Sycon spec.

Sycon spec.

Figures 47a–d View FIGURE 47 , 48a–e View FIGURE 48

? Sycon raphanus var. tergestinum View in CoL ; Breitfuss, 1896: 434; Breitfuss, 1898: 173 (not: Haeckel, 1872)

Material examined. ZMA Por. 15509d, Indonesia, SE Sulawesi, SW Salayar, NW coast of Pulau Guang , 6.35°S 120.45°E, depth 3–4 m GoogleMaps , SCUBA, H.A. ten Hove, Indonesian-Dutch Snellius II Expedition stat. 152/ Cave 1/A3, 28 September 1984 .

Description. Tiny sponge ( Fig. 47a View FIGURE 47 ), 4 mm high, 3 mm in diameter. Color cream in alcohol. Oscules provided with silvery white-opaque stiff dense fringe, underneath which there is a loose collar of widespread diactinal spicules ( Fig. 47b View FIGURE 47 , arrows). Surface of main body microconulose-spinose.

Skeleton. Typical radial arrangement ( Fig. 47c View FIGURE 47 ) of tubar spicules lining the syconoid chambers, with distal cones crowned by bouquets of diactines ( Fig. 48f View FIGURE 48 ); atrial skeleton with several layers of triactines; central tube crowned by peripheral fringe of long thin diactines ( Fig. 47b View FIGURE 47 ), at the base of which there is a circle of thick diactines forming a collar. These diactines are also found spread over the body.

Spicules. ( Figs 47d View FIGURE 47 , 48a–f View FIGURE 48 ) Tubar triactines, atrial triactines, fringe diactines, large collar diactines, small diactines of the distal cones.

Diactines of the oscular fringe ( Figs 48a, a View FIGURE 48 1 View FIGURE 1 ), thin, but elongately fusiform, 1000– 1500 x 6–10 µm.

Diactines of the collar ( Figs 48b, b View FIGURE 48 1 View FIGURE 1 ), thick, fusiform, 500–650 x 15–22 µm.

Diactines of the distal cones curved ( Figs 48c, f View FIGURE 48 ), at both ends tapering to sharp points, 120–220 x 5–6 µm.

Tubar triactines ( Fig. 48d View FIGURE 48 ), sagittal, T-shaped, with unpaired actines longer than paired actines, unpaired actines sharply pointed; unpaired actines 90–110 x 5–6 µm, paired actines 45–60 x 4–6 µm.

Triactines of the atrium ( Fig. 48e View FIGURE 48 ), sagittal, T-shaped, with unpaired actines shorter than paired actines, unpaired actines sharply pointed, 45–80 x 6 µm, paired actines 90–100 x 6 µm.

Ecology. Shallow-water reef cave.

Distribution. Indonesia.

Remarks. We consider this description as preliminary and e refrain from naming the present species, because the single specimen was tiny and most of the material was used up in making a few inadequate preparations. The habitus reminds of the Mediterranean Sycon humboldti ( Risso, 1827) , type species of the genus, but that has tetractines. Only few Sycon species lacking tetractines have been described, e.g. Grantia cupola ( Haeckel, 1872) from Japan (it has no diactines), and Sycon grantioides Dendy, 1916 from the Indian Ocean (tubar triactines with unpaired actines twice as long).

Breitfuss’ (1896, 1898) report of the Mediterranean (sub)species Sycon raphanus tergestinum from Ternate may possibly concern our present species. No spicule data were provided by Breitfuss, and, of course, the occurrence of a Mediterranean Sycon species in Indonesian waters is highly unlikely.

New Caledonian Sycon gelatinosum ( Blainville, 1834) , as redescribed by Borojevic & Klautau (2000) and Northeast Australian Sycon capricorn Wörheide & Hooper, 2003 differ strongly from the present material by having a branched tubular habitus, relatively smooth surface, possessing atrial tetractines, and differently shaped spicules.