What Are Lugworm Casts?

The lugworm or sandworm (Arenicola marina) is a large marine worm of the phylum Annelida. Its coiled castings are a familiar sight on a beach at low tide but the animal itself is rarely seen except by those who, from curiosity or to use as fishing bait, dig the worm out of the sand.

What do lugworms do?

Lugworms feed on organic material such as micro-organisms and detritus present in the sediment. They ingest the sediment while in the burrow, leaving a depression on the surface sand. Once the sediment is stripped of its useful organic content it is expelled, producing the characteristic worm cast (see photo #3 above).

How do lugworms make casts?

Lugworms live in burrows in the sand both on the beach and in the sandy seabed. Their burrows are u-shaped and are formed by the lugworm swallowing sand and then pooing it out, creating wiggly piles of sand along the shoreline. These are known as casts.