Noah's Ark shell

Mollusc

Identification & Biology

• IdentificationA bivalve with an elongated, rectangular shell that is dark brown to black, covered in a distinctive hairy periostracum (outer shell layer). The shell shape is said to resemble the hull of a boat, giving it its common name. Often found in dense clusters.
• SizeShell length up to 9 cm.
• Social HabitGregarious. Attaches to hard surfaces in clusters using byssus threads (strong protein filaments). Forms dense beds on suitable substrates.
• HabitatRocky reefs, boulders, and any hard substrate in shallow to moderate water. Often found in crevices and on overhangs.
• Depth0 to 50 m. Most common between 2 and 25 m.
• Feeds OnPlankton and suspended organic particles filtered from the water.
• DistributionEastern Atlantic and throughout the Mediterranean Sea. Common in Maltese waters.
• DescriptionArca noae takes its name from the biblical Ark of Noah, with its boat-shaped shell supposedly resembling the hull of a vessel. It is a common sight on Maltese reefs, often forming small clusters in crevices and on the undersides of overhangs. The dark, hairy periostracum covering the shell makes it distinctive even when encrusted with other organisms. It is occasionally harvested for food in parts of the Mediterranean.