(Johnston, 1842)
Species Overview
Suberites carnosus (Johnston, 1842) in its typical form is a stalked fig-shaped orange sponge, with a central apical oscule. More irregular specimens appear to be fused individuals taking a more massive shape and exhibiting several oscules. The extreme contractibility (it shrinks to 1/4 of its size when prodded) of this species is unique and characteristic. The surface is smooth, velvety; the consistency is weak in its expanded form, but more firm when contracted. It is a common species in shallow water.
Taxonomic Description
Colour: Various shades of pale yellow, buff, orange and brown.
Shape, size, surface and consistency: (Suberites carnosus MCS2) (Hymeniacidon carnosa) In the British Isles it typically assumes a hollow contractile, massive fig-shape, attached by a stalk to the substrate. Size typically a few cm high and across. On the Continent a variety of forms have been recognized, graduating from thin sheets and cushions to massive-lobose and even branching forms (see Topsent, 1900, p.233). These forms have yet to be found in British waters. There is some doubt whether all these forms are really one and the same species (cf. also descriptions of Suberites massa) . Surface smooth, even, with a minutely velvety feel. This is most easily detected with the tongue. The upper surface is often lightly coated with silt. Usually one oscule, at the top, but there may be more. If so, they are usually all on the uppermost surface. Consistency firm and moderately elastic when out of water. Extremely soft when fully expanded under water. Stalk breaks when bent through 20 deg. (when in contracted condition). Contraction very dramatic, contracts to about 1/4 of its fully expanded size when disturbed. Full contraction takes about 15 seconds. Further contraction occurs when the sponge is removed from the water. Smells faintly of freshly cut Laminaria stipe.
Spicules: (Suberites carnosus spics) Tylostyles, 130-570 µm long, in two distinct sizes. In any given specimen spicules are of a narrower size range than S . ficus . No microscleres.
Skeleton: Subradiate, the radial arrangement of the spicules being most apparent near the surface. Internally the skeleton is confused, almost halichondroid. The larger tylostyles constitute the main structural megascleres, whereas the smaller are perpendicularly arranged as plumose brushes (resembling shaving brushes) at the surface. In the stalk region the spicules are condensed to form an axial skeleton.
Ecology: Usually growing vertically. Sometimes found in muddy places attached to shells or stones buried in the mud, e.g. in harbours and Scottish sea lochs. Down to 108 m.
Distribution: Arctic; Atlantic coasts of Europe; Mediterranean; etc.
Etymology: Carnosus (Latin) = fleshy.
Type specimen information: Type: BMNH, unregistered (431E) (dry), Dr. Johnston.
Remarks
Differences between S . carnosus and S . ficus (based on criteria communicated by S.M. Stone): S. carnosus & S. ficus.
Sources: Ackers et al., 1985 (J.D. Guiterman, S.M. Stone, B.E. Picton, D. Moss).