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(Bowerbank, 1866)

Species Overview

Suberites virgultosus (Bowerbank, 1866) is a characteristic wedge-shaped sponge fixed on dead gastropod or bivalve shells which are partly buried in the sand. Colour greyish orange. Specimens may grow up to 20 cm high and 15 cm in diameter, with a gradually narrowed basal part (not a stalk separate from the main body). Occasionally the upper part is somewhat lobate. Very few if any oscules are apparent, so they are probably quite small. Consistency soft. Specimens may shrink considerably when taken out of the water. Common on the Dogger Bank in the Central North Sea.

Taxonomic Description

Colour: Greyish orange.
Shape, size, surface and consistency: (Hymeniacidon virgultosa) (Suberites virgultosus Ned) Elongate, wedge-shaped sponge of up to 20 cm in length and up to 15 cm in diameter. The upper parts of the sponge are broad and may be lobate, the lower parts gradually taper towards the substrate, which is invariably a dead shell of a mollusc (gastropods, bivalves, Dentalium) which are partly or wholly buried in the sand. Surface optically smooth but somewhat rough to the touch, coarser than in most other Suberites species of teh area. Oscules not apparent and probably small. Consistency fairly soft, compressible, flexible.
Spicules: Tylostyles, which are for a good proportion style-like, with barely visible swelling: up to 400 x 10 µm; centrotylote microstrongyles abundant, 20-50 µm.
Skeleton: The usual bouquets of smaller tylostyles at the surface laced with centrotylote microrhabds. In the interior the skeleton is a confused reticulation of ill-defined spicule tracts.
Ecology: On sandy bottom, on mollusc shells at depths of 30-50 m; very characteristic of the fauna of the Central North Sea.
Distribution: Known predominantly from the North Sea, but due to confusion with Suberites ficus the extent of its distribution is not well understood.
Etymology: virgultum (Latin) = bush, referring in this case somewhat exaggeratingly to the shape.
Type specimen information: BMNH 1847.9.7.48 (dry), Scarborough, Yorkshire. Slides from type unregistered (Bk 513), Mr. Bean's Collection.

Remarks

As with most other Suberites species of the area, this species also poses vexing taxonomic and nomenclatorial difficulties. The spiculation generally matches that of Suberites ficus but the high proportion of styles may be considered a significant difference. The growth form likewise approaches certain elongate lobate forms of S. ficus, but that species always has several conspicuous oscules, which are here considered further evidence for separate specific status.
The name Spongia virgultosa goes back to Esper (1794), but it is generally assumed that this is not the same species as what is described above. Subsequent assignments of Lamarck (1814) and Lamouroux (1824), likewise are obviously different species. The use of the name virgultosa for a Suberites-type sponge is ascribed to Johnston (1842 as Halichondria), but the figure of the habit provided by that author (a thin branch with a row of oscules) and his admission that he had seen only fragments, do not provide sufficient evidence that Johnston's material was identical to the species described here. Only Bowerbank's description and drawings form a perfect match, and accordingly we propose to assign the authorship of Suberites virgultosus to that author. The fact that Bowerbank used the combination Hymeniacidon virgultosa forms sufficient grounds for assigning his material type status, despite his reference to Johnston's Halichondria virgultosa. However, a future revision should corroborate these decisions and observations.
Source: Bowerbank, 1866, 1874.

Suberites virgultosus