Spongia agaricina Pallas (1766) is a flattened, plate-like sponge of superior bath-sponge quality, known in the trade as the "elephant-ear" sponge. It is a Mediterranean species which has been found also along the Portugese Atkantic coast.
Colour: Beige or dark maroon.
Shape, size, surface and consistency: Flattened, plate-like shape, or shallow-cup shape. Size normally 15-25 cm wide, 1-4 cm thick; however, much larger specimens, up to 1 m wide are known. The Atlantic coast specimens are 15 cm wide at most. Surface finely conulose. Oscules only on the inside or upper side of the plate. Consistency supple, elastic.
Skeleton: (Spongia agaricina fibres) Ectosome strengthened by a light reticulation of sand grains. Primary fibres cored by sand grains, 35-75 µm in diameter; secondary fibres free from inclusions, 10-30 µm in diameter. Skeletal meshvery similar to that of S. officinalis.
Ecology: In caves at 5-15 m, on rock faces in deeper water, down to 300 m.
Distribution: Mid-Portugal; Mediterranean.
Etymology: agaricum (Greek) = tinder fungus, i.e. a flattened toadstool, referring to the shape.
Type specimen information: Type is probably lost.
The shape of the sponge is distinctive.
The elephant ear sponge has very good commercial qualities, and has been widely used for glass polishing, pottery and and is now also valued for decoration. It has always been less common than the most widely used Mediterranean commercial sponges, Spongia officinalis and Hippospongia communis. Price has dramatically increased after the 1986 disease of Mediterranean commercial sponges, although the species has been relatively less affected because it may occur deeper (up to 100-120 m), where the disease was less severe. The species is not really endangered, especially as
it may be found from a few meters depth (where the sponge has a poor
commercial value due to an irregular shape) up to 120 m. But it will become
rarer and more expensive on the market.
There is some concern in pottery-making circles about this sponge which is used by potters when throwing pots on the wheel. It is held in the right hand to keep the outside of the pot lubricated with water while pulling up the fold of clay created by pressure of the left hand on the inside of the pot. The concern among potters stems from the fact that elephant ear sponges are increasingly expensive and hard to get. They work better than artificial sponge substitutes.
Source: Vacelet, 1959: 77; Vacelet in litteris (1997); Mackie in litteris, 1996.