Corallium sulcatum Kishinouye, 1903

Tu, Tzu-Hsuan, Dai, Chang-Feng & Jeng, Ming-Shiou, 2012, Precious corals (Octocorallia: Coralliidae) from the northern West Pacific region with descriptions of two New Species, Zootaxa 3395, pp. 1-17 : 14-16

Corallium sulcatum Kishinouye, 1903

( Fig. 14 )

Corallium sulcatum Kishinouye, 1903a: 624 ; Kishinouye 1903b: 104; Kishinouye 1904: 24, pl.4, figs.1,2; pl.7, fig.3; pl.8, fig.19; Kükenthal 1924: 52; Bayer 1956: 75 (in key); Imahara 1996: 28; Nonaka & Muzik 2010: 96 –97.

Material examined: NMNS-6606-002, Lanyu Island, Taiwan, 22˚48.3’N, 121˚27.4’E, depth 423–439 m, 2 August 2000, collected by S.M. Chao; ASIZ 0000966; Dongsha Atoll, Taiwan depth 400–450 m, 1990, collected by commercial fisherman.

Description. Colony ASIZ0000966 is flabellate with a somewhat dichotomous branching pattern on the larger, lower order branches, which give off slender tiny terminal twigs on the “front” side ( Fig. 14 A). Two of the major branches are missing. Some terminal twigs are fused with each other to form tunnel-like structures on major branches ( Fig. 14 B) that often protruded biserially from these branches. At the base of the main stem, most of these structures are lost. The main stem is 23.54 mm in diameter and nearly circular in its cross section. Commensal polychaetes are harbored in the tunnels formed by the fused terminal twigs.

The autozooids arise biserially, and only from the terminal twigs on the “front” side of the colony where they form groups of 2 or 3 ( Fig. 14 C). When contracted, the polyps are tall and cylindrical, with 8 prominent longitudinal grooves that fold over the intersection of tentacles, and extend halfway down the polyp body. Contracted autozooids are up to 1.58 mm high. Siphonozooids are visible around the contracted autozooids as minute apical pores. The cortex, which is thin and fragile in dry state, is decorated with fine granules on the “front” side of the colony, and has longitudinal rows of papillae on the “back”. The surface of the axis appears smooth when examined under the dissecting microscope, but it exhibits cone-like papillae under SEM ( Fig. 14 D). These cone-like papillae are approximately 0.020 mm high.

The most abundant sclerites of the cortex are 8-radiates, which are mostly symmetrically shaped ( Fig. 14 E). In addition, 6- and 7-radiates, crosses, double clubs and irregular forms are also common in the cortex. The relative abundance and shape of the sclerites in the autozooids resemble those in the cortex ( Fig. 14 F), but the spiny rods, which are only present in the tentacles, are not present in the cortex. These rods are coarsely spinose, often with one end enlarged, and up to 0.096 mm long ( Fig. 14 F). Radiates vary in size from up to 0.068 mm long for 8-radiates, up to 0.061 mm long for 7-radiates, and up to 0.076 mm for 6-radiates. The double clubs are up to 0.059 mm tall and 0.043 mm wide. The tubercular projections of the 8-radiates are dull and blunt. Double clubs are modified forms of 8-radiates, with heads ornamented with blunt projections.

The color of the cortex is either pinkish or orange, but the axis is only pinkish. Under transmitted light, the sclerites are colorless. Specimens in a dry state and in ethanol are similarly colored.

Distribution. Corallium sulcatum is found from the continental shelf off Honshu, Japan to the southwestern coast of Taiwan. It was first discovered at depths of 150–550 m off Boshu, Mera, Japan.

Remarks. The original description of this species was published in Zoologischer Anzeiger by Kishinouye in 1903. That specimen was collected from Boshu, Mera, Japan, depth 150–550 m, but the exact locality and depth are unknown ( Kishinouye 1904). The holotype was from a private collection and cannot be traced.

The specimen described above was gathered from a precious-coral fisherman. According to the records, this species was massively collected in the 1970s to 1990s in waters surrounding Taiwan. When precious-coral fishermen found the coral beds, hundreds of kilograms of corals could be collected on each trip. The commercial name of this species is ‘miss coral’ or ‘pink coral’. Although ‘miss coral’ was intensively collected, it has never been scientifically identified other than as Corallium until now. This is the first time a specimen of “miss coral” has been identified to species level.

The initial examination of the two specimens available indicated the species might be one of the 2 closely related and sympatric species, C. sulcatum and C. boshuensis . According to the descriptions of Kishinouye (1903a, b), and the illustrations in Kishinouye 1904, the major differences between C. sulcatum and C. boshuensis are the color of axis and the grooves on the branches. The axis of C. sulcatum is pink and C. boshuensis is milk white to light yellow, and it is only in C. sulcatum where the fine branches fuse together to form tunnel-like structures. We therefore identify the sample as C. sulcatum and not C. boshuensis .

In addition to C. boshuensis , the other species that is similar to C. sulcatum is C. regale . Both C. sulcatum and C. regale have a pink axis, cylinder-shaped contracted autozooids, and similar types of sclerites, but they differ in the shape and size of their 6- and 8-radiates. Corallium regale has spherical 6-radiates in its cortex ( Fig 13 a), which are not present in C. sulcatum . In addition, according to Bayer (1956), spherical 6-radiates only appear in C. regale , C. maderense (Johnson, 1899) , and C. tricolor (Johnson, 1899) . It seems that these three are closely related species in the northern West Pacific and differ from each other in only a few respects. More characteristics are needed to be sought out to clarify the species boundaries.

Figures

FIGURE 13. Corallium regale Bayer, 1956, holotype, USNM 49520: cortical sclerites.

FIGURE 14. Corallium sulcatum Kishinouye, 1903, ASIZ 0000966: (A) left, “ front ” of colony, right, “ back ” of colony; (B) close up of axis; (C) close up of autozooids; (D) SEM image of axis surface; (E) sclerites from cortex; (F) sclerites from autozooids.