Dercitus Stoeba berau, Van Soest, Rob W. M., Beglinger, Elly J. & De Voogd, Nicole J., 2010

Van Soest, Rob W. M., Beglinger, Elly J. & De Voogd, Nicole J., 2010, Skeletons in confusion: a review of astrophorid sponges with (dicho-) calthrops as structural megascleres (Porifera, Demospongiae, Astrophorida), ZooKeys 68, pp. 1-88 : 33-35

Dercitus Stoeba berau sp. n. Figs 15 A–B16A–D

Material examined.

Holotype RMNH 4256, Indonesia, Kalimantan, Berau region, Derawan Islands, depth 10 m, coll. N.J. De Voogd, field nr. BER105/140808/055, SCUBA, 14 August 2008.

Description.

Blackish grey lobate mass (Fig. 15A), approx. 20 ×15× 10 cm in size, surface in places speckled white by?coral sand and at the base the specimen is encrusted by a bluish sponge ( Haliclona ). Oscules prominent on the summit of lobes, approx. 0.5 cm in diameter. Consistency firm, compressible. The preserved specimen is broken into two similar sized masses (Figs 15B, 16A). The black colour is maintained in alcohol and has strongly darkened the fluid and the labels.

Skeleton: difficult to study in the preserved condition due to the intense black colour, but structure is dense and unorganized, with a dense cover of microscleres at the surface.

Spicules: calthrops, sanidasters and compressed spheraster-like microscleres (pseudasters); a few oxeas are present, but these belong to the encrusting Haliclona .

Calthrops (Fig. 16B), generally regular in shape and cladi number, occasionally three-claded or five-claded; size highly variable, cladi 25 –151.4– 280 × 5 –17.2– 35 µm.

Sanidasters (Fig. 16C) of extreme variability in shape, long thin with short spines, thicker with prominent stubby spines and squat warty ones, with many intermediates; size 19 –29.1– 42 × 1 –5.1– 10 (spines 0.5 –2.2– 4.5 µm).

Compressed sanidasters (pseudasters) (Fig. 16D), globular or oval with very short rays (usually less than 0.5 µm), diameter 8 –11.4– 15 µm.

Etymology.

Named after the Berau region, East Kalimantan.

Habitat.

Shallow open reef localities.

Distribution.

So far known only from the type locality E of Kalimantan.

Remarks.

Despite the long distance between the locality of Dercitus (Halinastra) exostoticus (Red Sea) and the present locality, there are compelling similarities in shape, colour and spicule sizes between the new species and exostoticus. The major difference between the two is the length and robustness of the sanidasters (up to 42 µm in Dercitus (Halinastra) berau sp. n. against max. 27.5 µm in Dercitus (Halinastra) exostoticus ). We also believe that the habit and the choanosome pigmentation will prove to be distinct in the two, but the absence of observations of living Dercitus (Halinastra) exostoticus precludes definite conclusions.

Dercitus (Halinastra) berau sp. n. differs from Dercitus (Halinastra) japonensis sp. n. (see below) in the more robust condition of the sanidasters, the more oval, not completely euaster-like condition of the compressed sanidasters of the Japanese specimens. Also the length of the calthrops cladi appears less in the Dercitus (Halinastra) japonensis sp. n. See also Table 3.