Epipolasis tubulata, Van, Rob W. M., 2017

Van, Rob W. M., 2017, Sponges of the Guyana Shelf, Zootaxa 1, pp. 1-225 : 184-185

Epipolasis tubulata sp. nov.

Figures 115 a–g

Material examined. Holotype RMNH Por. 9965 (larger specimen), Suriname, ‘ Snellius O.C.P.S. ’ Guyana Shelf Expedition, station G56, 7.26°N 56.6667°W, depth 67–68 m, Agassiz trawl, 10 May 1966 .

Paratype RMNH Por. 10549 (smaller specimen), same data as holotype.

Description. ( Fig. 115 a) Sponge forms low thick-walled tubes, diameter of the larger tube 1.5 cm, height 2 cm. Largest tube opening 8 mm in diameter. Surface smooth, but irregular around the oscules. Color greyish brown. Consistency compressible. The smaller paratype ( Fig. 115 a1) is similar.

Skeleton. The surface ( Fig. 115 b) is a halichondrioid tangential crust of intercrossing spicule tracts and single spicules, 2–10 spicules in diameter. This is carried by choanosomal spicule tracts ( Fig. 115 c), likewise 2–10 spicules in cross section, surrounded by a largely confused mass of single spicules and numerous single raphides, partially arranged in thin trichodragmas.

Spicules. ( Figs 115 d–g) Oxeote styles, trichodragmas.

Oxeotes, style-like, smooth, slightly fusiform, usually somewhat curved, with a faint subapical constriction, in two distinct size categories, (1) larger ( Figs 115 d,d1), 462– 601 –618 x 12 – 16.3 –19 µm, and (2) smaller ( Figs 115 e,e1), 192– 286 –324 x 5 – 7.4 –9 µm.

Raphides, partially in thin trichodragmas ( Fig. 115 f), but many raphides ( Fig. 115 g) are strewn singly throughout the skeleton; provided with a lanceolate hook at both ends ( Fig. 115 g1), 76– 87 –114 x 0.3–0.4 µm; trichodragmas up to 20 µm in diameter.

Distribution and ecology. Guyana Shelf, at 67–68 m depth.

Etymology. The name refers to the tubular shape of the sponge.

Remarks. The genus assignment is tentative. At first the species was assigned to the axinellid genus Dragmaxia (cf. above), because of the combination of smooth stylote spicules with trichodragmas. However, the clear division into a larger and a smaller category of megascleres added to the tangential halichondrioid ectosomal skeleton, precludes membership of the genus Dragmaxia . So far, Epipolasis has been limited to species with large and small oxeas, although stylote modifications are reported in the type species, Spongosorites suluensis Wilson, 1925 . There is one other Epipolasis in the Central West Atlantic, E. profunda Díaz, Pomponi & Van Soest, 1993 , but this has much larger spicules (up to 1600 x 29 µm), which are predominantly proper oxeas; trichodragmas are only half as long as those of the new species.

Figures

FIGURE 115. Epipolasis tubulata sp. nov., a, habitus of holotype RMNH Por. 9965, a 1, habitus of paratype RMNH Por. 10549 (scale bar = 1 cm), b, light microscopic image of tangential halichondrioid ectosomal skeleton, c, ditto of cross section of peripheral skeleton, d – g, SEM images of the spicules, d, large oxeote style, d 1, details of d, e, small oxeote style, e 1, details of e, f, trichodragma, g, individual raphide, g 1, detail of hooked end of g.