Anamixilla singaporensis, Van Soest & De Voogd, 2015

Van Soest, Rob W. M. & De Voogd, Nicole J., 2015, Calcareous sponges of Indonesia, Zootaxa 3951 (1), pp. 1-105 : 74-76

Anamixilla singaporensis sp. nov.

Figures 53a–c , 54a–d

? Leucosolenia sp. Lim et al. 2008: 163.

Material examined. Holotype RMNH Por. 9350, Singapore, Pulau Subar Laut, NW, 1.2°N 103.83°E, depth 6 m, SCUBA, coll. N.J. de Voogd, #SIN22/040406/160, 4 April 2006.

Description. Small group of whitish or pale beige tubes; a single basal tube may divide into two or three ( Fig. 53a ), ending in wide oscules, with frayed rim or coarse fringe. Diameter of tubes less than 1 cm, length up to 3 cm, usually slightly constricted at the open end. Consistency brittle, easily damaged.

Skeleton. ( Figs 53b–c ) Inarticulate, with a cortical thick layer of giant and intermediate-sized triactines. Choanosomal skeleton ( Fig. 53b ) formed by the unpaired actines of subatrial sagittal triactines. Atrial skeleton ( Fig. 53c ) thin, built by tetractines, with their apical actines protruding into the atrial lumen. The oscular rim has a thin spread of perpendicular trichoxeas.

Spicules. ( Figs 54a–d ) Giant and intermediate triactines, sagittal triactines, tetractines, thin diactines.

Equiangular equiactinal triactines ( Fig. 54a ) of the cortical region, in a wide size range from giant to intermediate sizes, 165– 331.1 –905 x 7– 26.2 –78 µm.

Sagittal triactines ( Fig. 54b ), usually with long unpaired actine and wide-angled to almost straight paired actines, unpaired actines 88– 288.3 –434 x 5– 8.1 –10 µm, paired actines 72– 129.2 –172 x 6– 7.6 –9 µm.

Tetractines ( Fig. 54c ), predominantly regular, but with apical actine often curved, unpaired actines 180– 277.3 – 342 x 8– 10.7 –12 µm, paired actines 182– 204.2 –222 x 8– 8.8 –10 µm, apical actines 42– 58.3 –90 x 6– 7.4 –8 µm.

Thin diactines ( Fig. 54d ), usually broken, approximately 75–210 x 2–3 µm.

Ecology. Shallow water amongst filamentous algae.

Distribution. Known only from the type locality off the coast of Singapore.

Etymology. The name refers to the type locality.

Remarks. The species is close to Anamixilla torresi in skeletal structure and spicular composition, but the habitus of the new species is simply tubular without the flaring trumpet ending of A. torresi , and two spicule types are distinctly different in shape and size. The actines of the giant triactines are only up to 905 µm in the present species, against up to 2000 µ or more in A. torresi . The sagittal triactines of the choanosomal skeleton in our new species have short straight paired actines; the unpaired actines are only up to 434 x 10 µm against up to 602 x 35 µm in A. torresi , which also has the angle of the paired actines more equiangular. Especially the atrial tetractines show a striking difference in that in A. torresi the paired actines of these spicules are very often much longer than the unpaired actines, whereas those of the new species are almost equal in length. Also, the unpaired actines of the new species are only half the length of those of A. torresi (up to 342 x 12 against 690 x 24 µm in A. torresi ), and the paired actines only a third in length (up to 222 x 10 vs. up to 900 x 23 µm in A. torresi ).

Genus Uteopsis Dendy & Row, 1913

Figures

FIGURE 53. Anamixilla singaporensis sp. nov., holotype RMNH 9350 from Singapore, a, habitus in situ at 6 m depth (scale bar = 1 cm, photo N.J. de Voogd), b, histological cross section showing syconoid aquiferous system and inarticulate skeleton of giant triactines (scale bar = 500 µm); upper part: cortical skeleton of giant and intermediate-sized triactines, lower part: atrial skeleton of tetractines, c, tangential view of atrial surface (scale bar = 200 µm), showing atrial tetractines and subatrial triactines.

FIGURE 54. Anamixilla singaporensis sp. nov., holotype RMNH 9350, SEM images of spicules, a, cortical and choanosomal equiangular equiactinal triactines, b, subatrial sagittal triactine, c, atrial sagittal tetractine, d, trichoxea.