Clathria (Axosuberites) riosae, Van, Rob W. M., 2017

Van, Rob W. M., 2017, Sponges of the Guyana Shelf, Zootaxa 1, pp. 1-225 : 154-156

Clathria (Axosuberites) riosae sp. nov.

Figures 96 a–f

Material examined. Holotype RMNH Por. 9916, Suriname, ‘ Luymes O.C.P.S. II’ Guyana Shelf Expedition, station J112, 7.305°N 54.605°W, depth 88.5 m, 22 April 1969 .

Additional non-type material. RMNH Por. 10511, Suriname, ‘ Snellius O.C.P.S. ’ Guyana Shelf Expedition, station F46, 6.312°N 56.57°W, depth 25–29 m, bottom sand, 7 May 1966 .

Description. ( Fig. 96 a) Small digitate sponge with optically smooth surface encrusting a shell. Overall size up to 3 x 2 x 2 cm. Digitations about 1–2 cm high, 0.5 cm thick. Color in alcohol tan or darker brown. Consistency compressible. A second specimen likely to be the same species is thinly encrusting.

Skeleton. ( Fig. 96 b) The digitations have a thin axial column of styles from which diverge bouquets of styles and subtylostyles, at the surface fanning out to form a more or less continuous ectosomal skeleton. No visible spongin. Styles and subtylostyles intermingled, not localized.

Spicules. ( Figs 96 c–f) Styles, subtylostyles, isochelae.

Styles ( Figs 96 c,c1), straight or curved, with broadly rounded smooth heads, shaft isodiametrical until the sharply pointed apex, in a large size range, 408– 524 –690 x 8 – 14.1 –17 µm.

Subtylostyles, straight, with slight narrowing below the elongated heads which are usually microspined, in a large size range, the larger subtylostyles as long or slightly shorter than the styles, the smaller variably thin to slightly fusiform; subtylostyles arbitrarily divisible in two size categories (possibly three sizes), (1) larger ( Figs 96 d,d1), 366– 478 –540 x 4 – 7.6 –10 µm, and (2) smaller ( Figs 96 e,e1), 174– 241 –303 x 3 – 4.4 –6 µm.

Palmate isochelae ( Figs 96 f), varying in the length of the alae, but otherwise closely similar in shape and size, 19– 20.3 –22 µm.

Distribution and ecology. Guyana Shelf, soft bottom, 25–88.5 m depth.

Etymology. Named after Dr Pilar Ríos (Instituto Español de Oceanografia, Gijon, Spain) in recognition of her excellent contributions to poecilosclerid taxonomy.

Remarks. This is the first record of the subgenus Axosuberites from the Central West Atlantic. Specimen RMNH Por. 10511 is a very thin crust and from greater depth than the holotype, but skeletal structure and spiculation are closely similar to the holotype. To be on the safe side it was decided not to include it in the type material.

The nearest species to this new species is Clathria (Axosuberites) papillat a Van Soest, Beglinger & De Voogd, 2013 from Mauritania in the East Atlantic. This is also basically encrusting with (papillate) digitations, and similarly lacks toxas. The differences are found in the sizes of the spicules, the upper sizes of which are larger in the new species (up to 450 in C. (A.) papillata vs up to almost 700 µm in the new species). The smaller styles often have microspined apices in C. (A.) papillata whereas these are smooth in the new species. Isochelae are also subtly different between the two species.

Cold-water species of the subgenus tend to have more elaborate shape and more diverse microscleres. The type species, C. (A.) fauroti ( Topsent, 1893b) from the Red Sea is a small digitation and it has no microscleres, the West African species and the present new species from tropical Atlantic waters have only palmate isochelae, whereas e.g. the Antarctic C. (A.) flabellata ( Topsent, 1916) (as Ophlitaspongia ), re-described by Ríos et al. (2004), is flabellate-erect with a complement of several chelae and toxa categories.

Figures

FIGURE 96. Clathria (Axosuberites) riosae sp. nov., a, habitus of holotype RMNH Por. 9916 (scale bar = 1 cm), b, light microscopic image of cross section of papilla, c – f, SEM images of the spicules, c, style, c 1, details of c, d, large subtylostyle, d 1, details of d, e, small subtylostyle, e 1, details of e, f, palmate isochelae.