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Grant, 1826

Species Overview

Cliona celata Grant (1826) is a yellow excavating (or boring) sponge, occurring in two distinct forms. One is the boring form, recognizable as yellow papillae sticking out of limestone (calcareous rocks, shells, etc.); the other is a large massive, wall-shaped sponge covered with characteristic flattened papillae. This species is the only excavating sponge in NW Europe developing the massive form; other species of Cliona only occur in the boring form. It is also the only Cliona without microscleres (microscopic examination necessary). The massive form is very common around the west coasts of Britain and France but is lacking in the North Sea. The boring form is very common in oyster and mussel beds, where they cause some damage to shell fish farming. It may be confused with similarly coloured C. lobata, but that species has much smaller and more numerous papillae, and it has microscleres.

Taxonomic Description

Colour: Yellow, becomes darker out of water and in alcohol goes brown discolouring both the alcohol and the specimen labels. Sometimes observed with red discolouration surrounding oscular openings.
Shape, size, surface and consistency: One of the few excavating species which produces a massive or 'raphyrus' or 'gamma' stage (Raphyrus griffithsi). In the 'gamma' stage (Cliona celata gamma stage) the sponge becomes massive-lobose with rounded ridges up to 40 cm across. It often forms a thick plate-like structure standing on its edge and up to 100 cm long. In the boring stage (Cliona celata MCS3) it is seen as clear sulphur-lemon lobes, which are the rounded tips of papillae, and are found studding limestone rock, shells, etc. The massive form is evenly covered by rather tuberculate retractable inhalant papillae (Cliona celata MCS2). The surface between these papillae is more or less smooth. In the massive form large oscules with raised rims are found along the tops of ridges. Delicate, thin walled, retractable inhalant papillae 2-5 mm in diameter, which project up to 1 cm above the surface when extended, cover the remainder of the surface (Cliona celata Topsent). These are not noticeable when out of the water as they close and retract below the surface.
In the boring stage apertures are at the tips of the papillae. Galleries (Cliona celata in Ostrea) made by this species are relative coarse and wide (up to 1.5 mm in diameter) compared to those of the other Cliona species in the area (excepting deep-water C. caledoniae). The internal damage to oysters and other commercial molluscs may be extensive and limestone calluses may take up a large part of the intervalvar space (Cliona celata in oyster).
Consistency firm with tough outer layer, compact. Contraction: The whole sponge shows a noticeable decrease in size when removed from the water. The papillae, and to a lesser extent the oscules, contract to such an extent that they become almost invisible out of the water.
Spicules: (Cliona celata spics) Megascleres are tylostyles: 280-350-430 x 2-8 µm, densely and irregularly arranged. The heads have swellings just below the tip in most spicules. Microscleres are apparently normally absent; if present, they are raphides. The raphides may have been young stages of the tylostyles.
Skeleton: Confused, showing no differentiation into ectosomal and choanosomal skeletons.
Reproduction: This is a hermaphroditic species. Oocytes and sperm cysts were found in the period between June and November (Wapstra and Van Soest, 1987). Despite reports from vivipary in this species from the east coast of the U.S.A., evidence for this is lacking in European populations. Asexual buds are produced under unfavourable conditions.
Ecology: Massive form occurs on rock. Begins life by boring into limestone, shells or calcareous red algae. Can withstand sediment. Favoured shells are e.g. Ostrea edulis, Crassostrea gigas, Crepidula fornicata and Arctica islandica.
Distribution: Widely distributed along all Western European coastlines. Also reported from most areas of the world, but these records need verification. The massive form is very common in parts of SW Britain and along the coasts of Brittanny, sometimes dominating the underwater 'scenery'. This form apparently reaches its easterly limit around Dorset in the Channel; apparently not found on either side of the North Sea.
Etymology: celatus (Latin) = concealed or hidden, referring to the boring habit,
Type specimen information: Possibly Royal College of Surgeons or Edinburgh (suggested by Hooper and Wiedenmayer, 1994: 131, and Rützler and Stone, 1986). MCS voucher: BELUM Mc174, Strangford Lough, N Ireland.


Recognizable by sight alone if massive form, the colour and inhalant sieve-like openings are distinctive. The boring form can be identified to genus by sight alone, but cannot be confused with any other genus except for Aka, Thoosa and Alectona, occasionally found in deeper waters. Other Cliona species in the area are C. lobata, C. caledoniae and Pione vastifica, which have similar (C. caledoniae), smaller (lobata) and more orange-red papillae (vastifica); all three possess microscleres.
Cliona alderi Hancock (1849) was synonymized with this species by Bowerbank (1866), but Rützler and Stone (1986) suggest this may be a separate species.
Sources: Ackers et al., 1992 (J.D. Guiterman, S.M. Stone, B. E. Picton).

Cliona celata