Stylaster lonchitis Broch, 1947

Cairns, Stephen D. & Zibrowius, Helmut, 2013, Stylasteridae (Cnidaria, Hydrozoa, Filifera) from South Africa, Zootaxa 3691 (1), pp. 1-57 : 32-34

Stylaster lonchitis Broch, 1947

Figs. 2 I, 15A–J, 30

? Stylaster eximius facies dentatus, irregularis, minor: Hickson & England, 1905: 10–11, pl. 1, figs. 4–8.

Stylaster (Eu-Stylaster) lonchitis Broch, 1947: 309 –311, pl. 1, fig. 2, text-fig.2a–c.

Stylaster lonchitis: Boschma, 1957: 12 ; 1962, 287–293, 2 pls., 2 text-fig. (complete redescription).—Vervoort & Zibrowius, 1981: 40.—Cairns 1983b: 430 (listed).

Stylaster sp. Liltved, 1989: fig. 227 (with Pedicularia scar).

Types and Type Locality. Holotype, BM 1950.5.22.6; fragment of holotype, USNM 85786. Type Locality: 4°57’S, 39°13’18”E (Pemba Channel, Tanzania), 113 m.

Material Examined. Anton Bruun 8—420A, several colonies, USNM 1104251 and 1174691; MN SM163, 10 small dead branch fragments, SAM; 33°01.8’S, 28°04.4’W (off Gonubie), 85 m, 17 July 1984, coll. William Rune Liltved, 1female colony now in 11 pieces, SAM, and 1 colony and SEM stubs 1704–05 (USNM 1189355); holotype; specimens reported by Boschma (1962).

Description. Colonies are uniplanar and relatively small, the largest specimen examined (Gonubie specimen) only 4.5 cm in height. Branching is dichotomous and usually at right angles; branches are straight, not geniculate, even though the cyclosystems are closely arranged in an alternating manner (sympodially) on either side of the branches ( Fig. 2 I). The coenosteal texture is linear-granular, the coenosteal strips ranging from 57–72 µm in width, and are often sharply convex, almost ridged ( Fig. 15 D, E). The strips are covered with low rounded granules, as well as numerous nematopore tubes in the shape of truncated cones, the cones up to 100 µm in height and about 85 µm in basal diameter ( Fig. 15 F). The colony is a salmon orange, whereas the branch tips are white.

Cyclosystems are exclusively arranged on the branch edges and are very closely spaced; they are circular near the branch tips, but somewhat horizontally elongate or irregular in shape on the majority of branches ( Figs. 15 A, B). Dactylopores are missing from the entire upper edge of the cyclosystem, resulting in a crescent-shaped tier of abcauline dactylopore spines ( Figs. 15 A, B), and with the coenosteal strips seeming to flow directly into the upper diastemate region of the gastropore tube. Cyclosystems are 0.8–1.2 mm in greater diameter. Based on 50 cyclosystems, the range of dactylopores per cyclosystem is 7–14; the average is 10.38 (ơ = 1.56); and the mode, 10. Based on the same number of cyclosystems, Broch (1947) reported a range of 7–12, an average of 9.54 and a mode of 10, whereas Boschma (1962) reported a range of 6–12, a weighted average of 9.21, and a mode of 9. Cyclosystems near the branch tips tend to be complete, lacking the diastema ( Fig. 15 A, upper), and thus have slightly more dactylopores per cyclosystem, which might explain the slight discrepancy on the reported averages and ranges.

The gastropore tube is straight and cylindrical, about twice the length of the gastrostyle. The gastrostyle is lanceolate, up to 0.35 mm in height and about 0.14 mm in diameter; a diffuse ring palisade is present, the cylindrical elements being about 19 µm in height ( Figs. 15 H, I). The dactylotomes are about 0.9–1.1 mm in width, the pseudosepta range from 0.11–0.18 mm in width, the latter being quite porous ( Fig. 15 C). Dactylostyles are composed of a linear row of clavate elements, each about 27 µm in height ( Fig. 15 G).

Female ampullae are usually clustered on one side of the branches, and are prominent hemispheres 0.70–0.75 mm in diameter; nematopores tubes also cover the ampullae, making them prickly in appearance ( Fig. 15 J). Efferent pores are rarely observed, but when present are quite small, about 0.10 mm in diameter. Male ampullae are not known.

Comparisons. Although the identity of the South African specimens are undoubtedly the same as S. lonchitis , it is possible that this species is a junior synonym of the taxa reported from Indonesia as Stylaster eximius facies dentatus, irregularis, and minor, by Hickson & England (1905), and if so, one of these names would have nomenclatural priority, e.g., dentatus. This possibility was hinted at by Boschma (1962) when he compared S. lonchitis to S. duchassaingi , which he thought similar to S. eximius . Although the types of these facies and of S. lonchitis have been examined by the authors, there is simply not enough material at hand to make a definitive synonymy. The unifying characters of this taxon are its crescent-shaped cyclosystems with broad diastemas, prominent nematopores tubes, straight branches, and closely spaced cyclosystems.

Distribution. Continental shelf off the Eastern Cape Province of South Africa (Fig. 30), 85–90 m; off Kenya and Tanzania (Pemba Canal and Zanzibar Channel), 55– 140 m.

Figures

FIGURE 2. Colonies of various species: A – B, Stylaster bithalamus, MN SM 185, male, anterior and posterior views of same colony, respectively. C, Stylaster griseus, holotype. D – F, Stylaster amphiheloides, syntypes, BM 1842.12.2.79. G – H, Stylaster amphiheloides, MN SM 228, posterior and anterior views of same colony. I, Stylaster lonchitis, Liltved specimen. J, Stylaster kenti, holotype.

FIGURE 15. Stylaster lonchitis collected by Liltved, female, USNM 1189355: A, stereo view of two cyclosystems. B, cyclosystem with a broad diastema. C, porous pseudosepta. D – E, ridged linear-granular coenosteal texture. F, conical nematopore tubes. G, dactylostyle elements. H, stereo view of gastropore tube and gastrostyle. I, gastrostyle and ring palisade. J, female ampulla.