Sowerby, 1806
Species Overview
Spongionella pulchella Sowerby, 1806 is a thickly lamellate to cushion-shaped, yellowish brown or green, soft sponge with a finely conulose surface. It is very elastic-spongy. It has no spicules; in stead it has a regular lattice-work of spongin fibres. It is predominantly a deep water species with a somewhat disjunct distribution in the Northern Atlantic and Mediterranean-Azores.
Taxonomic Description
Colour: Yellow, greenish-grey, light buff, brown. Brownish when dried or preserved.
Shape, size, surface and consistency: Usually upright, occasionally branching, but normally a thick lamella as though branches have been webbed together. There is often a small stalked base attached to the rock. Also reported as small cushions. There is a clear, easily detachable, dermal membrane. Surface is regularly conulate, corresponding to the ends of tbe skeletal fibres. Oscules are 0.5-1.5 mm in diameter, set in slight depressions. A few are scattered across the surface, with a closely spaced series of oscules at the outer edge of laminar specimens. Consistency elastic, soft to fairly tough.
Spicules: None. Spongin fibre skeleton.
Skeleton: (Spongionella pulchella skel) A regular lattice of spongin fibres. Thin primary fibres radiate from the base towards the distal margins: 20-30 µm. The secondary fibres lie approximately perpendicular to the primaries: ca. 7-20 µm. Primaries are separated by ca. 200-350 µm. The fibres do not enclose foreign bodies such as sand or broken spicules. The fibres are stratified and the primaries possess a distinct 'pith'.
Ecology: Usually on rock in deeper water and moderate to strong tidal streams, down to 200 m. Also reported at the base of Posidonia (Mediterranean). Rather scarce.
Distribution: North Atlantic (Greenland, Norway, Sweden, Shetland, Ireland, Azores); Mediterranean. Recently recorded from the Northern Irish coast (North Channel) and the Sound of Mull. It is not reported from intermediate well-investigated localities along the south and west coasts of Britain and France.
Etymology: Pulchellus (Latin) = small and beautiful.
Type specimen information: Unregistered slide in Bowerbank's Collection. MCS Voucher BELUM Mc1471, Rathlin Island, N Ireland.
Remarks
The form is somewhat reminiscent of some specimens of Axinella dissimilis with coalescent branches, or possibly Haliclona oculata . However, it is easily distinguished from these by its colour, elasticity and oscules, combining to give a distinctive "giz". In section, the lattice of spongin with no spicules is immediately diagnostic.
In the Mediterranean a second species of Spongionella is found, viz. S . gracilis (Vosmaer, 1886), which has been synonymized in the past. It forms groups of distinct tubes, dissimilar to the growth form of pulchella (cf. Pulitzer-Finali and Pronzato, 1976).
Source: Ackers et al., 1992 (B.E. Picton, D. Moss)