H.H. du Preez

Effect of copper on the haematology and osmoregulation of the Mozambique tilapia, Oreochromis mossambicus (Cichlidae)

Abstract The haematology of Oreochromis mossambicus was investigated after short-term (96 hr) exposures to 0.16 mg/l and 0.40 mg/l, respectively, as well as long-term (4 wk) exposure of 0.40 mg/l copper, at two temperatures. After the exposure of two sublethal copper concentrations a physiological effect was exerted on O. mossambicus , at both temperatures, by causing changes in the blood biochemistry such as leucocytosis and erythrocytopenia. Morphological changes in the gills, as reflected by the decreases in the plasma sodium, potassium, calcium and chloride concentrations, although not lethal, had a significant effect on the respiration and osmoregulatory function of the gills. Those morphological changes can be regarded as primary changes, which will inevitably lead to secondary physiological changes as well as responses that could affect various organ systems. Changes can be seen as an initial response to copper (the toxicant) or as an adaptation reaction to retain a normal condition.

The effect of copper on the blood chemistry of Clarias gariepinus (Clariidae).

Environmental stressors, both natural and humanly induced, could cause changes in cellular function which alter the physiology of organ systems in fish. The need to comprehend and predict the condition which stress metals will pose on fish, and extrapolate the effect of pollutants from laboratory to population levels, have forced scientists to search for physiological and biochemical indicators of health and sublethal toxicant effects. Hematological evaluation of fish blood provides valuable facts concerning the physiological response of fish to changes in the external environment. Furthermore, hematological variables are well known for their clinical value in prognosis and diagnosis. Sublethal responses after exposure to toxicants can be determined by commonly applied techniques. Measurements for a number of hematological and carbohydrate metabolic variables were recorded at winter and summer temperatures after fish, acclimated for 3 months to experimental conditions, were exposed to sublethal concentrations of copper for 96 hr in a continuous-flow experimental system. Controls were run at the same time to establish essential baseline hematological values. Fish were exposed to the mean copper concentration as was found in the Olifants River, Kruger National Park, during summer (0.05 ± 0.032 mg liter−1) and winter (0.085 ± 0.032 mg liter−1) to establish the effect thereof on the variables mentioned. The results proved that the concentration of copper in the river exerts a physiological effect on Clarias gariepinus at 21 ± 1 and 28 ± 1°C which manifests in changed blood chemistry. Pathological conditions, such as erythrocytopenia, leucocytosis, hyperglycemia, and hyperprotonemia, are evident. The fish physiologically adapted to the environmental change, which does not necessarily reflect a state of normality.

EFFECT OF COPPER ON THE DIFFERENTIAL WHITE BLOOD CELL COUNTS OF THE MOZAMBIQUE TILAPIA (OREOCHROMIS MOSSAMBICUS)

Abstract An increase in the number of leucocytes (leucocytosis) is a normal reaction of the fish body, against attacks of foreign substances, such as copper, which can alter the normal physiological function in fish. Significant increases in the number of lymphocytes (lymphocytosis) and eosinophils (eosinophilia) combined with significant decreases in monocytes (monocytopenia) and neutrophils (neutropenia), are indicative of changes (infections) that set in after short-term (96 hr) exposure to copper. This finding was confirmed by the number of leucocytes of Oreochromis mossambicus that increased at both temperatures, to protect the body against infections that may have been caused by copper.

A comparative biochemical genetic study of three populations of domesticated and wild African catfish (Clarias gariepinus)

Abstract 1. 1. Gene products of 22 protein coding loci in two commercially used (domesticated) and one wild population of African catfish, Clarias gariepinus, were examined by horizontal starch-gel and vertical polyacrylamide-gel electrophoresis. 2. 2. Average heterozygosities of 0.0759 and 0.0033 for the domesticated and 0.0467 for the wild catfish population were calculated. 3. 3. Genetic distances indicated a greater similarity between geographically isolated (hatchery) populations than between hatchery and wild populations. 4. 4. Selection of breeding stock for aquaculture practices based on the above information is discussed.

The effect of hexavalent chromium at different pH values on the haematology of Tilapia sparrmanii (Cichlidae)

1. The haematology of Tilapia sparrmanii (Smith) was investigated after exposure to 0.098 mg.l-1 hexavalent chromium at three different pH values. 2. Statistically significant changes occurred between the values of parameters of experimental and control fish. 3. At lower pH values erythrocytosis and leucocytosis were evident. 4. At an alkaline (9) pH anaemic and leucopenic conditions were observed. 5. T. sparrmanii adapted to chronic exposure to hexavalent chromium.

Effect of copper on blood coagulation of Oreochromis mossambicus (Cichlidae)

The effect of copper on the blood coagulation in freshwater fish, Oreochromis mossambicus was investigated. These fish were exposed to sublethal copper concentrations over short-term (96 hr) and long-term (4 wk) periods, at 29 +/- 1 degree C (summer) and 19 +/- 1 degree C (winter), in experimental flow-through systems. Copper concentrations applied during short-term exposures were 0.16 mg/l and 0.40 mg/l, respectively, while 0.40 mg/l copper was applied during the long-term exposures. After a photocymographic observation of blood, during all the phases of coagulation was made, it was evident that there were delays in the blood coagulation times, as well as decreases in the shear modulus (elasticity) of the clots formed, after the exposure of the fish to copper concentrations at both temperatures. Copper was found to induce haemophilia at 29 +/- 1 degree C and 19 +/- 1 degree C, while at the latter it also induced thrombocytopenia. Thus exposure to copper lead to coagulation defects, which caused haemorrhage in the body tissue, which can eventually cause the death of those fish.

Routine oxygen consumption of Tilapia sparrmanii (cichlidae) following acute exposure to atrazine

Abstract 1. 1. The routine oxygen consumption was measured in Tilapia sparrmanii exposed to 8.1 mgl −1 active atrazine for 72 hr. 2. 2. Routine oxygen consumption of the experimental fish fluctuated for the first 6–10 hr of the acclimation period. 3. 3. The routine oxygen consumption of T. sparrmanii , without the addition of any toxicants over a 72 hr period showed a decrease for the first 48 hr, but stabilized thereafter. 4. 4. Application of atrazine resulted in a drastic decrease in oxygen consumption for 3 hr. 5. 5. Routine oxygen consumption of the experimental fish showed no significant decrease for the first 24 hr after atrazine application, while the second 24 hr revealed a significant increase and the third 24 hr compared to the control values, showed no significant increase. 6. 6. These results indicated that acute exposure of T. sparrmanii to atrazine did alter routine oxygen consumption.

Concentrations of zinc in Barbus marequensis from the lower Olifants River, Mpumalanga, South Africa

Zinc was detected in all the tissues examined, but in variable concentrations. The highest zinc concentrations were detected in the skin and ovaries. These zinc concentrations also differed significantly from the concentrations in the other tissues. The bioaccumulation pattern of zinc in the fish was determined as: skin >ovaries>liver>gills>vertebrae>testes>hindgut>foregut contents >kidney=foregut>hindgut contents>muscle>blood>fat>bile.Although significant differences (P<0.05) between localities were detected no clear trend as to where the highest bioaccumulation had occurred, could be established. Significant seasonal differences were detected, but it was not always the same tissue that indicates these seasonal differences. The zinc concentrations detected in the fish suggest no serious zinc pollution in the lower Olifants River. Zinc levels detected in some of the tissues might indicate chronic exposure, causing possible sub-lethal effects. However, this should be investigated before final conclusions can be made.

A comparison of growth performance and genetic traits between four selected groups of African catfish (Clarias gariepinus burchell 1822)

1. 1. Fast growing individuals (three groups) in a progeny batch of African catfish were identified and isolated from the main population. 2. 2. At the age of 36 weeks, the mean mass of two fast growing groups (169.6 and 232.0 g) was significantly (P < 0.05) higher than that of the rest of the population (88.8–108.7 g). 3. 3. A comparison of specific growth rates revealed that these differences were the result of superior growth at an early age. 4. 4. An electrophoretic evaluation of the different mass classes showed little or no difference between the LDH allele frequencies of the fast growing groups, but did indicate significant differences between the frequencies of fast and slow growing groups. 5. 5. The present study represents the first attempt to establish the role of genetic characteristics in the control of growth in African catfish, and suggests the feasibility of genetic selection for rapid growth in Clarias gariepinus.

Bioaccumulation of manganese in selected tissues of the freshwater crab, Potamonautes warreni (Calman), from industrial and mine-polluted freshwater ecosystems

Manganese concentrations in water and sediments of the Bronkhorstspruit River, Nooitgedacht Dam and especially in the Natalspruit River, did not fall within stated limits for the protection of aquatic life. Tissue manganese concentrations in Potamonautes warreni from the Natalspruit River were generally higher than those in the tissues of crabs from the other two aquatic ecosystems. The highest mean manganese tissue concentration in crabs from the three systems was detected in the carapace (587± 445 µg g-1 wet weight). It appears that the carapace in these animals acts as a sink in which manganese can be deposited, thus also playing an important role in the detoxification of manganese in these crustaceans. No seasonal or sex-related variation was detected. Body size of the crabs, however, seems to be an important influencing factor in manganese bioaccumulation. A significant increase in carapace manganese concentrations was detected with an increase in body size. However, muscle manganese concentrations were higher in the smaller groups.The concentration factors (BF) calculated for the different tissues with respect to the water were highest in the carapace and ranged from 280.9 to 742.8. The BF with respect to the sediment was comparatively low for all the tissues (0.1 to 0.7). As the manganese concentration in the tissues reflects to some extent the degree of manganese contamination of the surrounding aquatic environment, it appears that P. warreni may be useful as a potential biomonitor of manganese pollution.