Ophiotholia (Echinodermata: Ophiuroidea): A little-known deep-sea genus present in polymetallic nodule fields with the description of a new species

• Published in: Frontiers in Marine Science 2023-03, Vol.10
• Main Authors: Eichsteller, Angelina, Martynov, Alexander, O’Hara, Timothy D., Christodoulou, Magdalini, Korshunova, Tatiana, Bribiesca-Contreras, Guadalupe, Martinez Arbizu, Pedro
• Format: Article
• Language: English
• Subjects: Biodiversity; Biogeography; brittle stars; Clarion Clipperton Zone; COI; COI protein; Cruises; Deep sea; Deep water; Ferromanganese nodules; Genera; Geographical distribution; Identification keys; Marine invertebrates; Metals; Mitochondria; Morphology; Museums; Natural history; New species; Nodules; Ophiotholia; Ophiotholia saskia; Ophiuroidea; Risk assessment; Scanning electron microscopy; SEM; Spines; Taxonomic revision; Taxonomy
• ISSN: 2296-7745; 2296-7745
• DOI: 10.3389/fmars.2023.1056282

The Clarion Clipperton Zone (CCZ) in the Northeast Pacific Ocean holds the largest deposits of polymetallic nodules at abyssal depths of 4000-6000 m in the world. These nodules are rock formations containing valuable metals and minerals targeted for mining. Polymetallic nodules support a rich sessile and mobile fauna. Little is known so far on the taxonomy, natural history and biogeography of these deep-sea animals which is vital for accurate assessment of the risk of species extinctions from large-scale mining. One of the most abundant megafaunal groups in the CCZ is the Ophiuroidea (brittle stars), of which Ophiotholia is one of the more abundant genera found in the area. The genus Ophiotholia has a world-wide distribution and currently holds six species. Material collected from seven scientific cruises to the CCZ was examined, together with comparative material from all the known species. The small size and the damage caused during sampling often impeded their identification. For this reason, the specimens were also genetically analyzed using a fragment of the mitochondrial COI gene. Scanning Electron Microscope images of the key microstructural characters were made using selected specimens from CCZ as well as from the comparative material. Within the CCZ, four genetically different lineages of Ophiotholia were recognized, while two morphotypes were recognized from examining the non-damaged material. Preliminary results indicate that one morphotype belongs to the known species Ophiotholia supplicans Lyman, 1880, while the second is new to science and is described in this paper. The most relevant morphological characters such as the umbrella spines and the arrangement of their articulations on the lateral arm plate, used for the taxonomy of the genus Ophiotholia are discussed and a revised identification key of all known Ophiotholia species is provided.