Form: Very thin sheets (less than 1mm?)
Colour: Brown or yellow.
Surface: Even, smooth, slightly hispid. Subsurface canal patterns visible in some specimens.
Apertures: Not apparent if canal patterns absent.
Contraction: Slight, accompanied by closure of canals.
Skeleton: In very thin specimens, the skeleton consists of tylostyles arranged perpendicularly to the substrate, with the heads nearer to the substrate and sometimes touching it. In thicker specimens the basal spicules are overlain by spicule bundles that anastomize and may run either perpendicular or parallel to the substrate. At the surface the spicule bundles usually support projecting tufts of spicules (causing the hispid appearance), but tangential spicules may also be present in the dermal membrane.
Spicules: The megascleres are tylostyles (a,b), usually from about 110-(145)-180 x 4μm and 220-(300)-350 x 7μm in a given specimen. However, lengths to ca. 600μm and widths to ca. 11μm may occur in some specimens. There is no consistent relation between length and width (width is measured just beneath the head). The shafts are usually curved. The curvature occurs about one quarter to one third the length of the shaft from the head and is sometimes pronounced. The shaft tapers gradually to a sharp point in the distal half to one third of its length. The greatest thickness is just above the head. The head is smooth and shaped like an old-fashioned door handle, weakly mucronate spicules being rare. Thinner spicules often exhibit a smaller additional swelling immediately adjacent to the head. Microscleres are absent.
Habitat: On undersides of boulders, shells, other animals and algae. Specimens tend to be small and cryptic but can form thin sheets to 10cm in extent. Shore to ca. 12 m.
Distribution: Recently known from Anglesey (Church Island, Menai Straits), Plymouth, Roscoff.
Distribution Map from NBN: Grid map (fast) : Interactive map (slower, requires login to view records) : National Biodiversity Network mapping facility, data for UK.
Identity: A microscopic examination is essential. A combination of spicules orientated perpendicularly to the substrate, door-handle like heads and the other spicule characteristics described above can confirm identity. Reliable field identification characteristics are not yet known.
Voucher: BELUM : Mc856. Menai Straits, Wales.
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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