Impact of ions of zinc and cadmium on body weight, fertility and condition of the tissues and organs of Procambarus virginalis (Decapoda, Cambaridae)

Abstract

Heavy metals cause functional disorders in the tissues and organs of hydrobionts, affecting their linear-weight indicators, reproductive system, digestive and eliminative organs. Using the method of histological estimation of the conditions of the tissues and organs of Procambarus virginalis Lyko, 2017 allowed us to determine the peculiarities of adaptation of crustaceans to the effect of different concentrations of heavy metal ions in the conditions of a modeling experiment. We studied the impact ions of zinc (0.1 mg/l) and cadmium (0.01 mg/l) on the organism of P. virginalis. The heavy metal ions had a negative effect on the weight indicators, survivability and reproduction of P. virginalis. During the experiments with zinc, we observed death of 18.2% of the tested сrustaceans; the highest death rate was observed in the experiment with cadmium – 27.3%. Experimentally modeled concentrations of heavy metals negatively affected the reproductive system of P. virginalis. In the experiment with cadmium ions, we observed no spawning; the highest percentage of the females with deposed eggs was observed in the control – 29.1%. The conducted studies allowed us to observe the reaction of the eliminatory system of P. virginalis to the impact of heavy metal ions. The impact of ions of zinc and cadmium decreased the area of secretory cells of the green gland by 10.4–14.8%. We observed grinding of the nuclear cell apparatus. Therefore, the nucleii of granulocytes were 23.6% smaller under the impact of zinc, and 17.5% smaller under the influence of cadmium. The sizes of cells and nucleus apparatus decreased mutually and proportionally; this was proven by stable indicators of nucleus-cytoplasm ratio, its value equaled 0.29–0.31 units. The given concentrations of heavy metals did not affect the histological condition of the adipose tissue, the sizes of adipocytes fluctuated within the range of 215–2178 μm2, the average equaled 872–994 μm2. We determined the negative effect of heavy metals on the histological structure of the hepatopancreas and the value of gland lumens. In the control, the area of previous section equaled 164.5 μm2 with 39 μm2 lumen. During the experiment with zinc ions the structures of hepatopancreas increased by 19.9%, and in the experiment with cadmium, we observed the highest increase in the structural elements of the tissues – by 50.2%. The worst histological condition of the cells of the tested tissues and organs of P. virginalis was observed among individuals impacted by the cadmium ions; this is explained by the high toxic effect of this heavy metal.