Evaluation of Di-ammonium Phosphate (DAP)-Induced Genotoxicity in Channa punctatus Using the Micronucleus Assay

Abstract

The extensive and often indiscriminate use of chemical fertilizers, particularly diammonium phosphate (DAP), poses a potential threat to freshwater ecosystems. The present study evaluated the genotoxic effects of DAP in the freshwater fish Channa punctatus using the micronucleus assay. Fish were exposed to three sub-lethal concentrations of DAP (0.4, 0.8, and 2.0 g/L) for 96 h, along with an unexposed control group maintained under identical laboratory conditions. Peripheral blood smears were prepared from individual fish, stained with 6% Giemsa solution, and approximately 3,000 erythrocytes were examined per treatment group. Data were analyzed using one-way ANOVA followed by Tukey’s HSD test. Exposure to DAP produced a significant dose-dependent increase in micronucleus frequency. The middle-dose (0.8 g/L) and high-dose (2.0 g/L) groups showed significantly higher micronucleus frequencies than the control group (p < 0.001), whereas the low-dose group (0.4 g/L) did not differ significantly (p = 0.997). In addition to micronuclei, several nuclear abnormalities, including blebbed nuclei, V-shaped nuclei, kidney-shaped nuclei, nuclear buds, notched nuclei, and nucleoplasmic bridges, were observed in DAP-treated fish. The frequency and diversity of these abnormalities increased with increasing DAP concentration, indicating progressive genomic damage. These findings demonstrate that DAP can induce chromosomal damage and genotoxic stress in Channa punctatus even at sub-lethal concentrations and highlight the need for improved management of fertilizer runoff to protect freshwater ecosystems.