Effect of clomazone herbicide on biochemical and histological aspects of silver catfish (Rhamdia quelen) and recovery pattern.

The effects of the herbicide, clomazone, on acetylcholinesterase (AChE), catalase and TBARS formation in teleost fish (Rhamdia quelen) were studied. The fish were exposed to 0.5 or 1.0 mg L(-1) of clomazone for 12, 24, 48, 96 and 192 h. After 192 h of exposure period, fish were transferred to clean water and kept in the same for 192 h to study the recovery response. Same parameters as that of exposure period were assayed after 96 and 192 h of recovery period. Specific AChE activity was reduced in the brain and muscle after treatments, reaching a maximum inhibition of 47% in the brain and 45% in the muscle after 12h of exposure. Fish exposed to clomazone increased TBARS production in the liver for all exposure periods. The brain presented elevated TBARS levels after 12, 24 and 48 h, but after 96 and 192 h, these levels decreased. The decrease of TBARS levels persisted in brain tissue after 96 h of recovery and returned to the control value after 192 h in clean water. Catalase activity was reduced for all periods of exposure. Histological analysis showed vacuolation in the liver after herbicide exposure. Some of the alterations observed were completely restored after recovery period.

Effect of glyphosate herbicide on acetylcholinesterase activity and metabolic and hematological parameters in piava (Leporinus obtusidens).

In this study, teleostean fish Leporinus obtusidens (piava) were exposed to different concentrations of Roundup, a glyphosate (acid equivalent) herbicide: 0 (control), 3, 6, 10, and 20 mg/L for 96 h (short-term). Acetylcholinesterase (AChE) activity was verified in brain and muscle tissues. Metabolic parameters in the liver and muscle (lactate, glycogen, glucose, protein, and ammonia), as well as some hematological parameters, were determined. Unexposed fish exhibited significantly higher brain AChE activity when compared to that of the muscle (P<0.05) (13.8+/-0.76 and 6.1+/-1.31 micromol/min/g protein, respectively). Results indicated that AChE activity significantly decreased in the brain of fish exposed to all glyphosate concentrations tested, but in the muscle this parameter was not altered. In addition, fish exposed to all glyphosate concentrations showed a significant increase in hepatic glycogen and glucose, but a significant reduction in muscle glycogen and glucose. Lactate and protein of fish exposed to all glyphosate concentrations presented a significant decrease in the liver, but did not change significantly in the muscle. Levels of ammonia in both tissues increase in fish at all glyphosate concentrations. Exposure to this herbicide produced a decrease in all hematological parameters tested. These results indicate that AChE activity as well as metabolic and hematological parameters may be good early indicators of herbicide contamination in L. obtusidens.

Effects of clomazone herbicide on hematological and some parameters of protein and carbohydrate metabolism of silver catfish Rhamdia quelen.

The effects of clomazone (0.5 and 1.0 mg/L) according to nominal concentrations used in paddy rice fields (0.4-0.7 mg/L) on protein and carbohydrate metabolism and haematological parameters were evaluated in silver catfish (Rhamdia quelen) after 12, 24, 48, 96 and 192 h of exposure with a recovery period of 96 and 192 h. Liver glycogen increased significantly (P<0.05) in all periods and concentrations tested. The maximum glycogen increase reaches 250% after 12h of exposure. Muscle glycogen reduced significantly after 24, 48, 96 and 192 h for both clomazone concentrations (P<0.05). Significantly elevated plasma glucose values (P<0.05) and variation in glucose in the liver and muscle of exposed fish were observed. Muscle lactate levels increased after 12, 24 and 48 h of clomazone exposure (22-67%), but reduced in the liver (P<0.05). Protein levels were enhanced in the liver and white muscle, except at 96 and 192 h of exposure, whereas it increased in the plasma in the period from 48 to 96 h (P<0.05). Alanine aminotransferase (ALT) and aspartate aminotransferase (AST) activities were significantly elevated in the plasma (P<0.05). In the liver, ALT increased after 24 h, while AST activity was enhanced only after 12 h of exposure. Hematocrit contents were reduced after 96 and 192 h of exposure. Most of the metabolic disorders observed did not persist after the recovery period, except for the liver AST and ALT activity. Clomazone concentrations used in this study appear safe to fish, Rhamdia quelen, because overall parameters can be recovered after 96 and 192 h in clean water. ALT and AST activity may be an early biomarker of clomazone toxicity.

Effects of the herbicides clomazone, quinclorac, and metsulfuron methyl on acetylcholinesterase activity in the silver catfish (Rhamdia quelen) (Heptapteridae).

Fingerlings of the silver catfish (Rhamdia quelen) were exposed to three herbicides widely used in rice culture in south Brazil: clomazone, quinclorac, and metsulfuron methyl. LC50 was determined and acetylcholinesterase (AChE) activity was evaluated in brain and muscle tissue of fish exposed to different herbicide concentrations after 96h (short term). The LC50 value (nominal concentration) was 7.32 mg/L for clomazone and 395 mg/L for quinclorac, but was not obtained for metsulfuron-methyl since all fingerlings survived the highest concentration of 1200 mg/L. Brain and muscle AChE activity in unexposed fish were 17.9 and 9.08 micromol/min/g protein, respectively. Clomazone significantly inhibited AChE activity in both tissues, achieving maximal inhibition of about 83% in brain and 89% in muscle tissue. In contrast, quinclorac and metsulfuron methyl caused increases in enzyme activity in the brain (98 and 179%, respectively) and inhibitions in muscle tissue (88 and 56%, respectively). This study demonstrated short-term effects of exposure to environmentally relevant concentrations of rice field herbicides on AChE activity in brain and muscle tissue of silver catfish.