Corallium uchidai, Nonaka & Muzik & Iwasaki, 2012

Nonaka, Masanori, Muzik, Katherine & Iwasaki, Nozomu, 2012, 3428, Zootaxa 3428, pp. 1-67 : 16-26

Corallium uchidai sp. nov. ( Figs. 10–17; Tables 2, 4)

Material examined: Holotype, USNM 19925 , Murotsu , Tosa , Japan. The specimen is dry and was donated by Kishinouye and was labeled by him as C. elatius .

Diagnosis. Colony irregularly branched in one plane, at mostly 45–90 degrees angles, without anastomoses. Coenenchymal mounds distributed all around the branches, 2.24–4.86 mm apart, scarcer near the base and more crowded near the twig tips, 1.12–1.62 mm diameter and 0.36–0.65 mm in tall. Coenenchyme is 0.15–0.24 mm thick in the dry condition. Axis finely striated in the longitudinal direction at 0.17–0.27 mm intervals, and brick-red in colour. Pits beneath coenenchymal mounds not distinct. Double-clubs and 6-radiates are most abundant, and 7-, 8-radiates and rods are not common.

Description of the holotype:

Colony form: The specimen is an almost complete colony (one main branch is missing) with a holdfast and a portion of substratum (limestone rock) attached ( Fig. 10). The colony is about 100 mm tall and 90 mm wide, but originally (including the missing branch) would probably have been much wider. The colony is planar without anastomoses, although a pair of the branches may appear to be joined in photographs ( Fig. 11). Branches occur irregularly, angle of branching is at mostly 45–90 degrees, and they are tapered at the tip. The diameter of the base of the colony is about 28 mm, the main stem 10 mm, and thinnest branch tip about 2 mm. Branch cross sections are rounded ( Fig.13).

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Polyps: Originally retracted into the coenenchyme, making hemispherical coenenchymal mounds, the autozooid tissue has now completely disintegrated. The coenenchymal mounds are distributed all around the colony ( Fig. 11). They are 1.12–1.62 mm in diameter and 0.36–0.65 mm in height, with an 8-lobed summit ( Figs. 12, 14). They are rather dispersed, 2.24–4.86 mm apart, scarcer near the base and more crowded near the twig tips. Siphonozooids ( Fig. 12) form small pits on the surface of the coenenchyme, 0.02–0.08 mm in diameter, and are irregularly distributed at mean intervals of 0.39–1.13 mm.

Axis: The surface of the axis ( Fig. 14) is faintly longitudinally grooved at 0.17–0.27 mm intervals, and covered with minute tubercles ornamented with thorny projections ( Fig.15). Pits are not distinct but are rather flattened areas on the axis at the position of each coenenchymal mound ( Fig. 14).

Coenenchyme: This is 0.15–0.24 mm thick in the dry condition ( Fig. 13) and the longitudinal axial grooves are not visible through it ( Fig. 14).

Colour: The dry coenenchyme is predominantly brick-red, whitish near the base and branch tips ( Figs. 10, 11). The axis is redder than the coenenchyme ( Fig. 13).

Sclerites: The coenenchymal mounds contain mainly double-clubs with a rough surface 0.040 –0.062 mm long and 0.032 –0.051 mm wide, asymmetric 6-radiates 0.037 –0.080 mm long and 0.028 –0.062 mm wide, symmetric 6- radiates 0.041 –0.065 mm long and 0.027 –0.047 mm wide, and a few small 6-radiates: 7-, 8-radiates and rods are rare ( Fig. 16A). The coenenchyme on the branch tips contains mostly double-clubs with a rough surface 0.038 – 0.061 mm long and 0.031 –0.050 mm wide, and a few 6-radiates (both symmetric and asymmetric); 7-radiates are very rare ( Fig. 16B). The coenenchyme on the base of the colony contains mainly symmetric 6-radiates 0.041 – 0.071 mm long and 0.034 –0.059 mm wide, double-clubs with a rough surfaces 0.038 –0.053 mm long and 0.034 – 0.052 mm wide, asymmetric 6-radiates 0.042 –0.063 mm long and 0.035 –0.050 mm wide, and a few 7- and 8- radiates ( Fig. 16C). The statistical data for sclerites of this specimen are shown in Table 5.

The average size of double-clubs is similar from all three regions (base, tips, and mounds), and that of the asymmetric 6-radiates is also almost the same from all three parts. However, symmetric 6-radiates from the base are larger than both those from the branch tips and from the coenenchymal mounds (Table 5).

Relative abundance of sclerites ( Fig. 17; Table 5): There are seven kinds of sclerites in the coenenchyme of the holotype. In the coenenchymal mounds, double-clubs with a rough surface represent 35% of the sclerites, asymmetric 6-radiates 25%, and symmetric 6-radiates 21%. The sclerites in the branch tip are mostly double-clubs with a rough surface (70%). In the base, symmetric 6-radiates represent 52% of the sclerites, double-clubs with a rough surface 22%, and asymmetric 6-radiates 19%. Symmetric 6-radiates are most abundant in the base coenenchyme (52%) but are less common from the mounds (21%) and from the tips (13%). Meanwhile, doubleclubs with a rough surface are the most abundant sclerites from the mounds (35%) and from the branch tip (70%). Asymmetric 6-radiates are present in all regions of the specimen (16–25%) but are never the most abundant sclerite. Small 6-radiates, 7-radiates, 8-radiates, and rods are rare in all parts of the specimen, and in fact 6-radiates and rods are only present in the coenenchymal mounds.

Etymology: This species is named in honor of Dr. Senzo Uchida, Director of Okinawa Churaumi Aquarium for more than thirty years, from 1981 until his retirement in May, 2011. His extraordinarily capable leadership led Churaumi to become the most successful aquarium in Japan, achieving not only many world-firsts and highest attendances, but also excelling in aquatic research on many species of mammals, fishes, reptiles, amphibians and invertebrates. His expert management made this study of Japanese Coralliidae possible.

Remarks: The holotype of C. uchidai sp. nov. has coenenchymal mounds equally on both sides, a rare characteristic for the genus Corallium . Table 8 shows the list of the species of Coralliidae with hemispherical coenenchymal mounds. There are no species yet described having the same characters of USNM 19925, which has a planar colony form, polyps arranged on all sides, and a reddish colored axis.