(Müller, 1774)
Description
Small to medium-sized, reddish worms. Chaetae in fan-like bundles, sigmoid without nodulus, by 2-8, 70-110 µm long, most numerous in ventral bundles. Ventral chaetae lacking at male pores in XII. Clitellum covering XII-1/2 XIII or XIII. Clitellar glands irregularly scattered. Internal characters: Pharyngeal glands in three pairs, IV-VI, both dorsal and ventral lobes present; the first two pairs merge dorsally, while those of the last pair are free. Coelomocytes oval or pear-shaped, with coarse granules. Chloragogen tissue on oesophagus present from VI, particularly dense in VII-VIII and in postclitellar region. No appendages on digestive tube. Blood reddish, dorsal blood vessel reaches up to postclitellar segments. Spermathecae in V, connected with oesophagus, spindle-shaped, slightly constricted externally but with distinctly bipartite lumen; its ectal half is thick-walled but ental half has thinner wall and contains most of sperm. High, dense crown of fused, entally lobed glands at ectal end of spermathecae. Numerous lobes of sperm vesicles full of spermatozoa, attached to body wall at 10/11 and extending bush-like into cavity of IX-XI. Length of male funnels five times as large as width, 1.5 times body diameter; collar regular and slightly wider than funnel itself. Vasa deferentia twice as long as funnels, loosely coiled in XII. Penial bulbs medium-sized, compact. Usually 8-12 mature eggs present at a time. Length 10-18 mm, segment number 35-58. Differing from congeners in some internal characters, including bipartite spermatheca. A variable species, particularly due to presence of polyploid forms.
Burrowing in sediment.
Distribution
Cosmopolitan.
Ecology
In the marine littoral, in the sublittoral of the brackish Baltic Sea, sometimes in polluted freshwater.
Reproduction
Sexual (but including parthenogenesis), with eggs laid in cocoons.
Literature
Müller, 1774: 29; Claparède, 1861: 82; Pl. III Fig. 1-6; Ditlevsen, 1904: 431-433, Fig. 28; Nielsen and Christensen, 1959: 100-102, Figs 109-112; Chekanovskaya, 1981: 388-389, Fig. 197; Kasprzak, 1986: 129-131, Figs 348-351; Coates, 1995: 1727-1734, Fig. 1.