Acanthogorgia densiflora Kükenthal & Gorzawsky,

Hwang, In-Young Cho and Sung-Jin, 2018, A new record of Acanthogorgia species (Octocorallia: Alcyonacea: Holaxonia: Acanthogorgiidae) from Korea, Journal of Species Research 7 (1), pp. 92-96 : 93-95

Acanthogorgia densiflora Kükenthal & Gorzawsky,

1908 OiOi가‼üfi (신%) ( Fig. 1-3)

Acalycigorgia densiflora Kükenthal & Gorzawsky, 1908a: 630 ; 1908b; 44-46, text-figs. 42. Utinomi, 1965 (listed only): 249. Iwase, 1992: 108, text-figs, 4-70B, pl. 23, fig. 5. Imahara, 1996; 29 (listed only). Iwase & Matsumoto, 2006: 82 (listed only). Matsumoto et al., 2007: 239 (listed only).

Acanthogorgia densiflora : Imahara et al., 2014: 224, text-figs. 139-140.

Materials examined. Korea: 1 colony, Gyeongsangnam-do, Geoje-si, Nambu-myeon, Angyeongseom Bukyeodo (34° 41.0077 ʺ N, 128°46.5569 ʺ E), 25 July 2017, Hwang SJ, Jung KJ, 14-24 m depth by SCUBA diving; 1 colony, Gyeongsangnam-do, Tongyeong-si, Hansan-myeon, Maejuk-ri, Eoyudo (34° 39.3458 ʺ N, 128° 34.3335 ʺ E), 27 July 2017, Hwang SJ, Jung KJ, 16-17 m depth by SCUBA diving .

Description. Colony bush like with short stem, not branched in complete one plane, formed by up to four levels of branching ( Fig. 1A). Usually first and second branches make acute angles with main and first branches, respectively. Branches not anastomosing, but sometimes terminal branches anastomosed. Colony 16- 16.5 cm in height, 15-16 cm in width. Polyps cylindrical, non-retractile, densely covering entire surfaces of branches, slightly arranged in whorl pattern with 24 polyps in branches of 0.5 cm length and three-four polyps on tip of branches. Polyp about 2.22-3.45 mm in length, with widths of 0.52-0.82 mm at top, 0.44-0.66 mm at middle, and 0.42-0.98 mm at base. Coenenchyme layer of branches very thin, revealing black axis. Spiny crown around polyp head absent ( Fig. 1B). Spindles compactly arranged in eight chevron rows along polyp walls, sometimes intersecting. Spindles straight, bent, and sometimes bifurcated. Spindles moderately or strongly warty; sometimes one side of spindles without warts and flattened, varying in size ( Fig. 2B ). Straight spindles 0.16-0.35 mm, bent spindles 0.23-0.40 mm, sometimes up to 0.60 mm, and bifurcated spindles 0.21-0.27 mm in length. Tentacular sclerites small plates or scales, 0.10- 0.14 mm in length and 0.04-0.06 mm in width ( Fig. 2A ). Coenenchyme sclerites warty spindles and radiates ( Fig. 3A, B ). Spindles predominant, mainly straight, sometimes bent or bifurcated, and 0.14-0.30 mm in length. Radiates smaller than spindles, 0.05-0.15 mm in length and 0.04-0.15 mm in width.

When alive, polyps and coenenchyme purple, axis of branches and main stem black. Upon preservation in alcohol, polyps and coenenchyme rendered colorless.

Habitat. This species inhabits the rocky slopes at depths between 14 and 24 m, and have bryozoans attached to their branches.

Remarks. This species was characterized by the absence of a spiny crown, and bush-like branching without anastomosis, similar to that of Acanthogorgia irregularis . However, this species was distinguished from the other species by the size of its polyp. The polyps are less than 2 mm long in A. irregularis , but about 3 mm long in A. densiflora . And also, spindles of polyp wall are up to 0.60 mm in A. densiflora , but less than 0.40 mm long in A. irregularis . The descriptions of our studied specimens are in considerable agreement with the original description by Kükenthal and Gorzawsky (1908b), but is slightly different from the description previously recorded by Iwase (1992), in being purple instead of yellow when alive. Also, our specimens had less sclerites in the tentacles than the specimens recorded by Imahara (2014).

Distribution. Pacific Ocean: Korea (South Sea: Hallyeohaesang National Park), Japan (Sagami Bay, Kii Peninsula).

Figures

Fig. 2. Sclerites of Acanthogorgia densiflora. A, plates in tentacles; B, spindles in polyp wall. Scale bars=0.1 mm.

Fig. 3. Sclerites of Acanthogorgia densiflora. A, spindles in coenenchyme; B, radiates in coenenchyme. Scale bars=0.1 mm.