Systematics and biogeography of Chrysogorgiidae from the Indian Ocean: discovery of new species on deep-sea ridges

Species of the family Chrysogorgiidae are distributed worldwide in deep-sea environments. However, most recorded species of this family were from the Atlantic and Pacific Oceans, with only a few reports from the Indian Ocean, particularly from ridge regions. This study describes three new species and reports two known species from Indian Ocean ridges, integrating morphological and molecular analyses ( mtMutS and 28S rDNA ). Chrysogorgia pugnioides Ge, Hu & Xu, sp. nov . is characterized by fist-like polyps; warty spindles in tentacles; flat and irregular spindles and elongate scales in the polyp body wall; and slender and smooth scales with toothed to irregular edges in the coenenchyme. Iridogorgia acutisclerita Ge, Zhang & Xu, sp. nov . resembles I. splendens but differs by possessing needles and pointed elongate scales in the polyp body wall. Iridogorgia levisquama Ge, Zhang & Xu, sp. nov . is differentiated from the congeneric I. squarrosa by slender and smooth scales with sharp ends in the polyp body wall and needles with fine wartiness in the tentacles. Parachrysogorgia chryseis and Metallogorgia melanotrichos are reported as new records for the Indian Ocean ridges. These findings expand the known biodiversity and biogeographic range of Chrysogorgiidae in the Indian Ocean ridges.