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Noble Pen Shell

About

The noble pen shell (Pinna nobilis) is one of the largest bivalve molluscs in the Mediterranean and can reach an impressive size, exceeding 100 centimetres in length. It resembles a giant mussel in some ways, but its defining feature is its long, triangular shell, usually half-buried in the sandy or muddy seabed.

Pen shells typically live in seagrass meadows, especially in areas with Posidonia, where they stay fixed in the seabed and filter seawater to feed.

One of their most striking features is the byssus, a set of very fine fibres with which they anchor themselves to the seabed. Historically, these fibres were used to produce an extremely fine and rare material known as "sea silk".

A valuable but vulnerable species

The pen shell is particularly important for the marine ecosystem, but in recent years its populations in the Mediterranean have suffered a dramatic decline due to a major epidemic that has struck the species.

For this reason, if we come across a pen shell in the sea, we do not touch it and do not try to pry it loose from the seabed. We observe it from a distance and let it continue its role in the marine ecosystem.

Fun fact: the pen shell is not just "a giant mussel". It is one of the most distinctive and impressive bivalves of the Mediterranean and can be a real little treasure for anyone exploring the seabed of our area.