Stichopathes spp.

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 : 198-209

Stichopathes spp. Clade C

The specimens from Mo’orea described below are all grouped within the Clade C previously defined by Bo et al. (2012). Each morphotype encountered is described below ( Figs. 10–13 ). Data are summarized in Table 3 .

Material examined. Stichopathes sp. NHMT-R2 E1007, 70–100 m depth, SEM stub of middle part; NHMT-R2 E100, 70–100 m depth, SEM stub of middle part ; NHMT-R2 E1009, 70–100 m depth, SEM stub of middle part ; NHMT-R2 E1010, 70–100 m depth, SEM stub of middle part ; NHMT-R2 E1011, 70–100 m depth, SEM stub of middle part ; NHMT-R2 E1012, 70–100 m depth, entire colony in 70% ethanol, SEM stubs of basal, middle and apical parts ; NHMT-R2 E1013, 70–100 m depth, SEM stub of middle part ; NHMT-R2 E1014, 70–100 m depth, SEM stub of middle part ; NHMT-R2 E 1015, 120 m depth, two middle fragments of around 3cm each in 70% ethanol, SEM stubs of basal, middle and apical parts .

Descriptions.

Stichopathes sp. NHMT-R 2E1007 ( Fig. 11 , a–d). The colony extends vertically, irregularly sinuous, and measures 14.6 cm in height and 16.5 cm in length. The corallum is tapering, it measures 2.25 mm, 1.62 mm and 0.85 mm in the basal, middle and apical sections, respectively. Polyps are found in a single row and measure 1 mm in transverse diameter. The interpolypar space was not measured, but on pictures polyps are crowded and sit close to each other. There are 6–8 polyps per cm, mostly 7. The spines are arranged in 8 longitudinal rows, with 3 spines/ mm. Polypar spines are tall, cylindrical and narrow, with the tip being large and rounded, larger than the spine itself; they measure 0.23–0.29 mm and are spaced 0.36–0.60 mm apart. They stand at right angle to the corallum. The whole spine –tip included– is covered by papillae, grown to a point that they almost form tubercles, varying in size and shape, some being rounded, some being extended towards the tip of the spine. Their distribution is irregular, and some spaces are left without papillae. At the enlarged tip, there are tubercles on both distal and proximal sides of the spine. The abpolypar spines are small, stout, and conical; they measure 0.1–0.15 mm and are spaced 0.33–0.60 mm apart. They stand at right angle to the corallum. On the middle of their surface, they are covered with faint papillae elongated towards the tip, almost looking like ridges. On the first third of their surface, the papillae are well formed and are rounded in varying sizes. Small tubercles are present at the tip. There are small secondary spines (with or without papillae) that appear to be more abundant on the abpolypar side on the middle section analyzed.

Stichopathes sp. NHMT-R 2E1008 ( Fig. 11 , e–h). The colony extends vertically, irregularly sinuous, measures 20 cm in height and 28 cm in length. The corallum is very slightly tapering, it measures 2.0 mm, 1.70 mm and 1.35 mm in the basal, middle and apical sections, respectively. Polyps are found in a single row and measure 1.0– 1.2 mm in transverse diameter. The interpolypar space was not measured, but on pictures polyps are crowded and sit close to each other. There are 6–8 polyps per cm. The longitudinal arrangement of the spines is not well defined and is closer to a spiral arrangement, but there are 2–3 spines/mm. The polypar spines are cylindrical and narrow. They are slightly inclined towards the apex of the colony. Their surface is covered by small, rounded papillae. The tip of the spine is tuberculated, 8 tubercles are seen on Fig. 11 , g. One tubercle is also present on the distal side of the spine. The polypar spines measure 0.18–0.36 mm and are spaced 0.36–0.87 mm apart. Abpolypar spines are small and conical; they measure 0.16–0.26 mm and are spaced 0.34–0.88 mm apart. Their distal edge is at right angle to the corallum while their proximal edge is inclined towards the apex of the colony. They are covered by small papillae, varying in size and shape, with the smallest and roundest located near the tip, while the largest and most elongated are located below. The tip of the abpolypar spines has small, almost flat tubercles, five are counted on Fig. 11 , h. Small secondary spines (with papillae or not) are present and sparsely distributed.

Stichopathes sp. NHMT-R 2E1009 ( Fig. 11 , i–l). The colony is growing vertically and is almost straight. It measures 24 cm in height and 25 cm in length. The corallum is thin, measures 1.43 mm at the base, 1 mm in the middle section analyzed and 0.85 mm in the apical part. Polyps are found in a single row and measure 1.1–1.5 mm in transverse diameter. There are 6–7 polyps per cm, mostly 7. The interpolypar space was not measured, but on pictures polyps are crowded and sit close to each other. The spines are arranged in 6–7 longitudinal rows, although they are not well defined, with 3 spines/mm. The polypar spines are tall, conical, and stout; they measure 0.28–0.39 mm and are spaced 0.36–0.73 mm apart. They stand at right angle to the corallum. The first third at the tip is covered by large tubercles, extending on the distal and lateral sides of the spine. Around 18 are counted on Fig. 11 , k. Rounded papillae are found below, with small, sparse, elongated papillae near the base of the spine. Abpolypar spines are smaller, stout, conical, with a flat or rounded tip; they measure 0.08–0.16 mm and are spaced 0.22–0.74 mm apart. They are covered by well-formed rounded papillae on almost their entire surface. Near the base faint elongated papillae almost form ridges. Small secondary spines (with or without papillae) are present and are located on the abpolypar side of the middle section analyzed.

Stichopathes sp. NHMT-R 2E1010 ( Fig. 12 , a–d). The colony is sinuous with an irregular growing pattern, it measures 35 cm in height and 70 cm in length. It forms two loops located at around 12 and 18 cm from the base, with diameters of around 2 and 3 cm. The skeleton is around 2.5 mm in diameter at the base, but thickness is not constant along the corallum, with thick and thin sections alternating towards the apex. The middle section analyzed measures 0.76 mm. The apical section measures 1.1 mm. Polyps are found in a single row and measure 1.3–1.7 mm in diameter. There are 5–7 polyps per cm, mostly 5. The interpolypar space was not measured, but on pictures polyps are crowded and sit close to each other. The spines are clearly arranged in quincunx in seven longitudinal rows with 2 spines/mm. The polypar spines are tall, conical, inclined distally, and laterally compressed; they measure 0.24–0.34 mm and are spaced 0.34–0.56 mm apart. They are covered by minute rounded papillae on almost their whole surface. The tip of the spine is tuberculated, five tubercles are counted in Fig. 12 , c. The lateral tubercles are arranged in a circle around the tip of the spine, forming ridges. Abpolypar spines are smaller, triangular, with the distal edge at right angle to the corallum and the proximal edge inclined towards the apex. They are also covered by small, rounded papillae and their tip is acute. They measure 0.11–0.19 mm and are spaced 0.58–0.90 mm apart. Small, secondary spines (with papillae or not) are present and located on the abpolypar side of the middle section analyzed.

Stichopathes sp. NHMT-R 2E1011 ( Fig. 12 , e–h). The colony is very sinuous with an irregular growing pattern, it measures 26 cm in height and 42 cm in length. It forms one loop, located at around 2 cm from the apical part, measuring around 1.5 cm in diameter. The skeleton is around 2.4 mm in diameter at the base, but thickness is not constant along the corallum, with thick and thin sections alternating towards the apex. The middle section analyzed measures 1.26 mm in diameter, the apical section 1.0 mm. Polyps are found in a single row and measure 1.0– 1.14 mm in diameter. There are 6–7 polyps per cm. The interpolypar space was not measured, but on pictures polyps are crowded and sit close to each other. The spines are clearly arranged in quincunx in 7 longitudinal rows with 2–3 spines/mm. The polypar spines are tall, conical and stand at right angle to the corallum; they measure 0.20–0.26 mm and are spaced 0.37–0.86 mm apart. They are laterally compressed and covered by small papillae that are rounded near the tip of the spine and elongated on the rest of the surface. The tip is tuberculated, mostly five tubercles are seen. The abpolypar spines are smaller, triangular to conical, the distal edge stands at right angle to the corallum while the proximal edge is inclined towards the apex of the colony. Their surface is covered by faint elongated or rounded papillae. Their tip is mostly acute but with small tubercles. They measure 0.11–0.17 mm and are spaced 0.33–0.93 mm apart. There are no secondary spines on the middle fragment analyzed.

Stichopathes sp. NHMT-R 2E1012 ( Fig. 12 , i–l). The colony is thin and tapering. It starts to grow vertically before going horizontal and forming a curve downwards. It measures 41 cm in height and 62 cm in length. The basal diameter is 1.5 mm, the middle section analyzed is 1 mm and the apical section is 0.44 mm. Polyps are found in a single row and measure 0.79–1.16 mm in transverse diameter. There are 5–8 polyps per cm, mostly 8. The interpolypar space was not measured but on pictures polyps sit close next to each other, without a significant interpolypar space. On the middle section, the spines are spirally distributed, but one may distinguish 8–9 longitudinal rows, and 2–3 spines/mm as in the apical section. In basal section, there are 3–4 spines/mm. The polypar spines are conical, with large, rounded papillae on two thirds of the surface, and elongated papillae on the lowermost part of the surface. The tip is tuberculated, and protuberance of the tubercles varies along the section. The polypar spines measure 0.11–0.16 mm and are spaced 0.40–1.2 mm. The abpolypar spines are triangular to conical, with large, rounded papillae on their surface. Their distal edge stands at right angle to the corallum while their proximal edge is inclined towards the apex of the colony. Their tip is slightly tuberculated. They measure 0.08–0.13 mm and are spaced 0.30–0.70 mm apart. There are numerous small secondary spines (with papillae or not) regularly distributed on the surface of the corallum.

Stichopathes sp. NHMT-R 2E1013 ( Fig. 13 , a–d). The colony is thick, sinuous, not tapering. It measures 24 cm in height and 52 cm in length. It forms four loops at around 13 and 16 cm from the base, and two consecutive at 20 cm from the base. The basal diameter is 4 mm and is not constant along the corallum, as it is thicker on some sections. The middle section analyzed is 2 mm in diameter and the apical section 1.25 mm. Polyps are found in a single row and measure 1.0– 1.3 mm in transverse diameter. There are 5–8 polyps per cm, mostly 5–6. The interpolypar space was not measured but on pictures polyps are crowded and directly next to each other, to a point that they look compressed. On the middle section analyzed, the spines are irregularly distributed, with 2–3 spines/ mm. The polypar spines are tall, cylindrical, with the tip being rounded and larger than the spine itself and covered in tubercles in all directions. They stand at right angle to the corallum. The surface is covered by numerous rounded papillae below the tip. They measure 0.44–0.51 mm and are spaced 0.34–0.69 mm apart. The abpolypar spines are smaller, conical, with a rounded tip, and distally inclined. The tip has small, faint tubercles. Their surface is covered by rounded papillae. They measure 0.13–0.21 mm and are spaced 0.24–0.56 mm apart. There are numerous small, pointed, papillose or smooth, secondary spines regularly distributed all around the corallum.

Stichopathes sp. NHMT-R 2E1014 ( Fig. 13 , e–h). The colony is in a tight helicospiral pattern, with the spirals stretched upwards, not tapering. It measures 30 cm in height with a basal diameter of 2.3 mm. The middle section analyzed is 1.5 mm in diameter and the apical section has the same diameter. The polyps are found in one row that twist around the corallum, following the helicospirals, and always located on the outer side of the latter. They measure 1.11–1.28 mm in diameter. The interpolypar space was not measured but on the pictures the polyps are sitting next to each other without a significant space between them. The polyp density per centimeter is hard to measure due to the narrow twist of the polyps around the corallum, but when looking at one twist from one aspect, 4–5 polyps are found on the visible side of the polyps before they twist, this side measures 5 mm in length. The spines on the middle sections are arranged in spirals, and polypar spines twisting around the corallum are clearly seen, with 2–3 spines/mm ( Fig. 13 , f). The polypar spines are tall, narrow, cylindrical, and stand at right angle to the corallum. They are covered by small, faint papillae, which are elongated towards the tip of the spine on two thirds of their surface, and more rounded close to the tip. The tip of the spine is tuberculated and some polypar spines have a ridge on their surface, mostly on their distal side. They measure 0.32–0.48 mm and are spaced 0.45–0.89 mm apart. The abpolypar spines are triangular to conical, slightly inclined upwards, and have either a pointed tip or a notched tip; they measure 0.14–0.22 mm and are spaced 0.39–0.72 mm apart. Their surface is covered by elongated papillae, which are rounded close to the tip. On the middle section analyzed, only a few secondary spines are seen.

Stichopathes sp. NHMT-R 2E1015 ( Fig. 13 , i–l). The colony is thin, small, and simple, it measures 6.5 cm in height and 14 cm in length. It extends vertically until around 5 cm in height then bends and grows horizontally and slightly tapers. The basal diameter is 0.77 mm, the middle section analyzed is 0.74 mm and the apical section is 0.40 mm. The polyps are found in one row. They measure 0.72–1.35 mm and are spaced 0.29–0.60 mm. There are 7–9 polyps per cm. The spines on the middle section are arranged in quincunx, a spiral arrangement may be seen or 7–8 longitudinal rows, with 2–3 spines/mm from apical to basal sections. The polypar spines are conical, stout, and stand at right angle to the corallum. They are covered by small, elongated papillae on the lowest part of their surface, and rounded papillae close to the tip. The tip of the spine is tuberculated at various degrees, each tubercle bearing large, rounded papillae as well. The polypar spines measure 0.19–0.26 mm and are spaced 0.44–0.67 mm apart. Abpolypar spines are smaller, conical, stout, and stand at right angle to the corallum. They are covered by small papillae, elongated near the base, and rounded near the tip of the spine. The tip is flattened and composed of small tubercles. They measure 0.15–0.23 mm and are spaced 0.48–0.67 mm apart. Small, pointed secondary spines (papillose or not) are sparsely distributed along the corallum.

Taxonomic discussion. The genetic distance of Clade C was greatest with Clade A (17.24 ± 2.32 %) and smallest with Clade D (8.76 ± 1.40%). Specimens of Clade D share similarities with Clade C by having tubercles on their spines as well as the presence of secondary spines ( Bo et al. 2012). Clade C is also the one which presents the greatest genetic distance within the clade (6.76 ± 0.6%) when considering all the specimens included in the phylogenetic tree ( Fig. 2 ), meaning that species divergence is more important within this clade than in others.

Clade C was originally characterized by a thick corallum, reaching up to 50 cm long, with tight helicoidal coils and a stem of more than 3 mm in diameter in the apical portion ( Bo et al. 2012). The polyps of the Indonesian specimens assigned to this clade measure 0.8–1.2 mm in diameter and are closely arranged on the external side of the coils. They tend to be sagittally compressed and crowded without any significant interpolypar space. The primary spines measure 0.45–0.60 mm with small tubercles mainly aggregated on the apex, with papillae below. The abpolypar spines are smaller, 0.15–0.18 mm high, more triangular and less tuberculated. It is mentioned that secondary spines are sparse and varying in density depending on the portion considered ( Bo et al. 2012). The Mo’orea specimens have morphological traits very close to those described for Indonesian specimens representing Clade C, especially for spine shape and ornamentation, polyp size and shape, abpolypar spine size and shape, and the presence and distribution of secondary spines. The only noticeable exceptions are the thickness of the apical section of the corallum, which never reaches 3 mm in the Polynesian specimens, along with the shape of the colony which is never perfectly helicoidal in Mo’orea specimens, and the smaller size of the polypar spines (0.11–0.51 mm for the nine morphotypes described here). These differences extend the general features of the Stichopathes Clade C, which was originally thought to be represented by perfectly spiral colonies. Here, the nine morphotypes have very different types of corallum morphology and stem thickness. Sometimes, there is a significant variation in corallum diameter across the length of the corallum, in the same fashion that has been called “spindle-shaped” by van Pesch (1914) in his description of Stichopathes variabilis .

It is well known that numerous ecotypes are found in some species of antipatharians, depending on environmental factors such as hydrodynamic conditions, presence of symbionts, events of breakage, or the orientation of the colony (growing on a crevasse, on a wall or on a horizontal substrate). These ecotypes might vary in diameter of the stem and/or coils, shape of the corallum, branch density and branching pattern, and size and shape of the spines. It is known that within unbranched antipatharians, the shape of the spine and the tubercle density may vary on sections of the stem having different diameters. However, the polyp size and shape and the ornamentation of the spines are morphological traits that tend to remain conserved within species ( Opresko et al. 2021).

If we consider the general characters of the spine ornamentation of the nine Polynesian specimens (i.e. presence of both elongated and rounded papillae, and tubercles at the tip of the spines), independently of their degree of expression (i.e. faint or protruding papillae, small or large tubercles), all of them share the same traits. Regarding the presence of secondary spines, all specimens possessed these spines to varying degrees, except for Stichopathes sp. NHMT R 2E1011 where none was seen. The absence of secondary spines in the middle section of the latter specimen analyzed might be a coincidence, since secondary spines can be very sparse on some sections. To date, it is not clear if the abundance and density of these secondary spines might be considered as ecological and/or intraspecific variations. Stichopathes sp. NHMT-R 2E1013 ( Fig. 13 , a–d) was the most remarkable with the highest abundance of secondary spines, densely distributed on the whole middle section analyzed. It is also the specimen with the thickest corallum, and the most loops and circumvolutions.

The general shape and growing pattern (including stem thickness) are probably the most plastic phenotypic characters among black corals because they depend on the environmental factors previously cited along with the age of the colony. In the nine morphotypes analyzed, three main types of colony shape can be distinguished: (i) thin, straight and/or bent; (ii) thick, irregularly sinuous, forming loops or not; and (iii) tight, stretched helicospirals. The first group is represented by specimens NHMT-R2 E1012 and NHMT-R2 E1015. They have a thin diameter at their base (less than 1.5 mm) and both have polyps in a similar size range, which is smaller than that of other morphotypes ( Table 3 ). Their polypar spines are more conical/triangular and stout than other specimens. However, there are significant differences in spine size ranges and mutual distances between both specimens, the spines of specimen NHMT-R2 E1015 being taller than those of NHMT-R2 E1012 ( Table 3 ). In addition, tentacles of polyps of specimen NHMT-R2 E1012 tend to be narrower than those of NHMT-R2 E1015, with cross-grooves clearly visible ( Fig. 14 ), while tentacles of C62 are thick and rounded, heavily built ( Fig. 14 ). Genetic distances are relatively important between both specimens, reaching>18% between some haplotypes. Considering these differences, these specimens might be considered as different species.

The second group with an irregularly sinuous corallums is composed of specimens NHMT R 2E1056, NHMT R 2E1065, NHMT R 2E1009, NHMT R 2E1010, NHMT R 2E1011 and NHMT R 2E1013. They all share a basal diameter> 1 mm, similar polyp ranges and density (slightly larger sizes in NHMT-R 2E1010 and NHMT-R 2E1011), and similar spine sizes and mutual distances, with the exception of specimen NHMT R 2E1013. The latter is significantly distinguished from the others by having a thick basal stem (4 mm) and significantly larger polypar spines (reaching 0.51 mm high compared to a maximum of 0.39 mm in the others). It is also the only one with abundant and dense secondary spines (see above). In terms of polypar spine shape, it is also the most remarkable with the particular tip of the spines (in a club-like shape) along with specimen NHMT-R 2E1007. The latter’s polypar spines only reach 0.29 mm high, which is substantially smaller than those of NHMT-R 2E1013. Specimens NHMT-R 2E1010 and NHMT-R 2E1011 are more remarkable by their laterally compressed spines, compared to those of the other specimens which are much thicker. They all share thick polyps, with thick tentacles and a tendency to be crowded and flattened ( Fig. 14 ). This feature of crowded, flattened polyps is more visible in specimens NHMT-R 2E1008, NHMT-R 2E1013, NHMT-R 2E1011 while in specimens NHMT-R 2E1007, NHMT-R 2E1009, and NHMT-R 2E1010 they appear to be more spaced ( Fig. 14 ). However, corallum and spine morphology is the closest between NHMT-R 2E1007 and NHMT-R 2E1013, suggesting that the significant variation of the interpolypar space (not measured but clearly visible on Fig. 14 ) should probably be considered as intraspecific variation, as well as the abundance of secondary spines. Pairwise comparisons of genetic distance of all these specimens within this group always showed genetic distances below 5%. Considering these morphological and genetic comparisons, all these specimens should probably be considered as ecotypes.

Finally, the last group with the helicoidal corallum is only composed of specimen NHMT R 2E1014. Polypar size range is similar to other morphotypes, but polypar spines are narrower and taller, with a maximum height 0.48 mm high. As the line of polyps twist around the stem, polyp density was measured based on the polyps visible one side of the corallum over a distance of 5 mm, and if extended to both sides, it could be up to 8–10 polyps per cm, which is higher than other specimens. Interestingly, the polyps of NHMT-RE 21014 are very similar to species belonging to the genus Cirrhipathes in their shape and size, which give them a distinct shape compared to other specimens. Their tentacles are narrow with a pointed tip, and all arranged circularly around the oral cone ( Fig. 14 ). Pairwise comparisons of genetic distances were also the greatest between NHMT-R 2E1014and all other specimens. Together with the typical helicoidal shape, specimen NHMT-R 2E1014 should be considered as a different species.

In conclusion, four different species might come out of this analysis. Species 1 is composed of NHMT-R 2E1012, species 2 is composed of NHMT-R 2E1015, species 3 is composed of NHMT-R 2E1014, and species 4 is composed of NHMT-R 2E1007, NHMT R 2E1008, NHMT R 2E1009, NHMT R 2E1010 and NHMT R 2E1011. The specimens used in the thermal physiological studies of Godefroid et al. (2022, 2023) all belonged to clade C based on genetic evidences, while morphological characteristics matched those of NHMT-R 2E1013. Note that in Godefroid et al. (2022), the specimens were wrongly assigned to Stichopathes cf. occidentalis .

Of previously described species, seven species were described as having secondary spines: Cirripathes? diversa Brook, 1889 ; C.? flagellum Brook, 1889 ; S. bispinosa Summers, 1910 (nomen nudum for C. flagellum Brook ); S. alcocki Forster Cooper, 1909 ; C. gardineri Forster Cooper, 1903 ; S. maldivensis Forster Cooper, 1909 ; and S. papillosa Thomson & Simpson , var., sensu Forster Cooper, 1909. The Forster Cooper type specimens are still missing, and only the scarce information in the original descriptions can be used for species comparison. Both S. maldivensis and C.? diversa are discussed in Terrana et al. (2020) and are clearly different from the present specimens. The first belongs to Clade D ( Bo et al. 2012; Terrana et al. 2021) and is characterized by colonies having a thick corallum reaching several meters in length (see Fig. 23 in Terrana et al. 2020 for a SEM picture of the corallum). The second is characterized by well-defined helicospirals with either a brown or a white coenenchyme and a thick corallum which is clearly different from the present specimens, despite similarities in crowded and flattened polyps and the presence of conical, blunt tuberculated spines (see Fig. 22 in Terrana et al. 2020 for a SEM of the corallum). These characteristics (corallum with close spirals, and flattened crowded polyps) are also shared by S. alcocki . The corallum is presumed to measure 2 or 3 mm in diameter based on the original drawing of Forster Cooper (1909), while the polyps measure 1 mm in diameter. The spines on the outer side of the coils (i.e. the polypar side) are reported to be blunt, conical and 0.3 mm in height, but no clear tuberculation of these spines is obvious from the drawing. Summers suggested synonymizing C.? diversa Brook, 1889 with S. alcocki . In C. gardineri , the polyps are reported to be “ 2 mm in oral diameter”, the spines conical with a blunt tip, with “a tendency to be knobbed at the apex [...] This form is not unlike C. anguina in appearance.” (Forster Cooper 1903). The size reported for the polyps as well as the corallum of C. anguina (see Fig. 13 in Terrana et al. 2020 for a SEM picture of the corallum) are enough differences to distinguish this species from the present specimens. In C.? flagellum , the colony is reported to measure 3.5 m in height with a corallum 6 mm in diameter ( Brook, 1889), which is way outside of the size ranges of the Mo’orea specimens. In S. bispinosa , the colony is reported to be 1.3 m in height, with large spirals of 21 cm in diameter, a basal diameter of 7 mm, and spines described as papillose and longer on one side ( Summers 1910). Summers (1910) also stated that her specimen corresponded to Brook’s specimen of C.? flagellum . Therefore, these species are not close to the Mo’orea specimens.

Lastly, S. papillosa was originally described by Thomson & Simpson (1905) from Ceylon as a colony growing in spirals. Thomson & Simpson (1905) reported a specimen measuring 38 cm in length and 18 cm in height, growing straight in the first 4 cm before growing in spirals, with a basal diameter of 1.25 mm tapering gradually to 0.5 mm at the top. The polyps measure 1 mm in diameter, and the spines are reported to be slightly papillose. The spines are reported to be conical, roughened and arranged in spirals, standing at right angles to the corallum, with some spines notched at the tips. Based on this descriptions, S. papillosa might be related to the specimen NHMT-R 2E1014 of this study.

In conclusion, pending a better comprehension of the occurrence of ecotypes within the genus Stichopathes , a taxonomic revision of the whole genus, and a larger-scale molecular study with both mitochondrial and nuclear markers to test the hybridization hypothesis, no new nominal species are established for the Mo’orea specimens grouping in Clade C, although they could be considered as four distinct undetermined species.

Figures

FIGURE 2. (a) Phylogenetic tree of Symbiodiniaceae sequences belonging to Cladocopium and Breviolum detected in some Stichopathes colonies (from Clade C) derived from Bayesian approaches. Bayesian posterior probabilities (first values) and Maximum Likelihood bootstrap support values (in brackets) are presented in black. (b–d) Histological views of zooxanthellaelike cells repartition in black coral tissues (blue arrows). Stichopathes C01 was identified belonging from Clade C based on a picture and the general morphology of the colony.

FIGURE 10. Examples of the differences seen in polyp shape and appearance of the same fragment from the same colony. (a) Entire colony NHMT R2E1018. (b) In situ picture. (c) Freshly sampled fragment. (d) Fragment stored in 70% ethanol for a few months.

FIGURE 11. Stichopathes spp. of Clade C, with pictures of entire colonies and middle sections of corallum (polypar side on the right side). (a–d) NHMT-R2E1007. (e–h) NHMT-R2E1008. (i–l) NHMT-R2E1009. (c, g, k) Typical polypar spines. (d, h, l) Abpolypar spines.

FIGURE 12. Stichopathes spp. of Clade C, with pictures of entire colonies and middle sections of corallum (polypar side on the right side). (a–d) NHMT-R2E1010. (e–h) NHMT-R2E1011. (i–l) NHMT-R2E1012. (c, g, k) Typical polypar spines. (d, h, l) Abpolypar spines. Small white dots on the spines are an artifact of SEM preparation.

FIGURE 13. Stichopathes spp. of Clade C, with pictures of entire colonies and middle sections of corallum (polypar side on the right side). (a–d) NHMT-R2E1013. (e–h) NHMT-R2E1014. (i–l) NHMT-R2E1015. (c, g, k) Typical polypar spines. (d, h, l) Abpolypar spines..

FIGURE 14. Illustrations of the polyps magnified under a stereomicroscope of each morphotype described in Clade C for Polynesian specimens and grouped following the taxonomic discussion. Illustrated polyps have all been stored in 70% ethanol for the same period of time before being photographed, therefore their state of preservation is comparable. Scales: 1 mm.