Desmacella koltuni Göcke & Janussen, 2013, sp. nov.

Desmacella koltuni sp. nov.

(Fig. 17, Tab. 13)

Synonymy:

? Tylodesma sp. Koltun 1976: 177, fig.5.

Material. 1 specimen from station 048-1 (SMF 11799, holotype), 602.1 m, 70° 23.94' S, 8° 19.14' W, 12.01.2008.

Diagnosis. Upright tubular sponges with bristle surface. Skeleton poorly organized, plumose tracts of styles with bouquets of smaller styles added in the ectosome. Spicules large styles 810 to 1175 (mean 1030) x 20 to 32.5 (mean 28) µm, small styles 370 to 500 (mean 428) x 8.75 to 12.5 (mean 11) µm and sigmas 30 to 37.5 (mean 34) x 16.25 to 20 (mean 18) µm.

Description. Specimen (Fig. 17 A) complete, but damaged about one third above the base. Sponge growing upright, tubular, widening towards the upper end, about 80 mm high with a maximal diameter of about 30 mm. Basal attachment site with diameter about 10 mm. Without distinct large osculum, but Surface bearing many small pores/oscula. Sponge rather dense, without inner cavity, but a system of aquiferous canals present, firm, but compressible. Surface bristled by short protruding spicule bundles. Color in alcohol greyish yellow.

Skeleton: Skeleton not well organized, based on long plumose tracts of large styles which run towards surface (Fig. 17 B). Tracts not consistent, their thickness and composition changing regularly, confusedly interconnected by single large styles. Large styles in choanosome sometimes accompanied by small styles. At the end of tracts, in ectosome, bundles or bouquets of small styles added, forming the bristly sponge surface. Numerous sigmas occuring free within entire tissue.

Spiculation (Tab. 13): 1. large styles (Fig. 17 C), 810 to 1175 (mean 1030) µm in length, 20 to 32.5 (mean 28) µm in diameter. These often slightly bent about one third from the blunt end, otherwise mostly straight. Acute top end often blunted, giving style the character of a pseudo-strongyle, while identity as a style still recognizable from differences between the two endings. 2. small styles (Fig. 17 D) 370 to 500 (mean 428) µm in length, 8.75 to 12.5 (mean 11) µm in diameter. These mainly straight, rarely slightly bent similar to large ones. 3. microscleres small sigmas (Fig. 17 E–F), 30 to 37.5 (mean 34) µm in length, 16.25 to 20 (mean 18) µm in width, mainly c-shaped, sometimes slightly distorted, rarely s-shaped.

Etymology. The species is named after Vladimir Mikhailovich Koltun (1921–2004), Russian sponge taxonomist, who reported the first probable fragmentary specimens but did not describe them as a species.

Remarks. Our specimen seems to be identical with those reported by Koltun (1976) as Tylodesma sp. The spicules are of the same size and shape (compare Tab. 13), also skeletal arrangement seems to be very similar (not figured by Koltun 1976). Koltun’s (1976) specimens were just five small fragments, so he did not describe a species on their basis, but he already mentioned them to be very probably something new. For genus assignment, we chose to follow Koltun’s (1976) decision, but as the genus Tyloderma has been synonymized with Desmacella (see Hajdu & van Soest 2002), our species assignment has to follow this taxonomic action and the species is now described as Desmacella. The species differs from the two already known from Antarctica (according to Sara et al. 1992), Desmacella vestibularis (Wilson 1904) and Desmacella alba (Wilson 1904), in having styles instead of tylostyles. Styles are quite uncommon in the genus Desmacella, only two species currently listed in the World Porifera Database (van Soest et al. 2012a) having styles instead of tylostyles. Desmacella digitata (Lévi 1960) has styles 180–270 x 6–23 µm (Lévi 1960), thus being much smaller than the ones in our new species. Styles are also present in Desmacella polysigmata van Soest, 1984, which are c. 513–635 x 10–19 µm in size (van Soest 1984) and share an interesting peculiarity with our new species, as the tips of styles in D. polysigmata are often blunted, much as in D. koltuni sp. nov. Still, the lack of a smaller category of styles and the relative small sizes of styles are distinctive differences. One species, Desmacella suberitoides (Burton 1932) has spicules in two different size classes, with the smaller forming palisade-like ectosomal structures, as in our new species. But these spicules are exclusively tylostyles (Burton 1932). In having styles, the new species also shows a strong similarity to Biemna Gray, 1867, which has a similar, but denser skeleton (Hajdu & van Soest 2002). Three species of that genus are known from the Antarctic (Ríos & Cristobo 2006). These are Biemna chilensis Thiele, 1905, Biemna macrorhaphis Hentschel, 1914 and Biemna strongylota Ríos & Cristobo, 2006. All these species have raphides and only one size category of megascleres. Furthermore, B. strongylota has strongyles instead of styles (Ríos & Cristobo 2006).