Iridogorgia densispicula, Xu & Zhan & Li & Xu, 2020

Xu, Yu, Zhan, Zifeng, Li, Yang & Xu, Kuidong, 2020, Morphology and phylogenetic analysis of two new species of deep-sea golden gorgonians (Cnidaria: Octocorallia: Chrysogorgiidae) from seamounts in the Western Pacific Ocean, Zootaxa 4731 (2), pp. 249-262 : 251-254

Iridogorgia densispicula n. sp.

( Figs 2 and 3 ; Table 1 )

urn:lsid:zoobank.org:act:EC438B59-1AA6-4E32-BC6C-2011D5D67F0B

Holotype: MBM286538 , collected from the station FX-Dive 137 (10°35.10’N, 140°07.46’E) of a seamount located at the Caroline Plate with water depth of 1204 m, on 21 August 2017. GenBank accession MK 431864 .

Diagnosis: Colony slender. Polyps with bud-like shape, towards the branch end situated at an acute angle. Sclerites densely arranged in polyps and branches, including the inter-polyp coenenchyme. Tentacles covered with rods, forming eight distinct columns. Scales at bases of polyp usually with sharp ends, and long spindles in coenenchyme.

Description: In vivo, colony with a slender stem and four helical turns on the top, growing on a rocky bottom ( Fig. 2A ). Specimen about 93 cm in height, with a part of straight stem about 28 cm. Each helical turn about 13–15 cm in height and 3–4 cm in diameter. Central axis 3 mm in diameter at base with yellow metallic luster. Branches arranged along one side, about 3–5 mm apart. The shortest branch at the top 5.4 cm, and the longest up to 23.8 cm long with 37 polyps counted ( Fig. 2B ). Polyps approximately 3–7 mm apart, with a bud-like shape, 1–3 mm in height, and 3–4 mm in width at base. Polyp with an expanded base and tilted at an acute angle with branch ( Fig. 2C ). Golden eggs present at base and visible under the microscope ( Fig. 2D ). Tentacles 2–3 mm long, forming eight obvious parallel columns terminating at base. A few verrucae in polyps and branches.

Sclerites densely arranged in polyps and branches including the inter-polyp coenenchyme, commonly with small protuberances on surface, sometimes slightly branched ( Fig. 2E ). Rods longitudinally arranged in tentacles, rarely crossed, sometimes with bulgy edges and large warts, and measuring 164–945 × 27–98 μm with an average of 462 × 38 μm ( Fig. 3A ). Slender spindles in coenenchyme mostly with two sharp ends, occasionally crossed, and measuring 215–835 × 25–60 μm with an average of 545 × 42 μm ( Fig. 3B ). Spindle-like scales in polyp bases, usu- ally with a broad waist and sharp ends, sometimes with a slight midway constriction, measuring 102–627 × 16–110 μm with an average of 312 × 59 μm ( Fig. 3C ).

Etymology: Composite of the Latin adjective densus (dense) and the Latin noun spicula (spicule), referring to the densely arranged spicules, a distinct feature of the species.

Distribution: Known only from the seamount in the Caroline Plate with water depth of 1204 m. Growing on a rocky bottom with the water temperature 3.6°C and the salinity 35.8.

Figures

FIGURE 2. The external morphology and polyps of Iridogorgia densispicula n. sp. A. The holotype in situ. Laser dots spaced at 33 cm used for measuring dimensions. B. The holotype after collection. C. Two branches with various polyps. D. One polyp with eggs under light microscope. E. One polyp in SEM. Scales = 20 cm (B), 2 mm (C), and 1 mm (D, E).

FIGURE 3. Sclerites of Iridogorgia densispicula n. sp. A. Rods in tentacles. B. Spindles in coenenchyme. C. Scales in bodies and at bases. Scale = 200 μm (all in the same scale).