Growth form irregular, massive; usually less than 10 cm in diameter, sometimes up to 15–20 cm in diameter and 2–3 cm in height. Colour in vivo (generally also preserved specimens) light grey to white; several, slightly perceptible, tone dominances are possible (light green to light brown). Consistency soft and fragile. Surface, shared by all species of the genus, as an irregular network of dense collagen fibres, sometimes with mineral debris. Inhalant apertures 80–120 µm in diameter. Oscules scattered (2–4 mm in diameter). Light collagen amount (fibrous reticulate) in the mesohyl. Flagellate chambers large. Skeleton reticulate, with irregular meshes (300–600 µm), and extremely fragile because of scanty spongin and extreme abundance of mineral granulation. Primary and secondary fibres (40–200 µm) not distinguishable or hierarchically organized. 

 Dysidea fragilis 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).

This sponge is usually whitish or grey in colour but can also be brown. In cases where sand grains predominate over organic matter the sponge can assume the colour of sand. It may be thinly encrusting or cushion to massive lobose in form. It is usually less than 15cm across, but can be greater than this in tidal, rocky estuaries. The surface is conulate, because of spongin fibres lifting the surface layer. The projections are sometimes lighter in colour than the main surface. This species may be confused with Dysidea pallescens which is pink-purple in colour with relatively larger oscules.

Aegean Sea, Atlantic, Australia, Azores Canaries Madeira, Azores Exclusive Economic Zone, Barents Sea, Belgian Exclusive Economic Zone, Bermuda, Black Sea, Canary Islands Exclusive Economic Zone, Caribbean Sea, Celtic Seas, Chatham Island, Circum-equitorial, Cosmopolitan (World Oceans), Cuba, European waters (ERMS scope), Freetown, Greek Exclusive Economic Zone, Gulf of Guinea Central, Gulf of Guinea West, Gulf of Mexico, Indian Ocean, Inhaca Island, Irish Exclusive economic Zone, Kara Sea, Laptev Sea, Levantine Sea, Mahe Island, Mediterranean Sea, Mexico, Namibian Exclusive Economic Zone, New Zealand Exclusive Economic Zone, North East Atlantic, North Sea, Off Bathurst, Pacific Ocean, Red Sea, Sea of Japan, South European Atlantic Shelf, Southern Norway, Tunisia, Tunisian Plateau/Gulf of Sidra, United Kingdom Exclusive Economic Zone, West Africa, White Sea, Wimereux, Zanzibar

A common species throughout the British Isles.

Depth range based on 391 specimens in 1 taxon.
Water temperature and chemistry ranges based on 68 samples.

Environmental ranges
  Depth range (m): 0 - 140
  Temperature range (°C): 9.788 - 27.228
  Nitrate (umol/L): 0.236 - 9.794
  Salinity (PPS): 34.633 - 37.656
  Oxygen (ml/l): 4.352 - 6.375
  Phosphate (umol/l): 0.095 - 0.585
  Silicate (umol/l): 1.232 - 3.727

Graphical representation

Depth range (m): 0 - 140

Temperature range (°C): 9.788 - 27.228

Nitrate (umol/L): 0.236 - 9.794

Salinity (PPS): 34.633 - 37.656

Oxygen (ml/l): 4.352 - 6.375

Phosphate (umol/l): 0.095 - 0.585

Silicate (umol/l): 1.232 - 3.727
 
Note: this information has not been validated. Check this *note*. Your feedback is most welcome.

 Dysidea fragilis is a cryptic species and can be found on the lower shore and sublittoral. It lives in rock crevices, on stones, shell and gravel. It has also been found embedded in muddy sand.

An almost ubiquitous species under boulders on the low shore and on hard substrata in the sublittoral.