Analysis of nuclear abnormalities in erythrocytes of rainbow trout (Oncorhynchus mykiss) treated with Cu and Zn and after 4-, 8-, and 12-day depuration (post-treatment recovery)

• Copper–zinc mixture solution induced geno-cytotoxicity effects in rainbow trout.
• Changes in gross morphometric indices and biological parameters were observed.
• Tissue-specific recovery and fluctuation of geno-cytotoxicity levels were detected.
• Micronuclei were found to increase after 4-day recovery in all tissues.
• Blood erythrocytes showed significant recovery of all geno-cytotoxicity endpoints.

The induction of micronuclei (MN), nuclear buds (NB), bi-nucleated erythrocytes with nucleoplasmic bridge (BNb), vacuolated (VacNuc), blebbed (BL), 8-shaped nuclei, bi-nucleated (BN) and fragmented-apoptotic (FA) erythrocytes was analysed in the peripheral blood, cephalic kidney and liver of rainbow trout Oncorhynchus mykiss after 4-day treatment with copper (Cu) and zinc (Zn) mixture solutions and in 4-, 8- and 12-day depuration process. Fish (three treatment and one control group, N = 40) were exposed to 0.0625, 0.125 and 0.25 fractions of 96-h LC50, respectively under semi-static conditions. Exposure of O. mykiss to Cu and Zn induced significant increase of MN (in blood in all test groups; in liver 0.125, 0.25 and in kidney 0.25 groups, respectively), NB and BL (in blood and kidney 0.25 group), 8-shaped (in blood 0.25; in liver 0.125, 0.25 and in kidney all test groups, respectively) and VacNuc (in liver and kidney 0.0625 and 0.125 groups). After 4-day recovery, significantly elevated levels of MN (in blood 0.0625, 0.125; in liver and kidney 0.125 group, respectively) and 8-shaped (in kidney—0.0625 group) were observed in fish. Significant recovery was observed in 0.0625 group after 12-day depuration, estimating the formation of MN in erythrocytes of blood, of 8-shaped nuclei erythrocytes in liver and kidney (after 8-, 12-day and 8-day recovery, respectively). Significant decrease of MN in blood (after 8- and 12-day recovery), in liver (after 8-day recovery), of NB in blood and kidney (after 8-day recovery) and of 8-shaped nuclei erythrocytes in blood (after 8 and 12-day recovery), kidney and liver (after 8-day recovery) was determined in 0.25 group. Changes in gross morphometric indices and biological parameters were observed. The binary metal mixture did not induce FA erythrocytes in any tissue at any test concentration.