Glyphosate (GLY) is a non-selective herbicide that works by preventing the synthesis of proteins in plants. GLY exposure in aquatic organisms can cause oxidative stress, cell damage, developmental impacts, physiological and behavioural changes, plant death, reduced biodiversity, bioaccumulation, and synergetic effects. In this study, we assessed the effects of the relevant concentrations of GLY (100ppb-300ppb) on young Penaeus vannamei through biochemical endpoints: tissue damaging enzymes (GOT and GPT), antioxidant enzymes (SOD), and defence enzymes were measured.
Glyphosate 41% S.L. (I.P.A salt, 500ml) manufactured by Monsanto India Limited, Mumbai, India was used in this study. GLY was purchased at Theni district, Tamil Nadu. The 41% GLY was used to prepare 100% stock and serially diluted to different concentrations (10ppm, 20ppm, 30ppm, 40ppm, and 50ppm). The effect of GLY exposure was examined to assess the oxidative stress and biotransformation of post larvae PL12 stage P. vannamei collected from a commercial farm near Pattukkottai, Thanjavur District, Tamil Nadu, and acclimatized for one day before the experiment started. After measuring body length (1.760±0.197cm) using Vernier caliper and weight (0.629±0.081g) they were divided into six groups (n=25/tank). Water quality was maintained at pH 7.8, salinity of 28-32ppt and temperature of 27-28ºC throughout the study. Tissue samples were collected every 6hr and the hepatopancreas removed for enzymatic reactions.
After 50 days of GLY exposure, the level of alkaline phosphatase assay (ALP) increased, peaking at 150-200 ppb, they subsequently fell. In contrast, the SOD activity reached a maximum between 250 and 300 ppb. The activity of tissue damaging enzymes GOT and GPT was increased, rising at concentrations of 250 ppb and 300 ppb. The activity of Cytochrome P450 (CYP 450 1A1) also increased at 250-300 ppb concentrations.
Overall, there was increased levels of tissue damaging enzymes, antioxidant enzymes, and defence enzymes. Hepatic tissues of P. vannamei exposed to commercial herbicide formulations containing GLY exhibit altered enzyme activities, suggesting an adaptive and regulated response against herbicide toxicity.