Corallium taiwanicum new species

(Figs. 11,12)

Material examined: Holotype, NMNS-6606-001, Liouciou Islet, southwestern Taiwan, 22˚16.56’N, 120˚6.11’E, depth 736–1040 m, 22 November 2001, collected by S.M. Chao.

Description. The holotype, which is 39 mm tall, consists of just part of the main stem and the stubs of some other branches, of which the largest protrudes at right angles and is 14 mm thick (Fig. 11 A). The origin of the missing higher order branches can be seen near the broken ends of the main branches.

The autozooids only occur on one side of the colony (Fig. 11 A) and are completely absent on the “back”. A group of autozooids forms a protuberance at the base of colony. The contracted autozooids are cylindrical in shape with faint longitudinal striations, which are at the division between the tentacles, and they are 0.93 mm high and 1.15 mm wide at the base. Some polyps are not completely contracted and the tentacles are observable under light microscopy and SEM (Fig. 11 B). The upper parts of some of the autozooids have been lost; the whole autozooids are gray. The openings of the solenial canals are very small and primarily present at the base of the autozooids Fig. 11 C), and the siphonozooids are distributed between the autozooids on the “front” of the colony.

On the “front” side, the cortex is thin and fragile, with veins and irregular creases stained by mud, but on the dorsal side it is smooth and not creased (Fig. 11 A). The axis is solid and round in cross-section with a smooth surface.

Double clubs and 8-radiate sclerites are the commonest types in the cortex where they are intermixed with irregular sclerites and form a thin layer overlying the axis (Fig. 12 A,B). In the autozooids, the commonest type is a highly modified 8-radiate (Fig, 12Ca). In general, the relative abundance and shapes of autozooid sclerites are similar to those of the cortex (Fig. 12 C). On the oral surface of the tentacles, long spindles, which are up to 0.11 mm long, are the only type of sclerite (Fig. 12 D).

There is much variation in the size of sclerites; up to 0.062 mm wide for double clubs, 0.054 mm long for 6- radiates, 0.065 mm long for 7-radiates, and 0.096 mm long for 8-radiates. Asymmetry and an oval shape are the major features of the radiates (Fig. 12 A,B). The double clubs are modified from 8-radiates and are decorated with tubercles and there are some incompletely modified 8-radiates (Fig. 12 Aa,Ba).

In ethanol, the axis is orange, the cortex is dark-pink, and the tentacles are gray. When the sclerites are examined with a microscope using transmitted light, they are slightly pink or colorless, while they are dark-pink under reflected light.

Distribution. This species is currently only known from an area off Liouciou Islet at depths of 736–1040 m.

Etymology. The specific name taiwanicum is alludes to the name of the main island of Taiwan, near where the specimen was collected.

Remarks. Corallium taiwanicum n. sp. differs from other Corallium species by the oval shape and large projections of the 8-radiate capstans.