Clathria (Clathria) flo Payne, Samaai & Gibbons sp. nov.

urn:lsid:zoobank.org:act: 67DCF563-3F82-48E4-81E2-783E4C619CB4

Figure 12A–K, Tables 10, 11

Material examined. Holotype. SAMC-A096904 (cross-reference TS 2342 & WSL-INV94(14)): Walters Shoal Seamount, Grid WSL044, Station ALG10976, coll. RV Algoa, (33°14.0’ S; 43°55.5’ E) - (33°13.7’ S; 43°55.6’ E), 25–28 m depth, 02 June 2014 . Paratypes. SAMC-A096888 (cross-reference TS 2302 & WSL-INV54): Walters Shoal Seamount, Grid WSL022, Station ALG10954, coll. RV Algoa, (33°10.9’ S; 43°48.6’ E) - (33°11.2’ S; 43°50.2’ E), 72–170 m depth, 29 May 2014 . SAMC-A096905 (cross-reference TS 2348 & WSL-INV94(20)), SAMC-A096907 (cross-reference TS 2355 & WSL-INV94(27)): Walters Shoal Seamount, Grid WSL044, Station ALG10976, coll. RV Algoa, (33°14.0’ S; 43°55.5’ E) - (33°13.7’ S; 43°55.6’ E), 25–28 m depth, 02 June 2014 . Additional material. TS 2399 (WSL-INV92 (10)), TS 2422 (WSL-INV92 (11)): Walters Shoal Seamount, Grid WSL043, Station ALG10975, coll. RV Algoa, (33°13.8’ S; 43°55.5’ E) - (33°13.1’ S; 43°55.8’ E), 28–30 m depth, 02 June 2014. TS 2508 (WSL-INV84 (37)), TS 2511 (WSL-INV84 (40)): Walters Shoal Seamount, Grid WSL042, Station ALG10974, coll. RV Algoa, (33°11.2’ S; 43°51.0’ E) - (33°11.2’ S; 43°50.7’ E), 28–34 m depth, 02 June 2014.

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Type locality. Walters Shoal Seamount, south of Madagascar on the Madagascar Ridge, Western Indian Ocean (Fig. 1).

Description (Fig. 12A). Thickly encrusting, lobate form. Length 3.4 cm, width 2.5 cm and thickness 1.3 cm. Surface undulating but smooth and velvety, with randomly scattered small, round oscules (<1 mm in diameter), sunken with no distinct membranous lip. Texture soft and spongy, compressible and easily torn. Colour in life orange, beige in preservative.

Skeleton (Fig. 12B, C). Choanosomal skeleton regularly reticulate, forming irregular anastomoses of differentiated primary and secondary fibres, diverging in plumoreticulate manner towards ectosome. Fibres are differentiated into primary and secondary transverse components. Primary fibres cored with principal styles, cemented by spongin that does not form a distinct sheath around the fibre and echinated by acanthostyles. Secondary fibres with unispicular tracts of principal styles. Ectosomal and subectosomal skeleton consists of principal styles and auxiliary subtylostyles, with the former arising from ascending choanosomal tracts being slightly plumose and diverging into erect bundles that project obliquely through the surface. The latter form compact diverging brushes at the ectosomal surface, barely penetrating the subectosomal membrane. Microscleres scattered throughout choanosome.

Spiculation (Table 10). Megascleres. Styles, smooth, curved, with well-rounded to almost subtylote-like base, distally hastate: 234 (179–320) × 9 (8–12) µm, n = 10 (Fig. 12D). Subtylostyles, smooth, straight with a terminally spined elongated base, distally fusiform: 211 (130–313) × 3 (2–4) µm, n = 10 (Fig. 12E, F). Acanthostyles, straight to slightly bent, with well-rounded to almost subtylote-like base, distally hastate: 138 (132–148) × 7 (6–10) µm, n = 10 (Fig. 12G). Microscleres. Toxas, terminally spined, in two size classes: I) 146 (111–177) µm, n = 20 (Fig. 12H); II) 45 (35–61) µm, n = 20 (Fig. 12I, J). Palmate isochelae: 13 (11–14) µm, n = 10 (Fig. 12K).

Substratum, depth range and ecology. Eight specimens found on rocky substrata in four sleds. Depth range: 25– 170 m.

Etymology. The species name ‘ flo’ is dedicated to Dr Wayne Florence from the Iziko Museums of South Africa (Cape Town). This name honours Dr Florence for his significant contributions to our knowledge of the Bryozoa fauna in South Africa. Additionally, Dr Florence is acknowledged for his support in providing laboratory space and resources to Dr Toufiek Samaai.

Remarks. The present material conforms to Clathria (Clathria) Schmidt, 1862 as diagnosed by a single category of auxiliary style and no marked difference between the axial and extra-axial regions in the choanosomal skeleton (Hooper 2002). There are 19 species of Clathria (Clathria) found within the WIO and South Africa (de Voogd et al. 2024), none of which are conspecific with C. (C.) flo sp. nov. (see Tables 10, 11)

Of the 19 species of Clathria (Clathria) recorded from the WIO and South Africa, one species, Clathria (Clathria) lobata Vosmaer, 1880, has terminally spined toxas (Table 10). Clathria (Clathria) lobata, however, has large megascleres and is erect branching. Five species— Clathria (Clathria) omegiensis Samaai & Gibbons, 2005; Clathria (Clathria) rhaphidotoxa Stephens, 1915; Clathria (Clathria) inhacensis Thomas, 1979; Clathria (Clathria) decumbens Ridley, 1884; and Clathria (Clathria) maeandrina Ridley, 1884 —are encrusting (Table 11). All 19 Clathria (Clathria) species differ substantially from Clathria (Clathria) flo Payne, Samaai & Gibbons sp. nov. in major features such as growth form, spicule geometries, spicule sizes, spicule structure and skeletal architecture (Table 10, 11).