Form: 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.

Colour: Yellow, orange, red-brown.

Smell: None. Slime : 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."

Surface: Villose, hairs of uneven length (cf. Raspailia hispida). The hairs trap particulate matter; the particles are easily seen with the unaided eye.

Apertures:

• Small oscules in groups near the tips of branches. The position of these oscules may help identification underwater. Not visible in dead material.

Contraction:

• Not noticeable.

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Synonyms: Dictyocylindrus stuposus (Ellis & Solander, 1786:186) Bowerbank, 1866:116, Vibulinus stuposus (Ellis & Solander, 1786:186) Gray 1867:545.

Internal characters

Skeleton: Plumose. An axial skeleton of longitudinally orientated 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.

Spicules: Megascleres of the axial core are styles (a), occasionally strongyles (b). Those of the extra-axial skeleton are long styles (c), and the divergent brushes consist of slender oxea or anisoxea (d). The microscleres are euasters (e) (ca. 14 μm diameter). Styles 900-(910)-1000 μm "to 2000 μm" in length, strongyles 630-(760)-880 μm, oxea 520-(610)-690 μm.

Identity: 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 (q.v. and table below), 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 following table. The characters used to separate the two species need to be checked to see it they are reliable. Guide users are asked to report their experience of using the table, so that unreliable characters can be discarded in future editions of the Guide. Other yellow, branched sponges with which it can be confused, especially underwater, are as follows: Axinella dissimilis (q.v.). 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 (q.v.). Not hairy, with neat oscules arranged serially along the edges of the branches. Endectyon spp. (q.v.). Smaller, more delicate looking, with a brighter, yellow or red-brown, colour. 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. It is surprising how often one can be caught out by these two species!

Distribution Map from NBN: Stelligera stuposa at National Biodiversity Network mapping facility, data for UK.

iNaturalist: Stelligera stuposa at iNaturalist World Species Observations database.

WoRMS: Stelligera stuposa at World Register of Marine Species. Accepted name: Stelligera stuposa (Ellis & Solander, 1786). AphiaID: 134175.

Classification: Biota; Animalia; Porifera; Demospongiae; Heteroscleromorpha; Axinellida; Stelligeridae; Stelligera

Voucher: BELUM : Mc814. Strangford Lough, Down.

Editors: D. Moss, B.E. Picton.