This is the Noble Pen Shell (Pinna nobilis), one of the largest bivalve mollusks in the world. It is endemic to the Mediterranean Sea and commonly found in seagrass beds, especially Posidonia oceanica. Once abundant, its populations have declined drastically due to disease outbreaks, habitat loss, and human activity. It is now classified as Critically Endangered, with conservation efforts focusing on refugia and habitat protection.

Location:
Endemic to the Mediterranean Sea. Found along the coasts of Spain, France, Italy, Greece, Turkey, and parts of North Africa.

Average Size:
Typically up to 100 cm in length, but can reach up to 120 cm.

Family:
Pinnidae (Pen Shells)

Species:
Pinna nobilis

Ecological Role:
Pinna nobilis is a filter feeder that helps improve water quality by filtering plankton and suspended particles. It also provides microhabitats for a variety of small marine species, including the symbiotic shrimp Pontonia pinnophylax. It plays a key ecological role in seagrass ecosystems by stabilizing sediment and supporting biodiversity.

Reproduction:
Pinna nobilis is a sequential hermaphrodite, starting life as a male and later developing female reproductive organs. Fertilization is external, and the larvae are planktonic before settling onto the seabed. The shell is anchored into the sediment using tough byssus threads, which were historically harvested to make “sea silk.”

Conservation Status:
Pinna nobilis is listed as Critically Endangered by the IUCN. Since 2016, populations have collapsed due to a lethal protozoan parasite (Haplosporidium pinnae). More than 99% mortality has been reported in many areas. It is protected under EU law (Habitats Directive, Annex IV) and the Barcelona Convention. Conservation efforts include captive breeding, relocation, and protection of remaining populations in disease-free refuges like the Amvrakikos Gulf (Greece), Mar Menor (Spain), and the Venetian Lagoon (Italy).