Hemicorallium tokiyasui Nonaka & Hayashibara 2021, sp. nov.
Creators: name: Nonaka, Masanori
name: Hayashibara, Takeshi
Publisher: name: Zenodo
Year: 2021
Subjects: Biodiversity
Taxonomy
Animalia
Cnidaria
Anthozoa
Alcyonacea
Coralliidae
Hemicorallium
Hemicorallium tokiyasui

description: Hemicorallium tokiyasui sp. nov.   (Figs 57–63; Tables. 2, 7)  
 Material examined. Holotype, NSMT-Co 1736, Koko Seamount, 414 m, 4 September 2009.   
 Diagnosis. Colony is branched almost in one plane with a few anastomoses. Branching irregular, at acute angles near the base and almost right angles in the twigs. Contract-   
ed autozooids are concentrated on both sides of the terminal twigs, at 1–2 mm intervals, 0.8–1.3 mm (average 1.0 mm) in diameter and 0.6–1.8 mm (average 1.1 mm) in height. Coenenchyme is 0.04–0.11 mm (average 0.06 mm) thick in the dry condition, with small but distinct warts on the twigs, pale pink in color. Axis stout, no pits underneath autozooids, surface smooth, pale purple to pink in color. Tentacles contain short (<0.1 mm) rods, coenenchyme contains several types of small (<0.05 mm) sclerites (6-radiate, 7-radiates, 8-radiates and multi-radiates). Double-clubs are absent.  
 Description of the holotype. Colony form. The specimen is part of a colony with a thick stem and sharp twigs (Fig. 57). The colony is about 80 mm tall and 60 mm wide, and is branched in almost one plane. Very thin twigs branch off directly from the thick stems, and the twigs have a few anastomoses (Fig. 58). They tend to occur on one side of the colony, with almost no twigs on the remaining sides. Their angle of branching is acute in the stem, but at almost right angles in the twigs. Stem diameter is about 12 mm and thinnest branch tip is about 1–2 mm. Branch cross sections are rounded (Fig. 61).   
Polyps. The autozooids are not retracted into the coenenchyme, making cylindrical mounds with 8 longitudinal striations (Fig. 60). Most of them are distributed on all sides of the twigs, with a few of them tending to one side of the stem (Fig. 58). They are 1.00± 0.12 mm in diameter and 1.10± 0.26 mm in height (Table 2), distributed at 1–2mm intervals on the twigs (Fig. 59). Siphonozooids are inconspicuous, distributed on the twigs, and about 0.06 mm in diameter (Fig. 59; Table 2).  
Axis. The surface of the axis is smooth, not striated (Fig. 58). There are no rounded pits on the surface of the axis at the position of each autozooid. A few commensal burrows are present in the axis, with one polychaete visible by microscope (Fig. 60).  
Coenenchyme. Coenenchyme is very thin, 0.06± 0.02 mm thick (Fig. 61; Table 2). Small but distinct warts 0.20± 0.02 mm in diameter, are distributed in longitudinal rows on the surface of the colony (Fig. 59).  
Color. The dry coenenchyme is pale pink, some twigs are whitish to white (Figs 57, 58). Axis is pale purple to pink in the stem, whitish in the twigs (Figs 57, 58).  
Sclerites. The tentacles contain mainly rods (46%; 0.077± 0.011 mm long, 0.023± 0.004 mm wide), multi-radiates (28%; 0.060± 0.009 mm long, 0.036± 0.005 mm wide) and a few 6-radiates, 7-radiates, 8-radiates and others (Figs 62, 63; Table 7).  
The autozooid mounds contain mainly multi-radiates (38%; 0.059± 0.009 mm long, 0.042± 0.004 mm wide), asymmetric 8-radiates (17%; 0.060± 0.009 mm long, 0.041± 0.004 mm wide), and some 6-radiates, 7-radiates, symmetric 8-radiates, a few 5-radiates and others are present (Figs 62, 63; Table 7).  
The branch tips contain mainly asymmetric 6-radiates (23%; 0.044± 0.004 mm long, 0.034± 0.003 mm wide), 7-radiates (23%; 0.047± 0.004 mm long, 0.035± 0.003 mm wide), asymmetric 8-radiates (20%; 0.047± 0.005 mm long, 0.034± 0.004 mm wide), multi-radiates (19%; 0.050± 0.011 mm long, 0.037± 0.004 mm wide), and a few crosses, symmetric 6-radiates, and symmetric 8-radiates (Figs 62, 63; Table 7).  
Coenenchyme on the base of the colony contains mainly asymmetric 8-radiates (26%; 0.048± 0.003 mm long, 0.034± 0.003 mm wide), symmetric 8-radiates (17%; 0.047± 0.005 mm long, 0.033± 0.004 mm wide), 7-radiates (16%; 0.046± 0.005 mm long, 0.035± 0.004 mm wide), multiradiates (15%; 0.045± 0.003 mm long, 0.036± 0.003 mm wide) and asymmetric 6-radiates (14%; 0.044± 0.004 mm long, 0.034± 0.002 mm wide). There are a few crosses 5-radiates and symmetric6-radiates (Figs 62, 63; Table 7).  
 Etymology. Named for the location where the specimen collected, Koko Seamount, one of the Emperor Seamounts. In 1954, Robert S. Dietz, a United States oceanographer, named the seamounts in the chain after Japanese emperors (mainly ancient) (Sugiyama 2005). Koko Seamount was named for the 58th Japanese Emperor, Koko (830–887). The scientific name of this new species honors Emperor Koko and is derived from his “Imina” or personal name, Tokiyasu.   
 Remarks. Tu et al. (2015b) described the morphological characters of the genus Hemicorallium as follows: Contracted autozooids are not retracted in the coenenchyme, cylindrical in shape, usually distributed on one side of the colony. The tentacles contain slender rod-shaped sclerites. These characters are all found in NSMT-Co 1736.   
 In the species of the genus Hemicorallium described from the Pacific, only H. laauense and H. taiwanicum have contracted autozooids similar in size to NSMT-Co 1736 (about 1.0 mm in both height and diameter). However, H. laauense has a whitish axis and coenenchyme, and H. taiwanicum has an orange axis and dark-pink coenenchyme. The morphological features of this specimen most resemble H. kaiyo sp. nov. as described above (in autozooid size and sclerite composition) but axis color and sclerite size are remarkably different (those of H. kaiyo are much larger). A unique character of NSMT-Co 1736 is having a pale purple to pink axis. Moreover, except for the tentacle rods, the sclerites of NSMT-Co 1736 are smaller, <0.05 mm, than those of H. laauense (> 0.08 mm) and H. taiwanicum: 0.054 –0.096 mm).
description: Published as part of Nonaka, Masanori & Hayashibara, Takeshi, 2021, A Report on Coralliidae (Cnidaria: Octocorallia) Specimens Collected from the Emperor Seamounts with Descriptions of Three New Species, pp. 297-342 in Species Diversity 26 on pages 331-335, DOI: 10.12782/specdiv.26.297, http://zenodo.org/record/5739111