(Müller, 1774)
Description
Transparent naidids, with contractile caudal branchial disc. Mostly 4 pairs of foliate gills but their number and shape well visible only in undisturbed living individuals. No eyes. Dorsal bundles beginning from VI, usually consisting of one hair chaeta, 240-390 µm long, and one straight needle chaeta, 81-121 µm. In needle chaetae, upper tooth distinctly longer and straighter; small intermediate teeth can be visible under strong magnification. Ventral chaetae of II-V by 3-6, 124-167 µm long, with upper tooth 1.5-2 times as long. From VI on, ventral chaetae by 2-5, shorter (85-125 µm) and more curved, with upper tooth only slightly longer than lower one. Length 5-36 mm, segment number in zooids 12-34, in single individuals 20-105. Described under many different names due to the great variability of branchial apparatus. Distinguishable from its European congeners by the longer upper tooth of dorsal needle chaetae.
Crawling on substratum, able to swim.
Distribution
Cosmopolitan.
Ecology
In freshwater, common. Tolerant of oxygen deficiency. Mostly in the vegetation zone but can occur also deeper, on soft mud bottom in eutrophic lakes. Constructing mucous tubes.
Reproduction
Mostly asexual, by paratomy (budding). Mature individuals and sexual reproduction rare or seasonal.
Literature
Müller, 1774: 22-23; Leidy, 1852: 226-227; Bousfield, 1886: 1098; Michaelsen, 1903b: 182-184, Fig. 3; Sperber, 1948: 165-178, Figs 19A-E, Pl. XIV Figs 2-5, Pl. XV-XVII, XVIII Figs 1-3, 6; Sperber, 1950: 71, Fig. 23B; Brinkhurst and Jamieson, 1971: 365-367, Fig. 7.13D-H; Chekanovskaya, 1981: 211-212, Fig. 89; Hrabe, 1981: 57, Pl. 9 Figs 1-7; Kasprzak, 1981: 112-113, Figs 278-290.