Bath Sponge

• The traditional bath sponge is this animal's cleaned skeleton: the living tissue is removed and only the spongin mesh remains, soft and absorbent.
• Harvesting it sustained whole Mediterranean economies for centuries, first with breath-hold divers and later with diving suits, and it was one of the most dangerous underwater trades that has ever existed.
• Successive epidemics since the 1980s, together with overharvesting, have cut its populations drastically.
• It is the classic bath sponge, and its exploitation is one of the oldest fisheries in the Mediterranean: it has been harvested since antiquity and appears in Aristotle and in Homer.
• What is used is not the animal but its skeleton: a mesh of spongin, a flexible, resistant protein, which is left when the living tissues are removed. It can absorb several times its own weight in water.
• Sponge fishing by free-diving to tear the sponges loose was an enormous industry in Greece, Tunisia and Florida, and one of the most dangerous: the use of diving suits in the 20th century caused hundreds of cases of decompression sickness among the sponge divers of the Aegean.
• Its populations collapsed in the 1980s and 1990s through mass epidemics of bacterial and fungal origin, on top of overexploitation, and have not recovered.
• It filters thousands of litres a day and harbours an extremely dense microbial community, which can account for a third of its mass and from which numerous bioactive compounds have been isolated.
• It grows very slowly and can live for decades, so a stripped bed takes a very long time to return.

Skeleton type

Invertebrate - spongin skeleton (sponge)

Habitat & environment

Rocky, semi-dark bottoms of the Mediterranean, from 5 to 40 m

Sources consulted: Pronzato y Manconi (2008), Marine Ecology; Lista Roja de la UICN; Voultsiadou, trabajos sobre esponjas del Egeo; FAO