Giemsa versus acridine orange staining in the fish micronucleus assay and validation for use in water quality monitoring

Abstract

This study concerns a comparative analysis of the acridineorange and Giemsastaining procedures for the fish erythrocyte micronucleusassay. The goal was to optimize the assay in the context of field watermonitoring. Fish (Carassius carassius) were exposed to a reference genotoxic agent, cyclophosphamide monohydrate 5 mg l−1 for 2, 4, and 6 days before testing. Slides from each individual were scored using the two procedures. The results show that the assay was more sensitive when acridineorange was used. When slides were Giemsa stained, the presence of ambiguous artefacts, leading to false positives and increasing random variance, reduced the contrast between exposed and control samples. AcridineOrangestaining was then applied in the context of waterqualitymonitoring. Fish were exposed for 4 days to water sampled in two hydrological contexts: basal flow and spring flood. The results show that exposure to spring flood water in an agricultural stream can induce mutagenicity.