Form: 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.
Colour: Yellow, greenish-grey, light buff, brown. Brownish when dried or in formalin.
Consistency: Elastic, soft to fairly tough.
Surface: There is a clear, easily detachable, dermal membrane. Surface is regularly conulate, corresponding to the ends of the skeletal fibres.
Apertures: Oscules are 0.5-1.5mm in diameter, set in slight depressions. A few are scattered across the surface, with a closely spaced series of oscules atthe outer edge of laminar specimens.
Skeleton: There are no spicules, but a regular lattice of spongin fibres. Thin (20-30Ám) primary fibres radiate from the base towards the distal margins. The secondary fibres (ca. 7-20Ám) lie approximately perpendicular to the primaries. Primaries are separated by ca. 200-350Ám. The fibres do not enclose foreign bodies such as sand or 'stray' spicules. The fibres are stratified and the primaries possess a distinct 'pith'.
Spicules: None. Spongin fibre skeleton.
Habitat: Usually on rock in deeper water and moderate to strong tidal streams. Also reported at the base of Posidonia (Mediterranean). Rather scarce.
Distribution: North Atlantic (Greenland, Shetland, Ireland, Azores); Mediterranean. Recently recorded from the Northern Irish coast (North Channel) and the Sound of Mull.
Distribution Map from NBN: Grid map (fast) : Interactive map (slower, requires login to view records) : National Biodiversity Network mapping facility, data for UK.
Identity: The form is somewhat reminiscent of some specimens of Axinella dissimilis (q.v.) with coalescent branches, or possibly Haliclona oculata (q.v.). However, it is easily distingushed 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.
Voucher: BELUM : Mc1471. Rathlin Island, Strangford Lough.
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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