Stellettinopsis megastylifera Wintermann-Kilian & Kilian 1984

Stellettinopsis megastylifera (Wintermann-Kilian & Kilian, 1984)

Figures 50 a–i

Ecionemia megastylifera Wintermann-Kilian, 1984:122, figs 1–2; Cárdenas et al. 2009: 12, figs 5–6. Stellettinopsis dominicana Pulitzer-Finali, 1986: 67 figs 1–2.

Ancorina megastylifera; Alcolado 2002: 56.

Ecionemia dominicana; Rützler et al. 2000: table 1. Ecionemia sp. Hajdu et al. 2011: 71.

Stellettinopsis megastylifera; Kelly et al. 2012: 31.

Material examined. RMNH Por. 9931, Guyana, ‘Luymes’ Guyana Shelf Expedition, station 63, 7.5833°N 57.0667°W, depth 71 m, sandy bottom, 31 August 1970.

Description. Lumpy-lobate mass (Fig. 50 a) of 6.5 x 4.5 x 4 cm, color red-brown, with a single oscule of 7 mm diameter surrounded by a darker-colored raised rim. Surface encrusted by shells and barnacles, rough to the touch. Consistency hard.

Skeleton. Cortex consisting of microscleres (asters and microrhabds) carried by the cladomes of dichotriaenes and plagiotriaenes, which are arranged radially. Choanosome more confused.

Spicules. (Figs 50 b–i) Oxeas, rare stylote modifications, dichotriaenes, plagiotriaenes, rare protriaenes, acanthoxyasters, acanthostrongylasters.

Large oxeas 1, (Figs 50 b,b1) fusiform, rather abruptly tapering to sharp apices; the styles which give the species its name are obvious modifications of the oxeas, with one end or occasionally two ends rounded; they do not merit status as a separate spicule category, 840– 1161 – 1410 x 14 – 40.7 –59 µm; styles/strongyles, (Figs 50 d,d1), 882–960 x 43 –54 µm.

Small thin oxeas 2 (Fig. 50 c), rare, (n=2), 426–603 x 4–7 µm.

Dichotriaenes (Figs 50 e,e1) with characteristically small orthotriaene-like cladomes, with thick rhabdomes tapering rather abruptly to sharp endings; rhabdomes 804– 907 – 1058 x 30 – 41.7 –51 µm, cladomes 121– 189 –264 µm, primary cladi 42– 48 – 57 x 18 – 31.5 –42 µm, secondary cladi 27– 53 – 72 x 13 – 20.2 –24 µm.

(Plagiotriaenes are similar to dichotriaenes, and may be considered juvenile forms of the dichotriaenes, with shorter rhabdomes and cladi).

Protriaenes (Fig. 50 f), rare (n=3), thin, not certainly proper to the sponge, rhabdomes up to 780 x 5 µm, cladomes 30–66 µm, cladi 15–40 x 2–6 µm.

Microrhabds (Fig. 50 g), entirely finely spined, often centrotylote, apices varying from sharp to bluntly rounded or strongylote, 66– 78 – 99 x 4 – 5.3 –7 µm.

Oxyasters (Fig. 50 h), without thickened center, rays smooth near the center and spined from halfway to the apex, diameter 11– 13.4 –17 µm, with 7–10 rays.

Strongylasters (Fig. 50 i), heavily spined at the apices and along the short shafts, the slightly thickened center is smooth, diameter 5– 6.6 –8 µm, with 6–10 rays.

Distribution and ecology. Guyana Shelf, Colombia, Belize, Dominica, Gulf of Mexico, NE Brazil, on various substratums, rocks mangroves, reefs, and sandy bottoms, from shallow water down to 71 m (previously 3–25 m).

Remarks. Cárdenas et al. 2009 revised this species extensively (as Ecionemia). Our material conforms closely to their description. We did not find anatriaenes, but these were absent also in the holotype and rare in the Belize specimens. We did find a few, mostly broken, pieces of thin small protriaenes, which might possibly be foreign, but since Cárdenas et al. 2009 found these as well, they could be part of the spicule complement of this wide-spread characteristic species. Our assignment of this species to the genus Stellettinopsis Carter, 1879a follows Kelly et al. 2012 (and the World Porifera Database).