Integrated assessment of metal bioaccumulation and genotoxic biomarkers in blood of broad-snouted caiman (Caiman latirostris) from Northeastern Brazil.

Environmental contamination by heavy metals poses a significant threat to aquatic biodiversity, however, the genotoxic effects in reptiles remain poorly understood, particularly in tropical ecosystems. This study provides the first genotoxic assessment of Caiman latirostris in northeastern Brazil, integrating cytogenetic biomarkers and trace metal analysis. Twenty-eight individuals were sampled from three areas representing distinct levels of anthropogenic pressure: a preserved reference site (Farming Area - FA), a moderately impacted reservoir (Tapacura Reservoir - TR), and a highly urbanized area (Urban Area - UA). Micronucleus frequency (MNF) was significantly higher in specimens from UA compared to FA (Kruskal-Wallis, p < 0.001), indicating potential genotoxic effects associated with untreated urban effluents and metal exposure. Although no significant differences in nuclear anomalies frequency (NAF) were found among sites, a moderate positive correlation was observed between MNF and NAF (Spearman's rho = 0.56; p = 0.026). MNF showed significant positive associations with blood concentrations of aluminum (p = 0.027), chromium (p = 0.049), iron (p = 0.035), manganese (p = 0.043), and zinc (p = 0.0083). Principal Component Analysis (PCA) confirmed these patterns, with MNF aligned along the same vector direction as Al and Cr, and opposed to Fe, Mn, Zn, and Pb, revealing distinct contamination profiles. No significant correlations were found between NAF and individual metals. These findings support the use of MNF and NAF as sensitive and complementary biomarkers for genotoxicity in reptiles. The integration of biomarker responses and multivariate analysis highlights C. latirostris as an effective sentinel species for environmental monitoring. This study provides novel baseline data on cytogenetic biomarkers in crocodilians from tropical freshwater ecosystems, underscoring the need for continued ecotoxicological monitoring in human-impacted areas.