Corallium carusrubrum, Tu, Tzu-Hsuan, Dai, Chang-Feng & Jeng, Ming-Shiou, 2012

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 : 5-7

Corallium carusrubrum new species

(Figs. 5,6)

Material examined: Holotype, ASIZ 0000960, Pengjia Islet, northeastern Taiwan, 25˚41.800’N, 122˚39.931’E, depth 156 m, 12 February 2009, collected by J.T. Dong. Paratype; ASIZ 0000961, same data as holotype.

Description. The holotype, which is 46.0 mm tall and 21.8 mm wide and branches laterally four times in one plane, consists only of the main stem and some of the main branches ( Fig. 5 ). The width of the main stem is uniform between the points at which it branches. The origins of the missing higher order branches can be seen near the broken ends of the main branches. The main stem is 4.89 mm in diameter at the base and the secondary branches are nearly circular in cross-section.

The autozooids are fully retracted into cortical mounds, which are irregularly distributed on only one side of the colony, the “front” ( Fig. 5 A,B), and are completely absent on the “back” ( Fig. 5 C) and “flanks”. The shape of the cortical mounds is short and cylindrical, although their base is slightly wider. They may occur singly or in small groups of two or three and are 0.66–0.75 mm high, and 0.37–0.40 mm wide at their base ( Fig. 5 B). They have an 8- lobed margin around the orifice that generally does not extend to the base. Siphonozooids can be found between the cortical mounds. The openings of solenial canals are scattered on the “back” of the colony appearing as small pores 0.060–0.080 mm in diameter ( Fig. 5 C,D).

The cortex is thick and firm, with a fine granular surface due to the arrangement of the surface sclerites. There are some small raised bumps on the cortex surface at the base of each cortical mound. The axis is solid, round in cross-section, with longitudinal shallow grooves on its surface, and as in other species of Coralliidae , the surface is ornamented with small thorny protuberances ( Bayer 1996).

Double clubs and 6-radiates are the most numerous types of sclerite in the cortex, where they intermix with 7- radiates 8-radiates, which are rare, and irregular types, and there are no sclerites in the forms of spindles. The shape and respective abundance of sclerites on the “front” side are similar to those on the “back” ( Fig. 6 A,B). In addition, the sclerites in the cortical mounds and autozooids resemble those in the trunk cortex ( Fig. 6 C). Sclerites vary in symmetry and size from up to 0.062 mm wide for double clubs to up to 0.088 mm long for 6-radiates, 0.091 mm long for 7-radiates and up to 0.092 mm for 8-radiates. The surface of the double clubs is decorated with tubercles.

The living colony axis was crimson with a white center and a similar color remains since it has been preserved in ethanol. The color of the cortex is orange with white spots. When examined under a microscope with transmitted light, the color of the sclerites is slightly orange or colorless.

Distribution. This species is currently only found off Pengjia Islet, the top of a seamount off northeastern Taiwan, at depths of 120– 180 m.

Etymology. The specific name carusrubrum is derived from a combination of the Greek words carus (highpriced) and rubrum (red), which is descriptive of this red precious coral.

Remarks. Among all Coralliidae species, the shape of cortical mounds of C. carusrubrum n. sp. is unique, in that it is short and cylindrical, and not typically hemispherical or prominently cylindrical.

Among the nine previously mentioned Corallium species with retractile autozooids, only C. konojoi and C. elatius do not have 8-radiates as their major type of sclerite. In fact, 8-radiates are completely absent in C. konojoi whereas they do occur in C. carusrubrum n. sp. In addition, the shape of cortical mounds above the retracted autozooids is hemispherical in C. konojoi , but it is short and cylindrical in C. carusrubrum . The absence of 7-radiates and the hemispherical cortical mounds in C. elatius can be used to distinguish it from C. carusrubrum n. sp. It seems that C. carusrubrum n. sp., C. elatius and C. konojoi are closely related species in the northern West Pacific and differ from each other in only a few respects.

Figures

FIGURE 5. Corallium carusrubrum n. sp. holotype, ASIZ 0000960: (A) “ front ” of colony; (B) close-up of cortical mounds; (C) “ back ” of colony; (D) SEM image of cortex—the pore is the opening of a solenial canal.

FIGURE 6. Corallium carusrubrum n. sp. holotype, ASIZ 0000960: (A) cortical sclerites from the “ front ”; (B) cortical sclerites from the “ back ”; (C) sclerites from cortical mounds and autozooids.