Cadmium and lead: genotoxic effects on the broodstock of the fish Prochilodus magdalenae (Characiformes: Prochilodontidae)

Introduction: Heavy metals such as cadmium (Cd) and lead (Pb) pose a significant threat to aquatic ecosystems due to their persistence, capacity for bioaccumulation, and genotoxic potential. These contaminants are of particular concern in tropical freshwater systems, where they may impact native species of ecological, economic, and nutritional importance, such as Prochilodus magdalenae, a migratory fish endemic to the Magdalena–Cauca River basin in Colombia. Objective: To evaluate the acute effects of individual and combined exposure to Cd and Pb on behavioral parameters, mortality, and genetic damage in P. magdalenae. Methods: Three individual doses of each metal and five binary combinations were administered via intramuscular injection in adult fish, followed by analysis using genotoxicity biomarkers (micronuclei, nuclear abnormalities, and DNA integrity damage). Results: Evident behavioral changes, increased mortality, and significant genotoxic damage were demonstrated, particularly in treatments involving combined exposures. The highest mortality rate (75 %) occurred in the 0.8 μg Cd/kg + 14 μg Pb/kg treatment. Pb exposure was associated with a greater frequency of micronucleus formation, while Cd exposure induced an increase in nuclear abnormalities, without a clear dose–response trend. The comet assay confirmed primary DNA damage particularly in 0.2 μg Cd/kg + 8.0 μg Pb/kg and 0.8 μg Cd/kg + 14 μg Pb/kg treatments, where effects exceeding those of individual exposures were observed. Nevertheless, non-linear responses were detected in some treatments, possibly due to adaptive cellular responses or apoptosis. A sex-dependent susceptibility was also identified: males exhibited higher mortality rates but lower micronucleus frequencies than females. Conclusions: The toxic potential of Cd and Pb is highlighted, and the suitability of P. magdalenae as a sentinel species for environmental monitoring supported. The study emphasizes the need to consider co-exposure scenarios in ecotoxicological risk assessments, due to their relevance to ecosystem health, human consumption, and food security in regions where this species represents a vital resource.