Theonella atlantica Van Soest & Stentoft, 1988

Van, Rob W. M., 2017, Sponges of the Guyana Shelf, Zootaxa 1, pp. 1-225 : 104

Theonella atlantica Van Soest & Stentoft, 1988

Figures 64 a–f

Theonella atlantica Van Soest & Stentoft, 1988: 48 , pl. VI figs 5–6, text-fig. 21; Van Soest et al. 2014: table 2 (p. 436), fig. 21b; Pisera & Pomponi 2015: 1302, figs 2A–E, 4–5.

Material examined. RMNH Por. 9825, Suriname, ‘Luymes’ Guyana Shelf Expedition, station 1, 7.1667°N 53.5833°W, depth 104–130 m, bottom sandy calcarenite, 24 August 1970 .

Description. ( Fig. 64 a) Three short stubby, stalked sponges with smooth surface. Largest individual/fragment, 3.5 cm high, 2 cm in diameter. Color beige in alcohol. Consistency stony, rough to the touch.

Skeleton. At the surface there is a regular cover of smooth phyllotriaenes. Microscleres densely strewn over the cladi of the phyllotriaenes. Choanosomal skeleton a dense and strongly zygosed desma skeleton ( Fig. 64 b) and occasional bundles of thin oxeotes arranged at right angles to the surface.

Spicules. ( Figs 64 b–f) Tetraclone desmas, oxeas, phyllotriaenes, and microrhabds.

Desmas ( Fig. 64 b), smooth inner branches but peripherally the cladi have strongly tuberculated zygomes. Spicules overall approximately 400 µm in size, individual cladi 50–100 µm in diameter.

Oxeas ( Figs 64 c,c1), thin, wispy endings, relatively few in number, 350– 1050 x 3 –7.7 µm.

Phyllotriaenes ( Figs 64 d,d1,e), with smooth, irregular cladi ( Figs 64 d1), subdivided into primary, secondary and often also tertiary cladi, overall cladome sizes 660–875 µm, rhabdomes conical ( Figs 64 d), 65–180 x 30–40 µm. Juvenile spicules ( Fig. 64 e) are triaenes with rough surface and three conical cladi.

Acanthomicrorhabds ( Figs 64 f), fusiform, with bluntly pointed apices, densely covered with compound spines, 9–16 x 2.5–3.5 µm.

Distribution and ecology. Guyana Shelf, Barbados, Bonaire, Florida, hard sandy bottoms, 63–161 m ( Guyana Shelf 104–130 m).

Remarks. The Suriname specimens are closely similar to those of Barbados and Bonaire. Pisera & Pomponi (2015) (p. 1303) gave an extensive description of Florida specimens of the species and their data also match closely. These authors also discovered a second Theonella species among the Florida material, T. wrightae Pisera & Pomponi, 2015 , differing from T. atlantica by having oscules on slight elevations at the side of long branches, and a remarkable suite of ectosomal spicules from phyllotriaenes merging into discotriaenes, which also may have tubercles on the upper side. The acanthomicrorhabds of T. wrightae show a much larger variation in length and include cylindrical acanthorhabds of up to 38 µm.

Figures

FIGURE 64. Theonella atlantica Van Soest & Stentoft, 1988, a, habitus of RMNH Por. 9825 (scale bar = 1 cm), b, SEM image of desma skeleton, c, oxeote, c 1, details of c, d, phyllotriaenes underside, d 1, phyllotriaene upperside, e, juvenile phyllotriaene, f, acanthomicrorhabds.