Biemna rhabdotylostylota, Van, Rob W. M., 2017

Van, Rob W. M., 2017, Sponges of the Guyana Shelf, Zootaxa 1, pp. 1-225: 68-70

publication ID 10.5281/zenodo.272951

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scientific name

Biemna rhabdotylostylota

sp. nov.

Biemna rhabdotylostylota  sp. nov.

Figures 44View FIGURE 44 a –j

Material examined. Holotype RMNH 9927View Materials, Suriname, ‘ Snellius O.C.P.S. ’ Guyana Shelf Expedition, station G7, 7.28°N 56.7933°W, depth 64 m, bottom sand, 7 May 1966GoogleMaps  .

Description. ( Fig. 44View FIGURE 44 a) Sponge consolidating an irregularly curled mass of rubble, shell debris and sand, size about 10 cm long and 2.5 wide and thick. Sponge recognized as a glassy, grayish, smooth tissue (in alcohol) cementing white and brown foreign objects.

Skeleton. ( Fig. 44View FIGURE 44 b) Not clearly differentiated, largely confused, with larger megascleres singly erect on pieces of calcareous matter, carrying a membrane charged with microscleres.

Spicules. ( Figs 44View FIGURE 44 c –j) Tylostyles, rhabdotylostyles, sigmas, dragmas of microxeas.

Tylostyles ( Figs 44View FIGURE 44 c –d), smooth, curved gently, especially in the proximal part below the tyle, tapering to thinner, but often bluntly rounded endings ( Fig. 44View FIGURE 44 c1), in a large size range, not clearly divisible in two distinct sizes, larger ( Fig. 44View FIGURE 44 c) 690–936 x 5.5–8.5 µm, smaller ( Fig. 44View FIGURE 44 d) 237–456 x 2 –5.5 µm), overall 237– 571 –936 x 2 –4.9–8.5 µm.

Rhabdotylostyles ( Figs 44View FIGURE 44 e –f), smooth, abruptly curved just below the tyle, gradually tapering to a sharp ending ( Fig. 44View FIGURE 44 f1), in a large size range, not clearly divisible in two distinct sizes, larger ( Fig. 44View FIGURE 44 e) 207–387 x 4 –7.5 µm, smaller ( Fig. 44View FIGURE 44 f) 78–189 x 1–5 µm), overall 78– 181 –387 x 1 – 4.4 –7.5 µm.

Sigmas ( Figs 44View FIGURE 44 g –h), small and thin, with faint roughening of the apices, divisible in two distinct size ranges, (1) larger ( Fig. 44View FIGURE 44 g) 13– 15.3 –18 µm, (2) smaller ( Fig. 44View FIGURE 44 h) 6– 8.0 –9 µm.

Microxeas ( Figs 44View FIGURE 44 i –j), smooth, straight, fusiform, arranged in tightly developed trichodragmas, in two distinct size categories, (1) long ( Figs 44View FIGURE 44 i, i1) 198– 253 –301 x 6 – 10.4 –17 µm, (2) short ( Figs 44View FIGURE 44 j,j1) 24– 30.4 – 36 x 6 – 9.5 –12 µm.

Distribution and ecology. Guyana Shelf, on sand bottom at 64 m depth.

Etymology. The name reflects the shape of the smaller megascleres.

Remarks. The new species is assigned to the Biemnida  by its combination of microxeas in dragmata and sigmas with roughened apices. The megascleres are unique among Central West Atlantic Biemna  species by being a diverse combination of tylostyles and rhabdotylostyles. The known Central West Atlantic species Biemna caribea Pulitzer-Finali, 1986  , B. microacanthosigma Mothes, Hajdu, Lerner & Van Soest, 2004  , B. microstyla De Laubenfels, 1950  , and B. trisigmata Mothes & Campos, 2004  , all have styles as megascleres, while B. cribraria ( Alcolado & Gotera, 1986)  and B. spinomicroxea Mothes, Campos, Lerner, Carraro & Van Soest, 2005  have oxeas or strongyles as megascleres. The megascleres are all in a single category, not differentiated in shape and size as in the new species.

Rhabdose megascleres are found in New Zealand Biemna rhabderemioides Bergquist, 1961  and in Namibian B. rhabdostyla Uriz, 1988  . In both species, the megascleres are styles, not tylostyles. The Namibian species is closest to the new species in having a diverse megasclere complement of longer styles (up to 1200 µm) and smaller rhabdostyles (up to 215 µm). Apart from lacking tylostyles it differs also in having three categories of sigmas, the largest of which are up to 112 µm.

The above described morphological characters of the present new species make it an atypical Biemna  species. A future revision of the genus may result in assignment to a separate, so far undescribed, genus along with B. rhabdostyla  .


National Museum of Natural History, Naturalis