Cyamon argon Dickinson, 1945

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 : 23-26

Cyamon argon Dickinson, 1945 Figs 12 A–C, Figs 13 A–G

Cyamon argon Dickinson 1945: 15, pl. 19 Figs 37-38 (Mexican Pacific).

Material examined.

Holotype of Cyamon argon , AHF-NHMLA L35535, D34, preserved in alcohol, Mexico, Cedros Island, South Bay, Hancock Pacific Exp editions, Velero Station 287-34, 28.09°N, 115.3°W, 18-27 m, among kelp, 10 March 1934.

Description.

Shape upright, bilobed thick branches (Fig. 12A), spreading out upwards, with longitudinal grooves and covered in rounded spiny projections and conules. Height and diameter 3.5 cm, stalk approximately 1.5 cm. Colour (preserved) red-brown. Consistency tough, barely incompressible.

Skeleton: axial-columnar, with surface projections formed by the outwardly directed columns (Fig. 12B) branching off from the axial region. Columns have a core of short thick styles and polyactines crowned at the surface by long thin styles accompanied by (rare) short thin centrotylote styles.

Spicules: long thin styles, short thin styles, short thick styles, polyactines.

Long thin styles (Fig. 13A), mostly broken in the slides, one complete one measured 960 × 15 µm.

Short thin centrotylote (Figs 13C, C1, C2), wavy to somewhat crooked, with one end rounded and the other mucronate-spined, 210 –250.6– 348 × 3 –3.6– 4 µm.

Short thick styles (Figs 13B, B1), smooth curved evenly, 350 –480.5– 593 × 15 –32.3– 42 µm.

Polyactines (Figs 12C, 13D-E) two-, three-, four- and five-claded, quite variable in shape and size. T-shaped spicules (Fig. 13D) similar to those found in Trikentrion are common. Basal cladi usually prominently spined (Fig. 13D1), lateral cladi finely spined (Fig. 13D2). No entirely smooth spicules were observed. Diactinal spicules (Fig. 13E) with swollen excentrical swellings and spined apices, often sharply angulated. Three-claded spicules with basal cladi 45 –60.7– 78 × 6 –14.9– 22 µm, lateral cladi 30 –110.7– 162 × 5 –17.0– 21 µm. Four-claded spicules have basal cladi 33 –44.8– 51 × 9 –14.9– 21 µm, lateral cladi 63 –86.2– 123 × 7-18 µm. Diactinal spicules: 204 –245.1– 312 × 18 –22.8– 31 µm.

Distribution.

Pacific coast of North Mexico.

Ecology.

In kelp forest, 18-27 m.

Discussion.

As pointed out above, this species is close to Cyamon neon , and if more data on variation would become available, it is possible, in view of the nearness of both type localities that the two might be part of a single variable species. The following characteristics are similar between the two: long thin styles of 1000+ µm in length, the possession of short thin centrotylote styles with spined pointed apex (shared with Cyamon vickersii ), smooth evenly curved short thick styles of 400-500 µm in length, polyactines consisting predominantly of three-claded polyactines with all cladi smooth except for the apices, short basal cladus compared to long lateral cladi, and the frequent occurrence of diactinal polyactines. However, there are also clear differences, which presently preclude synonymization of the two: shape bush-like in Cyamon argon , massively encrusting in Cyamon neon , thickness of short thick styles in Cyamon argon twice that of Cyamon neon , basal cladi of the polyactines distinctly spined in Cyamon argon whereas these are only rugose or even smooth in Cyamon neon , and finally the size (length but also thickness) of the lateral cladi in three-claded polyactines which are usually well over 200 µm long and 20 µm thick in Cyamon argon , whereas those of Cyamon neon are on average around 150 × 10 µm.

With Cyamon vickersii , this species shares a more elaborate, upright growth form, which is otherwise rare in the genus.