can be irregularly encrusting or massive and lobe-shaped. Encrusting forms may be up to 50 cm in diameter and 0.75 cm thick. Massive forms can be up to 30 cm in diameter. This species can vary in colour from brownish, greenish, greyish-white or reddish brown. The surface is covered in small conical projections (conuli) 1.5 mm in height and 2-2.5 mm diameter at the base. These conical projections are often lighter in colour. The exhalent openings (oscula) are scattered across the surface, can be slightly raised and vary in size from 2 to 5 mm in width. There are no spicules present and the skeleton is composed of spongin fibres making the consistency of Dysidea fragilis
very elastic.Dysidea fragilis
has a distinctive smell and may be sandy in colour where sand dominates the substrata. Interestingly, larger specimens may be found in tidal, rocky esturanine areas, and specimens in northern waters tend to be smaller in size. The skeleton of this species is often partially or completely obscured by sand grains, spicules of other sponges, diatom valves, formainifera and other hard materials. Such materials may be incorporated in within the skeleton (Hayward & Ryland, 1995).
The barnacle Acasta spongites forms a specific association with Dysidea fragilis (Uriz et al., 1992). Dysidea fragilis may be mistaken for the very polymorphic Ulosa digitata, however, unlike Dysidea fragilis, Ulosa digitata has styles coring into its fibres (only visible under a microcope). Dysidea pallescens is a Mediterranean species also similar to Dysidea fragilis. Dysidea pallescens has is pink-purple in colouration with larger oscula and occurs in Lough Hyne, although may be found in other UK areas (Ackers et al., 1992).