''Pinna nobilis'', known by the

common names In biology, a common name of a taxon or organism (also known as a vernacular name, English name, colloquial name, country name, popular name, or farmer's name) is a name that is based on the normal language of everyday life; and is often contras ...

noble pen shell and fan mussel, is a large

species A species () is often defined as the largest group of organisms in which any two individuals of the appropriate sexes or mating types can produce fertile offspring, typically by sexual reproduction. It is the basic unit of Taxonomy (biology), ...

Mediterranean The Mediterranean Sea ( ) is a sea connected to the Atlantic Ocean, surrounded by the Mediterranean basin and almost completely enclosed by land: on the east by the Levant in West Asia, on the north by Anatolia in West Asia and Southern ...

clam, a marine

bivalve Bivalvia () or bivalves, in previous centuries referred to as the Lamellibranchiata and Pelecypoda, is a class (biology), class of aquatic animal, aquatic molluscs (marine and freshwater) that have laterally compressed soft bodies enclosed b ...

mollusc Mollusca is a phylum of protostome, protostomic invertebrate animals, whose members are known as molluscs or mollusks (). Around 76,000 extant taxon, extant species of molluscs are recognized, making it the second-largest animal phylum ...

in the family Pinnidae, the pen shells.*''Pinna gigas'' Chemnitz It reaches up to of shell length.Zavodnik, D., Hrs-Brenko, M., & Legac, M. (1991). Synopsis of the fan shell ''P. nobilis'' L. in the eastern Adriatic sea. In the C. F. Boudouresque, M. Avon, & V. Gravez (Eds.), ''Les Especes Marines a Proteger en Mediterranee'' (pp. 169–178). Marseille, France: GIS Posidonie publ. It produces a rare

manganese Manganese is a chemical element; it has Symbol (chemistry), symbol Mn and atomic number 25. It is a hard, brittle, silvery metal, often found in minerals in combination with iron. Manganese was first isolated in the 1770s. It is a transition m ...

-containing porphyrin protein known as pinnaglobin.

Description

The

shell is usually long, but can reach . Its shape differs depending on the region it inhabits. Like all pen shells, it is relatively fragile to pollution and shell damage. It attaches itself to rocks using a strong

byssus A byssus () is a bundle of filaments secreted by many species of bivalve mollusc that function to attach the mollusc to a solid surface. Species from several families of clams have a byssus, including pen shells ( Pinnidae), true mussels (Mytili ...

composed of many silk-like threads which used to be made into cloth. The animal secretes these fibres from its byssus gland; they consist of

keratin Keratin () is one of a family of structural fibrous proteins also known as ''scleroproteins''. It is the key structural material making up Scale (anatomy), scales, hair, Nail (anatomy), nails, feathers, horn (anatomy), horns, claws, Hoof, hoove ...

and other proteins and may be as long as . The inside of the shell is lined with brilliant mother-of-pearl. As with other members of its genus, ''Pinna nobilis'' hosts symbiotic

crustacean Crustaceans (from Latin meaning: "those with shells" or "crusted ones") are invertebrate animals that constitute one group of arthropods that are traditionally a part of the subphylum Crustacea (), a large, diverse group of mainly aquatic arthrop ...

s which live inside its shell; in this case it is the

shrimp A shrimp (: shrimp (American English, US) or shrimps (British English, UK)) is a crustacean with an elongated body and a primarily Aquatic locomotion, swimming mode of locomotion – typically Decapods belonging to the Caridea or Dendrobranchi ...

'' Pontonia pinnophylax'' and the

pea crab The pea crab, ''Pinnotheres pisum'', is a small crab in the family Pinnotheridae that lives as a parasite in oysters, clams, mussels, and other species of bivalves. Etymology ''Pinnotheres'' is Greek for "guard of '' Pinna''" and ''pisum'' i ...

'' Nepinnotheres pinnotheres''. It is believed that when it sees a threat, the shrimp warns the host, perhaps by retracting its claws or even by pinching. The clam then closes shut. It has been demonstrated that the shrimp has a similar filter-feeding diet to its host and the relationship is likely mutualistic.

Right and left valve of the same specimen: Pinna nobilis 001.jpg, Right valve Pinna nobilis 002.jpg, Left valve

Distribution

This species is

endemic Endemism is the state of a species being found only in a single defined geographic location, such as an island, state, nation, country or other defined zone; organisms that are indigenous to a place are not endemic to it if they are also foun ...

to the

Mediterranean Sea The Mediterranean Sea ( ) is a sea connected to the Atlantic Ocean, surrounded by the Mediterranean basin and almost completely enclosed by land: on the east by the Levant in West Asia, on the north by Anatolia in West Asia and Southern Eur ...

, where it lives offshore at depths ranging between . It could be found buried beneath soft-sediment areas (fine sand, mud, often

anoxic Anoxia means a total depletion in the level of oxygen, an extreme form of hypoxia or "low oxygen". The terms anoxia and hypoxia are used in various contexts: * Anoxic waters, sea water, fresh water or groundwater that are depleted of dissolved ox ...

Human relevance

This species is the origin of sea silk, which was made from the

of the animal.Hill, John E. (2009) ''Through the Jade Gate to Rome: A Study of the Silk Routes during the Later Han Dynasty, 1st to 2nd centuries CE''. John E. Hill. BookSurge, Charleston, South Carolina. . See Section 12 plus "Appendix B – Sea Silk". pp. 468–476.

Threats

In 2016, an outbreak of one disease caused the mortality of 99% of its population in Spain. The cause of the disease was a newly discovered

pathogen In biology, a pathogen (, "suffering", "passion" and , "producer of"), in the oldest and broadest sense, is any organism or agent that can produce disease. A pathogen may also be referred to as an infectious agent, or simply a Germ theory of d ...

, '' Haplosporidium pinnae'', which still poses a serious threat to the survival of the species. By 2019, mortality spots had been detected in

Greece Greece, officially the Hellenic Republic, is a country in Southeast Europe. Located on the southern tip of the Balkan peninsula, it shares land borders with Albania to the northwest, North Macedonia and Bulgaria to the north, and Turkey to th ...

Croatia Croatia, officially the Republic of Croatia, is a country in Central Europe, Central and Southeast Europe, on the coast of the Adriatic Sea. It borders Slovenia to the northwest, Hungary to the northeast, Serbia to the east, Bosnia and Herze ...

Turkey Turkey, officially the Republic of Türkiye, is a country mainly located in Anatolia in West Asia, with a relatively small part called East Thrace in Southeast Europe. It borders the Black Sea to the north; Georgia (country), Georgia, Armen ...

Tunisia Tunisia, officially the Republic of Tunisia, is a country in the Maghreb region of North Africa. It is bordered by Algeria to the west and southwest, Libya to the southeast, and the Mediterranean Sea to the north and east. Tunisia also shares m ...

France France, officially the French Republic, is a country located primarily in Western Europe. Overseas France, Its overseas regions and territories include French Guiana in South America, Saint Pierre and Miquelon in the Atlantic Ocean#North Atlan ...

and

Morocco Morocco, officially the Kingdom of Morocco, is a country in the Maghreb region of North Africa. It has coastlines on the Mediterranean Sea to the north and the Atlantic Ocean to the west, and has land borders with Algeria to Algeria–Morocc ...

. In the

Trieste Trieste ( , ; ) is a city and seaport in northeastern Italy. It is the capital and largest city of the Regions of Italy#Autonomous regions with special statute, autonomous region of Friuli-Venezia Giulia, as well as of the Province of Trieste, ...

area, considerable efforts have also been made to conserve the deposits since 2020. In the past, ''Pinna nobilis'' faced extinction, due in part to fishing, incidental killing by trawling and anchoring, and the decline in

seagrass Seagrasses are the only flowering plants which grow in marine (ocean), marine environments. There are about 60 species of fully marine seagrasses which belong to four Family (biology), families (Posidoniaceae, Zosteraceae, Hydrocharitaceae and ...

fields; pollution kills eggs, larvae, and adult mussels. Such threats, however, have been very localised and have not led to such a widespread and rapid population decline. The pathogen, which is still present in the environment, will make recovery a challenge, so continuing declines are expected. The percentage of population size reduction over the last ten years is over 80%. In December 2019, ''Pinna nobilis'' has entered the

IUCN Red List The International Union for Conservation of Nature (IUCN) Red List of Threatened Species, also known as the IUCN Red List or Red Data Book, founded in 1964, is an inventory of the global conservation status and extinction risk of biological ...

critically endangered An IUCN Red List critically endangered (CR or sometimes CE) species is one that has been categorized by the International Union for Conservation of Nature as facing an extremely high risk of extinction in the wild. As of December 2023, of t ...

. The noble pen shell has been listed as an endangered species in the Mediterranean Sea. The European Council Habitats Directive 92/43/EEC, on conservation of natural habitats and the wild fauna and flora, proclaims that ''P. nobilis'' is strictly protected (by the Annex IV of EEC, 1992) – all forms of deliberate capture or killing of fan mussel specimens are prohibited by law.Centoducati, G., Tarsitano, E., Bottalico, A., Marvulli, M., Lai, O., Crescenzo, G. (2006). Monitoring of the Endangered ''Pinna nobilis'' Linee, 1758 in the Mar Grande of Taranto (Ionian Sea, Italy). In the ''Environ Monit Assess'' (2007) 131:339–347. As part of the ''Costa Concordia'' disaster recovery effort in Italy in 2012, a group of about 200 ''Pinna nobilis'' was relocated to a nearby area due to the threat posed by subsequent engineering work. The

of '' Atrina pectinata'', a shell of the same family, has been used in

Sardinia Sardinia ( ; ; ) is the Mediterranean islands#By area, second-largest island in the Mediterranean Sea, after Sicily, and one of the Regions of Italy, twenty regions of Italy. It is located west of the Italian Peninsula, north of Tunisia an ...

as a substitute for ''Pinna nobilis'', to weave sea silk.

Protection and extinction

''Pinna nobilis'' is sensitive to exceptional pollution. Many die due to anchoring; additionally, illegal extraction, which has been prohibited in Croatia since 1977, is still present. It has been placed on the list of strictly protected species in Croatia. Any extraction of ''P. nobilis'' out of the sea is heavily fined.

Gallery

File:Pinna nobilis.jpg, Live specimen of ''P. nobilis'', looking into the shell from above File:Pinna noblis shell & byssus.JPG, ''Pinna nobilis'': shell and byssus File:Fine sea silk threads.JPG, The very fine

threads of ''P. nobilis'' File:Pinna nobilis PN.jpg, Shell of ''Pinna nobilis'' File:Pinna nobilis DSC 0186.jpg, Releasing male gametes, Pula, Croatia File:Pinna nobilis DSC 0006.jpg, '' Marthasterias glacialis'' attack, Pula, Croatia

References

External links

Images of shells
* {{Taxonbar, from=Q536444 Pinnidae Molluscs described in 1758 Taxa named by Carl Linnaeus Molluscs of the Mediterranean Sea