Evaluation of genotoxicity induced by herbicide pendimethalin in fresh water fish Clarias batrachus (linn.) and possible role of oxidative stress in induced DNA damage.

The present study was carried out in fish Clarias batrachus to evaluate the genotoxicity induced by herbicide pendimethalin and to find out the role of oxidative stress in induced DNA damage. The LC50 value (96 h) of pendimethalin was determined (3.55 mg/L) and based on this, sub lethal test concentrations were calculated as SL-I (1/20th LC50), SLII (1/15th LC50) and SL-III (1/10th LC50) to which fish were exposed for 30, 45 and 60 days. Maximum DNA damage was observed in fish exposed to highest concentration of herbicide and for a particular concentration maximum damage occurs after 30 days then a time dependent decrease was observed. After 30 days the SOD and CAT activity was found to be significantly increased with respect to the control group while it was significantly decreased after 45 and 60 days as compared to 30 days of exposure. Level of lipid peroxidation in pendimethalin exposed fish followed the same pattern. GR activity remained same for all duration of herbicide exposure. The DNA damage is due to ROS generated by the metabolism of herbicide which is evident by alteration in LPO and anti-oxidant enzyme activities accompanied by incidence of DNA damage in a similar way. It can also be concluded that for pendimethalin genotoxicity testing C. batrachus can be used as model organism and comet assay and micronucleus test as effective tools.

Genotoxic Potential Assessment of the Herbicide Bispyribac-Sodium in a Fresh Water Fish Clarias batrachus (Linn.).

Genotoxic potential of herbicide bispyribac-sodium was evaluated in fish Clarias batrachus using micronucleus (MN) test and comet assay. Fish were exposed to three environmentally relevant test concentrations of the herbicide for 20, 25 and 30 days. Significant effects (p < 0.05) for both concentration and duration of exposure were observed in herbicide exposed fish. Similar trend of DNA damage was observed through MN test and comet assay. Maximum DNA damage was observed in fish exposed to highest concentration of herbicide at all duration. Maximum damage was observed on day 25 at all concentrations followed by a decline. This study established C. batrachus as an ecotoxicological model for bispyribac-sodium induced genotoxicity testing. It further confirmed that both MN test and comet assay are useful tool for assessment of genotoxicity induced by water pollutants.

Impact of herbicide pretilachlor on reproductive physiology of walking catfish, Clarias batrachus (Linnaeus).

Herbicide pretilachlor is widely used in paddy fields to control annual weeds. The present study has been carried out in walking catfish, Clarias batrachus, to evaluate the impact of herbicide pretilachlor on reproductive physiology after chronic exposure. Based on the median lethal concentration value (96 h), fish were exposed to three nominal test concentrations of pretilachlor ((SL-I (1/20th LC50), SLII (1/15th LC50), and SL-III (1/10th LC50)) for 30, 45, and 60 days after which plasma sex steroid profile, plasma vitellogenin concentration, and gonadal aromatase activity were analyzed in both sexes. Plasma concentration of testosterone decreases in herbicide-exposed male fish. Significant increase in plasma 17ß-estradiol, plasma vitellogenin concentration, and gonadal aromatase activity were observed in herbicide-exposed male fish. All these alterations in reproductive parameters in male fish are dependent on concentration and exposure duration of herbicide. On the other hand, significant decrease in plasma concentration of testosterone was observed in female fish which was also dependent on concentration and exposure duration of herbicide. No significant changes in plasma 17ß-estradiol concentrations, plasma vitellogenin concentration, and gonadal aromatase activity were observed in female fish. Above findings clearly suggested that herbicide pretilachlor acts as endocrine disruptor in fish and affects overall reproductive physiology of fish, but its ability to induce reproductive toxicity in male and female differs considerably.

Impacts of herbicide pendimethalin on sex steroid level, plasma vitellogenin concentration and aromatase activity in teleost Clarias batrachus (Linnaeus).

Pendimethalin (PM) is a selective herbicide, widely present in aquatic environment. It causes detrimental effects in fishes, but little is known regarding its reproductive toxicity. The present study was carried out in Clarias batrachus exposed to sub lethal concentrations of PM for 30, 45 and 60 days. Male fish showed a significant increase in plasma 17ß-estradiol (E2) however plasma E2 in females was not affected. Plasma testosterone levels were significantly decreased in both sexes. In male plasma vitellogenin (VTG) and gonadal aromatase activity was increased irrespective of herbicide concentration and exposure duration. In females concentration and time dependent reduction in plasma VTG but no significant change in the gonadal aromatase activity were observed. Results indicated that PM act as endocrine disruptor but act differentially in male and female fishes and plasma E2, T and VTG levels and aromatase activity can be considered as reliable biomarkers for PM toxicity in fishes.

Acute toxicity and behavioural responses in Clarias batrachus (Linnaeus) exposed to herbicide pretilachlor.

Pretilachlor is a systemic herbicide belonging to chloroacetamide group which is being used in rice fields for the control of annual weeds. The acute toxicity bioassay of pretilachlor was carried out by probit analysis method and the safe level was estimated by multiplying the 96 h LC50 with different application factors. The 12, 24, 48, 72 and 96 h LC50 values were obtained as 11.12, 9.55, 8.57, 7.11 and 5.84 mg L-1 respectively while the safe values found ranges 0.05 to 0.58 mg L-1. Buccal movements as well as the number of burst swimming movements in fishes exposed to pretilachlor were found to be increased significantly in response to all concentrations of the herbicides tested. Number of feeding attempts reduced significantly while irregular responses in fishes were observed regarding their attempt to form group after exposure to herbicide. As a whole, exposure of fishes to pretilachlor showed significant effects on all studied behaviours. So it can be concluded that the herbicide pretilachlor is toxic to fishes and its excess use should be avoided.

Impact of Environmental and Disturbance Variables on Avian Community Structure along a Gradient of Urbanization in Jamshedpur, India.

Gradient pattern analysis was used to investigate the impact of environmental and disturbance variables on species richness, species diversity, abundance and seasonal variation of birds in and around Jamshedpur, which is one of the fastest growing cities of India. It was observed that avian community structure is highly influenced by the vegetation habitat variables, food availability and human-related disturbance variables. A total of 61 species belonging to 33 families were recorded from the suburban area. 55 species belonging to 32 families were observed in nearby wildland habitat consisting of natural vegetation whereas only 26 species belonging to 18 families were observed in urban area. Results indicated that the suburban habitat had more complex bird community structure in terms of higher species richness, higher species diversity and higher evenness in comparison to urban and wildland habitat. Bird species richness and diversity varied across seasons. Maximum species richness and diversity was observed during spring season in all type of habitat. Most of the birds observed in urban areas were found to belong to either rare or irregular category on the basis of their abundance. The observed pattern of avian community structure is due to combined effect of both environmental and human related disturbance variables.

Ultimobranchial gland respond in a different way in male and female fresh water teleost Mastacembelus armatus (Lacepede) during reproductive cycle.

The present study was carried out to analyze the differences in the activity of ultimobranchial gland (UBG) between male and female fresh water teleost Mastacembelus armatus during reproductive cycle. Considerable variations in the nuclear diameter of UBG cells and plasma calcitonin (CT) levels during different reproductive phases of testicular and ovarian cycle suggested that the activity of the UBG depends upon the sexual maturity of fishes. A positive correlation was observed between plasma CT and sex steroid levels and the gonadosomatic index in both sexes which further confirmed the involvement of UBG in the processes related to gonadal development in fishes irrespective of the sex. Sudden increase in the level of plasma CT and nuclear diameter of UBG cells after administration of 17 α-methyltestosterone in males and 17 ß-estradiol in females during resting phase of the reproductive cycle clearly showed that UBG becomes hyperactive with increases in the level of sex steroids. Plasma calcium level was also found to be positively correlated with gonadal maturation in females. However no such change in plasma calcium level in relation to testicular cycle was observed. Thus it can be concluded that UBG becomes hyperactive during gonadal maturation but its role differs between male and female fishes. In females it may involved in both gonadal maturation and plasma calcium regulation while in males its involvement in calcium regulation was not justified. Variations in the level of CT during various phases of testicular cycle evidenced its involvement in gonadal maturation only.

Differential activity of stanniocalcin in male and female fresh water teleost Mastacembelus armatus (Lacepede) during gonadal maturation.

The present study was carried out to analyze the differences in the activity of hormone stanniocalcin (STC) between male and female fishes of Mastacembelus armatus during their gonadal cycle. A large variation in nuclear diameter of cells of corpuscles of Stannius (CS) were recorded in relation to testicular cycle as well as ovarian cycle which indicates that the cellular activity varied with different phases of reproductive cycle in both male and female fish. Similar changes in nuclear diameter of CS cells were also observed after 17alpha-methyltestosterone administration in males and 17 ß-estradiol administrations in females. A positive correlation was observed between plasma STC levels, gonadosomatic index (GSI) and the sex steroids in both sexes, suggesting that STC has a role in the processes involved in gonadal development. In addition females showed remarkable changes in plasma calcium level during gonadal cycle while no such change for males were observed. In females the plasma calcium level estimated during different phases of reproductive cycle indicates positive correlation between plasma level of calcium and gonad growth. Thus hyperactivity of CS cells was noted in both male and female fishes during gonadal cycle along with the differences in the activity of STC as well. In female it may act as hypocalcemic factor and bring the level of calcium to normal which increases during preparatory and pre spawning phases to fulfill the increased demand of calcium for vitellogenesis. However data of male fishes indicated that plasma STC concentration varied widely during gonadal cycle but showed no consistent relationship to plasma calcium level.