose families (>10 spp) were the Aglaopheniidae, Campanulariidae, Halopterididae, Haleciidae and Sertulariidae. Several new species are suspected but additional material and/or more taxonomic studies are required to complete the descriptions. The more common species are documented by underwater and laboratory photographs (29 spp), with a focus on aglaophenids. The species richness was high and well distributed in the varied locations visited. Richness was higher on atoll rim faro than inside the atoll. Richness was also higher on outer slopes and passes than reef flats and inner reefs of rim faro. The absence of Aglaophenia cupressina and of the fire corals Millepora was noticed. Combining records gathered from old literature data and those of this Baa Atoll study, the hydroid species richness in the Maldives reaches 160 spp, which is high like in other Indian Ocean islands.