Effect of nanochelate metal complexes on viability of cyprinids at embryonal stages of development

Purpose — to establish the patterns of the effect of complex compounds of copper, iron, zinc and magnesium on the survival rates and embryogenesis of various cyprinid species (common carp, silver carp and grass carp). Methodology. The experiments were conducted at the Bila Tserkva Experimental Hydrobiological Station of the Institute of Hydrobiology of the NAS of Ukraine. The material for the study were fertilized eggs of cyprinids (at different stages of embryonic development): common carp Cyprinus carpio (L.), grass carp Ctenopharyngodon idella (Val.), and silver carp Hypophthalmichthys molitrix (Val.). Fish eggs were obtained by stripping. The samples were kept in 50 cm3 Petri dishes in solutions with a certain concentration of metal chelate complexes. The exposure for common carp eggs was 3.5 days, and 32–36 hours for grass carp and silver carp that corresponded to the duration of embryogenesis of these species. The effect of substances was assessed by egg survival rate, by the degree of egg damage by the pathogenic fungus Saprolegnia, and visually by the development of bacterial fauna by turbidity of the water without visible mineral sediment. Findings. Nanoaquachelate complexes of metals were significantly less toxic to fish at early stages of ontogenesis compared to ions of these elements. Significant concentrations of these complexes were required for negative effects. Toxic manifestations of copper complexes were observed at concentrations <2.5 mg/dm3 for common carp eggs, and acute toxicity at <5.0 mg/dm3, with a maximum concentration of 0.1 mg/dm3. Iron complexes were more toxic to fish embryos. But for a phytophilic fish species (common carp), toxic concentrations of iron complexes exceed 5.0 mg/dm3. Iron content from 0.01 to 2.5 mg/dm3 has a biotic effect on the course of carp embryogenesis. Iron was an even more active fungicide compared to copper. Magnesium ions had a beneficial effect on the development of fish eggs, which was associated with improving environmental conditions and reducing the possibility of toxicants and fish metabolites entering the embryo through the egg shell. The biotic effect of magnesium compounds on carp eggs was observed at a concentration of 10–20 mg/dm3. Originality. For the first time, the biological and toxicological effects of nanochelate complexes of copper, iron, zinc and magnesium on fertilized eggs of cyprinids at different stages of embryogenesis have been comprehensively investigated. The patterns of the combined action of these compounds have been established, which was manifested in the presence of a pronounced fungicidal and bactericidal effect (in particular, against saprolegniosis pathogens) while maintaining high viability of eggs. Practical Value. The possibility and feasibility of using nanoaquachelate complexes of copper and iron in fish farming for artificial reproduction of fish is shown.