Form: Variable, depending on microhabitat, but typically from spreading cushions with mamillate oscular chimneys, to massive lobose forms with tall, rugose, volcano-like oscular chimneys. These oscular chimneys tend to be arranged in irregular rows in cushion forms. The rows can become ill-defined ridges, caused by the oscular chimneys anastomosing for up to 3/4 of their height. In large forms the oscular projections can be mammiform, or chimneys, which become bulbous for the first 2/3 of their height, narrowing more sharply in the upper 1/3. The oscular rows may appear as tassels, or as repent branches (see van Soest, 1980, p.9). More information is required on growth forms, and their relationships with habitat types. Specimens may be large, with a spread of up to 30cm, and height to 5cm.
Colour: Typically purple, but can verge to pink or brown in some specimens. The colour is normally deeper on the higher portions of the sponge (i.e. oscular chimneys), becoming a washed-out fawn/grey away from the extremities. The depth of colour probably reduces
Smell: None. Slime : May be present in considerable amounts, especially when crushed or torn apart.
Consistency: Firm, compressible, friable.
Surface: Smooth and punctate (from the inhalant pores). Large specimens become rugose, caused by irregular tuberculate projections of variable size and position, giving a distinctive warty appearance. The projections can form surface ridges, giving the sponge an 'angular' appearance. Some specimens display an initially moderate friction, but quickly become slimy as pressure is applied.
Apertures: The oscules are formed on chimneys, as described under 'Form'. The openings are large, up to 1cm in diameter, and remain open after collection and preservation. Inhalant pores show through the surface, and are closely packed and conspicuous.
Skeleton: Primary tracts are 3 to 6 spicules in diameter, with single inter-connecting spicules which are not differentiated into secondary tracts. There is no ectosomal skeleton. Spongin is scarce, nodal.
Spicules: Oxea, typically slightly curved, but varying from straight to fairly abruptly bent in the middle. 140 - 160 x 4.5 - 7Ám. Larger oxea (up to 170Ám?) are rare. Oxea in the range 95-140 x1-5.5Ám are occasionally found.
Habitat: This sponge is typically found from the upper circalittoral downwards, but less well developed specimens occur in shallower water and on the shore. It mainly occurs on vertical rock faces, in silt free areas of considerable water movement, e.g. gullies and/or areas exposed to wave action and tidal currents.
Distribution: Recently known from W. coast of Ireland; Northern Ireland (Antrim; Strangford Lough); W. coast of Scotland (Mull; Coll; Tiree; Oban; Lewis); S.W. Britain (Salcombe, Devon, Eddystone, Hard Deeps; Scilly Isles; Lundy).
Distribution Map: NBN map : National Biodiversity Network mapping facility, data for UK.
Identity: The purplish colour, giant volcano-like oscules, rugose appearance and slime are characteristic. Less well developed specimens could be confused with other Chalinids. This description is compiled largely from 11 specimens in the collection of G. Ackers. Other specimens may differ slightly in detail.
Voucher: BELUM : Mc800. Strangford Lough, Down.
Editors: D. Moss, B.E. Picton.
|Picton, B.E., Morrow, C.C. & van Soest, R.W.B., 2011. [In] Sponges of Britain and Ireland |
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