Xenia konohana, Koido & Imahara & Fukami, 2022

Koido, Tatsuki, Imahara, Yukimitsu & Fukami, Hironobu, 2022, Xenia konohana sp. nov. (Cnidaria, Octocorallia, Alcyonacea), a new soft coral species in the family Xeniidae from Miyazaki, Japan, ZooKeys 1085, pp. 29-49 : 29

Xenia konohana sp. nov.

New Japanese name: konohana-umiazami Figs 3 , 4 , 5 , 6 , 7 , 8 , 9 , 10

Synonym.

Xenia sp. 1 Koido et al. 2019: Table 1 , figs 2J-4J.

Materials.

Holotype: KBF-OA-00092 (MUFS-COMO 4 in Koido et al. 2019), Oshima Isl. , Nichinan City, Miyazaki Prefecture, depth <5 m, July 2, 2012 . Paratypes: KBF-OA-00093 (MUFS-COMO 53 in Koido et al. 2019), Oshima Isl. , Nichinan City, Miyazaki Prefecture, depth <10 m, December 25, 2012 ; KBF-OA-00094 (One colony with two stems) (MUFS-COMO 54 in Koido et al. 2019), Oshima Isl. , Nichinan City, Miyazaki Prefecture, depth <10 m, December 25, 2012 .

Descriptions.

The holotype (Fig. 2A ) displays a typical Xenia -style growth form ( Alderslade 2001; Benayahu 2010), featuring a distinct cylindrical stalk, 35 mm high and 20 mm wide attached to a rock. The colony possesses three branches 5-7 mm long from a common basal stalk. The whole colony is creamy white in ethanol. Polyps are 4.5-5.0 mm long, excluding tentacles, and 2.0 mm in diameter at their proximal part. Tentacles are 3.0-4.0 mm long and 0.3-0.5 mm wide at their proximal part.

Pinnules are arranged mostly in three rows along each side of the tentacles, leaving free median space along the oral side. This space is not always visible at the distal part of the longest tentacles. The number of rows of pinnules drops to two toward the proximal part of the tentacle, and occasionally, only a single row can be seen (Fig. 3 ). The outermost row usually includes 12-16 pinnules each, up to 0.23 mm long and 0.21 mm wide at the proximal part. Typically, no gap between pinnules exists, but in rare cases, a gap of approximately 0.05 mm is observed.

Sclerites are abundant in polyps and surface layers of stalk and branches but absent interior. Under light microscopy, two forms of sclerites are observed - simple platelets (Fig. 4A ) and spindles (Fig. 4B ). Platelets are brown-red and spindles transparent (Fig. 4 ) under transmitted illumination. Platelets look pale blue and spindles appear transparent under epi-illumination (Fig. 5 ).

Polyp sclerites.

Two forms of sclerites, simple platelets and spindles, are seen in polyps (Figs 6A, B , 7A, B ). Simple platelets are 0.016-0.021 mm long and 0.009-0.011 mm wide. Spindles, 0.035-0.049 mm long and 0.004-0.006 mm wide, display unique ends with pointed spear tips. Sclerite composition in tentacles (n = 124) is 7.3% simple platelets and 92.7% spindles. In the polyp body (n = 83), these proportions are 4.8% and 95.2%, respectively. Thus, the vast majority of sclerites are spindles. Some spindles have thorns on their surface.

Stalk and branch sclerites.

Two forms of sclerites, simple platelets and spindles, are also found in stalk and branches (Figs 6C, D , 7C, D ). Simple platelets, several with an indistinct median waist, are 0.017-0.021 mm long and 0.009-0.011 mm wide. Spindles are 0.038-0.049 mm long and 0.004-0.006 mm wide. All spindles are more or less bent. Sclerite composition in stalk (n = 104) is 7.7% simple platelets and 92.3% spindles. Thus, the vast majority of sclerites are spindles.

Microstructure of sclerites.

The platelets are composed of branched sinuous dendritic rods within the sclerite interior. SEM at 30,000-50,000 × magnification shows distal parts of rods that line up almost vertically and parallel to the surface (Fig. 8A, B ). The spindles are composed of fused grains with a granular appearance (Fig. 8C, D ). Fused grains also exist inside, which can be observed in cross-sections of broken spindles (Fig. 8E, F ). Both ends of the spindles are relatively smooth (Fig. 8G ). Thorns may form on the surface of spindles (Fig. 7 , red arrows indicate the thorn, Fig. 8D shows the thorn expansion).

Variation.

Two preserved paratypes (KBF-OA-00093, KBF-OA-00094) differ in size (Fig. 2B, C ). Both paratypes are smaller than the holotype (30 mm high, 15 mm wide of KBF-OA-00093, and 9-16 mm high, 6-9 mm wide of KBF-OA-00094). One paratype (KBF-OA-00094) does not branch but has two stalks connected at the bottom, although this specimen, accidentally, is broken into two pieces (Fig. 2C, D ). Tentacle size is 4.0 mm long and 0.5 mm wide for KBF-OA-00093 and 3.0 mm long and 0.5 mm wide for KBF-OA-00094 (Fig. 3C, D ). Paratypes display three rows of pinnules along each side of tentacles, consistent with the holotype. Pinnule numbers in the outermost row are 13-16 for KBF-OA-00093, and 12-14 for KBF-OA-00094, compared to 12-16 for the holotype. All paratypes have the two forms of sclerites as well as holotype (Fig. 9 , 10 ), and are similar in the composition. In all parts of all specimens, the vast majority of sclerites are spindles, with the percentages being approximately 83-94% (Table 2 ).

Locality.

The species is common in waters around Oshima Island, Miyazaki, Japan, at depths from 5 to 10 m. Specimens exist attached to the surface of rocks or rock debris.

Etymology.

Konohana is named after a goddess in Japanese mythology, “Konohanasakuya-hime” ( “hime” is “princess” in English). Her shrine is in Miyazaki Prefecture. The present study also proposes a standard Japanese name “konohana-umiazami” for X. konohana sp. nov. The specimen KBF-OA-00092 is designated as the standard specimen for this new Japanese name.

Remarks.

Most Xenia species have only ellipsoid platelets or spheroid sclerites ( Halász et al. 2019). Although only two species, X. membranacea Schenk, 1896 and X. depressa Kükenthal, 1909 have been reported to display rod-shaped sclerites in their original descriptions, this type of sclerite has not been found in the syntype of X. membranacea ( Halász et al. 2019), and X. depressa has never been re-described and the existence of the type materials are unknown. Therefore, we treated the existence of rod-shaped sclerites as either incorrect for X. membranacea or unverified for X. depressa in this study. On the other hand, X. konohana sp. nov. (= Xenia sp. 1 by Koido et al. 2019) has unique spindle sclerites in addition to ellipsoid platelets (Figs 4 - 10 ). This combination does not occur in other species in the genus. Moreover, it is clear that spindles are the majority sclerites in tentacles, polyp body and stalks for all three specimens (KBF-OA-00092 to KBF-OA-00094).

All three specimens (KBF-OA-00092 to KBF-OA-00094) were nearly identical in sclerite shape, size and composition of two types of sclerite forms (xeniid platelets and unique spindles), number of pinnules, and molecular phylogenetic position. Eight species of Xenia ( X. blumi Schenk, 1896, X. crassa Schenk, 1896, X. cylindrica Roxas 1933, X. fisheri Roxas, 1933, X. garciae Bourne, 1895, X. hicksoni Ashworth, 1899, X. ternatana Schenk, 1896, and X. viridis Schenk, 1896), which partly overlap with X. konohana sp. nov. in exhibiting platelet sclerites, 3-4 rows of pinnules and 12-23 outermost row of pinnules, are distinguishable by the absence of the specific sclerite form, "unique spindle" (Table 3 ). A variation of pinnules has been reported in many species in xeniid genera, and the number of pinnules is likely to be unreliable as a character to determine the species boundaries ( Halász et al. 2019; McFadden et al. 2017). Therefore, the information on sclerites is more important than ever as a character for identifying species boundaries.

Figures

Figure 2. Fixed specimens of Xenia konohana sp. nov. A holotype BF-OA- 00092 B paratype KBF-OA- 00093 C, D paratype KBF-OA- 00094. Scale bar: 10 mm.

Figure 3. Tentacles of Xenia konohana sp. nov. aboral (left) and oral sides (right) A schema of holotype KBF-OA- 00092: three rows (the number is shown in the upper-right) and 13 pinnules at the outermost row (the number is shown in the center) B holotype KBF-OA- 00092 C paratype KBF-OA- 00093 D paratype KBF-OA- 00094. Scale bar: 1 mm.

Figure 4. Light microscope images of sclerites in polyps of Xenia konohana sp. nov., holotype KBF-OA- 00092 A spindles B simple platelets.

Figure 5. Stereoscopic microscopes images of sclerites in polyps of Xenia konohana sp. nov., holotype KBF-OA- 00092 A spindles B simple platelets.

Figure 6. Scanning electron micrographs of platelets of Xenia konohana sp. nov., holotype KBF-OA- 0009 A in tentacles B in polyp body C in stalk surface D in branch surface. Scale bar: 0.010 mm.

Figure 7. Scanning electron micrographs of spindles of Xenia konohana sp. nov., holotype KBF-OA- 00092 A in tentacles B in polyp body C in stalk surface D in branch surface. Arrow indicates thorns on the surface of spindles. Scale bar: 0.010 mm.

Figure 8. Scanning electron micrographs of the surface of sclerites in tentacles of Xenia konohana sp. nov., holotype KBF-OA- 00092 A surface of platelets covered by minute papillae B broken platelets with radial dendritic rods C central surface of spindle covered by minute granular D thorns on the surface of spindles E broken spindle F close-up view of a broken spindle with fused grain G tip of a spindle. Scale bar: 0.001 mm.

Figure 9. Scanning electron micrographs of paratype (KBF-OA- 00093) of Xenia konohana sp. nov.: A platelets B spindles (arrow indicates thorns on the surface of spindles) C surface of platelets D central surface of spindle E tip surface of a spindle F thorns on the surface of spindles. Scale bar: 0.01 mm (A, B); 0.001 mm (C-F).

Figure 10. Scanning electron micrographs of paratype (KBF-OA- 00094) of Xenia konohana sp. nov.: A platelets B spindles (arrow indicates thorns on the surface of spindles) C surface of platelets D central surface of spindle E tip surface of a spindle F thorns on the surface of spindles. Scale bar: 0.01 mm (A, B); 0.001 mm (C-F).