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(Esper, 1791-1794)

Species Overview

Axinella damicornis (Esper, 1791-1794) is a branching-erect but often somewhat squat sponge, in which individual branches tend to fuse and result in irregular shapes. Colour bright ochre-yellow. Surface characteristically "mealy" (as if dusted with small particles) and velvety hispid. On vertical rocks, not uncommon on the west coasts of British Isles and France, but predominantly a Mediterranean species.

Taxonomic Description

Colour: Bright to deep yellow, verging sometimes towards deep orange at the margins. Distinctively 'bright'.
Shape, size, surface and consistency: Branching-erect with branches compressed and 'webbed' together (Axinella damicornis MCS). Variable in appearance. Up to 10 cm in height, with short stalk. The fusion of the branches tends to result in irregular growth forms in taller specimens. In lower growing, squatter specimens the lamellae become fused and convoluted (Axinella damicornis Pansini). The terminal branches are about 3 mm in diameter. Surface has characteristic 'mealy' appearance, as though dusted with small yellow particles. Surface velvety, with projecting spicules of uneven length, approximately twice that of A. dissimilis. Wide canals run up the sponge to arrive radially at 'vents' on the distal edges of the lamellae. Small oscules are borne on the apices of the lamellate branches. When alive, the open oscules are partially surrounded by a small triangular 'flap' of tissue, arising from the oscular rim. On collection this flap cannot be differentiated and the oscules themselves become inconspicuous. Consistency firm with strong axial skeleton. Lamellae are flexible. Contraction: none.
Spicules: (Axinella damicornis spics) Strongly developed styles to subtylostyles occasionally tylostyles, slightly bent: 320-1030 µm (in the Mediterranean the range is 180-1520 µm). Strongly developed oxeas, frequently bent in the middle, occasionally centrotylote: typically ca. 400-520 µm (in the Mediterranean the range is 25-470 µm: Pansini, 1983).
Skeleton: Axially condensed, extra-axially plumose. A dense central core composed mostly of bundles of (3 or 4) oxea, forming a plumose reticulation, which terminates in brushes of styles which penetrate the surface.
Reproduction: Oviparous. Oocytes in September (Lévi, 1950a, b). Buds between May and September in Mediterranean at Banyuls.
Chemistry: Pyrroloaminopropylimidazoles were reported from this species by Cimino et al., 1975, and Braekman and Dalloze, 1986.
Ecology: In Lough Hyne, SW Ireland, on vertical cliff face at 15 m in sheltered location. In Donegal, NW Ireland, on rock reefs at 30 m. In both localities Axinella dissimilis is also present. Donegal locations are moderately exposed to wave action. Eunicella verrucosa and Alyconium glomeratum are also characteristic of the habitat. It occurs in similar habitats in SW Britain, sometimes in silty locations, always (?) on sloping rock surfaces. Often found partly hidden in hydroid/bryozoan undergrowth on Lundy. Often bears zoanthids of Parazoanthus haddoni (Topsent, 1891a, Lévi, 1950a) (Axinella damicornis Schmidt).
Distribution: British Isles (recorded recently from W. coast of Ireland: Lough Hyne, Co. Cork; Skird Rocks, Galway Bay; St. John's Pt., Co. Donegal; Rathlin O'Birne Is., Co. Donegal; Scilly Isles; Channel Isles; Devon; Lundy), Roscoff; common in the whole of the Mediterranean.
Etymology: damicornis (Latin) = deer antler, referring to the ramose shape.
Type specimen information: Type probably lost. MCS voucher: BELUM Mc1306, Bretagne, France.

Remarks

The overall form is similar to Stelligera rigida but the mealy appearance of surface and bright yellow colour seem characteristic. Most readily confused with A. verrucosa (Esper, 1791-1794: 275), so far recorded from Roscoff (see Table below). It could be confused with A. pyramidata Stephens 1921: 63, but this species has not been recorded again since it was first described from off Co. Kerry at 68 m. Spicule complement confirms it as an Axinella.
The following table provides a list of visual characters for distinguishing between A. damicornis and A. verrucosa: A. damicornis & A. verrucosa.
Sources: Ackers et al., 1985 (B.E. Picton, S.M. Stone, D. Moss), 1992.

Axinella damicornis