Parachrysogorgia chryseis ( Bayer & Stefani, 1988 ) Xu & Zhan & Xu, 2023

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 : 20-29

Parachrysogorgia chryseis ( Bayer & Stefani, 1988) comb. nov.

Figs. 3–16 ; Table 7

Chrysogorgia chryseis Bayer & Stefani, 1988: 267–269 , figs. 7, 8.

Material examined. MBM286358 , station FX-Dive 143 (10°30'20″N, 140°9'32″E), a seamount (tentatively named as M4) on the Caroline Ridge, 688 m, 26 August 2017 . MBM286871 , station FX-Dive 213 (10°4′37″N, 140°11′23″E), 805 m, 31 May 2019 ; MBM286872 , station FX-Dive 215 (10°4′43″N, 140°11′3″E), 866 m, 2 June 2019 ; MBM286873 , station FX-Dive 216 (10°37′45″N, 140°4′32″E), 906 m, 4 June 2019 ; MBM286875 , station FX-Dive 223 (10°3′54″N, 140°15′17″E), 1692 m, 11 June 2019 ; they all from a seamount (tentatively named as M5) on the Caroline Ridge. MBM286874 , station FX-Dive 226 (10°37′45″N, 140°4′32″E), a seamount (tentatively named as M8) on the Caroline Ridge, 1476 m, 14 June 2019 .

Diagnosis (extended based on points of Bayer & Stefani 1988). Parachrysogorgia with a bi-flabellate colony and a usually short main stem. Polyps with sclerites forming eight projecting and acuminate point at the base of a naked tract below each tentacle. Scales at the upper part of tentacles transversely placed, lobed with irregular edges and shape, nearly smooth or with a few large warts. Rods and scales at the basal part of the tentacles rachis longitudinally arranged, blunt, thick and coarse usually with irregular edges and shape, and many large warts. Scales in pinnules slender, some of them curved and gutter-like, and one end broad or forked and the other end narrow or sharp. Scales forming the points smooth and slender, usually with one or two sharp ends, some of them curved or branched with irregular shape. Scales in polyp body wall obliquely or transversely placed, smooth, usually narrow and terete with weak marginal lobes or none. Scales in coenenchyme smooth and elongate with a medial contraction, some of them with slightly lobed edges. No verrucae.

Description. Specimens MBM286358 and MBM286874 incomplete with only a fan collected, and specimen MBM286871, MBM286872, MBM286873 and MBM286875 relatively complete with a bi-flabellate colony. Major branches of each fan subdivided dichotomously or sympodially. Internodes usually 3–10 mm long, occasionally up to 20 mm. Polyps 2.0– 3.5 mm long, some of them up to 5 mm, usually arranged one or two and occasionally up to six on internodes and up to seven on the terminal twigs. Polyps with sclerites forming a conspicuous sharp point at the base of a naked tract below each tentacle. Terminal polyps usually with a long and narrow body and nonterminal polyps usually cylindrical and stout with a slightly expended body. Verrucae absent.

The sclerite forms and arrangement agree with the diagnosis. For the detailed morphological measurements of each specimen, see Table 7 .

Distribution. Pacific Ocean incuding Indonesian Ceram Sea, 732 m ( Bayer & Stefani 1988) and seamounts on the Caroline Ridge, 688–1692 m.

Remarks. The six specimens match the holotype of Parachrysogorgia chryseis in having a bi-flabellate colony, eight sharp points beneath the tentacles and the same sclerite forms, including scales terete, tapering smoothly toward pointed ends with weak and broad marginal lobes in polyp body wall, scales usually various shaped with prominent marginal lobes in coenenchyme, blunt and thick rods present on the basal tentacles, thin and narrow scales in pinnules. Moreover, their 28S rDNA sequences are identical with the intraspecific differences (see the genetic analysis before). Thus, we identified the six specimens as the same species. The minor differences include (1) specimen MBM286875 is a little pink ( Fig. 11B ), while the other specimens are yellow to brown; (2) the colony of specimen MBM286875 is small with only one polyp in each internode and terminal branchlets, while the other specimens are relatively large with up to six polyps in internodes and up to seven in terminal ( Table 7 ); (3) a part of long and relatively straight stem is present in specimen MBM286874 with many polyps in its internodes ( Fig. 14B ), and it is short in MBM286873 with a few polyps ( Fig. 9B ), while this part is nearly absent in other specimens; (4) some branchlets are occasionally anastomotic in specimen MBM286874; (5) the points below the tentacles are occasionally short in MBM286872 ( Fig. 5E, G ) and inconspicuous in MBM286873 ( Fig. 9F ). These differences are not constant and may be caused by different growth stages or environment (e.g., depth, see Quattrini et al. 2017) or inadequate measurement, and we thus treat as the conspecific variation. The six specimens of Parachrysogorgia chryseis indicate this species has high intraspecific variations.

Figures

FIGURE 3. The external morphology and polyps of Parachrysogorgia chryseis (Bayer & Stefani, 1988) comb. nov., specimen MBM286358. A, B. The same specimen in situ and after collection. C. A part of branch under a light microscope. D, E. A single non-terminal polyp under a light microscope and SEM, respectively, showing the bare, sclerite-free area at the base of each tentacle (arrow in E) and eight distinct acuminate projections beneath the tentacles (arrow in D). F. Tentacular part under SEM. G. Polyp body wall under SEM. H. A part of branch under SEM. Scale bars: 5 cm (B); 5 mm (C); 1 mm (D–E), 500 μm (F–H).

FIGURE 4. Sclerites of Parachrysogorgia chryseis (Bayer & Stefani, 1988) comb. nov., specimen MBM286358. A. Sclerites in polyp body wall. B. Sclerites in coenenchyme. C. Sclerites in the point at the base of a naked tract below each tentacle. D. Sclerites in the basal part of tentacle rachis. E. Sclerites in the upper part of the tentacle rachis. F. Sclerites in pinnules. Scale bars: 500 μm (A–C in the same scale), 300 μm (D–F in the same scale).

FIGURE 5. The external morphology and polyps of Parachrysogorgia chryseis (Bayer & Stefani, 1988) comb. nov., specimen MBM286871. A, B. The same specimen in situ and after collection. C. A part of branch under a light microscope. D. A part of branch under SEM. E. A single non-terminal polyp under SEM. F. Tentacular part under SEM. Scale bars: 10 cm (B); 5 mm (C); 1 mm (E, F), 500 μm (D).

FIGURE 6. Sclerites of Parachrysogorgia chryseis (Bayer & Stefani, 1988) comb. nov., specimen MBM286871 A. Sclerites in polyp body wall. B. Sclerites in coenenchyme. C. Sclerites in the point at the base of a naked tract below each tentacle. D. Sclerites in the basal part of tentacle rachis. E. Sclerites in the upper part of the tentacle rachis. F. Sclerites in pinnules. Scale bars: 500 μm (all in the same scale).

FIGURE 7. The external morphology and polyps of Parachrysogorgia chryseis (Bayer & Stefani, 1988) comb. nov., specimen MBM286872 A, B. The same specimen in situ and after collection. C. A part of branch under a light microscope. D, G. A single non-terminal polyp under a light microscope and SEM, respectively. E, F. A single terminal polyp under SEM. H. A part of branch under SEM. Scale bars: 10 cm (B); 5 mm (C); 1 mm (D–G), 500 μm (H).

FIGURE 8. Sclerites of Parachrysogorgia chryseis (Bayer & Stefani, 1988) comb. nov., specimen MBM286872. A. Sclerites in polyp body wall. B. Sclerites in the point at the base of a naked tract below each tentacle. C. Thin sclerites in coenenchyme. D. Some thick sclerites in coenenchyme. E. Sclerites in the basal part of tentacle rachis. F. Sclerites in the upper part of the tentacle rachis. G. Sclerites in pinnules. Scale bars: 500 μm (A–D in the same scale), 300 μm (E–G in the same scale).

FIGURE 9. The external morphology and polyps of Parachrysogorgia chryseis (Bayer & Stefani, 1988) comb. nov., specimen MBM286873. A, B. The same specimen in situ and after collection. C. A single non-terminal polyps under a light microscope. D. Tentacular part under SEM. E. A part of branch under a light microscope. F. A single non-terminal polyp under SEM. G. A single terminal polyp under SEM. H. A part of branch under SEM. Scale bars: 5 cm (C); 2 mm (E); 1 mm (C, D, F, G), 500 μm (H).

FIGURE 10. Sclerites of Parachrysogorgia chryseis (Bayer & Stefani, 1988) comb. nov., specimen MBM286873. A. Sclerites in polyp body wall. B. Sclerites in coenenchyme. C. Sclerites in the point at the base of a naked tract below each tentacle. D. Sclerites in the upper part of the tentacle rachis. E. Sclerites in the basal part of tentacle rachis. F. Sclerites in pinnules. Scale bars: 500 μm (A–C in the same scale), 300 μm (D–F in the same scale).

FIGURE 11. The external morphology and polyps of Parachrysogorgia chryseis (Bayer & Stefani, 1988) comb. nov., specimen MBM286875. A, B. The same specimen in situ and after collection. C, D. A single non-terminal polyp under a light microscope and SEM, respectively. E, F. A single terminal polyp under a light microscope and SEM, respectively. Scale bars: 5 cm (B); 1 mm (C–F).

FIGURE 12. Sclerites of Parachrysogorgia chryseis (Bayer & Stefani, 1988) comb. nov., specimen MBM286875. A. Sclerites in polyp body wall. B. Sclerites in the point at the base of a naked tract below each tentacle. C. Sclerites in coenenchyme. Scale bars: 500 μm (all in the same scale).

FIGURE 13. Sclerites of Parachrysogorgia chryseis (Bayer & Stefani, 1988) comb. nov., specimen MBM286875. A. Sclerites in the basal part of tentacle rachis. B. Sclerites in the upper part of the tentacle rachis. C Sclerites in pinnules. Scale bars: 300 μm (A), 200 μm (B, C in the same scale).

FIGURE 14. The external morphology and polyps of Parachrysogorgia chryseis (Bayer & Stefani, 1988) comb. nov., specimen MBM286874. A, B. The same specimen in situ and after collection. C. A single non-terminal polyp under a light microscope. D, F and G. A single terminal polyp under a light microscope and SEM, respectively. E. A part of branch under SEM. Scale bars: 5 cm (B); 1 mm (C, D, F, G), 500 μm (E).

FIGURE 15. Sclerites of the terminal polyps of Parachrysogorgia chryseis (Bayer & Stefani, 1988) comb. nov., specimen MBM286874. A. Sclerites in the point at the base of a naked tract below each tentacle. B. Sclerites in polyp body wall. C. Sclerites in the basal part of tentacle rachis. D. Sclerites in coenenchyme. E. Sclerites in the upper part of the tentacle rachis. F. Sclerites in pinnules. Scale bars: 500 μm (A–D in the same scale), 200 μm (E, F in the same scale).

FIGURE 16. Sclerites of the non-terminal polyps of Parachrysogorgia chryseis (Bayer & Stefani, 1988) comb. nov., specimen MBM286874. A. Sclerites in the basal part of tentacle rachis. B. Sclerites in polyp body wall. C. Sclerites in the point at the base of a naked tract below each tentacle. D. Sclerites in the upper part of the tentacle rachis. E. Sclerites in pinnules. Scale bars: 300 μm (B, C in the same scale), 200 μm (A, D, E in the same scale).