Developmental toxicity of fluconazole and 1,2,4-triazole in non-target aquatic vertebrates

Fluconazole (FLU) is a widely used antifungal agent frequently detected in surface waters because of its extensive use in medicine, agriculture, and personal care products. Despite concerns about its persistence and developmental toxicity in aquatic species, its effects on amphibians remain poorly understood. This study aimed to assess the developmental and molecular effects of FLU and its structural core, 1,2,4-triazole (TRI), in amphibian embryos. Xenopus laevis embryos were exposed to FLU or TRI and evaluated for mortality, hatching rate, heart rate, body length, malformation incidence, and changes in gene expression. Even at low micromolar concentrations, both azoles altered the expression of Wnt- and BMP-associated genes, indicating disruption of these signaling pathways. At higher micromolar concentrations, these molecular changes were accompanied by early signs of developmental abnormalities, which intensified at the highest doses. Observed phenotypes included reduced head size, altered skin pigmentation, prolonged body length, changes in heart rate, and mild digestive tract malformations. These findings demonstrate that even the core structural motif TRI can disrupt key developmental signaling pathways in vertebrate embryos, underscoring the need for closer monitoring of azole compounds in aquatic environments. Given the fundamental role of these pathways in vertebrate development, the results raise concerns about potential risks from long-term or prenatal exposure to azoles, in both environmental and clinical contexts.