Stylodrilus parvus

(Hrabe and Cernosvitov, 1927)

Description
Small yellowish worms. Prostomium rounded, slightly longer than width. External secondary annulation beginning from V. Chaetae two per bundle, sigmoid with nodulus, bifid with short parallel upper tooth. Male pores in X simple, without any penes; spermathecal pores in IX. Clitellum in 1/2 IX-1/2 XII. No blind appendages on dorsal blood vessel. Testes in IX and X; posterior pair of vasa deferentia penetrate dissepiment 10/11 twice. Atria in X small spherical or ovoid, covered with prostatic cells. Length 10-15 mm, segment number 54-68. Among lumbriculids with small parallel upper tooth in chaetae, this species differs from Stylodrilus heringianus and Stylodrilus brachystylus in lack of penes, from Bichaeta sanguinea in presence of spermathecae, and from Trichodrilus strandi and Trichodrilus diversisetosus in the position of reproductive system.
Burrowing in sediment.

Distribution
Europe, Caspian Sea, Lake Baikal.

Ecology
In freshwater, particularly in streams.

Reproduction
Sexual only. Eggs laid in cocoons.

Literature
Hrabe and Cernosvitov, 1927: 203-207, Figs 1-4; Cook, 1971a: 245, Figs 5.5E, 5.6F; Chekanovskaya, 1981: 447-448, Fig. 224; Hrabe, 1981: 101-102, Pl. 18, Fig. 5; Kasprzak, 1981: 196, Figs 781-783.

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