Morphology and phylogenetic analysis of five deep-sea golden gorgonians (Cnidaria, Octocorallia, Chrysogorgiidae) in the Western Pacific Ocean, with the description of a new species Author Xu, Yu Laboratory of Marine Organism Taxonomy and Phylogeny, Institute of Oceanology, Chinese Academy of Sciences, Qingdao 266071, China & University of Chinese Academy of Sciences, Beijing 100049, China Author Zhan, Zifeng Laboratory of Marine Organism Taxonomy and Phylogeny, Institute of Oceanology, Chinese Academy of Sciences, Qingdao 266071, China & Laboratory for Marine Biology and Biotechnology, Pilot National Laboratory for Marine Science and Technology (Qingdao), Qingdao 266237, China Author Xu, Kuidong Laboratory of Marine Organism Taxonomy and Phylogeny, Institute of Oceanology, Chinese Academy of Sciences, Qingdao 266071, China & Laboratory for Marine Biology and Biotechnology, Pilot National Laboratory for Marine Science and Technology (Qingdao), Qingdao 266237, China & Center for Ocean Mega-Science, Chinese Academy of Sciences, Qingdao 266071, China & University of Chinese Academy of Sciences, Beijing 100049, China kxu@qdio.ac.cn text ZooKeys 2020 989 1 37 http://dx.doi.org/10.3897/zookeys.989.53104 journal article http://dx.doi.org/10.3897/zookeys.989.53104 1313-2970-989-1 8957A11D00984990B073A1999A8AFBC6 0185198E253B50C4BAB71B6BBF0305AB Metallogorgia melanotrichos (Wright & Studer, 1889) Figures 7 , 8 , 9 , 10 ; Tables 2 , 3 Dasygorgia melanotrichos Wright & Studer, 1889: 15, pl. IV, fig. 3, pl. V, fig. 5. Metallogorgia melanotrichos : Versluys, 1902: 87. Metallogorgia melanotrichos : Nutting, 1908: 593-594, pl. LI, fig. 5. Metallogorgia melanotrichos : Kuekenthal , 1919: 503. Metallogorgia melanotrichos : Pasternak, 1981: 51. Type locality. Ascension Island in the South Atlantic Ocean, 778 m depth ( Wright and Studer 1889 ). Voucher specimens. MBM286485, station FX-Dive 222 ( 10°04.73'N , 140°09.45'E ), depth 1839 m, 10 June 2019; MBM286486, station FX-Dive 227 ( 10°37.92'N , 140°05.62'E ), depth 1706 m, 15 June 2019. They were collected from two seamounts (tentatively named as M5 and M8, respectively) located on the Caroline Ridge in the West Pacific Ocean. Diagnosis (extended on the basis of Versluys 1902 ; Kuekenthal 1919 ; Mosher and Watling 2009 ). In adults, main stem monopodial with a few large branches occurring on the distal end. Branching angle between these large branches usually obtuse. In each large branch, strong branchlets subdivided dichotomously and forming a sympodium pattern. In juveniles, main stem monopodial and gracile with branches producing on the lateral of the trunk randomly and subdivided dichotomously in multiple planes. Polyps conical or cylindrical, absent on the stem of adults but present in juveniles. Sclerites elongated and often crossed, arranged densely in polyps and relatively sparsely in coenenchyme. Rods longitudinally arranged in tentacles, covered with sparse fine warts. Rods longitudinally arranged on upper part of polyp body, and scales partially crosswise or transversely arranged on bottom, with nearly smooth surface. Scales transversely arranged in coenenchyme, usually with rounded ends and occasionally irregular edges. Nematozooids absent. Description. For morphological measurements, see Table 2 . Table 2. The morphological measuring data of the specimens of Metallogorgia . "-" means nonexistent or meaningless data.
Characters/ Specimens MBM286485 MBM286486 MBM286484 MBM286487 MBM286488 MBM286489
Species M. melanotrichos M. melanotrichos M. macrospina M. macrospina M. macrospina M. macrospina
Colony height (cm) 76 35 56 51 69 48
Basal stem width (mm) 2.7 1.5 1.0 2.5 3.0 2.5
Branching part height (cm) 9 8 - 12 11 7
Branching part width (cm) 18 18 6 26 20 14
Branch maximal length (cm) 10 12 4 16 13 12
Branches 2 2 22 14 7 6
Interbranch distance (mm) - - 9-25 6-13 13-18 5-18
Internode length (mm) 4-12 3-11 3-7 3-8 3-10 3-11
First internode length (mm) 13-24 12-18 3-8 5-8 6-8 6-11
Polyp height (mm) 1.0-2.5 1.0-4.0, most 2.0 1.0-2.5, most 1.0 average 1.0 1.0-1.5 1.0-1.5
Polyps in internode 1, rarely 2 1, rarely 2 1, rarely 2 1, rarely 2 1, rarely 2 1, rarely 2
Polyps in terminal branchlets 1-3 1-4 1-4 1-4 1-5 1-2
Inter-polyp distance (mm) 1-6 1-4 2-5 1-3 0-5 0-4
Sclerites measured in tentacles (μm) 129-433 x 17-55 125-467 x 21-125 96-450 x 10-85 44-542 x 6-117 120-492 x 12-98 115-460 x 14-78
Sclerites measured in body wall (μm) 172-571 x 14-93 128-429 x 25-125 96-450 x 10-85 44-542 x 6-117 137-473 x 17-93 57-417 x 11-66
Sclerites measured in coenenchyme (μm) 96-378 x 18-66 148-379 x 31-113 112-456 x 10-62 175-394 x 17-75 78-328 x 11-51 70-372 x 14-50
Figures 7, 8 9, 10 11, 12 13, 14 15, 16 17, 18
Distribution. Central Indo-Pacific Ocean ( Wright and Studer 1889 ; Versluys 1902 ), Western and Central Pacific ( Nutting 1908 ; Pasternak 1981 ; present study), Atlantic Ocean, 183-2265 m depth ( Kuekenthal 1919 ; Watling et al. 2011 ; Pante et al. 2012 ). Remarks. Metallogorgia melanotrichos (Wright & Studer, 1889) is characterized by its completely monopodial stem, with the branches in adults occurring on the distal end, and scales in both body wall and coenenchyme (Table 3 ). Furthermore, M. melanotrichos has a much more extensive distribution than its congeners, while other species have a relatively limited distribution. Our specimens match well with the original description in the sclerites, but possess a relatively larger polyp (most 2 mm, up to 4 mm vs. 1.75 mm), and longer scales in coenenchyme (up to 379 μm vs. 225 μm ) ( Kuekenthal 1919 , Table 2 ). The branches of the specimen MBM286486 on one side is irregular and tend to form a fake spiral with branches subdivided dichotomously in multiple planes, while it is regular and forms a planar layer that nearly perpendicular to the trunk in the specimen MBM286485. Table 3. The comparisons of the species (adults) in the genus Metallogorgia Versluys, 1902 and Pseudochrysogorgia bellona Pante & France, 2010.
Characters/ Species M. macrospina M. melanotrichos M. splendens * M. tenuis P. bellona
Branching part sympodial monopodial unknown sympodial* monopodial
Branchlets forming a sympodium yes yes unknown No* No
Interbranch distance (mm) 5-18 - unknown 10-18* 9.9-17.2
Polyp height (mm) 1-1.5 1.5-2.0 1.5 1.5-2.0 1.0-3.3
Sclerites in tentacles rods rods plates spindles rods
Sclerites in body wall rods rods and scales rods rods and spindles rods and scales
Sclerites with its shapes in coenenchyme rods and scales elongated with slightly serrated edges and coarse surface scales elongated with relatively smooth edges and surface rods small, flattened, often with serrated edges and smooth surface scales small, elongated, often with irregular shape and serrated edges. scales and plates with many ornamentation
Dendritic holdfast no no unknown no yes
Reference Kuekenthal 1919 , present study Wright and Studer 1889 , Versluys 1902 , Nutting 1908 , Kuekenthal 1919 , Pasternak 1981 , present study Verrill 1883 , Versluys 1902 , Kuekenthal 1919 , Deichmann 1936 Pasternak 1981 Pante and France 2010 , present study
*, putative species or questionable regarded by Watling et al. 2011 .