Dercitus Stoeba occultus Hentschel, 1909

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 : 25

Dercitus Stoeba occultus Hentschel, 1909

Dercitus occultus Hentschel 1909: 352, text-fig. 1.

Material examined.

None. The type material collected by Michaelsen & Hartmeyer from Shark Bay, West Australia could not be found in ZMB (listed as a slide ZMB 4492 in Hooper and Wiedenmayer, 1994: 324).

Description

(from Hentschel, 1909). Endolithic within corals, filling tubular cavities of 1-2 mm diameter which connect to the outside in only a few places. Colour (in alcohol) a deep brown. The skeleton consists of dichocalthrops and sanidasters.

Dichocalthrops relatively small, protocladi 20-28 µm, deuterocladi 50-92 µm, rhabd 86-105 × 12-18 µm (computed cladome diameter 130-230 µm).

Sanidasters 13-21 × 1.5 µm. Spines are described as strongly developed and irregular, but only tiny drawings of these spicules are provided, which only show elongated rhabd shapes.

Habitat.

An endolithic species from shallow coral reefs (0.5-3.5 m).

Distribution.

West Australia, Shark Bay, shallow water.

Remark.

In spicule size this species appears close to Dercitus (Halinastra) sibogae sp. n. (see below), but that species has both ‘normal’ and compressed sanidasters, and it is epilithic. Details of the cladi lengths of the megascleres are also different.

The only other species of Dercitus (Stoeba) from Australian waters, Dercitus (Stoeba) xanthus Sutcliffe et al. 2010, differs sharply from the present species in the absence of dichocalthrops, in stead of which there are exclusively three-claded calthrops megascleres.