Exposure to acetochlor impairs swim bladder formation, induces heat shock protein expression, and promotes locomotor activity in zebrafish (Danio rerio) larvae

• Published in: Ecotoxicology and environmental safety 2021-12, Vol.228, p.112978, Article 112978
• Main Authors: Huang, Tao, Wang, Shuo, Souders, Christopher L., Ivantsova, Emma, Wengrovitz, Andrew, Ganter, Jade, Zhao, Yuan H., Cheng, Hongguang, Martyniuk, Christopher J.
• Format: Article
• Language: English
• Subjects: Agriculture; Agrochemical; Aquatic species; Developmental toxicity; Risk assessment
• ISSN: 0147-6513; 1090-2414
• DOI: 10.1016/j.ecoenv.2021.112978

Acetochlor is one of the most widely used herbicides in the world, however, there are few data on the sub-lethal effects of acetochlor on early developmental stages of fish. To address this, we measured survival, deformity, swim bladder formation, embryo oxygen consumption rates, reactive oxygen species (ROS) levels, transcripts (related to swim bladder formation, oxidative damage response, and apoptosis) and behavior responses following exposure to acetochlor (0.001 µM up to 125 µM). Exposure to acetochlor at concentrations 50 µM and above exerted 100% mortality after 3 dpf, and significantly reduced the size of the swim bladder (25 µM). In embryos, basal respiration, oligomycin-induced ATP production, and maximal respiration were decreased 30–60% following a 24 h exposure to 125 μM acetochlor. Acetochlor did not affect ROS levels up to 25 µM in larvae with acute exposure. Acetochlor at 25 µM increased mRNA levels of bax1, hsp70, and hsp90a by ~4-fold in larval zebrafish. In both the visual motor response and light-dark preference test, 25 µM acetochlor increased locomotor activity of larval fish. At lower exposure concentrations, 100 and 1000 nM acetochlor increased the mean time spent in the dark zone, suggesting promotion of anxiolytic behavior. This study presents a comprehensive evaluation of sublethal effects of acetochlor, spanning molecular responses to behavior, which can be used to refine risk assessment decisions for aquatic environments. [Display omitted] •Swim bladder malformation was observed with 25 µM acetochlor exposure.•Oxygen consumption rates were decreased following 24 h exposure to 125 µM acetochlor.•Pro-apoptotic bax1 and heat shock protein expression were induced by 25 µM acetochlor.•Hyperactivity in larvae was observed following exposure to 25 µM acetochlor.•Concentrations of 100 and 1000 nM acetochlor increased the mean time spent in the dark zone, indicating anxiolytic behavior.