ringmaskarna

Ringmaskarna, or polychaete worms, are a diverse group of segmented marine annelids. In Swedish usage they are called ringmaskarna. They occur worldwide in habitats from shallow coastal waters to the deep sea and include burrowers, tube-dwellers, and free-living species. The body is elongated and segmented, with numerous chaetae (bristles) on paired appendages (parapodia). The head, including the prostomium and peristomium, bears sensory structures; many species show conspicuous ring-like annulations that give rise to the name.

Ecologically, ringmaskarna are important in benthic ecosystems. They contribute to sediment mixing (bioturbation), influence nutrient cycling, and serve as predators, detritivores, or filter feeders depending on the species. Many have a trochophore larva, enabling dispersal, while tube-dwelling forms secrete protective tubes.

Reproduction varies; most species reproduce sexually with external fertilization, while some brood eggs in tubes or carry them on the body. Larval development includes free-swimming stages before settlement. Growth rates and lifespans vary widely.

Humans interact with ringmaskarna in several ways. They are widely used as fishing bait and are monitored in ecotoxicology as indicators of sediment quality. Some species have been introduced outside their native range through shipping or ballast water, potentially affecting local communities.

Conservation status for ringmaskarna as a group is generally not of concern, but local populations can decline due to pollution, habitat loss, and bottom-trawling.