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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

'n Vergelykende studie van die kariotipes van Tilapia rendalli, T. sparrmanii en Oreochromis mossambicus (Cichlidae)

Swanepoel, Antoinette 17 November 2014 (has links)
M.Sc. / Please refer to full text to view abstract
2

Die effek van swaarmetale by variërende pH op die bloedfisiologie en metaboliese ensieme van Tilapia sparrmanii (Cichlidae)

19 November 2014 (has links)
M.Sc. / Please refer to full text to view abstract
3

Die biokonsentrering van atrasien, sink en yster in Tilapia sparrmanii (Cichlidae)

Van Rensburg, Engela Larya 17 November 2014 (has links)
M.Sc. / Please refer to full text to view abstract
4

Die effek van atrasien, sink en yster op die hematologie en suurstofverbruik van Tilapia sparrmanii (Cichlidae)

Grobler, Eurika 26 May 2014 (has links)
M.Sc. (Zoology) / Tilapia sparrmanii (Smith) obtained from the Provincial Fishery in Lydenburg was used for toxicological studies. The haematology of T. sparrmanii was investigated after exposure to sub-lethal doses of atrazine, zinc and iron for 72 hours in a continuous flow and static system, as well as prolonged (4 weeks) exposure in the continuous flow system. After exposure the blood of the experimental fish were sampled. Mean values and standard errors were obtained for several haematological parameters such as number of red and white blood cells, haematocrit, haemoglobin, mean corpuscular volume, pH, plasma glucose-, protein-, lipid- and lactate concentrations, as well as plasma Na+, K+, eland Ca+. Statistically significant differences were found between the values of haematological parameters of experimental and control fish. A tendency towards haemoconcentration was observed when fish were exposed to the low pollutant concentrations, while signs of haemodilution was found at higher concentrations. The results in this study demonstrate that, after prolonged exposure, T. sparrmanii develops a tolerance and partially recovers from the stress condition. The bioconcentration of atrazine in the blood of T. sparrmanii after exposure were determined by liquid chromatography and zinc and iron by atomic absorption spectrophotometry. During this study it was found that atrazine, zinc and iron concentrated in the blood of T. sparrmanii after short- and prolonged exposure to the pollutants. The routine oxygen consumption of "!'. sparrmanii exposed to atrazine, zinc and iron were determined in a continuous flow apparatus over 72 hours. The oxygen consumption of the experimental fish fluctuated for the first 8-12 hours during the acclimation period. The influence of atrazine on the routine oxygen consumption was not so drastic as that of zinc and iron. Zinc caused a decrease in the routine oxygen consumption of the experimental fish over 72 hours, while iron increased the routine oxygen consumption...
5

Die effek van swaarmetale by veriërende pH op lewerensieme en bloedstolling by Tilapia sparrmanii (Cichlidae)

Gey van Pittius, Marina 23 July 2014 (has links)
M.Sc. (Zoology) / Tilapia sparrmanii (Smith) was exposed to sub-lethal doses of chromium, manganese, zinc and iron for 96 hours at an acidic pH (5), a physiological pH (7,4) and an alkaline pH (9), as well as a prolonged exposure (2 - 4 weeks) at an uncontrolled pH. In the laboratory fish were kept in aquaria which were supplied with continuously flowing borehole water. Controlled laboratory conditions existed during experimentation. Blood and liver samples of the experimental fish were sampled after exposure. The bioconcentration and the effect of the selected metals at the mentioned conditions, were thereby determined on bloodcoagulation, total and differential leucocyte counts, and liver enzYmes to investigate the possible damage to the liver. As metals have the ability to enter and concentrate in the body, the bioconcentration of each metal was determined by atomic absorption sPectrophotometry in the blood and liver. Chromium showed an increase in concentration in both the blood and liver, with an increase in pH after short term (96h) exposure. The statistical significant increases of manganese concentration in the blood over a short term were not reflected in the liver. It may be indicative of homeostatic control. A similar phenomenon was found with .zd.nc , The concentration of zinc in the liver did not reflect the progressive decrease in the blood wi th a increase in pH. Iron revealed a statistical significant increase in bioconcentration in the liver with, an increase in pH, which is indicative of the activity of the liver. The long term exposure of fish to chromium and manganese caused a significant increase in the concentration of the metals in the blood and liver. The only significant increase in concentration after exposure to iron, occured . in the Iiver. Exposure to zinc however caused a statistical significant decrease in concentration in both the blood and liver. Differential leucocyte counts reflected lymphocytosis, eosinophilia, monocytopenia and neutropenia, after short term exposure. These conditions nearly always resulted in leucopenia. Long term exposure to manganese and zinc reflected both eosinophilia and neutropenia. Chromium reflected eosinophilia, and iron, neutropenia. The only statistically significant change in the number of leucocytes after long term exposure, was caused by zinc and resulted in leucopenia. According to the photokymographic observation of blood coagulation by the thrombelastograph, exposure to the selected heavy metals lead to a prolonged clotting time and thrombocytopenia. Long term exposure (4 weeks) to manganese caused another bleeding disease, called hemophilia. It was thus evident that the exposure to heavy metals led to clotting defects, which caused bleeding.
6

Ondersoek na die broeigedrag asook die moontlike effek van omgewingsfaktore op eierproduksie by Tilapia sparrmanii Smith, 1840 (Pisces: Chichlidae)

Stutterheim, Irene Margaret 08 May 2014 (has links)
M.Sc. (Zoology) / Please refer to full text to view abstract
7

The effects of copper and effluent on certain life stages of Xenopus laevis and Tilapia sparrmanii

13 August 2012 (has links)
M.Sc. / The increase in industrialisation, mining and agricultural activity along rivers could have a detrimental effect on aquatic environments unless the dangers of pollutants are not taken notice of. Metal ions and industrial effluent have become a source of pollution in the watercourses of South Africa. Pollutants generally have negative effects on the physiology of aquatic biota in polluted waters. The effects of copper and industrial effluent by the exposure of the clawed toad, Xenopus laevis and Tilapia sparrmanii are presented in this study. An experimental static-renewal system with an exposure time of 96 hours was followed at 25±1°C. After copper and effluent exposure, several physiological changes occurred in the two aquatic organisms. The sublethal effects that occurred include changes in hatching, survival, behaviour, growth impairment and developmental limitations. The results of the present study suggest that lethal endpoints can be used as indicators in detecting and evaluating the effects of aquatic pollution, caused by copper and effluent. Individual variation, however, could hamper the conclusions made but the study of aquatic organisms is of practical importance when conducting experimental studies in a laboratory and does not have the same impact as during field studies. Apart from the exposure to sublethal concentrations of copper and effluent, computational derivations of LC50, NOEC values and 95% confidence limits were made. The obtained concentrations were used as assumptions that pollutants should not exceed for the protection of aquatic life. Statistically different differences were found between the chosen derived variables of control and experimental organisms. The advantages of FETAX solution over borehole water can be attributed to the bioavailability of pollutants, which appears to be much less in those solutions. The predicted NOEC values provide some information regarding the concentrations at which no effects will be observed and the Target Water Quality Ranges (TWGR) for water were used to determine if the diluent was correct.
8

Fish health, condition and biomarkers : a mechanistic and environmental perspective on copper pollution / Daléne van Heerden

Van Heerden, Daléne January 2005 (has links)
Thesis (Ph.D. (Zoology))--North-West University, Potchefstroom Campus, 2005.
9

Fish health, condition and biomarkers : a mechanistic and environmental perspective on copper pollution / Daléne van Heerden

Van Heerden, Daléne January 2005 (has links)
Thesis (Ph.D. (Zoology))--North-West University, Potchefstroom Campus, 2005
10

Fish health, condition and biomarkers : a mechanistic and environmental perspective on copper pollution / Daléne van Heerden

Van Heerden, Daléne January 2005 (has links)
Thesis (Ph.D. (Zoology))--North-West University, Potchefstroom Campus, 2005

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