Antipathes cf. virgata Esper, 1788

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 : 18-20

Antipathes cf. virgata Esper, 1788

Figs. 10 , 11

Antipathes virgata Esper, 1788 , pt. II, p. 8, pl. XIV

Antipathes scoparia Lamarck , t. II, p. 307

Material examined. Toliara, 25 m. Distal branches of different diameters, specimen INV.131349 .

Depth range. 25–45 m.

Description. A branched and bushy colony measuring 75 cm in height with a basal diameter of 1.5 cm ( Fig. 10 , a–c). The branches subdivide pseudo-dichotomously and are vertically elongated and almost parallel, being inserted with an acute angle to the thicker branch ( Fig. 10 , b, c). On the distal thick branches, smaller branches often originate from the same area and from different sides, giving the colony the general shape of a candelabra ( Fig. 10 , c). There is no fusion between adjacent branches ( Fig. 10 , c), but sometimes vertically erected branches can fuse with the main axis when they come in contact. In the upper part of the colony, the terminal branchlets measure up to 9 cm in length. Such branchlets measure around 2 mm in diameter at their base (measured with the tissues), while a shorter branchlet 5.8 cm in length measures 1.2 mm at the base (measured with the tissues). The polyps are generally found in one row, but on branches they are often arranged on both sides giving the appearance of two rows ( Fig. 10 , c). When they are arranged in a single row, they can twist around the branch. On thicker axes, they are found all around the axis. Polyps appear large with thick and rounded tentacles and measure 1.0– 1.7 mm in diameter. The interpolypar space is not uniform; the polyps can be close together or be spaced up to 1 mm apart, and 8–9 polyps are found along one cm. The spines are conical, sometimes slightly hooked upwards on thin branches and inclined distally on thicker branches ( Fig. 10 , d–i). Spines have papillae on two-thirds of their surface on every side and multiple, rounded knobs at the apex ( Fig. 10 , g–i). Spines can also be stout with a flattened and knobbed apex on larger branches ( Fig. 10 , i). The number of longitudinal rows that can be seen from one aspect varies between five and seven. The polypar and abpolypar spines are equivalent in size, regardless of branch thickness. On all branches measuring less than 0.75 mm in diameter, the spines are consistently no more than 0.14 mm tall, whereas on thicker branches they measure 0.11–0.17 mm. The overall mutual distance is consistently within the range of 0.31 to 0.56 mm.

Taxonomic remarks. Historically, there have been several descriptions of Antipathes virgata referring to specimens coming from different locations and presenting different states of preservation. The original description of the species was made by Esper (1798, Fig. 11 , a) who described a specimen coming from the Indian Ocean that he received as a gift from India. That specimen is lost. In his description, he stated that the specimen could be “distinguished from any known species by the spreading of its branches and twigs, as well as its growth form”. He also reported about a stem expanding in a “fork-like” shape and branches originating from the same angle, but no details were provided regarding the polyps or the morphology of the spines. In the absence of the type specimen and given the lack of information about taxonomical features, his description is inadequate to define the species ( Opresko & Baron-Szabo 2001). Other specimens were then described by Brook (1889, from the Persian Gulf, redescribed by Opresko in 1974, see Fig. 11 , d–f), Roule (1905, from the Atlantic Ocean) and Forster Cooper (1909, from Saint-Brandon) which have been later compared by Opresko & Baron-Szabo (2001) in their redescription of Esper’s specimens. The latter authors concluded that it was not possible to determine if all these specimens referred to An. virgata were identical with the one described by Esper, and that it was questionable whether all three authors were dealing with the same species. In any case, a neotype needs to be designated for the species. Although the spines of the present specimen are similar in shape and size as those described from Brook’s specimen ( Brook 1889; Opresko & Baron-Szabo 2001, see Figs. 10 , 11 ), they differ in their fine morphology: the spines of the Malagasy specimen are papillose with many small knobs at their tips, while those of Brook’s specimen are smooth with a few large tubercles at their tips ( Figs. 10 , 11 ). The branching pattern also appears to be different ( Fig. 11 , b, d–f). In Brook’s specimen, the branches are mostly on one side of the axis, and they can be bifurcated before twisting and becoming confluent again ( Fig. 11 , d–e). These features are not observed here. Forster Cooper (1909) also reported about different morphological features with branches becoming confluent and fusing together at some point, as well as polyps arranged in four rows along the branch and sharp, triangular spines. The original illustration given by Esper (1798, Fig. 11 , a) shows a similar branching pattern for the whole colony, however, given all the previous considerations and the different localities, this specimen might be different from those of Brook (1889), Roule (1905) and Forster Cooper (1909), and the name An. cf. virgata is used here.

Distribution. Indian Ocean (type locality, Esper 1798), Persian Gulf ( Brook 1889), Cargados Carajos (archipelago of Saint-Brandon, Forster Cooper 1909), Azores, Madeira and Cape Verde ( Roule 1905), Madagascar (present study).

Figures

FIGURE 10. Antipathes cf. virgata sensu Esper, 1788 specimen INV.131349. (a) Entire colony. (b–c) Close-up views of the branching pattern and the polyps. (d) Section of a branch 0.35 mm in diameter. The polypar side is on the right. (e) Section of a branch 0.74 mm in diameter. The polypar side is on the right. (f) Section of a branch 1 mm in diameter. Polyps are found on both sides on this branch. (g) Polypar spine on a branch 0.60 mm in diameter. (h) Abpolypar spine on the same branch. (i) Example of a stout polypar spine on a branch 0.70 mm in diameter.

FIGURE 11. Comparison of Antipathes virgata Esper, 1788 and related specimens. (a) Original illustration of An. virgata by Esper (Esper Fortsetzungen 2, p. 8, pl. 14, 1798) showing the lower portion of the colony. The colony is from the Indian Ocean (gift from India). He reports a colony measuring around 45 cm with no fusion of the branches. (b) A branch of the specimen An. cf. virgata INV.131349. from Madagascar. (c) A branch of the specimen An. cf. lentipinna INV.131337 from Madagascar showing the same uniserial branching pattern as Brook’s specimen of An. virgata, but with thick ramifications compared to the latter. (d–f) Views of the entire colony, a branch and a skeletal section of Brook’s specimen (Brook 1889) of An. virgata from the British Museum. The ramifications are uniserial and thin compared to the specimen from Madagascar. Photo of Brook’s specimen of An. virgata courtesy of Paul Richens of the NHMUK.