(Ellis and Solander, 1786)
Species Overview
Stelligera stuposa (Ellis and Solander, 1786) is a fairly large (up to 10 cm high) yellow branching sponge with a hairy, rather slimy surface, which accumulates mud and particles, giving it a characteristic habit. It may be confused with Raspailia hispida , but this is less slimy and it has no larger particles sticking to its surface. For certainty microscopic examination is necessary. It is a common species in shallow and somewhat deeper sublittoral localities along the west and south coasts of Britain and France.
Taxonomic Description
Colour: Yellow, orange, red-brown.
Shape, size, surface and consistency: (Stelligera stuposa MCS2) Branching-erect, branches often flattened in cross section; rarely fused. The branching is dichotomous or, more frequently, polytomous, usually more or less in one plane. Stalked; up to 10 cm or more high. Surface villose, hairs of uneven length. The hairs trap particulate matter; the particles are easily seen with the unaided eye. Small oscules in groups near the tips of branches. The position of these oscules may help identification underwater. Not visible in preserved material. Exudes quantities of slime when taken out of the water. Consistency moderately firm, but with a soft outer layer which is easily rubbed off. Elastic.
Spicules: (Stelligera stuposa spics) (Stelligera stuposa spics V) Megascleres of the axial core are styles of 900-2000 µm, occasionally strongyles of 630-880 µm. Those of the extra-axial skeleton are long styles similar in size to those of the axial skeleton, and the divergent brushes consist of slender oxeas or anisoxeas of 520-690 µm.
The microscleres are euasters, ca.14 µm in diameter.
Skeleton: Plumose. An axial skeleton of longitudinally oriented megascleres forms a stiff core along the centre of each branch. A softer, extra-axial, skeleton of long megascleres (often single) radiates at right angles away from the core and penetrates the surface. Slender megascleres are scattered through the internal skeleton and also form divergent brushes around spicules projecting through the surface. Microscleres form a layer at the surface. Minimal amounts of spongin are present.
Associations: Nematode worns often live in the outer silt-covered layers of the sponge.
Ecology: On rocks and stones and in rock crevices. Not found in harbours. A common species in the circalittoral, from 4 to 110 m.
Distribution: Britain, France, Spain, Mediterranean.
Etymology: Stuposa = Latin for soft rope made from flax or hemp, referring to the relatively soft branches.
Type specimen information: Type from Hastings (SE England) probably lost. MCS voucher BELUM Mc814, Strangford Lough, N Ireland.
Remarks
Descatoire, (1969b: 18) considers S . stuposa and S . rigida two forms of the same species.
The sponge is described by Ellis and Solander (1786) as Spongia stuposa , the "Tow Sponge": "Spongia ramosa teres stuposa atque villosa" = "sponge with round branches, soft like tow, and covered with fine pointed hairs". In the remarks it is said that the "little sponge is of a pale yellow color, and about three inches high." It was found thrown on the shore at Hastings. In this text reference is made to an earlier record by Ellis (1766) of the "Downy branched English sponge".
Production of slime in a hairy, branched sponge whose branches are somewhat flattened in cross section is probably indicative of Stelligera stuposa . To be certain a microscopic check is essential. The species with which Stelligera stuposa is most frequently confused is Raspailia hispida , especially in the size range up to 15 cm. Raspailia hispida and Stelligera stuposa may be separated by eye underwater using the information in the table below. Presence or absence of slime may prove to be the only reliable field character for separating these two species. Unless one is familiar with a local population, and maybe even then, it is necessary to check the spiculation to be certain of identification.
Other yellow, branched sponges with which it can be confused, especially underwater, are:
Axinella dissimilis : Surface, stellate, grooves converge on the oscules (only easily visible out of the water). Altogether a much larger and fleshier sponge than Stelligera stuposa .
Haliclona oculata : Not hairy, with neat oscules arranged serially along the edge of the branches.
Endectyon spp.: Smaller, more delicate looking, with a brighter, yellow or red-brown colour.
Comparison of characters of S . stuposa and R . hispida : S. stuposa & R. hispida.
Source: Ackers et al., 1992 (S.M. Stone, B.E. Picton, D. Moss).