Paper and Pulp Mill Effluent-Induced Immunotoxicity in Freshwater Fish Channa punctatus (Bloch)

The influence of temperature variation on the humoral immune response using the plaque-forming cell (PFC) assay in freshwater fish Channa punctatus (Bloch) was investigated. The fish was exposed to 1% concentration (v/v in water) of paper and pulp mill effluent under standard laboratory conditions in glass aquaria. Effect of effluent exposure on the organ weight and organ cellularity was also evaluated. In general, lower temperature in winter produced a subdued response in control as well as experimental group. At higher temperature of summer and rainy seasons, an elevated response was observed. It was revealed that though suppressive effect of effluent was evident during all the seasons, in summer, extent of suppression was greater as compared to winter. Paper and pulp mill effluent exposure resulted in a decrease in the splenic and pronephric (head kidney) cellularity, with more pronounced effect in the summer season. We also studied the effects of the length of exposure on various parameters. Fish were exposed for 15, 30, 60, and 90 days to effluent. Short-term exposure for 15 days induced an elevated PFC response, but change was not statistically significant. Conversely, the exposure for 30, 60, and 90 days significantly reduced (p < 0.05–0.001) the PFC response. Long-term exposure also caused significant reduction (p < 0.05–0.01) in the weights of lymphoid organs (spleen, head kidney, and total kidney). These results show a suppressive effect of chemical constituents of paper and pulp mill effluent on the immune functions. Furthermore, results demonstrated that though modulatory effect of the temperature on immune functions is recognized, it was not a major contributory factor to the elevated immunotoxicity of paper and pulp mill effluent in the seasons of high temperature. Received: 14 March 2000/Accepted: 28 July 2000     

Impact of Carbofuran in the Oocyte Maturation of Catfish, Heteropenustes fossilis (Bloch)

Investigations were undertaken to observe the influence of technical grade carbofuran (CF) on the egg maturational processes of catfish, Heteropneustes fossilis (Bloch). Fish were exposed to sublethal doses (0.5, 1, and 2 mg/L) of CF for 30 days at 25 ± 1°C. Control fish were maintained in water. The gonado-somatic index (G.S.I. = ovarian weight × 100/body weight) of the fish, treated with 1 or 2 mg/L CF, was decreased significantly compared to that of the controls. The inhibition was almost at the same level in these doses. CF at the dose of 0.5 mg/L was found to be ineffective. From the histomorphological observations of the ovary, it was observed that CF altered both the area and the percentage occurrence of the various types of primary oocytes in the ovary compared to that of the control fish. The stage I primary oocytes were predominantly higher in CF-treated fish than stage II and stage III which was reversed in control animals. The degeneration of follicular walls, connective tissues and vacuolization in the ooplasm of the stage II and III oocytes were observed in CF-treated fish (0.5–2 mg/L). It appears that CF at sublethal concentrations inhibits oocyte maturational processes in catfish. Received: 14 February 1996/Revised: 21 August 1996     

Carbofuran-induced histophysiological changes in thyroid of the teleost fish, Channa punctatus (Bloch)

The long-term toxic effects of continuous exposure for 6 months, from January to June, to a safe dose (4.5 ppm) of a commercial carbamate pesticide, carbofuran, on the histophysiology of thyroid in adult and young (yearling) Channa punctatus, are described in this investigation. In both the experimental groups, thyroid histology exhibited various abnormalities, including hypertrophy, hyperplasia and degeneration of follicular epithelial cells, and reduction in colloid content. Apart from this, in young experimentals, fibrosis of thyroid components, formation of cystic cellular masses, and rupture of blood vessels resulting in hemorrhage can also be seen and suggest direct action of this pesticide on the thyroid. On the other hand, in both treated groups, retardation of thyroid function was also evidenced by significantly reduced thyroidal radioiodine (131I) uptake and CR (conversion ratio of PB131I in blood serum in relation to total serum 131I uptake) values. Apparently, these histopathological and physiological changes were markedly pronounced in young experimentals, suggesting greater susceptibility of this group to chronic toxicity of carbofuran than that of adults. Thus, on the basis of these results, it can be inferred that carbofuran pesticide, which is washed into water systems in small quantities, induces adverse histophysiological alterations in thyroid, in an age- and size-dependent manner, possibly by acting directly on thyroid and/or through the hypothalamo-pituitary-thyroid axis, in this species.     

Haematotoxicity of Integrated Textile Mill Effluent to an Air-Breathing Fish Heteropneustes fossilis (Bloch)

The effect of integrated textile mill effluent on the haematological characteristic of the fish Heteropneustes fossilis was studied. LC₅₀ values were found to be 34 %–38 % on 96–24 h duration. Four sub-lethal concentrations were selected for this study. Exposure to effluent caused an increase in large lymphocytes, monocytes, neutrophils and basiphil granulocytes and decrease in small lymphocytes in H.fossilis.     

Toxic and sublethal effects of carbaryl on a freshwater catfish,Mystus vittatus (Bloch)

The effects of carbaryl (1-naphthalenyl methylcarbamate), commonly used in agricultural operations, have been studied with reference to survival, behavior, food intake, growth, and conversion efficiency of the catfishMystus vittatus. At a concentration of 32.5 ppm, carbaryl caused 100% mortality within 24 hr; the 72 hr LC₅₀ was 17.5 ppm. At concentrations of 12.5 ppm and below, it caused no mortalities within 72 hr. But such sublethal concentrations accelerated the swimming activity and increased the frequency of opercular beats. The latter response was dose-dependent. These behavioral changes were the immediate response to the toxicant and were indicators of possible stress. A 27-day exposure to sublethal concentrations of carbaryl led to a decrease in feeding rate and growth rate. The latter decreased from 10.15 mg/g/day (freshwater) to 2.84 mg/g/day (12.5 ppm). The reduced growth and conversion efficiency may be due to the expenditure of more energy for the purpose of maintenance. Therefore, the insecticide is considered to be a metabolic Stressor.     

Acute toxicity bioassays of mercuric chloride and malathion on air-breathing fish Channa punctatus (Bloch)

Acute toxicity tests (96 h) were conducted in flow-through systems to determine the lethal toxicity of a heavy metal compound, mercuric chloride, and an organophosphorus pesticide, malathion, to air-breathing teleost fish, Channa punctatus (Bloch) and to study their behavior. The 96-h LC50 values were determined, as well as safe levels. The results indicate that mercuric chloride is more toxic than malathion to the fish species under study. Dose- and dose-time-dependent increases in mortality rate were also observed in response to both test chemicals.     

Effect of malathion and endosulfan on brain acetylcholinesterase and ovarian steroidogenesis of Channa punctatus (Bloch)

The effect of sublethal concentrations of malathion (organophosphorus insecticide) and endosulfan (organochlorine insecticide) was investigated in Channa punctatus. Brain acetylcholinesterase (AchE) and ovarian delta 5,3 beta-hydroxysteroid dehydrogenase (delta 5,3 beta-HSD) and glucose-6-phosphate dehydrogenase (G-6-PD) activities were studied. Apart from the loss of stage II and III oocytes, the absence of delta 5,3 beta-HSD and G-6-PD activity indicating the inhibition of steroidogenesis was seen in the malathion- and endosulfan-treated fish ovaries. Malathion demonstrated a dose-dependent inhibition of brain AchE activity, whereas endosulfan caused no significant reduction of AchE activity.     

Cythion-induced histophysiological changes in thyroid and thyrotrophs of the teleost fish, Channa punctatus (Bloch)

The chronic effects of continuous exposure for 6 months, from January to June, to safe (2.0 ppm) and sublethal (4.0 ppm) concentrations of a commonly used organophosphorus pesticide, cythion, on the histophysiology of the thyroid and thyrotrophs in Channa punctatus are described in this investigation. The pharyngeal thyroid of fish of both treated groups exhibited hypertrophy and hyperplasia of the follicular epithelium and reduction of colloid content. Apart from this, in the fish exposed to 4.0 ppm, some of the follicles were exhausted and transformed into degenerated cystic masses. The presence of free blood cells at these sites suggests rupture of blood vessels and possible phagocytosis. These histopathological changes could be correlated with a significant and dose-dependent reduction of thyroidal radioiodine uptake and conversion ratio (serum protein-bound iodine:total serum iodine) values. After cythion exposure, the thyrotrophs in the pituitary were activated. These results suggest that the thyroid dysfunction caused by cythion may be responsible for the stimulation of the thyrotrophs which in turn stimulated the thyroid follicles through the pituitary-thyroid axis in this species.     

Carbofuran-induced histopathological and biochemical changes in liver of the teleost fish, Channa punctatus (Bloch)

In Channa punctatus exposed to a safe dose (4.5 ppm) of the commercial carbamate pesticide carbofuran for 6 months, from January to June, liver exhibited varying degrees of histopathological changes including cytoplasmolysis, nuclear pyknosis, and necrosis leading to complete exhaustion and disintegration of hepatocytes. In some regions of liver, extensive degeneration of proliferated hepatocytes, in close proximity to blood sinuses, looking like darkly stained debris of hepatomass and induction of tumors were indicative of carcinogenic action of this pesticide which may be attributed to its cumulative toxicity during chronic exposure. Apart from this, the rupturing of blood sinus causing invasive infiltration of leukocytes, and detrimental focal necrosis resulting in the complete dissolution of hepatocytes indicated by the presence of debris mass in the necrotic space can be seen. Moreover, in the liver of experimental fish, corresponding to cellular damage, a significant decrease in hepatosomatic index and ascorbic acid content and an elevation in acid and alkaline phosphatase levels were also recorded. These results suggest that carbofuran is capable of inducing histopathological and biochemical alterations in liver which may cause physiometabolic dysfunction in this species.