Axinella pyramidata Stephens, 1916


Family : Axinellidae

Form: In shape this species is somewhat like a three-sided pyramid standing on its apex, except that the sides are deeply cut vertically into a series of flattened lobes. Height 15 mm, diameter 17-30 mm.

Colour: Pale brown, beige.

Surface: The upper surface is flat overall, dissected into small knob-like elevations.

Apertures: Oscules are inconspicuous, at the tip of small transparent chimneys of tissue, usually at the convergence of surface grooves.

Contraction: very little.

Internal characters

Skeleton: The skeleton consists of closely set plumose columns of spicules which run upwards through the sponge, and then bend out towards the surface, where they end in brushes of styles which project for part of their length beyond the surface; a considerable amount of spongin is present, cementing the spicules together.

Spicules: Styles variable: about 230-1000 x 10-16 Ám; in the shorter styles the shaft is rather sharply bent at a little distance above the head; the longer styles are usually slightly curved; there is sometimes a slight swelling on the shaft a little distance above the head. Oxeas: 300-600 x 10-13 Ám; they are sharply and irregularly bent and taper at either end to a rather sharp point; many of the oxeas have a slight swelling about the middle of the spicule.

Habitat: On rock or stable boulders 30-99 m.

Distribution: Off SW Ireland, Rathlin Island (Co Antrim), Faroes, Roscoff; ?West Africa.

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

Identity: Spiculation is similar to Axinella damicornis and that species may form rather squat individuals which approach A. pyramidata in form. On re-examination the type was found to have numerous trichodragmata which are not mentioned in the original description. A. damicornis does not have trichodragmata. The specimen recorded from West Africa (Burton, 1956) (Axinella pyramidata Burton) may not be conspecific with Stephens' specimen.

Editors: Christine Morrow, Bernard Picton & Rob van Soest.

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