Cyamon quinqueradiatum (Carter, 1880)

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 : 26-27

Cyamon quinqueradiatum (Carter, 1880) Figs 14 A–D, 14E (right)

Microciona quinqueradiata Carter 1880: 43, pl. IV fig. 5a-e (Gulf of Manaar, India).

Cyamon quinqueradiatum ; Dendy 1905: 178 (Gulf of Manaar, Sri Lanka).

Material examined.

Seven slides from the collections of the Natural History Museum, BMNH 1954.2.23.8, made of Dendy’s (1905) topotypical material.

Carter’s specimen from the Gulf of Manaar is apparently lost from the collections of the National Museums Liverpool (Dr Ian Wallace, in litteris), no original slides have been found in the Natural History Museum (Ms Emma Sherlock, in litteris).

Description.

(Partly from Carter, 1880 and Dendy, 1905). Thinly encrusting, hispid, yellowish brown (alcohol) to cream color (dry). Dendy’s specimen was 1.1 cm in lateral expansion, 3 mm thick. Texture soft.

Skeleton (Figs 14 A–C): bundles of subtylostyles and styles standing erect on the substratum, in the basal layer supported by polyactine spicules.

Spicules: predominant spicules are longer and shorter subtylostyles with a minority of thin styles and polyactines.

Subtylostyles, presumably a mixture of undifferentiated long thin styles and short thick styles, with prominent heads, usually lightly and gradually curved, in a large size range, which makes determining an average size meaningless: 129-1989 × 3-33 µm.

Thin styles, tapering gradually to thinly pointed curved ends, size range limited, 492-698 × 3-5 µm. Dendy believed these spicules to be growth stages of the subtylostyles, but we regard them, like Carter, as a separate spicule category.

Polyactines [Figs 14D, 14E(right)], predominantly five-claded (a few four-claded forms were observed), with the basal cladus relatively finely spined, the lateral cladi smooth, with mucronate, occasionally bifid ends, basal cladi 45 –62.8– 93 × 4 –5.9– 11 µm, lateral cladi 31 –38.4– 51 × 3 –4.8– 7 µm.

Distribution.

Only known from the Gulf of Manaar.

Ecology.

Deep water (not specified).

Discussion.

As pointed out above, Mauritanian Cyamon arguinense sp. n. shares many features with Indian Ocean Cyamon quinqueradiatum , including the smooth lateral cladi and the lack of differentiation of the long thin and short thick styles. Although the Cyamon nature of this species has never been challenged, it is nevertheless obvious from the original description and drawing by Carter (1880) and the subsequent record of Dendy (1905) that the polyactines of this species have only their basal cladi spined, an alleged prominent and discriminating feature of the genus Trikentrion . We have confirmed single cladus spination by examining a series of slides of Dendy’s material. The structure of the skeleton with longer and shorter styles originating from a basal mass of polyactines is characteristic for Cyamon . This indicates that emphasis on a single spined cladus versus all cladi spined as a difference between Cyamon and Trikentrion is wrong. See further discussion below. Among the species of Cyamon the present species also stands out by the extreme length variation of the structural subtylostyles, assuming these are homologous with the 'short thick styles’ of many other Cyamon species, and perhaps related to it, the absence of a category of long thin styles. The thin styles observed above are assumed by their size to be homologous to the peripheral short thin styles surrounding the long thin styles in other species.