rotunda (Straus, 1820) sensu Sars, 1862

Kotov, Alexey A., Ibragimova, Aisylu G. & Neretina, Anna N., 2018, Identification of Ceriodaphnia Dana, 1853 (Crustacea: Cladocera) taxa from European Russia based on ephippial morphology, Zootaxa 4527 (1), pp. 105-123 : 111

Ceriodaphnia rotunda (Straus, 1820) sensu Sars, 1862

( Figs. 5–6 )

Length about 0.5 mm, width about 0.75 of length. In lateral view, ephippium semicircular; dorsal margin very slightly convex; ventral margin regularly curved from postero-ventral to anterior margin ( Figs. 5A , 6 A–B, D). Paired latero-dorsal ridges absent. A depression along dorsum separating two halves of ephippium indiscernible; sculpture of dorsal plate consisting of very thin longitudinal wrinkles and numerous minute columns, not organized into spots ( Figs. 5 B–C). Egg locule visibly extends laterally, without any wrinkles, but with numerous, densely located semicircular projections ( Figs. 5B, D ) well visible also under optical microscope ( Fig. 6C ); a patch of minute columns on each semicircular projection. Space between egg locule and dorsal margin with low, flattened projections (not associated with any air-spaces) bearing patches of minute columns ( Fig. 5B ). The rest of ephippium surface covered by low, densely located flattened domes ( Figs. 5 F–F, 6C) — external signs of air-spaces which are well-visible under light microscope, each dome with a spot of minute tubercles. Ephippium has a very narrow ventral rim without any sculpture ( Fig. 5F ). In general, minute tubercles (i.e. represented by minute columns) are better developed in all portions of ephippium as compared to C. laticaudata .

Figures

FIGURE 5. Ceriodaphnia rotunda (Straus, 1820), ephippium from a ditch from Lake Svetets, Vladimir Area. A, lateral view of ephippium. B, its dorsal portion, lateral view. C, dorsum, lateral view. D, sculpture of central portion. E, sculpture of posterior portion. F, ventral portion. Scale bars: 0.1 mm for A; 0.01 mm for B–F.

FIGURE 6. Ceriodaphnia rotunda (Straus, 1820), ephippial female from a ditch from Lake Svetets, Vladimir Area. A, general view. B–C, ephippium on ephippial female. D, separated ephippium. Scale bars: 0.1 mm.