Acute toxicity of an organophosphate insecticide sumithion to striped catfish Pangasianodon hypophthalmus

Rotenone-induced cell apoptosis via endoplasmic reticulum stress and PERK-eIF2α-CHOP signalling pathways in TM3 cells

Rotenone (ROT), a widely used natural pesticide, has an uncertain effect on reproductive toxicity. In this study, we used 20 mice distributed randomly into four groups, with each group receiving ROT doses of 0, 2, 4, and 8 mg/kg/day for 28 days. The results demonstrated that ROT induced significant testicular damage, including impaired spermatogenesis, inhibition of testosterone synthesis, and apoptosis of Leydig cells. Additionally, ROT disrupted the normal ultrastructure of the endoplasmic reticulum (ER) in testicular tissue, leading to ER stress in Leydig cells. To further explore whether ROT-induced apoptosis in Leydig cells is related to ER stress, the mouse Leydig cell line (TM3 cells) was treated with ROT at 0, 250, 500, and 1000 nM. ROT inhibited TM3 cell viability, induced cytotoxicity, and reduced testosterone content in the culture supernatants. Furthermore, ROT treatment triggered apoptosis in TM3 cells by activating ER stress and the PERK-eIF2α-CHOP signalling pathway. Pre-treatment of TM3 cells exposed to ROT with the ER stress inhibitor 4-phenylbutyric acid (4-PBA) alleviated these effects, decreasing apoptosis and preserving testosterone levels. Further intervention with the PERK inhibitor GSK2606414 reduced ROT-induced apoptosis and testosterone reduction by inhibiting PERK activity. In summary, ROT-induced male reproductive toxicity is specifically driven by apoptosis, with the PERK-eIF2α-CHOP signalling pathway activated by ER stress playing a crucial role in the apoptosis of Leydig cells triggered by ROT.

Size dependent ingestion and effects of microplastics on survivability, hematology and intestinal histopathology of juvenile striped catfish (Pangasianodon hypophthalmus)

Microplastic pollution is drastically increasing in aquatic ecosystems and it is assumed that different sizes of microplastics have diverse impacts on the physiology of aquatic organisms. Therefore, this study was intended to examine the ingestion and size specific effects of polyamide microplastic (PA-MP) on different physiological aspects such as growth, feed utilization, survivability, blood parameters and intestinal histopathology of juvenile striped catfish (Pangasianodon hypophthalmus). In a 28-day exposure, the fish were fed with different sized PA-MP with a concentration of 500 mg per kg of feed in order to simulate highly microplastic contaminated environment. Three different treatments were set for this experiment i.e. T1, 25-50 μm (smaller microplastic); T2, 300 μm-2 mm (larger microplastic); T3, (mixed) including a control (C); each had three replicates. The highest ingestion was recorded in the gastrointestinal tract (GIT) of fish exposed to smaller PA-MP treatments (T1 followed by T3). The results also showed compromised weight gain (WG; g), specific growth rate (SGR; %/day) and feed conversion ratio (FCR) with the exposure of PA-MP. Besides, survivability significantly reduced among treatments with the ingestion of smaller sized microplastic and found lowest in T1 (65.0 ± 5.0). In addition, the presence of PA-MP in feed negatively affected the concentration of hemoglobin and blood glucose. Similarly, smaller PA-MP caused most erythrocytic cellular and nuclear abnormalities; found highest in T1 that significantly different from other treatments (p < 0.05). Various histopathological deformities were observed in fish fed with PA-MP incorporated feed. The principal component analysis (PCA) showed that the toxicity and stress imparted by smaller PA-MP affected the survivability and blood parameters where larger PA-MP caused mild to severe abnormalities. Based on eigenvector values, the major abnormalities in intestine included occurrence of epithelium columnar degeneration (ECD: 0.402; PC1), hyperplasia of internal mucosa (HISM: 0.411; PC1), beheading of villi (BV: 0.323; PC1), atrophy of mucosa (AM: 0.322; PC1), tiny vacuoles in apical villi (TV: 0.438. PC2), crypt degeneration (CD: 0.375: PC2) and atrophy of goblet cell (AGC: 0.375; PC2). Therefore, it has been speculated that the size based PA-MP ingestion in the GIT interfered with the digestion and absorption as well as caused deformities that reflected negatively in survivability and hemato-biochemical parameters of juvenile striped catfish.

Effects of chlorpyrifos toxicity on brain, pseudobranchial neurosecretory system and swimming performance of a catfish, Heteropneustes fossilis

In the present study, it was aimed to evaluate the adverse effects of CPF on the histopathology of the optic tectum and cerebellum, pseudobranchial neurosecretory system (PNS), biochemical assays of brain tissue, and locomotory behavior in catfish, Heteropneustes fossilis. The fishes were exposed to an environmentally relevant concentration of 0.09 and 0.192 mg/L of CPF for 7, 15, and 30 d. The CPF toxicity induced degenerative changes with significantly decreased cell size, number, and nucleo-cytoplasmic (N/C) ratio of the PNS; and altered neuro-architectural pattern of optic tectum with degenerative changes in mononuclear and granular cells and necrotic variation in granular and Purkinje cells of the cerebellum. The Acetylcholinesterase (AChE) and Catalase (CAT) activity in the CPF-exposed brain was significantly decreased, whereas Superoxide dismutase (SOD) and Malondialdehyde (MDA) level was significantly increased in comparison with control. In CPF-exposed fishes, the respiratory movements and locomotory behavioral pattern like swimming speed, total distance traveled, time mobile, absolute turn angle, head: distance traveled, maximum speed were significantly decreased, whereas time immobile and time freezing episodes were significantly increased as compared to control fishes. The present study concludes that environmentally relevant concentration of CPF may induce histopathological, biochemical, physiological, and behavioral disturbances in a non-target organism, H. fossilis.

Effect of climate change on hematotoxicity/hepatoxicity oxidative stress, Oncorhynchus mykiss, under controlled conditions

Described as the 'main ecological factor', temperature, strongly affects the physiological stress responses of fish. In order to evaluate the effects of temperature variations on fish culture and food value chain, the present study was designed as a climate change model. Furthermore, the present study provides a theoretical basis for a better understanding of the mechanisms of the environmentally induced changes. In this direction, we examined the blood physiology and oxidative stress responses induced by temperature variation in the rainbow trout, a temperature-sensitive cold-water fish. The obtained results showed that climate changes promoted the inhibited activities' expressions and the development of potential tissue and hematological defense mechanisms against temperature-induced toxic damage. This study showed that climate change could be a subset of the studies on the stress physiology in aquaculture, which can be developed for new experimental designs and research collaborations. Furthermore, it highlights knowledge gaps to guide future research in this emerging field.

A Weak Electricigen-Based Bioelectrochemical Sensor for Real-Time Monitoring of Chemical Pollutants in Water

Electroactive microorganisms are now understood to be abundant across nature, though many are categorized as "weak electricigens" not suitable for reasonable power generation. We report the use of weak electricigens from the natural environment for rapid, real-time water quality monitoring. Using a variety of pesticides as model chemical pollutants, the bioelectrochemical sensor was responsive within minutes at all concentrations tested (0.05-2 ppm) and could be repreatedly used long-term. Due to the prevalence of electroactive microorganisms in the natural environment, such sensors could work in tandem with conventional monitoring methods and may be useful for detecting emerging contaminants.

PARP1 promotes NLRP3 activation via blocking TFEB-mediated autophagy in rotenone-induced neurodegeneration

Rotenone, a widely used pesticide, causes dopaminergic neurons loss and increase the risk of Parkinson's disease (PD). However, few studies link the role of PARP1 to neuroinflammatory response and autophagy dysfunction in rotenone-induced neurodegeneration. Here, we identified that PARP1 overactivation caused by rotenone led to autophagy dysfunction and NLRP3-mediated inflammation. Further results showed that PARP1 inhibition could reduce NLRP3-mediated inflammation, which was effectively eliminated by TFEB knockdown. Moreover, PARP1 poly(ADP-ribosyl)ated TFEB that reduced autophagy. Of note, PARP1 inhibition could rescue rotenone-induced dopaminergic neurons loss. Overall, our study revealed that PARP1 blocks autophagy through poly (ADP-ribosyl)ating TFEB and inhibited NLRP3 degradation, which suggests that intervention of PARP1-TFEB-NLRP3 signaling can be a new treatment strategy for rotenone-induced neurodegeneration.

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.

Effects of heavy metals on fish physiology - A review

The pollution by heavy metals poses a serious threat to the aquatic environment and to the organisms if the concentration of heavy metals in the environment exceeds the safe limits. Due to their non-biodegradable and long persistence nature in the environment, heavy metals cause toxicity in fish by producing oxygen reactive species through oxidizing radical production. In this review, we investigated the effects of heavy metals on fish physiology with special emphasis on hemato-biochemical properties, immunological parameters especially hormones and enzymes, histopathology of different major organs and underlying molecular mechanisms. All those parameters are significantly affected by heavy metal exposure and are found to be important bio-monitoring tools to assess heavy metal toxicity. Hematological and biochemical alterations have been documented including cellular and nuclear abnormalities in different fish species exposed to different concentrations of heavy metals. Major fish organs (gills, liver, kidneys) including intestine, muscles showed different types of pathology specific to organs in acute and chronic exposure to different heavy metals. This study also revealed the expression of different genes involved in oxidative stress and detoxification of heavy metals. In a nutshell, this article shades light on the manipulation of fish physiology by the heavy metals and sought attention in the prevention and maintenance of aquatic environments particularly from heavy metals contaminations.

Dose-Dependent Oxidative Damage in Erythrocytes and Hepatic Tissue of Wistar Rats Concurrently Exposed with Arsenic and Quinalphos: a Subacute Study

Concurrent exposure to a multitude of environmental toxicants pose serious health hazard to humans and animals. The present investigation was conceptualized to determine deleterious effects of concomitant subacute arsenic and quinalphos exposure on antioxidant responses of liver and erythrocytes of Wistar rats. Fifty-four Wistar rats were divided into nine groups with six animals in each. Animals were exposed to either quinalphos (1/100th and 1/10th of LD50) through oral gavage daily or arsenic (50 and 100 ppb) in drinking water alone and in combination for 28 days. While treatment with different toxicants alone also significantly reduced hemoglobin concentration, hepatic biomarkers and levels of antioxidant parameters as compared with control values, concomitant exposure significantly (P < 0.05) elevated levels of hepatic transaminases and alkaline phosphatase. Moreover, along with significant depletion in activities of SOD, CAT, TTH, AChE, and enzymes of glutathione complex, a significant enhancement of lipid peroxidation was also recorded in liver and erythrocytes in co-exposed animals in a dose-dependent manner when compared with exposure to individual toxicant. More severe alterations occurred in hepatic histo-architecture of rats receiving combined treatment as compared with those treated with either toxicant. Results indicated that oxidative damage in erythrocytes was more than that of the liver of rats on concomitant exposure of arsenic and quinalphos in a dose-dependent manner. In nutshell, our results revealed that combined treatment of quinalphos with arsenic potentiated toxic effects of either toxicant on antioxidant machinery of liver and erythrocytes and hepatic histomorphology of exposed Wistar rats.

Impacts of heavy metals on early development, growth and reproduction of fish - A review

Heavy metals pollution causes a threat to the aquatic environment and to its inhabitants when their concentrations exceed safe limits. Heavy metals cause toxicity in fish due to their non-biodegradable properties and their long persistence in the environment. This review investigated the effects of heavy metals on early development, growth and reproduction of fish. Fish embryos/larvae and each developmental stage of embryo respond differently to the intoxication and vary from species to species, types of metals and their mode of actions, concentration of heavy metals and their exposure time. Many of the heavy metals are considered as essential nutrient elements that positively improve the growth and feed utilization of fishes but upon crossing the maximum tolerable limit these metals cause not only a hazard to fish health but also to human consumers and the disruption of ecological systems. Reduced gonadosomatic index (GSI), fecundity, hatching rate, fertilization success, abnormal shape of reproductive organs, and finally failure of reproduction in fish have been attributed to heavy metal toxicity. In summary, this review sheds light on the manipulation of fish physiology by heavy metals and seeks to raise sensitivity to the prevention and control of aquatic environmental contamination, particularly from heavy metals.

Application of fenitrothion on Heteropneustes fossilis causes alteration in morphology of erythrocytes via modifying hematological parameters

In Bangladesh, the extensive use of fenitrothion on crops and in aquaculture ponds inevitably threatens a range of aquaculture species, including fish, owing to stress responses and physiological disturbances. The present study elucidated the potential toxic effects of fenitrothion on the blood biomarkers (haemato-biochemistry and structure of erythrocytes) of stinging catfish (Heteropneustes fossilis), a commercially significant aquaculture species. Fish were exposed to four sub-lethal concentrations (0%, 10%, 20%, and 40% of the 96-h LC50 value) of fenitrothion in triplicate and observed on the 7th, 14th, 21st, and 28th day following exposure. With increasing fenitrothion concentration, blood glucose and white blood cell levels increased significantly; in contrast, hemoglobin, red blood cell, and packed cell volume substantially decreased. However, the mean corpuscular volume and mean corpuscular hemoglobin did not change significantly during the exordial period (0-7 d); although, at a later stage, changes were observed. Frequencies of observed erythrocytic nuclear abnormalities, such as degeneration, bi-nucleus, micronucleus, notch nucleus, and nuclear bridge and erythrocytic cellular abnormalities, such as echinocytes, fusion, elongation, and tear drop morphology increased significantly in a concentration-dependent manner. Differences between the control individuals and those individuals under treatment were considered insignificant for twin cells on the 14th day of exposure. The study showed the pernicious impact of the effects of fenitrothion on H. fossilis through physiological alteration, which is likely to pose challenges for aquaculture production.

Alterations in hematological parameters and the structure of peripheral erythrocytes in Nile tilapia (Oreochromis niloticus) exposed to profenofos

The burden of pesticide use from agricultural intensification lies in the fact that pesticides may end up in aquatic ecosystems and have pernicious effects on non-target organisms, including fish. Different blood biomarkers, including hemato-biochemical indices, erythrocytic nuclear abnormalities (ENA), and erythrocytic cellular abnormalities (ECA), were observed in Nile tilapia (Oreochromis niloticus) after exposure to varying sub-lethal concentrations (0%, 5%, 10%, 20%, and 40% of 96-h LC50) of profenofos at different time intervals (7, 14, 21, and 28 days). The results revealed that glucose and white blood cell (WBC) levels significantly increased, while hemoglobin, red blood cell (RBC), and packed cell volume (PCV) significantly decreased in a time- and concentration-dependent manner. Aberrant erythrocytic morphology-derived ENA, such as nuclear degeneration, micronuclear formation, binuclear development, nuclear budding, and karyopyknosis, significantly increased with time in profenofos-exposed groups compared to controls. Between the treatment and control groups, a significant execution was discerned for teardrop and fusion type ECA. For other cellular aberrations of erythrocytes, including elongated, twin, and spindle, a significant difference appeared only at the beginning of the experiment (day 7). This study concludes that the presence of widely used profenofos in aquatic systems has a pernicious effect on Nile tilapia.

Effects of bisphenol a on hematological, serum biochemical, and histopathological biomarkers in bighead carp (Aristichthys nobilis) under long-term exposure

Bisphenol A (BPA) is one of the highest volume chemicals produced in the world and is frequently used in dental sealants, water bottles, food, and beverage packaging. Due to persistent applications, BPA has become a potential threat to a variety of organisms including public health. In this study, a total of 80 bighead carps were randomly placed in different four groups (A-D). Fish in groups B, C, and D were exposed to BPA @500, 1000, and 1500 μg/L, respectively for 60 days. Fish in group A served as an untreated control group. The body weight was significantly decreased while the absolute and relative weight of different visceral organs increased significantly (p < 0.05) in fish exposed to higher concentration (1500 μg/L) of BPA. Results on proximate analysis showed significantly lower values of crude proteins, lipids, and moisture contents while increased contents of ash in muscles of treated fish. The erythrocyte counts, hemoglobin concentration, lymphocytes, and monocytes significantly decreased while total leukocyte and neutrophil counts significantly increased in treated fish. Results exhibited that different serum biochemistry parameters like serum albumin and total proteins decreased significantly (p < 0.05) while alanine aminotransferase (ALT), aspartate aminotransferase (AST), and alkaline phosphatase (ALP), urea, creatinine, glucose, cholesterol, and lactate dehydrogenase (LDH) increased significantly (p < 0.05) in treated fish. Histopathological ailments like pyknosis, degeneration of glomeruli, increased Bowman's space, ceroid formation in kidneys while ceroid formation, hemorrhages, pyknosis, karyorrhexis, karyolysis, nuclear hypertrophy, and eccentric nuclei were observed in the liver of treated fish. Histological observation of different sections of the brain of treated fish exhibited degeneration of neurons in the cerebellum, lipofuscin deposition, microgliosis, necrotic neurons, inflammatory cells, and hemorrhage. Results on light microscopic observation of different sections of the heart of bighead carp revealed necrosis, inflammatory reaction, neutrophilic myocarditis, and hemorrhages. In conclusion, it is suggested that BPA induces adverse effects on physical, blood-biochemical parameters, and histopathological changes in multiple visceral tissues of exposed fish.

Toxicological effect of sumithion pesticide on the hematological parameters and its recovery pattern using probiotic in Barbonymus gonionotus

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Sumithion induced hematoxicity and their recovery pattern in Barbonymus gonionotus was measured.

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Sumithion induces severe formation and prevalence of micronuclei and significantly (p< 0.05) increased white blood cells.

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Blood glucose, red blood cell, hematocrit, and hemoglobin were found to be decreased after the exposure of sumithion.

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In recovery experiment, the recovery rate was significantly higher in probiotic treated groups than other treatments.

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Fish micronucleus and hematology is an effective biomarker for toxicity test of an organophosphate.

The experiment was conducted to clarify sumithion induced hematoxicity in silver barb (Barbonymus gonionotus) through in vivo exposures (25 % and 50 % of LC₅₀ of sumithion) and subsequent recovery patterns using normal and probiotic treated feed were also assessed. Three treatments each incorporating three replications were used in the experiment for different days (1, 7, 14, 21, and 28). Treatment T₁ was control (0 mg/L), and two concentrations, such as 2.61 mg/L (25 % of 96 h LC₅₀), 5.21 mg/L (50 % of 96 h LC₅₀) were used as Treatment T₂ and T₃, respectively. After 28 days of exposure to pesticide half of the fishes of T₂ and T₃ were reared in sumithion free water with normal (T₂N, T₃N) and probiotic treated feed (T₂P, T₃P). The median lethal concentration (50 %) for 96 h was 10.42 mg/L. In pesticide-treated groups, values of each hematological parameter (blood glucose, red blood cell, hematocrit, and hemoglobin) decreased but prevalence and severity of micronucleus and white blood cells increased significantly (p< 0.05) with concentration and time duration. Other blood indices including mean corpuscular volume (MCV), mean corpuscular hemoglobin (MCH) and mean corpuscular hemoglobin concentration (MCHC) were correspondingly changed in comparison to the control. In the recovery experiment, the silver barb recovered spontaneously, but the recovery rate was significantly higher in probiotic treated groups than normally treated groups in time and duration reliant fashion. In conclusion, persistent sublethal dosages of sumithion caused hematological abnormalities in silver barb. Probiotic supplement can recover the damage but only 28 days of recovery is not enough to recover the total alterations.

Bisphenol A Induces Histopathological, Hematobiochemical Alterations, Oxidative Stress, and Genotoxicity in Common Carp (Cyprinus carpio L.)

Bisphenol A (BPA) is one of the environmental endocrine disrupting toxicants and is widely used in the industry involving plastics, polycarbonate, and epoxy resins. This study was designed to investigate the toxicological effects of BPA on hematology, serum biochemistry, and histopathology of different organs of common carp (Cyprinus carpio). A total of 60 fish were procured and haphazardly divided into four groups. Each experimental group contained 15 fish. The fish retained in group A was kept as the untreated control group. Three levels of BPA 3.0, 4.5, and 6 mg/L were given to groups B, C, and D for 30 days. Result indicated significant reduction in hemoglobin (Hb), lymphocytes, packed cell volume (PCV), red blood cells (RBC), and monocytes in a dose-dependent manner as compared to the control group. However, significantly higher values of leucocytes and neutrophils were observed in the treated groups (P < 0.05). Results on serum biochemistry revealed that the quantity of glucose, cholesterol, triglycerides, urea, and creatinine levels was significantly high (P < 0.05). Our study results showed significantly (P < 0.05) increase level of oxidative stress parameters like reactive oxygen species (ROS) and thiobarbituric acid reactive substances (TBARS) and lower values of antioxidant enzymes (superoxide dismutase (SOD), catalase (CAT), peroxidase (POD) in treated groups (4.5 mg/L and 6 mg/L)) in the brain, liver, gills, and kidneys. Our study depicted significant changes in erythrocytes (pear shaped erythrocytes, leptocytes, microcytes, spherocytes, erythrocytes with broken, lobed, micronucleus, blabbed, vacuolated nucleus, and nuclear remnants) among treated groups (4.5 mg/L and 6 mg/L). Comet assay showed increased genotoxicity in different tissues including the brain, liver, gills, and kidneys in the treated fish group. Based on the results of our experiment, it can be concluded that the BPA exposure to aquatic environment is responsible for deterioration of fish health, performance leading to dysfunction of multiple vital organs.

Probiotics, prebiotics and synbiotics improved the functionality of aquafeed: Upgrading growth, reproduction, immunity and disease resistance in fish

Aquaculture plays an increasingly significant role in improving the sustainability of global fish production. This sector has been intensified with the advent of new husbandry practices and the development of new technology. However, the increasing intensification and indiscriminate commercialized farming has enhanced the vulnerability of cultivated aquatic species to damage from pathogens. In efforts to confront these various diseases, frequent use of drugs, antibiotics, chemotherapeutics, and agents for sterilization have unintentionally added to the risk of transmission of pathogens and harmful chemical compounds to consumers. Some natural dietary supplements are believed to have the potential to offset this setback in aquaculture. Application of bio-friendly feed additives such as probiotics, prebiotics and synbiotics are becoming popular dietary supplements with the potential to not only improve growth performance, but in some cases can also enhance immune competence and the overall well-being of fish and crustaceans. The present review discusses and summarizes the effects of probiotics, prebiotics and synbiotics application on growth, stress mitigation, microbial composition of intestine, immune system and health condition of aquatic animals in association with existing constraints and future perspectives in aquaculture.

Chromium Supplementation in Diet Enhances Growth and Feed Utilization of Striped Catfish (Pangasianodon hypophthalmus)

Chromium (Cr) is a trace element and plays a significant role in fish nutrition and physiology. An experiment was designed to know the effects of Cr addition in the diets to growth and feed utilization in striped catfish (Pangasianodon hypophthalmus). Four diets with Cr (0, 2, 4, and 8 mg kg-1) were fed to striped catfish in aquaria with triplicate groups for 60 days. Survival, growth parameters (weight gain, WG; %WG; specific growth rate, SGR), and feed utilization (feed intake, FI; feed efficiency, FE; protein efficiency ratio, PER; feed conversion ratio, FCR) were calculated at the end of the feeding trial. Several hemato-biochemical parameters, such as hemoglobin (Hb), red blood cell (RBC), white blood cell (WBC) and glucose level, and frequency of micronucleus (MN) formation in erythrocytes, were analyzed. The growth parameters (WG, %WG, and SGR) and feed utilization (FE and PER) increased significantly in the fish fed with 2 and 4 mg kg-1 Cr supplemented diets. On the other hand, the growth parameters suppressed in the fish fed with 8 mg kg-1 Cr-based diet. The polynomial regression analysis based on WG showed that 2.82 mg kg-1 Cr supplementation in the diet is optimum for the tested fish species. The values of Hb (g/dL), RBC (×106/mm3) and blood glucose (mg/dL) significantly decreased in the fish fed with the highest (8 mg kg-1) Cr-based feed. Conversely, MN frequency was significantly increased in the fish fed with 8 mg kg-1 Cr-based diet. Overall, 2.82 mg Cr kg-1 can be added to the diets of striped catfish for its better growth with maximum utilization of feed.

Use of complex physiological traits as ecotoxicological biomarkers in tropical freshwater fishes

We review the use of complex physiological traits, of tolerance and performance, as biomarkers of the toxicological effects of contaminants in subtropical and tropical freshwater fishes. Such traits are growing in relevance due to climate change, as exposure to contaminants may influence the capacity of fishes to tolerate and perform in an increasingly stressful environment. We review the evidence that the critical oxygen level, a measure of hypoxia tolerance, provides a valuable biomarker of impacts of diverse classes of contaminants. When coupled with measures of cardiorespiratory variables, it can provide insight into mechanisms of toxicity. The critical thermal maximum, a simple measure of tolerance of acute warming, also provides a valuable biomarker despite a lack of understanding of its mechanistic basis. Its relative ease of application renders it useful in the rapid evaluation of multiple species, and in understanding how the severity of contaminant impacts depends upon prevailing environmental temperature. The critical swimming speed is a measure of exercise performance that is widely used as a biomarker in temperate species but very few studies have been performed on subtropical or tropical fishes. Overall, the review serves to highlight a critical lack of knowledge for subtropical and tropical freshwater fishes. There is a real need to expand the knowledge base and to use physiological biomarkers in support of decision making to manage tropical freshwater fish populations and their habitats, which sustain rich biodiversity but are under relentless anthropogenic pressure.

Chromium Exposure Causes Structural Aberrations of Erythrocytes, Gills, Liver, Kidney, and Genetic Damage in Striped Catfish Pangasianodon hypophthalmus

Heavy metal pollution due to anthropogenic activities poses a great threat to aquatic organisms. The present study was conducted to evaluate the cytotoxic and genotoxic effects of hexavalent chromium (potassium dichromate) on hemato-biochemical, histo-pathological, and genetical changes in striped catfish Pangasianodon hypophthalmus. Three sub-lethal doses (0.8, 1.6, and 3.2 mg/L) of chromium (Cr) were selected and fish were exposed in vivo contrasting with a control (0 mg/L) for 30 days. The study revealed that various hemato-biochemical parameters showed a significant decrease in hemoglobin (Hb), red blood cells (RBCs), and blood glucose content, whereas white blood cells (WBCs) significantly increased in Cr exposed fish. Frequencies of all forms of structural abnormalities of erythrocytes (erythrocytic cellular abnormalities; ECA, erythrocytic nuclear abnormalities; ENA and erythroblasts; Ebs) were significantly increased in higher two test concentrations (1.6 and 3.2 mg/L) when compared to control. Differential leucocyte count exhibited significant increase in neutrophil and decrease in lymphocytes in the highest Cr treated group. The severity of various histo-pathological changes in the gills, liver, and kidney were increased considerably with the increase of Cr concentrations. Similarly, the amount of DNA (ng/μl) decreased significantly in blood and tissues of different vital organs where the liver showed the highest decline compared to control in a concentration-dependent manner. Taken altogether, P. hypophthalmus is susceptible to Cr and can be used as a bio-indicator to assess aquatic metal pollution.

Sumithion induced structural erythrocyte alteration and damage to the liver and kidney of Nile tilapia

Indiscriminate use of pesticides in agricultural land poses a potential threat to many non-target organisms, including fish. In the present study, we explored the toxicological effects of sumithion on Nile tilapia (Oreochromis niloticus) after exposure at different concentrations (0.0, 1.5, 2.0, 2.5, 3.0, 3.5 and 4.0 mg/L) in triplicate for 96 h. The 96-h LC₅₀ value of the pesticide for the test fish was calculated by probit analysis, which was 2.579 mg/L. We also investigated the haematological parameters, erythrocytic alteration and histopathological responses of Nile tilapia. Red blood cell (RBC) and haemoglobin (Hb) level were significantly declined, whereas white blood cell (WBC) and blood glucose level were increased dramatically in the sumithion treated fish. The frequencies of erythrocytic cellular and nuclear alterations were significantly elevated in the fish after exposure to sumithion compared with the control group. The substantial histopathological alterations were observed in sumithion-exposed fish, including pyknotic nucleus, melano-macrophage centers and severe congestion of blood vessels in the liver and patch degeneration, vacuolation and intense form of pyknotic nuclei in the kidney. Observed alterations in this study exhibit that sumithion negatively impacts on Nile tilapia. It is recommended that the use of this pesticide in the agriculture field be monitored and controlled.

In vivo assessment of dichlorvos induced histological and biochemical impairments coupled with expression of p53 responsive apoptotic genes in the liver and kidney of fish, Channa punctatus (Bloch, 1793)

Sub-lethal exposure of dichlorvos induces oxidative stress, consequent genetic instability and apoptosis coupled with impairments in biochemical, histopathological and transcription of genes in Channa punctatus. Exposure of 5% (0.041 mg/L; E2) and 10% (0.082 mg/L; E3) of 96 h-LC₅₀ of dichlorvos significantly (p < 0.05) elevated the reactive oxygen species (ROS) generation and activities of SOD and CAT, as compared to control (E1) after 30 d. The maximum reduction in reduced glutathione (GSH) was recorded in the liver (18.53 ± 0.81 μg/mg of protein) and kidney (19.32 ± 0.97 μg/mg of protein); while the total protein contents were also found reduced, 278.38 ± 8.40 μg/mL (liver) and 248.44 ± 7.28 μg/mL (kidney), after 30 days in E3, in comparison to respective controls. Further, significant (p < 0.05) induction in micronuclei (MN) and apoptotic cells (AC), in a dose- and exposure-based manner were also recorded. Moreover, a significant (p < 0.05) up-regulation of p53 (2.51-fold in liver), bax (2.03-fold in liver; 1.99-fold in kidney) and casp3a (2.26-fold in liver; 2.10-fold in kidney) together with an elevated expression of cat (1.73-fold in liver; 1.12-fold in kidney), p53 (1.27-fold in kidney) and apaf-1 (1.72-fold in liver) in fish exposed to higher dose of dichlorvos for 30 d evidently reflects geno-toxicological potential of referenced pesticide. Disturbed biochemical and molecular parameters evince that the fish experienced oxidative stress as is further supported by prominent pathological observations in liver and kidney. Findings are, thus, helpful in organ-specific molecular scanning against aquatic toxicants like dichlorvos.

Rotenone alters behavior and reproductive functions of freshwater catfish, Mystus cavasius, through deficits of dopaminergic neurons in the brain

Rotenone, commonly used as a pesticide in agriculture and as a piscicide in aquaculture, is a toxic compound that causes dopaminergic neuronal cell loss in the substantia nigra pars compacta of the brain. At the neuroendocrine level, dopamine (DA) drives behavioral (locomotion, emotion, feeding, and social interactions, etc.) and reproductive functions of fish. In the current investigation, we examined effects of rotenone toxicity on neurobehavioral and reproductive functions in whole brain and in selected brain regions in an Indian freshwater catfish, locally known as gulsha (Mystus cavasius). After fish were exposed to water containing rotenone at 0, 2.5, 25, and 250 μg/L for 2 days, significant reductions of DA, 3,4-dihydroxyphenylacetic acid (DOPAC; a DA metabolite), and their ratio (DOPAC/DA) were observed in whole brain at 250 μg/L ambient concentrations of rotenone. When fish were treated with rotenone at 250 μg/L concentration for 2 days, there was a significant reduction of DA, DOPAC and DOPAC/DA in diencephalon, DA and DOPAC in pituitary, and only DA in the telencephalon, compared with control fish. In parallel, numbers of tyrosine hydroxylase-positive (TH⁺) neurons declined significantly in the diencephalon and pituitary after rotenone treatment. Slowed, spontaneous movement and reduced feeding behavior were observed in rotenone-treated fish. Rotenone treatment resulted in a significantly higher gonadosomatic index with many mature vitellogenic oocytes in ovaries and lowered dopaminergic activity in these fish. These results indicate that rotenone influences neurobehavioral and reproductive functions through dopaminergic neuronal cell loss in gulsha brain.

Toxicity and genotoxic evaluations in African catfish Clarias gariepinus (Burchell 1822) exposed to Act Force Gold®, Butaforce®, and Atraforce®

Act Force Gold^®, Butaforce^®, and Atraforce^® are among the most commonly used pesticides in Nigeria. The lethal concentrations and the respective toxic units for the three pesticides were determined. The genotoxic effects of the three pesticides were investigated in the red blood cells of Clarias gariepinus using micronucleus (MN) assay. The 96 h LC₅₀ was 4.75, 4.84, and 54.74 mg L^-1 for Act Force Gold^®, Butaforce^®, and Atraforce^®, respectively. The toxic units in ascending order of toxicity were 1.83, 20.66, and 21.05 for Act Force Gold^®, Butaforce^®, and Atraforce^® respectively. The estimated safe levels based on NAS/NAE varied from 4.75 × 10^-1-4.75 × 10^-5 in Act Force Gold^® through 4.64 × 10^-1-4.85 × 10^-5 in Butaforce^® to 5.74-5.74 × 10^-5 in Atraforce^®. Fish specimens were exposed to the pesticides and sampling was done at regular intervals at days 1, 7, 14, and 21 and after another 7-day recovery period. The results obtained indicated concentration- and duration-dependent increase in % MN formation with maximum values of 3.40 ± 0.25 for Act Force Gold^® on day 14 and 3.05 ± 0.36 and 2.35 ± 0.14 for Butaforce^® and Atraforce^® respectively on day 7 of exposure. The 7-day recovery period could not reverse the trend as the % MN values obtained were significantly different from the control. The results further support the use of MN assay in assessing the toxicity of aquatic pollutants and can be used in the monitoring of aquatic ecosystems.

Toxic effects of fenitrothion on freshwater microcosms in Bangladesh

The organophosphate pesticide fenitrothion is widely used as an agricultural pesticide to control tiger bug in larval rearing for aquaculture. The objectives of the present study were to assess the effects of fenitrothion on certain structural (phytoplankton, zooplankton, macro-invertebrates and periphyton) and functional (organic matter decomposition) endpoints of freshwater microcosms. Fenitrothion 50 EC was applied in 12 microcosms (PVC tanks having 400 L of dechlorinated tap water) providing concentrations of 0, 25, 50 and 100 μg/L at a 4-day interval over a period of 4 weeks. Each of the experimental treatment was executed in three replicates. The results indicated the consistent significant effects for most of the species composition of zooplankton and macro-invertebrates. Univariate analysis showed a significant decrease in abundance (p < 0.05) of all identified insects (i.e. Notonecta sp., Gerris sp., Ranatra linearis and Chironomid larvae), when compared to control in all sampling days throughout the treatment period (no observed effect concentration; NOEC = < 25 μg/L). No consistent significant effects were observed for most of the phytoplankton taxa and organic matter decomposition and water quality variables (dissolved oxygen, free CO₂, pH, nitrate etc.). However, several taxa of different endpoints were found sensitive to even the lowest concentration of fenitrothion (25 μg/L). Further studies with acute and chronic conditions are recommended involving more local species exposed to < 25 μg/L of fenitrothion.

Global trends in pesticides: A looming threat and viable alternatives

Pesticides are widely used chemical compounds in agriculture to destroy insects, pests and weeds. In modern era, they form an indispensable part of agricultural and health practices. Globally, nearly 3 billion kg of pesticides are used every year with a budget of ~40 billion USD. This extensive usage has increased the crop yield as well as led to significant reduction in harvest losses and thereby, enhanced food availability. On the other hand, indiscriminate usage of these chemicals has led to several environmental implications and caused adverse effects on human health. Epidemiological evidences have revealed the harmful effects of pesticides exposure on various organs including liver, brain, lungs and colon. Recent investigations have shown that pesticides can also lead to fatal consequences such as cancer among individuals. These chemicals enter ecosystem, thus hampering the sensitive environmental equilibrium through bio-accumulation. Due to their non-biodegradable nature, they can persist in nature for years and are regarded as potent biohazard. Worldwide, very few surveillance methods have been considered, which can bring awareness among the individuals, therefore the present review is an attempt to delineate consequences induced by various types of pesticide exposure on the environment. Further, the prospective of biopesticides use could facilitate the increase of crop production without compromising human health.

Nuclear and Cellular Abnormalities of Erythrocytes in Response to Thermal Stress in Common Carp Cyprinus carpio

As a consequence of global warming, increase of water temperature is likely to alter physiological functions of fish. Hence, we examined the effects of high temperature on blood glucose, hematological parameters [hemoglobin (Hb), red blood cell (RBC), and white blood cell (WBC)], and nuclear and cellular structure of blood cells of common carp (Cyprinus carpio) after exposure to three temperature regimes (27, 31, and 35°C) for 14 days. Fish were sacrificed on 3, 7, and 14 days of exposure. The blood glucose level increased significantly in the fish exposed to 35°C compared to 27 and 31°C. The Hb and RBC contents decreased but WBC increased significantly in the blood of fish exposed to 35°C compared to 27 and 31°C at 7 and 14 days of exposure. Consequently, the frequencies of erythroblasts (Ebs), erythrocytic nuclear abnormalities (ENA), and erythrocytic cellular abnormalities (ECA) were found to be increased in the blood of fish exposed to 35°C compared to 27 and 31°C. There was a significant increase in neutrophils and decrease in lymphocytes in the highest temperature (35°C). With increasing temperature, dissolved oxygen (DO) decreased but free CO₂ increased significantly during the study period. The present study demonstrated that common carp are better adapted to 27 and 31°C environmental temperatures, while the higher temperature 35°C is likely stressful to this fish species.

Acute effects of chromium on hemato-biochemical parameters and morphology of erythrocytes in striped catfish Pangasianodon hypophthalmus

Chromium is considered the most detrimental pollutant to the aquatic organisms. The present experiment was conducted to determine the acute toxicity of chromium in view of its effects on hemato-biochemical parameters and the structure of erythrocytes in striped catfish, Pangasianodon hypophthalmus. Fish were exposed to seven different concentrations (0, 10, 20, 30, 40, 50 and 60 mg/L) of chromium, each with three replications for 96 h. After 96 h of exposure, the survived fish were sacrificed to measure hemato-biochemical parameters (hemoglobin, Hb; red blood cell, RBC; white blood cell, WBC; packed cell volume, PCV; mean corpuscular volume, MCV; the mean corpuscular hemoglobin, MCH and blood glucose). In addition, erythrocytic cellular abnormalities (ECA) and erythrocytic nuclear abnormalities (ENA) of peripheral erythrocytes were assayed. No mortality was observed up to 10 mg/L, but 90% and 100% mortality was observed at 50 mg/L and 60 mg/L, respectively after a 96 h exposure period. The 96 h LC50 value through probit analysis was 32.47 mg/L. Hb (%), RBC (×106/mm3) and PCV (%) significantly decreased at 20, 30 and 40 mg/L of chromium, whereas WBC (×103/mm3), MCV (μm3) and MCH (pg) showed the opposite scenario. Blood glucose (mg/dL) levels significantly increased at 10, 20, 30 and 40 mg/L of chromium compared to 0 mg/L. Frequencies of ECA and ENA significantly increased with increasing chromium concentrations. This study indicates that chromium is highly toxic to striped catfish.

Hypoxia reduced upper thermal limits causing cellular and nuclear abnormalities of erythrocytes in Nile tilapia, Oreochromis niloticus

Global warming is a threat across the world that leads to estimates of the upper thermal limits of ectothermic species. Increased water temperature up-regulates oxygen consumption and metabolic rates, and alters the physiological processes. In this study, we identified the critical thermal maxima (CTmax) and physiological responses under normoxia and hypoxia in Nile tilapia, Oreochromis niloticus. CTmax was 41.25 °C under hypoxia and 44.50 °C under normoxia. Compared to normoxia, lower values of hemoglobin (Hb) and red blood cells (RBCs) were observed at the CTmax under hypoxia. In contrast, higher values of white blood cells (WBCs) and blood glucose (Glu) levels were observed at the CTmax under hypoxia. Consequently, higher frequencies of micronucleus, cellular and nuclear abnormalities of erythrocytes were observed at the CTmax under hypoxia. These results suggest that high temperature tolerance and subsequent physiology are significantly affected by the oxygen supply in Nile tilapia. As climate vulnerability is intensifying day by day, this data will be helpful in successful management practice for the aquatic environment having low oxygen content.