Comprehensive DescriptionRead full entry
Material: Three specimens from EASIZ.
Locality: Weddell Sea, EASIZ st. 39-18 (AGT 4b), depth 1538–1543 m.
Body: This species is represented by fragments, one of which seems to be tubular. The confused spicule positions and their (partly damaged) condition in light microscopy correspond to spicule mats and it is obvious that the sponges were captured in a condition of disintegration, except for one fragment which contains spicules in natural position.
Spicules: Choanosomal spicules are diactines. Hypodermalia are pentactines with rough and spiny tangential rays. Only one dermal spicule was found, a tauactine with rough conically pointed outer ends, its ray is 0.2/0.015 mm. Atrialia are relatively numerous hexactines with rough and conically pointed rays. The proximal ray is about 0.5 mm long, distal one is 0.26 mm long, tangentials 0.13 mm long, diameter is 0.006–0.015 mm. Microscleres: Discoctasters and various oxyoidal forms: oxyhexasters, oxyhemihexasters and oxyhexactines with 4–5 rays. The discoctasters have 1–4 secondary rays, they are 0.15–0.17 mm and their primary rosette 0.06–0.07 mm in diameter. Oxyoidal microscleres are 0.09–0.14 mm in diameter.
Remarks: The differences between the spicule dimensions of our new specimens and that described by Topsent are not significant. The oxyoidal microscleres are smaller: 0.09–0.14 mm in diameter in our specimen and 0.14–0.16 mm in the type material (Topsent, 1910), and the discoctasters are smaller as well, respectively, 0.15–0.17 and 0.18 mm in diameter. No microdiscohexasters are present. This species has been considered a synonym of Rossella antarctica (Burton, 1929; Barthel and Tendal, 1994), but was recently revived (Tabachnick, 2002b K.R. Tabachnick, Family Rossellidae Schulze, 1885. In: J.N.A. Hooper and R.W.M. van Soest, Editors, Systema Porifera: A Guide to Classification of Sponges Vol. 2, Kluver Academic/Plenum Publishers, New York (2002), pp. 1453–1505.Tabachnick, 2002b). Another specimen described as Rhabdocalyptus australis by Okada (1932) seems to be erroneousely identified; its description is insufficent for comparison and the same is true for the data on dimensions of large spicules, choanosomal diactines and hypodermal pentactines.
Distribution: This species was previously known only from a single report off Antarctica (west of the Antarctic Peninsula), depth 450 m. In the light of unpublished materials of the ‘Eltanin’ expedition the distribution of this species appears to be circumantarctic. Depth 450–1543 m.”
(Janussen et al., 2004:1866)