Masters Degrees (Biological Sciences)

Permanent URI for this collectionhttps://hdl.handle.net/10413/12380

Browse

Now showing 1 - 20 of 70

The financial and economic feasibility of biodigester use and biogas production for rural households.
(2011) Smith, Michael Trevor.; Blignaut, James N.; Goebel, Jessica Schroenn.
In South Africa, sustainable development is set in the context of two separate economies. The second of these economies consists of the rural population and is characterised by poverty and stagnant development. Sustainable development is an increasingly topical concept which highlights the need for development to proceed in a manner that does not deplete natural resources. In addition to narrowing the gaps between the various classes (layers) in an economy, the key ‘ingredients’ of sustainable economic development include “natural resource management, food, water, and energy access, provision and security” (Blignaut, 2009: cited in Blignaut and van der Elst, 2009: 14). A biodigester is a potential solution to some of the difficulties faced by remote rural populations. Biodigester systems are submerged tanks capable of producing a nutrient rich fertiliser and combustible gas when consistently fed with organic matter and water. A biodigester may be one simple answer to the key ingredient needs of sustainable development – reducing the depletion of natural resources, providing clean burning energy for cooking and fertiliser for growing food. The potential is clear for biodigesters to aid in the process of sustainable development. The question to be analysed is whether this technology would be financially and economically feasible for installation and use in rural households. This thesis focuses on a typically remote and rural community in KwaZulu-Natal, South Africa, in order to assess the potential feasibility of a biodigester system. The appraisal takes the form of a Cost Benefit Analysis (CBA) and aims to establish whether or not this technology is financially feasible for individual rural households and/or economically beneficial to society.
Water stress effects on growth, development, resource capture and resource use efficiency of two contrasting sugarcane genotypes.
(2014) Ngxaliwe, Sivuyile.; Singels, Abraham.; Eksteen, Alana.; Pammenter, Norman William.
Abstract available in PDF file.
Prevalence and genetic relatedness of Besnoitia besnoiti isolates from different geographical regions of South Africa.
(2015) Malatji, Mokgadi Pulane.; Mukaratirwa, Samson.; Chitanga, Simbarashe.
Bovine besnoitiosis is a protozoan disease caused by an apicomplexan parasite Besnoitia besnoiti and is reportedly re-emerging in Europe and occurring in many other countries including South Africa. The disease has long been neglected and has only recently started getting attention due to its increasing geographical distribution. This parasite causes significant economic losses due to reduced body condition, declined milk production, irreversible sterility in males and mortality. This study was conducted to determine the prevalence of Besnoitia besnoiti infection in cattle, as well as to establish the phylogenetic relationship among parasite isolates in different geographical regions of South Africa, where the disease was previously reported. A total of 688 cattle (688 blood and 376 skin samples) were randomly sampled from farms located in Limpopo, Gauteng, KwaZulu-Natal and Eastern Cape provinces of South Africa. Based on the analyses of DNA sequences of the nuclear ribosomal internal transcriber spacer 1 (ITS1), it was observed that 15.7% (108/688) of the sampled animals were positive, with 5.3% (20/376) and 14.4% (99/688) of the animals being positive on skin and blood samples, respectively. 2.9% (11/376) of the animals were positive on both blood and skin samples. The difference between in prevalence between the areas sampled were not significant, χ² = 0.263. The parasite was more prevalent in communal farms (30.8 %) and in exotic breeds (35.3 %) than local or mixed breeds, and the difference in prevalence between farming and breed type were not significant (χ² = 0.199, χ² = 0.227 respectively). Aligned sequences were analysed by Maximum parsimony, neighbour joining and maximum likelihood and phylogenetic analysis of the isolates was carried out. Results showed that, based on the ITS1 region, our isolates were closely related to the wildebeest strain which is currently used for the manufacture of the vaccine, forming a clade which is separate from the European strains. One of the isolates from Gravelotte, Limpopo province, was closely related to the European strains, forming a sister clade for the European strains from GenBank. This is the first report on molecular characterisation of the parasite in South Africa and will aid in disease surveillance and control in the studied areas.
A phylogeny of South African east coast intertidal rocky-shore Polychaete worms (Annelida) and the genetic structure and demographic history of an example, Marphysa corallina.
(2015) Kara, Jyothi Ashok.; Macdonald, Angus Hector Harold.
The Annelida is an evolutionarily ancient invertebrate taxon. Recent studies have found that the formerly described sister taxon of the Polychaeta, Clitellata, is a derived Polychaete group thus making Polychaeta a paraphyletic group. Polychaete worms represent one of the most diverse invertebrate groups and are well represented in a variety of environments such as temporary freshwater puddles, rocky intertidal shores, estuaries and the abyssal plain. Polychaetes are fundamentally important in their environments as many are regarded as ecosystem engineers. Phylogenetic relationships within the Polychaeta are poorly understood and some species level classifications are uncertain due to the large number of polychaete worms present. In Chapter two, the phylogenetic relationships within the commonly found polychaete families (Nereididae and Eunicidae) were analysed using the universal mitochondrial cytochrome oxidase subunit 1 (COI). Within Eunicidae, analyses supported a polyphyletic Marphysa and Eunice which is consistent with previous results as individuals from both genera are nested among one another. Within Nereididae, relationships between genera and species were poorly supported and complex. Genera did not form exclusive clades but instead grouped with one another. A large degree of homoplasy has been recorded for the family which could have attributed to the convoluted groupings. Thus it has been suggested that genera from both Eunicidae and Nereididae be revised. Marphysa corallina is a poorly studied Eunicid polychaete which has a tropical indo-west distribution. It was observed to be a common worm among others on the intertidal rocky shores of KwaZulu-Natal and the Eastern Cape. In Chapter three, the population genetic structure and demographic history of M. corallina was investigated using two genes: universal mitochondrial cytochrome oxidase subunit 1 (COI) and the nuclear intron spacer region (ITS1). Diagnostic taxonomic characters were used to identify and validate the specimens as Marphysa corallina. The COI marker revealed that populations were highly connected to one another and formed a large panmictic population whereas ITS1 showed shallow genetic structuring of populations. Family Eunicidae individuals are known to lack a long lived planktonic larval stage which could not have contributed to panmixia as demostrated by the COI marker. Demographic results indicated that populations had recently undergone sudden expansions which could have falsely resembled highly connected populations. Estimation of divergence times places the expansions in the mid to late Pleistocene. Populations had not reached migration-drift equilibrium thus contemporary population distributions of Marphysa corallina along the east coast of South Africa are largely shaped by past climatic events such as in the Pleistocene.
Mapping the expression of key functional genes associated with murine corneal endothelial development.
(2015) Bengtson, Michel Leigh.; Sommer, Paula.
The cornea is a complex, layered, transparent structure that is responsible for transmitting and refracting light to ensure vision. Of all the layers, the corneal endothelium is physiologically the most important layer. Its principle function is to regulate deturgescence, a requirement for corneal transparency. Corneal deturgescence is regulated by key functional genes that include a network of tight junctions, water channels and ion pumps. In this study, we created an in vitro model of murine corneal endothelial development by immortalising endothelial cells at significant stages in corneal endothelial morphogenesis. Primary cultures of presumptive corneal endothelial cells were immortalised from wild-type mouse embryos at embryonic day (E) 14.5 and E15.5, and mature corneal endothelial cells were immortalised from wild-type pups at post-natal day (P) 13. These cell lines, together with already established cell lines at earlier stages in corneal endothelial development (E12.5 and E13.5), were used to map the expression patterns of three functional genes associated with corneal endothelial function, Zo1, Aqp1 and Slc4a4. Zo1 is a tight junction protein that facilitates the formation of the resilient monolayer that is characteristic of the corneal endothelium. Aqp1 is a water channel protein that mediates transcellular fluid transport while Slc4a4 is an ion pump that transports cellular bicarbonate ions across plasma membranes. Aqp1 and Slc4a4 are disease target genes which is indicative of their functional significance in corneal endothelial physiology. Quantitative real-time PCR (qPCR) and western blot analysis showed that Zo1 expression at both mRNA and protein level was progressively down-regulated from E12.5 to E15.5, after which it was up-regulated at P13 (p˂0.05 relative to E15.5 at mRNA level). Aqp1 gene expression was up-regulated at E13.5, with subsequent down-regulation at E14.5. Thereafter, Aqp1 gene expression was up-regulated at E15.5. Interestingly, Aqp1 gene expression was significantly down-regulated at P13 when the endothelium is completely matured (p˂0.05 relative to all other cell lines). Western blot analysis demonstrated Aqp1 expression throughout development in this model. Densitometric analysis showed that glycosylated Aqp1 protein expression levels decreased gradually from E12.5 to P13. Unglycosylated Aqp1 protein expression was only present at E12.5 and E13.5, and was up-regulated at E13.5. Slc4a4 was expressed at low levels during corneal endothelial development. However, it was highly expressed at P13 (p˂0.05 relative to all other cell lines). Protein expression for Slc4a4 could not be determined due to the lack of a commercially available antibody specific for murine Slc4a4. Confocal microscopy analysis demonstrated the protein localisation patterns for Zo1 and Aqp1 in monolayer and hanging drop culture, mimicking the 3D environment in which corneal endothelial development occurs. The results of this study provide valuable insight into the expression patterns of key functional genes associated with corneal endothelial development.
Efficacy of maslinic acid and chloroquine on the co-infection of Plasmodium berghei and Trichinella zimbabwensis in Sprague-Dawley rats.
(2015) Gcanga, Lorna.; Mukaratirwa, Samson.; Masola, Bubuya.
Many people living in Africa and elsewhere in the tropics suffer from combined malaria, soil-transmitted infections and tissue-dwelling nematodes. Most of these deaths are prevalent in sub-Saharan Africa (SSA) where the infections overlap, which often results in co-infection. Malaria and trichinellosis are one of the most important zoonotic diseases especially in sub-Saharan Africa caused by Plasmodium spp. and Trichinella spp., respectively. New drugs targeting malaria and trichinellosis have been examined with little success. The aim of our study was to determine and compare the efficacy of maslinic acid and chloroquine on the co-infection of muscle-dwelling larvae of Trichinella zimbabwensis and Plasmodium berghei in rats. Fifty-four Sprague-Dawley rats with an average weight of 150g and 200g for males and females respectively were infected with T. zimbabwensis and P. berghei. Infected rats were randomly assigned to nine groups which were subjected to treatments of maslinic acid and chloroquine and a combination of maslinic acid and chloroquine. Co-infected groups were infected with T. zimbabwensis on day 0, and then infected with P. berghei on day 30 post-infection (pi). Treatment was administered for 3 consecutive days on day 9 pi with P. berghei. Groups infected with P. berghei only were infected on day 0 and were treated on day 9 pi for 3 consecutive days. Groups infected with T. zimbabwensis only were infected on day 0 and treated on day 25 pi. Untreated control groups were a placebo (distilled water) on day 25 pi infected with T. zimbabwensis and from day 9 pi infected with P. berghei. In Trichinella-infected groups, the efficacy of each treatment measured by the rate of the reduction in muscle larvae was significant (P < 0.05) for both drugs compared to the untreated control group. In malaria-infected groups, the efficacy of each treatment, measured by the rate of reduction in parasitaemia, was significant (P < 0.05) for both drugs compared to the untreated control group. There was no apparent synergistic effect due to the combination of the two drugs in reducing the muscle larval burden and in reducing malaria parasitaemia. In all the treatment regimens, the reductions were significant when compared to the untreated control groups and not significant to each other (P > 0.05). From these results we can conclude that the efficacy of maslinic acid on the co-infection of T. zimbabwensis and P. berghei was comparable to that of chloroquine, making maslinic acid a promising drug to be used as an anthelmintic and anti-malaria against muscle larval stages of Trichinella spp. and malaria parasitaemia and no side effects were observed.
Technique establishment for in vitro selection of drought tolerant sugercane genotypes.
(2015) Mhlanga, Philisiwe Felicity.; Watt, Maria Paula Mousaco Deoliveira.; Snyman, Sandra Jane.
There is a need to have constant supply of sugarcane varieties adapted to different South African regions. However, the genetic improvement and selection of sugarcane cultivars with superior traits, e.g. drought tolerance, are difficult due to its complex polyploid and aneuploid genome. Biotechnology approaches are being investigated for the selection and/production of drought tolerant cultivars. Towards this end, the aim of this study was to establish: 1) the best source of meristematic explant for initiation and mass propagation of in vitro shoots; 2) in vitro conditions to screen and select for drought tolerance; and 3) physiological parameters as indicators of drought tolerance in vitro. Sugarcane stalks and shoots from single-budded setts of NCo376 were used. From the former, 1.3 cm-long meristems were isolated and used for shoot induction, shoot multiplication and rooting. The single-budded setts (approx. 50 mm) were first germinated in 20 ml sterile water or sterile moist paper, resulting in 100% and 60% sett contamination, respectively. With 1 mg lˉ¹ methylene blue (MB) there was 30% sett contamination, whilst 1 mg lˉ¹ MB in combination with 1 ml lˉ¹ Previcur® or 1 ml lˉ¹ BRAVO® resulted in 40% and 7% contamination, respectively. The uncontaminated germinated shoots (approx. 1 - 2 cm) were excised after 10 days in culture and used as the other source of meristems. Meristems from both sources were multiplied and rooted in vitro and their plantlet yield was 60 shoots/sugarcane stalk meristem and 10 shoots/meristem from in vitro-germinated sett. NCo376 and N41 varieties were used to determine the effect of mannitol (204, 326, 448 and 569 mM) on in vitro plantlet shoot and root re-growth. For both, increased mannitol in the media delayed shoot and root re-growth, with NCo376 being affected first. Stress was more significant on root than on shoot re-growth. For NCo376 plantlets, there were significant differences in root re-growth between 0 and 204 mM and the other tested treatments. For N41 plantlets, % root re-growth at day 10 on 569 mM mannitol was significantly higher than that at the other treatments. At 4 – 10 days, % shoot re-growth of NCo376 on 0 and 204 mM mannitol was greater than that at 326, 448 and 569 mM mannitol. Similar results were observed with N41 plantlets. The LD₅₀ and LD₉₀ for mannitol were 332 and 606 mM for NCo376, and 851 and 1493 mM for N41. There was no differences between the effects of polyethylene glycol-6000 (PEG-6000) and mannitol on root re-growth at the same osmotic potential. However, PEG-6000-containing cultures required to be aerated. As at 87 mM PEG-6000, NCo376 plantlets showed 50% root re-growth compared to 10% in non-aerated cultures, mannitol was used in subsequent investigations. Mannitol concentrations equivalent to LD₅₀ and LD₉₀ for NCo376 and N41 were used to screen N12, N36, N19 and N26 varieties. Based on the results obtained, the varieties were ranked on their tolerance to mannitol stress: N41 > N26 > N36 > N12 > N19 > NCo376. Leaf electrolyte leakage, leaf chlorophyll content measured with Soil Plant Analysis Development (SPAD) measurements, and histochemical detection of hydrogen peroxide (H₂O₂) (with nitroblue tetrazolium) and superoxide anion (O₂⁻˙) (with 3, 3’-diaminobenzidine) production were evaluated as indicators of stress using N41, N26, N19 and NCo376 on 332, 606 or 851 mM mannitol. N19 and NCo376 plantlets on 332 mM mannitol showed a higher % electrolyte leakage at day 5 (70%) than at day 10 (40 – 50%) of culture than N41 and N26 plantlets. A slight decrease in chlorophyll content was recorded at day 10 of culture in 332 and 851 mM mannitol, with no differences between NCo376 and N19, and N41 and N26. NCo376 and N19 accumulated more H₂O₂ than N41 and N26. O₂⁻˙ accumulation was also greater in NCo376 and N19 than in N41 and N26. All these parameters detected stress at lower levels of mannitol (332 and 606 mM), but not at 851 mM. It was concluded that mannitol stress in vitro (332 – 606 mM), in combination with the physiological assays allow for the discrimination of in vitro osmotic stress among sugarcane varieties. Further work is necessary before recommendations can be made regarding the use of the other stress biomarkers.
Lichen photobiology in relation to climate change : protection in peltigeralean lichens against excess ultraviolet (UV) radiation using induced melanins and the effects of UV on melanin synthesizing enzymes.
(2015) Matee, Lusanda Patrick Herbert.; Beckett, Richard Peter.
Depletion of the stratospheric ozone has allowed more solar ultraviolet (UV) radiation (100-400 nm) to reach the lower atmosphere. Despite the success of the continued implementation of Montreal protocol of 1987 and its amendments aimed at the protection of the ozone layer, it is possible that UV will remain elevated in some regions due to decreasing removal by clouds and aerosols. Strong interactions between ozone depletion and changes in climate induced by increasing greenhouse gases could result in increased UV radiation levels reaching the surface. Increased exposure to UV-B can cause significant damage to organisms including protein damage, inhibition of photosynthesis, formation of high energy reactive oxygen species (ROS), disruption of nitrogen fixation and induction of cell mutation and inhibition of growth. Lichens are composite organisms that arise from a symbiotic association between fungi and photoautotrophic algal partners, which may be microalgae and/or cyanobacteria. They have developed several protective strategies to protect themselves from excessive radiation. Lichens such as Cladonia rangiferina, Lobaria pulmonaria and Umbilicaria rossica are known to synthesize melanins in response to elevated levels of UV-B radiation. Synthesis of melanins is generally catalysed by enzymes that are involved in phenol coupling including P450 monooxygenases, ascorbate oxidases, peroxidases, laccases and tyrosinases (Nezbedová et al. 2001). The work presented in this thesis investigated the enzymes involved in melanin biosynthesis in lichens from suborder Peltigerineae. We present a detailed characterization of redox enzymes from Lobaria pulmonaria and Pseudocyphellaria aurata with a special focus on tyrosinases. Furthermore, an evaluation of the response of L. pulmonaria to UV radiation was done. The role of the redox enzymes tyrosinases, laccases and peroxidases in melanin synthesis is elucidated by exposing L. pulmonaria thalli to various combinations of UV and PAR. Laboratory experiments clearly indicated that L. pulmonaria and P. aurata have redox enzymes that are of similar nature to those of their free-living symbionts and other lichens. Tyrosinase from L. pulmonaria oxidized monophenolic compounds and was able to metabolize L-DOPA, thus showing characteristics of a typical fungal tyrosinase. L-DOPA can also be metabolized by peroxidases and laccase suggesting that peroxidases and laccases may participate in melanisation reactions. A field experiment showed that exposing shade-adapted L. pulmonaria to solar radiation in the field induces DOPA melanin synthesis. The synthesis of the brown cortical compounds occurred when lichen thalli were exposed to direct sunlight or placed under a wavelength neutral filter that marginally reduced overall light. Melanin synthesis was accompanied by an increase in laccase activity in lichens that were exposed to natural sunlight. By contrast, no changes in enzyme activity occurred in lichen thalli placed under the wavelength neutral filter. Placing lichen thalli under filters that removed both UV-A and UV-B prevent melanisation and was accompanied by an increase in tyrosinase activity. Filtering out UV-B had no effect on enzyme activity but slight browning occurred. Results showed that laccases could be involved in melanin biosynthesis under some conditions, but provided no evidence for a role of tyrosinases in melanisation. However, it could be that melanisation requires tyrosinase, but rates of melanisation are controlled by the levels of melanin precursors such as tyrosine. No differences in maximal PSII efficiency and chlorophyll contents occurred between the radiation treatments indicating that no deterioration of photosynthetically apparatus occurred and the photobionts remained relatively healthy even when exposed to UV. Taken together these results suggest that further research in needed into determining the levels of melanin precursors, the roles of lichen redox enzymes in melanin synthesis and whether a transcriptional activation of these redox enzymes by UV radiation in lichens exists or not. Furthermore, additional roles for tyrosinase need to be investigated, for example defence against pathogens.
Behavioural responses of rodents to the scent and taste of compounds associated with sugar and protein degradation : implications for the evolution of chemical signals in rodent-pollinated flowers.
(2015) Records, Darryn.; Johnson, Steven Dene.; Nicolson, Susan W.
Volatile compounds in nectar may influence the behavioural responses of animal flower visitors, and thus have fitness consequences for both animal and plant mutualists. Rodents may use certain volatiles associated with sugar fermentation or protein degradation as a cue to locate food. Plants pollinated by rodents may thus emit these volatiles to enhance their attractiveness to rodents. However the presence of certain compounds in nectar may also indicate reward degradation, reducing its attractiveness to potential pollinators. The effects of these compounds on small mammal flower visitors are largely unknown and the consequences of nectar degradation by microorganisms for small mammal flower visitors need investigation. The present study examines the responses of a known rodent pollinator, the Namaqualand rock mouse Micaelamys namaquensis, an occasional floral visitor, the four-striped field mouse Rhabdomys pumilio, and a closely-related congener, the mesic four-striped field mouse Rhabdomys dilectus towards four compounds - ethanol, ethyl acetate, acetic acid and dimethyl disulphide - that are associated with the degradation of sugars and proteins. The study aimed to: (i) Identify if fermentation and protein degradation volatiles act as behavioural cues for small mammals, and have the potential to assist in the finding of food resources; and (ii) to determine the responses of rodents to the taste of volatiles in nectar. In chapter 1, I investigated whether fermentation and protein degradation volatiles elicit a behavioural response in small mammals, using a traditional Y-maze choice apparatus. Rodent species differed in their responses to the four volatiles tested. Ethanol emerged as an attractant for all of the species, with the strongest response seen at the 0.3 % ethanol concentration, while only R. dilectus responded positively to dimethyl disulphide. Acetic acid and ethyl acetate were generally not attractive. In chapter 2, the palatability of fermentation and protein degradation compounds at varying concentrations in experimental nectars was tested. A paired choice test analysis was used to determine if animals altered their choice with the addition of volatiles to sucrose solutions (0.73 and 1.46 M). Rodents showed a dose-dependent response towards the volatile concentrations presented to them. Both M. namaquensis and R. pumilio preferred medium (0.3 %) concentrations of ethanol in high sugar concentration diets, but found this compound distasteful in lower sugar concentration diets. Acetic acid and ethyl acetate were generally not preferred by any species at either sugar concentration. Dimethyl disulphide was preferred by all species when present in greater sugar concentrations (1.46 M) and at low volatile concentrations (0.003 %). These results suggest that rodents do alter their choice of nectar in relation to the tested compounds. I conclude that certain compounds associated with sugar fermentation or protein degradation have the potential to act as behavioural cues in rodent pollination and that further studies to reveal the effect of nectar degradation by microorganisms are needed to help in understanding plant-pollinator interactions.
The leaf secretory apparatus of Hibiscus surattensis and Hibiscus sabdariffa (Malvaceae) : micromorphology, histo-phytochemistry and ultrastructure.
(2015) Raghu, Kashmira.; Naidoo, Yougasphree.; Nicholas, Ashley.
The research presented here forms the basis of the ethnobotanical and ethnopharmacological evaluation of Hibiscus surattensis, which is a widely distributed vegetable and medicinal shrub used by African and Indian traditional practitioners. Using light microscopy together with advanced electron microscopy techniques, the leaf topography and internal structure was examined. A closely related species, Hibiscus sabdariffa was also investigated for foliar and histophytochemical comparisons. Hibiscus sabdariffa is a widely consumed medicinal species with well-known biological activity and known chemical principles. Both species belong to the section Fucaria within the genus Hibiscus. Analyses of foliar secretory tissues showed that both H. surattensis and H. sabdariffa were characterised by capitate trichomes as well as mucilage-producing ducts and idioblasts. Head cells of capitate trichomes were between 5 and 7, while lignified stalk cells occurred in numbers of 2 or 3. A basal cell supporting the trichome was implanted in the epidermis comparative study between the two species showed some variation of chemical composition in trichome head cells. Polysaccharidic, alkaloids, phenolic and acidic lipid components were identified for both H. surattensis and H. sabdariffa whereas H. sabdariffa showed an intense staining of proteinaceous substances. Densities of capitate trichomes varied from emergent to mature developmental stages, with the highest number occurring on the emergent abaxial surface for both H. surattensis and H. sabdariffa. However, a distinct trend was observed for H. surattensis, where a decrease in capitate trichomes with progressive development was associated with the proliferation of mucilage idioblasts, particularly on the mature adaxial surface. Mucilage producing tissues are assumed to be associated with a protective role against dehydration in a number of plant families. Idioblasts observed in H. surattensis were visible leaf surface structures, embedded in the epidermal tissues. They contained considerable amounts of acidic polysaccharides and acidic lipids, and appeared to be implicated in reducing evaporative water loss in fully expanded leaves. Mucilage ducts were identified in vascular tissue within leaf veins. They occurred parallel with the conducting tissue and comprised of an epithelial layer of cells which seemed to be secreting a mucilage into an extracellular lumen. Crystal idioblasts were also identified in tissues of both H. surattensis and H. sabdariffa. The sequestration of calcium oxalate is assumed to be governed and regulated by specialised mesophyllous idioblasts that in turn appeared to be triggered by excess calcium within the plant body to differentiate into crystal forming cells. The supposed function of calcium oxalate crystals includes mechanical support and herbivory avoidance. TEM revealed the cellular processes which involved crystal idioblast development in H. surattensis. This appeared to demonstrate that degeneration of organelles which are assumed to occur when crystals reach maximal proportions. The non-glandular trichome component of each Hibiscus species was diverse in trichome type and might have accounted for differences in leaf texture and the leaf indumentum. The prickly texture of Hibiscus surattensis was attributed to rigid stellate and falcate trichomes as well as restrorse prickles, whereas the leaves of H. sabdariffa were glabrous with few falcate, bi- and trifurcate trichomes found mainly at the base or along the midvein. Preliminary phytochemical experiments which involved methanolic, chloroform and hexane extracts, yielded favourable results, which showed that leaves of H. surattensis and H. sabdariffa were chemically similar, in this regard, the author recommended further investigation into the phytochemical nature of H. surattensis.
The emission of volatile organic compounds (VOCs) from rotting fruits and wilting flowers.
(2015) Ragubeer, Charlene.; Jürgens, Andreas.; Johnson, Steven Dene.
Plants and the microbes that feed on them produce a high diversity of volatile organic compounds (VOCs) that often mediate interspecies communication with other organisms. Two main functions of VOCs emitted by plants are to attract pollinating animals to flowers and seed dispersers to fruits; while volatiles emitted by microbes that feed on plant material can be used as cues by animals searching for food and can also facilitate dispersal of the microbes. The emission of VOCs from flowers and fruits often shows temporal changes that are characteristic for the different ripening stages of the plant organs. In many plants the VOC emission not only increases but also changes in its chemical composition during flower opening and fruit ripening respectively. In addition, VOC emission into the atmosphere carries information about the physiological status and stresses of the plant. However, the vast majority of studies that deal with the function of VOCs, e.g. for attracting pollinating animals or seed dispersers, focus only on those components that are emitted during the time when the plant shows the highest attractiveness for interaction partners. It is reasonable to believe, however, that the decisions made by animals, in terms of host preference and selection, are not only based on the chemical components that are emitted during times of optimal (nutritional) condition. The decision to utilize a flower/fruit is most likely also based on components that indicate to animals that a food source is not worth using, unpalatable, or toxic. For example, early stage flowers and unripe fruits have a low nutritional value, and late stage (wilted) flowers and rotten fruits may, in addition to already depleted resources, also contain toxic chemicals from microbial decomposition of the plant tissue. Compounds that are emitted from flowers and fruits are often difficult to detect with conventional headspace extraction techniques that use solvents. This is a particular problem for researchers interested in fermentation volatiles because many of the emitted compounds (e.g. ethyl acetate, acetic acid, acetoin) overlap in their retention time with solvents that are commonly used for extracting these compounds such as hexane, acetone, or dichloromethane. In this thesis two commonly used extraction techniques were compared: (i) solid phase micro-extraction (SPME) and (ii) micro solid phase extraction (Micro SPE), both the techniques are used to collect fermentation and floral VOCs. For Micro SPE two different chromatography columns (DB5 and Carbowax) were used to determine which is more sensitive in identifying compounds. For this, a floral and fermentation standard mixture was created by using compounds that represent sweet smelling flowers and rotting/fermenting fruits. Significant differences in the absolute emission of compounds, when using SPME and Micro SPE were found. There were also significant differences with the use of a DB5 and Carbowax column. The selection of the appropriate extraction technique for collection of VOCs should be based upon the type of application and availability of the necessary equipment. From this study, I found that Micro SPE worked better for collecting early to late stage VOCs of flowers and fruits, particularly if samples need to be collected under field conditions. To characterise the typical fermentation volatiles from flowers, the temporal variation in the emission of floral VOCs from the freshly opened to the wilted stages of three plant species namely: Hymenocallis littoralis, Dendrobium chrysotoxum and Camellia reticulata were investigated. The study revealed that there were significant differences in the absolute amounts and in some species also in the number of compounds emitted between early stage flowers and wilted flowers. Hymenocallis littoralis had a higher absolute emission of compounds on day one of flowering and thereafter emission decreased. However, no differences in the number of compounds were detected for this species. The VOCs of H. littoralis on the first day of sampling included: linalool, (1Z)-2-methylbutanal oxime, and 2-methyl-6-methylene-1,7-octadien-3-one, however the composition during the wilted stage included: (3E)-3-hexenyl acetate, heptenal, nonanal, and 2,6-dimethyl-7-octen-2-ol. There was a difference in the absolute emission of compounds for D. chrysotoxum, the emission increased until day six and thereafter decreased. There was also a difference in the number of compounds emitted, with more compounds being emitted from day 1 to 9 of sampling. The VOCs that contributed to the overall scent of the flowers of D. chrysotoxum from day 1 to 11 included: myrcene, linalool, limonene, 3,7-dimethyl-1,3,7-octatriene and α-pinene, however as the flowers began to wilt from day 12 to 13, the VOC composition changed and 4-dimethyl-1-heptene, limonene, terpinen-4-ol and (Z)-verbenol contributed to the late stage scent. For Camellia reticulata significant changes in the absolute emission and the number of compounds during the fresh and wilted flowering stages were detected. It was found that more compounds were emitted during the wilted stage. During the early stage of flowering, ethyl 2-(5-methyl-5-vinyltetrahydrofuran-2-yl) propan-2-yl carbonate, linalool, and 2H-pyran-3-ol, 6-ethenyltetrahydro-2,2,6-trimethyl- contributed to the scent of the flowers. During the wilted stage, benzaldehyde, benzyl alcohol, (E)-2-Hexen-1-ol, and 2-Heptanol contributed to the scent of the flowers. To investigate typical fermentation volatiles three plant species, Musa acuminata (banana), Pyrus communis (pear) and Rothmannia globosa, were selected. For the three selected species, the temporal variation in the emission of VOCs from fruits during the ripening process (i.e. ripe to overripe stages) were investigated. Significant differences in the absolute amount and number of compounds emitted were detected. For M. acuminata, there was a higher absolute emission and number of compounds emitted from sampling day 1 to 10. Acetoin and 2,3-butanediol contributed to the scent of rotting M. acuminata. For P. communis, more absolute emission took place on day 1 of sampling and thereafter decreased, followed by an increase at day 35 of sampling and thereafter decreasing. Hexyl acetate, n-butyl butanoate, 1-hexanol and n-amyl acetate were found during the ripe stage of the fruit, and the VOC composition changed during rotting with the occurrence of ethyl acetate, acetic acid, 3 methyl-1-butanol, phenylethyl alcohol and benzaldehyde. Rothmannia globosa was sampled during the ripe and overripe stages. Higher absolute emission and number of compounds were emitted during the ripe stage of the fruit. 1-hexanol contributed to the scent of R. globosa during the ripe stages, however during the rotting stage, n-butyl acrylate, benzaldehyde, 1-butanol and 2-ethyl-1-hexyl acetate were found in samples. The findings of this study have relevance for researchers that are interested in the role of temporal VOC changes for the behaviour of pollinators and seed dispersers. Furthermore, it may be beneficial to researchers interested in the chemicals that are emitted by flowers that mimic rotting fruit volatiles. It is likely that microbial VOCs together with VOC changes initiated by the plant play an ecological role for host selection in animals. However, there is still a gap in our knowledge regarding the functional role of these VOCs and further studies are needed to investigate how such changes affect animal behavior and host selection. In addition, some of the findings of this study might be of interest for more applied areas such as horticulture and agriculture where the detection of microbial VOC signatures is important for detecting microbial pathogens, early senescence, and decomposition of plant tissue.
A systematic study of the genus rhoicissus planch, (vitaceae) in KwaZulu-Natal.
(2015) Kunene, Sinethemba Faith.; Nicholas, Ashley.; Naidoo, Yougasphree.; Boon, Richard Graham Campbell.
The family Vitaceae, sometimes referred to as the grape family, comprises about 700 to 800 species and 13 to 14 genera, which includes Rhoicissus Planch. Rhoicissus contains 12 species all of which are described as climbing shrubs with tendrils that are without adhesive discs. This study was aimed at updating the taxonomy of the genus Rhoicissus in KwaZulu-Natal such that the names and number of species contained within the genus reflect the current findings. This dissertation looks primarily at the taxonomy of the leaves of the Rhocissus species of KwaZulu-Natal. The reason for this is that this work is meant to help conservationists, environmental managers, rangers, amateur botanists and others who will usually only encounters these species in their vegetative state. It is at this audience that this dissertation is aimed. Rhoicissus tridentata was found to be a complex that is made up of three subspecies: R. tridentata subsp. cuneifolia; R. tridentata subsp. diplonervia and R. tridentata subsp. tridentata. Phenetic results, scatter plots and polygonal graphs did not all support the division of R. digitata into three subspecies. Morphological results, however, did show the slight differences between the subspecies of R. digitata which are R. digitata subsp. digitata; R. digitata subsp. oravivens and R. digitata subsp. emarginata. The other species of Rhoicissus (R. revoilii; R. rhomboidea; R. sessilifolia and R. tomentosa) were all found to be distinct species.
The utility of Trichilia dregeana leaves as a bioindicator of air pollution within selected industrial areas in the eThekwini Municipality, South Africa.
(2016) Appalasamy, Minoli.; Naidoo, Sershen.
Increased anthropogenic activities worldwide have led to dangerously high levels of gaseous emissions. Air pollution levels within industrial areas in South Africa, such as South Durban Basin (SDB), are monitored daily at a few monitoring stations; however, limited coverage of, and data generated by, these stations necessitates alternative strategies such as biomonitoring. In this regard, the use of tree leaves as bioindicators of air pollution can generate valuable data on environmental health and pollutant levels. The present study investigated the utility of Trichilia dregeana Sond. leaves as a bioindicator of air pollution within selected industrial areas in SDB. The first part of the study focussed on effects of SO₂ pollution on leaf morphological (leaf area), physiological (leaf chlorophyll content and leaf fluorescence) and biochemical (intracellular superoxide and hydrogen peroxide production, total aqueous antioxidant activity, and electrolyte leakage) biomarkers of environmental stress. Leaves were sampled over four seasons from (four) trees growing at three industrial (treatment) sites (Prospecton, Ganges and Southern Works) within SDB and from greenhouse-located trees, which served as an ex situ control. Results indicated annual SO₂ concentrations ([SO₂]) were high by global standards and significantly different (p<0.001) across sites, with levels being highest at Southern Works. All biomarkers, except leaf chlorophyll fluorescence, could discriminate between SO₂-exposed and -unexposed leaves. Seasonal data for many of these biomarkers were significantly (p<0.001) correlated with seasonal [SO₂]; however, none of them reflected differences in [SO₂] across treatment sites. The second part of the study, partial least squares regression (PLSR) was used to quantify the relationship between two air pollution biomarkers (chlorophyll content and leaf area) and hyperspectral data. Trichilia dregeana leaves (n=28) were sampled in spring and summer only. Spectral reflectance data were able to distinguish between SO₂-exposed and -unexposed leaves and PLSR was able to relate the hyperspectral dataset to both biomarkers. However, the interaction between biomarkers suggests simultaneous prediction of these, using an algorithm such as PLS-2, may be more suitable. The variable importance in projection method identified wavebands within the red-edge region of the electromagnetic spectrum that showed promise in identifying stress in the leaves of T. dregeana. Collectively, the results provide ample motivation for the establishment of T. dregeana leaves as a bioindicator of air pollution.
The role of floral and fruit scent compounds as mosquito attractants : developing new methods for monitoring mosquito populations.
(2016) Pachuwah, Priyanka.; Jürgens, Andreas.; Johnson, Steven Dene.
Abstract available in PDF file.
Patterns and influencing factors of the larval fish assemblage of the KwaZulu-Natal Bight, South Africa.
(2016) Collocott, Sarah Jade.; Fennessy, Sean Thomas.; Weerts, Steven.
Abstract available in PDF file.
Prevalence of gastro-intestinal parasites of livestock and dogs and risk factors for transmission with emphasis on giardia and cryptosporidium in Magude district, Maputo province, Mozambique.
(2016) Miambo, Regina Daniel.; Mukaratirwa, Samson.; Junior, Alberto Pondja.; Lindh, Johan.
The main objective of this study was to determine the prevalence of gastrointestinal parasites and risk factors for transmission of Giardia and Cryptosporidium in livestock and dogs of Magude District, Maputo, Mozambique. Methods: A total of 696 faecal samples (480 from calves, 60 from goats and 156 from dogs, between 0 and 7 months) were randomly collected from the rectum of animals of both sexes from February to September, 2015. Willis and McMaster methods using NaCl solution were applied in all faecal samples to identify and quantify gastrointestinal helminthic and protozoal infections. To improve the sensitivity of the tests in detection of Giardia and Cryptosporidium, the formol-ether method was applied and the sediment obtained was used for the modified Ziehl Neelsen (mZN) for detection of Cryptosporidium oocysts, direct immunofluorescence (DIF) and indirect immunofluorescence (IIF) tests for both Cryptosporidium oocysts and Giardia cysts. Since the secondary antibody for IIF was derived from goats, this method was not applied in goat samples. To determine the risk factors, a questionnaire was administered to dog owners and livestock farmers. Odds ratios (OR) and 95% confidence interval (CI), Chi Square or Fisher exact test for risk factors and general linear model multivariate for differences between localities of Magude District were applied using SPSS programme and p < 0.05 was considered to be statistically significant. The sensitivity and specificity of mZN and IIF were determined using MedCalc software with DIF test as gold standard. Using Willis, IIF and DIF, the prevalence of Giardia in calves was 0%, 8.1%, and 6.0%, in dogs 0.6%, 8.3% and 5.7% and for goats it was 0% and 13.3% respectively and the IIF was not done. The prevalence of Cryptosporidium in calves using Willis, mZN, IIF and DIF was 0%, 3.8%, 4.7% and 0.4% in dogs it was 0%, 0.6%, 6.4% and 0.6% respectively and in goats was 0% for all tests. All positive samples to DIF, IIF and mZN were negative by PCR. Additionally, the parasites and prevalence detected in dogs were Sarcocystis spp. (3.8%), Isospora spp. (2.6%), Ancylostoma spp. (60.3%), Toxocara canis (5.8%), Taeniidae (1.9%), Trichuris vulpis (1.3%), Spirocerca lupi (0.6%); in calves and goats, Strongylid (50.8%, 31.6%), Eimeria spp. (17.5%, 41.6%) and Moniezia spp. (3.3% and 11.6%) respectively. The mZN test showed high sensitivity (100%) and specificity (96.2% and 100%) in detecting Cryptosporidium oocysts. The sensitivity and specificity of IIF test to detect both parasites was also high. The sensitivity ranged between 88.9% and 100%, specificity between 95.4% and 98.5% for Giardia and 100% of sensitivity, 93.2% and 93.9% of specificity for Cryptosporidium. In contrast, the Willis lacked sensitivity for Giardia and Cryptosporidium infections (0%). The lack of regular treatment against parasitic infections in calves and the source of water (mostly the river) were identified as a risk factor in the transmission of Giardia and Cryptosporidium in calves and dogs (p < 0.05). Giardia and Cryptosporidium are prevalent in Magude District, although the risk of zoonotic transmission through molecular technique was not done due to low numbers of oocysts/cysts in the positive samples. The main helminthic parasites detected through floatation technique for dogs were Toxocara canis and Ancylostoma spp., for cattle and goats were strongylids and Eimeria spp. and the intensity of infection was low.
The use of open top chambers to assess the effects of elevated temperatures on subtropical grassland vegetation in situ : a case study on KwaZulu-Natal sandstone sourveld.
(2016) Buhrmann, Rowan David.; Naidoo, Sershen.; Ramdhani, Syd.; Pammenter, Norman William.
Abstract available in PDF file.
Production of hydroxyl radicals by lichens via extracellular hydroquinone-driven redox cycling.
(2016) Moyo, Calvin Eddington.; Beckett, Richard Peter.
Abstract available in PDF file.
Using environmental niche models to identify Malagasy bat biodiversity hotpots and conversation priorities in the face of climate and human land use changes.
(2016) Kok, Ryan Bradley.; Schoeman, Marthinus Cornelius.; Goodman, Steven Michael.
Madagascar represents a global hotspot of endemism, but it faces numerous threats to its biodiversity, including impacts of climate and human land use changes. In this study, suitable habitat space of 25 Malagasy bat species was modelled under past, current and future climate projections, asking three questions: (i) Do Malagasy bat richness hotspots change over different climatic projections and human land use in the past to present to future?; (ii) Do current and future hotspots fall within Madagascar’s current protected areas (PAs)?; and (iii) Can areas be included in the current protected areas to better protect the Malagasy bat hotspots? A decline in suitable habitat space for bat species was anticipated, and, hence, decreased hotspots under warmer (Last Inter-glacial (LIG) and future) climate scenarios, particularly in combination with human land use. It was also expected that changes in climate would influence bats similarly within functional groups (FGs) and differently across functional groups. Specifically, it was predicted that bats adapted to forage in vegetation (clutter FG) should be more affected than bats adapted to hunt insects near vegetation (clutter-edge FG) and high above vegetation (open-air FG). It was further predicted bat richness hotspots would have poor coverage by Madagascar’s PA network for current and future scenarios, due to broad distribution ranges of bats and limited area coverage of PAs across the island. Suitable habitat space was modelled for bat species using environmental niche models (ENMs), taking an ensemble modelling approach to identify the most suitable ENM for each species. Species richness was quantified by stacking suitable habitat maps of individual bat species. The results showed that richness hotspots shifted in size and geographic position under different climate change scenarios. Generally, changes from warm to cold climates decreased the potential suitable habitat space of clutter bats yet increased those of clutter-edge and open-air bat species. In contrast, changes from cold to warmer climates decreased the suitable habitats of clutter bats more than those of clutter-edge and open-air bats. Null model analyses showed that under both cold and warm climatic conditions, the observed overlap in suitable habitat between clutter and clutter-edge functional groups was lower than expected, whereas overlap in suitable habitat between clutter-edge and open-air functional groups was higher than expected by chance. Further, suitable habitat space of bat species was only partially covered by the PA system for climate change and human land use scenarios (range 2 – 20%). Although most of the bat richness hotspots are in PAs, this coverage will decrease with predicted future climate change. It is suggested that an additional 58,077 km should be added to the current protected areas to ensure adequate protection under future climate and land use.
The genetic connectivity of diplodus capensis (blacktail) and neoscorpis lithophilus (stonebream) fish populations in the Southwest Indian Ocean.
(2016) Cele, Lindile Venencia.; Macdonald, Angus Hector Harold.; Gouws, Gavin.; Fennessy, Sean Thomas.
Abstract available in PDF file.

Browse

Browsing Masters Degrees (Biological Sciences) by Issue Date