Use of biometric, hematologic, and plasma biochemical variables, and histopathology to assess the chronic effects of the herbicide prometryn on Common Carp

Developmental toxicity of prometryn induces mitochondrial dysfunction, oxidative stress, and failure of organogenesis in zebrafish (Danio rerio)

Prometryn, 2-methylthio-4,6-bis(isopropylamino)-1,3,5-triazine, is a selective thiomethyl triazine herbicide widely used to control unwanted weeds and harmful insects by inhibiting electron transport in target organisms. Despite having various advantages, herbicides pose as a major threat to the environment and human health due to persistent contamination, bioaccumulation, and damage to non-target organisms. In this study, the developmental toxicity of 5, 10, and 20 mg/L prometryn in zebrafish (Danio rerio) embryos was evaluated and compared to that of the solvent control for 96 h. Several transgenic zebrafish models (fli1a:eGFP, flk1:eGFP, olig2:dsRed and L-fabp:dsRed) were visually assessed to detect fluorescently tagged genes. Results showed that prometryn shortened body length, and induced yolk sac, heart edema, abnormal heart rate, and loss of viability. Fluorescence microscopy revealed that prometryn exposure caused defects in organ development, reactive oxygen species accumulation, and apoptotic cell death. Mitochondrial bioenergetics were also evaluated to determine the effect of prometryn on the electron transport chain activity and metabolic alterations. Prometryn was found to interfere with mitochondrial function, ultimately inhibiting energy metabolism and embryonic development. Collectively, our findings suggest that prometryn is a potential contaminate for non-target sites and organisms, especially aquatic, and emphasize the need to consider the toxic effects of prometryn.

Blood biomarkers as diagnostic tools: An overview of climate-driven stress responses in fish

Global climate change due to anthropogenic activities affects the dynamics of aquatic communities by altering the adaptive capacities of their inhabitants. Analysis of blood provides valuable insights in the form of a comprehensive representation of the physiological and functional status of fish under various environmental and treatment conditions. This review synthesizes currently available information about blood biomarkers used in climate change induced stress responses in fish. Alterations in informative blood-based indicators are used to monitor the physiological fitness of individual fishes or entire populations. Specific characteristics of fish blood, such as serum and plasma metabolites, cell composition, cellular abnormalities, cellular and antioxidant enzymes necessitate adapted protocols, as well as careful attention to experimental designs and meticulous interpretation of patterns of data. Moreover, the sampling technique, transportation, type of culture system, acclimation procedure, and water quality must all be considered for valid interpretation of hemato-biochemical parameters. Besides, blood collection, handling, and storage time of blood samples can all have significant impacts on the results of a hematological analysis, so it is optimal to perform hemato-biochemical evaluations immediately after blood collection because long-term storage can alter the results of the analyses, at least in part as a result of storage-related degenerative changes that may occur. However, the scarcity of high-throughput sophisticated approaches makes fish blood examination studies promising for climate-driven stress responses in fish.

Acute toxicity, bioaccumulation and elimination of prometryn in tilapia (Oreochromis niloticus)

Tilapia juvenile (Oreochromis niloticus) (mean weight 50.00 ± 10.00 g) were aqueous exposed to different concentrations of the herbicide prometryn to investigate its acute toxicity, bioaccumulation and uptake and elimination rates. First, a 96-h acute toxicity test was carried out. The resulting 96 h LC₅₀ was 5.49 mg/L, and the 96 h LC₁₀ was 5.02 mg/L. Then, fish were exposed to 0.55 mg/L (1/10 96 h LC₅₀) and 0.055 mg/L (1/100 96 h LC₅₀) of prometryn solution for 28 days, followed by 14 days of elimination in clean groundwater. The result shows that in both water and tissues, prometryn concentrations fluctuated during the exposure period, indicating that steady state was not reached. The bioaccumulation of prometryn was the highest in liver, followed by gill, muscle and blood. The accumulated concentration levels in various tissues were always higher in the high concentration compared to the low concentration. The highest accumulated concentration of prometryn in various tissues in the 0.055 mg/L treatment were for muscle: 0.136 ± 0.0616 mg/kg (1 d), liver: 3.74 ± 2.95 mg/kg (7 d), gill: 0.971 ± 1.45 mg/kg (1 d) and blood: 0.0716 ± 0.0669 mg/kg (22 d). In the 0.55 mg/L treatment, the highest levels were for muscle: 1.27 ± 0.284 mg/kg (1 d), liver: 16.9 ± 12.7 mg/kg (7 d), gill: 8.11 ± 3.02 mg/kg (1 d) and blood: 0.751 ± 0.0775 mg/kg (22 d). The highest bioconcentration factor (BCF) of 93.1 was observed in the liver when exposed to the low concentration. Besides, for other tissues, the highest BCF were for muscle: 5.76, gill: 32.3 and blood: 2.91, all observed in the 0.55 mg/L treatment. Most of the accumulated prometryn was removed from all tissues within 24 h after the organisms were transferred to clean water. However, management of using prometryn in China aquaculture should be improved to prevent possible ecotoxicological effects and ensure food safety.

Demonstration of an aggregated biomarker response approach to assess the impact of point and diffuse contaminant sources in feral fish in a small river case study

The assessment of the exposure of aquatic wildlife to complex environmental mixtures of chemicals originating from both point and diffuse sources and evaluating the potential impact thereof constitutes a significant step towards mitigating toxic pressure and the improvement of ecological status. In the current proof-of-concept study, we demonstrate the potential of a novel Aggregated Biomarker Response (ABR) approach involving a comprehensive set of biomarkers to identify complex exposure and impacts on wild brown trout (Salmo trutta fario). Our scenario used a small lowland river in Germany (Holtemme river in the Elbe river catchment) impacted by two wastewater treatment plants (WWTP) and diffuse agricultural runoff as a case study. The trout were collected along a pollution gradient (characterised in a parallel study) in the river. Compared to fish from the reference site upstream of the first WWTP, the trout collected downstream of the WWTPs showed a significant increase in micronucleus formation, phase I and II enzyme activities, and oxidative stress parameters in agreement with increasing exposure to various chemicals. By integrating single biomarker responses into an aggregated biomarker response, the two WWTPs' contribution to the observed toxicity could be clearly differentiated. The ABR results were supported by chemical analyses and whole transcriptome data, which revealed alterations of steroid biosynthesis and associated pathways, including an anti-androgenic effect, as some of the key drivers of the observed toxicity. Overall, this combined approach of in situ biomarker responses complemented with molecular pathway analysis allowed for a comprehensive ecotoxicological assessment of fish along the river. This study provides evidence for specific hazard potentials caused by mixtures of agricultural and WWTP derived chemicals at sublethal concentrations. Using aggregated biomarker responses combined with chemical analyses enabled an evidence-based ranking of sites with different degrees of pollution according to toxic stress and observed effects.

Does the Site of Blood Collection in Fish Affect Haematological and Blood Biochemical Results?

The values of haematological and selected blood plasma biochemical parameters of juvenile common carp (Cyprinus carpio Linnaeus, 1758) were compared between blood samples taken from caudal vein and heart to evaluate the influence of blood sampling body site on the obtained results in two groups of fish of different blood sampling order: I – first by caudal and then by cardiac puncture, II – first by cardiac and then by caudal puncture. The obtained results revealed statistically significant (p<0.05) differences only in group I where red blood cell (RBC) count was higher in caudal vein blood, while haematocrit (Ht) value, mean corpuscular volume (MCV), mean corpuscular haemoglobin (MCH), total protein (TP) concentration, and magnesium (Mg) level were higher in cardiac blood samples. No statistically significant differences occurred in white blood cell (WBC) count, differential leukocyte count or erythrocyte morphology based on stained blood smears. The obtained results showed that blood sampling body site may affect the results of haematological and plasma biochemical analyses.

The effect of chronic exposure to chloridazon and its degradation product chloridazon-desphenyl on signal crayfish Pacifastacus leniusculus

The effects of chloridazon (Ch) and its metabolite chloridazon-desphenyl (Ch-D) at the environmentally relevant concentrations of 0.45 µg/L and 2.7 µg/L on signal crayfish Pacifastacus leniusculus were assessed in a 30-day exposure followed by a 15-day depuration period. Locomotion, biochemical haemolymph profile, oxidative and antioxidant parameters, and histopathology were evaluated. Crayfish exposed to Ch at 0.45 µg/L and 2.7 µg/L showed significantly (p < 0.01) higher CAT activity and GSH level in hepatopancreas and gill compared to controls. The concentration of Ch at 2.7 µg/L was associated with significantly (p < 0.01) higher levels of GLU, LACT, ALT, AST in haemolymph compared to controls. Chloridazon-desphenyl exposure at both tested concentrations caused significantly higher (p < 0.01) GLU, LACT, ALT, AST, NH₃, and Ca in haemolymph; lipid peroxidation (TBARS) levels in hepatopancreas; and CAT activity and GSH level in hepatopancreas and gill. Alterations of structure including focal dilatation of tubules, increased number of fibrillar cells, and haemocyte infiltration in the interstitium were observed with 2.7 µg/L Ch and with both Ch-D exposures. Locomotion patterns did not vary significantly among groups. A 15-day recovery period was insufficient to restore normal physiological parameters in exposed groups. Chloridazon and its metabolite Ch-D exerts harmful effects on crayfish.

Blood biomarkers of herbicide, insecticide, and fungicide toxicity to fish-a review

Pesticides are widely used in the world agriculture, and they may adversely affect non-target organisms, including fish. The present 2000-2019 literature review summarizes hematological and blood biochemical effects of various herbicides, insecticides, and fungicides in fish. The observed changes usually indicate anemia and inflammation, as well as hyperglycemia, hypoproteinemia, increase in cortisol concentration and activities of hepatic aminotransferases that are typical for intoxication and stress. Other changes that are also sometimes observed such as increase in red blood parameters indicate compensatory response. The often-noted symptoms of immunosuppression show an adverse effect of pesticides on immune system and possible immunosuppression. Pathophysiological changes in fish induced by pesticides depend on many factors, such as active compound and its concentration, exposure duration, fish species, environmental conditions, etc. Hematological and blood biochemical parameters appear to be useful biomarkers for evaluation of physiological state of fish exposed to pesticides; however, they are not specific markers of intoxication.

Impact of acute handling stress, anaesthesia, and euthanasia on fish plasma biochemistry: implications for veterinary screening and metabolomic sampling

Impacts of pre-sampling practices on fish plasma biochemistry may bias the outcome of a study if not considered within the general sampling strategy. Acute handling stresses can be imposed on fish during capture, and it is common practice to immobilise fish via sedation prior to obtaining blood samples for non-lethal extraction purposes, and/or to reduce stress, pain, or suffering before being euthanised. We investigated these potential influences using a Chinook salmon model (Oncorhynchus tshawytscha) by measuring levels of 119 biochemical targets comprising ions, metabolites, and enzymes in plasma. Multivariate analyses showed that 2 min of confinement with mild handling manipulation led to a significant departure from baseline metabolism, which was further exasperated during a prolonged 5-min challenge. These changes were characterised by a disruption in osmoregulation, a switch towards anaerobic metabolism, and shifts in ammonia recycling, among others. Sedation of fish with clove oil and AQUI-S® had major impacts on plasma biochemical profiles, with alterations signalling changes in glycolytic metabolism, respiratory modes, carbon flux through the TCA cycle, and lipid compartmentalisation. Sedation also enhanced levels of plasma amino acids, revealing a key difference between responses to handling stress and sedation. These results demonstrate that pre-harvest practices should be carefully managed during fish sampling for biochemical/metabolomic-based analyses, and if manipulations are essential, they should be standardised.

Enhanced degradation of prometryn and other s-triazine herbicides in pure cultures and wastewater by polyvinyl alcohol-sodium alginate immobilized Leucobacter sp. JW-1

The s-triazine herbicides, such as prometryn, have been widely used in agriculture and have raised much public concern over their contamination of water and soil. Leucobacter sp. JW-1 cells were immobilized in polyvinyl alcohol‑sodium alginate (PVA-SA) beads and then used to degrade prometryn. Orthogonal array experiments showed that the optimal immobilization conditions of PVA-SA immobilized Leucobacter sp. JW-1 beads (PSLBs) were 3% JW-1 cells (w/v, wet weight), 10-12% (w/v) PVA, 2-3% (w/v) calcium chloride, and an immobilization time of 24-36h. The PSLBs were more tolerance to pH, temperature and salinity changes than free JW-1 cells and were stable and effective for degrading prometryn through six reuse cycles without losing their degradation capacity. The half-life of prometryn degradation by PSLBs at 100mgL^-1 in pesticide plant wastewaters were 1.1-6.9h. The rate constants of prometryn degradation by PSLBs in wastewaters ranged from 304 to 576mgL^-1day^-1, which were approximately 1.25-118 times those of degradation by free JW-1 cells. The PSLBs degraded 99.9% of atrazine, 99.9% of ametryn, 97.8% of propazine, 100.0% of simetryn, 77.9% of simazine, 98.9% of terbuthylazine, 95.2% of prometon, 98.9% of atraton, and 31.6% of terbumeton at an initial concentration of 50mgL^-1 of each herbicide in 2days. This study indicates that PSLBs persistently biodegrade s-triazine herbicides better than JW-1 free cells, and can be an efficient, safe and reusable biomaterial for the removal of s-triazine herbicides from contaminated sites.

Effects of the terbuthylazine metabolite terbuthylazine-desethyl on common carp embryos and larvae

Toxicity of terbuthylazine-desethyl to embryos and larvae of common carp (Cyprinus carpio) was assessed. Based on mortality, the lethal concentration of terbuthylazine-desethyl was estimated to be 31days LC50=441.6μg/L. Carp exposed to terbuthylazine-desethyl at 1800μg/L exhibited lower weight and length at 7days of exposure compared to the control group. By day 20, carp exposed to 900μg/L terbuthylazine-desethyl showed lower weight and length compared to control group. Terbuthylazine-desethyl in concentrations (180, 900, and 1800μg/L) caused delay in ontogenetic development. Total superoxide dismutase activity was significantly lower in all exposed groups. Exposure to 180 and 900μg/L terbuthylazine-desethyl was associated with alteration of the caudal kidney tubular system including peritubular dilatation detachment of epithelial cells from the basal lamina, and focal autolytic disintegration of the tubular epithelia. Chronic terbuthylazine-desethyl exposure affected survival, growth, ontogenetic development, and the antioxidant system and caused pathological changes to the caudal kidney.

Toxicity of environmental Gesagard to goldfish may be connected with induction of low intensity oxidative stress in concentration- and tissue-related manners

Prometryn is a selective herbicide commonly used in agriculture as the commercial preparation, Gesagard. Goldfish (Carassius auratus) exposure for 96h to 0.2, 1, or 5mgL(-1) Gesagard 500FW (corresponding to 0.1, 0.5, and 2.5mgL(-1) of prometryn) on indices of oxidative stress (lipid peroxides, protein carbonyls, and thiol content) and activities of antioxidant and related enzymes in gills, liver, and kidney was studied. Gills appeared to be the most resistant to Gesagard treatment, reacting to only the highest concentration of herbicide with enhanced levels of low molecular mass thiols and activities of glutathione S-transferase (GST) and glutathione reductase. Goldfish exposure to 0.2-5mgL(-1) Gesagard resulted in enhancement of carbonyl protein level and activity of superoxide dismutase (SOD), but reduced the lipid peroxide (LOOH) content and activity of glutathione peroxidase in liver. Kidney appeared to be the main target organ of Gesagard toxicity, showing the greatest number of parameters affected even under low concentrations of herbicide. An increase in the content of L-SH and activity of SOD was accompanied with decreased activities of catalase, GST, and glucose-6-phosphate dehydrogenase and reduced levels of LOOH in kidney of Gesagard treated fish. The treatment also induced various histological changes in goldfish liver and kidney which could be related to their dysfunction. The present study indicates that Gesagard induced oxidative stress of differing intensities in the three goldfish tissues and demonstrated that kidney would be the best target organ to analyze, reveal, and monitor Gesagard effects on fish.

Effects of prometryne on early life stages of common carp (Cyprinus carpio L.)

Toxicity of prometryne to early life stages of common carp was assessed. On the basis of accumulated mortality in the experimental groups lowest observed-effect concentration (LOEC) was estimated as 1100 µg/l; and no observed-effect concentration (NOEC) was 850 µg/l. Fulton's condition factor was significantly lower than in controls in fish exposed to 4000 µg/l after 7, 14, and 21 days. By day 14, fish exposed to 4000 µg/l prometryne showed significantly lower mass and total length compared to controls. Fish exposed the 1200 and 4000 µg/l showed delay in development, severe hyperaemia in gill, liver, and caudal and cranial kidney. Subchronic prometryne exposure of early-life stages of common carp at concentrations of 1200 and 4000 µg/l affected their survival, growth rate, early ontogeny, and histology.

Effect of chronic exposure to prometryne on oxidative stress and antioxidant response in red swamp crayfish (Procambarus clarkii)

The aim of the study was to investigate effects of the triazine herbicide prometryne on red swamp crayfish on the basis of oxidative stress, antioxidant indices in hepatopancreas and muscle, and histopathology of hepatopancreas. Crayfish were exposed to prometryne concentrations of 0.51 μg L⁻¹, 0.144 mg L⁻¹, and 1.144 mg L⁻¹ for 11 and 25 days. Indices of oxidative stress (thiobarbituric acid reactive substances (TBARS)), and antioxidant parameters (superoxide dismutase (SOD), catalase (CAT), and glutathione reductase (GR)) in crayfish muscle and hepatopancreas were measured. Chronic exposure to prometryne did not showed the impact of oxidative damage to cells. Changes activity of the antioxidant enzymes SOD, CAT, and GR were observed in all tested concentrations to prometryne for 11 and 25 days (P < 0.01) as compared with the control group. We did not see any differences in histopatological examination to hepatopancreas. Prolonged exposure of prometryne did not result in oxidative damage to cell lipids and proteins, but it led to changes in antioxidant activity in crayfish tissues. Changes in antioxidant systems were also observed in the environmental prometryne concentration of 0.51 μg L⁻¹. The results suggest that antioxidant responses may have potential as biomarkers for monitoring residual triazine herbicides in aquatic environments.