Stylaster nobilis (Kent, 1871)

Cairns, Stephen D. & Zibrowius, Helmut, 2013, Stylasteridae (Cnidaria, Hydrozoa, Filifera) from South Africa, Zootaxa 3691 (1), pp. 1-57 : 21-23

Stylaster nobilis (Kent, 1871)

Figs. 1 I, 10A–L, 24

Allopora nobilis Kent, 1871: 279 –280, no fig.—Moseley, 1879: 480 (listed); 1881: pl. 2, figs. 10–12; 1892: 460–461, text-figs. 2–3.—Hickson, 1900: 93–94.—Gilchrist, 1921: 31, 72.—Boschma, 1956b: 154–164, pl. 1, figs. 1–4, pl. 2, figs. 1–4, pl. 3, figs. 1–9, 4 text figs. (complete redescription and discussion of previous records); 1957: 23–24 (complete synonymy); 1961: 220–221; 1966a: 271; 1966b, 112.—Rudd, 1978: 1–36.—Vervoort & Zibrowius, 1981: 38.—Williams, 1986: 11, 13.

Allopora explanata Kent, 1871 , 280, pl. 25, figs. 2, 2a–c.—Moseley, 1879: 480 (listed).

Stylaster (Allopora) nobilis : England, 1926: 267, 273–275, text figs. 9–11 (observations of male gonophore).—Broch, 1936: 11, 13, 63–65, pl. 11, fig. 28, text-figs. 20–21 (redescription).

Stylaster nobilis: Best, Faure & Pichon,1980: 623 (listed).—Cairns, 1983b: 429 (listed).

Types and Type Locality. Fragments of the male holotype of A. nobilis are deposited at the BM (1893.6.1.1). Type Locality: Boschma (1957) “fixed” the type locality of this species as False Bay, South Africa, 30 fms, the locality of the specimen reported by Hickson (1900), however this is not based on a type specimen and thus cannot serve as the type locality. The type locality was unrecorded in the original description and thus remains unknown, but is probably in the region of the Cape of Good Hope.

Material Examined. PF 393, 1 colony, SAM H1239; PF 503, 1 colony, SAM H1238; PF 559, 2 colonies, SAM H1227; PF 622, 1 colony, SAM H1230; PF 808, 1 colony, SAM H1231; PF 7014, 1 female, 1 male colony, and SEM stubs 1695–96, USNM 76531, and 34 colonies, SAM H1229; PF 7023, 11 colonies, SAM H1243; PF 13476, 1 indet. colony, SAM H1228; PF 15607, 2 colonies, SAM H1220; PF 15614, 1 colony, SAM H1218; PF 15618, 2 colonies, SAM H3054; PF 15675, 2 colonies, SAM H1217; PF 18347, 1 colony, SAM H1494; UCTES AFR801, 1 colony, RMNH 15833; UCTES AFR801, 1 male colony, RMNH 15876; UCTES FAL332, 1 colony, RMNH 15838; UCTES FAL573, 5 colonies, RMNH 15831; UCTES FAL582, 1 colony, RMNH 15832; UCTES SCD56, 1 colony, RMNM 15834; UCTES SCD311, 1 colony, RMNH15837; UCTES TRA 23, 1 male and 1 female colony, RMNH 15835, and 2 male colonies and SEM stub 1694 (USNM 76532); UCTES WCD36, 1 colony, RMNH 15830; Valdivia 95, 5 fragments, ZMB; off Cape Town, 9–22 m, 1 female colony, coll. Branko Velimirov, Senckenberg Museum, Frankfurt; Mossel Bay, 1 colony, SAM H1510; off Cape of Good Hope, 2 colonies, BM1977.8.7.1; five fragments of holotype (BM 1893.6.1.1); specimens reported by Hickson (1900) MHNHP; specimens reported by Boschma (1956a, 1966b (reported herein)), the Naturalis Biodiversity Centre; specimens reported by Broch (1936), ZMC.; specimen reported by Best et al. (1980), Musée Royal de l’Afrique Centrale, Tervuren ( Belgium), #968.

Description. Colonies are large, robust, uniplanar, and sparsely branched, not uncommon for colonies up to 5 cm being unbranched ( Fig. 1 J). The largest known colony (the holotype) is 30 cm tall and 23 cm wide, having a massive basal branch diameter of 5 cm. Branching is dichotomous, resulting in U-shaped axils; branch tips are blunt, 2–4 mm in diameter; there is no branch anastomosis. There are no polynoid gall tubes. The coenosteal texture is reticulate-smooth, the strips being 22–41 µm in width and fairly short, but quite tall, standing as pillars up to 0.2 mm in height ( Fig. 10 D); the bordering coenosteal slits are quite narrow, about 2 µm. Small, shallow cylindrical depressions are scattered over the coenosteum, each about 50 µm in diameter and only 20–30 µm in depth, these assumed to be nematopores ( Fig. 10 B, K, L). The colonies are light pink to rose colour, but branch tips and the central core of large diameter branched are white.

Cyclosystems are homogeneously arranged on all branch surfaces, although occasionally several appear to be arranged in a short row, and in some cases 2 or 3 cyclosystems are fused together. Cyclosystems are round, 0.7–0.8 mm in diameter, and usually flush with or only slightly raised above the coenosteum ( Fig. 10 B). Based on 50 cyclosystems, the range of dactylopores per cyclosystem is 4–8; the average is 6.14 (ơ = 1.05); and the mode is 6 (but see Remarks). Diastemas ( Fig. 10 B) are not uncommon, especially in cyclosystems near the base of the colony.

The gastropore is circular and the gastropore tube cylindrical, each having a diameter of 0.28–0.35 mm, the tube as deep as 1 mm. The gastrostyle is lanceolate and pointed, up to 0.45 mm in height and 0.25 mm in diameter, having a L:D ratio of 1.5–3.2. The style is covered with sharp spines up to 21 µm in length. There is a discrete ring palisade near the tip of the gastrostyle ( Fig. 10 E), the clavate elements up to 65 µm in height. The dactylotomes are 60–100 µm in width, the pseudosepta being wider and variable in size. Dactylostyles ( Fig. 10 I) are well developed, often unilinear rows of clavate elements up to 50 µm in height, easily seen in apical view.

Female ampullae are primarily internal, only low superficial mounds visible in an intact corallum ( Fig. 10 K), but these cavities are easily seen in branch cross section, ranging from 1.2–1.5 mm in diameter. Efferent pores are never seen, although it is not unusual to observe spent female ampullae, seen as large craters in the coenosteum ( Figs. 10 A, L). It is likely that the entire top of the ampulla disintegrates to release the planula. Male ampullae are also primarily internal, about 0.34– 0.41 mm in diameter, and also best seen in branch cross section ( Figs. 10 J, M). They are very abundant in colonies, manifested as very low superficial mounds having apical efferent pores, the pores irregular in shape and about 50 µm in diameter.

Comparisons. See Comparisons in the account of S. subviolaceus and Table 1 .

Remarks. Although relatively few specimens are known of this species, it is one of the best-described stylasterids thanks to the exhaustive account of Boschma (1956b), the redescription of Broch (1936), and the observations of male gonophores by Hickson (1900). For instance, Boschma summarized the results of counting 600 dactylopores per cyclosystem, resulting in a range of 2–8, an average of 5.09, and a mode of 5, slightly less than reported herein, and he illustrated no less than 21 gastrostyles.

Distribution. Common on South African continental shelf from Saint Helena Bay (Western Province) to Sandy Point (near Cape Morgan), Eastern Cape Province (Fig. 24), 3– 174 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 10. Stylaster nobilis (A – C, I, K, L, female form PF 7014, USNM 76531; E – F, J, M, male from UCTES TRA 32, USNM 76532; D, G, H, male from PF 7014, USNM 76531): A, branch segment with numerous cyclosystems, a ruptured female ampulla, and numerous nematopores. B, a cyclosystem. C – D, reticulate-smooth coenosteal texture. E – G, gastrostyles and diffuse ring palisade (E is a stereo pair). H, spines on gastrostyle. I, dactylostyle elements. J, M, branch cross section with gastrostyles and internal male ampullae (M is a stereo pair). K, superficial female ampulla. L, stereo view of ruptured female ampulla.