(Bowerbank, 1866)
Species Overview
Pseudosuberites sulphureus (Bowerbank, 1866) is a bright, deep, sulphurous orange coloured, thinly encrusting sponge forming extensive sheets on the undersurface of intertidal boulders and on exposed rocks in the sublittoral. It is rather common on the west and south coasts of the British Isles and along the Atlantic coasts of France and Spain. It may be easily confused with Pseudosuberites mollis which has smaller and slightly differently shaped tyles (microscopic examination necessary).
Taxonomic Description
Colour: A bright, deep, sulphurous orange or bright yellow. The brightness is distinctive under water.
Shape, size, surface and consistency: Thin sheets, but can exceed 5 mm in thickness. Forms extensive irregular patches, to at least 30 cm across. Surface even, smooth, with subsurface cavities visible through the pellucid ectosome, which is readily detachable. Apertures according to Topsent 0.2 to 1 mm in diameter and flush with the surface. Not visible on collection. Consistency compact, fleshy.
Spicules: (Pseudosuberites sulphureus sp) The megascleres are tylostyles: 150-500 x 3-11.5 µm. Considerable variation in spicule size occurs in a given specimen. There is no clear division into 2 size classes as found in other Suberitid species. Most of the tylostyles are straight, but when curved the curvature occurs about a third (or less) of the way along the shaft. The shafts tend not to be parallel-sided, their widest point being about midway. The tyles vary from being smoothly rounded to sharply mucronate. There are no microscleres.
Skeleton: The ectosome consists of megascleres of varying size lying tangentially to the surface in bundles that intercross to form a network visible to the naked eye. The choanosomal skeleton is essentially halichondroid, with megascleres orientated in all directions, sometimes in bundles.
Ecology: Bedrock, boulders, shells. Possibly confined to areas of strong water movement. In tidal rapids on shore, beneath boulders. In sublittoral also on exposed vertical bedrock.
Distribution: Shetlands, SW Ireland, east coast (Scarborough) and south coast of UK, Guernsey, Roscoff.
Etymology: The name refers to the sulphur colour.
Type specimen information: The type is in the Natural History Museum, London: BMNH 1910.1.1.156 (dry), Norman Collection + 1910.1.1.1880 (slide from Type), Norman Collection. MCS voucher BELUM Mc33, Valentia Isl., SW Ireland.
Remarks
The tangentially arranged tylostyles in the ectosome are characteristic. A microscopic examination is essential to separate this yellow or orange encrusting sponge both from other species of suberitids, especially Pseudosuberites mollis , and from other taxa. It is possible that the brightness of the colour is a useful field characteristic, but more evidence is needed to confirm this.
P . mollis has smaller spicules (175-350 µm) and the head of the tylostyle is subterminal, with the end of the spicule as wide as the shaft underneath the tyle.
Source: Ackers et al., 1992.