Conopora tenuiramus, Cairns, Stephen D. & Zibrowius, Helmut, 2013

Cairns, Stephen D. & Zibrowius, Helmut, 2013, Stylasteridae (Cnidaria, Hydrozoa, Filifera) from South Africa, Zootaxa 3691 (1), pp. 1-57 : 42-43

Conopora tenuiramus sp. nov.

Figs. 3 E–F, 20A–N, 25

Etymology. From the Latin tenuis (thin) and ramus (branch), an allusion to the slender terminal branches of this species; treated as a noun in apposition.

Types and Type Locality. Holotype: MN SM228, female colony, SAM, and SEM stubs 1690, 1693 (USNM).

Paratypes: MN SM162, 4 branch fragments, gender indeterminate, SAM; MN SM228, 2 male branches, SAM; MN SM232, 2 dead male branch fragments, SAM, and SEM stub1690 (USNM); PF 14306, 1 female colony, SAM H1455. Type Locality: 32°29.5’S, 28°57.1’E (continental slope north of East London, off northern Eastern Cape Province), 650– 700 m.

Material Examined. Types. Reference Material: Broch’s (1936) Mauritius specimen of C. tenuis and C. major (ZMC).

Description. Colonies are uniplanar and relatively small, the holotype ( Fig. 3 F) only 3.8 cm tall and 2.4 cm broad, with an intact basal branch having a diameter of 2.75 mm. However, larger colonies are known (PF 14306), which are up to 6 cm long and 1.1 cm in diameter, most of the main branch diameter consumed with a polynoid gall tube. Regardless of the size of the colonies, the distal branches are invariable delicate and thin, usually less in diameter than the cyclosystems they support. All colonies support a commensal polynoid gall tube ( Figs. 3 E, F), which is prominent in the basal part of the main branches, often forming a web-like membrane that seems to envelope the lower branches. Branching is dichotomous, nodes occurring at almost every cyclosystem, producing a highly ramified and often anastomotic colony. The coenosteal texture is a well-defined linear-imbricate ( Figs. 20 G–I), the strips being 70–80 µm in width, with about 65 platelet leading edges per mm, although parts of some colonies appear to have a smooth (worn?) texture ( Fig. 20 J). The platelets are somewhat roughened by having low longitudinal ridges. The branch and polynoid gall tube coenosteum, ampullae, and pseudosepta are densely covered with low nematopore mounds, the pores on the coenosteum and ampullae 20–40 µm in diameter ( Fig. 20 K) and the mounds up to 30 µm in height, whereas those on the pseudosepta are usually slightly larger (35–45 µm in diameter) and flush with the coenosteum, and arranged one to a pseudoseptum ( Fig. 20 C, E). The colonies are white.

Cyclosystems are unifacially arranged on all branches in a linear manner, elliptical to slightly irregular in shape ( Figs. 20 B–D), and 1.0– 1.4 mm in greater diameter. Based on 40 cyclosystems, the range of dactylopores per cyclosystem is 13–19; the average is 16.0 (ơ = 1.13); and the mode is 15.

The gastropore tube is double chambered ( Fig. 20 F), the lower chamber flattened, about 0.45 mm in diameter and 0.15 mm in height, separated from the upper spherical chamber by a delicate gastropore ring constriction of about 0.26 mm diameter. The upper chamber is about 0.35 mm in diameter, above which the gastropore tube is flanked with dactylotomes. Dactylotomes range from 75–80 µm in width, the pseudosepta being slightly wider and more variable in width, ranging from 0.10–0.21 mm. The tops of the pseudosepta are flat to slightly convex.

Female ampullae are massive swellings (up to 1.6 mm in diameter), sometimes even hemispherical, but often partially submerged in the coenosteum, most clustered in the coenosteum forming the polynoid gall tube ( Fig. 20 L). Efferent pores are well defined, lateral in position, and about 0.25–0.30 mm in diameter. Male ampullae are also clustered in the polynoid gall tube coenosteum and frequently internal, only seen in a cross sectional break of the polynoid gall tube coenosteum ( Figs. 20 M, N). They are about 0.4–0.7 mm in internal diameter; their efferent pores were not observed.

Comparisons. Only one other species of Conopora has unifacially-arranged cyclosystems (but see below), C. unifacialis Cairns, 1991 (from New Zealand). Conopora tenuiramus is easily distinguished from that species by its thicker pseudosepta, lesser number of dactylopores per cyclosystem, polychaete commensalism, and gastropore tube shape. But, Conopora tenuiramus is also similar to C. laevis (Studer, 1878) , especially in its delicate colony shape, polychaete commensalism, nematopore distribution, and ampullar shape, but C. tenuiramus can be distinguished by having unifacially arranged cyclosystems, more dactylopores per cyclosystem, and thinner branches.

Although similar, the specimen reported from Mauritius by Broch (1936) as C. tenuis Hickson & England, 1905, has smaller cyclosystems and female ampullae, hemispherical female ampullae, and a mixture of unifacial and sympodially arranged cyclosystems.

Conopora tenuiramus was also compared to Broch’s (1936) C. major Hickson & England, 1905, also collected from off Mauritius. Both species have unifacial cyclosystems, a polynoid commensal, and similarly-sized cyclosystems and ampullae, but Broch’s specimens differ in having female efferent pores that open within the gastropore tube, and frequently having enlarged (widened) pseudosepta in the abcauline position of the cyclosystem, resembling incipient lids characteristic of Crypthelia .

Distribution. Continental shelf and slope off southeastern South Africa from Cape Seal (Western Cape Province) to northern Eastern Cape Province (Fig. 25), 146– 650 m.

Figures

FIGURE 3. Colonies of various species: A, Stenohelia venusta, holotype. B, Stenohelia spinifera, holotype. C, Conopora sola, holotype. D, Conopora verrucosa, Valdivia 104. E – F, Conopora tenuiramus, E, female paratype from PF 14306; F, holotype. G – I, Crypthelia micropoma, UCTES SCD 301 (H, male; I, female).

FIGURE 20. Conopora tenuiramus (A – L, female holotype, MN SM 228, SAM; M – N, male paratype, MN SM 232, SAM): A, unifacially arranged cyclosystems. B – D, cyclosystems showing the regular placement of one nematopore per pseudoseptum (C is a stereo pair). E, nematopores on outer edges of each pseudoseptum. F, stereo view of double-chambered gastropore tube. G – I, linear-imbricate coenosteal texture. J, transition of linear-imbricate to smooth coenosteal texture. K, a single nematopore mound. L, female ampulla and efferent pore. M, transverse section though several male ampullae lodged in polynoid gall tube coenosteum. N, longitudinal section of male ampullae in polynoid gall tube coenosteum.