Noble Pen Shell

Mollusc

Identification & Biology

• IdentificationThe largest bivalve in the Mediterranean, with a fan-shaped, triangular shell that can reach impressive sizes. The shell is thin, fragile, and dark brown to olive-green. It stands upright in the seabed, anchored by strong byssus threads. The interior produces a golden byssus known as sea silk.
• SizeShell length up to 120 cm, making it the largest native bivalve mollusc in the Mediterranean.
• Social HabitLives in scattered populations in seagrass meadows. The shell provides habitat for many other organisms that settle on its surface.
• HabitatPosidonia oceanica seagrass meadows and sandy bottoms. Requires soft substrate to anchor its pointed base.
• Depth0.5 to 60 m. Most common between 2 and 20 m in Posidonia meadows.
• Feeds OnPlankton and suspended organic particles filtered from the water through its gills.
• DistributionMediterranean Sea only. Endemic to the Mediterranean. Now critically rare across almost its entire range.
• DescriptionPinna nobilis is the most iconic and most endangered bivalve in the Mediterranean. A mass mortality event caused by the parasite Haplosporidium pinnae, first detected in 2016, has killed over 99% of the population across the entire Mediterranean basin. The species is now functionally extinct in most areas and listed as Critically Endangered. In Malta, surviving individuals are extremely rare. It is strictly protected and must never be disturbed.