Crella plana Picton & Goodwin, 2007


Family : Crellidae

Form: 2 mm thick peach encrusting sponge with numerous pore sieves. Forms quite small patches on bedrock, maximum patch diameter ranged between 2 and 6 cm.

Colour: Pale pink or peach coloured.

Consistency: Firm, tough, but thin.

Surface: The surface is covered with regularly spaced circular pore-sieves.

Apertures: The pore sieves are typically 1-2 mm in diameter and cover most of the surface of the sponge. In each patch there are one to a few larger oscules which have slightly raised transparent rims in living specimens.

Contraction: Oscules and pore sieves may close on disturbance.

Internal characters

Skeleton: The choanosomal skeleton consists of plumose bundles of tornotes between 50 and 80 μm in diameter rising from a basal layer of spongin in which acanthostyles are embedded, shaft upwards. Acanthoxea and fusiform acanthostyles are scattered through the choanosome and chelae are also present in small numbers. The ectosome is a multiple layered crust of tangential acanthostyles, up to 120 μm thick.

Spicules: Fusiform acanthoxeas entirely spined with large robust spines, 105 μm by 2 μm. Many of the spicules are bent in the middle. Most are between 4 and 8 μm in width but a few much thinner ones are present. Fusiform acanthostyles, 120 μm by 2 μm, very similar in appearance to the acanthoxeas, with large, robust spines. Most are between 4 and 8 μm in width but a few much thinner ones are present. One end tapers abruptly to a sharp point, the other is rounded but not tylote. Basal acanthostyles, 185 μm by 4 μm, tapering acanthostyles with a tylote head, entirely spined but the spines are much sparser and slightly smaller than those of the fusiform acanthostyles and acanthoxea. Tornotes, 310 μm by 5 μm are smooth fusiform oxea, pointed at both ends but one end tends to be more sharply pointed, some have mucronate ends. Chelae: 15 μm, arcuate.

Habitat: Found on tide-exposed vertical rock surfaces at 25-40m depth in sponge rich habitats.

Distribution: Currently only known from Rathlin Island, Co Antrim, Northern Ireland.

Identity: The spiculation does not match any existing Crella species, this species is unusual in possessing both acanthoxeas and fusiform acanthostyles in the choanosome. It is most similar in spiculation to Crella (Pytheas) schottlaenderi (Arndt, 1913) but this has curved tornotes which are oxeote or stylote and does not have choanosomal acanthoxeas.

Voucher: BELUM:Mc2746, holotype.

Editors: Claire Goodwin & Bernard Picton

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