Deltamethrin is responsible for health and reproduction problems both in mammals and aquatic organisms. In this study, zebrafish adults were exposed for 15 days to 0.25, 0.5, 1, and 2 μg L⁻¹ non-lethal concentrations of deltamethrin, knowing that is used worldwide on agricultural crops. We investigated the chronic effects of deltamethrin on gonads by histopathological examination, immunohistochemistry, and immunofluorescence using biomarkers for apoptosis (anti-p53, anti-H2A.XS139ph antibodies, and TUNEL assay), oxidative stress (anti-Cox4i1 antibody) and proliferation (anti-PCNA antibody). Among the histopathological changes, the apoptotic response was elevated in ovary and testis of deltamethrin exposed groups as it was seen in the IHC and IF for p53, H2A.XS139ph, and confirmed by TUNEL assay. These were observed in the case of all studied concentrations compared with the control group. Thereby, the gonadal tissue exhibited an up-regulated activity of this cell-death signaling markers, while the proliferation marker (PCNA) increased in the ovary due to its presence not only in primary growth and cortical-alveolar stage follicles but also in atretic follicles, meanwhile decreased notably in the testis. Cox4i1, a mitochondrial marker, decreased both in ovary and testis during deltamethrin treatment, probably inhibited by the overproduction of the free radicals after pesticide exposure.

Wild-type (WT) zebrafish are commonly used in behavioral tests, however, the term WT corresponds to many different strains, such as AB, Tübingen long fin (TL), and Wild Indian Karyotype (WIK). Since these strains are widely used, there has to be at least one study to demonstrate the behavioral differences between them. In our study, six zebrafish strains were used, which are AB, absolute, TL, golden, pet store-purchased (PET), and WIK zebrafishes. The behavior of these fishes was tested in a set of behavioral tests, including novel tank, mirror-biting, predator avoidance, social interaction, and shoaling tests. From the results, the differences were observed for all behavioral tests, and each strain displayed particular behavior depending on the tests. In addition, from the heatmap and PCA (principal component analysis) results, two major clusters were displayed, separating the AB and TL zebrafishes with other strains in another cluster. Furthermore, after the coefficient of variation of each strain in every behavioral test was calculated, the AB and TL zebrafishes were found to possess a low percentage of the coefficient of variation, highlighting the strong reproducibility and the robustness of the behaviors tested in both fishes. Each zebrafish strain tested in this experiment showed specifically different behaviors from each other, thus, strain-specific zebrafish behavior should be considered when designing experiments using zebrafish behavior.

The overuse of antibiotics combined with the limitation of wastewater facilities has resulted in drug residue accumulation in the natural environment. Thus, in recent years, the presence of antibiotic residues in the environment has raised concerns over the potential harmful effects on ecosystems and human health. The in vivo studies represent an essential step to study the potential impact induced by pharmaceutical exposure. Due to the limitations of traditional vertebrate model systems, zebrafish (Danio rerio) has recently emerged as a promising animal model to study the toxic effects of drugs and their therapeutic efficacy. The present review summarizes the recent advances made on the toxicity of seven representative classes of antibiotics, namely aminoglycosides, β-lactams, macrolides, quinolones, sulfonamides, tetracyclines and polyether antibiotics, in zebrafish, as well as the combined effects of antibiotic mixtures, to date. Despite a significant amount of the literature describing the impact of single antibiotic exposure, little information exists on the effects of antibiotic mixtures using zebrafish as an animal model. Most of the research papers on this topic have focused on antibiotic toxicity in zebrafish across different developmental stages rather than on their efficacy assessment.