Phakellia ventilabrum (Linnaeus, 1767)


Family : Axinellidae

Form: Cuplike or lamellate, attached by fairly narrow base i.e. sub-stipitate. Edge of cup/fan sharp, frayed, not neatly rounded, except in juvenile specimens.

Colour: Grey, Also reported as "yellow, often with a green tint" (?). Confirmation would be valuable.

Smell: None

Consistency: Firm, elastic, fairly tough, but becomes laxer in older specimens, when it can become easily torn.

Surface: "Even." Slightly velvety; no projecting spicules visible to naked eye. In cuplike forms, the interior of the cup is dotted with small openings which are larger than the openings on the outer surface. Both surfaces have a tendency to be marked by an ascending system of "vein-like" lines. In older specimens the surface can become wrinkled (i.e. rugose), especially towards the base.

Apertures: Exhalent openings (oscules) are confined to one surface; in cuplike forms seen as pin-hole sized openings scattered over the inner surface of the cup. Pores are not visible with the naked eye (?).

Contraction: None.

Internal characters

Skeleton: Plumose. An axial or mesial condensation of densely packed vermiform megascleres (i.e. flexuous spicules), with radially arranged ascending plumose fibres arising from the core and branching and anastomosing towards the surface. At the surface they form brushes. Minimal amounts of spongin encase the spicules.

Spicules: Megascleres are long, vermiform strongyles (a) 420-(525)-620 x 7.5Ám forming the axial condensation, whereas the plumose fibres consist of styles (b) 220-(420Ám)-500 x 7.5Ám which are slightly curved at the base. "Styles may be supplemented or even replaced by oxea (c)" . These are mostly anisoxea, with one end finely tapering and the other blunt or telescoped. No microscleres are present.

Habitat: Slightly sheltered locations close to deep water. At St. John's Point, Donegal, at 30m on rock ridges. At Skird Rocks, Galway, characteristic of Konnecker's Axinellid association - Axinella dissimilis, Axinella infundibuliformis, Diazona violacea, Eunicella verrucosa, Alcyonium glomeratum.

Distribution: "Arctic, Atlantic coasts of Europe". Known recently from Ireland: the Aran Islands and Skird Rocks, Galway Bay; Donegal Bay; and W. Scotland: the entrance to Loch Sunart, Sound of Mull.

Distribution Map: NBN map : National Biodiversity Network mapping facility, data for UK.

Identity: Similar to Axinella infundibuliformis but often larger, more brittle, with a sharp edge to the cup (rounded in Axinella). Colour is grey, c.f. Axinella which is slightly brown to yellow. Axinella has trichodragmata and lacks vermiform megascleres. Other lamellate Axinellids recorded from British Isles include Axinella arctica Vosmaer, 1885:25. Phakellia robusta Bowerbank 1866:120 and Phakellia rugosa (Bwk 1862:770).

Voucher: BELUM : Mc449. St. John's Pt, Donegal.

Editors: D. Moss, B.E. Picton.

 Picton, B.E., Morrow, C.C. & van Soest, R.W.B., 2011. [In] Sponges of Britain and Ireland