Form: Variable, often basically a thin walled, laterally compressed cylindrical or pear shaped bag (the walls are thicker and almost muscular in comparison with the more common G. compressa). 'Thin' is used relative to the overall size of the sponge - the walls are thick when compared to those of Grantia compressa. It hangs from the point of attachment. (Note orientation in photograph). It can grow from 12-15 cm long, the largest specimens seen being 5cm in diameter and in excess of 1m long. There is also a more lobate form. There is a very short stalk.
Colour: Beige (alive or in alcohol).
Smell: Not noticeable.
Consistency: Firm but thin walled.
Surface: Smooth, slightly velvety.
Apertures: Usually a single terminal oscule, which is naked (i.e. with no collar of spicules).
Contraction: Will deflate, but no overall shrinkage.
Spicules: Oxea ca. 500Ám, triradiates with 100-200Ám rays; quadriradiates are also present, with rays 150-200Ám.
Habitat: Only recently known from two sites, in each case on vertical or overhung side of wreck in 5-20m. No current. Shallow site was exposed to moderate occasional swell.
Distribution: Recently found in Orkney on Scapa Flow block ships (voucher specimens). "Atlantic, N of UK!" Probably reaching southern limit off Northern Scotland. Earlier recorded from Shetland and Faeroes.
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 large specimens are unusually large for Calcarea and larger bag-like 'Grantia' forms in UK waters are likely to be this species. Smaller specimens could be confused with G. compressa.
Voucher: BELUM : Mc2127. Churchill causeway, Orkney. Coll. D. Moss.
Editors: R. Earll, 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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