The Noble Pen Shell (Pinna nobilis L.)

The Noble Pen Shell (Pinna nobilis L.) in its seagrass habitat (Photo: de Gaulejac & Vicente 1995)
The Noble Pen Shell (Pinna nobilis L.) in its seagrass habitat (Photo: de Gaulejac & Vicente 1995)
Phylum: Mollusca
Class: Bivalvia Linnaeus, 1758
Order: Pterioida Newell, 1965
Family: Pinnidae Leach, 1819
Genus: Pinna Linnaeus, 1758
Species: Pinna nobilis Linnaeus, 1758

The noble pen shell (Pinna nobilis L.) is the largest shellfish living only in the Mediterranean. Its habitat is seagrass of the species Posidonia oceanica (L.) and Cymodocea nodosa (Ucria). The shell prefers more or less closed, protected bays with low water depths up to 40 m. The main factors that characterise the habitat of the Pinna nobilis are good lighting, clean water, low seasonal variations in salinity (3.4 to 4%), moderate temperatures (7 to 28° C) and a uniform, slow flow with enough nutrients.

The shell lives on plankton, which it filters from about 6 litres of water every hour. As a hermaphrodite, it produces male and female germ cells, which it alternately releases in the water from June to August. After fertilisation, free-swimming larvae are developed, which, after a few days and once they have formed a thin calcareous shell, drop to the ocean floor. Now the shell produces the first byssus threads and grows into place. In the first year it reaches a size of 10 to 15 cm, fully grown, the shell can grow up to a size of 120 cm and reach an age of 20 years (de Gaulejac 1995, Vicente 2000, Siletic 2004).
medsea_de2000. (pdf, 540.6 KB)

In the 18th century dense populations are testified to build «cities and villages in the depth of the sea»: «...da wohnen die zahlreichsten Colonien und Familien derselben, welche gleichsam unterirdische Städte und Dörfer ausmachen, darinnen die ältesten Stammväter wie Thürme hervorragen» (Chemnitz 1777). Since the mid-20th century, the populations have broken down. Reasons for the decline are anchoring and over-exploitation by recreational divers and the damage by trawl fishing. On the other hand, the sea grass meadows are threatened by over-fertilisation. An additional nocent effect on the seagrass beds comes through the dissemination of the Caulerpa taxifolia (Vahl), a very invasive algae. Today's populations fluctuate between one of up to 60 specimens per 100 m2. The latter numbers are for the most suitable sites in the southern Adriatic (Mljet National Park, Croatia) or Sardinia. A report by the European Environment Agency in 2000 shows the status and impact on marine and coastal environment of the Mediterranean.

Since 1992 the species Pinna nobilis is under protection in the European Union (EU) and Croatia, officially renewed in 2006 (see pdf-file at the end of the side).

Since the 1980s, the Pinna nobilis and their living conditions and opportunities for the resettlement are being explored around Mediterranean, in Croatia (Zavodnik 1967, Zavodnik et al. 1991, Orepic et al. 1997, Siletic & Perharda 2003, Richardson et al. 2004), in southern France (Vicente 1980, de Gaulejac 1993, de Gaulejac & Vicente 1995), Corsica (de Gaulejac & Vicente 1990), Greece (Catsiki & Catsikiery 1992, Katsanevakis 2006 & 2007), Tunisia (Tlig-Zouari 1993, Rabaoui et al. 2007), Sardinia (Porcheddu et al. 1998, Addis et al. 2009), Spain (Richardson et al. 1999, Templado 2001, García-March et al. 2002, Garcia-March 2003, Garcia-March et al. 2002 & 2005 & 2006 & 2007), Maroc (Guallart 2000) and South Italy (Giacobbe 2002, Centoducati et al. 2007). On the south coast of Turkey, WWF Turkey is working on projects to protect coastal waters. Nevertheless, many populations in the EU continue to be threatened, as the protection of the shell is not implemented or simply ignored

Further sources
: Ravera 1950, Czihak & Dierl 1961, Hignette 1983, Vicente et al. 1990, Vicente & Moreteau 1991, Vicente & de Gaulejac 1993, Butler et al. 1993, Kennedy et al. 2001 (pdf, 551.8 KB)