Antipathes

Diagnosis. Corallum sparsely to densely branched; bushy or flabellate; rarely monopodial. Branchlets of varying length; arranged irregularly, or bilaterally; rarely pinnulate. Spines usually triangular to conical in lateral view, smooth or papillose; often laterally compressed; sometimes with knobs or multiple forking at the apex. Polyps from about 1 to 3 mm in transverse diameter, sometimes longer along the sagittal axis than along the tranverse axis.

Remarks. Although many species formerly referred to Antipathes have now been reassigned to other genera in two newly established families (Myriopathidae and Aphanipathidae), the genus still contains species of very diverse morphology. It is likely that with further taxonomic revisions species in this genus will be recategorized, primarily on the basis of the morphology of the polyps and on the growth form of the corallum, and, it is quite possible that some species now assigned to Antipathes may be removed from the family.

Type species. Antipathes dichotoma Pallas, 1766. Type material. A neotype has recently been established for Antipathes dichotoma (see Opresko 2003 b). The type species is characterized by having relatively large polyps (up to 2 mm in transverse diameter), a rather sparsely and irregularly branched corallum, and large, smooth spines.

Diagnosis (after Opresko 2019). Corallum sparsely to densely branched. Branching bushy, bramble-like, broomlike, or fan-shaped. Terminal branchlets of varying length; arranged irregularly, or bilaterally. Spines triangular or cone-shaped in lateral view; smooth or papillose; apex of spines simple or with one or more lobes or bifurcations. Polyps less than 1 mm in transverse diameter.

Remarks. Antipathes dichotoma is the type species of the Antipathidae; however, molecular studies (Bo et al. 2018; Brugler et al. 2013), including this study (Fig. 2), have found that the species is more closely related to species in the Aphanipathidae than the Antipathidae. A formal review with integrated morphological and molecular data of all species in each family is required to resolve this taxonomic issue.

Type Locality. Mediterranean Sea

Type Species. Antipathes dichotoma Pallas, 1766

The genus Antipathes is the first to have been established (Pallas 1766). It is characterized by colonies that are branched, bramble-like, bushy or fan-shaped (Opresko 1972, 1974). The branches are not pinnulate and the polyps occur in a single row on smaller branches. The spines can be smooth or papillose, simple or forked, multilobed or knobbed at the apex. There are currently about 70 nominal species (Opresko 2019), 36 from the Pacific and Indian Oceans, out of which 13 have their type species lost. New species are still being described, which is why it is difficult to determine the exact number of species belonging in the genus Antipathes.

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.

Depth range. 15 – 30 m.

Fig. 12

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).

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

Diagnosis. Corallum sparsely to densely branched. Branching bushy, bramble-like, broom-like or fan-shaped. End-branchlets of varying length; arranged irregularly, or bilaterally. Spines triangular or cone-shaped in lateral view; smooth or covered, to varying degrees, with small papillae; apex of spines simple or with one or more lobes or bifurcations. Polyps from less than 1 to 3 mm in transverse diameter.

Remarks. The genus contains a large number of nominal species. DNA studies (Brugler et al. 2013; Bo et al. 2019) suggest that it might be subdivided on the basis of whether the spines are smooth-surfaced or have distinct papillae and whether they are simple, forked or multiply lobbed at the apex. Species are usually differentiated by colony morphology, as well as size, shape, and surface ornamentation of the skeletal spines.

Distribution. The genus is known primarily from tropical and subtropical waters in all oceans; usually at depths less than 200 m. However, some species may occur much deeper.

Type species. Antipathes dichotoma Pallas, 1766 (see Opresko 2003: 481 – 493).

Diagnosis. Corallum sparsely to densely branched; bushy or flabellate, rarely monopodial. Branches variable in length, irregularly disposed or bilaterally, but never pinnulated. Spines usually triangular to conical in side view, smooth or papillose; frequently laterally compressed; apex multilobate or bifurcated. Polyps 1 to 3 mm in diameter, sometimes elongate in saggital axis in relation to the transverse axis (adapted from Opresko, 2005 and Brugler et al., 2013).

Distribution. Atlantic, Indian and Pacific Oceans (Opresko, 2003; Opresko, 2005; Opresko & Sanchez, 2005).

Type-species. Antipathes dichotoma Pallas, 1766 (by subsequent designation: Brook, 1889).