(Gruithuisen, 1828)
Description
Comparatively big and stout, transparent worm, usually occurring as a chain of several zooids. Five anterior segments fused forming head and containing muscular pharynx. Prostomium absent, sometimes a notch in its place at the edge of mouth. Chaetae in ventral bundles only, absent from III-V. Those of II 200-350 µm long and about 4.5 µm thick, 2-20 per bundle; from VI on 2-10 per bundle, 100-218 µm long. Upper tooth of chaetae slightly longer. In mature individuals, clitellum in 1/2 V-VI, and penial chaetae in VI 3-5 per bundle, about 100 µm long, blunt or with vestigial upper tooth. Length 2.5-25 mm, thickness 1 mm, segment number in zooids 9-12, in single individuals 14-15. The biggest species of the genus Chaetogaster. Smaller individuals can be confused with Chaetogaster cristallinus, particularly since Sperber, 1948, 1950 erroneously attributed the notch on the upper edge of the mouth to the latter species (Poddubnaja, 1966). In Chaetogaster diaphanus, stomach in V-VII is surrounded by a blood plexus but with several transversal blood vessels in its anterior part, while in Chaetogaster cristallinus the stomach is surrounded by about 20 pairs of distinct transversal blood vessels not forming any plexus (visible in live worms).
Crawling on substratum.
Distribution
Almost cosmopolitan.
Ecology
In various freshwater bodies, seldom in slightly brackish water, living on water plants and bottom sediment. Common. Feeding on small invertebrates as cladocerans, chironomid larvae, oligochaetes etc.; ingested prey in stomach well visible through transparent body wall.
Reproduction
Paratomy (budding); up to 32 zooids have been observed in a chain. Sexually mature individuals rare, sexual reproduction evidently seasonal; cocoons with single egg, attached to the substratum.
Literature
Gruithuisen, 1828: 409-416, Pl. XXV Figs 1-5; Sperber, 1948: 66-68, Figs 5, 7D, I, Pl. I Figs 5-6; Sperber, 1950: 52, Fig. 3D; Poddubnaja, 1966: 120-124; Brinkhurst and Jamieson, 1971: 310-311, Fig. 7.1I-K; Chekanovskaya, 1981: 257-259, Fig. 119; Hrabe, 1981: 32, Pl. 2 Figs 9-11; Kasprzak, 1981: 94, Figs 174-185.