Mystery of strange circles in the sand at beach near Plymouth

Objects at Whitsand Bay may look like worn out plastic bottles but the answer is far stranger

The mystery of strange semi-circular objects which have appeared in large numbers on a popular beach near Plymouth has been solved.

They look like worn-down bottle bases in the sand caused by people carelessly disposing of their plastic.

But the items at Whitsand Bay are in fact entirely natural – and a product of the wonderfully-named moon snail.

They are the egg cases, or collars, of the snails, also known as necklace shells.

Geoff Wigham, formerly associate professor of marine biology at the University of Plymouth, said: “Eggs are laid in capsules, many thousands of which are embedded in a collar-shaped mass of jelly, shaped by the animal’s foot and hardened and strengthened by the incorporation of sand grains.”

The video above shows that the cases are solid enough to pick up and handle without crumbling.

But it does not end well for most of the eggs.

Dr Wigham added: “Each individual capsule may contain many eggs, of which most are ‘nurse eggs’ providing sustenance for the one or two that will eventually hatch from each capsule as juvenile snails.

“The collars, or necklaces, are laid on the surface of the sand, their production peaking in spring and early summer, and are often washed higher up the shore by wave action. This is particularly so following periods of rough sea conditions, which appears to be the case here.”

He said the size of the cases seemed to indicate the snails were Euspira catena.

Dr Wigham added: “The common name ‘Necklace Shell’ derives from the appearance of the collar-like egg mass, while ‘Moon Snail’ refers to the semi-lunar shape of the opening of the shell.”

Steve Haywood, who took these pictures last weekend, said: “While enjoying the sun on Whitsand Bay I came across what looked like pieces of plastic! There were thousands of these pieces across the beach, I’ve no idea what they are.”

Plenty of rubbish has been dumped at beaches and beauty spots, including around a bin at the top of the path from Whitsand's Tregantle beach.

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Once Plymouth Live found out the answer, Steve added: “Oh really, wow I’m surprised, I’ve been going to the beach forever and never noticed them before, but glad it’s not anything dangerous.”