(Orsted, 1842)
Description
Smooth transparent worms. Pigment spots can occur on dorsal side of forebody. Prostomium usually much thinner than body segments, in preserved specimens. Eyes present. All chaetae similarly bifid, upper tooth being slightly longer (the difference decreasing backwards). Dorsal chaetae beginning from VI. Ventral chaetae of II, 120-126 µm long and 2-7 per bundle. Posteriorly, both ventral and dorsal chaetae less numerous (by 2-4) and shorter, 86-110 µm. In mature individuals penial chaetae by 2-3, with blunt, bent tip. Length 5-18 mm, segment number in zooids 19-27, in single individuals 31-54. It can be confused with Piguetiella blanci whose very fine and short hair chaetae can sometimes remain unnoticed. In the species of Paranais, with similar chaetae, dorsal bundles always begin from V, and eyes are lacking.
Crawling on substratum, able to swim.
Distribution
Holarctic; recorded also from Japan and Guyana.
Ecology
In freshwater, common on sand; intestine often full of sand.
Reproduction
Mostly asexual, by paratomy (budding). Mature individuals and sexual reproduction common in the second half of summer.
Literature
Orsted, 1842: 136; Sperber, 1948: 98-99, Fig. 26G, Pl. V Figs 2-4; Sperber, 1950: 58-59, Fig. 8; Brinkhurst and Jamieson, 1971: 325-326, Fig. 7.4A; Chekanovskaya, 1981: 246-247, Fig. 112; Hrabe, 1981: 37, Pl. 3 Figs 9-13; Kasprzak, 1981: 133, Figs 397-398.