J.H.J. van Vuren

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 fertilizing capacity of cryopreserved sharptooth catfish (Clarias gariepinus) sperm

Abstract Ova of one female were inseminated with cryopreserved and fresh milt. Cryopreserved milt was stored in liquid nitrogen for 14 days and 16 months. The insemination ratio was 0.3 ml milt 20 ml (±7600) ova. Cryopreserved and fresh milt were equally effective during the hatching trials. Fertilization with both fresh milt and milt cryopreserved for 14 days resulted in a maximum of 51% hatched ova. Milt which was preserved for 16 months caused the hatching of 41% ova.

The effects of toxicants on the haematology of Labeo umbratus (Teleostei: Cyprinidae)

1. 1. The haematology of Labeo umbratus (Smith) was investigated after exposure to four toxicants under controlled static conditions. 2. 2. Statistically significant changes exist between the values of parameters of experimental and control fish. 3. 3. The concentration of haemoglobin fractions changes with different toxicants. 4. 4. Electrophoretograms of plasma proteins showed changing patterns as well as a decrease in fraction numbers.

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.

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.

Bioconcentration of atrazine in the banded tilapia, Tilapia sparrmanii

Abstract 1. The bioconcentration of atrazine was determined in the liver, muscle, heart, gonads and brain of Tilapia sparrmanii exposed to high concentrations of atrazine. 2. The highest concentrations were recorded in the ovaries (50.6 μg/g) and in the liver (40.1 ± 5.5 μg/g). This may be attributed to the higher lipid content of these organs, while the liver also accumulates atrazine as a result of its detoxification function. 3. The bioaccumulation factors for atrazine in the liver, muscle, heart, gonads and brain ranged from 0.9 to 20.0. Bioconcentration of atrazine in banded tilapia was found to be low, even after exposure to external atrazine concentration much higher than detected in natural surface water.

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.

Some ultrastructural observations of Leydig and Sertoli cells in the testis of Tilapia rendalli following induced testicular recrudescence

Transmission electron microscopical studies performed on the testis of Tilapia rendalli confirmed the presence of Leydig and Sertoli cells. These cells displayed characteristic morphological features and were positively identified in the interstitial tissue and lobules, respectively. Based on cytoplasmic features it appeared that Leydig cells were responsible for male sex steroid synthesis. Although no clear evidence of steroidogenesis was found in the Sertoli cells, they perform a phagocytic function in the seminiferous lobules.

Some physical properties of the semen from artificially induced sharptooth catfish (Clarias gariepinus)

Abstract 1. 1. A programme for the artificial induction of spermatogenesis and spermiation in Clarias gariepinus is presented. 2. 2. The physical properties of the semen were determined. 3. 3. Semen colour was white in all cases and mean values for the other physical properties were as follows: semen volume = 9.91 ml; spermatocrit = 27%; sperm count = 6.2 × 10 6 /mm 3 ; percentage live spermatozoa = 87% and total motility time = 118 sec.