(Müller, 1774)
Description
Medium-sized to large, usually dark brown or reddish brown worms. Body cylindrical, prostomium bluntly conical, often inflated. Body wall with dark green pigment in forebody. In each postclitellar segment, a pair of blind, branching transversal blood vessels covered with dark chloragogen cells. As a result, live worms often assume a transversally striped appearance. Chaetae two per bundle, sigmoid, with distal nodulus, 120-220 µm long, with smaller but well distinguished upper tooth diverging at an angle of about 300. When mature, male pores and beginning of clitellum (also testes) usually in VIII but sometimes also further rearward. Male pores surrounded by concentric ridges of body wall. Atria cylindrical, their efferent ducts with double bend. Penis formed of bundle of thin extended epithelial cells. Usually several pairs of spermathecae in postclitellar segments, with roundish ampullae and thin ducts, opening dorsolaterally. Number, position and shape of different reproductive organs very variable. Length 40-90 mm, segment number 140-300, but individuals regenerating one or both ends are often shorter. Easy to distinguish from the other lumbriculids in NWE, by its diverging upper tooth in chaetae. There exist a number of variants of reproductive system in the genus, even within one population, since sexual organs have lost their evolutional value and hence the control of natural selection. In some regions of North America and East Asia, similar variants may be genetically stable, and have been described as separate subspecies, species, or even genera. None of them has been reliably recorded from NWE.
Burrowing in sediment, crawling fast on the substratum. Able to swim short distances when irritated.
Distribution
Holarctic, introduced in some countries on the Southern Hemisphere.
Ecology
In freshwater, particularly among macrovegetation. Tolerant of low pH; occurring even in peat bogs and temporary pools. Able to form desiccation-resistant cysts.
Reproduction
Asexual reproduction by architomy (fragmentation) prevailing. Disintegrates easily when caught. Mature individuals very rare.
Literature
Müller, 1774: 26; Mrázek, 1906: 381-461, Figs A-V; Cook, 1971a: 204-206, Figs 5.1B, 5.3A-C; Chekanovskaya, 1981: 412-414, Fig. 206; Hrabe, 1981: 111-112, Pl. 19, Figs 13-17; Kasprzak, 1981: 207-208, Figs 833-837; Timm et al., 1997: 24, Fig. 5.