Diaphanosoma lacustris Kořinek, 1981

(Fig. 4)

Kořinek, 1981: 1119, Fig. 12–18 ( D. birgei lacustris, partim); Korovchinsky, 1987: 741–747, Pl. V–IX; 1992: 39, figs. 185– 190; 2004: 297, Fig. 107.

Diagnosis. Parthenogenetic female. Body conically-rectangular, head comparatively small (34.5–38.8 % of body length), with a protruding dorsal part (Fig. 4 A) which is sometimes deformed (Fig. 4 B). Eye (5.2–6.8 % of body length) situated near antero-ventral or ventral head margin. Antennules small of regular type. Swimming antennae comparatively short (60.0–73.8 % of body length), with the upper antennal branch not reaching the posterior valve margin (Fig. 4 A). The proximal segment of the branch has a conspicuous apical denticle (Fig. 4 C). Shell comparatively high; valves with more or less high posterior margin bearing a small inner thorn (Fig. 4 D, 4H). The ventral valve margin has a comparatively narrow, long inflexion with 9–11 long marginal feathered setae without marginal setulae between them, proximal ones implanted submarginally. Postero-ventral valve margins bear 18–37 small, thin, densely situated denticles with thin setulae between every two to six of them (Fig. 4 F, 4G). Postabdominal claws with three basal spines, proximal one conspicuously smaller than others (Fig. 4 I). Body length: 0.78–0.98 mm.

Remarks. Specimens from Lake Turkana resemble D. mongolianum in having small number of denticles on postero-ventral valve margins yet all other features (comparatively small head and eye, short swimming antenna, high posterior valve margin) unequivocally characterize them as D. lacustris . The small number of denticles on postero-ventral valve margins may be a result of inter-population morphological variability, particularly due to the small size of individuals. Similar features were found in the specimens from Lake Kinneret (Israel) and from a Bulgarian reservoir (see Korovchinsky 1987).