Müller, 1774
Description
Transparent worms but anterior end often pigmented. Eyes usually present. Dorsal bundles beginning from VI, consisting of 1-4 hair chaetae, 90-305 µm long, and 1-4 needle chaetae, 58-100 µm long, with long parallel teeth. All ventral bundles consisting of 2-5 similar chaetae, 70-112 µm long, with upper tooth twice as long and strongly curved in its distal end, lower tooth forming a right angle with the longitudinal axis of chaeta. In mature individuals hooked penial chaetae, 2-4 per bundle. Stomachal dilatation gradual. Length 2.2-12 mm, segment number in zooids 12-21, in single individuals 15-40. The species is easy to recognize by its uniform ventral crotchets with much longer upper teeth, and characteristic shape of needles. However, in older literature, before the revision by Piguet, 1906a, most species of Nais were treated under this name.
Crawling on sediment. Able to swim.
Distribution
Cosmopolitan.
Ecology
In freshwater, often in extreme conditions (cold springs, heavily polluted streams), as well as in brackish water. Usually lacking or rare in habitats rich in other species of Nais.
Reproduction
Mostly asexual, by paratomy (budding). Mature individuals and sexual reproduction rare or seasonal.
Literature
Müller, 1774: 22 (partim); Sperber, 1948: 127-130, Fig. 14A-C, Pl. IX Figs 1-3; Sperber, 1950: 64, Fig. 15; Brinkhurst and Jamieson, 1971: 336-337, Fig. 7.6M-P; Chekanovskaya, 1981: 230-231, Fig. 101; Hrabe, 1981: 39, Pl. 4 Figs 1-5; Kasprzak, 1981: 128, Figs 375-380.