Hymedesmia 2009

Goodwin, Claire E. & Picton, Bernard E., 2009, Demosponges of the genus Hymedesmia (Poecilosclerida: Hymedesmidae) from Rathlin Island, Northern Ireland, with a description of six new species, Zoological Journal of the Linnean Society 156 (4), pp. 896-912 : 906-907

HYMEDESMIA (STYLOPUS) CRAMI SP. NOV.

( FIG. 9A, B )

Type material: Holotype: specimen in IMS, section and spicule preparation from tissue sample ( Rathlin Island Sponge Biodiversity Project ; White Cliffs, 55°17.542 ′ N, 06°14.507 ′ W; water depth, 30–33 m; Mc 2653). Collected by B. Picton and A.M. Mahon, 7 July 2005.

Etymology: Named for the cream colour of the surface, from the Latin crami for cream.

Comparative material examined: Hymedemsia dermata Lundbeck, 1910 , spicule preparation of specimen from Forsblads Fjord in East Greenland (Amdrup expedition 1900). ZMUC.

External appearance: Thin, cream incrustation on boulder, with a maximum diameter of 5 cm. There are no obvious pore sieves, and the surface appears slightly hispid and is covered in a thin layer of silt.

Skeleton: Basal layer of acanthostyles, sparsely distributed, with a roughly even ratio of large to small acanthostyles. There are ascending columns of ectosomal spicules that are 10–15 spicules thick, which fan out towards the surface, and may adjoin with adjacent columns. The sponge is 900–1000-Mm thick.

Spicules:

1. Large acanthostyles: 370–550 Mm (436 Mm) by 12–18 Mm. Head, very slightly tylote; shaft, mainly smooth, with the bottom eighth to one-quarter covered in very small spines, giving it a roughened appearance. The spines on the head may be rounded at the tip.

2. Small acanthostyles: 105–175 Mm (136 Mm) by 12–14 Mm; the head is not tylote, and is entirely spined with recurved spines, the size of which vary between individual spicules (small–large). In some individuals the spines on the head are larger, and may have rounded tips.

3. Ectosomal spicules: 290–400 Mm (360 Mm) by 4–7 Mm. These are strongyles in which usually one or both ends are tylote.

4. Microscleres: absent. One arcuate chela was present in the spicule preparation, but is assumed to be contamination, as chelae are not present in the tissue section.

Remarks: Hymedemsia dermata has similar spicule sizes. However, it is described as having concical papillae on the surface, and the large acanthostyles are strongly spined, as opposed to the roughened texture of the acanthostyles described above. The strongyles are also thicker (6–10 Mm), and may be polytylote.

Figures

Figure 9. A, Hymedesmia (Stylopus) crami sp. nov. A, large acanthostyle; B, base of large acanthostyle; C, small acanthostyle; D, ends of ectosomal spicule. Scale bars: 10 Mm. B, Hymedesmia (Stylopus) crami sp. nov., surface.