Effect of Ascorbic Acid on Glyphosate-Induced Residues in Muscles of Juvenile Catfish (Clarias gariepinus)

Aims: This study focused on acute toxicity of Glyphosate and its residual effect on muscles of juvenile Clarias gariepinus fish, as well as on L-ascorbic acid (vitamin C) treatment of induced glyphosate residues in muscles of the fish to prevent bioaccumulation of glyphosate and subsequent toxicity when consumed by humans.

Study Design: Latin square.

Place and Duration of Study: Department of Fisheries and Aquaculture Management, Nnamdi Azikiwe University Awka. Nigeria, between December 2018 and April 2019.

Methodology: Forty-eight hours acute toxicity tests were initially carried out on eight juveniles of C. gariepinus of mean weight 41.50±1.35g and length 20.75±0.43cm to determine LC50 of both glyphosate (Delsate®) and Vitamin C (Kepro®). Thereafter the fish were exposed for 91 days to sub-lethal concentrations of 0.0 (control), 5.0, 10.0 and 15mgL-1 glyphosate; and later treated separately with 50 and 100 mgL-1 of vitamin C for 7 days. A second set of fish was exposed to glyphosate and vitamin C concurrently for 91 days. Glyphosate residues in the muscles of the fish were determined by gas chromatography.

Results: The LC50 of Delsate® and Kepro® were 75 and 175 mgL⁻¹ respectively. There was significant increase (P<.05) in mean values of glyphosate retained in muscles of fish exposed to glyphosate for 91days when compared with the control. Seven days post-exposure treatment with vitamin C resulted in significant decrease (P<.05) in glyphosate residues in fish muscles; with 100mgL-1 of vitamin C being more effective than the 50 mgL⁻¹. The second set-up did not show significant therapeutic effects on the muscles of C. gariepinus.

Conclusion: This work has determined the LC50 of glyphosate and Vitamin C. Glyphosate residues in muscles of exposed fish could be rendered safe for human consumption by treatment of exposed fish in water bath containing with Vitamin C. Our on-going research is on histopathological alterations in tissues of glyphosate-exposed C. gariepinus juvenile fishes.