Iglikowska_MINIATURA 5_2021_05_X_NZ8_00025.xlsx

This study tested in the laboratory settings the influence of environmental aqueous concentrations of zinc (230 and 410 µg Zn L^-1) and copper (260 and 460 µg Cu L^-1) on fitness-related life history traits of a cosmopolitan freshwater ostracod <i>Heterocypris incongruens </i>originating from laboratory (Ostracodtoxkit f) and wild (anthropogenic temporary pool) populations. Additionally, we aimed at determining whether the presence of those metals in surrounding water increases their concentration in ostracod tissues. The response of ostracods to the exposure of Zn and Cu differed considerably. Whereas the Cu treatments significantly reduced the total hatching success and hatching dynamics of resting eggs, increased mortality of juveniles and reduced survival of adults, dramatically decreasing fitness of ostracods, the Zn treatments were less harmful, not affecting adult survival and timing of juvenile hatching from subitaneous eggs. The effects of Zn on other studied fitness traits were not conclusive; although both concentrations of Zn reduced mortality of juveniles, the lower concentration extended the time of laying eggs, while the higher – stimulated hatching dynamics and success. Moreover, a different response of the laboratory and wild populations reported in the Zn experiments may suggest a genetically-cued tolerance variation of ostracods to metals in ambient environment. Therefore, experiments involving laboratory <i>H. incongruens </i>as analogues of wild ostracods should be cautiously interpreted. Finally, we found a positive correlation between the levels of Zn and Cu in ambient water and in ostracod bodies, which may indicate that <i>H. incongruens</i> tend to accumulate rather than eliminate these metals. It seems that the increased Zn body burden did not intensely impact fitness of the studied specimens. Thus, we conclude that the major toxicant in our study was Cu while Zn could be considered as a micronutrient even supporting ostracod fitness, although its higher levels are likely to exert strong toxic effects.