Bighead sludgeworms

There are two groups of polychaetes that, in shape, closely resemble familiar terrestrial earthworms (oligochaetes): bighead sludgeworms (Family Capitellidae, represented by the following species) and marine earthworms (Family Lumbrineridae, p. 131). They are all active burrowers. Bighead sludgeworms are opportunistic, often thriving in soft, organically enriched sediments or even black anoxic (low-oxygen) mud. Like their close relatives, bighead sludgeworms are a major component of the unseen benthic “labour force,” bioturbating (ingesting, mixing and aerating) the sediments.