Acute toxicity and effects of the Roundup Transorb®, a glyphosate-based herbicide, on freshwater teleost matrinxã, Brycon amazonicus

The aim of this study was to evaluate the susceptibility of the Neotropical freshwater fish matrinxã, Brycon amazonicus, exposed to Roundup Transorb®, a newer commercial formulation 50% stronger than the ordinary mixtures and with a new technology for quicker absorption and faster translocation. The median lethal concentration (96 h-LC50) was determined, and the effects of a sublethal concentration on oxidative stress biomarkers were evaluated in the liver, gills, white muscle, and heart. During the acute toxicity test, fish mortality progressively increased with RT concentration along with behavioral abnormalities were detected. The calculated 96 h-LC50 value of RT was found as 1.21 mg/L. Fish exposed to 0.5 mg/L of RT (40% of 96 h-LC50) showed a significant increase in the hepatic somatic index (HSI) with a concomitant decrease in Fulton's condition factor (K). The sublethal exposure also induced significant increases (p < 0.05) in the hepatic lipid peroxidation (LPO) levels, reduced glutathione (GSH) content, and catalase (CAT) activity, with a concomitant decrease in the glutathione S-transferase (GST) activity. In the gills, RT exposure induced significant increases in the GST activity, GSH and LPO levels, whereas CAT activity was inhibited. RT also induced CAT and GST activities together with the content of GSH and LPO levels in the white muscle. On the other hand, significant decreases in the CAT and GST activities were detected in the heart with a marked increase in the GSH content and no changes in LPO levels. Therefore, the exposure to 0.5 mg/L of RT induced oxidative stress in the liver, gills and white muscle with tissue-specific responses related to antioxidant defenses. This study demonstrated that B. amazonicus is sensitive to Roundup Transorb® at sublethal and environmentally relevant concentrations, even at short-term exposures. The use of Roundup Transorb® should be carefully monitored due to its adverse non-target impacts.