The Sand Collars of The Moon Snail

These strange-looking frilly edged flat spirals made of sand sometimes wash ashore on tropical beaches. They are called sand collars—so called because they are said to resemble an old-fashioned detachable shirt or blouse collar. Sand collars are made by the female moon snails when they lay eggs.

Moon snails, also known as the necklace shells, are a predatory sea mollusks in the family Naticidae. The snails are known for their rather globular-shaped shells and their voracious appetite for other mollusks. When a moon snail finds another snail it wants to eat, it wraps its huge foot around the hapless prey and drills a hole through the victim’s shell using its radula—a tongue like structure— and an acid secretion to soften the shell. Once the shell is bored open, the moon snail proceeds to consume the flesh of the prey.

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Photo credit: Fogonazos

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A sand collar that’s intact still has eggs inside. After the eggs hatch, the collar breaks allowing the newly hatched larvae to escape from their capsules and swim freely towards the open ocean.

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Photo credit: Hans Hillewaert/Wikimedia

A somewhat damaged sand collar of Euspira catena. When the light is shines through the collar, it is possible to make out the individual egg capsules within it.

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Moon snail timelapse.

 

Thanks for sharing Dragon

I live near to the beach so I notice these when the tide goes out. I always wondered what they were, sometimes they appear like little sinkholes on the sea bed. That's neat.