Bath Sponge

Sponge

Identification & Biology

• IdentificationA large, rounded or irregularly lobed sponge with a soft, compressible texture and a dark brown to black exterior. The interior is lighter. Numerous large openings (oscula) are visible on the surface. When dried, the skeleton is the familiar soft, pale bath sponge.
• SizeDiameter up to 40 cm. One of the largest sponges in the Mediterranean.
• Social HabitSessile (permanently attached). Found singly or in groups on rocky substrates. Filter feeds by drawing water through thousands of tiny pores.
• HabitatRocky reefs, walls, and sheltered areas with moderate water flow. Requires hard substrate for attachment.
• Depth1 to 100 m. Most common between 5 and 40 m.
• Feeds OnBacteria, microalgae, and dissolved organic matter filtered from the water. Processes enormous volumes of water daily.
• DistributionMediterranean Sea and adjacent eastern Atlantic. Present in Maltese waters. Historically heavily harvested.
• DescriptionSpongia officinalis is the original bath sponge, harvested in the Mediterranean for thousands of years. The soft, elastic skeleton left after the living tissue decays has been used for bathing, cleaning, and painting since ancient times. Commercial sponge harvesting was once a major industry in Malta, Greece, and Tunisia. Wild populations have declined due to overharvesting and disease, and the species is now less common than it once was.