(Vejdovsky, 1878)
Description
Medium-sized white or yellowish worms. Chaetae sigmoid, sharp-pointed, without nodulus, mostly by 3, sometimes by 2 or, in caudal portion, even by 4 per bundle, 40-110 µm long. Ventral chaetae absent on male pores. Owing to prevailing asexual reproduction by fragmentation, regenerating anterior or posterior ends often present; in sexually mature individuals, clitellum with male pore often shifted forward (with male pore in VIII, IX, X, or XI). Clitellar glands arranged in transverse rows. Internal characters: Pharyngeal glands usually in 5 pairs, on dissepiments 4/5-8/9, always as dorsal lobes only. In mature individuals, posterior pairs can be reduced. Coelomocytes variable: oval, pear-shaped or spindle-shaped. No appendages on digestive tube. Blood colourless, dorsal blood vessel can be observed up to XIII-XVIII. Spermatheca not connected with oesophagus, can extend backwards up to VII, consisting of roundish ampulla with gradual transition into longer duct. Duct reveals an almost spherical bulboid dilatation containing transversal sperm ring in its distal portion. Large gland present at spermathecal pore in 4/5. Male funnels tubular, 3-5 times as long as width; vasa deferentia long and narrow. Penial bulbs medium-sized and compact; sometimes single submedian, supernumerary blind bulb present. Length 15-25 mm, segment number 40-65 (can be less in regenerating fragments). Cognettia sphagnetorum differs significantly from the related Cognettia glandulosa in its smaller pharyngeal glands devoid of any ventral lobes.
Burrowing in sediment.
Distribution
Europe, eastern North America, Greenland.
Ecology
In soil and in freshwater near the shore, seldom in deep water of oligotrophic lakes.
Reproduction
Almost exclusively asexual, by architomy (fragmentation). Mature individuals and sexual reproduction rare, with eggs laid in cocoons.
Literature
Vejdovsky, 1878: 304; Vejdovsky, 1879: 52-53, Pl. XIII Figs 1-6; Nielsen and Christensen, 1959: 42-43, Figs 28-29; Chekanovskaya, 1981: 398-399, Fig. 201; Kasprzak, 1986: 124-125, Figs 332-334; Timm et al., 1997 : 25-26, Fig. 6.