Vanadium induced changes in glycogen content of Clarias batrachus (Linn) and Channa punctatus (Bloch)

Clarias batrachus (Linn) and Channa punctatus (Bloch) were exposed to 5, 10 and 15 ppm of vanadium and investigated the effects on tissue glycogen at 3, 6 and 9 hrs. Results indicated the variations in the level of glycogen were highest at 15 ppm after 9 hr exposure in liver than muscle, brain, kidney and heart of Clarias batrachus as compared to Channa punctatus. The variation recorded in tissue glycogen content was discussed in relation to respiratory distress, formation of mucus on the whole fish and disturbed behaviour of the fish.     

Acute and chronic toxicity of nitrite to Clarias lazera

The present study is an attempt to define acute (96 hr) and chronic (6-months) effects of nitrite on two different sizes of juvenile Clarias lazera. Static bioassays on acute toxicity showed median tolerance limit (TLm) for four days of 28 and 32 mg/l NO2-N for the two sizes respectively. Although nitrite is known to cause hypoxia, as a result of oxidation of haemoglobin to methemoglobin, exposure of both sizes to nitrite resulted in a decreased erythrocyte count haemoglobin content and haematocrit values. Fish exposed to nitrite responded physiologically by producing methemoglobin. A decline in serum total protein levels was recorded during acute and chronic exposure of both sizes to nitrite. This was interpreted as a generalized stress response.     

Hematological responses of the Neotropical teleost matrinxã (Brycon cephalus) to environmental nitrite

Environmental increase in nitrite impairs the function of several aquatic species, including fishes. Nitrite reacts with hemoglobin yielding the non-functional methemoglobin (metHb), and many physiological disturbances can arise. The physiological mechanisms to cope with nitrite are still unclear in fish. Hematological parameters, the role of NADH-methemoglobin reductase system and the electrolytic balance were studied in the freshwater teleost Brycon cephalus (matrinx?) exposed to 0.2, 0.4 and 0.6 mg/L of nitrite N-NO(2) for 24 and 96 h. Hematocrit, total hemoglobin and the red blood cell (RBC) number decreased. Methemoglobin content increased from 1% to 69% for 24 h of exposure and drastically from 5-6% to 90% for 96 h. The activity of NADH-methemoglobin reductase system displayed a tendency of increase in response to nitrite concentration or time of exposure. In the plasma, nitrite was accumulated to values 30-fold higher than the environmental concentration. The plasma K(+) concentration increased only in fish exposed to NO(2) for 24 h. No changes in plasma protein and Na(+) were observed during nitrite exposure but Cl-presented a punctual increase at 0.2 mg/L N-NO(2)-96 h. The hematological data suggest that nitrite caused functional and hemolytic anemia. Furthermore, the electrolytic balance was relatively undisturbed, and the nitrite clearance in matrinx? is likely depending on other factors than NADH-methemoglobin reductase system.     

Chloride inhibition of nitrite uptake for non-teleost Actinopterygiian fishes

Fish that transport environmental chloride with a gill uptake mechanism (gill epithelial Cl(-)/HCO(3)(-)cotransport exchange system), also transport nitrite into plasma through the same mechanism. Because of the relationship between nitrite uptake and the gill chloride uptake mechanism, nitrite uptake can provide insight regarding the method of chloride uptake for fish. This study was designed to determine if non-teleost fishes concentrate nitrite in their plasma, and to determine if chloride inhibits nitrite uptake in non-teleost fish. To determine if bowfin Amia calva, spotted gar Lepisosteus oculatus, alligator gar Atractosteus spatula, and paddlefish Polyodon spathula concentrate environmental nitrite in their plasma, individuals were exposed to concentrations of 0, 1, 10, or 100 mg/L nitrite-N. After exposure, all species had plasma nitrite-N concentrations greater than environmental levels. To determine if chloride inhibits nitrite uptake for spotted gar, alligator gar, and paddlefish, fish were exposed to 1 mg/L nitrite-N and 20 mg/L chloride as calcium chloride, or to 1 mg/L nitrite-N only. Chloride effectively prevented nitrite from being concentrated in the plasma of all species. It appears that non-teleost fish concentrate nitrite in their plasma via their chloride uptake mechanism and that this is an ancestral characteristic for teleost.     

The African sharptooth catfish Clarias gariepinus can tolerate high levels of ammonia in its tissues and organs during four days of aerial exposure

The African sharptooth catfish Clarias gariepinus lives in freshwater, is an obligatory air breather, and can survive on land during drought. The objective of this study was to elucidate how C. gariepinus defends against ammonia toxicity when exposed to terrestrial conditions. During 4 d of aerial exposure, there was no accumulation of urea in its tissues, and the rate of urea excretion remained low. Thus, exposure to terrestrial conditions for 4 d did not induce ureogenesis or ureotely in C. gariepinus. Volatilization of NH(3) was not involved in excreting ammonia during aerial exposure. In addition, there were no changes in levels of alanine in the muscle, liver, and plasma of C. gariepinus; nor were there any changes in the glutamine levels in these tissues. However, there were extraordinarily high levels of ammonia in the muscle (14 micromol g(-1)), liver (18 micromol g(-1)), and brain (11 micromol g(-1)) of fish exposed to terrestrial conditions for 4 d. This is the first report on a fish adopting high tolerance of ammonia in cells and tissues as the single major strategy to defend against ammonia toxicity during aerial exposure. At present, it is uncertain how C. gariepinus tolerates such high levels of ammonia, especially in its brain, but it can be concluded that, contrary to previous reports on two air-breathing catfishes (Clarias batrachus and Heteropneustes fossilis) from India, C. gariepinus does not detoxify ammonia to urea or free amino acids on land.     

Short-term effects of mercury on survival, behaviour, bioaccumulation and ionic pattern in the catfish (Clarias lazera)

1. The fresh-water fish, Clarias lazera, was exposed to 13 lethal and sublethal concentrations of mercury. 2. The median tolerance limit (TLm) at different exposure periods, 24, 48, 72 and 96 hr, appears to be as follows: 0.96, 0.88, 0.81 and 0.72 ppm Hg2+/l, respectively. 3. From the subacute tests, the maximum acceptable toxicant concentration (MATC) for this fish was between 0.10 and 0.22 ppm Hg2+/l. 4. Behavioural changes, tissue Hg2+ distribution and serum ionic patterns were recorded during both the acute and subacute exposure periods.     

The growth and feeding habits of Clarias anguillaris during their first season in the floodplain pools of the Sokoto-Rima river basin, Nigeria

The growth and feeding habits of juvenile Clarias anguillaris (Linné 1762) during their 5-month residence in the floodplain pools of the Sokoto-Rima river basin are described. A mean growth increment of 202 mm and 69.7 g attained in the October to March season compares favourably with first-year growth recorded for other Clarias species. The diet of C. anguillaris is relatively unspecialized and includes a wide variety of items ranging from algae, higher plant material and detritus through larval dipterans, rotifers and copepods, to fish. There is variation in the diet according to month of capture and capture location, and a reduction in diet diversity with fish size. The findings are discussed in the context of work carried out on other Clarias species. It is proposed that C. anguillaris is suitable for locally operated fish culture programmes.     

Acute effects of nitrite on ion regulation in two neotropical fish species

To broaden the understanding of physiological responses of tropical fish to environmental stressors, the effects of nitrite on haematological parameters and plasma and red blood cell ion regulation were studied in two neotropical fish species, Astyanax altiparanae and Prochilodus lineatus. Both fish species were exposed to NaNO2 (30 mg l(-1)) over a 96-h period and blood samples were taken for ion and haematological analyses. The results revealed that nitrite leads to a decrease in P. lineatus blood haematocrit and haemoglobin content and an increase in blood methaemoglobin. A. altiparanae did not exhibit any significant difference in these haematological parameters. During the exposure to NO2- both fish species had significantly reduced plasma Na+ concentration and red blood cell (RBC) K+ concentration, but only P. lineatus showed an increase in extracellular K+ concentration. When RBC volume was analyzed in vitro, after 2 min of exposure to NaNO2, a 36% shrinkage was observed in P. lineatus cells, while only a 10% shrinkage was observed in A. altiparanae cells. These results suggest that for P. lineatus, nitrite entrance into the cell leads to methaemoglobin formation and K+ efflux, causing red cell shrinkage and increased plasma K+. However, A. altiparanae proved to be a species more resistant to nitrite, exhibiting fewer responses to this compound.     

Changes in the kidney peroxidase activity in fish exposed to some industrial pollutants.

Fish under abnormal environmental conditions suffer from retarded growth and other physiological dysfunctions related to thyroxine deficiency. In teleosts lacking a definite thyroid gland the kidney plays a very important role in biosynthesis of the thyroidal hormone, in which peroxidase has an indirect action. Effects of some industrial pollutants and factory effluents on fish kidney peroxidase activity were recorded in Ophicephalus punctatus and Clarias batrachus. At concentrations of the pollutants at which 70-100% of the fish survive the exposure, peroxidase activity was greatly inhibited, indicating that even sub-lethal doses of toxicants may cause drastic changes in the physiological systems. The peroxidase activity increased well above the control levels at 5-h and 27-h exposures in some cases, but declined towards the end of the test.     

Effect of sublethal levels of nitrite on some blood parameters of juvenile Labeo rohita (Hamilton-buchanan)

Juveniles of L. rohita were exposed to sublethal levels of nitrite (0.02, 0.1 and 0.4 mg/l) for 2, 24, 48 and 96 hr. The time of exposure at individual concentrations of nitrite did not show any significant difference in haemoglobin, cortisol, chloride and lactic acid. Haematocrit showed significant reduction with increasing concentration of nitrite irrespective of duration of exposure. Fishes exposed to 0.4 mg/l nitrite showed significantly high levels of glucose beyond 2 hr. The mean erythrocytic fragility of fishes exposed to the 3 concentrations of nitrite for 3 exposure periods showed significant higher sensitivity to osmotic stress. The results suggest decrease in haematocrit and cell wall strength of erythrocytes creating stress to fish.     

In vivo impact of monocrotophos on biochemical parameters of a freshwater fish during subacute toxicity and following cessation of exposure to the insecticide

In vivo toxicity of monocrotophos on key metabolites and enzymes of the protein metabolism was investigated in important tissues of the freshwater fish Clarias batrachus. Fish were exposed to 1/10 and 1/20 of LC50 concentration for 28 days. After 28 days of exposure, some fish were transferred to monocrotophos-free water and kept in the same for 21 days (recovery period) in order to study the recovery response. Total protein, amino acid, and ammonia contents were decreased in gill, kidney, liver, and muscle tissues, and recovery was slight at the end of 21 days of transfer of fish into freshwater. Urea and glutamine levels were elevated, except in kidneys, and recovered at the end of the recovery period. The activities of protease, transaminase, and phosphatase enzymes were elevated in all tissues during 28 days of exposure and at both concentrations. Recovery of the activity of enzymes was more significant at the lower concentration as compared to the higher concentration.     

Stress response of juvenile Clarias lazera elicited by copper

1. Experiments were conducted with juvenile Clarias lazera to investigate the influence of acute copper exposure on bioaceumulation and some haematological constituents (erythrocyte count, haemoglobin content and haematocrit value).2. Analyses of copper residues in liver, kidney, muscle, gills, brain and blood after 96-hr exposure period revealed that liver and kidney accumulated the greatest amount of copper, while the other organs were found to accumulate relatively smaller concentrations.3. All blood samples collected from copper-treated fish showed some haemolysis. In addition, significant decreases in the values of the 3 parameters were noted. The anaemia reported is therefore of the haemolytic type, possibly due to the effect of copper on membrane ATPase, the glycolytic enzymes in the erythrocytes and glutathione.     

Effects of Waterborne Copper, Cyanide, Ammonia, and Nitrite on Stress Parameters and Changes in Susceptibility to Saprolegniosis in Rainbow Trout (Oncorhynchus mykiss)

The effects of toxic exposures on the susceptibility of rainbow trout (Oncorhynchus mykiss) to saprolegniosis were evaluated. Fish were exposed to sublethal concentrations of copper (0.25 mg/liter), cyanide (0.07 mg/liter), ammonia (0.5 mg/liter), and nitrite (0.24 mg/liter) for 24 h. After exposure, the fish were challenged by Saprolegnia parasitica (3.6 x 10(sup6) zoospores per liter) for 10 min. Cortisol and cholesterol were used to indicate stress response. Similar increases of cortisol were found for the four tested chemicals. All fish with cortisol levels higher than 370 ng/ml developed the disease, while only 24% of the fish with cortisol levels lower than 370 ng/ml were infected. Cholesterol levels remained unchanged after toxic exposure. Increased susceptibilities to the pathogen were observed for ammonia (71%), copper (57%), nitrite (50%), and cyanide (33%). The increases in susceptibility as a result of cyanide and nitrite exposure could be explained by the stress response. For copper and ammonia, the combination of two different effects, the stress response and specific impairments of the defense mechanism of trout against saprolegniosis, should be considered.     

The effect of inorganic and organic pollutants on sperm motility of some freshwater teleosts

Using four different sperm types from brown trout Salmo trutta fario (Salmonidae), chub Leuciscus cephalus (Cyprinidae), burbot Lota lota (Gadidae) and African catfish Clarias gariepinus (Clariidae) the effect of inorganic (cadmium, copper, mercury, lead, zinc and nitrite) and organic (cyclohexane and 2,4‐dichlorophenol) environmental pollutants on sperm motility was investigated. Spermatozoa were activated in double distilled water containing the different test substances and the motility was compared to controls of similar pH. From the investigated motility variables the sperm motility rate and swimming velocity reacted most to the environmental pollutants whereby the changes depended on the species and on the test substance. African catfish spermatozoa were the most resistant, chub and burbot spermatozoa showed medium resistance and brown trout spermatozoa were the most sensitive to the pollutants. With exception of 2,4‐dichlorophenol and zinc the effective concentrations of the tested pollutants exceeded the recommendation for surface waters 100–10·000‐fold and were in a range lethal for the fish themselves. Therefore, it was concluded that fish sperm motility is not a suitable marker for risk assessment of environmental pollutants.     

Digestive enzymes of three teleost fishes.

The activity of amylase, sucrase, protease and lipase has been examined in Wallago attu, Clarias batrachus and Labeo rohita. The optimum pH value for carbohydrases ranges from 5.0 to 7.0 and that for trypsin between pH 6.8 and 7.8. Lipase is active at a slightly more alkaline medium. The optimum pH for a given enzyme varies in different sections of the alimentary canal of the same fish and also from species to species. Variations are also found in the optimum substrate concentration for a given enzyme in the different sections of the alimentary canal. The activity of carbohydrases is higher in the herbivorous fish Labeo, than in the carnivorous fish Wallago, and the omnivorous fish Clarias. As for protease, maximum activity is found in Wallago. The difference is not so well marked for the activity of lipase. There is a correlation between the normal diet of the fishes and the relative activity of the digestive enzymes.     

The toxicity to Clarias lazera of copper and zinc applied jointly

1. The acute toxicity to juvenile Clarias lazera of a mixture of copper and zinc over a 96 hr exposure period was determined. Fish were exposed to the summation of half the 96 hr TLm value of each toxicant. 2. Percentage survival was much reduced indicating that the metals potentiate each others lethal action. 3. Comparison between metal residues in fish exposed to copper and zinc or to their mixture showed that the uptake of one metal was decreased by the presence of the other. 4. Toxic effects of the mixture on the physiological parameters studied were mainly attributable to copper, indicating that the presence of zinc did not influence the mode of action of copper.     

Three Egyptian trematodes of fish-eating mammals of family Cyathocotylidae (Poche, 1926)

Fifty-eight specimens of cyathocotylid flukes were collected from dogs fed on the fish Clarias lazera: 10 Duboisia, 27 Mesostephanus appendiculatus; and 21 Prosostephanus industrius. This is the first time that these genera have been identified as parasites of C. lazera. The danger of human infection with these trematodes by means of C. lazera and other commercially important fish is stressed.     

Vanadium toxicology – an assessment of general health, haematological aspects and energy response in an Indian catfish Clarias batrachus (Linn)

The pervasive occurrence of vanadium in nature and its use in various industrial processes has increased its inputs in the environment. This has prompted us to elucidate the impact of vanadium on aquatic environ-ment, the primary body for industrial effluent discharge. The energy response of the fish, Clarias batra-chus, its haematological status including haemoglobin (Hb), haematocrit (Ht), leutocrit (Lt), mean corpuscular haemoglobin (MCH), mean corpuscular volume (MCV), mean corpuscular haemoglobin concen-tration (MCHC) etc. And overall general health conditions have been observed to be significantly hampered leading to deleterious alterations in the general metabolism of the fish following long term exposure to vana-date. The increase in muscle and tissue lactic acid (2–12 fold) in association with decrease in pyruvic acid (72% in mucle; 26% in liver) reflect a shift towards an anaerobic metabolism of the fish. We conclude that vanadium could be toxic for the fish in question under long term exposure at the doses under observation (2–10 mg L).© Rapid Science 1998     

Seasonality in expression and distribution of nitric oxide synthase isoforms in the testis of the catfish, Clarias batrachus: Role of nitric oxide in testosterone production

Nitric oxide (NO) is a well-recognized versatile signaling molecule. It is produced by catalytic action of nitric oxide synthase (NOS) on L-arginine in a variety of animal tissues. Existence of different isoforms of NOS has been shown in mammalian testis, but report on their presence in the testis of ectothermic vertebrates is non-existent. This study demonstrates the differential expressions of two isoforms of nitric oxide synthase (neuronal-nNOS and inducible-iNOS) like molecules in different cell types in the testis of seasonally breeding catfish, Clarias batrachus through immunohistochemistry. Positive immunoprecipitation of nNOS and iNOS like molecules were detected in germ cells as well as interstitial cells only in the recrudescing and fully mature fish. The immunoreactions differed in intensity and varied with changing reproductive status. Treatment of adult male fish with NO donor, sodium nitroprusside, and a NOS inhibitor, N-nitro-L-arginine methyl ester (L-NAME) increased and decreased the total nitrate and nitrite concentration in the testis, respectively. Sodium nitroprusside and L-NAME also induced simultaneous decline and rise in the testicular testosterone level, respectively. These findings, thus, suggest that NOS isoforms are expressed variedly in different cell types in the testis of reproductively active fish. This investigation also suggests that NO inhibits testosterone production in the testis.     

胡子鲶的胚胎发育

用无膜卵的培养方法,比较详细地观察了胡子鲶胚胎发育的过程,并从早期个体发育的本质着眼提出了卵裂、细胞分化和器官分化三个主要胚胎发育阶段。分析了胚胎发育与环境条件的适应性。根据胡子鲶胚胎发育的特点,初步讨论了苗种生产中应该注意的几个问题,同时提出胡子鲶可以作为鱼类细胞工程研究的一个比较理想的实验鱼材料。