The Noble Pen Shell, Pinna Nobilis, is a species of large saltwater clam, a marine bivalve mollusk belonging to the family Pinnidae.
This bivalve shell can be as large as almost 3 feet in length, and the shape is somewhat variable. Like all pen shells, it is quite fragile. It attaches itself to rocks using a strong byssus made up of many silk like hairs. These are fibers that are secreted by the animal. Brilliant mother of pearl lines the inside of the shell.
This species is native to the Mediterranean Sea, where it resides offshore down to a depth of 20 meters.
It’s the origin of sea silk, which was made from the byssus of the animal. Unfortunately, in recent years, Pinna nobilis has become threatened with extinction, partially because of overfishing, the fact that the soft parts are edible, and also because of the decline in seagrass fields, and the increasing pollution.
Image Caption: Live specimen of Pinna nobilis, in Levanto, Liguria. Credit: Hectonichus/Wikipedia (CC BY-SA 3.0)