Cirrhipathes densiflora Silberfeld, 1909

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 : 27-30

Cirrhipathes densiflora Silberfeld, 1909

Figs. 15 , 16

Cirrhipathes densiflora Silberfeld 1909, p.19

Material examined. Distal fragments from four colonies, Toliara 18–24 m specimens INV.131352, INV.131368, INV.131374, INV.131376 .

Depth range. 10–30 m.

Description. Single stem colonies which are straight with some crooked parts ( Fig. 15 , a, b), or sinuous and contorted ( Fig. 15 , c, d). The apex that can form a small loop ( Fig. 15 , d, e). They measure up to 170 cm in length. The skeleton is thin and generally tapers from the base to the apex of the colony. The diameter of the stem of the analyzed specimens varies from 2.5 to 8.0 mm at the base, and ranges from 1.5 to 2.5 mm on the distal part of the colonies. The color of the coenenchyme varies from grey to yellow or brown, with the polyps being yellow, white or orange ( Fig. 15 , b–e). The polyps are located all around the stem in an irregular way, with 3–6 polyps per cm. In contorted colonies, they tend to gather on the same side, leaving one side of the colony partially without any polyps ( Fig. 15 , e). In the analyzed portions taken at more than 10 cm below the tip of the colony, the polyps measure 1.7–3.9 mm in transverse diameter with a mutual distance of zero when they sit next to each other, up to 6 mm. The oral cones are prominent and clearly visible when the polyps are expanded with the mouth appearing like a slit. Longitudinal and cross grooves are usually visible between the polyps ( Fig. 15 , e). Clusters of nematocysts are distinguished as white spots on the coenenchyme between polyps ( Fig. 15 , b).

The spines are either at a right angle to the corallum or slightly inclined in different directions ( Fig. 15 , f). Spines have different shapes, from subtriangular to conical ( Fig. 15 , g–k), however tall cylindrical spines tend to be more frequent in the polypar side of the contorted colony ( Fig. 15 , h, i). In any case, the spines are slightly papillose with a knobbed tip more or less defined ( Fig. 15 , g–l). Growing spines are sometimes visible as they are narrower and cylindrical in shape, or minute and triangular. Adjacent spines are sometimes found fused together at their base. They measure 0.13–0.29 mm and are spaced apart 0.19–0.80 mm. Between seven and ten longitudinal irregular rows of spines can be seen in distal portions of the colony, but the longitudinal arrangement tends to be lost on thicker parts ( Fig. 15 , f). On the contorted form, the abpolypar spines measure 0.13-0.28 mm and they are spaced 0.19-0.46 mm apart. The polypar spines measure 0.22-0.31 mm and their mutual distance is 0.16-0.72 mm.

Taxonomic remarks. This species was originally described by Silberfeld (1909) who stated that the colony was sinuous, with polyps in multiple rows measuring about 1 mm in diameter and 2 mm in height, rounded spines measuring 0.35 mm in height and inserted at a right angle to the corallum, and having smaller spines with acute tips. He reported seven longitudinal rows of spines seen from one aspect. Since this description, no record of this species has been published. Contorted colonies are typical of Ci. contorta van Pesch, 1910 . However, in his description van Pesch (1910) states that the colonies are so contorted that a colony measuring 1.5 m in length would fit into a “bottle of 20 cm ”. As seen in Ci. densiflora , the polyps are also gathered on one side of the axis, 10 to 12 of them found per cm. The spines are triangular, blunt or acute, and measure 0.11–0.15 mm, their mutual distance is around 0.52 mm. They are papillose, but no mention is made about the presence of any knobs at the apex. A reexamination of both type specimens of Ci. densiflora Silberfeld, 1909 (USNM 100475, Fig. 16 , a, c) and Ci. contorta van Pesch, 1910 (USNM 100414, Fig. 15 , b, d) confirmed that spines were very similar, but knobs are only found in Ci. densiflora ( Fig. 16 ).

In the present case, the Malagasy colony is also generally thicker than typical Ci. contorta , and with a more limited contortion of the corallum. In Madagascar, these knobs at the tip of the spines represent one of the main features to differentiate Ci. densiflora from Ci. anguina as the colonies can be very similar when observed in the field. Regionalization of spine size and ornamentation are common in contorted or spiral species. Contrary to straighter specimens of Cirrhipathes , the apical portion might slightly differ from a central or basal one, as well as between straight or looped segments. Cirrhipathes contorta has two categories of the size of spines: in loops and curves, polypar and abpolypar spines are markedly different, which is also the case in the contorted specimen (INV.131374) analyzed here. Examination of entire contorted colonies of non-type material in Indonesia revealed a gradient of spines, from simple to few apical knobs (pers. obs. MB). However, as seen previously, the type does not show distinct knobs –but this has not been analyzed for specimens from all regions. Environmental constraints may contort colonies of Ci. densiflora . Monitoring of transplanted colonies in Indonesia suggested that this possibility is not to be excluded ( Bo et al. 2009). Pending a revision of the Cirrhipathes group and the clarification of intra- and interspecific variability of contorted colonies in the same environments, importance should be given to spines and type material for identifications among genera and species. Therefore, the name Ci. densiflora is applied to the different phenotypes observed in Madagascar.

Distribution. Japan (type locality, Silberfeld 1909), Madagascar (present study).

Figures

FIGURE 15. Cirrhipathes densiflora Silberfeld, 1909. (a–e) In situ pictures showing the different phenotypes of the species (a—INV.131368; b—INV.131376; d/e—INV.131374). (f) Sections of the skeleton 1.8 mm in diameter (INV.131352), 2 mm in diameter (INV. 131376), 3.2 mm in diameter (INV.131368) and 2.5 mm in diameter (INV.131374), respectively. (g–i) Spines found on the contorted morphotype (INV.131374, conical polypar spines in (d), cylindrical abpolypar spines in (e, f). (j–k) Spines found on the whip morphotypes (INV.131368, INV.131376). (l) Detailed view of the tubercles at the tip of the spine.

FIGURE 16. (a, c) Cirrhipathes densiflora Silberfeld, 1909 type specimen (schizotype USNM 100475) from Japan. (b, d) Cirrhipathes contorta van Pesch, 1910 type specimen (schizotype USNM 100414) from Indonesia.