Siphonidium ramosum ( Schmidt, 1870 )

Van, Rob W. M., 2017, Sponges of the Guyana Shelf, Zootaxa 1, pp. 1-225 : 107-109

Siphonidium ramosum ( Schmidt, 1870)

Figures 66 a–d

Leiodermatium ramosum Schmidt, 1870: 21 , pl. 3 fig. 1.

Siphonidium ramosum ; Schmidt 1879: 28, pl. 1 fig. 8; Van Soest & Stentoft 1988: 66, text-fig. 31; Pisera & Lévi 2002: 342, figs 6–8; Mothes & Silva 1999: figs 27–32, 42–46.

Material examined. RMNH Por. 9824, Suriname, ‘Luymes’ Guyana Shelf Expedition, station 1, 7.1667°N 53.5833°W, depth 104–130 m, bottom sandy calcarenite, 24 August 1970 .

Description. Cushion-shaped sponge ( Fig. 66 a) with characteristic ‘cut-off’ fistules spread over the surface. Size of single specimen 3 x 2.5 x 2.5 cm, individual fistules 2–4 mm in diameter. Color in alcohol orange–beige. Surface overgrown by sponges, bryozoans, vermetids and serpulids. Consistency hard.

Skeleton. ( Figs 66 b–c) At the surface there is a special, dense, tightly interlocking mass of knobby desmas ( Fig. 66 b), overlying a more open choanosomal skeleton of rhizoclone desmas ( Fig. 66 c) with smooth cladi provided with strongly tuberculated zygomes. Bundles of exotyles are arranged at right angles to and slightly protruding from the surface.

Spicules. ( Figs 66 b–d) Desmas, exotyles.

Rhizoclone desmas, of the surface skeleton ( Fig. 66 b) 150–200 µm diameter, tuberculated but tending to be smooth at the parts facing outwards.

Rhizoclone desmas of the choanosome ( Fig. 66 c) 200–300 µm in diameter, smooth part of the cladi 30–50 µm in diameter, zygomes approximately 100 µm.

Exotyles ( Figs 66 d,d1), tylostyle-like but with heads protruding outwards and rugose or irregularly spined, pointed ends occasionally wispy or bluntly rounded, in a large size range, 252– 313 –438 x 3.5– 5.3 –7.5 µm.

Distribution and ecology. Guyana Shelf, Florida, Barbados, SE Brazil, (reported also from E Atlantic and Mediterranean), hard sandy bottom at 104–439 m (previously 150–439 m).

Remarks. A widespread species in the Central West Atlantic (common at 150 m off Barbados, rare elsewhere). It is reported along the SE Brazilian coast at 30°S and also—if the same species—at greater depths in the Azores and the Mediterranean. Size of the exotyles varies among the localities, but the holotype (measurements of Mothes & Silva 1999, table 1) and the present measurements are in the same range. The Azores specimen described by Topsent (1904) had exotyles of 800– 1000 x 4–6 µm, distinctly longer than the known Caribbean measurements. Further research must establish if S. ramosum may have been erroneously reported from the East Atlantic .

Figures

FIGURE 66. Siphonidium ramosum (Schmidt, 1870), a, habitus of RMNH Por. 9824 (scale bar = 1 cm), b, ectosomal desma skeleton, c, choanosomal desma skeleton, d, exotyle, d 1, detail of exotyle showing roughened tyle.