Dorydrilus tetrathecus

Hrabe, 1960

Description
Middle-sized worms, with two sigmoid, simple-pointed chaetae per bundle. Chaetae 90-143 µm long, with distal nodulus. External secondary annulation beginning from III, with narrow anterior ring in each segment. Male pores in X, spermathecal pores as two pairs in X (before the male pores) and XI, female pores in 10/11; all pores behind ventral chaetae of corresponding segment. Internal characters: Pharyngeal glands in IV-VI. Chloragogen cells on digestive tube begin from the middle of VII. Testes in IX, ovaries in X. Large male funnels on 9/10, vasa deferentia make a loop in X and fall into apical end of pear-shaped atria covered with minute prostatic cells. Ectal end of atrium can be protruded from male pore as pseudopenis. Two pairs of spermathecae, in X and XI, with large oval ampullae and clearly limited ducts. Length about 15 mm, segment number at least 61. Externally very similar to several lumbriculids, particularly to those of the genus Trichodrilus; differing from them in the location of testes and male pores in different segments. Differing from congeners in having a double pair of spermathecae.
Burrowing in sediment.

Distribution
Germany.

Ecology
In freshwater, mainly in groundwater.

Reproduction
Sexual only. Eggs laid in cocoons.

Literature
Hrabe, 1960: 261-264, Figs 17-19; Cook, 1971b: 649-650, Fig. 10.1C; Kasprzak, 1981: 185.

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