Ceriodaphnia quadrangula (O.F. Müller, 1785)

(Figs. 7–8)

Length about 0.35–0.4 mm, width about 0.6–0.65 of length. In lateral view, ephippium semicircular; dorsal margin slightly convex to almost straight; ventral margin regularly curved from postero-ventral to antero-ventral angle (Figs. 7 A–B, 8A–D). Paired latero-dorsal ridges absent (Figs. 7 S–C). A distinct depression along dorsum separates two halves of ephippium and, respectively, two halves of dorsal plate with sculpture of relatively thick small columns with branched tips (Figs. 7 D–E); no any wrinkles or low projections are detected, no air spaces in this region. Egg locule somewhat extends laterally (Fig. 7B); surface of locule with columns bearing branched tips as in the region of dorsal plate (Figs. 7 E–F). The rest of ephippium surface covered by same columns, but towards the margins they diminishing in size, and finally they are transformed into circles of small tubercles (Fig. 7H). Airspaces expressed in ventral portion of ephippium well-visible under light microscope (Figs. 8 C–F), but no their signs visible under SEM, excluding most ventral portion, where they are slightly elevated above the general surface, just each air space bears the circle of small tubercles described above (Fig. 7H). Ventral rim of ephippium lacking air spaces, without reticulation (Figs. 7H, 8F).