Noble Sea Pen

Image: riandreu
Pinna nobilis

Forget blood from a stone. Try silk from a tooth...

It's the Noble Sea Pen, a magnificent clam found only in the Mediterranean Sea. Over the course of a 25 year lifespan it can reach a height of 90 or 120 cm (3 or 4 feet)!

Image: Giuseppe Romano

It looks like an enormous tooth.

An ENORMOUS tooth.

The biggest predatory tooth known thus far belonged to a whale thought to prey on other whales. Its teeth were 36 cm (14 in) long, about a third of the Noble Sea Pen. Were it really a tooth, its owner would probably have to feed on entire habitats and nation states.

Image: Andreas Hoffmann

The inside of the shell is covered in a layer of nacre on the pointy end, but you'd have to do mean and destructive things to see that. The Noble Sea Pen would rather you didn't.

They would much prefer to stand tall and proud, half-buried in the soft sand of the seabed. Now they can open up their shell to filter out delicious plankton from the sea. It's said they can process up to 6 litres of water every hour!

Image: Arnaud Abadie

It all looks rather precarious, really. This tall, slim fan-shaped thing on the sea floor. They'll need a sturdy grip to keep from falling over, won't they?

Video: Daniele Tartarini

Don't worry, the Noble Sea Pen has that covered. In common with certain other bivalves, they come armed with a gland that secretes a fluid which hardens into a collection of threads known as the byssus. It's with this that they secure their foothold on the ocean floor.

Image: John Hill
Incredibly fine threads of the byssus

In the case of the Noble Sea Pen, the byssus is made up of over 20,000 exceedingly fine, silky threads that glisten with a lovely golden sheen. It's an uncommonly luxurious byssus, appropriate for a Noble. Each thread is up to 25 cm (10 in) long and with a bit of work, can be turned into a fabric called sea silk.

Image: Topyti
A few people still make sea silk today!

People have produced sea silk for thousands of years. Byssus cloth is mentioned on the Rosetta Stone, which dates back to 196 BC. Byssus cloth was used to pay taxes back then! It was also popular and extremely expensive among the Greeks and Romans.

The Arabs and Chinese also imported the stuff in the early centuries AD. I guess they didn't have documentaries back then because stories spread that suggested sea silk came from some kind of aquatic, sheep creature.

Image: John Hill
Sea silk glove

It sounds pretty ludicrous, but then so does making a pair of gloves out of a clam. And honestly, if most of us tried to explain where the twitter feed updates on a smartphone come from, we'd fall into a world of myth and magic pretty quick, too.