Chrysogorgia geniculata : Versluys 1902

Chrysogorgia geniculata (Wright & Studer, 1889) Versluys, 1902

Figs. 38, 39; Table 10

Dasygorgia geniculata Wright & Studer, 1889: 17–18, Pl. IV, fig. 5; Pl. V, fig. 7.

Chrysogorgia geniculata: Versluys, 1902: 79–81, figs. 130–135.

Chrysogorgia geniculata: Nutting 1908: 592, PL. L, fig. 4.

Chrysogorgia geniculata: Kinoshita 1913: 32.

Chrysogorgia geniculata: Kükenthal 1919: 529.

Material examined. MBM286467, station FX-Dive 209 (10°4′40″N, 140°12′12″E), a seamount (tentatively named as M5) on the Caroline Ridge, 993 m, 27 May 2019.

Description. Colony attached to a rocky substrate (Fig. 38A). Specimen bottlebrush-shaped with a little curved stem, about 19 cm long and 4.5 cm wide in maximum with the holdfast not recovered (Fig. 38B). Stem about 2 mm in diameter at base with aeruginous metallic luster at bottom and became brown at the upper part. Branching sequence 1/ 3L. Branches subdivided dichotomously, up to eight orders with branching angle 70°–110°. Distance between adjacent branch 3–4 mm, orthostiche intervals 9–12 mm, the first internode of branch 2–5 mm and the terminal branchlets up to 10 mm long. Polyp average 2 mm tall and 1 mm wide with a strong contraction at the base of tentacular part (Fig. 38C). Polyps usually arranged one on first internode of branch and each internode of the stem, one or two in medial internodes and up to two in terminal branchlets. Tentacular part 1.0– 1.5 mm long and 1.0 mm wide with eight obvious tentacles (Fig. 38C). Verrucae absent.

Scales in aboral face of tentacle rachis transversely arranged in a single row, some of them longitudinally arranged in two rows at the base, thick and curved with many fine warts, almost branched or forked with irregular shape, and became small and thin on the top, measuring 81–265× 12–218 μm (Figs. 38D; 39B). Scales in pinnules longitudinally arranged, slender and nearly smooth, curved with rib-like shape and one or two toothed ends and one serrated side, some of them with sparse fine warts on the surface of ends, measuring 225–538 × 13–63 μm (Figs. 38D; 39A). The margins of its two side often bent up to form a shallow groove. Scales at the base of tentacular part longitudinally or transversely arranged, elongate with a strong medial contraction and many fine warts, some of them with lobed edges and one or two ends became broad and straight, measuring 230–350 × 45–206 μm (Fig. 39C). Scales in basal polyp body wall obliquely or transversely arranged, elongate with a slightly medial contraction, nearly smooth or with sparse fine warts, occasionally with one or more large warts and lobed edges, measuring 125–513 × 13–219 μm (Figs. 38F, 39D). Scales in coenenchyme longitudinally and densely arranged, slender and thick with irregular and lobed edges, usually with many large oval or irregular warts and more or less fine warts, occasionally nearly smooth, measuring 84–420 × 15–102 μm (Figs. 38E, 39E). Plates or scales in polyp mouth area near the tentacles rare to absent, occasionally thick with many warts.

Distribution and habitat. Off the Philippines, Hawaii and Japan, 148–621 m (Wright & Studer 1889, Versluys 1902, Nutting 1908, Kinoshita 1913); a seamount on the Caroline Ridge in the Western Pacific, 993 m.

Remarks. The Caroline specimen matches well with the original description of C. geniculata (Wright & Studer, 1889). The characters of C. geniculata can be summarized by having a typical bottlebrush-shaped colony, thick scales usually with many large warts and irregular edges in coenenchyme, elongate scales in polyp body wall and coarse scales with many fine warts in tentacles (Table 10).