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Systematics and biogeography of Mesobola brevianalis (Boulenger, 1908) (Teleostei: Cyprinidae)

  • Authors: Riddin, Megan Amy
  • Date: 2015
  • Subjects: River sardine , Molecular evolution
  • Language: English
  • Type: Thesis , Masters , MSc
  • Identifier: vital:5930 , http://hdl.handle.net/10962/d1017808
  • Description: The accurate identification of fish species, their life stages and their products enables the correct management of fisheries, research and conservation of distinctive populations for long-term survival and sustainability. Mesobola brevianalis Boulenger, 1908, commonly known as the river sardine, is found in many river systems in southern Africa. Because it exhibits widely separated populations showing subtle differences, particularly in colour, it is thought that there may be cryptic species involved. Standard phylogenetic techniques using three genetic markers (mitochondrial COI, nuclear protein RAG1 and nuclear ribosomal 28S rRNA), enabled the building of phylogenetic networks for M. brevianalis and some outgroup species. Consistent patterns of relationship were seen with 28S supporting monophyly. COI and RAG1 suggested that populations that are currently identified as M. brevianalis in fact represent several species. There was sufficiently strong support for the evolutionary independence of the M. brevianalis populations from the Rovuma, Kunene and Orange River Systems to consider them as independent species. The independence of the genus Mesobola was brought into question because Engraulicypris sardella and Rastrineobola argentea were placed within it phylogenetically.Morphometric methods in the form of multivariate truss network analyses, were performed to locate morphological markers for populations. There was little to no variation among most of the populations synonymized under M. brevianalis. Furthermore, neither latitude nor longitude had an effect on the morphological characters that might be linked to functional evolution. A molecular clock analysis of COI data was used to calibrate a paleobiogeographical model which entailed a divergence of lineages starting from an easterly reigning Paleo-Congo Basin, via a hypothetical Paleo-Kalahari Lake that was fragmented by a series of uplifts and drying events beginning ~65 million years ago. Complete evidence supported the synonymisation of the genera Engraulicypris and Mesobola, the resurrection of the species name gariepinus for the Orange River Systempopulation, and the description of two new species: E. ngalala from the Rovuma River System and E. howesi from the Kunene River System.
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  • Date Issued: 2015

The role of cellulases and glucohydrolases in the solubilisation of primary sewage sludge

  • Authors: Ngesi, Nosisa
  • Date: 2002 , 2013-05-09
  • Subjects: Sewage sludge , Sewage sludge digestion , Cellulase , Glucosidase inhibitors , Hydrolases , Sulfates
  • Language: English
  • Type: Thesis , Masters , MSc
  • Identifier: vital:4080 , http://hdl.handle.net/10962/d1007454 , Sewage sludge , Sewage sludge digestion , Cellulase , Glucosidase inhibitors , Hydrolases , Sulfates
  • Description: Biological sulph ate reduction has been identi fied as a potentially valuable process for removing sulphate and heavy metals from indllstrial effluents. The role of sulphate reducing bacteria (SRB) in this process has attracted the attention of biotechnologists and recently of enzymologists due to its fundamental properties and possible role in AMD bioremediation. These obligatory anaerobic sulphate-reducing bacteria are commonly known to dissimilate sulphate for energy. Under anaerobic conditions SRB oxidize simple organic compounds such as lactic acid with the sulphate and thereby generate hydrogen sulphide (a stTong reducing agent) and bicarbonate ions. The hydrogen sulphide in turn reacts with contaminant metals contained in AMD and precipitates them out of solution as metal sulphides. Bicarbonate ions neutralize AMD by reaction with protons to form carbon dioxide and water. Organic matter in the municipal sewage sludge has been identified as a potential source of electron donors for su lphate reduction. However, this organic matter is in the polymeric form that cannot be util ised by SRB. The latter depend on the activities of other hydrolytic bacteria for the degradation of complex polymers. Hence the availability of these monomeric substrates is a major factor, which may constrain further process development and is considered a rate-limiting step. Thi s study is therefore undertaken to investigate the bacterial glucohydrolase enzymes involved in the digestion of the polysaccharides present in the sewage sludge with specific interest in cellulases and/or p-glucosidase enzymes. The goals of the research are to: isolate, identify, purify and quantify these enzymes; study their distribution with respect to time, pH, and temperature; maximize and quantify the hydrol ys is products; study whether sulphide and sulphate have an enhancing or an inhibitory effect on the activity of enzymes; optimize the enzyme activity against substrate and/or product inhibition and soluble heavy metal salts. , KMBT_363 , Adobe Acrobat 9.54 Paper Capture Plug-in
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  • Date Issued: 2002

Aspects of the biology and ecology of some intertidal Holothurians (Echinodermata) along the Eastern Cape coast of South Africa

  • Authors: Foster, Gregory George
  • Date: 1994
  • Subjects: Echinodermata , Echinodermata -- South Africa
  • Language: English
  • Type: Thesis , Masters , MSc
  • Identifier: vital:5638 , http://hdl.handle.net/10962/d1005320 , Echinodermata , Echinodermata -- South Africa
  • Description: Four species of dendrochirote holothurians, Roweia stephensoni John, Pseudocnella sykion Lampert, Aslia spyridophora Clark, Roweia frauenfeldi frauenfeldi Ludwig, and one aspidochirote holothurian, Neostichopus grammatus Clark, are common inhabitants of the intertidal regions of the eastern Cape rocky shores of South Africa. All five species are sympatric for most of their geographical distribution. The intertidal distributions, densities and biomasses of R. stephensoni, P. sykion and N. grammatus were examined at six sites from Port Elizabeth to East London in the eastern Cape. At all sites the three species showed similar overlapping zonations with R. stephensoni and P. sykion reaching their highest maximum mean densities and biomasses (drained wet weight) in the lower mid-shore region (401m² and 684g/m², 181m² and 269g/m², respectively at Port Elizabeth), whilst N. grammatus in the low-shore region (61m² and 72g/m², at Port Elizabeth). The highest densities and biomasses of all three species were recorded on boulder shores that had minimal sand inundation. Seasonality of reproduction of R. stephensoni, P. sykion and N. grammatus was compared at Port Elizabeth, using gonad index values, gonadal tubule diameters, egg diameters and spermatozoon content in tubules from January 1992 until August 1993. All three species are dioecious and did not deviate from a 1: 1 sex ratio. Sizes at first sexual maturity were 2.5-2.9 cm³ for R. stephensoni and P. sykion, and 3.0-3.9cm³ for N. grammatus. The gonads of R. stephensoni and P. sykion consist of a bunch of unbranched tubules of equal diameter, with males having more tubules of a smaller diameter than females. By contrast, the gonad of N. grammatus consists of two tufts of multiple branched tubules. All three species followed annual reproductive cycles, and in R. stephensoni and P. sykion gametogenesis occurred from March 1992 until August/September 1992, and maturity was maintained until the main spawning event in January 1993. By contrast, in N. grammatus gametogenesis occurred from July 1992 until September 1992, and maturity was maintained until the main spawning event in December 1992/January 1993. Unlike R. stephensoni and P. sykion the reproductive cycle of N. grammatus was more pronounced, in that the gonad regressed after spawning. Aspects of the feeding biology of R. stephensoni, P. sykion, A. spyridophora, R.ffrauenfeldi and N. grammatus were compared, using the gross buccal tentacle morphology, type and size range of ingested food particles, and gut lengths. Scanning electron microscopy revealed that the buccal tentacles of R. stephensoni, P. sykion and A. spyridophora could be classified as dendritic, branching numerous times with the tips terminating in numerous nodes covered with discs of papillate projections. The buccal tentacle structure of R. f frauenfeldi deviated from the typical dendrochirote dendritic form. The tentacles are stout with few branches which terminate in large bulbous nodes lacking discs of papillate projections. Neostichopus grammatus possesses buccal tentacles that could be classified as peltate, terminating in large nodes which also lacked discs of papillate projections. Roweia stephensoni, P. sykion and A. spyridophora are suspension-feeders, ingesting food particles mostly <53μm in size. Roweia f frauenfeldi was classed as a "heavy" suspension-feeder, ingesting food particles mostly between 250μm-1.18μm, while N. grammatus is a deposit-feeder, ingesting benthic sediments mostly between 106-500μm. The gut lengths of the dendrochirote holothurians were found to be significantly longer than that of the aspidochirote, and may be attributed to the nature of the food ingested.
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  • Date Issued: 1994

A geohydrological evaluation of the coastal area between Bushmans River Mouth and Cape Mouth and Cape Padrone, Eastern Cape, South Africa

The in vivo and quantitative assessment of topical corticosteroid formulations

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