Potamothrix heuscheri

(Bretscher, 1900b)

Description
Small smooth pink worms. Prostomium short conical, separated by a distinct furrow from I, in alcohol-preserved specimens. Body wall delicate, with deep intersegmental furrows on tail when preserved. Anterior dorsal bundles consisting of 2-5 hair chaetae, 245-554 µm long, and 2-5 pectinates, 98-144 µm long, with short intermediate teeth. Anterior ventral chaetae by 3-5, 80-160 µm long, with slightly longer and thinner upper tooth. Spermathecal chaetae in X 121-224 µm long, their distal portion straight and narrow (up to 8 µm), with furrow with parallel edges, and with sharp hooked tip; their proximal end also hooked. Male pores in XI, accompanied with a few ordinary crotchets. Length 6-15 mm, segment number 36-150. Differing from congeners in its narrow spermathecal chaetae.
Burrowing in sediment.

Distribution
Western Palaearctic, East Africa, Lake Titicaca in South America.

Ecology
In fresh and slightly brackish water, highly tolerant of oxygen deficiency in stratified lakes.

Reproduction
Sexual only. Eggs laid in cocoons.

Literature
Bretscher, 1900b: 435; Brinkhurst and Jamieson, 1971: 490, Fig. 8.11H-I; Chekanovskaya, 1981: 326, Fig. 159; Hrabe, 1981: 81-82, Pl. 12 Fig. 22; Kasprzak, 1981: 157, Fig. 526; Timm et al., 1997: 19-21, Fig. 3.

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