Cyamon arguinense, Soest, Rob van, Carballo, Jose Luis & Hooper, John, 2012

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 : 15-17

Cyamon arguinense sp. n. Figs 5, 6 A–D

Material examined.

Type specimen: HolotypeZMA Por. 06723, encrusting a stone, preserved in alcohol.

Type locality: Mauritania, off Banc d’Arguin, 19.0833°N, 16.4167°W, on sandstone ridge, dredged, 12-18 m, coll. R.W.M. van Soest & J.J. Vermeulen, Mauritania II Exped. Stat. 49, 11 –06– 1988.

Description.

Thin crust, (Fig. 6A) hispid surface. Color red (alive), dirty white (alcohol). Consistency soft, easily damaged, size 2.5 × 1.5 cm × 2-3 mm.

Skeleton: columnar bundles of megascleres issuing from a basal layer of polyactines. Columns consist of a single long subtylostyle sheathed in a tight bundle of fusiform centrotylote styles; bundles separate, interconnected only near the substratum.

Spicules of three types: subtylostyles (assumed to be homologues of the long thin styles), centrotylote styles (assumed homologues of the short thin styles), polyactines (short thick styles apparently lacking).

Long thin (subtylo-)styles (Fig. 6B, B1) with prominent heads, and bluntly rounded pointed ends, 1229 –1482.1– 1668 × 12 –13.9– 18 µm.

Short thin styles, fusiform, centrotylote (Fig. 6C, C1), tyle slightly excentric, rounded end tapering, 244 –521.5– 719 × 2.5 –6.4– 9 µm.

Polyactines, (Fig. 6D) predominantly four-claded, (a few five-claded forms were observed), basal cladus with coarse recurved spines, lateral cladi entirely smooth, basal cladus 51 –58.6– 69 × 5 –6.5– 8, lateral cladi 31 –55.7– 78 × 4 –6.1– 8 µm.

Etymology.

The name is an adjective referring to the type locality: the Mauritanian nature reserve Banc d’Arguin, one of the richest faunal areas of the west coasts of Africa (cf. Wolff et al. 1993).

Distribution

(Fig. 5). So far known only from the sandstone ridges of coastal flats of the Banc d’ Arguin, Mauritania, West Africa.

Ecology.

In shallow-water (12-18 m), highly sedimented environments, in the company of many other sand dwelling sponges such as Ciocalypta and Polymastia (cf. Van Soest 1993: Pl. I fig. a).

Discussion.

The single spined cladus of the polyactine spicules is an alleged feature of the genus Trikentrion , but in all other characters (growth form, monaxone spicules and skeletal arrangement) this is a typical Cyamon . It reminds strongly of Indian Ocean Cyamon quinqueradiatum , with which it shares the shape and up per length of the subtylostyles, the lack of differentiated long and short thick styles, and the size and single cladus spination of the polyactines. Differences are the predominantly five-claded polyactines and the shape and size of the stylote spicules in Cyamon quinqueradiatum . Long subtylostyles with prominent heads are shared with Indian Ocean Cyamon quadriradiatum but that species has all the cladi of the polyactines densely spined.

The new species was collected in the same dredge sample as Cyamon amphipolyactinum sp. n. (see above), but on a different sandstone flake (these provide hard substratum for sponges that would otherwise be buried in the sand). The two species differ sharply in the shape, size and ornamentation of the polyactines as well as in the shape and size of the styles.