Spongia virgultosa (Schmidt, 1868) is a massive sponge, that may not be easily recognized as such because it is always overgrown by other organisms, including other sponges. Because of the "buried" way of life it develops fistule-like outgrowths. It has the elasticity of bath-sponges but is not exploited. It is a Mediterranean species which has been found along the Atlantic coast of Portugal.
Colour: Greyish maroon.
Shape, size, surface and consistency: Thickly encrusting to massive, with fistular outgrowths. Size up to 8 cm in lateral expansion, 4-5 cm wide and 1 cm thick. Papillae up to 1.5 cm long, 0.5 cm in diameter. Surface covered by epibonts, often other sponges. Consistency compressible, elastic, but less so than the true bath-sponges.
Skeleton: (Spongia virgultosa fibres) Primary fibres have inclusions, mostly spicular debris and a dustinct pith; they are rare in the base of the sponge but form the supporting skeleton of the papillae. Size 50-80 µm. Secondary fibres are devoid of inclusion and pith, size 10-50 µm.
Ecology: Shallow water, in caves and among calcareous algae, 1-150 m.
Distribution: Mid-Portugal; Mediterranean.
Etymology: virgultum (Latin) = bush, presumably referring to the fistular outgrowths of this sponge.
Type specimen information: No specimens have been found; there are slides in the Paris Museum, MNHN DT 774, and the Natural History Museum, London, BMNH 1868:3:2:14.
This species stands out among the Spongia species of the area by its massively encrusting habit with fistular outgrowths.
Source: Vacelet, 1959.