Form: Variable in shape but usually cup-like or lamellate. The walls are of regular thickness with the margins of the cup/fan rounded and firm. Stalked or substipitate.
Colour: Buff, pale creamy-yellow.
Consistency: Moderately firm and resilient. Pieces break off if bent through 90 degrees. "Compact."
Surface: The outer surface presents moderate friction when rubbed. The inner surface has many pin hole sized exhalent openings. These are larger than the inhalent pores on the outer surface. Neither surface is bristly.
Apertures: Oscules are "small, scattered evenly" over one surface; in cup-like specimens, all the exhalent openings are found on the inner surface.
Contraction: Not noticeable.
Skeleton: Plumoreticulate. The contrast between a stiffer axial skeleton and a softer extra-axial skeleton, which is characteristic of branched Axinellids, is scarcely noticeable in this species. The megascleres tend to show an axial condensation towards the centre of the choanosome, and a sub-anisotropic reticulation in the extra-axial regions with sub-plumose primary fibres (the amounts of spongin encasing spicules is variable), ending as brushes at the surface. (NOTE: the variability of the spicule complement and architectural structure is a well-known feature of Axinellids. All kinds of combination can be found e.g. megascleres can be all oxea (making confusion with Halichondrida possible), or all styles. If both types are present together, a zonation can often be detected i.e. in a reticulation, the multispicular primary fibres are usually formed by styles and the connective secondary fibres formed of oxea (often unispicular or up to 3 spicules thick). Surface brushes may consist of long or short spicules which pierce the surface (resulting in a rough surface, smooth surfaces being a rarity in Axinellids). Dense axial skeleton may be absent; extra-axial reticulation may be completely replaced by plumose fibres.)
Spicules: Megascleres are styles (a) 260-(330)-360Ám and oxea (b) 210-(250)-280Ám (slightly curved) and occasionally strongyles. Microscleres are trichodragmata (c), longer than those of Axinella dissimilis but often inconspicuous.
Habitat: "Shallow sublittoral to 630m." Usually found on bedrock, cliff ledges, or stable boulders in the circalittoral zone, usually on horizontal surfaces in semi-sheltered conditions where it must be tolerant of the presence of sediment. Reported on "shells, gravel stones, sand or mud" but this may refer to dredgings from deeper water. (??)-confirmation of this would be valuable.
Distribution: "Norway; Faeroes; U.K.; North and East France." Recently known from W. coasts of Scotland and Ireland; Anglesey; Lundy; etc where it is a common and conspicuous species in the right habitat. Apparently not found on North Sea coasts of the U.K., although a photographic record exists from off Northumberland. (Bamber & Coughlan, 1989)
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 well formed cup with rounded edges, attached by a central stalk, is unlikely to be anything but Axinella infundibuliformis. However a few other rarer species form cups so identification should be confirmed by microscopic examination. Phakellia ventilabrum (q.v.) is one such species, distinguished by possessing long flexuous (vermiform) styles (not straight or slightly curved ones). Phakellia ventilabrum is said to have thin walls and a sharp edged rim to its cup, and also to differ in texture from Axinella infundibuliformis, being of a laxer consistency.
Voucher: BELUM : Mc1530. Ardnoe Pt, Sound of Jura.
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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