The Small Five

The lugworm is one of the Wadden Sea’s best known creatures, but it isn’t easy to find. Its hallmark is the piles of sand it makes.

Lugworms are similar to earthworms and have an average lifespan of five years. They live in burrows in the sand of the tidal flats. The burrows are U-shaped and about 30 centimetres deep. By eating the sand of the North Sea tidal flats, they play an important role in the Wadden Sea ecosystem. In fact, every year they eat all the sand in the North Sea tidal flats down to a depth of 25 centimetres – and excrete it again. That’s where the distinctive sand piles come from that can be seen on the seabed at low tide.

The worms’ digestive activity supplies important nutrients to the surface and oxygen to the seabed. During the winter, the lugworm adjusts its body temperature to its surroundings so it needs very little energy and food, and it stays in its burrow where it’s protected from frost and cold.

Cockles live on the bed of the Wadden Sea. Probably the most common mussels in the Wadden Sea, they are heart-shaped when viewed from the side and have rugged, ribbed shells.

They burrow into the mud using a tongue-like foot by pressing the foot into the sand, anchoring it, and then pulling the shell under. The bigger cockles can be easily recognised in small puddles on the tidal flats by the sunlight reflecting off their two siphon openings. The siphon is a short breathing tube through which the cockle takes in seawater; it uses its gills to filter plankton from the water.

The shore crab is widespread along the coast. It has a five-sided carapace and two eyestalks with compound eyes, which can be folded into a depression in the carapace for protection. It can feel and smell with the antennae between its eyes. The shore crab is not caught commercially, but many fish and seabirds prey on it. 

The mud snail is the world’s fastest snail! With help from an air bubble, it can reach the surface of the sea and drift with the current instead of slithering along, enabling it to reach a speed of up to 4 km/h. Mud snails range in colour from dark yellow to brown and are only 7 millimetres across. At first they’re very hard to see. But once you’ve found one, it won’t be the only one: up to 20,000 mud snails can inhabit a square metre. 

Brown shrimp can reach a length of 8 centimetres and have long antennae and eyestalks. They like to bury themselves in the sand and can live for two to five years. At high tide they move onto the tidal flats, and at low tide they can be found in the tidal creeks.

Brown shrimp are a popular delicacy along the North Sea coast. How about shelling a few shrimp yourself?