D'Udekem, 1855
Description
Transparent naidids with caudal branchial disc. Mostly 3 pairs of short, contractile gills, those of the first (dorsal) pair foliate or reduced, the subsequent ones finger-like, the last pair reaching to end of disc. No eyes. Dorsal bundles beginning from VI, consisting mostly of one hair chaeta, 95-185 µm long, and 1-2 needle chaetae, 42-75 µm long. Both teeth of needle chaetae equally short. Ventral chaetae of II-V by 2-6, 63-123 µm long, slender, with upper tooth twice as long. From VI on, ventral chaetae by 3-6, much shorter (51-82 µm), thicker and curved; their teeth at first of equal length but upper tooth shorter rearward. Length 5-19 mm, segment number in zooids 18-29, in single individuals 21-35. Dero obtusa differs from the related Dero nivea, bearing similar chaetae, in its shorter branchial disc, covered by gills up to the posterior edge.
Crawling on substratum. Able to swim.
Distribution
Almost cosmopolitan.
Ecology
In freshwater, common. Constructing mucous tubes.
Reproduction
Mostly asexual, by paratomy (budding). Mature individuals and sexual reproduction rare or seasonal.
Literature
D'Udekem, 1855: 549-550, Pl. Fig. 1; Bousfield, 1886: 1098; Sperber, 1948: 180-184, Figs 19F, 20A, Pl. XVIII Fig. 5; Sperber, 1950: 71, Fig. 23C; Brinkhurst and Jamieson, 1971: 369-370, Fig. 7.14F-I; Chekanovskaya, 1981: 214-215, Fig. 91; Hrabe, 1981: 59, Pl. 9 Fig. 8; Kasprzak, 1981: 113-114, Figs. 219-296.