Abstract
Rhamdia quelen (silver catfish) and Leporinus obtusidens (piava) were exposed to a commercial formulation Roundup(r), a glyphosate-based herbicide at concentrations of 0.2 or 0.4 mg/L for 96 h. The effects of the herbicide were analyzed on the alanine aminotransferase (ALT) and aspartate aminotransferase (AST) activities and glucose in plasma, glucose and protein in the mucus layer, nucleotide hydrolysis in the brain, and protein carbonyl in the liver. The parameters were chosen, owing to a lack of information concerning integrated analysis, considering oxidative damage parameters, liver damage, and effects on the mucus layer composition and triphosphate diphosphohydrolase (NTPDase) activities. Plasmatic glucose levels were reduced in both species, whereas the transaminase activities (ALT and AST) increased after exposure to the herbicide. Herbicide exposure increased protein and glucose levels in the mucus layer in both species. There was a reduction in both NTPDase and ecto-5'-nucleotidase activity in the brain of piava, and increased enzyme activity in silver catfish at both concentrations tested. The species showed an increase in protein carbonyl in the liver after exposure to both concentrations of the glyphosate. Our results demonstrated that exposure to Roundup(r) caused liver damage, as evidenced by increased plasma transaminases and liver protein carbonyl in both of the fish species studied. The mucus composition changed and hypoglycemia was detected after Roundup(r) exposure in both species. Brain nucleotide hydrolysis showed a different response for each fish species studied. These parameters indicated some important and potential indicators of glyphosate contamination in aquatic ecosystems.
Highlights
When present in an aquatic system, chemicals such as herbicides may contaminate fish, plants, and other animals by inducing secondary effects, sometimes owing to indirect contamination (Fonseca et al, 2008)
The plasmatic glucose levels became reduced in the silver catfish after exposure to glyphosate at both 0.2 and 0.4 mg/L when compared to the control group (Table 1)
The glucose and protein levels exhibited a significant increase in the mucus layer of both silver catfish and piava that were exposed to both concentrations of the glyphosate herbicide, when compared to control group (Table 2)
Summary
When present in an aquatic system, chemicals such as herbicides may contaminate fish, plants, and other animals by inducing secondary effects, sometimes owing to indirect contamination (Fonseca et al, 2008). The commercial formulation of glyphosate herbicides contains the isopropylamine (IPA) salt of glyphosate 480 g/L, water, and polyethoxylated tallow amine surfactant (POEA) (Jiraungkoorskul et al, 2002). Numerous commercial formulations with glyphosate as the active ingredient have become popular worldwide, owing to their effective action, low toxicity to mammals, and reduced cost to the farmer (Corbera et al, 2005). Glyphosate and its principal degradation product, aminomethylphosphonic acid (AMPA), have been found in natural water sources in many countries (Coupe et al, 2012). The glyphosate distribution between water, soil, and sediment is influenced by some factors, and it is very difficult to predict the exact environmental behaviors that influence the distribution of the active ingredient or degradation product (AMPA); for example, glyphosate levels measured in April ranged from 0.5 to 4 μg/L with AMPA ranging from 0.5 to 2.3. In August of the same year, the glyphosate dispersion was between 0.5 and 2.3 μg/L and AMPA ranged from 1.7 to 3.6 μg/L (Aparicio et al, 2013)
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