Aquatic Oligochaete Worm

• It reproduces by breaking into pieces: each fragment regrows a new head and tail and becomes a complete individual within a few weeks.
• It is a reference organism in ecotoxicology, and standardised sediment toxicity tests are largely carried out with it.
• It is bred on a large scale as live food for aquarium fish, where it is known as the California blackworm.
• It reproduces almost entirely by fragmentation: it breaks into pieces and each one regrows a head and a tail within days. Almost all populations are clones.
• It has two giant neurons running the length of its body that control two different escape responses: touch the head and it pulls back, touch the tail and it shoots forward. That simplicity has made it a standard model in neurophysiology teaching.
• It breathes through its tail, which it sticks out of the sediment and waves to renew the water; the less oxygen there is, the more it waves.
• It is a standard organism in sediment ecotoxicology: freshwater bioaccumulation tests are run on it.
• It is mass-reared as live food for aquarium fish, where it is known as blackworm.

Skeleton type

Invertebrate - no rigid skeleton (annelid)

Habitat and environment

Muddy and leaf-litter bottoms of ponds, streams and wetlands

Sources consulted: Wikipedia (es): Lumbriculus variegatus · ScienceDirect (Hughes 1989) · Science Advances, How colonial animals evolve · Wikipedia, Zooid