Kasprzak, 1973
Description
Transparent worms, anterior end often pigmented. Eyes present. Dorsal bundles beginning from VI. Hair chaetae 1-2 per bundle, 214-330 µm long; needle chaetae by 1-2, 72-75 µm long, very finely bifid. Ventral chaetae by 2-4, in II-V 112-127 µm long, with equally thin teeth but upper tooth 1.5-2 as long. Basal portions of teeth of ventral chaetae in II-V parallel; lower tooth forming an acute angle with the longitudinal axis of chaeta. From VI on, ventral chaetae shorter (85-110 µm), much thicker (up to 4-5 µm) and more curved, with lower tooth several times as thick as upper one. In mature individuals, hooked penial chaetae by 2-3. Stomachal dilatation abrupt. Length 5-8 mm, segment number in zooids 16-23, in single individuals ~29. Can be (and evidently has been) confused with Nais variabilis. Differing from this species in having long parallel teeth of anterior crotchets (II-V), contrasting very sharply with the shape of posterior ones (from VI).
Crawling on substratum. Able to swim.
Distribution
Europe.
Ecology
In freshwater.
Reproduction
Mostly asexual, by paratomy (budding). Mature individuals and sexual reproduction rare or seasonal.
Literature
Kasprzak, 1973: 535-539, Figs 1-4; Kasprzak, 1981: 126-127, Figs 355-364; Hrabe, 1981: 41-42, Pl. 4 Figs 16-21; Giani et al., 2001: 65-74.