Description: This lugworm is usually seen through presence of its distinctive burrows in sand. They burrow in sand or muddy sand and deposit a thin, neat worm cast which has the appearance of a neatly coiled tube of sand which is excreted by the worm as it burrows. There is no depression as in Arenicola marina, but a small hole may be visible within the cast itself. The worm has a firm cylindrical body 12-20 cm in length, with annulations, and is usually dark green, red-brown to black in colour. The head is small and blunt and lacks appendages aside from a rough proboscis. The first three chaetigers have the body ring formula 2-2-4, which is an important way to distinguish from Arenicola marina (which has 2-2-3).

Habitat: Burrows in sand or muddy sand. Found intertidally, but usually near low water mark, or subtidal.

Distribution: Scattered records around Britain and Ireland, not as commonly recorded as Arenicola marina.

Similar Species: Could be confused with the blow lugworm Arenicola marina.

Key Identification Features:

• Thin, neat worm cast often visible on surface.
• Dark colouration.
• Firm, annulated cylindrical body 12-20 cm.
• Number of body rings on first 3 chaetgers - body ring formula of 2-2-4.

Distribution Map from NBN: Arenicola defodiens at National Biodiversity Network mapping facility, data for UK.

iNaturalist: Arenicola defodiens at iNaturalist World Species Observations database.

WoRMS: Arenicola defodiens at World Register of Marine Species.