Pyrogallol-mediated acute, developmental, and neurobehavioral alterations investigated using larval zebrafish

Pyrogallol, a phenolic compound derived from the natural breakdown of tannins, possesses several properties that make it valuable for various industrial applications. Its natural occurrence and widespread industrial use contribute to its environmental presence in aquatic ecosystems. However, our understanding of its potential environmental and human health risks remains limited due to the insufficient toxicity information available. This study investigates the acute, developmental, and neurobehavioral toxicities of developmental exposure to pyrogallol in larval zebrafish. Acute toxicity was assessed over 96 h to determine the 24-, 48-, 72-, and 96-h post-fertilization (hpf) median lethal concentration (LC₅₀) values. Embryos were exposed to sub-LC₅₀ concentrations of pyrogallol (2, 10, 20, 50, and 100 nM) from 6 to 120 hpf to evaluate its developmental and neurobehavioral toxicities. Mortality rates, developmental abnormalities, overall growth, baseline activity, and behavioral responses to acoustic and visual stimuli were measured. LC₅₀ values, determined using Hill's equation, were 2.049 μM at 24 h, 0.472 μM at 48 h, 0.297 μM at 72 h, and 0.210 μM at 96 h. Sub-lethal toxicity assessments revealed a reduction in total larval length and an increase in baseline locomotor activity. Significant increases in the prevalence of developmental defects, including yolk sac edema, body axis defects, pericardial edema, pigmentation defects, and swim bladder defects, were observed. Additionally, pyrogallol-exposed larvae showed a depression in their behavioral responses to acoustic stimuli and exaggeration in their behavioral responses to visual stimuli regardless of morphological defects. These results underscore the significant toxicological impacts of pyrogallol at nanomolar concentrations on zebrafish larval development and behavior, highlighting the need for comprehensive environmental risk assessment and stricter regulatory oversight of pyrogallol contamination in aquatic ecosystems.