Monday 31 August 2015

File Shell

Image: Ria Tan
Tentacles. They are the crowning glory of Mollusca. Cephalopods like octopuses and squid are clearly the anointed kings and queens of this tentacle-blessed race. Just look into their large, intelligent eyes and you know they're asking one thing: where are your tentacles, peasant?

Even Gastropods like slugs and snails have a few tentacles, sometimes with eyes on top. And when you look into those beady, little peepers they're like: who said that? because they all need glasses or miniature telescopes or something to see anything.

Image: Patrick Randall
But what about the bivalves? What about those poor clams and mussels? Can there be any wonder that they spend their entire lives hidden in their shells, often underground or rammed into some benighted, rocky niche, when they have scarcely a single tentacle between them? The shame. The terrible shame!

Never fear...

Image: prilfish
File Shells are here!

File Shells are a family of over 100 species of clam in the Limidae family. They're found all over the world in marine waters, from the shallows to the deeps.

We've seen one before. The famous Disco Clam or Flame Scallop who startles the eye with a flash of electric blue along the lip of its deep red mantle. But there are many more, and what they share in common is not a flash of electric blue, but tentacles.

Image: Ria Tan
Tentacles galore! So many tentacles that a lot of File Shells can't fully close their shell. No great sacrifice when you get TENTACLES in return! And such bright and beautiful ones, too. Gorgeous red and orange colours are common among File Shells. The actual shell it's all coming out of is sometimes lost among all those luxurious limbs.

File Shells live on the ground, often hidden in rocky crevices where they can peacefully open their shell to filter out food and oxygen from the water. If they grow displeased of the area, like if a Disco Clam moves in next door and hosts loud parties all night or someone like me comes along and keeps on pointing at their tentacles, File Clams can make a reasonably swift getaway.

They can sort of swim! Or crawl? Opening and closing their shell pushes them forward with a squirt of water while their tentacles keep them propped upright. They end up looking like one of those fluffy caterpillars! The tentacles are also sticky and readily fall off and wriggle around to distract predators while the rest of the clam escapes. Tentacles are heroic like that.

Some File Shells would really prefer not to go gallivanting around the sea. They'd much rather stay in one place, so much so that they build a kind of nest around themselves. It's made out of a material called byssus. The File Shell secretes this stuff as sticky threads but they soon harden so the clam can maintain a firm foothold on the rocky ground.

Video: ScotNaturalHeritage1
How is that not an orange mouth, orange lips, orange tongue and orange beard?

That's one File Shell safe in its nest. But what happens if you get two of them close together. What about 100? 100 MILLION?

We've all heard of coral reefs. But what about clam reefs? In 2012 an enormous colony of some 100 million Flame Shells (Limaria hians) was discovered off the coast of the Isle of Skye in north-west Scotland. Their nests of byssus had grown to become a thick, velvety carpet that proved to be the perfect home for algae, worms, crabs and all sorts of other invertebrates.

Image: Goatchurch
Flame Shells themselves get their name from their bright orange tentacles. There aren't many bright orange things in Skye so hopefully 100 million Flame Shells is enough to keep the people there warm over the winter.

And aren't those Flame Shells living the dream? To camp out under the Hebridean stars (clouds) with 100 million friends. To sleep on beds created from our own bodies and which serve as habitat to thousands of tiny creatures. Ah... doesn't the rustling of life beneath your pillow bring the sweetest dreams?


elfinelvin said...

They certainly are a showy group! Incredible that there are 75 hectares of them in Loch Alsh. We're so used to seeing bland coloring in cold waters, good to have some bright color for a change.

Crunchy said...

They look chewy.

Joseph JG said...

@elfinelvin: Fields of orange tentacles in Scotland. So bizarre!

@Crunchy: I think that's blasphemy in some circles.