Developmental and Behavioral Effects of Arsenobetaine in Zebrafish (Danio rerio)

Arsenobetaine (AsB) is a prevalent organoarsenical in aquatic environments and is generally regarded as nontoxic. Despite its widespread occurrence, the developmental and neurobehavioral toxicity of AsB has not been systematically investigated. Here, we examined how waterborne exposure to AsB influences early development, oxidative stress, behavior, and neurogenesis in zebrafish (Danio rerio). At approximately ~1-h post fertilization (hpf), embryos were exposed to environmentally relevant levels of AsB (0, 100, 200, 600, and 1200 μg/L) until 5-day postfertilization (dpf). Developmental endpoints, including survival, hatching success, and deformities, were assessed, while behavioral responses were evaluated using locomotor and thigmotaxis assays. Oxidative stress levels were evaluated by quantifying reactive oxygen species (ROS) and lipid peroxidation, and gene expression analyses targeted pathways involved in neurogenesis, neural signalling, and antioxidant defence. Exposure to higher concentrations of AsB (600 and 1200 μg/L) significantly reduced survival and hatching success and increased deformities. Larvae also exhibited hyperlocomotion and anxiety-like behavior, accompanied by elevated oxidative stress. Gene expression analyses revealed significant alterations in genes involved in neurodevelopment, dopaminergic and motor neuronal signalling, as well as antioxidant responses. These findings demonstrate that AsB is not biologically inert during early life stages and may pose risks to aquatic ecosystems.