Cyamon aruense Hentschel, 1912

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 : 21

Cyamon aruense Hentschel, 1912 Figs 9 A–E

Cyamon aruense Hentschel 1912; 374, pl. 20 fig. 33 (Aru Islands, Indonesia); Hooper 1991: 1305, figs 63f-i.

Material examined.

Fragment of holotypeSMF 1618, preserved in alcohol, Indonesia, Aru Islands, Straits of Dobo, 6°S, 134.8333°E, 40 m, coll. H. Merton, 20 –03– 1908.

Description.

The holotype is an encrusting sponge of 6 cm long and 3 cm wide growing over a haplosclerid sponge (Hentschel, 1912). The fragment of less than 0.5 × 0.5 cm and 1 mm in thickness (see Fig. 9A) examined by us was mixed with the haplosclerid in such a way that the microscopic slides were thoroughly contaminated with it. We have to rely on Hentschel’s remarks about shape and surface characters. The surface is hispid due to the long styles protruding from the sponge, which was grey coloured in alcohol, but shows a pale brownish colour in our fragment. Consistency not mentioned by Hentschel, but crumbly describes it best.

Skeleton: the usual basal mass of polyactinal spicules upon which relatively long styles are erected surrounded in the periphery by bundles of thin centrotylote styles. Thick short styles are singly erect on the substrate, buried in the basal mass of polyactines.

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

Long thin styles (Figs 9B, B1), relatively rare, smooth, almost always broken in the slides so we cannot show a complete SEM image of them, heads smooth and not distinguished in width from the shaft, the other end gradually pointed. Longest style approximately 1620 × 16 µm, whereas Hentschel mentioned 1760 × 9-12 µm. Hentschel suggested a faint tyle, but we did not observe this.

Centrotylote thin styles (Fig. 9C, C1), smooth, curved, with a tyle near the middle of the spicule, but not exactly in the middle, the most common spicule of the monaxone spicule complement, 302 –368.7– 426 × 1.5 –2.6– 4 µm.

Short thick styles (Fig 9D, D1), relatively rare, smooth, often curved in the upper half, slightly fusiform, with a faint tyle, 297 –389.8– 456 × 8 –13.9– 17 µm.

Polyactines (Figs 9E) with 3-5 cladi, all of which are heavily spined with relatively coarse spines, without smooth areas, basal cladi rather blunt compared to those of other species, 48 –68.9– 84 × 5 –8.1– 11 µm, lateral cladi 29 –40.6– 54 × 4 –6.7– 8 µm.

Distribution.

Only known from the Arafura Sea.

Ecology.

Deeper water on hard substrate.

Discussion.

The heavy spination of the polyactines appears to be a distinct feature of this species. Hooper’s (1991) redescription denies the occurrence in this species of centrotylote ectosomal thin styles, wheras these spicules appeared common in the fragment of the holotype examined by us. These spicules are comparable to those of Cyamon arguinense sp. n., rather than to those of Cyamon vickersii because they do not have the characteristic crooked shape and also are not rugose at the pointed end. The polyactines of this species appear somewhat similar to those of Cyamon quadriradiatum as described and drawn by Carter (1880). However, details and sizes of the other spicules differ between the two: long styles are much longer and thinner in Cyamon aruense and there is apparently no further category of short thick styles in Cyamon quadriradiatum . Since both are ill known, we must have more data and further specimens to establish these species as distinct.