How old is this shell?

Having a close look at a shell can sometimes tell you a lot about its history.

Some shells can tell you how old the mollusc inside had been alive, for example. Common cockles are some of the best shells to see this on - so these are pictured here.

While cockles have ridges running from their narrowest point, to their widest, it is sometimes also possible to see indented lines running across the width of the shell (and these are replicated exactly on each half of the shell).

The theory is that each line across represents one growing season, rather like the growth rings of tree trunks.

READ MORE: How to identify shells

The two deep lines across the shell above indicate that the cockle lived through two birthdays but dies before the third.

Rings may be a better indication of age than the size of the shell, as the above photo shows. A bigger shell does not neceassarily mean that the molusc lived a longer life.

While the shells above are very different sizes, the growth ring suggests that they are both around the same age - somewhere between one and two years old. Perhaps the larger shell on the right lived in an area where more food was available enabling it to grow bigger.

To be scientifically accurate, the best way to age a shell would be to saw through it to get a cross section and look at the internal growth rings. This is, however, a very tricky operation requiring specialist equipment.

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