Sarostegia oculata, TOPSENT, 1904

Dohrmann, Martin, Göcke, Christian, Janussen, Dorte, Reitner, Joachim, Lüter, Carsten & Wörheide, Gert, 2011, Systematics and spicule evolution in dictyonal sponges (Hexactinellida: Sceptrulophora) with description of two new species, Zoological Journal of the Linnean Society 163 (4), pp. 1003-1025 : 1009-1011

SAROSTEGIA OCULATA TOPSENT, 1904

Material examined: One specimen ( HBOI 25 -V-06- 2-001, SMF 11034) collected 25.v.2006 by Johnson- Sea-Link II east of Miami Terrace , south-west of Bimini, 25°38′N, 79°24′W, on a 10–20° slope, depth 745 m.

Additional material examined: One specimen (ZMA Por.3868) collected 8.vi.1982 at Sao Tiago, Cap Verde, 14°49′N, 24°45′W, depth 600–675 m. One specimen of Claviscopulia facunda (MCZ 6711n) collected 21.ii.1879 during the Agassiz expedition 1878–79, Blake Caribbean Island Exploration (C.I.E.), St. Vincent, st. 232, 13°07′N, 61°07′W, 159 m depth .

Description: Body shape tubular, arborescent, more or less branching, attached by a basal plate, branches cylindrical to subcylindrical ( Fig. 3 ). Specimen examined is 53 mm high and diameter of the tubes 3–7 mm, gradually increasing from base to top. Atrial cavity narrow, 2–3 mm diameter, extending throughout most of the body. Surface of the specimen occupied by (?symbiotic) zoanthids as previously reported for this species (see Reiswig, 2002b). One of the tubes contained a large polychaete, which filled out the entire inner cavity ( Fig. S1 ). Parietal oscula 0.6– 2 mm distributed at the sides of branches at intervals of 6–8 mm. Colour in ethanol preserved white to pale brown.

Skeleton ( Figs 4–5 , Table 3): Irregular dictyonal framework of hexactins with triangular and quadrangular meshes. Beams are microtuberculated, mesh sides 119–333 Mm, beam thickness 14–48 Mm. Dermalia are microspined hexactins with short distal ray, tangential rays 250–320 Mm and proximal ray 230– 340 Mm length, probably choanosomal oxyhexactins spiny with unpaired rays measuring 78–150 Mm and tangential rays 58–100 Mm. Microhexactins of similar dimensions are commonly found attached by one ray to the dictyonal framework. Sceptrules are sarules, 308–400 mm long, with 15–30 secondary rays, some of which are fused almost all the way to the top. The axial cross of the sarules lies in the basal part of the head. Uncinates are present in two size ranges: All measurements in Mm.

D, diameter; L, length.

large ones, length 720–1030 Mm, and smaller ones, length 400–650 Mm. Microscleres are oxyhexasters, 60–90 Mm diameter, primary rays 30–43 Mm long, usually occurring as holoxyhexasters ( Fig. 4F ), but also occasionally as hemioxyhexasters ( Fig. 5E ), and discohexasters with hooked spines, variable in size and number of secondary rays, diameter 35–60 Mm, length of primary rays 16–30 Mm, number of secondary rays five to seven.

Remarks: The placement of Sarostegia in Farreidae ( Reiswig, 2002b) was based on the hypothesis that its sarules are homologous to those of Claviscopulia . However, this interpretation is debatable, as the sarules of the two genera show clear differences. In Sarostegia the sarules tend to have short, scale-like secondary rays often fused almost to the top, leading to a pine-cone like appearance of the sceptrule head ( Figs 1 , 4 , 5 ). The sarules of Claviscopulia facunda ( Schmidt, 1870) tend to have fewer secondary rays (ten to 15), which are clearly differentiated from the sceptrule head giving it a brush-like shape ( Fig. 1 ; see also Mehl, 1992: pl. 6, figs 1, 2). Considering the euretoid nature of the dictyonal framework in Sarostegia , the absence of clavules, and the strong molecular evidence against its placement in Farreidae (see above), we transfer Sarostegia back to Euretidae , in line with Topsent (1928) and Reid (1958; see also Reid, 1963).

Sarostegia oculata was previously only known from the Indian Ocean, Cap Verde Is., and south-east Brazil ( Reiswig, 2002b; Tabachnick et al., 2009); this is the first report from the north-west Atlantic. The collection depth of the new specimen (745 m) is well within the known range for this species (256–1829 m; Reiswig, 2002b).

EVOLUTION OF SCEPTRULOPHORAN SPONGES 1011

Figures

Figure 1. Sceptrules. A, regular scopule (from Heterochone sp.). B, regular (pileate) clavule from Farrea sp. (courtesy H. M. Reiswig). C–D, unusual sceptrule types. C, from left to right: sarule (left: Sarostegia, right: Claviscopulia), lonchiole (Lonchiphora; interpreted from text-description), aspidoscopule (Aspidoscopulia). Redrawn from Reiswig (2002b); D, two types of lonchioles from Lonchiphora antarctica (Göcke & Janussen, 2011).

Figure 3. Sarostegia oculata. Piece of the original specimen described herein seen from both sides. Scale bars = 10 mm.

Figure 4. Sarostegia oculata, skeleton. A-B, sarules (A, scale bar = 30 Mm; B, scale bar = 50 Mm). C, dictyonal framework (scale bar = 150 Mm). D–E, discohexasters (scale bars = 10 Mm). F, oxyhexaster (scale bar = 10 Mm).

Figure 5. Sarostegia oculata, spicules: A, uncinate. B, sarule. C, choanosomal hexactin. D, dermal hexactin. E, hemioxyhexaster. F, discohexaster.