(Linnaeus, 1767)
Description
Transparent worms with dorsoventrally flattened body. Prostomium with short protruding lobe on either side of tentacle (lobes can be lacking in the youngest zooids only). Eyes present. Dorsal bundles beginning from VI, with 1-3 stiff hair chaetae, 465-1050 µm long, and 3-4 single-pointed sharp needle chaetae, 75-120 µm long. Ventral chaetae by 4-7, 159-222 µm long, with two angular bends in their proximal half, with upper tooth much longer and strongly curved. In mature individuals penial chaetae by 2, hooked. Length 5.5-18 mm, segment number in zooids 15-35, in single individuals 23-49. In freshwater, common, especially among water plants.
Crawling on substratum. Swimming well.
Distribution
Holarctic; recorded also from South America and (?)Madagascar.
Ecology
In freshwater, very common, especially among water plants. Sometimes swimming in open water. Feeding on detritus and algae collected from substratum.
Reproduction
Mostly asexual, by paratomy (budding). Mature individuals and sexual reproduction rare in spring and summer but common in autumn (in northern Europe).
Literature
Linnaeus, 1767: 1085; Sperber, 1948: 147-149, Fig. 15L, Pl. X, XI; Sperber, 1950: 68, Fig. 17L; Brinkhurst and Jamieson, 1971: 352-353, Fig. 7.11A,C; Chekanovskaya, 1981: 196-198, Figs 78-79; Hrabe, 1981: 52, Pl. 8 Fig. 12-15; Kasprzak, 1981: 107, Figs 257-258.