Tubificidae is a family of the class Oligochaeta.
Length 0.3-20 cm. Body filamentous, red or pink. Its anterior part (2/3) is usually immersed in the soil (in many species - in a tube of mucus and soil particles), the posterior - free, and makes "respiratory" movements. 35 genera, about 350 species. Widespread everywhere, in fresh, brackish water bodies and seas. In freshwater bodies are found at all depths, in the seas - mainly up to 200 m, in the abyssal - to a depth of 4632 meters. They live in the ground, forming dense settlements, sometimes from thousands of individuals on 1 m2 of the bottom. They feed on organic substances of the soil, carrying it from a depth of 50-100 mm to the bottom surface and mineralizing it. Reproduce by laying cocoons with eggs after mating. Contribute to the biological purification of water. Are the food of fish. Serve as intermediate hosts for some aquatic animal parasites.
The distinctive feature of each of them is the shape of male gonads, their number and position in relation to each other. Tubificidae are hermaphrodites. Tubificidae are herphrodites, feeding on decomposing particles by ingesting and passing sludge through the intestines.