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(Haeckel, 1870)

Species Overview

Sycon villosum (Haeckel, 1870) is a whitish ovate tube-shaped calcareous sponge. It is one of several Sycon species which can only reliably identified by microscopic examination. The characteristic feature of S. villosum are the long apical rays of the atrial tetractines filling up much of the internal cavity.

Taxonomic Description

Colour: White or grey.
Shape, size, surface and consistency: Small, ovate or cylindrical tubes with a short apical fringe surrounding the oscule. Size up to 2 cm high 0.7 cm in diameter, but normally not exceeding 1.2 x 0.5 cm. Surface minutely papillate-hispid. Consistency soft.
Spicules: (Sycon villosum spics) Calcareous. Triactines, regular or sagittal, in two forms: one (tubar triactines) with about equal sized paired rays and basal rays: 100-300 x 10-30 µm, and the other (choanosomal triactines) with thinner paired rays: 100-200 x 5-8 µm and longer and thinner basal rays: 100-400 x 5-8 µm.
Tetractines: with paired rays 100-200 x 5-8 µm, basal rays 100-400 x 5-8 µm and apical rays 500-1500 x 5-10 µm.
Oxeas: 1000-3000 x 10-30 µm.
Skeleton: Distal ends (cones are not clearly recognizable in this species) of radial tubes ornamented with oxeas; tubar skeleton made up of triactines and the basal rays of choanosomal triactines; choanosomal-atrial skeleton made up of the paired rays of choanosomal triactines and a tangential layer of triactines and tetractines. Atrial cavity is almost entirely filled by the apical rays—pointing upwards—of the tetractines.
Choanocyte chambers: Completely fused over their entire length.
Reproduction: August.
Ecology: On hard bottoms, in shallow depths down to 9 m.
Distribution: Scotland (E coast), Norway, Roscoff, Iles des Glénans.
Etymology: villosus (Latin) = hairy.
Type specimen information: BMNH 1882.3.6.20-1, BMNH 1882.3.6.31-2, BMNH 1882.3.6.33 (dry).

Remarks

The microscopic features are well-established and make this an easily recognizable species. It has not been recorded very often.
Source: Arndt, 1935.

Sycon villosum