Sycetta vinitincta, Van Soest & De Voogd, 2015

Sycetta vinitincta View in CoL sp. nov.

Figures 44a–e View FIGURE 44 , 45a–e View FIGURE 45 , 46a–h View FIGURE 46

Material examined. Holotype RMNH Por. 1873, Indonsesia, NE Kalimantan, Berau Islands, Samama Island , 2.1254°N 118.336°E, depth 2 m, SCUBA, coll. B.W. Hoeksema, #BER10/071003/053, Berau 2003 Expedition, 7 October 2003. GoogleMaps

Paratype ZMA Por. 08633, Indonesia, SE Sulawesi, Salayar, SW coast, off the NW coast of Pulau Guang, 6.35°S 120.45°E, depth 4–12 m GoogleMaps , SCUBA, coll. R. W.M. van Soest, Indonesian-Dutch Snellius II Expedition stat. 152 / III/15 , 29 September 1984 .

Additional material. ZMA Por. 08221b, Indonesia, SE Sulawesi, Tukang Besi Islands , southern reef of Karang Kaledupa, 5.9333°S 123.8°E, depth 4–11 m GoogleMaps , SCUBA, coll. R. W.M. van Soest, Indonesian-Dutch Snellius II Expedition stat. 016 / III/10 , 8 September 1984 .

Description. Wine-red irregular broadly sac-shaped thin-walled tubes ( Figs 44a–c View FIGURE 44 ), with irregular-shaped knob-like side-tubes (diverticula?). In alcohol the specimens become white ( Fig. 44d View FIGURE 44 ). Surface of tube and side projections is covered in tiny rounded papillae of up to 0.5 mm in height and width ( Fig. 44b View FIGURE 44 ). Size of entire specimens up to 4 cm high, individual side-tubes, up to 3 cm long and 8 mm in diameter, overall the sponge may be 4–5 cm wide, atrial lumen up to approximately 2 cm in diameter. Consistency soft and easily damaged.

Histology. No histological section was made, but thin hand sections of the skeleton indicate that it has a probable syconoid aquiferous system ( Fig. 45a–c View FIGURE 45 ), but with choanocyte chambers shallow and closely adjacent to each other in the papillae. See also the Remarks below.

Skeleton. ( Figs 45a–e View FIGURE 45 ) The walls of the atrial tube and the side-tubes bear continuous close-set semi-globular (‘alveolar’) papillae ( Figs 45a–b, d View FIGURE 45 ). Spicules of these alveolar papillae are predominantly characteristic ‘oxhornshaped’ small triactines and tetractines (with upturned paired actines) in a single layer, but near the atrial lumen there is an additional subatrial smaller sagittal triactine spicule located ( Fig. 45b–c View FIGURE 45 ), differing from the alveolar oxhorn-shaped spicules in having the paired actines recurved. The atrial wall ( Fig. 45c, e View FIGURE 45 ) is supported by regular larger tri- and tetractines, predominantly tetractines and smaller sagittal tri- and tetractines with paired actines almost in one plane and characteristic short unpaired actines. The skeletal structure of this species might be interpreted as inarticulate.

Spicules. ( Figs 44e View FIGURE 44 , 46a–h View FIGURE 46 ) Regular equiangular equiactinal triactines and tetractines in two size categories, oxhorn-shaped sagittal triactines and tetractines, small sagittal tri- and tetractines in two categories.

Atrial triactines ( Fig. 46a View FIGURE 46 ) with unpaired actine up to 330– 444.3 –530 x 8– 10.3 –13 µm, paired actines up to 190– 378.8 –489 x 9– 10.5 –13 µm.

Atrial tetractines ( Figs 46b, f View FIGURE 46 ) often with shorter unpaired actine, up to 210– 359.2 –479 x 9– 11.8 –14 µm, paired actines up to 240– 396.6 –426 x 9– 10.7 –12 µm, and apical actines 18– 21.8 –34 x 4– 6.6 –10 µm.

Triactines with recurved actines ( Fig. 46e View FIGURE 46 ), unpaired actines 149– 176.8 –242 x 7.5– 8.3 –9 µm, paired actines 108-126.4-135 x 6.5-7.6- 9 mm.

Triactines of the alveolar papillae, oxhorn-shaped ( Fig. 46c View FIGURE 46 ), with unpaired actines 28– 68.0 –123 x 5– 6.2 –8 µm, paired actines 91– 110. 2–129 x 5– 5.9 –8 µm.

Tetractines of the alveolar papillae, oxhorn-shaped ( Fig. 46d View FIGURE 46 ), with unpaired actine up to 48– 106.1 –180 x 8 µm, paired actines up to 93– 120.8 –135 x 6– 6.8 –8 µm and apical actine approximately 20– 36.5 –61 x 4.5– 5.6 –7 µm.

Atrial triactines, sagittal, with short unpaired actines ( Fig. 46g View FIGURE 46 ), and paired actines almost in one plane, unpaired actines 68– 89.3 –112 x 7– 8.3 – 10 mm, paired actines 153– 174.3 –193 x 8– 9.2 – 11 mm.

Atrial tetractines, sagittal, with short unpaired actines ( Fig. 46h View FIGURE 46 ) and paired actines almost in one plane, unpaired actines 18– 33.2 –53 x 8– 8.6 – 11 mm, paired actines 88– 172.0 –361 x 8– 8.8 – 10 mm, apical actines 25– 47.4 –95 x 7– 8.1 – 9 mm.

Ecology. Shallow-reefs.

Distribution. So far known only from Indonesia, at Salayar and the Berau region.

Etymology. The word vinum (L.) means wine, tinctus (L.) means colored, referring to the wine-red color of the species.

Remarks. The genus assignment is tentative. Among Calcaronea, the papillate surface and a wall of alveolar choanocyte chambers only occur in the poorly known genus Sycetta , with type species the Indian Ocean S. sagittifera ( Haeckel, 1872) , and other species the Mediterranean S. conifera ( Haeckel, 1872) , and two Antarctic species, S. antarctica Brøndsted, 1931 and S. primitiva ( Brøndsted, 1931) (originally as Tenthrenodes ). The spicule shapes and sizes of these species are clearly different from those of the present species, especially the Indian Ocean S. sagittifera , which lacks tetractines. Oliver Voigt (personal communication) made histological sections of the paratype, ZMA Por. 08633, and this confirmed that the alveolar structures are indeed syconoid choanocyte chambers, with choanocytes lining the entire internal walls. He pointed out that there is a great similarity in skeletal structure and histology with the South Australian ‘Sycon’ carteri Dendy, 1893 . The two are probably closely related, differing in habitus (‘ S.’ carteri is a strongly divided bush of thin orange colored tubes) and spiculation (‘ S.’ carteri has brushes of short diactines on the papillae). Molecular work ( Voigt et al. 2012) also demonstrated that ‘ S.’carteri is in its turn closely related to Leucascandra caveolata Borojevic & Klautau, 2000 (described also in Lévi et al. (1998: 79). This species is rather more distinct in habitus and skeletal features: it is a dense mass of orange–brown, smooth, delicate tubes provided with thinner side tubes, the walls of the tubes are ‘caveolate’, i.e. rounded-syconoid (our interpretation), and there is a distinct cortex. There is no papillate surface as in Sycetta vinitincta sp.nov. and ‘Sycon’ carteri , but the three species share similar oval syconoid choanocyte chambers and the inarticulate skeleton. Leucascandra is at present assigned to the family Jenkinidae , which is, however, postulated to be polyphyletic ( Voigt et al. 2012; Dohrmann et al. 2006).

Genus Sycon Risso, 1827