Great scallop

The great scallop is a shellfish with a beautiful fan-shaped shell, the kind you might spot on a beach or on old paintings and postcards. It lives on sandy and gravelly seabeds in the cool waters around Europe. Its two curved shells, called valves, fit together like a case, keeping the soft animal safely tucked inside.

Here is a wonderful surprise: a scallop can swim! Most of the time it lies quietly in a little hollow in the sand, but if it needs to move, it claps its two shells together again and again. Each clap squirts out jets of water, and the scallop goes zipping along through the sea with the curved edge of its shell leading the way. It looks a bit like a chattering pair of castanets bouncing off across the seabed.

Even more amazing, the great scallop has eyes — lots of them! Along the edge of its shell sit rows of tiny eyes, around 30 to 36 of them, glinting blue or green like little jewels. These eyes cannot see clear pictures, but they can spot shadows and movement. If something creeps too close, the scallop senses it and claps away to safety.

The great scallop is a filter feeder. It gently draws seawater in over its gills and sieves out tiny drifting specks of food, such as plankton, that are far too small for us to see. By quietly filtering the water all day, it feeds itself without ever needing to chase or hunt a single thing.

Great scallops live across the north-eastern Atlantic, from Norway down past the British Isles to Spain and beyond. Where they are left undisturbed, they can live for more than 20 years and grow shells about 15 centimetres across. They have not been given an official rating on the IUCN Red List, but these clever, swimming shellfish remain a familiar sight on the seabed.