Oyster Sponge

Overview

The Oyster Sponge (Crambe crambe) is a common encrusting sponge frequently found in the Mediterranean Sea. It typically forms thin, flat, orange to orange-red plates that can cover significant surface areas on rocky substrates or the shells of living bivalves.

Appearance

This species is characterized by its vibrant orange or reddish coloration and a relatively smooth, slippery surface. Its body is marked by a visible network of internal channels that lead to raised, distinct oscula—the openings through which the sponge expels filtered water. While it generally forms thin, flat layers, it can occasionally appear slightly lobed.

Biology & behavior

Crambe crambe is a hermaphroditic filter feeder that survives by consuming bacteria, microorganisms, and single-celled algae from the water column. It is a sessile organism that often colonizes the shells of sedentary mollusks, such as the Noah's Ark shell (Arca noae) or spiny oysters (Spondylus), effectively camouflaging them. The sponge produces chemical compounds that serve as antifungal and antibacterial defenses, and it is known to be toxic to some potential predators. Its planktonic larvae settle on nearby surfaces to begin new colonies, and the sponge is known to communicate with others of its kind through the release of microparticles into the water.