The byssus of Pinna nobilis L.

Fan-shaped traps of the byssus of Pinna nobilis. SEM-photograph, EMPA St. Gallen
Fan-shaped traps of the byssus of Pinna nobilis. SEM-photograph, EMPA St. Gallen
The byssus or beard of the noble pen shell is a bundle of fine, tear-resistant fibres which are formed by the byssus gland in the foot of the shell. The surface is smooth, the diameter of this fibre is comparable to other animal and vegetable fibres. At the moment of formation of fibres, the movable, about 9 cm long foot forms a channel through which the protein secretion of the gland flows. With the toe of the foot the secretion is applied on a suitable location - roots of the seagrass, sand, stones. In contact with the water, the secretion hardens to the byssus fibre.

Unlike other bivalves, such as the blue mussel (Mytilus edulis), the byssus threads of the noble pen shell have no adhesion plates at the end, but fan-shaped traps.


Pinna nobilis with byssus, left: byssus threads with adhesive traps, at the bottom a Pinna guard (Pinnotheres). Poli 1795
Pinna nobilis with byssus, left: byssus threads with adhesive traps, at the bottom a Pinna guard (Pinnotheres). Poli 1795
The silky fibres have a length of up to 20 cm - Basso-Arnoux (1916) notes up to 30 cm. When cleaned, they shine in gold-bronze to olive-coloured tones. This is the raw material from which sea-silk is produced.

First studies of the byssus of Pinna nobilis go back to the early 18th century. In 2002, the Swiss Federal Laboratories for Materials Science and Technology EMPA St. Gallen studied cleaned byssus fibres of Pinna nobilis. Further research followed in 2010. First colouring experiments with genuine purple as well as with chemical dyes have been carried out.

Byssus fibres have also been studied for many years with respect to applications in the technical and medical field. But these studies were always conducted with the easily available byssus of blue mussel (Mytilus edulis), never with the byssus of the noble pen shell (Pinna nobilis L.) (Waite 1983, 1987, 2002)!


Further sources: de Réaumur 1714, Lavini 1835, Müller 1837, Seydel 1909, Pigorini 1922, Ravera 1950, Mercer 1972, Montegut 1999, Maeder & Halbeisen 2002a & 2002b, Jaworski 2010