Uteopsis argentea ( Poléjaeff, 1883 )

Uteopsis argentea ( Poléjaeff, 1883) View in CoL

Figures 55a–b View FIGURE 55 , 56a–c View FIGURE 56 , 57a–g View FIGURE 57

Ute argentea Poléjaeff, 1983: 43 , pl. I fig.3, pl. IV fig.3, pl. V figs 1a–p; Dendy, 1893a: 92.

Uteopsis argentea View in CoL ; Dendy & Row, 1913: 769; Burton, 1930: 5, fig. 3; Burton, 1963: 530.

Sycon sp. ; Colin & Arneson, 1995: 61, photo 238.

Material examined. ZMA Por. 00155, Indonesia, Lesser Sunda Islands, West Timor, Samau Island , Haingsisi , 10.205°S 123.4591°E, depth 23 m, trawled, coll. Siboga Expedition stat. 060, 27 April 1899 GoogleMaps ; ZMA Por. 00182, Indonesia, Irian Jaya, 1.7083°S 130.7916°E, depth 32 m, trawled, coll. Siboga Expedition stat. 164, 20 August 1899 GoogleMaps ; RMNH Por. 1871, Indonesia, NE Kalimantan, Berau Islands, off Tanjung Batu , 2.2396°N 118.0934°E, 10– 15 m GoogleMaps , SCUBA, coll. B.W. Hoeksema, #BER.19/091003/158, East Kalimantan-Berau Expedition 2003, 9 October 2003 ; RMNH Por. 2598, Singapore, Pulau Subar Laut , NW, 1.2°N 103.83°E, depth 6 m GoogleMaps , SCUBA, coll. N.J. de Voogd, #SIN22/040406/160, 4 April 2006 ; RMNH Por. 6593, Indonesia, North Sulawesi, Lembeh Strait, Pulau Abadi , 1.4336°N 125.2062°E, depth 30 m GoogleMaps , SCUBA, coll. B.W.Hoeksema, #LEM22/100212/104, 10 February 2012 .

Description. Bush of thin tubes ( Figs 55a–b View FIGURE 55 ). Individual tubes up to 8 cm high, 3–4 mm in diameter, maintaining this diameter over most or all their length. Tubes may divide into two at a short distance above the substratum, but are unbranched for most of their length. Terminal oscules provided with a very short lighter colored fringe. Smooth surface, tough-hard consistency. Color pale brown.

Histology. Syconoid aquiferous system ( Fig. 56b View FIGURE 56 ), with oval-rounded choanocyte chambers.

Skeleton. ( Figs 56a–c View FIGURE 56 ) Strong, dense cortex of aligned tangential giant diactines ( Fig. 56a View FIGURE 56 ), covered by a thin layer of small equiangular or sagittal triactines and scattered small diactines. Choanosomal skeleton inarticulate ( Fig. 56b View FIGURE 56 ), thin and predominantly formed by the unpaired actines of subatrial sagittal triactines, with a minority of similar tetractines. Atrial skeleton of small sagittal tetractines and triactines, with scattered small diactines.

Spicules. ( Figs 57a–g View FIGURE 57 ) Giant diactines, small diactines, triactines, tetractines.

Giant diactines ( Fig. 57a View FIGURE 57 ) from the cortex, 1200– 2170.0 –3600 x 36– 60.6 –78 µm.

Small diactines ( Fig. 57b View FIGURE 57 ), 105– 211.0 –360 x 1.5– 3.4 –8 µm.

Triactines from the cortical skeleton ( Fig. 57c View FIGURE 57 ), unpaired actines 96– 104.7 –126 x 6– 6.1 –6.5 µm, paired actines 60– 75.2 –93 x 6– 6.7 –7 µm.

Triactines from the choanosome ( Fig. 57d View FIGURE 57 ), unpaired actines 252– 430.4 –576 x 5– 7.8 –11 µm, paired actines 96– 180.6 –258 x 5– 8.6 –9 µm.

Triactines from the atrial skeleton ( Fig. 57e View FIGURE 57 ), unpaired actines 99– 121.2 –135 x 4– 5.1 –7 µm, paired actines 142– 155.3 –165 x 6– 7.0 –9 µm.

Tetractines from the choanosome ( Fig. 57f View FIGURE 57 ), unpaired actines 250– 301.7 –384 x 8– 8.1 –8.5 µm, paired actines 126– 159.0 –181 x 6 –8.3 –11 µm, apical actines 45–58 x 6 µm.

Tetractines from the atrial skeleton ( Fig. 57g View FIGURE 57 ), unpaired actines 96– 185.3 –312 x 5– 5.7 –6 µm, paired actines 96– 114.0 –129 x 5– 6.7 –8 µm, apical actines 20–24 x 4 µm.

Ecology. Deeper parts of the reefs.

Distribution. Indonesia, elsewhere South Australia.

Remarks. The type of Uteopsis argentea from the SE coast of Australia is similar in shape and overall spiculation, but there are a few discrepancies. Atrial tetractines of the type have much shorter unpaired actines, and the unpaired actine of the choanosomal triactines may be up to 750 µm in length. These differences are considered too small for specific separation. Future records of the species may find consistent differences among the widely separated populations.