Gold Sponge

Overview

The Gold Sponge (Aplysina aerophoba) is a distinctive, tube-forming sponge native to the Mediterranean Sea and parts of the eastern Atlantic Ocean. It is well-known for its vibrant yellow color and its unique reaction to air, which causes it to turn blue-black when removed from the water.

Distribution & habitat

This species is primarily found in the Mediterranean and extends into the nearby Atlantic along the coasts of Portugal and Spain. It is a photophilic (light-loving) organism that typically inhabits sunlit, rocky substrates or seagrass beds in relatively calm, clear waters.

Appearance

Aplysina aerophoba forms colonies that can reach up to one meter across, consisting of irregular, finger-like tubular processes. Each tube is generally firm and rubbery, featuring a flattened top with a central osculum (exhalant pore). The surface is smooth yet slippery, often covered with small, cylindrical projections. While the exterior is yellow, the internal flesh is a brighter yellow.

Biology & behavior

The name "aerophoba," meaning "fear of air," refers to the sponge's rapid color change to blue or black upon exposure to the atmosphere, a result of chemical reactions within its cells. Unlike many other sponges, it lacks siliceous spicules, relying instead on a skeleton of tough, fibrous material. It may occasionally host colonies of Nausithoe polyps.