Antipathes, Pallas, 1766

Terrana, Lucas, Bo, Marzia, Opresko, Dennis M. & Eeckhaut, Igor, 2020, Shallow-water black corals (Cnidaria: Anthozoa: Hexacorallia: Antipatharia) from SW Madagascar, Zootaxa 4826 (1), pp. 1-62 : 20-22

Antipathes sp.

Fig. 12

Material examined. Soalara, 15 m. Entire colony, specimen INV.131338.

Depth range. 15–30 m.

Description. The living colony is bramble-like with the appearance of a mass of entangled and fused branches. It measures 25 cm in height and width in situ ( Fig. 12 , a, b). The terminal branchlets are straight to slightly curved and their end is very thin. Branchlets are inserted almost perpendicular to the next lower order branch, but more often at 70–80°, even if more acute angles are also found ( Fig. 12 , b). Branchlets are not regularly arranged nor in a single plane. They occur either uniserially or loosely biserially and are irregularly spaced 0.2–11 mm on the same side, with 3–5 branchlets per cm ( Fig. 12 , b). Terminal branchlets measure up to 5 cm with basal diameter of around 0.6 mm, but more often less than 2.5 cm ( Fig. 12 , b). Fusions are frequent between adjacent branches and branchlets. For instance, in a branch measuring 8 cm in length, 17 fusions are seen when considering all its branchlets (represented by the red dots in Fig. 12 , b). The polyps are located in a single row that can twist around the thin branches but are irregularly spread out on thicker branches. Polyps measure 0.5–0.6 mm in diameter and are spaced 0.2–0.8 mm apart (mostly 0.4–0.5 mm). There are 10-11 polyps per cm.

The spines are widely varying in shape depending on the branch where they sit but are always smooth. On a branch measuring 0.16 mm in diameter, the spines are conical, measure 0.04–0.07 mm, and are spaced 0.13–0.26 mm apart ( Fig. 12 , c). Most of them show two or more protuberances at the apex without distinction between polypar or abpolypar spines ( Fig. 12 , c, g). For some spines the protuberances are found close to the base of the spine, consequently the conical shape is no more distinct ( Fig. 12 , c). On such branches, four longitudinal rows are seen in one aspect ( Fig. 12 , c). On a branch measuring 0.36 mm in diameter ( Fig. 12 , d), the spines are either perpendicularly inserted or slightly inclined upward and 6–7 longitudinal rows are seen on lateral view. Most of them are conical ( Fig. 12 , h), although spines with protuberances are occasionally found ( Fig. 12 , d). Their size is the same as those of thinner branches, 0.04–0.07 mm, and they are spaced 0.22–0.36 mm apart. On larger branches measuring 0.5 mm ( Fig. 12 , e), only four longitudinal rows of spines are seen, and all of the spines are almost conical. They are slightly inclined but not in the same direction ( Fig. 12 , e, i). They measure 0.05–0.09 mm and are regularly spaced 0.19–0.37 mm apart, but often around 0.26 mm, giving the appearance of regular spacing. Finally, on branches measuring 0.80 mm in diameter the arrangement of the spines in longitudinal rows is no more visible ( Fig. 12 , f). The spines can be conical but most of them are hooked and inclined in different directions ( Fig. 12 , f, j). Their size remains constant as they measure 0.05–0.09 mm. Because they are not arranged in longitudinal rows, their mutual distance cannot be measured.

Taxonomic remarks. Currently, four valid species are known to be bramble-like: Antipathes chamaemorus Pax & Tischbierek, 1932 ; An. lenta Pourtalès, 1871 ; An. polyhedra Opresko, 2019 and An. rubusiformis Warner & Opresko, 2004 . Two other species, An. pauroclema Pax & Tischbierek, 1932 and An. simplex ( Schultze, 1896) could possibly be similar, but both are only known from fragments. Antipathes simplex is reported to have laterally compressed spines with rounded tips and inclined towards the end of the branch. They have a height of 0.085 mm on a branch 0.2 mm. Five to six longitudinal rows can be seen on one aspect, which becomes less distinct near the base of the corallum. Polyp transverse diameter has an average of 1 mm. Antipathes pauroclema is reported to have variable spine morphologies. On what Pax & Tischbierek (1932) call the middle part of the skeletal axis, the spines are measuring 0.1 mm on average. On the tip of the branchlets, the spines reach 0.06 mm. In the largest part of the colony they are blunt cone-shaped, on the twig tips they are curved sharply and apically. They are arranged in five longitudinal rows and spaced 0.2–0.25 mm apart. The polyps measure 1.15 mm. Considering the wide variation of the spine morphology, size and arrangement depending on the thickness of the branch seen in the present specimen, as well as the small fragments from which An. simplex and An. pauroclema have been described, the two latter species cannot be compared confidently. For the remaining bramble-like species, only An. chamaemorus and An. lenta have triangular, smooth spines, while An. rubusiformis has triangular and papillose spines and An. polyhedra has tall and narrow spines ( Opresko 2019). Antipathes chamaemorus differs from the present specimen by being a small colony not exceeding 3 cm in height, and in An. lenta no mention is made about the presence of spines with protuberences as seen in the present specimen.

Distribution. Madagascar (present study).

Figures

FIGURE 12. Antipathes sp. specimen INV.131338. (a) Colony photographed in situ. (b) Spread-out colony showing the curved branches and the arrangement of the branchlets. The red dots represent the fusion points of branchlets belonging to the branch indicated by the red arrow. (c) Section of a branch 0.16 mm in diameter. (d) Section of a branch 0.36 mm in diameter. (e) Section of a branch 0.50 mm in diameter. (f) Section of a branch 0.80 mm in diameter. (g–j) Shapes of the spines.