Cyamon (?) spinispinosum (Topsent, 1904)

Soest, Rob van, Carballo, Jose Luis & Hooper, John, 2012, Polyaxone monaxonids: revision of raspailiid sponges with polyactine megascleres (Cyamon and Trikentrion), ZooKeys 239, pp. 1-70 : 29-31

Cyamon (?) spinispinosum (Topsent, 1904) Figs 16 A–E

Hymeraphia spinispinosa Topsent 1904: 162, pl. 14 fig. 9 (Azores).

Acantheurypon spinispinosum ; Topsent 1928: 293 (Azores).

Acantheurypon incipiens Topsent 1928: 293, pl. 10 fig. 10 (Azores).

Cyamon spinispinosum ; Stephens 1921: 61 (Ireland); Van Soest et al. 2007: 130 (Rockall Bank, W of Ireland).

Material examined.

Twenty six samples in the ZMA Porifera collection, preserved in alcohol, all from Rockall Bank, approximately 55.4N, 15.8W, depth 500-900 m, collected during MOUNDFORCE 2004 and BIOSYS 2005 cruises with RV Pelagia. Type material:Monaco Oceanographic Museum, not examined.

Description.

Pale greenish encrustations (Fig. 16A) on deep-sea coral branches, surface irregularly conulose-hispid. Consistency soft. Dimensions up to 15 × 6 cm in widest expansions, thickness approximately 1 mm.

Skeleton: basal mass of polyactines, usually a single layer of spicules, with basal cladi pointing outwards and lateral cladi spread out on the substrate, taking up the position of echinating acanthostyles as in Hymedesmia or Clathria (Microciona) . Single long styles with heads embedded in the layer of polyactines, surrounded by groups of short styles.

Spicules: long styles, short styles, polyactines.

Long styles (Figs 16C, C1) with upper parts heavily spined, becoming gradually smooth toward the pointed end, only a few were found to be complete, 657 –737.2– 822 × 32 –35.5– 38 µm.

Short styles (Figs 16B, B1), very abundant, heads slightly spined, shaft smooth, faintly polytylote, pointed end tends to be slightly mucronate, 302 –324.1– 366 × 7 –8.4– 10 µm.

Polyactines (Figs 16D-E), with 3-8 cladi, usually with a long and prominent basal cladus and short irregular lateral cladi (Fig. 16E), heavily spined without smooth areas, basal cladi 90 –151.3– 234 × 9 –11.2– 14 µm, lateral cladi 15 –27.3– 36 × 6 –7.4– 12 µm.

Distribution.

Azores, Ireland, also Norway (P. Cárdenas, pers. comm.). A common North Atlantic bathyal species ( van Soest et al. 2007 report 110 specimens collected on Rockall Bank, W of Ireland).

Habitat.

Encrusting deep-sea corals at depths from 500-900 m.

Discussion.

This is a deviating Cyamon with several unique features not shared by the majority of the species. Both monaxone megascleres are partially heavily spined, and the raspailiid feature of a long thin style surrounded by short thin styles is absent. The polyactines resemble echinating acanthostyles by their long basal cladus and crown of short irregular lateral cladi. These spicules may be assumed to bridge the gap between the polyactines with more or less equal length cladi and acanthostyles with heavily knobbed and spined heads such as found in some myxilline genera ( Hymedesmia Bowerbank, 1864, Discorhabdella Dendy, 1924) and in the raspailiid genus Eurypon Gray, 1867. Additionally, it occurs in cold deep-sea habitats unlike all other Cyamon species. It is likely that this species does not belong in Cyamon , but we will await additional (molecular) evidence before removing it from the genus