Stichopathes desaturata, Terrana & Godefroid, 2024

Terrana, L., Rouzé, H., Opresko, D. M., Consortium, Under The Pole, Eeckhaut, I., Dubois, P., Hédouin, L. & Godefroid, M., 2024, Whip black corals (Antipatharia: Antipathidae: Stichopathes) of the Mesophotic Coral Ecosystem of Mo’orea (French Polynesia), with the description of a new species, Zootaxa 5486 (2), pp. 182-212 : 188-192

publication ID	https://doi.org/ 10.11646/zootaxa.5486.2.2
publication LSID	lsid:zoobank.org:pub:2CBD1AF5-1B48-4DD1-B3C7-E3BEAB4E7559
DOI	https://doi.org/10.5281/zenodo.13750756
persistent identifier	https://treatment.plazi.org/id/03B40C78-FFF4-FFB8-FF30-FB94FCE6B5DE
treatment provided by	Plazi
scientific name	Stichopathes desaturata
status	sp. nov.

Treatment

Stichopathes desaturata sp. nov. Terrana & Godefroid

( Figs 3–5 View FIGURE 3 View FIGURE 4 View FIGURE 5 )

Material examined. Entire colonies collected at 120m depth. Holotype: NHMT-R2E1001 . Paratypes: NHMT-R2E1002 ; NHMT-R2E1003 . Other specimens (colony pictures and genetics only, examined in the field by M. Godefroid): Stichopathes C38, Stichopathes C39, Stichopathes C41, Stichopathes C42.

Type locality. Mo’orea , French Polynesia, 120 m depth.

Diagnosis. Corallum unbranched, irregularly sinuous, basal diameter not exceeding 1 mm, reaching a dozen of cm in height, polyps 0.50–1.0 mm in transverse diameter, interpolypar space well defined up to 0.50 mm, 6–8 polyps per cm, polypar spines taller than abpolypar spines, polypar spines max 0.13 mm, perpendicular to corallum, conical, pointed tip, with round and/or elongated papillae on two thirds of the spine, abpolypar spines conical to triangular, inclined upwards, with the same ornamentation as the polypar spines.

Description of the holotype NHMT-R2E1001.

Thin skeleton 0.38 mm in basal diameter, distinctly tapering at the apex (0.21 mm in diameter at the terminal section). It is sinuous, irregularly contorted, but not forming any loop or coil ( Fig. 3 View FIGURE 3 , a). It measures ~ 22 cm in length and ~ 10 cm in height ( Fig. 3 View FIGURE 3 , a). The polyps are found in a single row, that can twist around the corallum ( Fig. 3 View FIGURE 3 , h–j). They measure 0.6–0.84 mm in transverse diameter, with 6–8 polyps/cm. When expanded, sagittal tentacles are long, almost transparent, and longer than the diameter of the corallum ( Fig. 3 View FIGURE 3 , i, j). Smaller polyps are sometimes inserted between two larger ones ( Fig. 3 View FIGURE 3 , i). Interpolypar space well defined 0.15–0.48 mm, on average 0.30 ± 0.08 mm ( Fig. 3 View FIGURE 3 , h). The spines along the corallum are all triangular on the abpolypar sides to conical on the polypar sides, the latter being taller ( Fig. 4 View FIGURE 4 , a–c). On growing sections of corallum, the spines tend to be laterally compressed ( Fig. 4 View FIGURE 4 , c). On every section, a spiral arrangement of the spines can be seen ( Fig. 4 View FIGURE 4 ). There are no secondary spines on any section ( Fig. 4 View FIGURE 4 ). There are 4 spines/mm in the apical and middle sections, and 7 spines/mm in the basal sections. In the latter, the spines measure 0.08–0.10 mm and have both rounded and elongated papillae on their surface ( Fig. 5 View FIGURE 5 , a). In the middle section, polypar spines are conical with a pointed tip, slightly compressed laterally, and stand almost perpendicular to the corallum ( Fig. 4 View FIGURE 4 , b; Fig. 5 View FIGURE 5 , b). Papillae are both rounded and elongated towards the tip of the spine, covering from two thirds of the spine to the whole surface. In some places they form small tubercles ( Fig. 5 View FIGURE 5 , b). They measure 0.08–0.10 mm and are spaced 0.28–0.37 mm apart ( Fig. 4 View FIGURE 4 , b; Fig. 5 View FIGURE 5 , b). The abpolypar spines are smaller and more conical than polypar spines. They are slightly inclined towards the apex of the corallum ( Fig. 4 View FIGURE 4 , b). They have the same ornamentation than polypar spines ( Fig. 5 View FIGURE 5 , e). They measure 0.05–0.07 mm and are spaced 0.24–0.37 mm apart. In the apical sections, the distal edge of the spines is slightly curved compared to middle and basal sections ( Fig. 4 View FIGURE 4 , c; Fig. 5 View FIGURE 5 , c, f), but they have the same ornamentation as those on the rest of the corallum. Large, round papillae are not totally protruding on some spines ( Fig. 5 View FIGURE 5 , c, f). The spines on the apical section measure 0.05–0.07 mm.

Description of the paratypes.

Specimen NHMT-R2 E1002 irregularly sinuous and contorted, 9 cm in height, basal diameter 0.43 mm, apical diameter 0.19 mm ( Fig. 3 View FIGURE 3 , d). Polyps 0.58–1.0 mm in transverse diameter, 7–8 per cm. Spine ornamentation, shape and sizes are similar to holotype, with 4 spines/mm in apical, middle and basal sections.

Specimen NHMT-R2E1003 irregularly sinuous and contorted, 12 cm in height, basal diameter 0.72 mm, apical diameter 0.14 mm ( Fig. 3 View FIGURE 3 , g). Polyps 0.51–0.58 mm in transverse diameter, 7–8 per cm. Spine ornamentation, shape and size mostly similar to holotype. However, basal spines just above the anchorage plate are pointed and spike-like ( Fig. 4 View FIGURE 4 , d). Abpolypar spines are smaller than polypar spines, triangular and inclined upwards. In the middle section of the stem, they measure 0.04–0.05 mm and are spaced 0.30–0.38 mm apart ( Fig. 4 View FIGURE 4 , e–f). In medial sections, polypar spines measure 0.11–0.13 mm ( Fig. 4 View FIGURE 4 , e–f). There are 4 spines/mm in apical and middle sections, and 5–6 spines/mm in basal section.

Taxonomic discussion. Based on ITS1 molecular data, the present species belongs to “ Stichopathes Clade A” as described by Bo et al. (2012), and comprising species collected in Indonesia at depths of 10–50 m. The genetic distance from the Indonesian specimen AMBA5 is within the intraspecific range of variability of Mo’orea specimens, suggesting that AMBA5 might be related to the present species.

The morphological features of the French Polynesian specimens closely match those described for the Indonesian specimens of Clade A. The clade is characterized by a thin spiral or contorted corallum with a diameter less than 1 mm ( Bo et al. 2012); in the Mo’orea specimens it does not exceed 0.72 mm at the base. None of the Mo’orea specimens have spirals, they all are irregularly sinuous, sometimes irregularly contorted as well. The polyps are small (0.5–0.6 mm for Indonesian specimens of Clade A, 0.5–1.0 mm for the Mo’orea specimens), with a well-defined interpolypar space (0.3–0.4 mm for Clade A, 0.15–0.5 mm here), with 7–8 polyps per cm, compared to 6–8 polyps per centimeter in this case. Indonesian specimens of Clade A have pointed triangular spines, laterally compressed, taller on the polypar side (0.2–0.25 mm) than the abpolypar side (0.05–0.1 mm). This is congruent with the spines analyzed here in Mo’orea specimens, which are slightly laterally compressed in the middle sections, but clearly laterally compressed in apical sections. Nonetheless, the spine sizes observed here are smaller than those reported for the Indonesian specimens of Clade A. The papillae for Indonesian specimens of Clade A are reported being sometimes in the form of marked rounded ridges, and homogeneously distributed on their surface, which corresponds to the ornamentation of the spines observed here in Mo’orea specimens; except that in the middle section, the papillae of the latter specimens are much more developed so that sometimes they almost form tubercles. No secondary spines are observed in any case. Both morphological and genetic evidence confirms that the present species is closely related to Antipathes grandis Verrill, 1928 ( Wagner et al. 2010; Gress et al. 2020). A. grandis has been described as having similar triangular spines, with rounded tubercles on their surface ( Gress et al. 2020). Among described species of Stichopathes , four species have been reported to have a thin corallum with triangular and papillose spines: S. contorta Thomson & Simpson, 1905 (originally from Ceylon); S. echinulata Brook, 1889 (originally from Mauritius, Fig. 6 View FIGURE 6 , a–c); S. occidentalis (Gray, 1860) (originally from the West Indies, Fig. 6 View FIGURE 6 , e), and S. variabilis van Pesch, 1914 (originally from the Indonesian islands, see Fig. 6 View FIGURE 6 , d and explanation of the type hereafter). Stichopathes contorta differs from the present specimens by having only slightly papillose spines with some having apical notches ( Thomson & Simpson 1905; unpublished observations of DMO, see taxonomic discussion of S. cf. contorta below), whereas they are clearly defined and almost tuberculated here and never notched. The type specimen of S. echinulata located in Natural History Museum (London, BM82.2.21.5, NHMUK) is reported as having a basal diameter of 2.5 mm, which is substantially larger than that of the Polynesian specimens. The spines are reported as being short, triangular, compressed, directed upwards, and arranged in spirals, but no mention is made about the ornamentation, except that they are similar to S. occidentalis . A reexamination of both a schizotype of S. echinulata (USNM 100371 from holotype BM82.2.21.5) and a schizotype of S. occidentalis (USNM 100386), as well as the description of S. occidentalis provided by Wagner et al. (2010) shows that the spine ornamentation is different between these species. The spines of S. echinulata are finely papillose, with minute papillae mostly elongated towards the tip of the spine ( Fig. 6 View FIGURE 6 , c), while those of S. occidentalis have papillae well formed, almost tuberculated ( Fig. 6 View FIGURE 6 , d and Wagner et al. 2010). Stichopathes occidentalis is recorded from the Atlantic Ocean and usually grows vertically ( Cordeiro et al. 2012; Sanchez et al. 2019). Finally, among the almost 200 specimens that van Pesch (1914) assigned to the species Stichopathes variabilis in five “varieties”, some colonies were reported to be irregularly sinuous with triangular papillose spines.

It should be noted than Van Pesch (1914) stated that S. variabilis was a new name for the specimen that Silberfeld (1909) identified as S. filiformis (Gray) ( Fig. 6 View FIGURE 6 , d). Within the five varieties that van Pesch described, none of them is identified as Stichopathes variabilis variabilis nor Stichopathes variabilis typica . Therefore, it is likely that the original specimen that Silberfeld (1909) identified as S. filiformis (Gray, 1868) must be considered as the type of S. variabilis variabilis ( Fig. 6 View FIGURE 6 , d).

Among the varieties described by van Pesch (1914) as having conical to triangular and papillose spines are the specimens belonging to “ Stichopathes variabilis var. asperispina ”. A total of 82 specimens were assigned to this name and were collected from 15 meters down to 567 meters depth ( van Pesch 1914) in Indonesian waters. Some are reported to be thin and irregularly sinuous. Van Pesch (1914) divided the variety asperispina into six groups depending on the collection site (see Table 2 View TABLE 2 for a comparison of the morphological traits of S. variabilis var. asperispina ). It is probable that the specimens included in this species and variety belong to different species, and that dredged fragments coming from different genera of branched species might have been misidentified as Stichopathes because the polyps were found in a single row. He reported that all the specimens assigned to this variety showed a great variability in their polyp morphology, which is now considered as an identification criterion for antipatharians. He stated that “The very diverging shape of the polyps is the best proof how cautious one should be in making use of the polypar structure and dimension as specific or even generic differences” ( van Pesch 1914), meaning that he did not take into account such polyp differences to separate species. Another example is the observation of very tall, papillose, needle-like spines in some specimens ( van Pesch 1914, Figs. 199–120) along with antler-like spines ( van Pesch 1914, Figs. 168, 171) which are usually found within myriopathids. Considering the large discrepancies between polypar spine size and shape, the polyp and tentacle size and shape, as well as the large depth distribution of the specimens, one cannot be confident with the identification of S. variabilis pending a careful reexamination of all of van Pesch’ specimens.

The only molecular data available to date for specimens presumably identified as S. variabilis by Miller et al. (2010) do not confirm a close relationship to S. desaturata . In conclusion, the Stichopathes species most closely related to the French Polynesian specimens to date is S. occidentalis , but the differences in the growth pattern of the corallum and ornamentation of the spines do not allow the inclusion of the present specimens into this species.

Etymology. The name is derived from the Latin saturo, meaning saturated, and the prefix de-, the negation, in reference to the hours of decompression stops that the technical divers had to do when the holotype was collected at 120 m depth during the scientific expedition of Under the Pole.