Murex

• Along with Hexaplex trunculus it was the source of Tyrian purple, the most expensive dye of antiquity: thousands of individuals were needed to dye a single garment, reserved for emperors.
• The pigment is not purple in the animal: it is released colourless and takes on its colour as it oxidises in the light.
• It is one of the reference species for measuring tributyltin pollution, which masculinises the females.
• Tyrian purple came from this snail, the most expensive dye of the ancient world and a symbol of imperial power. The compound is 6,6'-dibromoindigo.
• The secretion from its hypobranchial gland is milky and colourless as it emerges, and only on contact with air and light does it turn into a deep, lasting purple dye.
• It took a staggering number of animals: an estimated 10,000 snails to produce barely an ounce of dye. That explains the price, and why the Phoenicians kept the process secret.
• Together with Hexaplex trunculus and Stramonita haemastoma it makes up the trio of murexes from which the ancients extracted purple.
• In Spain it is the cañaílla, a traditional dish of the Bay of Cádiz, and in Italy it gives its name to scungilli.
• It is known as a fossil from the Pliocene, between 3.6 and 2.6 million years ago.

Habitat & environment

Sandy and muddy bottoms of the Mediterranean and the nearby Atlantic, from 0 to 150 m

Sources consulted: https://es.wikipedia.org/wiki/Bolinus_brandaris