Sinularia arctium, Dautova, Tatyana N. & Savinkin, Oleg V., 2009

Dautova, Tatyana N. & Savinkin, Oleg V., 2009, New data on soft corals (Cnidaria: Octocorallia: Alcyonacea) from Nha Trang Bay, South China Sea, Zootaxa 2027, pp. 1-27 : 10-11

publication ID	https://doi.org/ 10.5281/zenodo.186181
DOI	https://doi.org/10.5281/zenodo.6221725
persistent identifier	https://treatment.plazi.org/id/B771771D-3622-391E-E894-FB36FBEBA5BB
treatment provided by	Plazi
scientific name	Sinularia arctium
status	sp. nov.

Treatment

Sinularia arctium View in CoL sp. nov.

( Figs. 8–15 View FIGURE 8 )

Material examined. Holotype: MIMB 16536, 1 specimen, 12° 16′ N, 109° 21.8′ E, 12 m, 11 Nov 2005, Dung Island, Nha Trang Bay, South China Sea, Vietnam, coll. T. N. Dautova.

Description. Living colonies are dish-shaped with lobed edges; some lobes are united into ridges which are placed radially on the outer part of disk. Some finger-like or lumpy lobes (up to 12 mm in height) can occur on the central part of disk ( Fig. 8 View FIGURE 8 ). The polyps cover the disk and lobes; they are also distributed on the lower surface of the disk but only near the edge, as a border 4–6 mm in width. The preserved holotype is funnel-shaped ( Fig. 9), 99.6 mm high. The lower surface of the disk and stalk surface are slightly grooved longitudinally.

Modified clubs and curved, slightly flattened, rods ( Fig. 10 View FIGURE 10 A) are arranged as points in the polyps. These triangular arrangements of sclerites occupy the lower part of the tentacles and the upper part of the neck zone. The polyp armature observations were carried out on semi-expanded polyps; collarets were not found.

The surface layer of the lobes contains clubs 0.07–0.32 mm long. Some of the small ones, mostly up to 0.12 mm long, approach the leptoclados -like club form, while others have a distinct central wart ( Fig. 10 View FIGURE 10 B). Their handles are tapered, straight or slightly curved, and ornamented with round tubercles. Other small clubs have complexly warted heads with notched tubercles and warty handles ( Fig. 10 View FIGURE 10 C). Long, curved-handled clubs, 0.15–0.32 mm in length, are also present. Some of them have a distinct central wart ( Fig. 11 View FIGURE 11 A), while others tend to have unordered processes on the heads ( Fig. 11 View FIGURE 11 B, a, b). The latter forms merge into club-like spindles. There are also numerous small spindles which vary from being relatively smooth to being thick with evenly distributed and complex warts ( Fig. 11 View FIGURE 11 B).

The stalk surface has similar sclerites to those of the lobe surface. Some small clubs approach the form of leptoclados -like clubs while others have a central wart and a tapered or blunt, robust handle ( Fig. 12 View FIGURE 12 A). Clubs with notched tubercles on their heads have an indistinct central wart and are more robust in comparison with the ones from the polypary. They have thick robust handles, which are sometimes forked, and are abundantly ornamented with well-developed warts ( Fig. 12 View FIGURE 12 A, a, b, c). They are similar to remarkably robust clubs, 0.3–0.57 mm long, with thick warty handles and heads ( Fig. 12 View FIGURE 12 B). Crosses are common. There are also clublike spindles and small spindles that vary from being thickened warty forms to thin forms with small conical processes ( Fig. 12 View FIGURE 12 C).

The spindles from the lobe interior are 0.8–3.3 mm in length, without median constriction ( Fig. 13 View FIGURE 13 ). They are sometimes curved or have concave sides, probably due to their compact placement in the lobes. The spindle warts may have flat summits or they may resemble granulated cones, which sometimes are transversely widened ( Fig. 13 View FIGURE 13 A). The spindle ends are slightly tapered ( Fig. 13 View FIGURE 13 B).

The warts on the stalk interior spindles mostly have flat summits ( Fig. 14 View FIGURE 14 A) but some small ones may be covered with granulated cones. Two size ranges of spindles may be observed here:

1. long spindles with tapering ends with or without a median waist ( Fig. 14 View FIGURE 14 B);

2. short, thick spindles with blunt rounded ends ( Fig. 14 View FIGURE 14 C) and no median waist.

Variability. No clear intra-colony variability in sclerite forms and sizes were found between the lobes and the central region of the polypary.

Coloration. The alcohol-fixed specimens are light brown. The living colonies are brown with colorless polyps.

Distribution. Nha Trang Bay (South China Sea, Vietnam).

Etymology. The specific name alludes to the external similarity of colony shape with leaves of the plants of the genus Arctium (Magnoliopsida: Asterales : Asteraceae ).

Remarks. The species may be considered as very close to four Sinularia species which were described by Alderslade & Shirwaiker (1991: 211-232, Figs. 20 View FIGURE 20 –48) from the Laccadives with respect to the leptoclados - like clubs with plump heads. However, S. arctium differs from all of them in both colony shape and sclerite form. S. jasminae has no sclerites in the polyps, has mostly small waisted spindles (0.33 mm long) in the upper part of the lobe interior, and has no clubs with long thin handles ( Alderslade & Shirwaiker 1991: 211–214, Figs. 21 View FIGURE 21 –23). S. parulekari has differently shaped sclerites in the polyps and lacks clubs with long handles ( Alderslade & Shirwaiker 1991: 217–218, Figs. 29–32). S. karavattiensis and S. gaveshaniae have clubs with quite long handles and clubs with radially divergent outgrowths on the heads, but have rodlets in polyp tentacles and different internal spindles ( Alderslade & Shirwaiker 1991: 219–229, Figs. 37–48). All of the 4 above mentioned species have no clubs with a distinct central wart. S. slieringsi Ofwegen & Vennam, 1994 is the only species which has similar colony shape to S. arctium , together with similar sclerite types in the lobe surface, including forms that approach leptoclados -like clubs. However, S. slieringsi has no curved spindles in the polyps and no leptoclados -like clubs with plump heads in the lobes surface ( Ofwegen & Vennam 1994: 152–158, Figs. 15–20 View FIGURE 15 View FIGURE 16 View FIGURE 17 View FIGURE 18 View FIGURE 19. S View FIGURE 20 ). The internal spindles of S. slieringsi are also different. S. verseveldti Ofwegen, 1996 has the similar shape of the preserved specimen. However, S. verseveldti contains leptoclados - type clubs along with theleptoclados-like clubs wart clubs in the lobe surface and capstans in the stalk surface (Ofwegen 1996: 210–211, Figs. 1–5 View FIGURE 1 View FIGURE 2 View FIGURE 3 View FIGURE 4 View FIGURE 5 ). Moreover, S. verseveldti differs from S. arctium having flat spiny rods in the polyp tentacles and the point sclerites of quite a different shape.