Bacterial flora of the gut of the African snakehead, Channa obscura (Pisces: Channidae)

A qualitative and quantitative investigation of the bacterial flora of the gut of the African snakehead, Channa obscura was undertaken. The types of bacteria isolated from the different parts of the gut of C. obscura include Pseudomonas, Streptococcus, Citrobacter and Proteus. The coliform (Escherichia coli, Enterobacter) and some other Enterobacteriaceae such as Salmonella were also present. The stomach and intestine were found to have a preponderance of Pseudomonas and Vibrio species. Klebsiella sp. and Bacillus sp. (only in the pyloric caeca) were also isolated. On the whole, the correlation coefficients of the two incubation temperatures showed a high statistical significance. Thus the bacterial load of the gut of C. obscura has been shown as a function of temperatur

Sublethal haematological effects of zinc on the freshwater fish, Heteroclarias sp. (Osteichthyes: Clariidae)

Laboratory study was undertaken to evaluate some haematological changes resulting from the exposure of a freshwater fish, Heteroclarias sp. to sublethal concentrations (5.0 and 10.0 mg L-1) of zincin water for a period of fifteen (15) days. Three groups of ten fish were subjected to serial dilutions of the stock solution of zinc of 0 (control), 5.0 and 10.0 mg L-1 in three large plastic bowls of 60 litrescapacity by the semistatic (renewal) method. At the end of the 15 days exposure period, blood samples were taken from the control and experimental fish. Blood was assayed for selected haematologicalparameters (haematocrit, haemoglobin, red blood cell counts, white blood cell counts, differential white blood cell counts, erythrocyte sedimentation rate, total plasma protein and plasma glucoseconcentration). The derived haematological indices of mean corpuscular volume (MCV), mean corpuscular haemoglobin (MCH) and mean corpuscular haemoglobin concentration (MCHC) were calculated. Sublethal concentrations (5.0 and 10.0 mg L-1) of zinc caused a dose dependent decrease in haemoglobin values, coupled with a decrease in haematocrit values and red blood cell counts are obvious indication of anemia of the norm chronic type. The total white blood cell counts and the differential white blood cell counts were decreased except for the lymphocytes in which there was a slight increase. Plasma level of protein and glucose were also lower in the exposed fish when comparedto the control. The haematological indices MCHC, MCH and MCV were also lowered. In conclusion, the changes observed indicate that haematological parameters can be used as an indicator of zinc relatedstress in fish on exposed to elevated zinc levels

Carbohydrases In The Alimentary Canal And Associated Organs Of The African Snakehead, Parachanna Africans (Osteichthyes: Channidae)

Standard qualitative and quantitative methods were employed to determine the presence and activity of digestive carbohydrases in different regions of the alimentary canal and associated organs of the African snakehead, Parachanna africans. Qualitatively, amylase, maltase, sucrase, and lactase were present in the stomach, pyloric ceca, anterior and posterior intestine, liver and spleen. No carbohydrases were found in the esophagus whereas cellulase was com- pletely absent throughout the canal and organs. Quantitatively, a relatively large amount of lac- tase and maltase was found throughout the canal and organs (except the esophagus) while sucrase was active in varying degrees in all the canal regions and associated organs (except the esophagus)

Digestive enzymes in the alimentary canal of Clarias anguillaris (Pisces: Clariidae)

Three groups of digestive enzymes were observed in the alimentary canals of the fingerlings and adults of Clarias anguillaris. The enzymes were carbohydrases including amylase, sucrase, lactase and maltase, proteases including peptase, tryptase and peptidase, and lipase. The activities of the protease were found to be higher in the fingerlings than in the adults while carbohydrases' activities were higher in the adults than fingerlings. Amylase was most widely distributed, found in both fingerlings and adults and in every region studied; it was followed by lactase. Of the proteases, peptase was found to have the widest distribution. Lipase activity was found in the alimentary canal of the adults. Tropical Freshwater Biology VOL. 8 1999, pp. 55-63 KEY WORDS: digestive enzymes – carbohydrases – proteases – lipases - Clarias anguillari

Acute toxicity of potassium permanganate to fingerlings of the African catfish, Clarias gariepinus (Burchell, 1822)

Laboratory static bioassays were conducted to determine the 96-h LC50 and the lethal levels of concentrations of the aquaculture therapeutant, potassium permanganate (KMnO4) on fingerlings (meanweight, 6.24 ± 0.15 g and mean length, 4.25 ± 0.07 cm) of the African catfish, Clarias gariepinus. A total number of one hundred and eighty (180) fingerlings of mixed sex and brood stock were used for thetoxicity bioassay. The 96-h median lethal concentration (LC50) value obtained for treatment of the fingerlings of the catfish C. gariepinus with potassium permanganate was 3.02 mg/L KMnO4 with lowerand upper 95% confidence limits of 0.40 and 3.73 mg/L KMnO4, respectively. There was very strong and positive correlation between the variables (r = 0.96) with 93% (r2) association. Toxicity curve revealed 11.20 mg/L KMnO4 at 8.20 h as the threshold value for the 96 h assay of potassium permanganate on fingerlings of C. gariepinus. The 96 h LT50 for 10, 8 and 6 mg/L KMnO4 to the test fish were alsodetermined to be 10.40, 11.30 and 17.80 h, respectively. Varying behavioural patterns were observed in the fish, which included erratic swimming, loss of reflexes, total loss of equilibrium, paleness of skinand gasping for air. The value of water quality parameters monitored during the exposure period did not differ significantly (P>0.05) within the various concentrations of the therapeutant (KMnO4) as well aswith the control. However, pH and total alkalinity tended to increase with increasing concentration of the toxicant

Acute toxicity of refined oil on the catfish, Clarias gariepinus (Teugels, 1984) (Pisces: Clariidae)

Laboratory static bioassays were conducted to determine the 24-, 48-, and 96 -hour LC50 and the lethal levels of concentrations of oil-in-water dispersions (OWD) of used and fresh fuel oil for embryo, fry and fingerlings of the catfish Clarias gariepinus(Teugels, 1984). The most sensitive was the embryonic stage while the fingerlings were most resilient. The LC50 values obtained for treatment with fresh fuel oil were as follows: Embryos (24- and 48 -hour LC50) 0.034 ml/l and 0.042 ml/l respectively. For the fry (24-, 48-, 72- and 96-hour) the LC50 values were 1.22ml/l, 0.85ml/l, 0.83ml/l and 0.70ml/l respectively. The fingerlings had 48-, 72 and 96-hour LC50 values of 5.00 ml/l, 2.30 ml/l and l.78ml/l respectively. The LC50 values for treatment with used fuel oil were as follows: Embryos (24 - and 48 -hour LC50) 0.032 ml/l and 0.04 ml/l respectively. For the fry (24-, 48-, 72-and 96-hour LC50) values were 1.59 ml/l, 1.14 ml/l, and 1.12 ml/1 while the fingerlings had 0.82 ml/l, 1 .37 ml/l and 1.02 ml/l as their 48-, 72- and 96-hour LC50 values respectively. Loss of skin pigmentation was observed in fish exposed to fresh fuel oil and darker pigmentation in fish exposed to used oil. Activity generally decreased with increased concentration of toxicant and longer duration of exposure. A similar trend was observed for hatchability of the embryos. Increased mouth and opercular breathing were also observed. Tropical Freshwater Biology VOL. 8 1999, pp. 17-26 KEY WORDS: Petroleum-Refined Oil-Toxicity-Behaviour-Clarias gariepinus, Nigeria

Effects of sublethal concentrations of tobacco (Nicotiana tobaccum) leaf dust on some biochemical parameters of Hybrid catfish (Clarias gariepinus and Heterobranchus bidorsalis)

The aim of this work was to study the effect of tobacco (Nicotiana tobaccum) leaf dust at sublethal concentrations (375.6, 187.8, 93.9 0.0mg/L) on biochemical parameters of Hybrid catfish in a static semi-renewable bioassay system with the aim to ascertain its effect on the test fish after 14 days exposure period. The effects of the plant dust on the test fish was dose-dependent, revealing significant difference in albumin, glucose, triglyceride, cholesterol, urea, and uric acid of the serum, liver and kidney; total protein and globulin of serum and kidney and creatinine and calcium of the serum while insignificant difference were observed for calcium and creatinine in liver and kidney and total protein and globulin in liver compared to the control. The effect of the plant dust was most pronounced in the serum, less in the kidney and least in the liver. However, the monitored water quality parameters revealed that the plant dust had effects on primary productivity, thus the biodiversity of organisms