On a recent holiday around the Scottish coast I was struck by the huge difference in colours of the different shells, especially the limpets.

I had assumed that a limpet is simply a limpet with differently coloured shells but there are many different aquatic snails with conical shell shapes.They are known as ‘patellidae’ meaning dish shaped .

We usually come across the empty shell but their anatomy and locomotion is amazing. Next time you foolishly try and prise one from a rock think of this: The large strong muscular foot by which they move called the tongue or radula is composed of the toughest biological material ever tested which is why it is so difficult to shift them. Oystercatchers seem to be their only natural predator presumably because they peck through the shell?

This rough tough tongue can shift the limpet up to 3 feet away in search of food - plant material and algae which they scrape off the rock, and small barnacles. They only move and feed when covered by water and have fine hairs at the roof of the mouth which conveys food to the gut. After feeding they always return to home base where a depression is created known as the ‘home scar’.

They have all the usual organs of molluscs including a nervous system, a head or snout containing an optical nerve with eye spots. They do not receive images but merely get a sense of light and dark. A heart pumps blood which is aerated using gills situated around the shell edge and they have 2 kidneys, one of which often covers the whole body in a thin, almost invisible layer.

Unlike many species we are familiar with who breed in Spring, for limpets it is Autumn when they shed eggs into the sea. The larvae hatch within 24 hours and they develop a shell within 10 days.

My initial question to self regarding colour differences has not been answered except that maybe it is safe to assume that shell colour has some connection with camouflage and the colour of the rocks?

But rocks are a whole other area of beach combing and what you chose to do with the stones and shells and bits of this and that which you may pick up on holiday. Personally I have a whole section of the garden devoted to ‘unusual stones and things’ and the shells from around the world find a place on shelves and in plant pots! Very satisfying it is too!