Form: In shape this species consists of rounded lobes with a slightly narrower base, 1–3 cm in width and height. Pale yellow-brown in colour with a grooved or sulcate appearance to the surface.
Apertures: The oscules are inconspicuous, at the tip of small transparent chimneys of tissue.
Contraction: Specimens contract on collection and the sulcate grooves disappear.
Skeleton: There is a basal skeleton of oxeas, with ascending plumose columns of styles, oriented with their points towards the surface. There is no axial column, just a condensation of spicules at the centre of the base of the sponge. At the surface a few styles penetrate a short distance, but the surface does not appear hispid. Oxeas occur within the plumose columns, typically oriented across the columns.
Spicules: Styles mostly 600–900 μm by 16–23 μm (but with a few extremes to 250–1070 μm). Usually smoothly bent about 1/4 of the way down the shaft. Some styles have rounded ends and many have telescoped ends, the rest taper smoothly to sharp points. Oxea 300–500 μm (with a few to 710 μm) by 10–16 μm, typically half the diameter of the styles. Usually bent twice, often in different directions and at different angles, somewhat contorted in appearance. The ends taper smoothly and are frequently telescoped. Occasional oxea are centrotylote or appear to be formed by fusion of two styles, with rounded swellings on opposite sides of the spicule.
Habitat: Found at depths of 20-35m in strong tidal streams, attached to horizontal bedrock.
Distribution: Known only from the North Channel, between Ireland and Scotland. Specimens have been found on Rathlin Island and at the Maidens, off Larne.
Identity: Many Axinella species have a spicule complement of only oxeas and styles, this species differs from others in the northeast Atlantic area in the sizes of these spicules. It is small and inconspicuous and occurs with Axinella pyramidata on Rathlin Island. Axinella pyramidata is also a small species, but has abundant trichodragmata and smaller, thinner styles. This species is easy to recognize in situ by its shape and colour and the sulcate grooves in the surface.
Editors: Claire Goodwin & Bernard Picton
|Picton, B.E., Morrow, C.C. & van Soest, R.W.B., 2011. [In] Sponges of Britain and Ireland |
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