Chrysogorgia carolinensis, Xu & Zhan & Xu, 2020

Xu, Yu, Zhan, Zifeng & Xu, Kuidong, 2020, 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, ZooKeys 989, pp. 1-37 : 1

Chrysogorgia carolinensis sp. nov. Figures 5 , 6 ; Table 1

Type material.

Holotype. MBM286494, station FX-Dive 226 (10°38.18'N, 140°04.08'E), a seamount (tentatively named as M8) located on the Caroline Ridge, depth 1832 m, 14 June 2019. GenBank accession number: MT269889.

Paratypes. MBM286493, station FX-Dive 224 (10°37.63'N, 140°05.45'E), depth 1509 m, 12 June 2019. MBM286495, station FX-Dive 227 (10°37.92'N, 140°05.62'E), depth 1709 m. MBM286496, station FX-Dive 227 (10°37.92'N, 140°05.62'E), depth 1706 m, 15 June 2019. MBM286497, station FX-Dive 227 (10°37.90'N, 140°05.62'E), depth 1695 m, 15 June 2019. MBM286498, station FX-Dive 227 (10°37.68'N, 140°05.48'E), depth 1537m, 15 June 2019. MBM286499, station FX-Dive 227 (10°37.60'N, 140°05.43'E), depth 1506 m, 15 June 2019. They were all collected from a seamount (tentatively named as M8) located on the Caroline Ridge.

Diagnosis.

Chrysogorgia "group A, Spiculosae" with 1/3L branching sequence. Branches subdivided dichotomously, up to sixth order. Polyps only present in the end of terminal branchlets. Polyps large with pitcher shape, up to 8 mm long. Rods and spindles slender and coarse with many warts on surface in the back and base of tentacles. Scales amoeba-shaped, branched toward to any directions, irregularly and alternately arranged at basal polyp body. Scales rare, transversally arranged in coenenchyme.

Description.

Specimen of holotype ca. 31 cm long and 14 cm wide excluding the holdfast (Figure 5C ). Colony bottlebrush-shaped, with branching sequence 1/3L. Stem golden with metallic luster, ca. 1 mm in diameter at base. Branches subdivided dichotomously, up to sixth order, with distance between adjacent branches 6-12 mm long and orthostiche interval 19-35 mm long in measurements from all specimens. Branches up to 6 cm with the first branch internodes 7-15 mm long and terminal branchlets up to 2 cm long. Polyps only present in the end of the terminal branchlets. Polyps large with pitcher shape, some of them contracted and narrow at the base of tentacles, average 5 mm long with the terminal one up to 8 mm long, and 1-3 mm wide (Figure 5B, D, F ). No polyps in axis internodes.

Rods and spindles slender and coarse with many warts on surface, some of them branched, rarely with one end a little flat, longitudinally arranged in the back of tentacles and usually forming eight distinct columns, and transversally or longitudinally arranged in the base of tentacles, measuring 107-814 × 10-78 μm (length × width, the same below, Figures 5E, G , 6A ). Rare sclerites extend into pinnules, but mostly pinnules free of sclerites. Scales amoeba-shaped, branched in any directions, irregularly and alternately arranged at the basal polyp body, and measuring 161-483 × 14-170 μm (Figures 5H , 6B ). Scales rare and elongate, some of them lobed with irregular edges, transversally arranged in coenenchyme, and measuring 139-221 × 29-67 μm (Figures 5I , 6C ).

Type locality.

A seamount (tentatively named as M8) located on the Caroline Ridge with a depth range of 1506-1832 m.

Etymology.

Named after the type locality, the Caroline Ridge, where the species was discovered.

Distribution and habitat.

Found only from a seamount located on the Caroline Ridge. Colony attached to a rocky substrate (Figure 5A ).

Remarks.

Chrysogorgia carolinensis sp. nov. belongs to the "group A, Spiculosae" with an unusual branching sequence of 1/3L and bottlebrush-shaped colony, which is similar to C. midas Cairns, 2018 and C. abludo Pante & Watling, 2012. However, the new species differs distinctly from these species by the presence of amoeba-shaped scales, which branch toward to any directions at the basal polyp body (vs. absence in both species). Chrysogorgia carolinensis sp. nov. is also similar to C. dendritica by 1/3L branching sequence and the conspicuously amoeba-shaped sclerites at the basal polyp body. However, the new species is easily separated by the bottlebrush-shaped colony (vs. tree-shaped), absence of polyps on internodes (vs. presence) and larger polyps up to 8 mm long (vs. no more than 5 mm) (Table 1 ).

Figures

Figure 5. External morphology and polyps of Chrysogorgia carolinensis sp. nov. A the holotype in situ B close-up branches in situ C the holotype after collection D two polyps under a light microscope E tentacles under a light microscope F a single polyp under SEM G upper part of a polyp under SEM H basal polyp body under SEM I coenenchyme under SEM. Scale bars: 10 cm (B); 2 mm (D); 1 mm (E-G); 300 μm (H); 100 μm (I).

Figure 6. Sclerites of Chrysogorgia carolinensis sp. nov. A sclerites in the back and at the base of tentacles B sclerites at the basal polyp body C sclerites in coenenchyme. Scale bar: 300 μm (all images at the same scale).