Ecotoxicology : A Review of Pesticides Induced Toxicity in Fish

| Throughout the world pesticides are widely employed in agriculture sector in order to elevate crops’ yield with low labour and efforts. Pesticides exposure leads to toxicity in many non-target organisms, fish being one of the most prominent among these. Most of the time acute concentration of these pesticides leads to mortality while sub lethal concentration of these pesticides result in different lethal changes. These changes may be in behaviour of the exposed fish such as change in feeding behaviour, attack or avoiding behaviour and reproductive behaviour, or other types of alterations such as changes in histology (liver, kidneys, gills, muscles, brain, intestine), haematology (RBCs, WBCs or Plasma), anti-oxidant defence system (Glutathione reductase, Peroxidase, Catalase, Superoxide dismutase, Glutathione peroxidase, Glutathione-S-transferase etc.), changes in nutrient profile (Protein, Lipids, Carbohydrates, Moisture content and Ash etc.) and worth of the fish, hormonal or enzymatic alterations, oxygen consumption, and DNA damage or damage at genes level (genotoxicity). Different environmental agencies are working on this aspect and that’s why there are a large number of banned chemicals. Still these chemicals are available in markets. Certain newly synthesized pesticides (insecticides or fungicides etc.) and extensive use of these chemicals are always there to maximize the problem for aquatic organisms especially fish. This article focuses on the same aspect of ecotoxicology and reviews some major induced toxicological aspects of pesticides in fish including behavioural changes, histopathological damages, haematological alterations, biochemical changes, fluctuations in acetylcholinesterase activity, vicissitudes in protein contents, induced genotoxicity, alterations in feeding biology, oxygen consumption and oxygen stress all across the world.


DETERMINING PESTICIDE CONTENTS
For finding pesticide contents in sediments, organic substrate, water and most important in animal or plants tissues is done chemically (APHA, 1998;Shuhong et al., 2005;Ishaq and Khan, 2013).The solid tissue of animals or plants and other solid materials are first homogenized and then extraction is done through acetone or hexane, then evaporated to a small volume, followed by cleaning and drying, and then finally analysed (Peterson and Batley, 1993;USGS, 1995;Hong et al., 2003;Hong et al., 2006;Zhou et al., 2007;Hong et al., 2008).
For determining the effects of pesticides such as acute toxic effect of these chemicals on aquatic organism biological methods are used, in situ bioassays (Akcha et al., 2003;Buschini et al., 2004;Cavas and Ergene-Gozukara, 2005;Pandey et al., 2011;Kushwaha et al., 2012).This assay is based on exposing the test animals to the field without disturbing the polluted sediments.After exposure survival percentage is determined.Sometimes when the water column is too deep or too fast, water cages are used for holding the fish in water column (Dey and Saha, 2014).

indirect effectS of PeSticideS to fiSh
Pesticides greatly reduce food organisms' abundance in aquatic bodies and eco system which is necessary for fish survival (Helfrich, 2009).By this mean it indirectly interrupts the fish food supply and change the habitat of water bodies (Maskaoui et al., 2005;Chau, 2005).Besides this it can also make the fish more susceptible to predators by decreasing habitat suitability and changing their behaviour as well, which is a direct effect as a consequence of indirect effect (Holden, 1973;Prashanth et al., 2011;Gill and Raine, 2014).Results have shown that these indirect effects can be much more vital than the direct ones (Murthy et al., 2013).

lethal effectS of PeSticideS
Studies have shown that sub lethal amount of certain chemicals induced abortions (Boyd, 1964).DDT (dose of 2 mg kg1 per seven days for five months) resulted in production of more mature ova than control group while mortality in sac fries was higher, when the gametes were from DDT treated parents as compared to control fish group.In 1996 the disastrous event of mortalities in various fish species such as deaths of 92,000 steel head, 19 resident rainbow trout, 114 juvenile coho salmon and thousands of non-game fish species in a branch of Rogue River by the name of Bear Creek (Ewing, 1999) was attributed to aquatic pollution mainly from chemicals such as pesticides.
Table 1 is depicting a list of common pesticides along with their lethal concentrations for different fish species.However for further details handbook of Johnson and Finley (1980) can be consulted.
In contrast to lethality and mortalities of fish on account of lethal concentration, sublethal concentrations of these pesticides lead to subtle changes in biology of different fish and consequently effect their survival (Scott and Sloman, 2004;Rani and Kumaraguru, 2014).Laboratory experiments have shown different effect of these pesticides on different biological aspects of these fish species.DDT has shown a disastrous effect of disturbing the reproduction of certain species while some species such as cutthroat goldfish have shown no change (Allison et al., 1964).The altered physiology and other changes that take place due to sublethal concentration of pesticides are divided into behavioural, Histopathological, haematological and such other subheadings in the following.

PeSticide indUced BehavioUral changeS in fiSh
Pesticides have shown different alteration in behaviour of various fish species such as rendering fish sluggish and alter their swimming ability making them more susceptible to be preyed, reduce their ability to feed, maintain their position and defend their territories (Prashanth et al., 2011) et al., 2011).Disruption of schooling behaviour also renders the fish more susceptible and easily preyed.
On account of stress due to pesticides, fish became stressed and immunocompromised, which make them more susceptible and vulnerable to diseases, secondary infections and pathogens (Satyavardhan, 2013;Nwani et al., 2010).Methyl parathion resulted in increased movements of opercula, rapid jerk movement, equilibrium loss, body colour alterations, frequent surfacing, and elevated mucus secretion in Catla catla (Ilavazhahan et al., 2010).Cypermethrin caused darting, erratic and irregular swimming movements, equilibrium loss, hyper excitability and sinking to bottom in Labeo rohita (Marigoudar et al., 2009).
Pesticides also alter the migratory behaviour of migratory fish (Nagaraju et al., 2011), thus result in disturbing their life cycle such as it can disturb the ability of salmonid fish to transit from fresh water to sea water.However this phenomenon is seeking further researchers to place particular emphasis on critical period of transition, which occurs in estuaries.Yet studies have shown that adult salmon use to circumvent pollutants and contaminated areas during their migration, altering their migratory pattern, which result in postponement of spawning (Satyavardhan, 2013).Cypermethrin resulted in jumping, increased surface activity, balance loss, increased air gulping, equilibrium loss, abrupt swimming, sluggishness, motionlessness, adopting vertical positions and internal haemorrhage in Tor putitora (Ullah et al., 2014c).Sodium cyanide induced certain behavioural changes such as hypexcitability, darting and erratic movements, and imbalance swimming, in Oreochromis mossambicus, Catla catla, Cirrhinus mrigala, Labeo rohita, and Cyprinus carpio (David et al., 2012).There are many other studies confirming behavioural changes in fish due to pesticides (Scott and Sloman, 2004;Krian and Jha, 2009;Prashant et al., 2011;Rani and Kumaraguru, 2014).

PeSticide indUced hiStoPathological changeS in fiSh
Histopathological changes due to various pesticides have been extensively studied in different fish species.These changes have been traced in liver, gills, blood vessels, brain, kidneys and muscles of the studied fishes.The changes documented are quite various such as partial loss of liver plate radial orientation, cytoplasmic granularity and shrinkage of liver cell mass in liver cells; pycnotic alteration of cell nuclei, atrophy and cytoplasm vocalization in kidneys; gill lamellae and filaments have shown precipitated masses that plugged to the central capillaries and in large blood vessels various changes have also been observed such as alteration in morphology, haematocrit levels and blood cells' quantity (Kennedy et al., 1970).
Histopathological changes were also observed in ovary when expose to Malathion altered ovigerous lamellae, follicular cell degeneration, atrectic oocytes increment, clumping of cytoplasm, ruptured follicular epithelial lining and nuclear materials' shrinkage, which was attributed to endocrine and hormonal imbalance, while carofuran caused degeneration of connective tissues, follicular walls and vacuolization in the ooplasm during stage second and third (Mohan, 2000;Chatterjee et al., 1997;Dutta et al., 1994) and diazinon exposure resulted in different alterations in ovaries such as primary follicles adhesion, atretic oocytes increment, cytoplasmic retraction in oocyte II, damages to oocyte IV, vitellogenic membrane destruction, increased intrafollicular spaces, cytoplasmic degeneration, cytoplasmic necrosis, karyoplasm extrusion and vacuolated cytoplasm (Dutta et al., 2003).Malathion also resulted in changes in histology of liver, ovary and kidney in Heteropneustes fossilis (Deka and Mahanta, 2012).Sodium cyanide also resulted in histopathological changes such as variation in histoarchitecture of kidneys including necrosis, degeneration of glomerulus, lymphocytes infilteration, cytoplasmic vacuolation, blood congestion, damage to collecting duct and size change of tubular lumen, in Cyprinus carpio after exposure to sub lethal concentration (David and Kartheek, 2014).
Certain other studies also support the toxic effects of pesticides in various tissues and organs of different fish, such as atrazine to Labeo rohita ( Jayachandran and Pugazhendy, 2009) There are many other studies conducted showing haematological changes taken place due to different pesticides ( Joshi et al., 1988;Joshi et al., 2002;Johal and Grewal, 2004;Gautam and Kumar, 2008).

PeSticide indUced toxic effectS in acetylcholineSteraSe of fiSh
AChE (AChE) activity is very much sensitive for carbamate pesticides and organo phosphates as compare to other types of pesticides and contaminants (Murthy et al., 2013).Various studies have been shown that inhibition of this enzyme has been associated with the effects and exposure of fish with other contaminants such as crude oil addition to brain homogenate inhibited AchE activity (Rodriguez-Fuentes, 2000).AChE activity was inhibited by 40% in muscles of flounder on account of abode in polluted sites (Minier et al., 2000); heavy metals and pesticides also reduced AChE activity in brain by 40% in three polluted sites in Italy (Lionetto et al., 2003).AChE activity in Labeo rohita was inhibited by Cypermethrin significantly, brain being the most altered followed by muscles, gills and liver tissues (Marigoudar et al., 2010).
By affecting the AChE activity in fish, the swimming capability and performance of fish is ultimately reduced and disturbed which can attribute to more harmful consequences (Rao, 2006;Rao et al., 2007)

PeSticide indUced BiocheMical changeS/ oxidative StreSS in fiSh
Various studies have shown devastating effects of pesticides in various biochemical activities (Ullah et al., 2014c).These changes in antioxidants systems of fish are often tissue specific such as these changes have been traced in brain, gills, muscles, kidneys, lungs and viscera of different fish and have shown varying results in different organs and different fish species such as peroxidase activities was found higher in brain, viscera, gills, and muscles of tilapia but gills was the organ received highest disturbance in peroxidase (Ahmad et al., 2000).Similarly changes in lipid peroxidase have been observed on account of different pesticides as well as environmental pollutants.

PeSticide indUced MolecUlar changeS in fiSh (genotoxicity)
Various studies conducted have shown that pollutants cause carcinogenesis (Dunn, 1991;Weishburger and Williams, 1991;El Adlouni et al., 1995;Erickson and Larsson, 2000), teratogenesis, clastogenesis and mutation in fish (Obiakor et al., 2012) which ultimately lead to reduced growth, malignancies, reduction in survival of fish in early life stages as well as adult stage, abnormal development and different deformities of body organs (Akpoilih, 2012).There is rich documented literature witnessing research on molecular level of different fish species showing ill effects of pesticides on genes and DNA levels (Stahl, 1991;Helma et al., 1996;Mitchelmore and Chipman, 1998;White et al., 1998a;White et al., 1998b;Hose and Brown, 1998;Hartmann et al., 1999;Gartiser et al., 2001;Vargas et al., 2001;Çavas and Könen, 2007).al., 2013).Also, in a complex pathway, dioxin interacts with DNA to alter how genes control protein synthesis, for example the protein called vitellogenin which is involved in egg development (Zorriehzahra, 2008).

PeSticideS indUced changeS in iMMUne SySteMS and endocrine diSrUPtorS
Pesticides have shown disruption of immune system in fish (Bols et al., 2001;Maskaoui et al., 2005).Studies have shown serious ill impact of pesticides on immune system, which results in disease initiation and eventually can lead to death (Dunier and Siwicki, 1993;Halloran et al., 1998).Fish are also vulnerable to endocrine disrupting impacts during early life stages or stages of development (Magare, 1997;Gupta et al., 1997;Kamble et al., 1999).Pesticides also act as sex hormones' blockers, which leads to anomalous and atypical sexual development, irregular sex ratios, males' feminization and disturbed mating behaviour.Susceptible fish reproductive behaviour de-picts its vulnerability by different pollutants such as pesticides (Hoeger et al., 2005).It can also alter other hormonal processes of fish like development of bones and proper thyroid functioning (Murthy et al., 2013).Dimethoate and Lambda-cyhalothrin showed lethal effect on Thyroid hormone of Labeo rohita (Dey and Saha, 2014).Several studies have shown that environmental chemicals disturb levels plasma thyroid hormone (Steenland et al., 1997).Disturb plasma thyroid hormone level leads to thyroid dysfunction in fishes (Waring et al., 1997).

PeSticideS indUced changeS in oxygen conSUMPtion
Different studies conducted put forth the results of reduction or increase in oxygen consumption by various fish species when exposed to different pesticides.These fish showed these changes with different time and duration of exposure such as Dimethoate (Shereena et al., 2009) andlead ( James et al., 1993) induced toxic changes in oxygen consumption in Oreochromis mossambicus.Dimethyl parathion disturbed the oxygen consumption in Labeo rohita (Bengeri et al., 1984), DDT induced disturbance in Lepidocephalichthys thermalis (Gurusamy and Ramadoss, 2000), endrin in Lepomis machrochirus (Huner et al., 1967) and different pesticides in Puntius ticto (Magare and Patil, 2000).

PeSticideS indUced changeS in larvivoroUS Potential of fiSh
Organophosphorous pesticides, on account of high insecticidal property, lesser persistence, less toxic to mammals and rapidly biodegradable, are frequently used (Bhandare et al., 2011) but unfortunately these also affects non-target life forms both indirectly as well as directly including larvivorous fish species (Roger and Bhuiyan, 1990).
Pesticides have been concluded as an agent of alteration in fish physiology.Different studies conducted have shown pesticides lowering the larvivorous potential of different fish species., 2012).Instead of these pesticides, larvivorous fish can be used for biological control of vector mosquito (Chandra et al., 2008).It is safer and environmental friendly approach instead of using these pesticides which often lead to higher mortalities and reduction of fish population (Ravindran et al., 2012).

dioxin aS tyPical Model for Side effectS of PeSticideS on fiSh health
Fish show a wide range of sensitivity to some chemical substances such as dioxin.Trout are very sensitive to the effects of dioxin.These fish are not only being used to tell scientists about what is happening in the environment but as models of what may happen to humans exposed to these chemicals.In experimental study in University of Wisconsin, researchers have injected very small quantities of dioxin and dioxin-like chemicals into newly fertilized lake trout eggs.Dramatic changes in the development of the embryo have been observed in this fish (Guiney et al., 1996).Very small amounts of dioxin into lake trout embryos causes a condition called "blue-sac disease" in which there is a disruption of both the yolk sac and blood vessels.Normal embryos of lake trout have large yolk sacs and good blood vessel formation.Rate of mortality could be reached in 25% in affected farms (Peterson et al., 1993).But when fry mortality syndrome occurred after stage of yolk sac absorption, above mentioned disorder signs could not be observed.
Furthermore, Dioxins are highly toxic to both freshwater and marine fish, particularly to early life stage fish, although the saltwater fish species tested so far are more tolerant to TCDD (2,3,7,8-tetrachlorodibenzo-p-dioxin) exposure than most freshwater species (Walker and Peterson,1994) Previously exposed saltwater fish are also more tolerant than un-adapted fish.Lake trout were the most sensitive to TCDD, the most toxic form of dioxin.(Peterson et al., 1993) discovered that TCDD levels in lake trout eggs as low as 30 parts per trillion caused observable increases in yolk-sac fry mortality, and 100 percent mortality occurred at TCDD levels above 100 parts per trillion.The yolk-sac fry die from an accumulation of excess fluid in the yolk-sac (yolk sac edema) and around the heart (pericardial edema), obstructed blood flow (ischemia), hemorrhages, and a deformed skull (craniofacial malformations) conditions resembling blue sac disease.Typical toxic responses in early-stage fish following exposure to TCDD include yolk sac edema, hemorrhaging, arrested development, and head and spinal deformities, and in older fish include lesions, fin necrosis and death.Dioxin and dioxin-like chemicals such as PCBs and polyaromatic hydrocarbons (PAHs) are sometimes called xenoestrogens.This means that these chemicals can either mimic or disrupt the function of the sex hormone estrogen.They may also affect development and the immune system or cause cancer.Dioxin has its toxic effect at the level of the cell (Walker and Peterson, 1991).In a complex pathway, dioxin interacts with DNA to alter how genes control protein synthesis, for example the protein called vitellogenin which is involved in egg development (Zorriehzahra, 2008).

CONCLUSION
This article concluded that pesticides can create a great economic loss by fish mortalities on one hand and on the other hand rendering them unfit for human consumption.If consumed, these fish can cause health hazard situation for those who utilized these fish.From a health perspective this article depicts that one should take necessary precautionary measure when selecting fish.From a pesticides standpoint such pesticides should be avoided or should be used to minimum for protecting aquatic life.Researchers all across the globe have worked on the toxic effects of pesticides in fish such as behavioural change, Histopathological alterations, haematological and biochemical change, AChE activities inhibition, decrease in protein and lipid contents, change in life cycle, carcinogenesis, mutagenic changes, physiological changes and change in reproductive process.On account of differences in susceptibility of different fish species to various pesticides and other pollutants, fish that are less susceptible and vulnerable to these chemicals and pollutants should be stocked in water bodies.Beside this such species should be stocked that accumulate less quantity of pesticides, heavy metals and other pollutants.Further studies and research regarding new introduced pesticides and other chemicals should be carried out in both natural as well as laboratories.This will be helpful in documenting the toxic effects of these contaminants and on the basis of these experiments, nontoxic or less toxic as well as environmental friendly chemicals can be employed.

in Animal and Veterinary Sciences January 2015 | Volume 3 | Issue 1 | Page 46 glucose
6 phosphate dehydrogenase in skeletal muscle, liver and brain, while lactate dehydrogenase activity in brain of Clarius batrachus(Tripathi and Verma,  2004).Malathion resulted in disturbed Catalase and Glutathione-S-transferase activities in gills, liver and muscles of Labeo rohita(Thenmozhi et al., 2011)and also induced biochemical changes in Clarias batrachus(Khare et al., 2000).Cypermethrin induced very much change in Catalase, Glutathion Reductase, Peroxidase, and Lipid peroxidase in brain, liver, gills and muscle tissues of Tor putitora (Ullah et al., 2014c) while catalase, hydrogen peroxide, malondialdehyde, protein carbonyls and free amino acid in liver of Labeo rohita(Marigoudar et al.,  2012).Sodium cyanide caused steady decreased with time in different enzymatic activities such as succinate dehydrogenase, lactate dehydrogenase, phosphorylase, glucose-6-phosphate dehydrogenase, acid phosphates and alkaline phosphatase in different tissues such as liver, gills and muscles of Labeo rohita(Dube et al.,  2013)and catalase in Cyprinus carpio(David et al., Colisa fasciatus(Singh et  al., 2010).Profenofos caused significant change in tail of marine fish, Therpon jarbua(Devi et al., 2011).
that leads to mutation(Gilot-Delhalle et al., 1983), and hyperproliferation of cells due to local irritation(Mirsalis et al., 1989; Oshiro et al., 1991; Benford et  al., 1994).Interestingly longer exposure was associated with lower frequency of DNA aberrations.Cyper-methrin caused changes in nucleic acids (RNA and DNA) in gonadal tissue of

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2015 | Volume 3 | Issue 1 | Page 48 al.