Arenicola

Arenicola is a genus of marine polychaete worms in the family Arenicolidae. Known commonly as lugworms, members of Arenicola are adapted to living in soft sediment and are found in intertidal and shallow subtidal habitats around the world, especially in temperate regions. They have elongated bodies with numerous segments and well-developed setae (chaetae) for digging and anchoring in their burrows. Each species forms U-shaped burrows in mud or sand, often extending deep below the surface, and they produce surface casts of sediment that can be seen as dark threads or mounds.

They feed by depositing sediment at the anterior end of the burrow and extracting organic material as it passes through the digestive system; this deposit-feeding behavior makes them important bioturbators, enhancing sediment oxygenation and nutrient cycling.

Arenicola species are typically dioecious, releasing gametes into the water column for external fertilization; their larval development includes free-swimming trochophore stages before settling as juvenile worms. The common lugworm, Arenicola marina, is one of the best-known species and is widely harvested as bait in recreational and commercial fishing. Other species occur along both Atlantic and Pacific coasts and in various coastal seas.