Number of species about 35. In NWE, both families, family Aeolosomatidae and family Potamodrilidae, with a total of 23 species.
Description
Small freshwater polychaetes close, or convergently similar, to oligochaetes. Prostomium without any appendages or eyes; its ventral side ciliated, functioning as locomotory organ. Chaetal bundles beginning from II, usually both dorsal and ventral bundles with hair chaetae, often also with shorter, sigmoid chaetae, seldom lacking. Testes and ovaries present in one and same individual but not arranged as in oligochaetes (testes in preovarian segments). No clitellum; ventral glandular pad surrounding female pore. Differing from oligochaetes in different arrangement of reproductive system, including lack of clitellum; in ventral pharyngeal pad (always dorsal in oligochaetes); and in prostomium modified as locomotory organ. Sharing, with the other polychaetes, nuchal organs represented by sensory pits in Aeolosomatidae. Has been originally treated as a family of most primitive oligochaetes; later on, as a separate subclass of polychaetes, or a separate class of annelids (then named Aphanoneura Vejdovsky, 1884b) but also as a single family, Aeolosomatidae. May be a sister group of Clitellata, according to Purschke et al., 2000.
Gliding or crawling on substratum.
Distribution
Cosmopolitan.
Ecology
In freshwater.
Reproduction
Both sexual and asexual.
Literature
Vejdovsky, 1884b: 16; Bunke, 1967: 189, 335; Van der Land, 1971: 665; Chekanovskaya, 1981: 175; Kasprzak, 1981: 68-69, 87; Purschke et al., 2000: 167-169.