Dercitus Stoeba senegalensis, 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 : 19-22

Dercitus Stoeba senegalensis sp. n. Figs 8 A–C9A–D

Dercitus plicatus ; Lévi 1952: 42, fig. 5; Van Soest 1993: Table 2, pars (not: Dercitus plicatus sensu Schmidt 1868).

Material examined.

Holotype ZMA Por. 21530, off the coast of Senegal, coll. F.P. Vermeulen, 1906, fish trawl.

Paratype ZMA 06721, Mauritania, off Banc d’Arguin, 19.0667°N; 16.4167°W, dredged at 12-18 m, coll. R.W.M. Van Soest, R.V. ’Tyro’ Mauritania II Expedition stat. 049, 11 June 1988.

Additional (non-type) material ZMA Por. 21697, Aegean Sea, fragment of specimen nr. 101 of E. Voultsiadou’s collections.

Description

(Figs 8A, 9A). Sponge encrusting and agglutinating calcareous fragments, colour dirty white. Lateral size approx. 5 × 3 cm. The holotype now consist of three fragmented pieces, the paratype is 1.5 × 1.5 cm. Consistency crumbly.

Skeleton: a confused mass of calthrops with a crust of microscleres at the surface.

Spicules: calthrops (no dichocalthrops) and sanidasters.

Calthrops (Figs 8B, 9 B–C), often with bifid or bluntly rounded cladi, occasionally five-claded, in a wide size range but upper size relatively large, cladi length and thickness 92 –299.8– 426 × 8 –38.6– 55 µm (in holotype) and 36 –224.9– 480 × 6 –28.6– 60 µm, cladomes 126 –462.6– 618 µm (holotype) and 61 –300.4– 810 µm (paratype).

Sanidasters (Figs 8C, 9D), relatively uniform in size and spination, relatively small: 11 –12.6– 17 µm (holotype) and 12 –17.3– 21 µm (paratype).

Etymology.

Named after the locality of the holotype.

Habitat.

Consolidating coarse limestone fragments on rubble bottoms.

Distribution.

Senegal, Mauritania, possibly (Eastern) Mediterranean.

Remarks.

The new species was formerly identified as Dercitus (Stoeba) plicatus , but it differs clearly by the much larger upper size of the calthrops and the apparent absence of dichocalthrops. There are some discrepancies between the two type specimens in the average size and thickness of the spicules, but in view of the generally large size variation this is considered intraspecific variation. It is likely that Lévi’s Senegal record of Dercitus plicatus also fits with this species, as it was similarly white coloured, and also lacked dichocalthrops. The size of the cladi of the calthrops were given as maximum 250 × 30 µm which is clearly larger than in Mediterranean Dercitus plicatus and within the range of our new species.

The ZMA collection contains a tiny fragment of a specimen from the Aegean Sea donated by E. Voultsiadou (ZMA 21697) which has calthrops (Fig. 9E) with cladi up to 295 × 48 µm (cladomes up to 475 µm), and which lacked dichocalthrops. Sanidasters similar in size and shape to those of Dercitus (Stoeba) senegalensis sp. n., especially to the paratype. Apart from the wide geographic separation, this fits with our new species.

The record of Pansini (1987) of Dercitus plicatus from the Alboran Sea possibly also belongs to this species as it was noted to lack dichotriaenes. However, since no further data were provided this remains undecided.