Bits of beach 'rubber' are left by predatory snails

2 hours ago

James DiamondCornwall

News image — Large amounts of the natural substance has been spotted on Perranporth beach

BBC The photo shows several bits of Moonsnail egg casings washed up on Perranporth beach. The casings lie on the sand in the foreground, with the water in the distance. A headland can be seen on the left of the image, while centrally a small outcrop of rock can be seen. — Large amounts of the natural substance has been spotted on Perranporth beach

Beach goers have expressed concern "chunks of rubber" washing up on beaches are some form of man-made pollutant.

Some believe the bits of circular material which have appeared in large quantities on beaches in Cornwall and Devon are tennis balls, bits of artificial football pitches or even old shoes.

But an expert told the BBC the substance was actually the egg casing created by a moon snail (naticidae), a predatory mollusc which creates the structure during its breeding season.

Matt Slater, from Cornwall Wildlife Trust, said: "It's actually a sort of a mucus structure that gets lots of sand stuck in it and looks kind of like plastic and that's why people have been getting a bit confused."

Dog walker Dan Alderman, 30, said Perranporth beach was covered in the casings and he had been wondering for weeks what the substance was.

"I've just been clueless as to what they are," he said.

"I thought maybe they were like eel skin or something, I don't know or just something off a fish.

"I almost asked Chat GPT today and now, well, now I don't have to."

Wearing a dark green coat with a black dog lead hanging round his neck, dog walker Dan smiles at the camera. He also wears a grey baseball cap, with a light ginger beard and blue eyes. — Dog walker Dan Alderman said he has been confused for weeks about the mystery substance

Another walker, Janet, said she had noticed the bits of material "everywhere".

"It looks like it's bits of plastic of something that's broken up in the surf and just been washed ashore with this heavy surf."

In one post on a Facebook group for Widemouth near Bude, a man said people had spotted "dozens" of the casings in recent weeks.

Perranporth Marine Conservation Group Four grey moon shell casings which look like pieces of grey rubber lying on the sand — The casings are found all over beaches in north Cornwall

What is a moon snail?

Slater said moon or necklance shells were native to the UK. They arelarge round snails, about an inch across, which live on soft sandy seabeds all around Cornwall's coastline.

He said they were a predatory creature which feasted on other molluscs like clams and mussels, using a kind of teeth and enzymes to break through their shells.

"The strange thing is this incredible structure they create to embed their eggs," he said.

"It's actually a sort of a mucus structure that gets lots of sand stuck in it and it looks kind of like plastic and that's why people have been getting a bit confused when they've seen these things.

"It might have been a really good year for this particular species. We often see a few of these washing up after storms, but we've had reports of quite large numbers [this year]."

Getty Images A shiny snail shell lying in a pool of bubbly water on a beach — Moon snails are native to the UK

Moon snails are partial to other molluscs like clams and mussels.

Slater said they drilled a hole through their prey and then used a special acid gland in their foot that releases an enzyme, acids, to weaken the shell.

"Then they scrape away that weakened shell, and it makes a perfect circular hole. It almost looks like it's been drilled.

"Once they've created that hole, they then inject a load more enzymes, dissolving the flesh, turning it into soup, and the little worm just sucks."