What creates those circular holes on seashells?

At Dalton Koss HQ we are often asked wonderful questions about the coastal and marine environment that we are only too happy to answer.

One question beach lovers often ask us is how are those incredibly circular holes made on the shells? The holes are so perfect, that the shells can be used as a necklace pendant (see image above).

If you recall last week’s Marine Fact, Dalton Koss HQ discussed the difference between carnivore and herbivore marine snails. Leading on from this discussion, the holes you see on these shells are made by carnivore marine snails, or more specifically by their radula.

A radula is similar to our tongue in that it assists the snail to eat. However, unlike a human’s tongue a radula looks and functions like a chainsaw (see image below). The radula is comprised of teeth like structures that have the ability to cut through hard surfaces, such as a calcareous shell. The snail will stay in one place while the radula chainsaws through the shell, hence creating a beautiful concentric circle.

Once the snail breaks through the shell, it will kill and eat the animal inside. Unfortunately, a sad ending for the prey but enabling the carnivore marine snail to survive another day.

The radula is located inside the snails mouth and acts like a chainsaw drilling through tough surfaces. Image sourced from: noaa.gov/ocean

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