Form: Branching-erect, the branch diameter variable in thickness (averaging about 1cm), maintaining the same thickness almost to the tip. More or less circular in cross-section, sometimes a little flattened. Branching is typically irregular, in all planes; branches rarely fuse. Stalked.
Colour: Dark brown. This sponge gives a greenish sheen to alcohol and may stain the label purple. The dark brown colour of the tissue is still evident after sectioning and clearing.
Consistency: Firm, elastic. The soft layer is easily rubbed from the strong axial core (?).
Surface: Bristly (villose) with hairs of uniform length (?) which trap particles of silt. Ragged remnants of membrane may be seen clinging to the surface.
Apertures: Oscules are apparent in the field on close inspection, scattered on the branches and often sub-terminal. They are obvious as dark spots in photo 33, but lost on preservation.
Skeleton: Plumoreticulate, with a dense axial condensation of reticulating spongin fibres, which are cored by subtylostyles and echinated by acanthostyles. There is a soft, extra-axial skeleton of long spicules radiating out at right angles from the core to pierce the surface. Divergent brushes of slender spicules surround the projecting spicules at the surface. The spongin becomes more abundant as the animal ages.
Spicules: Megascleres of axial and extra axial skeletons are subtylostyles (a) 900-(1115)-1325Ám "to 1600Ám". The echinating spicules are acanthostyles (c) 90-(110)-125Ám), best seen in longitudinal sections (these spicules are always frequent or common in this species, cf. Raspailia hispida). The divergent brushes consist of styloids (b) to ca. 350Ám.
Habitat: Common on sublittoral rock and boulders from moderately exposed sites to sheltered sites with some tidal current. Tolerates some silt. The only Raspailia spp. so far known from harbours (?). Co-exists with Raspailia hispida and other Axinellids in open water.
Distribution: Recently known from Cornwall; Lundy ; Anglesey; Strangford Lough; Mull; W. coast of Ireland; Roscoff; Sussex; Channel Isles. Common on western coasts of the British Isles. Not found in the North Sea.
Distribution Map from NBN: Grid map (fast) : Interactive map (slower, requires login to view records) : National Biodiversity Network mapping facility, data for UK.
Identity: This is the only dark brown, branched, bristly sponge which is common, but beware other rarer Raspailia species whose live appearance is currently unknown. The presence of the typical acanthostyles will confirm Raspailia spp. and their shape and size are diagnostic for Raspailia ramosa. (Other branching - erect Raspailiids, which may be valid species, include; Raspailia pumila, Raspailia rectangulus, Raspailia radiosus, Raspailia viminalis, etc. Raspailia virgultosa occurs in the North Sea and has much larger acanthostyles.)
Voucher: BELUM : Mc101. Portrush, Co Antrim.
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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