HYDRODYNAMIC CHARACTERISTICS OF DAPHNIA-MIDDENDORFFIANA

Sinking terminal velocities of D. middendorffiana (with and without ta i; spine) were measured and correlated with morphological parameters a nd water temperature. The main dimensions of the body showed positive growths rate correlations with the body weight. In turn, negative allo metric variation was observed in the tail-spine length. The density of D. middendorffiana was age specific, and decreased as the individual grew. No differences in the sinking terminal velocities and trajectori es between individuals with and without tail spine were observed. The observed hydrodynamic characteristics of D. middendorffiana were simul ated by means of a model based on equivalent ellipsoids and spheres. T he analysis showed that the effects of shape and the body projections are negligible on the sinking rates of D. middendorffiana.