Magister Scientiae - MSc (Biodiversity and Conservation Biology) / Heavy metal accumulation in arable land as a result of mining activities, pesticides and fertilisers has become a global concern. Steinkopf and Concordia in the Northern Cape are well-known for subsistence farming, but just as well-known for the nearby copper mining industry. Very little research has been done on heavy metal toxicity in these areas, thus it was of importance to assess the wheat cultivars (Triticum aestivum) historically used in the study areas, to ensure the viability of wheat farming. The nine wheat cultivars screened were Flameks, Knoppies, Rooiwol, Rooigys, Yecoro Royo, Charchia, Witwol, Kariega and Losper. A comparative study was done by determining the concentration levels of Cu, Fe, Zn, Mn, K, Mg, Ca, Na, N and P in the roots and shoots of sensitive and tolerant wheat cultivars. It was established that Witwol and Rooigys were the most tolerant to these adverse conditions. Kariega and Rooiwol were most sensitive. Their tolerance was achieved by excluding copper from the roots and limiting the translocation of copper to the shoots. This trend to exclude copper uptake in Witwol and Rooigys, warrants further investigation on a molecular level to explain these adaptive mechanisms. / South Africa

M.Sc. (Zoology) / There has been an increasing concern worldwide regarding the possible adverse effects of pharmaceutical supplements present in our aquatic ecosystems and whether or not they modify the physiological functioning in humans and wildlife. Trenbolone acetate (TBA) and zeranol (Z) for example, are two commonly used synthetic anabolic growth promoting hormones in cattle production. TBA is metabolized into trenbolone-β and excreted as both trenbolone-α and -β. In liquid manure trenbolone-β has a half-life of over 270 days and Z, 120 days. Therefore if released into the surrounding environment there is the possibility for long-term severe ecological impacts i.e. fish reproduction and general health. The aim of this study was to determine the physiological effects of several growth promoting hormones used as growth promoting hormones in cattle production on the Mozambique Tilapia – Oreochromis mossambicus. The growth promoting hormones assessed in this study were; Trenbolone acetate, Methyltestosterone, Diethylstilbestrol and Zeranol. The aim was accomplished by making use of histology (gills, liver and gonads) and three biomarker assays; Glutathione-S-transferase (GST), Uridine-Diphosphate Glucuronosyltransferase (UDPGT) and Cellular Energy Allocation (CEA). Stock solutions of Trenbolone acetate (14 μg/l and 15 μg/l), Methyltestosterone (7 μg/l and 7.5 μg/l), Zeranol (2.8 μg/l and 3 μg/l) and Diethylstilbestrol (0.28 μg/l and 0.29 μg/l) were prepared. Fish were exposed under controlled conditions for a period of 24-hours, 4-, 15- and 30-days respectively using a flow-through system. The aquarium water was changed (45 L removed and replaced with 45 L of prepared growth hormone containing bore-hole water) every 48 – 72 hours to remove all waste material thus ensuring the aquariums were clean. Upon performing the necropsies, gills, liver and gonads were removed and examined using standard histological techniques. Muscle tissue was used to determine the CEA, liver and kidney tissue was used for both GST and UDPGT assays. The results obtained from the histology revealed that the gills and liver were not severely affected by exposure to the growth promoting hormones although possible exposure related alterations were evident. The gonads results indicated that exposure to the growth promoting hormones severely affected the morphology and functioning of the organs to the point where reproduction is questionable. The results obtained from the hepatosomatic index (HSI) and gonadosomatic index (GSI) revealed no significant differences (p<0.05) although a trend of increasing HSI and decreasing GSI was evident in the male fish exposed to the androgens. With regards to the biomarker assays there were minor decreases in CEA in the exposed fish but no significant differences (p<0.05) could be established. The GST assay revealed that Zeranol prompted a significant increase (p<0.05) in GST activity in the kidney after 4- and 15-days of exposure while the liver displayed no change in GST activity. The UDPGT assay revealed minor fluctuation in UDPGT activity in both the kidney and liver throughout the study, however, no significant differences (p<0.05) could be established. To conclude, exposure to these growth promoting hormones at the selected concentrations and exposure periods severely compromised the fish’s reproductive capabilities thus challenging the fish’s fitness. Further studies examining the energy metabolism and xenobiotic detoxification pathways of the Mozambique tilapia and other indigenous fish species are recommended to better comprehend the effects that these growth promoting hormones may possess.

D.Sc. / Please refer to full text to view abstract

M.Sc. / During the last decade, Cape Wagtails (Motacilla capensis) have been observed with several forms of feet abnormalities, such as missing toes and clubbed feet. The aim of this research was to find the reason for these abnormalities. The initial hypothesis was that ‘Feet abnormalities in the Cape Wagtail (M. capensis) are caused by the internal action of contaminants (e.g. pesticides and metals) through direct contact and/or secondary poisoning’. Wagtails were caught with mist nets and/or ground traps depending on the area and accessibility of the sampling sites. Wagtails with feet abnormalities, as well as those without, were caught at six localities around South Africa. Indicators of pollutant exposure and effect were studied. The bioaccumulation of certain metals (measures of exposure) in the feathers such as aluminium (Al), arsenic (As), cadmium (Cd), chromium (Cr), cobalt (Co), copper (Cu), iron (Fe), Pb, nickel (Ni), manganese (Mn), silver (Ag), strontium (Sr) and zinc (Zn) and Al, As, calcium (Ca), Cd, Cr, Co, Cu, Fe, Pb, Ni, Mn, Ag and Zn in the blood plasma were analyzed on the Inductively Coupled Plasma Mass Spectrometry (ICP-MS). Biomarker testing (measures of effect) was carried out in the blood such as acetylcholinesterase (AChE) which tested for nerve transmission inhibition, ä-aminolevulinic acid dehydratase (ALA-D) which tested for lead (Pb) bioaccumulation, catalase (CAT) which tested for the invasion of oxyradicles and oxidative stress and DNA damage which tested for DNA band length alteration caused by stress due to xenobiotics. Biomarker outcomes and metal analysis results were carried out on a site comparison basis. Acetylcholinesterase, ALA-D and DNA damage were found not to be linked to the occurrence of feet deformities at these sites. However, CAT revealed stress at all the sites which may have indicated the presence of a stress (or stresses) which could have been caused by feet abnormalities or other factors. A non-metric multidimensional scaling graph (NMDS) ordination suggested that biomarkers were not grouped according to sites that had affected birds and those that did not, but were rather assorted. Consequently, few real differences in biomarker responses were noted between healthy and affected birds. Catalase enzyme activity and DNA damage were suggested to be indicative of feet abnormalities although results were not convincing. Secunda displayed the highest concentrations of metals in the feathers when compared to the other sites. Most metals were higher than reference values for contaminated areas and recent South Africanreported concentrations. Almost all of the metals tested at each site exceeded the Ecological Quality iii Objectives (EcoQOs) for metals in bird feathers, based on Weavers (Ploceus sp.) in the Gauteng region. Zinc levels at all the sites posed some concern. Chromium and Ni were suspected to possibly trigger feet and toe abnormalities in Cape Wagtails. Levels of various metals in the plasma were higher at sites that had no deformities. This suggested that these metal concentrations did not cause or influence feet or toe deformities. Calcium levels were found to be lower at sites with affected birds which indicated that the deformities may perhaps be caused by decreased Ca concentrations. Metal concentrations were higher than the uncontaminated reference levels, but were lower than contaminated site reference values. / Prof. V. Wepener

M.Sc. / A lot of research in ecotoxicology is currently focused on identifying and developing suitable biomarkers for use in assessing the health of aquatic systems. Thus this study was done as part of a major project aimed at identifying and selecting suitable biomarkers to use in the Rietvlei System, South Africa. This study focused on the response of Clarias gariepinus (Burchell, 1822) to contaminants using three biomarkers: population genetic structure, DNA damage and metallothioneins (MT¡¦s). The main objectives of the study were to assess the potential of these biomarkers in C. gariepinus and to provide baseline data on the Rietvlei System. Eighteen enzyme loci (creatine kinase (Ck), esterase (Est), phosphoglucomutase (Pgm), glycerol-3-phosphate dehydrogenase (G3pdh-1 and -2), glucose-6-phosphatase isomerase (Gpi-A and -B), L-lactate dehydrogenase (Ldh-A and B), malate dehydrogenase (sMdh-1, -2 and -3), malate dehydrogenase (NADP+) (Mdhp), phosphogluconate dehydrogenase (Pgdh), isocitrate dehydrogenase (NADP+) (Idh); superoxide dismutase (Sod), and peptidase: substrate (leucyl tryrosine) (Pep-S1 and -2)) were screened for by horizontal starch gel electrophoresis. An agarose gel electrophoretic method was used for DNA damage determination and a spectrophotometric method for metallothionein. The Rietvlei System population (RSP) showed higher genetic variability as shown by the average number of alleles per locus (A), proportion of polymorphic loci (P) and expected average heterozygosity (HE) than the reference populations. Statistically significant deviations (p < 0.05) from Hardy-Weinberg proportions associated with heterozygote deficiencies occurred at Gpi-B, Idh, Pgdh, Ldh-A and Pep-S1 for RSP. These deviations could have been a result of small sample size. There was high genetic differentiation between RSP and the reference populations with FST values of 0.450 and 0.480 between RSP and wild population (WP) and RSP and Northern Cape population (NCP) respectively. A mean base-pair length of 6770.9 „b 10.68 (SE) bp was recorded in the Marais Dam population (MDP) that of 6327.2 „b 17.69 (SE) bp was recorded in the Rietvlei Dam population (RDP). The MDP had a higher proportion of DNA fragments with low base-pair lengths than RP indicating a higher level of DNA damage. The level of DNA damage in the MP was higher than in the RDP. The mean MT¡¦s content was 3.63 „b 0.643 (SE) nmol g-1 wet weight in the MDP and 4.35 „b 0.580 (SE) nmol g-1 wet weight in the RDP. There was no significant (p = 0.40) difference in the levels of MT¡¦s between the two dams. It was concluded that there were significant differences in genetic diversity between RSP and the other populations in unpolluted sites; hence genetic diversity in C. gariepinus has potential as biomarker of pollution. However, further research is recommended to investigate possible contributing factors to differences in genetic diversity such as inter-sex males, geographical isolation and differences in sample sizes used. DNA damage is also a potential biomarker provided due care is taken in interpreting average base-pair length data to consider differences in each DNA size class. It seems further research is required before conclusions are made about use of MT¡¦s as biomarker in this population. The levels of MT¡¦s in other uncontaminated systems will be useful to determine whether the levels recorded in this study are background levels or responses to contamination. / Prof. F.H. van der Bank

M.Sc. / Please refer to full text to view abstract

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This study examined the extent to which physiological and psychological concomitants of aerobic terrestrial performance were affected by body cooling of varying degrees induced by cold water immersion (CWI). Thirteen male and 13 female subjects underwent three randomly assigned 30 min treadmill runs: a control run without prior manipulation of the subjects' thermal status and the same exercise after "central" (core temperature 1°C below pre-immersion) and "peripheral" cooling (skin heat loss 100kcal.m⁻².h⁻¹). During treadmill runs core temperature was measured, together with chest, leg, arm and hand temperatures, from which mean skin temperature (T [subscript]s[subscript]k) and mean body temperature (T[subscript]b) were calculated. Heart rate, oxygen consumption (VO₂,), carbon dioxide production (VCO₂), minute ventilation (V₂ (BTPS)), breathing frequency (f), cadence and ratings of perceived exertion (RPE) and thermal sensation (PTS) were also measured. Both central and peripheral cooling resulted in significantly reduced T[subscript]r[subscript]e (males : control 37.9±0. 3°C; central cooling : 36.8±0.5°C; peripheral cooling: 37.5±0.4°C; females: control: 37.9±0.4°C; central cooling: 37.2±0.5; p<0.05) during subsequent treadmill running, except following peripheral cooling for females (37.9±0.3°C) . For males and females T[subscript]s[subscript]k was lower following peripheral cooling than control values and lowest after central cooling (males: control: 30.0±1.3°C; central cooling: 36.8±0.5°C; peripheral cooling: 37.5±0.4°C; females: control: 30.5±1.2°C; central cooling: 25.9±1.8°C; peripheral cooling: 26.9±1.9°C; p<0.05). Female subjects experienced significantly higher T[subscript]r[subscript]e than males following central and peripheral cooling and a lower T[subscript]s[subscript]k following central cooling. Females experienced less of an increase in heart rate than males during exercise following central and peripheral cooling (control: l57.7±23.7b.min⁻¹; central cooling: 143.5±20.5b.min⁻¹; peripheral cooling 151.7±16.7b.min⁻¹; p<0 .05). Male responses were the same following central cooling but higher for peripheral cooling than control values (control: 139.1±7.3b.min⁻¹; central cooling 134.7±17.5b.min⁻¹; peripheral cooling: 145.0±16.4b.min⁻¹; p<0.05). These data indicate a depression in cardiovascular function for females following peripheral cooling that was not apparent for males. The VO₂ was not different between tests for males; only peripheral cooling resulted in a raised VO₂ of 28.6±3 .3ml.kg⁻¹.min⁻¹ (p<0 .05) for females compared to 27.6±2.6ml.kg⁻¹.min⁻¹ (control). A biphasic response was evident for VO₂ VCO₂ and V[subscript]B (BTPS). For both sexes overall RPE was lower for peripheral cooling (males: 9.4±1.9; females: 8.7±1.3; p<0 .05) than for control and central cooling. Central RPE was only changed for females following peripheral cooling. Changes in cadence and step length together with the effect of low skin and leg temperatures resulted in higher local RPE for females after central cooling (9.6±1.2; p<0.05) than control (9.4±1.9) and peripheral cooling (8.9±1.2 ). Males and females rated the same ambient temperature during the same exercise lower after peripheral cooling (males: 4.6±1.5; females : 5.3±1.3) than control values and lower still after central cooling (males: 3. 8±1.8; females: 2 .7±l. 5) In this study T[subscript]s[subscript]k was the primary determinant of PTS after precooling. / KMBT_363 / Adobe Acrobat 9.54 Paper Capture Plug-in

No description available.

Plants that develop under foliar shade encounter both low photosynthetically active radiation (PAR) and low red to far red ratios (R:FR). Both of these factors are important in determining developmental responses to shade. Papaya (Carica papaya L.) seedlings grown under filtered shade (low PAR and low R:FR) were compared with seedlings grown under neutral shade (low PAR with R:FR similar to that of full sunlight), and high light (moderate PAR with R:FR similar to that of full sunlight). The results indicated that papaya exhibits a light seeking strategy as evidenced by morphological and anatomical differences between treatments. Based on past research the results also indicate shade developmental responses in papaya to be phytochrome mediated.