Nuclear Abnormalities in Erythrocytes of Black Spiny-Necked Turtles (Acanthochelys spixii) as Evidence of Agrochemical Contamination in a Monoculture Landscape in Brazil

Agricultural production imposes intense pressure on the species living in agricultural matrices, especially concerning agrochemical contamination. The Upper Paranapanema River Basin, located in the southwest region of São Paulo State of Brazil, comprises extensive agricultural areas due to its high soil quality and ample availability of water resources. This study evaluated the possible impact of agrochemicals on populations of the black spiny-necked freshwater turtle (Acanthochelys spixii) that inhabit ponds in monoculture matrices through the employ of a micronucleus (MN) test and other erythrocytic nuclear abnormalities (ENAs). We compared the frequency of MNs and other ENAs between free-living individuals from contaminated environments and reference individuals from captivity. We found strong and highly significant evidence of chromosome damage in the free-living population from contaminated environments. The MN frequency per 1000 cells in these individuals was 104 times higher than that in reference individuals from captivity (2.08 vs. 0.02), while the ENA frequency was 4.7 times higher (24.92 vs. 5.31). In addition, the differences found between free-living and captive specimens of A. spixii is much higher than that reported in similar studies with other freshwater chelonians species. This result suggests that free-living A. spixii might have been exposed chronically to a substantial quantity of agrochemicals while inhabiting agricultural matrices, highlighting a potentially underestimated impact on the conservation of Brazilian freshwater chelonians.