Blue mussel

The blue mussel is a small shellfish with a smooth, blue-black shell shaped a little like a teardrop. It lives along busy, splashy seashores, clinging to rocks, piers, and ropes where the waves roll in and out. Inside its two shells, the soft animal stays safe and cosy, opening up just a little when it is time to eat.

Blue mussels have a clever trick for holding on. Using a small, stretchy body part called a foot, a mussel spins strong threads called byssus, which set as hard as tough little ropes. These silk-like threads glue the mussel firmly to the rocks, so even when powerful waves crash over it again and again, the mussel stays right where it wants to be.

A blue mussel eats by filtering the water. It draws seawater in through its shell, then combs out tiny drifting specks of food, such as plankton, and swallows them up. As it feeds, it also traps bits of dirt and cloudy stuff floating in the sea. In this way, a bed of mussels quietly helps keep the water around them clearer and cleaner.

Mussels love company. They live packed close together in huge groups called mussel beds, all anchored side by side by their byssus threads. These crowded beds become little seaside towns, giving shelter and safety to crabs, small fish, and other tiny creatures that hide among the shells. A mussel is never lonely on a busy shore.

Blue mussels are found on cool, rocky coasts on both sides of the North Atlantic, around Europe and North America. They have not been given an official rating on the IUCN Red List, but they are common and important animals of the seashore, filtering the water and building homes for their neighbours, day after day.