Chrysogorgia rigida Versluys, 1902

Xu, Yu, Zhan, Zifeng & Xu, Kuidong, 2023, Studies on western Pacific gorgonians (Anthozoa: Octocorallia, Chrysogorgiidae). Part 1: a review of the genus Chrysogorgia, with description of a new genus and three new species, Zootaxa 5321 (1), pp. 1-107 : 68-70

Chrysogorgia rigida Versluys, 1902

Figs. 40 , 41 , Table 10

Chrysogorgia rigida Versluys, 1902: 81–83 , figs. 136–142.

Chrysogorgia rigida: Kükenthal 1919: 536 .

Material examined. MBM286356 , station FX-Dive 143 (10°30′20″N, 140°9′32″E), a seamount (tentatively named as M4) on the Caroline Ridge, 691 m, 26 August 2017 .

Description. Colony bottlebrush-shaped and attached to a rock ( Fig. 40A ). Specimen about 24 cm long and 6 cm wide in maximum with an unbranched stem about 9 cm long. Holdfast small and nearly same as the base of the stem. Stem about 1.5 mm in diameter at base with a strong blue metallic luster and became brown in branch. Branching sequence 1/ 3L. Branches subdivided dichotomously, up to four orders with branching angle 90°–100°. Distance between adjacent branch about 4 mm, orthostiche intervals 12–13 mm, the first internode of branch about 5 mm and the terminal branchlets up to 9 mm. Polyps 1.5–2.0 mm tall and 1.0 mm wide, usually with a conical shape, some of them with an expanded body and became narrow at the base of tentacular part ( Fig. 40C–E, G ). Polyps often arranged one on first and medial internodes, and up to three in terminal branchlets. Polyps absent in stem internodes and verrucae also absent. Tentacular part 1.0– 1.5 mm long with eight obvious tentacles.

Scales in aboral face of tentacle rachis transversely arranged in a single row, thick and curved, branched or forked with irregular shape but relatively uniform from the tentacle bottom to top, usually with broad ends and many obvious fine or coarse warts, measuring 72–267 × 13–161 μm ( Figs. 40G , 41C ). Scales in pinnules longitudinally arranged, slender and curved with rib-like shape, usually coarse and the margins of its two side often bent up to form a shallow groove, some of them nearly smooth with sparse warts on one end. It usually with one end more toothed and the other end slightly lobed and one side serrated at the distal, measuring 266–444 × 11–89 μm ( Figs. 40G , 41A ), and with one or two ends forked or sharp with one side slightly serrated at the proximal ( Fig. 41B ), measuring 344–461 × 5–28 μm. Scales at the base of tentacular part longitudinally or transversely arranged, elongate with an obvious medial contraction, some of them one or two ends became broad and straight, usually irregular with lobed edges, nearly smooth or with sparse fine warts on surface and shallow toothed traces on edge surface, measuring 100–356 × 33–267 μm ( Fig. 41D ). Scales in basal polyp body wall longitudinally or transversely arranged, stacked with each other, elongate with an obvious medial contraction and rounded ends and shallow toothed traces on edge surface, nearly smooth, occasionally with sparse fine warts and lobed with irregular shape, measuring 78–333 × 17–167 μm ( Figs. 40G , 41E ). Scales in coenenchyme longitudinally arranged, elongate and thin with usually one or more large oval warts on center and many fine warts, measuring 95–241 × 17–59 μm ( Figs. 40F , 41F ). It usually with a slight medial contraction and irregular and coarse edges, which surface arranged with dense small warts.

Distribution and habitat. Off the Philippines, 522 m ( Versluys 1902); a seamount on the Caroline Ridge in the Western Pacific Ocean, 691 m.

Remarks. Chrysogorgia rigida Versluys, 1902 is characterized by a typical bottlebrush-shaped colony, thin scales usually with an large wart on center and coarse warty edges in coenenchyme, irregular scales with relatively uniform shape and many fine warts in tentacles, and a strong blue metallic luster in stem. It is most similar to C. geniculata , but differs from it by relatively regular scales in polyp body wall (vs. elongate and slender with irregular shape), thin scales with usually one large warts on center in coenenchyme (vs. thick with many large warts), more rib-like scales with forked or two sharp ends in pinnules (vs. rare) ( Table 10 ).

Our specimen matches well with the original descriptions of C. rigida in sclerite forms and colony shape, but differs by larger orthostiche intervals and smaller polyp size, which may be caused by different status of tentacles and growth stage, and is treated as the intraspecific variation.

Figures

FIGURE 40. The external morphology and polyps of Chrysogorgia rigida Versluys, 1902. A, B. The same specimen in situ (the arrow) and after collection. C, D, G. Non-terminal polyps under a light microscope and SEM, respectively. E. A single terminal polyp under SEM. F. A part of branch under SEM. Scale bars: 5 cm (B); 1 mm (C–E, G); 300 μm (F).

FIGURE 41. Sclerites of Chrysogorgia rigida Versluys, 1902. A. Sclerites with toothed ends in pinnules. B. Sclerites with forked or sharp ends in pinnules. C. Sclerites in tentacle rachis. D. Sclerites at the base of tentacular part. E. Sclerites in the basal polyp body wall. F. Sclerites in coenenchyme. Scale bars: 300 μm (A–E in the same scale); 200 μm (F).