Stylaster subviolaceus (Kent, 1871)

Cairns, Stephen D. & Zibrowius, Helmut, 2013, Stylasteridae (Cnidaria, Hydrozoa, Filifera) from South Africa, Zootaxa 3691 (1), pp. 1-57 : 23-26

Stylaster subviolaceus (Kent, 1871)

Figs. 1 J, 11A–L, 25

Allopora subviolacea Kent, 1871: 280 .—Moseley, 1879: 480 (listed).—Boschma, 1957: 28–29 (in part, not tropical records, which are S. blatteus ); 1961: 206–210, 218–219 (comparison to S. blatteus ); 1966a: 267–271, pl. 1, text-figs. 1–2 (complete redescription); 1966b: 112.—Vervoort & Zibrowius, 1981: 38.—Williams, 1986: 12, fig. 1.

Not Allopora subviolacea: Greeff, 1886: 11 .—Bauer, 1896: 696.—Monod, 1928: 175.—Eguchi, 1941: 1183 (most being S. blatteus ).

Stylaster (Allopora) subviolaceus: Broch, 1936: 13 , 17, 66–69, pl. 11, fig. 29, text fig. 21 (redescription, in part, not West African specimens).

Stylaster subviolaceus: Cairns, 1983b: 429 (listed).—Zibrowius & Cairns, 1992: 76.

Types and Type Locality. Male holotype deposited at the BM (1851.11.14.27); 3 small fragments of holotype also deposited at the Naturalis Biodiversity Centre (RMNH 15364). Type Locality: Unknown, although Boschma (1966a) attempted to “restrict” the type locality to the southern coast of South Africa.

Material Examined. PF 15607, 12 colonies, SAM H3053–54; PF 15614, 4 colonies, SAM H3051; PF 15618, 2 male colonies, SAM 1225; PF 15675, 8 colonies, SAM 3052, and SEM stub 1697 (USNM); PF 15745, 5 colonies, SAM H3055; UCTES TRA120, 5 colonies, Naturalis Biodiversity Centre; UCTES FAL303, 1 colony, Naturalis Biodiversity Centre; TRA151, 1 male fragment and SEM stub 1698, USNM 76533; portion of holotype deposited at the Naturalis Biodiversity Centre; holotype (BM 1851.11.14.27); specimen reported by Broch (1936), ZMC; specimen reported by Boschma (1966a), Naturalis Biodiversity Centre.

Description. Colonies are moderately large, uniplanar, and sparsely branched, not having branch anastomosis. The largest known colony (the holotype) is 8.9 cm in height and 1.3 cm in basal branch diameter. Branching is dichotomous, with U-shaped axils, the branch tips about 2.5 mm in diameter. There are no polynoid gall tubes. The coenosteal texture is reticulate-smooth ( Figs. 11 C–E), the strips being 60–80 µm in width and somewhat convex in shape, also having a vertical dimension, as in S. nobilis ; the coenosteal slits are only 2–3 µm in width. Nematopores were not observed. The colonies are light violet or purple in colour, the central core and tips of branches being white to light yellow.

Cyclosystems are homogeneously arranged on all branch surfaces. They are elliptical to irregular in outline and 0.9–1.3 mm in greater diameter; their edges are slightly raised above the coenosteum, especially on the lower Dactylopores/Cyclosystem: Range, 2–8; 6.1; 5 and 6 3–12; 8.67; 8 6–12; 8.88; 9 1–19; 11.0; 10 and 11 7–12; 9.22; 9

Average, Mode

Isolated Dactylopores Common Rare Very common Absent Absent

Dactylostyles Unilinear, 50 Μm tall Multilinear, 80 Μm tall Rudimentary elements Dactyloglossae Dactyloglossae

Female Ampullae Primarily internal, 1.2–1.5 Unknown Superficial, 0.5–0.65 mm Primarily internal, with Internal, with efferent pore mm, no efferent pore efferent pore into gastropore into upper gastropore tube tube

Male Ampullae Partially internal, 0.4 mm Primarily internal, Superficial, 0.3–0.45 mm Superficial, 0.3–0.5 mm Low mounds, 0.4 mm

0.38–0.50 mm, efferent

pores unknown

Other Characters Ring palisade elements Ring palisade elements Gastrostyles variable in Gastrostyles variable in

elongate elongate shape shape

Distribution Southwestern S. Africa, Southwestern S. Africa, Gulf of Guinea, 0–10 m South Africa, 11–131 m Southeastern S. Africa,

3–174 m 22–88 m 80–155 m (abcauline) side. Based on 30 cyclosystems, the range of dactylopores per cyclosystem is 6–12; the average is 8.67 (ơ = 1.56); and the mode 8. Other counts made by Broch (1936) and Boschma (1961, 1966a) yielded slightly lower averages of 6.78, 6.97, and 8.06, modes of 7 and 8, and a range as low as 3. Diastemas are rare.

The cylindrical gastropore tube is 0.32–0.39 mm in diameter and up to 1.3 mm long. The gastrostyles are lanceolate ( Fig. 11 K, L), up to 0.58 mm in height and 0.23 mm in diameter, having a H:D ratio of 1.7–3.6. The gastrostyle is covered with spines, each up to 40 µm in length. The ring palisade consists of elongate (not cylindrical) elements, each up to 60 µm in length and 22 µm in width, the greater axis aligned with the gastropore tube ( Fig. 11 H, I), each elongate about 50 µm in height. The dactylotomes are 70–75 µm in width. Dactylostyles are well developed ( Fig. 11 F, G) and often in a crowded arrangement, each slightly clavate element up to 76 µm in height and about 15 µm in diameter.

Female ampullae are unknown. Male ampullae are primarily internal ( Figs. 11 B, J, K), visible on the surface as only a slight swelling and apical efferent pore. The diameter of the internal cavity is 0.38–0.50 mm.

Comparisons. Stylaster subviolaceus is quite similar to S. nobilis , both species sympatric in range and depth. However, when scrutinized ( Table 1 ), S. subviolaceus appears to differ in: having a higher range and average number of dactylopores per cyclosystem, a coarser coenosteal texture composed of wider and slightly convex coenosteal strips, raised cyclosystems (vs flush), elliptical to irregularly-shaped (vs round) and larger cyclosystems, lacking isolated dactylopores, and in having distinctively shaped ring palisade elements.

Stylaster subviolaceus has also been confused with S. blatteus (Boschma, 1961) in the past, as chronicled by Boschma (1961). S. blatteus , the so-called “West African blue coral” or “akori” has been used to manufacture ornamental beads at least since the sixteenth century. This species occurs exclusively in shallow water (0–10 m) in the tropical Gulf of Guinea region. Perhaps because of the similarity of colour and belonging to the same genus, the tropical species was called Allopora subviolacea by several authors (see synonymy) until Boschma (1961) recognized the mistake and named the tropical species A. blattea . S. subviolaceus differs from S. blatteus ( Table 1 , and Zibrowius & Cairns 1992) in having a less intense colouration (not dark purple) that fades in the branch axis and tips, reticulate-smooth coenosteal texture (not reticulate-granular), larger cyclosystems, lacking isolated dactylopores (which are very common in S. blatteus ), and in having much larger dactylostyles. Iro nically, both species share the same morphology of the elongate elements composing their ring palisades.

Remarks. Although the species has been well described and figured (Broch 1936, Boschma 1966a, and herein), it must be kept in mind that it is known from relatively few records, most of that material consisting of small branches.

Distribution. Known from a small region off southwestern South Africa from the Cape of Good Hope to Cape Agulhas (Western Cape Province)(Fig. 25), 22– 88 m.

Figures

FIGURE 1. Colonies of various species: A – B, Lepidopora diffusa, PF 13654. C, Inferiolabiata africana, holotype. D, Inferiolabiata lowei, PF 907. E, Inferiolabiata spinosa, Anton Bruun 420 A. F, Errina capensis, syntype, Manchester Museum. G, Errina capensis, MN XX 129, female. H, Gyropora africana, BM 1977.8. 5.1. I, Stylaster nobilis, PF 7014, 3 distal branches. J, Stylaster subviolaceus, PF 15675.

FIGURE 11. Stylaster subviolaceus (A – F, H – I, male from PF 15675, SAM; G, J – L, male from UCTES TRA 151, USNM 76533): A, stereo view of branch segment with cyclosystems and male ampullae. B, stereo view of a cyclosystem and adjacent male ampulla. C – E, reticulate-smooth coenosteal texture. F – G, dactylostyle elements. H, gastropore tube missing its gastrostyle but showing the ring palisade. I, elongate ring palisade elements. J, branch cross section showing internal male ampullae. K, stereo view of gastrostyle and internal male ampulla. L, stereo view of a gastrostyle.

Tables

TABLE 1. Distinguishing Characteristics of the South African species of Stylaster (Group A).

Branch Tips	S. nobilis (Kent, 1871) Blunt	S. subviolaceus (Kent, 1871) Blunt	S. blatteus (Boschma, 1961) Blunt	S. bithalamus Broch, 1936 S. griseus n. sp. Sympodial Blunt
Commensal Polynoid Tube	Absent	Absent	Absent	Present Absent
Coenosteal Colour	Rose-pink	Rose (white interior)	Dark purple	White Gray or light brown
Coenosteal Texture	Reticulate-Smooth, deep strips	Reticulate-Smooth, deep strips	Reticulate-Granular	Reticulate-Granular Reticulate-Granular (irregular granules) (irregular granules)
Cyclosystems: Prominence and Diameter	Flush, 0.7–0.8 mm	Raised, 0.9–1.3 mm	Slightly raised, 0.8–0.9 mm	Slightly raised, 1.0–1.4 mm Raised, 0.9–1.1 mm