An investigation of female leaders' perceptions of themselves and their roles as leaders in a Catholic School
- Authors: Kauaria, Vejanda
- Date: 2003
- Subjects: Catholic schools -- Namibia -- Administration Women school administrators -- Namibia School management and organization -- Namibia Educational leadership -- Namibia Women in public life -- Namibia Sex discrimination against women -- Namibia
- Language: English
- Type: Thesis , Masters , MEd
- Identifier: vital:1626 , http://hdl.handle.net/10962/d1003508
- Description: The question of gender in leadership continues to be a contentious and poorly understood phenomenon. There seems general agreement that women do lead differently from men, and this study begins from that premise, focusing on a case in which leadership has traditionally been the domain of females. The case was chosen for its uniqueness, the assumption being that in these circumstances leadership may have developed particular characteristics. Following a qualitative approach (drawing on phenomenology), the study seeks to investigate how women leaders experience their roles as leaders. In-depth interviews made it possible for me to capture the perceptions and experiences of the three women leaders I interviewed. The study reveals that women are more inclined to use interactive styles of leadership. Women use leadership that is more participative, negotiative, cooperative, shared and collaborative. These characteristics are in line with the features of transformational leadership which differs from the more traditional transactional leadership that is more controlled and directive. The study has also shown that leadership develops from within the person of the leader as the leader is the one who spearheads the organization through vision, ideas, beliefs andassumptions. The findings of this study suggest thus that unless women are given chances to prove how they can lead, this new approach of leadership within them and that is required by modern organizations would be lost and leadership would remain relatively unchanged and undesirable. In the context of Namibia, this study should be of potential significance because of the rapid change that is taking place in the inclusion of women in leadership and management positions in education.
- Full Text:
- Date Issued: 2003
- Authors: Kauaria, Vejanda
- Date: 2003
- Subjects: Catholic schools -- Namibia -- Administration Women school administrators -- Namibia School management and organization -- Namibia Educational leadership -- Namibia Women in public life -- Namibia Sex discrimination against women -- Namibia
- Language: English
- Type: Thesis , Masters , MEd
- Identifier: vital:1626 , http://hdl.handle.net/10962/d1003508
- Description: The question of gender in leadership continues to be a contentious and poorly understood phenomenon. There seems general agreement that women do lead differently from men, and this study begins from that premise, focusing on a case in which leadership has traditionally been the domain of females. The case was chosen for its uniqueness, the assumption being that in these circumstances leadership may have developed particular characteristics. Following a qualitative approach (drawing on phenomenology), the study seeks to investigate how women leaders experience their roles as leaders. In-depth interviews made it possible for me to capture the perceptions and experiences of the three women leaders I interviewed. The study reveals that women are more inclined to use interactive styles of leadership. Women use leadership that is more participative, negotiative, cooperative, shared and collaborative. These characteristics are in line with the features of transformational leadership which differs from the more traditional transactional leadership that is more controlled and directive. The study has also shown that leadership develops from within the person of the leader as the leader is the one who spearheads the organization through vision, ideas, beliefs andassumptions. The findings of this study suggest thus that unless women are given chances to prove how they can lead, this new approach of leadership within them and that is required by modern organizations would be lost and leadership would remain relatively unchanged and undesirable. In the context of Namibia, this study should be of potential significance because of the rapid change that is taking place in the inclusion of women in leadership and management positions in education.
- Full Text:
- Date Issued: 2003
An investigation of knowledge management implementation strategies
- Authors: Sunassee, Nakkiran N
- Date: 2003
- Subjects: Knowledge management , Strategic planning , Automobile industry and trade -- South Africa -- Management
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:1141 , http://hdl.handle.net/10962/d1002770 , Knowledge management , Strategic planning , Automobile industry and trade -- South Africa -- Management
- Description: The world is experiencing an era which has been termed the “knowledge age” or the “knowledge economy”. In this new context, knowledge is the primary commodity, and knowledge flows are regarded as the most important factors in the economy. The management of knowledge flows within organisations has become a crucial activity because many of the activities of organisations and the broader economic and social life today are knowledge-driven. In recent years, this managerial activity has become known as Knowledge Management. Equally important are the associated Knowledge Management implementation strategies. Driven by a need expressed by the South African Motor Vehicle Industry for a knowledge management implementation strategy tailored to their needs, this research aimed to develop a knowledge management implementation strategy suited to the needs of this industry. Following an extensive literature survey and a study of the target industry using Duffy’s Knowledge Benchmarking Questionnaire, a model of knowledge management implementation is proposed that is suited to the needs of the South African Motor Vehicle Industry. The model consists of three main interlinked components: Knowledge Management of the Organisation, People, and Infrastructure and Processes. Furthermore, the model recommends a holistic approach to managing knowledge. The critical success factors of the model were tested by means of a survey of industry opinions that validated certain aspects of the model and motivated for changes in others. Additionally, despite the focus of the model on the target industry, it is considered sufficiently appropriate for use by other organisations.
- Full Text:
- Date Issued: 2003
- Authors: Sunassee, Nakkiran N
- Date: 2003
- Subjects: Knowledge management , Strategic planning , Automobile industry and trade -- South Africa -- Management
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:1141 , http://hdl.handle.net/10962/d1002770 , Knowledge management , Strategic planning , Automobile industry and trade -- South Africa -- Management
- Description: The world is experiencing an era which has been termed the “knowledge age” or the “knowledge economy”. In this new context, knowledge is the primary commodity, and knowledge flows are regarded as the most important factors in the economy. The management of knowledge flows within organisations has become a crucial activity because many of the activities of organisations and the broader economic and social life today are knowledge-driven. In recent years, this managerial activity has become known as Knowledge Management. Equally important are the associated Knowledge Management implementation strategies. Driven by a need expressed by the South African Motor Vehicle Industry for a knowledge management implementation strategy tailored to their needs, this research aimed to develop a knowledge management implementation strategy suited to the needs of this industry. Following an extensive literature survey and a study of the target industry using Duffy’s Knowledge Benchmarking Questionnaire, a model of knowledge management implementation is proposed that is suited to the needs of the South African Motor Vehicle Industry. The model consists of three main interlinked components: Knowledge Management of the Organisation, People, and Infrastructure and Processes. Furthermore, the model recommends a holistic approach to managing knowledge. The critical success factors of the model were tested by means of a survey of industry opinions that validated certain aspects of the model and motivated for changes in others. Additionally, despite the focus of the model on the target industry, it is considered sufficiently appropriate for use by other organisations.
- Full Text:
- Date Issued: 2003
An investigation of knowledge management practices in the Old Mutual, Buffalo City Metropole branch
- Authors: Siqoko, Kolisa
- Date: 2003
- Subjects: Knowledge management , Insurance companies -- South Africa -- East London
- Language: English
- Type: Thesis , Masters , MBA
- Identifier: vital:10879 , http://hdl.handle.net/10948/252 , Knowledge management , Insurance companies -- South Africa -- East London
- Description: The study has sought to examine knowledge management practice in the Old Mutual, Buffalo City Metropole. The study has been conducted against the backdrop of measuring how far South African companies are in applying Knowledge Management (KM) tools and techniques to improve their competitive advantage. The study was conducted based on the assumption that insurance companies in South Africa are at the forefront in the use and application of technology. Various concepts are defined throughout the study. In reviewing literature for example, the study introduces the reader to various theories, views and approaches to KM. The most significant of these are the cultural and social systems approach on one hand and the product or process approach on the other. The study relied on the use of a variety of data collection methods such as questionnaires, interviews and participant observation for the purposes of collecting primary data. From the primary data collected, it was discovered that the largest number of responses came from marketing, sales and customer services departments. The employees have limited flexibility in terms of decision making and team work, due to the rigidity of tasks. The findings revealed that the company has a loosely structured infrastructure, where each strategic business unit (SBU) manages its own IT tools and documents. All these underlying aspects are not conducive to the promotion of and growth of KM in any company. The final chapter concludes with a model for KM implementation and the procedures to be followed to ensure that the practice adds value to the company.
- Full Text:
- Date Issued: 2003
- Authors: Siqoko, Kolisa
- Date: 2003
- Subjects: Knowledge management , Insurance companies -- South Africa -- East London
- Language: English
- Type: Thesis , Masters , MBA
- Identifier: vital:10879 , http://hdl.handle.net/10948/252 , Knowledge management , Insurance companies -- South Africa -- East London
- Description: The study has sought to examine knowledge management practice in the Old Mutual, Buffalo City Metropole. The study has been conducted against the backdrop of measuring how far South African companies are in applying Knowledge Management (KM) tools and techniques to improve their competitive advantage. The study was conducted based on the assumption that insurance companies in South Africa are at the forefront in the use and application of technology. Various concepts are defined throughout the study. In reviewing literature for example, the study introduces the reader to various theories, views and approaches to KM. The most significant of these are the cultural and social systems approach on one hand and the product or process approach on the other. The study relied on the use of a variety of data collection methods such as questionnaires, interviews and participant observation for the purposes of collecting primary data. From the primary data collected, it was discovered that the largest number of responses came from marketing, sales and customer services departments. The employees have limited flexibility in terms of decision making and team work, due to the rigidity of tasks. The findings revealed that the company has a loosely structured infrastructure, where each strategic business unit (SBU) manages its own IT tools and documents. All these underlying aspects are not conducive to the promotion of and growth of KM in any company. The final chapter concludes with a model for KM implementation and the procedures to be followed to ensure that the practice adds value to the company.
- Full Text:
- Date Issued: 2003
An investigation of the isolation, characterisation and application of hydantoinases for the industrial production of amino acids
- Authors: Kirchmann, Shaun
- Date: 2003
- Subjects: Hydantoin Amino acids Hydrolysis
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:3969 , http://hdl.handle.net/10962/d1004028
- Description: This thesis describes a series of investigations into the hydantoin-hydrolysing activity of bacterial strains RU-KM1 and RU-OR, which were previously isolated for their ability to hydrolyse hydantoins to amino acids. The main aim of the study was to develop biotransformations with potential application in the production of enantiomerically pure amino acids using a bioreactor based system utilising the hydantoin hydrolysing enzymes of the two isolated microorganisms. Different substituted hydantoins may be used as substrates by these enzymes for the production of a variety of amino acids. These are not only important for amino acid production, but they may be used for production of other industrially important compounds, such as semisynthetic penicillin/ampicillin, L-aspartame (sweetener), Fluvalinate (insecticide), Enalapril (ACE inhibitor). Thus, the ability of the above-mentioned strains to hydrolyse these substrates was investigated, with the view to utilizing the maximum potential of these biocatalysts. Hydantoin conversion involves a two-step hydrolysis reaction which yields, initially, an N-carbamylamino acid intermediate, and subsequently, an amino acid. The hydantoin-hydrolysing enzymes of a Pseudomonas sp. RU-KM1, and an Agrobacterium sp. RU-OR were characterised as whole cells and in a crude extract preparation, and reaction conditions for its biocatalytic application were optimised. The optimum conditions for conversion of hydantoin to glycine were found to be 1 hour at 40 °C, with conversion yields greater than 30 % achieved. The enzymes of RU-KM1 demonstrated considerable stability, retaining 80 % of their activity after storage for 2 weeks at 4 °C. The activities of the enzymes were increased by the addition of a detergent to the extraction medium, suggesting that the enzymes might be membrane-bound. The results of the determination of the metal-dependence of the hydantoinase and N-carbamoylase of RU-KM1 suggested that these enzymes required metal ions for activity, with metal ions such as Cu[superscript (2+)], Fe[superscript (2+)], and Co[superscript (2+)] resulting in no significant change in enzyme activity, however there was an activation of the enzymes when Mn[superscript (2+)] was added to the enzymes. The stereoselectivity of the enzymes was investigated, and the results suggested that the hydantoinase was D-selective, whereas the N-carbamoylase was shown to be L-selective by other researchers. The hydantoin substrate selectivity of RU-KM1 and RU-OR was investigated, and the organisms were shown to be able to hydrolyse all of the seven substrates tested. However, there was a difference in activity levels between crude extract preparations and whole cells, with crude extracts generally showing slightly lower activity than whole cells in RU-KM1, and the whole cells or RU-OR showing the lower activity than its crude extract. Some difference was also observed in the order of preference of substrates between whole cells and crude extracts. The preferred substrate for RU-KM1 whole cells was isopropylhydantoin, whereas the crude extract preparation preferentially hydrolysed p-hydroxyphenylhydantoin, achieving 57 % and 52 % conversions respectively. RU-OR whole cells preferred methylhydantoin where as the crude extract preferred isopropylhydantoin, and showed 49 % and 51 % conversions respectively. The enzymes were characterised in terms of their temperature and pH optima, inducer requirements, and product inhibition studies. The hydantoinase of RU-KM1 was shown to be inducible with low levels of hydantoin, and thermostable upto 75 °C with its optima between 60 and 70 °C. The N-carbamoylase was shown to have its optima at 50 °C. The addition of ATP (0.5 mM), DTT (1 mM) and a protease inhibitor (2 mg.mL[superscript (-1)]) all increased the hydantoinase activity of RU-KM1 crude extract, however they had very little effect on the N-carbamoylase activity. The hydantoinase enzyme from extracts of RU-KM1 was partially purified by development of cell disruption methods using mechanical and lysing enzymes, followed by precipitation and chromatographic resolution. The results obtained showed a hydantoinase enzyme of between 48 and 66 kDa. RU-KM1 was grown under fermentation conditions using different minimal media. The activity and yields under these conditions were low. Previous attempt to grow the organism in a rich medium had resulted in an increase in biomass but no hydantoinase activity. A rich medium was developed by carbon and nitrogen optimisation and yielded biomass up to 30 g.L[superscript (-1)] dry cell weight. The hydantoinase activity was restored by nitrogen starvation in stationary phase. This resulted in high biomass with increased activity. This data is currently in press. Crude extract and whole cells were immobilised on flat sheet membranes, hollow fibre membranes and in alginate beads. Low hydantoinase activity was measured in bioreactors using membranes in different configurations. A significant increase in hydantoinase activity was measured when the crude extract was immobilised in sodium alginate, as a result of stabilisation of the N-carbamoylase. Temperature and pH optima were unaffected by the immobilisation procedure, however the durability of the enzymes increased 2-fold. Different configurations of the bioreactor were investigated, as well as a hydroxyphenylhydantoin as an alternative substrate in this study. The bioreactors showed a near 95 % conversion of the hydantoin to glycine, and a 99 % conversion using HPG. In conclusion, the hydantoin-hydrolysing enzymes of RU-KM1 have been shown to be possibly membrane associated, which is a novel finding. This study has shown that the hydantoinase of RU-KM1 is D-stereoselective, with high temperature stability. A growth medium was developed for the rapid production of active biomass. A bioreactor was developed using a single and a dual biocatalyst configuration, which was capable of hydrolysing hydantoin and monosubstituted hydantoins to produce amino acids. To our knowledge this system is the first such dual biocatalyst system reported for the production of amino acids.
- Full Text:
- Date Issued: 2003
- Authors: Kirchmann, Shaun
- Date: 2003
- Subjects: Hydantoin Amino acids Hydrolysis
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:3969 , http://hdl.handle.net/10962/d1004028
- Description: This thesis describes a series of investigations into the hydantoin-hydrolysing activity of bacterial strains RU-KM1 and RU-OR, which were previously isolated for their ability to hydrolyse hydantoins to amino acids. The main aim of the study was to develop biotransformations with potential application in the production of enantiomerically pure amino acids using a bioreactor based system utilising the hydantoin hydrolysing enzymes of the two isolated microorganisms. Different substituted hydantoins may be used as substrates by these enzymes for the production of a variety of amino acids. These are not only important for amino acid production, but they may be used for production of other industrially important compounds, such as semisynthetic penicillin/ampicillin, L-aspartame (sweetener), Fluvalinate (insecticide), Enalapril (ACE inhibitor). Thus, the ability of the above-mentioned strains to hydrolyse these substrates was investigated, with the view to utilizing the maximum potential of these biocatalysts. Hydantoin conversion involves a two-step hydrolysis reaction which yields, initially, an N-carbamylamino acid intermediate, and subsequently, an amino acid. The hydantoin-hydrolysing enzymes of a Pseudomonas sp. RU-KM1, and an Agrobacterium sp. RU-OR were characterised as whole cells and in a crude extract preparation, and reaction conditions for its biocatalytic application were optimised. The optimum conditions for conversion of hydantoin to glycine were found to be 1 hour at 40 °C, with conversion yields greater than 30 % achieved. The enzymes of RU-KM1 demonstrated considerable stability, retaining 80 % of their activity after storage for 2 weeks at 4 °C. The activities of the enzymes were increased by the addition of a detergent to the extraction medium, suggesting that the enzymes might be membrane-bound. The results of the determination of the metal-dependence of the hydantoinase and N-carbamoylase of RU-KM1 suggested that these enzymes required metal ions for activity, with metal ions such as Cu[superscript (2+)], Fe[superscript (2+)], and Co[superscript (2+)] resulting in no significant change in enzyme activity, however there was an activation of the enzymes when Mn[superscript (2+)] was added to the enzymes. The stereoselectivity of the enzymes was investigated, and the results suggested that the hydantoinase was D-selective, whereas the N-carbamoylase was shown to be L-selective by other researchers. The hydantoin substrate selectivity of RU-KM1 and RU-OR was investigated, and the organisms were shown to be able to hydrolyse all of the seven substrates tested. However, there was a difference in activity levels between crude extract preparations and whole cells, with crude extracts generally showing slightly lower activity than whole cells in RU-KM1, and the whole cells or RU-OR showing the lower activity than its crude extract. Some difference was also observed in the order of preference of substrates between whole cells and crude extracts. The preferred substrate for RU-KM1 whole cells was isopropylhydantoin, whereas the crude extract preparation preferentially hydrolysed p-hydroxyphenylhydantoin, achieving 57 % and 52 % conversions respectively. RU-OR whole cells preferred methylhydantoin where as the crude extract preferred isopropylhydantoin, and showed 49 % and 51 % conversions respectively. The enzymes were characterised in terms of their temperature and pH optima, inducer requirements, and product inhibition studies. The hydantoinase of RU-KM1 was shown to be inducible with low levels of hydantoin, and thermostable upto 75 °C with its optima between 60 and 70 °C. The N-carbamoylase was shown to have its optima at 50 °C. The addition of ATP (0.5 mM), DTT (1 mM) and a protease inhibitor (2 mg.mL[superscript (-1)]) all increased the hydantoinase activity of RU-KM1 crude extract, however they had very little effect on the N-carbamoylase activity. The hydantoinase enzyme from extracts of RU-KM1 was partially purified by development of cell disruption methods using mechanical and lysing enzymes, followed by precipitation and chromatographic resolution. The results obtained showed a hydantoinase enzyme of between 48 and 66 kDa. RU-KM1 was grown under fermentation conditions using different minimal media. The activity and yields under these conditions were low. Previous attempt to grow the organism in a rich medium had resulted in an increase in biomass but no hydantoinase activity. A rich medium was developed by carbon and nitrogen optimisation and yielded biomass up to 30 g.L[superscript (-1)] dry cell weight. The hydantoinase activity was restored by nitrogen starvation in stationary phase. This resulted in high biomass with increased activity. This data is currently in press. Crude extract and whole cells were immobilised on flat sheet membranes, hollow fibre membranes and in alginate beads. Low hydantoinase activity was measured in bioreactors using membranes in different configurations. A significant increase in hydantoinase activity was measured when the crude extract was immobilised in sodium alginate, as a result of stabilisation of the N-carbamoylase. Temperature and pH optima were unaffected by the immobilisation procedure, however the durability of the enzymes increased 2-fold. Different configurations of the bioreactor were investigated, as well as a hydroxyphenylhydantoin as an alternative substrate in this study. The bioreactors showed a near 95 % conversion of the hydantoin to glycine, and a 99 % conversion using HPG. In conclusion, the hydantoin-hydrolysing enzymes of RU-KM1 have been shown to be possibly membrane associated, which is a novel finding. This study has shown that the hydantoinase of RU-KM1 is D-stereoselective, with high temperature stability. A growth medium was developed for the rapid production of active biomass. A bioreactor was developed using a single and a dual biocatalyst configuration, which was capable of hydrolysing hydantoin and monosubstituted hydantoins to produce amino acids. To our knowledge this system is the first such dual biocatalyst system reported for the production of amino acids.
- Full Text:
- Date Issued: 2003
An investigation of the relative importance of the media in influencing the voting behaviour of Evelyn Hone College students in Lusaka during the December, 2001 presidential elections in Zambia
- Authors: Jere, Caesar
- Date: 2003
- Subjects: Voting -- Zambia Mass media -- Political aspects -- Zambia Presidents -- Zambia -- Election -- 2001
- Language: English
- Type: Thesis , Masters , MA
- Identifier: vital:3516 , http://hdl.handle.net/10962/d1007803
- Description: This study explores the relative importance of the media in influencing the electoral choices of a small group of Zambians, namely Evelyn Hone College students in Lusaka who participated in the December 2001 elections in Zambia. The study investigates the interplay of mediation between the lived cultural experiences of the sample of students and the impact of media messages. Students at Evelyn Hone College come from different ethnic groupings, social classes, religions and regions. They are exposed to both the state and the privately owned media, which represent a range of political viewpoints. The outcome of the December 2001 elections in Zambia gave the impression that people in urban areas in Zambia were less likely to vote on ethnic lines because they had easy access to different media, ranging from print to electronic, which provided them with diverse information about the political scene, and probably shaped their electoral choices. Conversely, their counterparts in the rural areas appeared to vote along ethnic lines, seemingly because of lack of exposure to the media. It was also assumed that most people in rural areas were not as modernized as their urban counterparts who were more exposed to enlightened sources of information such as professional groups and other elite social institutions which helped them to shape their political opinions than most rural people. The study attempts to establish to what extent the media impacted on the selected sample of urban students in the choice of their presidential candidates in the December 2001 elections in Zambia. The study further investigates to what extent other factors such as ethnic inclinations and other social predispositions influenced them in their choice of the candidates. The interviewees for this study were randomly drawn from a population of Evelyn Hone College students that voted in the December 2001 presidential elections in Zambia. The sample consisted of 30 randomly selected students who were purposely stratified in three focus groups of ten each. Each stratum represented the approximate ethnic equivalence of one of the presidential candidates who contested the December 2001 elections.
- Full Text:
- Date Issued: 2003
- Authors: Jere, Caesar
- Date: 2003
- Subjects: Voting -- Zambia Mass media -- Political aspects -- Zambia Presidents -- Zambia -- Election -- 2001
- Language: English
- Type: Thesis , Masters , MA
- Identifier: vital:3516 , http://hdl.handle.net/10962/d1007803
- Description: This study explores the relative importance of the media in influencing the electoral choices of a small group of Zambians, namely Evelyn Hone College students in Lusaka who participated in the December 2001 elections in Zambia. The study investigates the interplay of mediation between the lived cultural experiences of the sample of students and the impact of media messages. Students at Evelyn Hone College come from different ethnic groupings, social classes, religions and regions. They are exposed to both the state and the privately owned media, which represent a range of political viewpoints. The outcome of the December 2001 elections in Zambia gave the impression that people in urban areas in Zambia were less likely to vote on ethnic lines because they had easy access to different media, ranging from print to electronic, which provided them with diverse information about the political scene, and probably shaped their electoral choices. Conversely, their counterparts in the rural areas appeared to vote along ethnic lines, seemingly because of lack of exposure to the media. It was also assumed that most people in rural areas were not as modernized as their urban counterparts who were more exposed to enlightened sources of information such as professional groups and other elite social institutions which helped them to shape their political opinions than most rural people. The study attempts to establish to what extent the media impacted on the selected sample of urban students in the choice of their presidential candidates in the December 2001 elections in Zambia. The study further investigates to what extent other factors such as ethnic inclinations and other social predispositions influenced them in their choice of the candidates. The interviewees for this study were randomly drawn from a population of Evelyn Hone College students that voted in the December 2001 presidential elections in Zambia. The sample consisted of 30 randomly selected students who were purposely stratified in three focus groups of ten each. Each stratum represented the approximate ethnic equivalence of one of the presidential candidates who contested the December 2001 elections.
- Full Text:
- Date Issued: 2003
An object relational psychoanalysis of selected Tennessee Williams play texts
- Authors: Tosio, Paul
- Date: 2003
- Subjects: Williams, Tennessee, 1911-1983 Williams, Tennessee, 1911-1983 -- Knowledge -- Psychology Object relations (Psychoanalysis) Psychoanalysis Drama -- Psychological aspects
- Language: English
- Type: Thesis , Masters , MA
- Identifier: vital:2150 , http://hdl.handle.net/10962/d1002382
- Description: Tennessee Williams is a playwright of great psychological depth. This thesis probes some of the complexities of his work through the use of Object Relational Psychoanalysis, specifically employing the theories of Melanie Klein, W.R.D. Fairbairn and Donald Winnicott. The Glass Menagerie, A Streetcar Named Desire, Cat On A Hot Tin Roof and The Night of The Iguana are analysed from this theoretical stance. All of these plays display great perceptiveness into the human condition, accurately portraying many psychological relational themes. Certain Object Relational themes become very apparent in these analyses. These themes include, Dependency (especially in The Glass Menagerie), Reparation (particularly in A Streetcar Named Desire), Falsehood (notably in Cat on a Hot Tin Roof), Idealisation (evident in The Night of The Iguana), Honest Empathetic Relations (apparent in Cat on a Hot Tin Roof and The Night of The Iguana) as well as Guilt, Object Loss, Sexual Guilt, and Obligation (recurring throughout these plays). It is advanced that Williams’ plays posses an honest and insightful understanding of human relations and, as such, are of contemporary value. This Thesis is not only an academic study, but also has practical applications for dramatists. With an increased understanding of the intrinsic tensions and motivations within such plays, offered by such psychoanalytic strategy, performance and staging of such work may be enhanced valuably.
- Full Text:
- Date Issued: 2003
- Authors: Tosio, Paul
- Date: 2003
- Subjects: Williams, Tennessee, 1911-1983 Williams, Tennessee, 1911-1983 -- Knowledge -- Psychology Object relations (Psychoanalysis) Psychoanalysis Drama -- Psychological aspects
- Language: English
- Type: Thesis , Masters , MA
- Identifier: vital:2150 , http://hdl.handle.net/10962/d1002382
- Description: Tennessee Williams is a playwright of great psychological depth. This thesis probes some of the complexities of his work through the use of Object Relational Psychoanalysis, specifically employing the theories of Melanie Klein, W.R.D. Fairbairn and Donald Winnicott. The Glass Menagerie, A Streetcar Named Desire, Cat On A Hot Tin Roof and The Night of The Iguana are analysed from this theoretical stance. All of these plays display great perceptiveness into the human condition, accurately portraying many psychological relational themes. Certain Object Relational themes become very apparent in these analyses. These themes include, Dependency (especially in The Glass Menagerie), Reparation (particularly in A Streetcar Named Desire), Falsehood (notably in Cat on a Hot Tin Roof), Idealisation (evident in The Night of The Iguana), Honest Empathetic Relations (apparent in Cat on a Hot Tin Roof and The Night of The Iguana) as well as Guilt, Object Loss, Sexual Guilt, and Obligation (recurring throughout these plays). It is advanced that Williams’ plays posses an honest and insightful understanding of human relations and, as such, are of contemporary value. This Thesis is not only an academic study, but also has practical applications for dramatists. With an increased understanding of the intrinsic tensions and motivations within such plays, offered by such psychoanalytic strategy, performance and staging of such work may be enhanced valuably.
- Full Text:
- Date Issued: 2003
Analysis of material flow around a retractable pin in a friction stir weld
- Authors: Georgeou, Zacharias
- Date: 2003
- Subjects: Friction welding , Aluminum alloys -- Welding
- Language: English
- Type: Thesis , Masters , MTech (Mechanical Engineering)
- Identifier: vital:10812 , http://hdl.handle.net/10948/196 , Friction welding , Aluminum alloys -- Welding
- Description: Friction StirWelding (FSW) has been researched for a number of years since its inception in 1991. The work thus far has been based on understanding the material and thermal flow using the standard fixed pin tool. The keyhole resulting during tool extraction in a FSW weld, is a disadvantage and a current limiting factor. Eliminating this effect from a weld using a movable pin tools would make FSW more commercially viable. This dissertation focuses on the design of a novel retractable pin tool, and highlights the problems encountered during the welding of Aluminum plates, Al2024 and Al5083. Previously studied techniques of material and thermal flow were used, to investigate the effect of the tool during extraction in a FSW weld. A prototype retractable tool was designed using parametric and axiomatic design theory, and implementing a pneumatic muscle actuation system. The resulting problems in the calibration of the retractable pin tool and the resulting welds are presented, these results confirming previous studies. The movable pin produced discrepancies the heat generation around the shoulder during a FSW weld. The failure of this tool to produce a reasonable weld showed that previous ideas into the workings of a retractable pin tool requires further investigation, furthermore a fresh approach to the interpretation and understanding of the FSW weld process needs consideration.
- Full Text:
- Date Issued: 2003
- Authors: Georgeou, Zacharias
- Date: 2003
- Subjects: Friction welding , Aluminum alloys -- Welding
- Language: English
- Type: Thesis , Masters , MTech (Mechanical Engineering)
- Identifier: vital:10812 , http://hdl.handle.net/10948/196 , Friction welding , Aluminum alloys -- Welding
- Description: Friction StirWelding (FSW) has been researched for a number of years since its inception in 1991. The work thus far has been based on understanding the material and thermal flow using the standard fixed pin tool. The keyhole resulting during tool extraction in a FSW weld, is a disadvantage and a current limiting factor. Eliminating this effect from a weld using a movable pin tools would make FSW more commercially viable. This dissertation focuses on the design of a novel retractable pin tool, and highlights the problems encountered during the welding of Aluminum plates, Al2024 and Al5083. Previously studied techniques of material and thermal flow were used, to investigate the effect of the tool during extraction in a FSW weld. A prototype retractable tool was designed using parametric and axiomatic design theory, and implementing a pneumatic muscle actuation system. The resulting problems in the calibration of the retractable pin tool and the resulting welds are presented, these results confirming previous studies. The movable pin produced discrepancies the heat generation around the shoulder during a FSW weld. The failure of this tool to produce a reasonable weld showed that previous ideas into the workings of a retractable pin tool requires further investigation, furthermore a fresh approach to the interpretation and understanding of the FSW weld process needs consideration.
- Full Text:
- Date Issued: 2003
Analysis of the calling songs of Platypleura hirtipennis (Germar, 1834) and P. plumosa (Germar, 1834) (Hemiptera: Cicadidae)
- Sanborn, Allen F, Phillips, P K, Villet, Martin H
- Authors: Sanborn, Allen F , Phillips, P K , Villet, Martin H
- Date: 2003
- Language: English
- Type: text , Article
- Identifier: vital:6896 , http://hdl.handle.net/10962/d1011656
- Description: [From the introduction]: Most male cicadas produce a calling song in order to attract conspecific females. These songs have been shown to differ in closely related species (e.g. Alexander & Moore 1962; Villet 1988, 1989; Boulard 1995; Marshall & Cooley 2000; Sanborn & Phillips 2001) and in species which share habitats (e.g. Sueur 2002). The former is an inevitable part of the divergence of recognition signals that characterizes the speciation process in animals using acoustic signals (Villet 1995), while the latter would be expected from a signal that acts as a reproductive isolating mechanism (Claridge 1985; Marshall & Cooley 2000). Calling songs are therefore of value in resolving taxonomic problems in the cicadas.
- Full Text:
- Date Issued: 2003
- Authors: Sanborn, Allen F , Phillips, P K , Villet, Martin H
- Date: 2003
- Language: English
- Type: text , Article
- Identifier: vital:6896 , http://hdl.handle.net/10962/d1011656
- Description: [From the introduction]: Most male cicadas produce a calling song in order to attract conspecific females. These songs have been shown to differ in closely related species (e.g. Alexander & Moore 1962; Villet 1988, 1989; Boulard 1995; Marshall & Cooley 2000; Sanborn & Phillips 2001) and in species which share habitats (e.g. Sueur 2002). The former is an inevitable part of the divergence of recognition signals that characterizes the speciation process in animals using acoustic signals (Villet 1995), while the latter would be expected from a signal that acts as a reproductive isolating mechanism (Claridge 1985; Marshall & Cooley 2000). Calling songs are therefore of value in resolving taxonomic problems in the cicadas.
- Full Text:
- Date Issued: 2003
Aplousobranch ascidians (Tunicata: Ascidiacea) from Southern Africa
- Authors: Parker-Nance, Shirley
- Date: 2003
- Subjects: Sea squirts -- South Africa -- Classification , Aplousobranchia -- South Africa -- Classification
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:11078 , http://hdl.handle.net/10948/311 , Sea squirts -- South Africa -- Classification , Aplousobranchia -- South Africa -- Classification
- Description: The ascidian (subphylum Tunicata: class Ascidiacea) fauna along the southern African coast constitutes an important component of the sessile benthic reef fauna. Little is known of the species composition, biodiversity and distribution of ascidians on southern African intertidal and subtidal reefs. Past research on the ascidian fauna of South Africa was sporadic and limited, with only about one hundred and seventy species recorded during the last one hundred and twenty years. This is the first taxonomic study undertaken by a South African resident scientist. The study focused on six genera in four families (Euherdmaniidae, Polyclinidae, Pseudodistomidae and Didemnidae) belonging to the class Ascidiacea and suborder Aplousobranchia. Five species new to science, two Polyclinum, two Pseudodistoma and one Polysyncraton species are described. New additional information on the distribution of five species previously known to science, including one recorded for the first time along the South African coast, is presented. A literature review and comparison of the taxonomic important characteristics is made of all species known globally for the six genera. These six genera comprise twelve Euherdmania, fifteen Aplidiopsis, forty Polyclinum thirty-one Pseudodistoma, six Atriolum and sixty-eight Polysyncraton species.
- Full Text:
- Date Issued: 2003
- Authors: Parker-Nance, Shirley
- Date: 2003
- Subjects: Sea squirts -- South Africa -- Classification , Aplousobranchia -- South Africa -- Classification
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:11078 , http://hdl.handle.net/10948/311 , Sea squirts -- South Africa -- Classification , Aplousobranchia -- South Africa -- Classification
- Description: The ascidian (subphylum Tunicata: class Ascidiacea) fauna along the southern African coast constitutes an important component of the sessile benthic reef fauna. Little is known of the species composition, biodiversity and distribution of ascidians on southern African intertidal and subtidal reefs. Past research on the ascidian fauna of South Africa was sporadic and limited, with only about one hundred and seventy species recorded during the last one hundred and twenty years. This is the first taxonomic study undertaken by a South African resident scientist. The study focused on six genera in four families (Euherdmaniidae, Polyclinidae, Pseudodistomidae and Didemnidae) belonging to the class Ascidiacea and suborder Aplousobranchia. Five species new to science, two Polyclinum, two Pseudodistoma and one Polysyncraton species are described. New additional information on the distribution of five species previously known to science, including one recorded for the first time along the South African coast, is presented. A literature review and comparison of the taxonomic important characteristics is made of all species known globally for the six genera. These six genera comprise twelve Euherdmania, fifteen Aplidiopsis, forty Polyclinum thirty-one Pseudodistoma, six Atriolum and sixty-eight Polysyncraton species.
- Full Text:
- Date Issued: 2003
Apollo, Dionysus, dialectical reason and critical cinema
- Authors: Konik, Adrian
- Date: 2003
- Subjects: Motion pictures and language , Philosophy in motion pictures , Dionysus (Greek deity) in literature , Apollo (Greek deity) in literature
- Language: English
- Type: Thesis , Masters , MA
- Identifier: vital:10990 , http://hdl.handle.net/10948/295 , Motion pictures and language , Philosophy in motion pictures , Dionysus (Greek deity) in literature , Apollo (Greek deity) in literature
- Description: The contemporary era is dominated by an Apollonian visual language, i.e. the visual language of mainstream cinema and the mass media, and this study concerns the role that critical cinema, as Dionysian subverter, plays under such conditions. I argue that critical cinema should not be viewed as something completely ‘new’ but rather as a new, or at least the latest, manifestation of an older subversive ‘Dionysian’ voice that has made its presence felt since the dawn of the hegemony of an Apollonian disposition in Homeric epic. (I maintain that the history of western culture can be understood in terms of the persistent tension between Apollonian and Dionysian dispositions, and I use the distinction Derrida makes in Différance, between restricted and general economies, to distinguish between them, respectively.) I begin by considering the Dionysian echoes within Homer’s Iliad and then consider the way in which they became a ‘roar’ in the tragedies of Aeschylus. After Aeschylus a predominantly Apollonian voice asserted itself once again (to various degrees) through the work of Sophocles and Euripides. This was in keeping with the trend towards a more (Apollonian) restricted economy that is reflected in the writings of Homer’s literary successors, and which reached a crucial stage in Plato’s valorisation of ‘dialectics’, or what I term ‘dialecticis m’, which saw the birth of ‘dialectical language’. Through Plato dialecticism, or dialectical language, became instantiated as the ‘language’ of western philosophy and this predisposed western culture to develop along predominantly Apollonian lines. This continued from Plato, through the Middle Ages, until in the 17th century this Apollonian trend became manifest in the concept of the stable, integral, autonomous and self -transparent Cartesian ego, which is inextricably linked to dialectical language that promises certainty of ‘truth’ and maintains the possibility of representing the world in its entirety (as a system). In the contemporary ‘age of a world picture’, the hegemonic (Apollonian) visual language of mainstream cinema and the mass media propagates and perpetuates the belief in the possibility of representing the world in its entirety through the image, and insofar as it caters to audiences’ needs for stability and certainty (of ‘truth’) through providing such ‘complete’ representations, shapes their subjectivity along the lines of the Cartesian ego. According to Baudrillard, in contemporary society and culture the hyperreal realm of visual language has become far more significant for individuals than their immediate, empirical experiences, and that, as a result, they are far less predisposed to discussion and reflection and far more prone to passive ‘watching’. Also, Adorno maintains that it is impossible to have a form of critical cinema because of the way in which features inherent to cinema predispose it towards being an ideological apparatus. However, if both Baudrillard and Adorno are correct then the future appears increasingly bleak as it involves nothing other than the continuation and propagation of the hegemony of the visual language of mainstream cinema and the mass media, with no possibility for critical resistance. I argue instead that critical cinema is possible because the move towards a more restricted economy, motivated by an Apollonian disposition, did not develop from Homer to the contemporary era without meeting Dionysian resistance. I trace the presence of a subversive Dionysian voice through Homer’s Iliad, through Aeschylus’ Prometheus Bound, and through Plato’s Dialogues, where it echoes in the sentiments of some of Plato’s interlocutors, such as Callicles. In addition, I maintain that a ‘Dionysian’ voice resonates through both Nietzsche’s and Heidegger’s respective criticisms of ‘dialectical language’ and the ‘validity’ of the Cartesian ego. I argue that critical cinema, particularly Aronofsky’s postmodern critical cinema, parallels their similar epistemological and ontological perspectives in the way in which it engages with the (Apollonian) visual language of mainstream cinema and the mass media, and thereby, potentially, facilitates a more porous and protean subjectivity.
- Full Text:
- Date Issued: 2003
- Authors: Konik, Adrian
- Date: 2003
- Subjects: Motion pictures and language , Philosophy in motion pictures , Dionysus (Greek deity) in literature , Apollo (Greek deity) in literature
- Language: English
- Type: Thesis , Masters , MA
- Identifier: vital:10990 , http://hdl.handle.net/10948/295 , Motion pictures and language , Philosophy in motion pictures , Dionysus (Greek deity) in literature , Apollo (Greek deity) in literature
- Description: The contemporary era is dominated by an Apollonian visual language, i.e. the visual language of mainstream cinema and the mass media, and this study concerns the role that critical cinema, as Dionysian subverter, plays under such conditions. I argue that critical cinema should not be viewed as something completely ‘new’ but rather as a new, or at least the latest, manifestation of an older subversive ‘Dionysian’ voice that has made its presence felt since the dawn of the hegemony of an Apollonian disposition in Homeric epic. (I maintain that the history of western culture can be understood in terms of the persistent tension between Apollonian and Dionysian dispositions, and I use the distinction Derrida makes in Différance, between restricted and general economies, to distinguish between them, respectively.) I begin by considering the Dionysian echoes within Homer’s Iliad and then consider the way in which they became a ‘roar’ in the tragedies of Aeschylus. After Aeschylus a predominantly Apollonian voice asserted itself once again (to various degrees) through the work of Sophocles and Euripides. This was in keeping with the trend towards a more (Apollonian) restricted economy that is reflected in the writings of Homer’s literary successors, and which reached a crucial stage in Plato’s valorisation of ‘dialectics’, or what I term ‘dialecticis m’, which saw the birth of ‘dialectical language’. Through Plato dialecticism, or dialectical language, became instantiated as the ‘language’ of western philosophy and this predisposed western culture to develop along predominantly Apollonian lines. This continued from Plato, through the Middle Ages, until in the 17th century this Apollonian trend became manifest in the concept of the stable, integral, autonomous and self -transparent Cartesian ego, which is inextricably linked to dialectical language that promises certainty of ‘truth’ and maintains the possibility of representing the world in its entirety (as a system). In the contemporary ‘age of a world picture’, the hegemonic (Apollonian) visual language of mainstream cinema and the mass media propagates and perpetuates the belief in the possibility of representing the world in its entirety through the image, and insofar as it caters to audiences’ needs for stability and certainty (of ‘truth’) through providing such ‘complete’ representations, shapes their subjectivity along the lines of the Cartesian ego. According to Baudrillard, in contemporary society and culture the hyperreal realm of visual language has become far more significant for individuals than their immediate, empirical experiences, and that, as a result, they are far less predisposed to discussion and reflection and far more prone to passive ‘watching’. Also, Adorno maintains that it is impossible to have a form of critical cinema because of the way in which features inherent to cinema predispose it towards being an ideological apparatus. However, if both Baudrillard and Adorno are correct then the future appears increasingly bleak as it involves nothing other than the continuation and propagation of the hegemony of the visual language of mainstream cinema and the mass media, with no possibility for critical resistance. I argue instead that critical cinema is possible because the move towards a more restricted economy, motivated by an Apollonian disposition, did not develop from Homer to the contemporary era without meeting Dionysian resistance. I trace the presence of a subversive Dionysian voice through Homer’s Iliad, through Aeschylus’ Prometheus Bound, and through Plato’s Dialogues, where it echoes in the sentiments of some of Plato’s interlocutors, such as Callicles. In addition, I maintain that a ‘Dionysian’ voice resonates through both Nietzsche’s and Heidegger’s respective criticisms of ‘dialectical language’ and the ‘validity’ of the Cartesian ego. I argue that critical cinema, particularly Aronofsky’s postmodern critical cinema, parallels their similar epistemological and ontological perspectives in the way in which it engages with the (Apollonian) visual language of mainstream cinema and the mass media, and thereby, potentially, facilitates a more porous and protean subjectivity.
- Full Text:
- Date Issued: 2003
Applications of the Baylis-Hillman reaction in the synthesis of coumarin derivatives
- Authors: Musa, Musiliyu Ayodele
- Date: 2003
- Subjects: Coumarins Heterocyclic compounds -- Derivatives
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4403 , http://hdl.handle.net/10962/d1006705
- Description: The reaction of specially prepared salicylaldehyde benzyl ethers with the activated alkenes, methyl acrylate or acrylonitrile, in the presence of the catalyst, DABCO, has afforded Baylis-Hillman products, which have been subjected to conjugate addition with either piperidine or benzylamine. Hydrogenolysis of these conjugate addition products in the presence of a palladium-on-carbon catalyst has been shown to afford the corresponding 3-substituted coumarins, while treatment of O-benzylated Baylis-Hillman adducts with HCl or HI afforded the corresponding 3-(halomethyl)coumarins directly, in up to 94%. The 3-(halomethyl)coumarins have also been obtained in excellent yields (up to 98%) and even more conveniently, by treating the unprotected Baylis-Hillman products with HCl in a mixture of AcOH and Ac₂O, obtained from tert-butyl acrylate and various salicylaldehydes. The generality of an established route to the synthesis of coumarins via an intramolecular Baylis-Hillman reaction, involving the use of salicylaldehyde acrylate esters in the presence of DABCO, has also been demonstrated. Reactions between the 3-(halomethyl)coumarins and various nitrogen and carbon nucleophiles have been shown to proceed with a high degree of regioselectivity at the exocyclic allylic centre to afford 3-substituted coumarin products. The electronimpact mass spectra of selected coumarin derivatives have been investigated using high-resolution and B/E linked scan data. Fragmentation pathways have been proposed and fragmentation modes associated with different coumarin-containing analogues have been compared. A series of coumarin-containing analogues of ritonavir (a clinically useful HIV-1 protease inhibitor) have been prepared and characterized. The synthetic approach has involved the coupling of coumarin derivatives with a hydroxyethylene dipeptide isostere to afford ritonavir analogues containing coumarin termini. An interactive docking procedure has been used to explore the docking of ritonavir and a coumarincontaining analogue into the enzyme active site.
- Full Text:
- Date Issued: 2003
- Authors: Musa, Musiliyu Ayodele
- Date: 2003
- Subjects: Coumarins Heterocyclic compounds -- Derivatives
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4403 , http://hdl.handle.net/10962/d1006705
- Description: The reaction of specially prepared salicylaldehyde benzyl ethers with the activated alkenes, methyl acrylate or acrylonitrile, in the presence of the catalyst, DABCO, has afforded Baylis-Hillman products, which have been subjected to conjugate addition with either piperidine or benzylamine. Hydrogenolysis of these conjugate addition products in the presence of a palladium-on-carbon catalyst has been shown to afford the corresponding 3-substituted coumarins, while treatment of O-benzylated Baylis-Hillman adducts with HCl or HI afforded the corresponding 3-(halomethyl)coumarins directly, in up to 94%. The 3-(halomethyl)coumarins have also been obtained in excellent yields (up to 98%) and even more conveniently, by treating the unprotected Baylis-Hillman products with HCl in a mixture of AcOH and Ac₂O, obtained from tert-butyl acrylate and various salicylaldehydes. The generality of an established route to the synthesis of coumarins via an intramolecular Baylis-Hillman reaction, involving the use of salicylaldehyde acrylate esters in the presence of DABCO, has also been demonstrated. Reactions between the 3-(halomethyl)coumarins and various nitrogen and carbon nucleophiles have been shown to proceed with a high degree of regioselectivity at the exocyclic allylic centre to afford 3-substituted coumarin products. The electronimpact mass spectra of selected coumarin derivatives have been investigated using high-resolution and B/E linked scan data. Fragmentation pathways have been proposed and fragmentation modes associated with different coumarin-containing analogues have been compared. A series of coumarin-containing analogues of ritonavir (a clinically useful HIV-1 protease inhibitor) have been prepared and characterized. The synthetic approach has involved the coupling of coumarin derivatives with a hydroxyethylene dipeptide isostere to afford ritonavir analogues containing coumarin termini. An interactive docking procedure has been used to explore the docking of ritonavir and a coumarincontaining analogue into the enzyme active site.
- Full Text:
- Date Issued: 2003
Applied studies of some Southern African blowflies (Diptera: Calliphoridae) of forensic importance
- Authors: Lunt, Nicola
- Date: 2003
- Subjects: Diptera -- South Africa , Blowflies -- South Africa , Forensic entomology
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5803 , http://hdl.handle.net/10962/d1006202 , Diptera -- South Africa , Blowflies -- South Africa , Forensic entomology
- Description: Three major aspects of blowfly (Diptera: Calliphoridae) research were the focus of this study. Firstly, the phylogenetic relationships of 40 oestroid species from a variety of geographical localities were investigated using Cytochrome Oxidase b subunit I (COl) gene sequences. Maximum parsimony (MP) and Jukes-Cantor neighbor-joining (NJ) analyses both extracted a paraphyletic Calliphoridae, with the Calliphorinae-Luciliinae clade being sister to the Sarcophagidae. Short branch lengths within Chrysomya indicate a recent rapid radiation of this genus. Phormia and Protophormia either formed a sister clade to Chrysomya, or were embedded in this genus. Tree topologies were comparable between MP and NJ trees, but the positions of some genera were ambiguous. Secondly, developmental parameters and behaviour were investigated for four southern African species of forensically important blowflies viz. Chrysomya chloropyga, C. putoria, C. megacephala and Lucilia sericata, and ad hoc observations were made for Calliphora croceipalpis, Chrysomya marginalis and the predatory C. albiceps. Choice of oviposition substrate differed between species, mirroring substrate preferences in the field. Sexual dimorphism and dwarfism within a cohort complicated ageing maggots using size, but the use of developmental events (e.g. ecdysis) allowed ages to be determined unambiguously. Separate species status was supported for the previously synonymised C. chloropyga and C. putoria, by differences in maggot behaviour, larval growth rates and temperature optima. The proportion of total development time assigned to each larval instar and pupariation was variable among temperatures, but similar between congeneric species. Thirdly, since a negative linear relationship was found to occur between the developmental constant (K) and developmental zero (D₀) for both Calliphoridae and Sarcophagidae, the potential for predicting physiological parameters of unstudied taxa was investigated. Species and genera of Palaearctic origin generally had high K's and low D₀'s, and the reverse was true for the tropical taxa. It was found that both K and D₀ can be estimated for "unknown" taxa using the Felsenstein's Independent Contrasts (FIC) method of PDTree (Garland et al. 200 I), provided that branch lengths are relatively short and the phylogenetic position of the estimated taxon is unambiguous.
- Full Text:
- Date Issued: 2003
- Authors: Lunt, Nicola
- Date: 2003
- Subjects: Diptera -- South Africa , Blowflies -- South Africa , Forensic entomology
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5803 , http://hdl.handle.net/10962/d1006202 , Diptera -- South Africa , Blowflies -- South Africa , Forensic entomology
- Description: Three major aspects of blowfly (Diptera: Calliphoridae) research were the focus of this study. Firstly, the phylogenetic relationships of 40 oestroid species from a variety of geographical localities were investigated using Cytochrome Oxidase b subunit I (COl) gene sequences. Maximum parsimony (MP) and Jukes-Cantor neighbor-joining (NJ) analyses both extracted a paraphyletic Calliphoridae, with the Calliphorinae-Luciliinae clade being sister to the Sarcophagidae. Short branch lengths within Chrysomya indicate a recent rapid radiation of this genus. Phormia and Protophormia either formed a sister clade to Chrysomya, or were embedded in this genus. Tree topologies were comparable between MP and NJ trees, but the positions of some genera were ambiguous. Secondly, developmental parameters and behaviour were investigated for four southern African species of forensically important blowflies viz. Chrysomya chloropyga, C. putoria, C. megacephala and Lucilia sericata, and ad hoc observations were made for Calliphora croceipalpis, Chrysomya marginalis and the predatory C. albiceps. Choice of oviposition substrate differed between species, mirroring substrate preferences in the field. Sexual dimorphism and dwarfism within a cohort complicated ageing maggots using size, but the use of developmental events (e.g. ecdysis) allowed ages to be determined unambiguously. Separate species status was supported for the previously synonymised C. chloropyga and C. putoria, by differences in maggot behaviour, larval growth rates and temperature optima. The proportion of total development time assigned to each larval instar and pupariation was variable among temperatures, but similar between congeneric species. Thirdly, since a negative linear relationship was found to occur between the developmental constant (K) and developmental zero (D₀) for both Calliphoridae and Sarcophagidae, the potential for predicting physiological parameters of unstudied taxa was investigated. Species and genera of Palaearctic origin generally had high K's and low D₀'s, and the reverse was true for the tropical taxa. It was found that both K and D₀ can be estimated for "unknown" taxa using the Felsenstein's Independent Contrasts (FIC) method of PDTree (Garland et al. 200 I), provided that branch lengths are relatively short and the phylogenetic position of the estimated taxon is unambiguous.
- Full Text:
- Date Issued: 2003
Aspekte van die prosa van André P Brink met spesifieke verwysing na Sandkastele (1995)
- Authors: Vermeulen, Liezel
- Date: 2003
- Subjects: Brink, André P (André Philippus), 1935-2015 -- Sandkastele Brink, André P (André Philippus), 1935-2015
- Language: Afrikaans
- Type: Thesis , Masters , MA
- Identifier: vital:3605 , http://hdl.handle.net/10962/d1003809
- Description: Hierdie studie ondersoek aspekte van die prosa-oeuvre van die Suid-Afrikaanse outeur André P. Brink, met spesifieke verwysing na sy eerste post-apartheid roman Sandkastele (1995). Hierdie teks se feministiese hersiening van en alternatief tot die manlikgedomineerde en -gedokumenteerde amptelike geskiedenis van Suider-Afrika staan sentraal in die postmodernistiese, postkoloniale fase waarin die Brink prosa-oeuvre die verlede heroorweeg. Die pre-koloniale en koloniale verlede van die landstreek word herkaart deur die vertelling van stories van vroue van die verlede in 'n unieke vertelsituasie wat 'n her-verbeelde, tekstuele vrouegeskiedenis registreer. Die konsep "reimagination" wat ontwikkel in Brink se kritiese en literêr-teoretiese werke vanaf die publikasie van die essay "Imagining the real" in Mapmakers (1983) en Elleke Boehmer se konseptualisering van die tekstuele gevolge van dekolonisasie (1995) word ontgin. Spore van die magiese realisme, die postkolonialisme, die poststrukturalistiese postmodernisme en leeswyses en denkrigtings wat in die feminisme en genderstudies aandag geniet, word in Sandkastele se vertelling, narratiewe figure en ruimte ondersoek. Hierdie leesstrategie akkommodeer die Brink-oeuvre se voortdurende heroorweging en ontdekking van nuwe tekstuele moontlikhede, 'n proses wat gekenmerk word deur 'n reeks tematiese of konseptuele ontwikkelinge en die uit-en deurwerk van belangstellings van vorige Brinktekste. ABSTRACT: This study investigates aspects of the prose oeuvre of the South African author André P. Brink, with specific reference to his first post-apartheid novel Imaginings of Sand (1995). The feminist revisioning of the text as an alternative to the male-dominated and -documented official history of Southern Africa is central to the postmodernist, postcolonial phase of the Brink oeuvre in which the past is reconsidered. The pre-colonial and colonial past of the country is remapped through the stories of women of the past in a narrative construction which registers a re-imagined textual women's history. The concept "reimagination" which develops in Brink's critical and literary theoretical works from the publication of the essay "Imagining the real" in Mapmakers (1983) and Elleke Boehmer's conceptualisation of the textual effects of decolonisation (1995) is utilised. Traces of the magical realism, postcolonialism, poststructuralist postmodernism and approaches which are explored in feminism and gender studies are explored in Sandkastele's narrative construction, characters and space. This reading strategy accommodates the Brink oeuvre's continual re-evaluation and uncovering of new textual possibilities, a process that is characterised by a series of thematic or conceptual developments and the deployment of themes from previous Brink prose texts.
- Full Text:
- Date Issued: 2003
- Authors: Vermeulen, Liezel
- Date: 2003
- Subjects: Brink, André P (André Philippus), 1935-2015 -- Sandkastele Brink, André P (André Philippus), 1935-2015
- Language: Afrikaans
- Type: Thesis , Masters , MA
- Identifier: vital:3605 , http://hdl.handle.net/10962/d1003809
- Description: Hierdie studie ondersoek aspekte van die prosa-oeuvre van die Suid-Afrikaanse outeur André P. Brink, met spesifieke verwysing na sy eerste post-apartheid roman Sandkastele (1995). Hierdie teks se feministiese hersiening van en alternatief tot die manlikgedomineerde en -gedokumenteerde amptelike geskiedenis van Suider-Afrika staan sentraal in die postmodernistiese, postkoloniale fase waarin die Brink prosa-oeuvre die verlede heroorweeg. Die pre-koloniale en koloniale verlede van die landstreek word herkaart deur die vertelling van stories van vroue van die verlede in 'n unieke vertelsituasie wat 'n her-verbeelde, tekstuele vrouegeskiedenis registreer. Die konsep "reimagination" wat ontwikkel in Brink se kritiese en literêr-teoretiese werke vanaf die publikasie van die essay "Imagining the real" in Mapmakers (1983) en Elleke Boehmer se konseptualisering van die tekstuele gevolge van dekolonisasie (1995) word ontgin. Spore van die magiese realisme, die postkolonialisme, die poststrukturalistiese postmodernisme en leeswyses en denkrigtings wat in die feminisme en genderstudies aandag geniet, word in Sandkastele se vertelling, narratiewe figure en ruimte ondersoek. Hierdie leesstrategie akkommodeer die Brink-oeuvre se voortdurende heroorweging en ontdekking van nuwe tekstuele moontlikhede, 'n proses wat gekenmerk word deur 'n reeks tematiese of konseptuele ontwikkelinge en die uit-en deurwerk van belangstellings van vorige Brinktekste. ABSTRACT: This study investigates aspects of the prose oeuvre of the South African author André P. Brink, with specific reference to his first post-apartheid novel Imaginings of Sand (1995). The feminist revisioning of the text as an alternative to the male-dominated and -documented official history of Southern Africa is central to the postmodernist, postcolonial phase of the Brink oeuvre in which the past is reconsidered. The pre-colonial and colonial past of the country is remapped through the stories of women of the past in a narrative construction which registers a re-imagined textual women's history. The concept "reimagination" which develops in Brink's critical and literary theoretical works from the publication of the essay "Imagining the real" in Mapmakers (1983) and Elleke Boehmer's conceptualisation of the textual effects of decolonisation (1995) is utilised. Traces of the magical realism, postcolonialism, poststructuralist postmodernism and approaches which are explored in feminism and gender studies are explored in Sandkastele's narrative construction, characters and space. This reading strategy accommodates the Brink oeuvre's continual re-evaluation and uncovering of new textual possibilities, a process that is characterised by a series of thematic or conceptual developments and the deployment of themes from previous Brink prose texts.
- Full Text:
- Date Issued: 2003
Basalt geochemistry and tectonic discrimination within continental flood basalt provinces
- Authors: Marsh, Julian S
- Date: 2003
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/140412 , vital:37886 , https://doi.org/10.1016/0377-0273(87)90035-7
- Description: Continental flood basalts are usually regarded as a single tectonomagmatic entity but frequently quoted examples exhibit a variety of tectonic settings. In one well-studied, classic, flood basalt province, the Mesozoic Karoo province of southern Africa, magmatism occurred in the following tectonic settings: (a) continental rifting leading to ocean-floor spreading in the South Atlantic Ocean (Etendeka suite of Namibia); (b) stretched continental lithosphere and rifting not leading directly to ocean-floor formation (Lebombo suite of southeastern Africa); and (c) an a-tectonic, within-plate, continental setting characterized by an absence of faulting or warping (Lesotho highlands and Karoo dolerites of South Africa).
- Full Text: false
- Date Issued: 2003
- Authors: Marsh, Julian S
- Date: 2003
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/140412 , vital:37886 , https://doi.org/10.1016/0377-0273(87)90035-7
- Description: Continental flood basalts are usually regarded as a single tectonomagmatic entity but frequently quoted examples exhibit a variety of tectonic settings. In one well-studied, classic, flood basalt province, the Mesozoic Karoo province of southern Africa, magmatism occurred in the following tectonic settings: (a) continental rifting leading to ocean-floor spreading in the South Atlantic Ocean (Etendeka suite of Namibia); (b) stretched continental lithosphere and rifting not leading directly to ocean-floor formation (Lebombo suite of southeastern Africa); and (c) an a-tectonic, within-plate, continental setting characterized by an absence of faulting or warping (Lesotho highlands and Karoo dolerites of South Africa).
- Full Text: false
- Date Issued: 2003
Between the Reds and the Greens: a geographical interpretation of the land question in South Africa
- Authors: Fox, Roddy C
- Date: 2003
- Language: English
- Type: Text
- Identifier: vital:575 , http://hdl.handle.net/10962/d1006657
- Description: This inaugural lecture is in two parts: each related to a different nexus of the four types of scholarly activity. The first reflects on my career and is an examination of how I have developed as a teacher and learner. The key scholarly activities being discovery, integration and teaching. The second part reflects on the evolution of my research interests and leads up to an examination of the land question in South Africa. The scholarly activities in this part of the lecture are discovery, integration and application.
- Full Text:
- Date Issued: 2003
- Authors: Fox, Roddy C
- Date: 2003
- Language: English
- Type: Text
- Identifier: vital:575 , http://hdl.handle.net/10962/d1006657
- Description: This inaugural lecture is in two parts: each related to a different nexus of the four types of scholarly activity. The first reflects on my career and is an examination of how I have developed as a teacher and learner. The key scholarly activities being discovery, integration and teaching. The second part reflects on the evolution of my research interests and leads up to an examination of the land question in South Africa. The scholarly activities in this part of the lecture are discovery, integration and application.
- Full Text:
- Date Issued: 2003
Binding and transcriptional activation by Uga3p, a zinc binuclear cluster protein of Saccharomyces cerevisiae redefining the UAS [subscript GABA] and the Uga3p binding site
- Authors: Idicula, Anu Mary
- Date: 2003
- Subjects: Saccharomyces cerevisiae GABA
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:3933 , http://hdl.handle.net/10962/d1003992
- Description: Uga3p, a member of the zinc binuclear cluster transcription factor family, is required for [gamma]-aminobutyric acid-dependent transcription of the UGA genes in Saccharomyces cerevisiae. Crystallographic data of some of the protein-DNA complexes of this family reveal that members of this family bind to CGG triplets. A conserved 19-nucleotide activation element in certain UGA gene promoter regions contains a CCG-N4-CGG everted repeat, proposed to be the binding site of Uga3p, UAS[subscript GABA]. The spacer region (N4) between the CGG triplets has been suggested to be the specificity determinant for binding to UAS[subscript GABA]. The data available from the Saccharomyces genome database indicates that there are multiple repeats of -CCG-N4-CGG- regions within the genome. These transcription factors are involved in the activation of specific pathways and the question arises as to how their specificity of binding is determined. The aim of this study was to understand the binding characteristics of Uga3p to UAS[subscript GABA] and to determine the affinity and specificity of this interaction. In this study, full-length (tagged and untagged) and truncated (1-124 a.a.) Uga3p was produced in a heterologous expression system (E. coli). The interaction of Uga3p with UAS[subscript GABA] in Saccharomyces cerevisiae was characterized in terms of binding in vitro and the transcriptional activation of lacZ reporter genes in vivo. The Uga3p was capable of binding to these sites in vitro independent of exogenous GABA. Electrophoretic mobility shift assays (EMSA) of the full-length Uga3p with the wild type UAS[subscript GABA] sequences produced two distinct mobility complexes. The complexes formed in the EMSA of the full-length Uga3p were those specific to the interaction of the Uga3p to UAS[subscript GABA]. The truncated Uga3p(1-124 a.a.), which has the DNA-binding zinc cluster domain, the linker region and the putative coiled-coil domain was not functionally equivalent to the full-length protein with respect to binding in vitro because the EMSAs of the UAS[subscript GABA] with the truncated Uga3p produced indistinct complexes. EMSAs using mutant UAS[subscript GABA] sequences and heterologously-produced full-length Uga3p, demonstrated that UAS[subscript GABA] consists of two, independent Uga3p-binding sites. This work presents evidence that the two Uga3p molecules bound to UAS[subscript GABA] most likely interact with each other. Unlike other zinc cluster binding sites the Uga3p-binding site is an asymmetric site of 5’-SGCGGNWWT-3’ (S= G or C, W = A or T and N = no nucleotide or G or C). UAS[subscript GABA] is a palindrome containing the two asymmetric Uga3p-binding sites. The two-site consensus sequence required for the binding of Uga3p to the UAS[subscript GABA] is present upstream of UGA1 (region -387 to -370) and UGA4 (region -403 to -387). Furthermore, a single Uga3p-binding site was identified in the 5’ untranslated regions of UGA2 (region -219 to -211). GABA-dependent transcriptional activation by UAS[subscript GABA] in vivo could be directly correlated to a high affinity, specific interaction of two Uga3p molecules to this UAS. Binding with high affinity required the conserved sequences flanking the everted repeat. This study provided evidence that the binding pattern of Uga3p is novel compared to other zinc cluster motifs investigated, as the sequences flanking the everted repeat are important regions for recognition by Uga3p. The studies with the truncated Uga3p (1 –124 a.a.), also suggested that the regions C-terminal to the DNA-binding motif and putative coiled-coil area of this protein are important for Uga3p-specific interactions with UAS[subscript GABA]. Investigation of regions C-terminal to the zinc cluster, linker and putative coiledcoil revealed an eight-motif regulatory region similar to that in other zinc cluster proteins. This indicated that the regions C-terminal to these domains are important for the regulation and activity of these proteins. A putative seven repeat WD40-like motif was identified within this region. This putative domain has been speculated to be important for protein-protein interactions. Phosphorylation and dephosphorylation in other proteins of this class have been indicated to be important for the regulation of the activity of these proteins. The bioinformatic analysis of Uga3p revealed two possible cAMP/cGMP-dependent protein kinase phosphorylation sites, four putative protein kinase C phosphorylation motifs and four putative casein kinase II phosphorylation motifs. This study has contributed to the understanding of the nature of interactions between Uga3p and its specific UAS [subscript GABA] and how the regions flanking the everted repeat determine its specificity. The comparison of the nature of the binding of truncated and full-length Uga3p in vitro provided evidence for the role played by the full-length protein in determining this specific interaction. This evidence suggested that the in vitro binding evidence for other proteins of this family, using truncated peptides that carry the DNA-binding domain, might not reflect the true nature of interactions between the proteins of this class and their specific UASs in vivo.
- Full Text:
- Date Issued: 2003
- Authors: Idicula, Anu Mary
- Date: 2003
- Subjects: Saccharomyces cerevisiae GABA
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:3933 , http://hdl.handle.net/10962/d1003992
- Description: Uga3p, a member of the zinc binuclear cluster transcription factor family, is required for [gamma]-aminobutyric acid-dependent transcription of the UGA genes in Saccharomyces cerevisiae. Crystallographic data of some of the protein-DNA complexes of this family reveal that members of this family bind to CGG triplets. A conserved 19-nucleotide activation element in certain UGA gene promoter regions contains a CCG-N4-CGG everted repeat, proposed to be the binding site of Uga3p, UAS[subscript GABA]. The spacer region (N4) between the CGG triplets has been suggested to be the specificity determinant for binding to UAS[subscript GABA]. The data available from the Saccharomyces genome database indicates that there are multiple repeats of -CCG-N4-CGG- regions within the genome. These transcription factors are involved in the activation of specific pathways and the question arises as to how their specificity of binding is determined. The aim of this study was to understand the binding characteristics of Uga3p to UAS[subscript GABA] and to determine the affinity and specificity of this interaction. In this study, full-length (tagged and untagged) and truncated (1-124 a.a.) Uga3p was produced in a heterologous expression system (E. coli). The interaction of Uga3p with UAS[subscript GABA] in Saccharomyces cerevisiae was characterized in terms of binding in vitro and the transcriptional activation of lacZ reporter genes in vivo. The Uga3p was capable of binding to these sites in vitro independent of exogenous GABA. Electrophoretic mobility shift assays (EMSA) of the full-length Uga3p with the wild type UAS[subscript GABA] sequences produced two distinct mobility complexes. The complexes formed in the EMSA of the full-length Uga3p were those specific to the interaction of the Uga3p to UAS[subscript GABA]. The truncated Uga3p(1-124 a.a.), which has the DNA-binding zinc cluster domain, the linker region and the putative coiled-coil domain was not functionally equivalent to the full-length protein with respect to binding in vitro because the EMSAs of the UAS[subscript GABA] with the truncated Uga3p produced indistinct complexes. EMSAs using mutant UAS[subscript GABA] sequences and heterologously-produced full-length Uga3p, demonstrated that UAS[subscript GABA] consists of two, independent Uga3p-binding sites. This work presents evidence that the two Uga3p molecules bound to UAS[subscript GABA] most likely interact with each other. Unlike other zinc cluster binding sites the Uga3p-binding site is an asymmetric site of 5’-SGCGGNWWT-3’ (S= G or C, W = A or T and N = no nucleotide or G or C). UAS[subscript GABA] is a palindrome containing the two asymmetric Uga3p-binding sites. The two-site consensus sequence required for the binding of Uga3p to the UAS[subscript GABA] is present upstream of UGA1 (region -387 to -370) and UGA4 (region -403 to -387). Furthermore, a single Uga3p-binding site was identified in the 5’ untranslated regions of UGA2 (region -219 to -211). GABA-dependent transcriptional activation by UAS[subscript GABA] in vivo could be directly correlated to a high affinity, specific interaction of two Uga3p molecules to this UAS. Binding with high affinity required the conserved sequences flanking the everted repeat. This study provided evidence that the binding pattern of Uga3p is novel compared to other zinc cluster motifs investigated, as the sequences flanking the everted repeat are important regions for recognition by Uga3p. The studies with the truncated Uga3p (1 –124 a.a.), also suggested that the regions C-terminal to the DNA-binding motif and putative coiled-coil area of this protein are important for Uga3p-specific interactions with UAS[subscript GABA]. Investigation of regions C-terminal to the zinc cluster, linker and putative coiledcoil revealed an eight-motif regulatory region similar to that in other zinc cluster proteins. This indicated that the regions C-terminal to these domains are important for the regulation and activity of these proteins. A putative seven repeat WD40-like motif was identified within this region. This putative domain has been speculated to be important for protein-protein interactions. Phosphorylation and dephosphorylation in other proteins of this class have been indicated to be important for the regulation of the activity of these proteins. The bioinformatic analysis of Uga3p revealed two possible cAMP/cGMP-dependent protein kinase phosphorylation sites, four putative protein kinase C phosphorylation motifs and four putative casein kinase II phosphorylation motifs. This study has contributed to the understanding of the nature of interactions between Uga3p and its specific UAS [subscript GABA] and how the regions flanking the everted repeat determine its specificity. The comparison of the nature of the binding of truncated and full-length Uga3p in vitro provided evidence for the role played by the full-length protein in determining this specific interaction. This evidence suggested that the in vitro binding evidence for other proteins of this family, using truncated peptides that carry the DNA-binding domain, might not reflect the true nature of interactions between the proteins of this class and their specific UASs in vivo.
- Full Text:
- Date Issued: 2003
Bioaccumulation and histopathology of copper in Oreochromis mossambicus
- Authors: Naigaga, Irene
- Date: 2003
- Subjects: Mozambique tilapia , Copper , Marine toxins , Fishes -- Effect of water pollution on , Water -- Pollution -- Environmental aspects
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5234 , http://hdl.handle.net/10962/d1005077 , Mozambique tilapia , Copper , Marine toxins , Fishes -- Effect of water pollution on , Water -- Pollution -- Environmental aspects
- Description: Cu is one of the most toxic elements that affect fish populations when the fish are exposed to concentrations exceeding their tolerance. To investigate the effects of elementary Cu on aspects of bioconcentration, histology and behaviour, O. mossambicus were exposed to 0 and 0.75 ± 0.20 mg/l of Cu for 96 hours (short-term study), and 0, 0.11 ± 0.02, 0.29 ± 0.02, and 0.47 ± 0.04 mg/l of Cu for 64 days (longterm study) under controlled conditions in the laboratory. For the long-term study fish were sampled for gills, liver, and kidney Cu accumulation analysis after 1, 32 and 64 days of exposure and after 1, 2, 4, 16, 32, and 64 days for gills, liver and spleen histology analysis. Cu accumulation was concentration-duration dependent with the highest accumulation capacity in the liver. A multifactor linear model was developed for the relationship between exposure dose, exposure duration and Cu accumulation in the organs with the liver model: Log L = 3.35 + 0.85W + 0.31T (r² = 0.892) giving a better fit than the gills: G = −35.09 + 10.58W + 17.58T (r² = 0.632). Where L = Cu accumulation values in the liver, G = Cu accumulation values in the gills (both in μg/g dry mass); W = exposure dose in water (mg/l); and T = exposure time (days). Using this model Cu accumulation in organs can be estimated when exposure concentration and duration is known. This model should be tested under different conditions to determine the potential of the model in monitoring Cu toxicity in the environment. Lesions were observed in the liver, gills and spleen in all Cu treatments at all exposure concentration and exposure durations. However, the incidence and the degree of alteration was related to the concentration of Cu and duration of exposure. The sequential appearance of lesions in the order of, hepatic vacuolar degeneration, fatty degeneration and necrosis indicated a gradual increase in liver damage with larger duration of exposure time and increasing Cu concentration. The initial lesions in the gills were manifested as hypertrophy and hyperplasia of the gill epithelium causing increase in the thickness of the secondary lamellae, mucous cell hypertrophy and proliferation, mucous hypersecretion, proliferation of eosinophilic granule cells and hyperplasia of interlamellar cells. With increase in exposure time, necrosis of the eosinophilic granule cells, lamellar oedema, epithelial desquamation and increase in severity of lamellar hyperplasia were observed. These lesions indicated an initial defence mechanism of the fish against Cu toxicity followed by advanced histological changes that were related to Cu concentration and duration of exposure. Changes in the spleen were haemosiderosis, increase in the white pulp and macrophage centres, reduction in the red pulp, and necrosis suggesting that fish exposed to environmentally relevant levels of Cu may be histopathologically altered leading to anaemia and immunosuppression. Regression analysis was used to quantify the relationship between the total activity of the fish, and duration of exposure. There was a gradual decline in fish activity related to Cu concentration and duration of exposure before introducing food into the tanks. There was a constant activity after introducing food in the tanks at the control and 0.11 ± 0.02 mg/l Cu exposure levels irrespective of exposure time. Analysis of covariance (ANCOVA) was used to test for the difference in slopes between treatments. There was no significant difference (p > 0.05) between slopes of the control and 0.11 ± 0.02 mg/l Cu, and between 0.29 ± 0.02 and 47 ± 0.04 mg/l Cu before and after introducing food in the tanks. The slopes of both the control and 0.11 ± 0.02 mg/l Cu were significantly different from those of 0.29 ± 0.02 and 0.47 ± 0.04 mg/l Cu (p < 0.05). There were significant differences in the mean opercular movements per minute between treatments (p < 0.05). There was hyperventilation at 0.11 ± 0.02 mg/l Cu i.e. 87 ± 18 opercular movements per minute (mean ± standard deviation) and hypoventilation at 0.29 ± 0.02 and 0.47 ± 0.04 mg/l Cu i.e. 37 ± 34 and 13 ± 6 opercular movements per minute compared to the control. Hypo- and hyperventilation were related to the lesser and greater gill damage, respectively. In conclusion Cu accumulation and effects on histology of the liver, gills and were related to the concentration of Cu in the water and duration of exposure showing a gradual increase in incidence and intensity with larger duration of exposure time and increasing Cu concentration. The fish were initially able to homeostatically regulate and detoxify Cu. However, as the exposure continued, the homeostatic mechanism appears to have failed to cope with the increasing metal burden causing advanced histological changes.
- Full Text:
- Date Issued: 2003
- Authors: Naigaga, Irene
- Date: 2003
- Subjects: Mozambique tilapia , Copper , Marine toxins , Fishes -- Effect of water pollution on , Water -- Pollution -- Environmental aspects
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5234 , http://hdl.handle.net/10962/d1005077 , Mozambique tilapia , Copper , Marine toxins , Fishes -- Effect of water pollution on , Water -- Pollution -- Environmental aspects
- Description: Cu is one of the most toxic elements that affect fish populations when the fish are exposed to concentrations exceeding their tolerance. To investigate the effects of elementary Cu on aspects of bioconcentration, histology and behaviour, O. mossambicus were exposed to 0 and 0.75 ± 0.20 mg/l of Cu for 96 hours (short-term study), and 0, 0.11 ± 0.02, 0.29 ± 0.02, and 0.47 ± 0.04 mg/l of Cu for 64 days (longterm study) under controlled conditions in the laboratory. For the long-term study fish were sampled for gills, liver, and kidney Cu accumulation analysis after 1, 32 and 64 days of exposure and after 1, 2, 4, 16, 32, and 64 days for gills, liver and spleen histology analysis. Cu accumulation was concentration-duration dependent with the highest accumulation capacity in the liver. A multifactor linear model was developed for the relationship between exposure dose, exposure duration and Cu accumulation in the organs with the liver model: Log L = 3.35 + 0.85W + 0.31T (r² = 0.892) giving a better fit than the gills: G = −35.09 + 10.58W + 17.58T (r² = 0.632). Where L = Cu accumulation values in the liver, G = Cu accumulation values in the gills (both in μg/g dry mass); W = exposure dose in water (mg/l); and T = exposure time (days). Using this model Cu accumulation in organs can be estimated when exposure concentration and duration is known. This model should be tested under different conditions to determine the potential of the model in monitoring Cu toxicity in the environment. Lesions were observed in the liver, gills and spleen in all Cu treatments at all exposure concentration and exposure durations. However, the incidence and the degree of alteration was related to the concentration of Cu and duration of exposure. The sequential appearance of lesions in the order of, hepatic vacuolar degeneration, fatty degeneration and necrosis indicated a gradual increase in liver damage with larger duration of exposure time and increasing Cu concentration. The initial lesions in the gills were manifested as hypertrophy and hyperplasia of the gill epithelium causing increase in the thickness of the secondary lamellae, mucous cell hypertrophy and proliferation, mucous hypersecretion, proliferation of eosinophilic granule cells and hyperplasia of interlamellar cells. With increase in exposure time, necrosis of the eosinophilic granule cells, lamellar oedema, epithelial desquamation and increase in severity of lamellar hyperplasia were observed. These lesions indicated an initial defence mechanism of the fish against Cu toxicity followed by advanced histological changes that were related to Cu concentration and duration of exposure. Changes in the spleen were haemosiderosis, increase in the white pulp and macrophage centres, reduction in the red pulp, and necrosis suggesting that fish exposed to environmentally relevant levels of Cu may be histopathologically altered leading to anaemia and immunosuppression. Regression analysis was used to quantify the relationship between the total activity of the fish, and duration of exposure. There was a gradual decline in fish activity related to Cu concentration and duration of exposure before introducing food into the tanks. There was a constant activity after introducing food in the tanks at the control and 0.11 ± 0.02 mg/l Cu exposure levels irrespective of exposure time. Analysis of covariance (ANCOVA) was used to test for the difference in slopes between treatments. There was no significant difference (p > 0.05) between slopes of the control and 0.11 ± 0.02 mg/l Cu, and between 0.29 ± 0.02 and 47 ± 0.04 mg/l Cu before and after introducing food in the tanks. The slopes of both the control and 0.11 ± 0.02 mg/l Cu were significantly different from those of 0.29 ± 0.02 and 0.47 ± 0.04 mg/l Cu (p < 0.05). There were significant differences in the mean opercular movements per minute between treatments (p < 0.05). There was hyperventilation at 0.11 ± 0.02 mg/l Cu i.e. 87 ± 18 opercular movements per minute (mean ± standard deviation) and hypoventilation at 0.29 ± 0.02 and 0.47 ± 0.04 mg/l Cu i.e. 37 ± 34 and 13 ± 6 opercular movements per minute compared to the control. Hypo- and hyperventilation were related to the lesser and greater gill damage, respectively. In conclusion Cu accumulation and effects on histology of the liver, gills and were related to the concentration of Cu in the water and duration of exposure showing a gradual increase in incidence and intensity with larger duration of exposure time and increasing Cu concentration. The fish were initially able to homeostatically regulate and detoxify Cu. However, as the exposure continued, the homeostatic mechanism appears to have failed to cope with the increasing metal burden causing advanced histological changes.
- Full Text:
- Date Issued: 2003
Biogeography and community structure of fishes in South African estuaries
- Authors: Harrison, Trevor D
- Date: 2003
- Subjects: Estuarine ecology -- South Africa Estuarine fishes -- South Africa Fish communities -- South Africa Biogeography -- South Africa
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5235 , http://hdl.handle.net/10962/d1005078
- Description: The biogeography and community structure of the fishes of South African estuaries was investigated. In all, 109 systems were examined representing two broad types: temporarily closed and permanently open estuaries. Multivariate analyses of the fish communities identified three biogeographic regions. A cool-temperate region extended along the west and southwest coasts; a warmtemperate zone stretched along the south, southeast and east coasts and a subtropical region occurred along the east coast. The boundaries of these biogeographic regions were also delineated. The general physico-chemical characteristics of the estuaries within the three biogeographic regions also reflected regional differences in climate, rainfall and ocean conditions. Estuarine temperatures followed the trend for marine coastal waters, decreasing from subtropical estuaries toward cool-temperate systems. The low rainfall and runoff in the warm-temperate region together with high evaporation rates and strong seawater input resulted in higher salinities in these estuaries. These factors also accounted for the predominantly clearer waters in warm-temperate estuaries. The estuaries in the three biogeographic regions were also shown to contain somewhat distinctive fish assemblages. Temperature and salinity appeared to be the two main factors affecting the distribution and abundance of fishes in South African estuaries. Subtropical systems were characterised by fishes mostly of tropical origin as well as certain south coast endemic species. Warm-temperate estuaries were dominated by endemic taxa with some tropical species also present. The fish fauna of cooltemperate estuaries mostly comprised south coast endemic species with cosmopolitan and temperate taxa also present. Certain functional components of the ichthyofauna also exhibited slight differences between regions. Freshwater fishes were a major component of closed subtropical estuaries while estuarine resident species were more abundant in warm-temperate estuaries. Overall, estuarine-dependent marine species dominated the fish fauna of the estuaries in all biogeographic regions, signifying that South African estuaries perform a vital nursery function for this group of fishes. Slight differences were also apparent in the trophic structure of the fishes; these were related to environmental differences between regions. Zooplanktivores and fishes that feed on aquatic macrophytes/invertebrates assumed a relatively higher importance in warm-temperate systems. Overall, detritivores dominated the estuarine fish fauna in all regions, indicating that detritus forms the main energy source in South African estuaries.
- Full Text:
- Date Issued: 2003
- Authors: Harrison, Trevor D
- Date: 2003
- Subjects: Estuarine ecology -- South Africa Estuarine fishes -- South Africa Fish communities -- South Africa Biogeography -- South Africa
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5235 , http://hdl.handle.net/10962/d1005078
- Description: The biogeography and community structure of the fishes of South African estuaries was investigated. In all, 109 systems were examined representing two broad types: temporarily closed and permanently open estuaries. Multivariate analyses of the fish communities identified three biogeographic regions. A cool-temperate region extended along the west and southwest coasts; a warmtemperate zone stretched along the south, southeast and east coasts and a subtropical region occurred along the east coast. The boundaries of these biogeographic regions were also delineated. The general physico-chemical characteristics of the estuaries within the three biogeographic regions also reflected regional differences in climate, rainfall and ocean conditions. Estuarine temperatures followed the trend for marine coastal waters, decreasing from subtropical estuaries toward cool-temperate systems. The low rainfall and runoff in the warm-temperate region together with high evaporation rates and strong seawater input resulted in higher salinities in these estuaries. These factors also accounted for the predominantly clearer waters in warm-temperate estuaries. The estuaries in the three biogeographic regions were also shown to contain somewhat distinctive fish assemblages. Temperature and salinity appeared to be the two main factors affecting the distribution and abundance of fishes in South African estuaries. Subtropical systems were characterised by fishes mostly of tropical origin as well as certain south coast endemic species. Warm-temperate estuaries were dominated by endemic taxa with some tropical species also present. The fish fauna of cooltemperate estuaries mostly comprised south coast endemic species with cosmopolitan and temperate taxa also present. Certain functional components of the ichthyofauna also exhibited slight differences between regions. Freshwater fishes were a major component of closed subtropical estuaries while estuarine resident species were more abundant in warm-temperate estuaries. Overall, estuarine-dependent marine species dominated the fish fauna of the estuaries in all biogeographic regions, signifying that South African estuaries perform a vital nursery function for this group of fishes. Slight differences were also apparent in the trophic structure of the fishes; these were related to environmental differences between regions. Zooplanktivores and fishes that feed on aquatic macrophytes/invertebrates assumed a relatively higher importance in warm-temperate systems. Overall, detritivores dominated the estuarine fish fauna in all regions, indicating that detritus forms the main energy source in South African estuaries.
- Full Text:
- Date Issued: 2003
Biological control initiatives against Lantana camara L. (Verbenaceae) in South Africa : an assessment of the present status of the programme, and an evaluation of Coelocephalapion camarae Kissinger (Coleoptera: Brentidae) and Falconia intermedia (Distant) (Heteroptera: Miridae), two new candidate natural enemies for release on the weed
- Authors: Baars, Jan-Robert
- Date: 2003
- Subjects: Lantana camara Lantana camera -- South Africa Biological pest control agents -- South Africa Beetles -- South Africa Hemiptera -- South Africa Weeds -- Biological control -- South Africa
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5647 , http://hdl.handle.net/10962/d1005329
- Description: Lantana camara (lantana), a thicket-forming shrub, a number of different varieties of which were introduced into South Africa as ornamental plants but which has become a serious invasive weed. Conventional control measures for lantana are expensive and ineffective and it has therefore been targeted for biological control since 1961. To date, eleven biological control agent species have become established on lantana in South Africa. However, most agents persist at low densities and only occasionally impact plant populations. Three species regularly cause significant damage, but only reach sufficiently high numbers by midsummer after populations crash during the winter. Overall, the impact of the biological control programme on the weed is negligible and this has been ascribed to the poor selection of agents for release, the accumulation of native parasitoids, differences in insect preference for different varieties of the weed and variable climatic conditions over the weed’s range. This study suggests that the importance of varietal preferences has been over-estimated. A predictive bioclimatic modelling technique showed that most of the agents established in South Africa have a wide climatic tolerance and that the redistribution and importation of new climatypes of these agents will not improve the level of control. Additional agents are required to improve the biocontrol in the temperate conditions, and also to increase damage in the sub-tropical areas where most of the agents are established and where the weed retains its leaves year round. New candidate agents that possess biological attributes that favour a high intrinsic rate of increase, a high impact per individual and that improve the synchrony between the weed and the agent in climatic conditions that promote the seasonal leaflessness of plants should receive prior consideration. A survey in Jamaica indicated that additional biological control agents are available in the region of origin but that care should be taken to prioritise the most effective agents. The various selection systems currently available in weed biocontrol produce contradictory results in the priority assigned to candidate agents and a new selection system is proposed. The biology and host range of two new candidate natural enemies, the leaf-galling weevil, Coelocephalapion camarae and the leaf-sucking mirid, Falconia intermedia were investigated for the biocontrol of lantana. The studies indicated that these have considerable biocontrol potential, in that the weevil has a wide climatic tolerance and has the potential to survive the host leaflessness typical of temperate conditions, while the mirid has a high intrinsic rate of increase, and the potential for several generations a year. Both agents caused a high level of damage to the leaves, with the weevil galling the vascular tissue in the leaf-petiole and the mirid causing chlorotic speckling of the leaves. During laboratory trials both agents accepted indigenous species in the genus Lippia. However, under multiple choice conditions these agents showed a significant and strong oviposition preference for lantana. A risk assessment and post release field trials indicated that F. intermedia is likely to attack some Lippia species in the presence of lantana, but the levels of damage are predicted to be relatively low. A possible low incidence of damage to indigenous species was considered a justifiable ‘trade-off’ for the potentially marked impact on L. camara. Preference and performance studies on the two candidate agents suggested that most of the South African lantana varieties are suitable host plants. The mirid preferred certain varieties in multiple choice experiments, but this is unlikely to affect its impact under field conditions. Permission for release was accordingly sought for both species. Finally, the challenges facing the biological control programme and the potential for improving the control of L. camara in South Africa are considered.
- Full Text:
- Date Issued: 2003
- Authors: Baars, Jan-Robert
- Date: 2003
- Subjects: Lantana camara Lantana camera -- South Africa Biological pest control agents -- South Africa Beetles -- South Africa Hemiptera -- South Africa Weeds -- Biological control -- South Africa
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5647 , http://hdl.handle.net/10962/d1005329
- Description: Lantana camara (lantana), a thicket-forming shrub, a number of different varieties of which were introduced into South Africa as ornamental plants but which has become a serious invasive weed. Conventional control measures for lantana are expensive and ineffective and it has therefore been targeted for biological control since 1961. To date, eleven biological control agent species have become established on lantana in South Africa. However, most agents persist at low densities and only occasionally impact plant populations. Three species regularly cause significant damage, but only reach sufficiently high numbers by midsummer after populations crash during the winter. Overall, the impact of the biological control programme on the weed is negligible and this has been ascribed to the poor selection of agents for release, the accumulation of native parasitoids, differences in insect preference for different varieties of the weed and variable climatic conditions over the weed’s range. This study suggests that the importance of varietal preferences has been over-estimated. A predictive bioclimatic modelling technique showed that most of the agents established in South Africa have a wide climatic tolerance and that the redistribution and importation of new climatypes of these agents will not improve the level of control. Additional agents are required to improve the biocontrol in the temperate conditions, and also to increase damage in the sub-tropical areas where most of the agents are established and where the weed retains its leaves year round. New candidate agents that possess biological attributes that favour a high intrinsic rate of increase, a high impact per individual and that improve the synchrony between the weed and the agent in climatic conditions that promote the seasonal leaflessness of plants should receive prior consideration. A survey in Jamaica indicated that additional biological control agents are available in the region of origin but that care should be taken to prioritise the most effective agents. The various selection systems currently available in weed biocontrol produce contradictory results in the priority assigned to candidate agents and a new selection system is proposed. The biology and host range of two new candidate natural enemies, the leaf-galling weevil, Coelocephalapion camarae and the leaf-sucking mirid, Falconia intermedia were investigated for the biocontrol of lantana. The studies indicated that these have considerable biocontrol potential, in that the weevil has a wide climatic tolerance and has the potential to survive the host leaflessness typical of temperate conditions, while the mirid has a high intrinsic rate of increase, and the potential for several generations a year. Both agents caused a high level of damage to the leaves, with the weevil galling the vascular tissue in the leaf-petiole and the mirid causing chlorotic speckling of the leaves. During laboratory trials both agents accepted indigenous species in the genus Lippia. However, under multiple choice conditions these agents showed a significant and strong oviposition preference for lantana. A risk assessment and post release field trials indicated that F. intermedia is likely to attack some Lippia species in the presence of lantana, but the levels of damage are predicted to be relatively low. A possible low incidence of damage to indigenous species was considered a justifiable ‘trade-off’ for the potentially marked impact on L. camara. Preference and performance studies on the two candidate agents suggested that most of the South African lantana varieties are suitable host plants. The mirid preferred certain varieties in multiple choice experiments, but this is unlikely to affect its impact under field conditions. Permission for release was accordingly sought for both species. Finally, the challenges facing the biological control programme and the potential for improving the control of L. camara in South Africa are considered.
- Full Text:
- Date Issued: 2003
Biology and demography of the spotted grunter Pomadasys commersonnii (Haemulidae) in South African waters
- Authors: Webb, Garth Anthony
- Date: 2003
- Subjects: Grunts (Fishes) -- South Africa , Grunts (Fishes) -- South Africa -- Ecology
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5201 , http://hdl.handle.net/10962/d1003727 , Grunts (Fishes) -- South Africa , Grunts (Fishes) -- South Africa -- Ecology
- Description: The spotted grunter, Pomadasys commersonnii (Haemulidae), is an Indian Ocean coastal species, extending from India to False Bay but is absent from the central Indian Ocean islands. Its taste and texture has made it one of the most important line fish species and is caught by recreational and subsistence fisherman along the entire east coast of South Africa. Because of its inshore distribution, reduced catch rates and estuarine dependence the species was de-commercialised in 1992. Since then it has been investigated as a candidate species for mariculture. All previous work on the biology of the species was undertaken on fish collected in KwaZulu-Natal in the mid 1970's. All other information has been incidental and formed part of other ecological studies. All management plans for this species have been based on these data. To develop a more comprehensive management plan that incorporates the entire population of spotted grunter, it was deemed necessary to reassess the biology (including feeding biology, age and growth and reproductive biology) as well as the demography of the population throughout its distributional range in South African waters. Analysis of the diet of spotted grunter, collected in estuaries, indicates that crustaceans form the bulk of the prey selected. Amphipods, mysids and estuarine brachyura predominate the diet of fish < 300 mm TL. At 200 mm TL fish start to prey on anomurans, which are extracted from their burrows using the 'blowing' feeding mechanism. Anomurans, in particular Upogebia africana and Callianassa krausii, become the preferred prey of fish larger than 300 mm TL. The high degree of diet flexibility that spotted grunter exhibit means that the composition and abundance of the macrobenthos of a particular environment will dictate the diet of the species. Otolith growth zones were found to be deposited annually with the opaque zones being deposited during the austral summer (November - February). The optical definition of annual otolith growth rings differed significantly between geographic regions (namely: Western Cape, South Eastern Cape and KwaZulu-Natal). Growth (sex combined) offish in the Western Cape were best described by the specialised 3 parameter Von Bertalanffy with a relative error structure in the form : Lt = 753(1- e⁻°·¹⁵⁴ ⁽t +¹·⁶¹⁵⁾) while growth in the South Eastern Cape was best described by using the Schnute model with an absolute error structure in the form: Lt=177°·⁴¹⁶ + (676.2⁻¹·²⁶⁶ - 169.2⁻¹²⁶⁶)[1-e°·⁴¹⁶⁽t-t₁⁾ / 1-e°·⁴¹⁶⁽t₂-t₁⁾]¹/¹·²⁶⁶ whereas growth was best described in KwaZulu-Natal using the specialised 3 parameter Von Bertalanffy with a relative error structure in the form: Lt = 839(1-e°·¹⁷⁽t⁺°·⁴⁹⁾) In the South Eastern Cape, length at 50% maturity was found to be 305 mm TL for males. Since females with ripe & running or spent gonads were not found in the South Eastern Cape and since histological evidence suggests that females in the South Eastern Cape have spawned, it appears that spawning does not occur in the South Eastern Cape. These results suggest that adults are resident in the estuaries of the Western and South Eastern Cape and undertake the spring/summer, northward spawning migration to KwaZulu-Natal. After joining the resident spawner stock in KwaZulu-Natal and spawning in the offshore environment of KwaZulu-Natal, adults soon return to the southern regions of their distributional range. Juveniles recruit into KwaZulu-Natal estuaries at a length of 25 - 35 mm TL. A proportion of the eggs and larvae are transported southwards along the periphery of the western boundary Agulhas Current where juveniles (25 - 30 mm TL) recruit into the estuaries as far south as the Swartvlei estuary in the Western Cape. There is evidence to suggest that the fish, which occur in the Western Cape estuaries, have migrated there once they have attained sexual maturity further east.
- Full Text:
- Date Issued: 2003
- Authors: Webb, Garth Anthony
- Date: 2003
- Subjects: Grunts (Fishes) -- South Africa , Grunts (Fishes) -- South Africa -- Ecology
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5201 , http://hdl.handle.net/10962/d1003727 , Grunts (Fishes) -- South Africa , Grunts (Fishes) -- South Africa -- Ecology
- Description: The spotted grunter, Pomadasys commersonnii (Haemulidae), is an Indian Ocean coastal species, extending from India to False Bay but is absent from the central Indian Ocean islands. Its taste and texture has made it one of the most important line fish species and is caught by recreational and subsistence fisherman along the entire east coast of South Africa. Because of its inshore distribution, reduced catch rates and estuarine dependence the species was de-commercialised in 1992. Since then it has been investigated as a candidate species for mariculture. All previous work on the biology of the species was undertaken on fish collected in KwaZulu-Natal in the mid 1970's. All other information has been incidental and formed part of other ecological studies. All management plans for this species have been based on these data. To develop a more comprehensive management plan that incorporates the entire population of spotted grunter, it was deemed necessary to reassess the biology (including feeding biology, age and growth and reproductive biology) as well as the demography of the population throughout its distributional range in South African waters. Analysis of the diet of spotted grunter, collected in estuaries, indicates that crustaceans form the bulk of the prey selected. Amphipods, mysids and estuarine brachyura predominate the diet of fish < 300 mm TL. At 200 mm TL fish start to prey on anomurans, which are extracted from their burrows using the 'blowing' feeding mechanism. Anomurans, in particular Upogebia africana and Callianassa krausii, become the preferred prey of fish larger than 300 mm TL. The high degree of diet flexibility that spotted grunter exhibit means that the composition and abundance of the macrobenthos of a particular environment will dictate the diet of the species. Otolith growth zones were found to be deposited annually with the opaque zones being deposited during the austral summer (November - February). The optical definition of annual otolith growth rings differed significantly between geographic regions (namely: Western Cape, South Eastern Cape and KwaZulu-Natal). Growth (sex combined) offish in the Western Cape were best described by the specialised 3 parameter Von Bertalanffy with a relative error structure in the form : Lt = 753(1- e⁻°·¹⁵⁴ ⁽t +¹·⁶¹⁵⁾) while growth in the South Eastern Cape was best described by using the Schnute model with an absolute error structure in the form: Lt=177°·⁴¹⁶ + (676.2⁻¹·²⁶⁶ - 169.2⁻¹²⁶⁶)[1-e°·⁴¹⁶⁽t-t₁⁾ / 1-e°·⁴¹⁶⁽t₂-t₁⁾]¹/¹·²⁶⁶ whereas growth was best described in KwaZulu-Natal using the specialised 3 parameter Von Bertalanffy with a relative error structure in the form: Lt = 839(1-e°·¹⁷⁽t⁺°·⁴⁹⁾) In the South Eastern Cape, length at 50% maturity was found to be 305 mm TL for males. Since females with ripe & running or spent gonads were not found in the South Eastern Cape and since histological evidence suggests that females in the South Eastern Cape have spawned, it appears that spawning does not occur in the South Eastern Cape. These results suggest that adults are resident in the estuaries of the Western and South Eastern Cape and undertake the spring/summer, northward spawning migration to KwaZulu-Natal. After joining the resident spawner stock in KwaZulu-Natal and spawning in the offshore environment of KwaZulu-Natal, adults soon return to the southern regions of their distributional range. Juveniles recruit into KwaZulu-Natal estuaries at a length of 25 - 35 mm TL. A proportion of the eggs and larvae are transported southwards along the periphery of the western boundary Agulhas Current where juveniles (25 - 30 mm TL) recruit into the estuaries as far south as the Swartvlei estuary in the Western Cape. There is evidence to suggest that the fish, which occur in the Western Cape estuaries, have migrated there once they have attained sexual maturity further east.
- Full Text:
- Date Issued: 2003