(Martin, 1907)
Description
Small transparent worms. Prostomium rounded, bearing small tentacle. Eyes present or lacking. Dorsal bundles beginning from VI, with 1-18 hair chaetae, 222-395 µm long, and between them, in a fan-like arrangement, 7-15 needle chaetae of the same shape but much shorter (62-68 µm). Ventral chaetae by 3-7, with longer upper tooth, in II 144-149 µm long, shortening gradually in III-IV, and from VI on 110-128 µm long. In mature individuals penial chaetae by 4, with simple hooked tip. Length 8-10 mm, segment number in zooids 32, in single individuals 42-50. Differing from Stylaria lacustris in lack of lateral lobes on prostomium, cylindrical body, and numerous very thin dorsal needle chaetae like in Ripistes parasita. However, giant hair chaetae, characteristic of the latter, do not occur in Arcteonais lomondi.
Crawling on substratum. Not swimming.
Distribution
Holarctic; recorded also from China and Japan
Ecology
In freshwater. Sometimes even in muddy deeper zones devoid of any other naidids, in lakes.
Reproduction
Mostly asexual, by paratomy (budding). Mature individuals and sexual reproduction rare or seasonal.
Literature
Martin, 1907: 25-26, Pl. II; Sperber, 1948: 142-143, Fig. 15G; Sperber, 1950: 67, Fig. 19; Brinkhurst and Jamieson, 1971: 350, Fig. 7.10I-K; Chekanovskaya, 1981: 200-201, Fig. 82; Hrabe, 1981: 51-52, Pl. 8 Figs 8-11; Kasprzak, 1981: 107, Figs 259-260.