Towards the development of species-specific fish production models for small reservoirs in Southern Africa
- Authors: Potts, Warren M
- Date: 2004
- Subjects: Freshwater fishes -- Africa, Southern Fish populations -- Africa, Southern Fisheries -- Africa, Southern Sustainable fisheries -- Africa, Southern Labeo -- Reproduction Cyprinidae -- Africa, Southern
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5330 , http://hdl.handle.net/10962/d1005176
- Description: The fish populations in small southern African reservoirs are largely unexploited and there is potential for fisheries development. However, the development of sustainable fisheries requires reliable estimates of potential yield or production. Empirical models that have been developed to predict fish production only apply to large water bodies and only predict total fish production, not the production of individual species. Small reservoirs generally have few commercially important species and therefore species-specific fish production models are an alternative approach. The small reservoirs of the Eastern Cape are dominated by the moggel (Labeo umbratus). The principal objectives of this thesis were to gain an understanding of the ecology of small reservoirs and the function of moggel in these systems. This information was used to design a research approach to rapidly develop species-specific models for small reservoirs in southern Africa. The limnology of two small reservoirs was compared. During the study period the reservoirs were turbid and showed a warm, monomictic pattern of thermal stratification. Anthropogenic pressure in the reservoir catchments appeared to be the overriding factor increasing the nutrient input to the reservoirs and consequently, influencing the biomass of algae in the reservoirs. The feeding biology of moggel in Katriver and Laing reservoirs was examined. Moggel are detrivorous and successfully digested diatoms. The slower growth rate of moggel in Katriver reservoir was attributed to the poorer nutritional value of the diet as a consequence of the lower concentration of diatoms in the detrital aggregate. The reproductive characteristics of moggel were examined in four reservoirs. Moggel were able to reproduce successfully in the reservoirs. This could be attributed to their r-selected reproductive strategy, with a high fecundity and an extended spawning season and their ability to spawn in a floodplain environment. Differences in recruitment success between years were found to be a consequence of the timing and duration of seasonal rains. The number of mature females in a population and the availability of suitable spawning habitat influenced recruitment success. The life history of the moggel in five reservoirs was compared. Growth appeared to be related to food availability, while mortality was lower in the populations where food was abundant and there were less predatory species. Size and age at maturity were not affected by environmental factors, but were dependent on growth and mortality. Three contrasting methods were used to estimate moggel gillnet selectivity. The Sechin, direct fyke net method and length-structured model all yielded similar results and correction factors obtained from the selectivity study were applied to the gillnet data to estimate the fish population size and structure in each reservoir. Using information from the life history and selectivity studies, the biomass and production of five moggel populations was estimated and related to abiotic and biotic factors in the reservoirs and their catchments. Moggel biomass and production was dependent on the biomass of algae, which was dependent on morphoedaphic characteristics of the reservoirs. Small, shallow reservoirs with a reasonable amount of human habitation in their catchments would sustain the highest algal biomass and provided they had adequate spawning habitat would also have the highest moggel biomass and production. The future research requirements for small reservoir fisheries are outlined and include a three-year program to develop a species-specific production model for any of the dominant species.
- Full Text:
- Date Issued: 2004
- Authors: Potts, Warren M
- Date: 2004
- Subjects: Freshwater fishes -- Africa, Southern Fish populations -- Africa, Southern Fisheries -- Africa, Southern Sustainable fisheries -- Africa, Southern Labeo -- Reproduction Cyprinidae -- Africa, Southern
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5330 , http://hdl.handle.net/10962/d1005176
- Description: The fish populations in small southern African reservoirs are largely unexploited and there is potential for fisheries development. However, the development of sustainable fisheries requires reliable estimates of potential yield or production. Empirical models that have been developed to predict fish production only apply to large water bodies and only predict total fish production, not the production of individual species. Small reservoirs generally have few commercially important species and therefore species-specific fish production models are an alternative approach. The small reservoirs of the Eastern Cape are dominated by the moggel (Labeo umbratus). The principal objectives of this thesis were to gain an understanding of the ecology of small reservoirs and the function of moggel in these systems. This information was used to design a research approach to rapidly develop species-specific models for small reservoirs in southern Africa. The limnology of two small reservoirs was compared. During the study period the reservoirs were turbid and showed a warm, monomictic pattern of thermal stratification. Anthropogenic pressure in the reservoir catchments appeared to be the overriding factor increasing the nutrient input to the reservoirs and consequently, influencing the biomass of algae in the reservoirs. The feeding biology of moggel in Katriver and Laing reservoirs was examined. Moggel are detrivorous and successfully digested diatoms. The slower growth rate of moggel in Katriver reservoir was attributed to the poorer nutritional value of the diet as a consequence of the lower concentration of diatoms in the detrital aggregate. The reproductive characteristics of moggel were examined in four reservoirs. Moggel were able to reproduce successfully in the reservoirs. This could be attributed to their r-selected reproductive strategy, with a high fecundity and an extended spawning season and their ability to spawn in a floodplain environment. Differences in recruitment success between years were found to be a consequence of the timing and duration of seasonal rains. The number of mature females in a population and the availability of suitable spawning habitat influenced recruitment success. The life history of the moggel in five reservoirs was compared. Growth appeared to be related to food availability, while mortality was lower in the populations where food was abundant and there were less predatory species. Size and age at maturity were not affected by environmental factors, but were dependent on growth and mortality. Three contrasting methods were used to estimate moggel gillnet selectivity. The Sechin, direct fyke net method and length-structured model all yielded similar results and correction factors obtained from the selectivity study were applied to the gillnet data to estimate the fish population size and structure in each reservoir. Using information from the life history and selectivity studies, the biomass and production of five moggel populations was estimated and related to abiotic and biotic factors in the reservoirs and their catchments. Moggel biomass and production was dependent on the biomass of algae, which was dependent on morphoedaphic characteristics of the reservoirs. Small, shallow reservoirs with a reasonable amount of human habitation in their catchments would sustain the highest algal biomass and provided they had adequate spawning habitat would also have the highest moggel biomass and production. The future research requirements for small reservoir fisheries are outlined and include a three-year program to develop a species-specific production model for any of the dominant species.
- Full Text:
- Date Issued: 2004
Variability in and coupling of larval availability and settlement of the mussel Perna perna : a spatio-temporal approach
- Authors: Porri, Francesca
- Date: 2004
- Subjects: Mussels -- South Africa Perna -- South Africa Perna -- Spawning Perna -- Larvae
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5796 , http://hdl.handle.net/10962/d1005484
- Description: Population dynamics of many intertidal organisms are highly influenced by the abundance and distribution of planktonic larvae in the water column and their arrival on the shore. The brown mussel, Perna perna was used to investigate two of the primary processes that affect population size and dynamics, larval availability and settlement, on the south coast of South Africa. Perna perna is a dominant species on rocky shores of the southern and eastern coasts of South Africa. It creates three-dimensional beds that provide habitats for many other species and hence promotes biodiversity. Larval availability and settlement were examined at different spatial and temporal scales using a nested experimental design. To detect possible relationships between larval availability and settlement, the studies were simultaneous. Two sites, 4km apart, were chosen to investigate mussel settlement patterns. Within each site, three locations (300m from each other) were selected. At each location, five artificial settler collectors were placed at approximately 20cm intervals. Collectors were replaced at a range of time intervals, from daily to seasonal, for 16 months. Each intertidal location was paired with an offshore station, 500m from the shore, where larval availability was measured. At each offshore station, three vertical hauls were collected twice a month using a plankton net. Plankton sampling lasted for 14 months and was designed to examine variability on three temporal scales: seasonal, lunar and daily. The results showed no correlation between the distribution of larvae in the water and settlers on the shore. While larvae were abundant in the water at the start of sampling, they became very rare throughout the rest of the study at both sites and all locations. In contrast, distinct peaks of settler abundance were observed during the seasonal settlement study. In addition to the expected, strong temporal variation that emerged from both studies at all time scales, spatial patterns of variability were also observed. While no spatial effect was detected for the larvae in the water column, there was distinct spatial variation in settlement at the location level: some locations always showed higher settlement than others. These results suggest that, on scales of hundreds of meters to kilometers, larval availability and settlement are very unpredictable in time and that differential delivery of larvae occurs from nearshore waters to the shore. Although the effect of the state of the moon (new or full) was not significant in either study, more settlers seemed to arrive on the shore during new moon. Wind direction did not correlate significantly with settlement. However, the dropping of offshore winds and the prevalence of onshore winds, which are characteristic of summer, may be linked to the start of settlement. Nevertheless, further investigations on tidal or lunar cycles and on the influence of wind on surface currents are required to clarify the effects of moon and wind on settlement.
- Full Text:
- Date Issued: 2004
- Authors: Porri, Francesca
- Date: 2004
- Subjects: Mussels -- South Africa Perna -- South Africa Perna -- Spawning Perna -- Larvae
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5796 , http://hdl.handle.net/10962/d1005484
- Description: Population dynamics of many intertidal organisms are highly influenced by the abundance and distribution of planktonic larvae in the water column and their arrival on the shore. The brown mussel, Perna perna was used to investigate two of the primary processes that affect population size and dynamics, larval availability and settlement, on the south coast of South Africa. Perna perna is a dominant species on rocky shores of the southern and eastern coasts of South Africa. It creates three-dimensional beds that provide habitats for many other species and hence promotes biodiversity. Larval availability and settlement were examined at different spatial and temporal scales using a nested experimental design. To detect possible relationships between larval availability and settlement, the studies were simultaneous. Two sites, 4km apart, were chosen to investigate mussel settlement patterns. Within each site, three locations (300m from each other) were selected. At each location, five artificial settler collectors were placed at approximately 20cm intervals. Collectors were replaced at a range of time intervals, from daily to seasonal, for 16 months. Each intertidal location was paired with an offshore station, 500m from the shore, where larval availability was measured. At each offshore station, three vertical hauls were collected twice a month using a plankton net. Plankton sampling lasted for 14 months and was designed to examine variability on three temporal scales: seasonal, lunar and daily. The results showed no correlation between the distribution of larvae in the water and settlers on the shore. While larvae were abundant in the water at the start of sampling, they became very rare throughout the rest of the study at both sites and all locations. In contrast, distinct peaks of settler abundance were observed during the seasonal settlement study. In addition to the expected, strong temporal variation that emerged from both studies at all time scales, spatial patterns of variability were also observed. While no spatial effect was detected for the larvae in the water column, there was distinct spatial variation in settlement at the location level: some locations always showed higher settlement than others. These results suggest that, on scales of hundreds of meters to kilometers, larval availability and settlement are very unpredictable in time and that differential delivery of larvae occurs from nearshore waters to the shore. Although the effect of the state of the moon (new or full) was not significant in either study, more settlers seemed to arrive on the shore during new moon. Wind direction did not correlate significantly with settlement. However, the dropping of offshore winds and the prevalence of onshore winds, which are characteristic of summer, may be linked to the start of settlement. Nevertheless, further investigations on tidal or lunar cycles and on the influence of wind on surface currents are required to clarify the effects of moon and wind on settlement.
- Full Text:
- Date Issued: 2004
A corpus-based investigation of Xhosa English in the classroom setting
- Authors: Platt, Candice Lee
- Date: 2004 , 2013-06-03
- Subjects: English language -- Study and teaching (Foreign speakers) -- South Africa , Computational linguistics , Black English -- South Africa , Black people -- South Africa -- Eastern Cape -- Education
- Language: English
- Type: Thesis , Masters , MA
- Identifier: vital:2379 , http://hdl.handle.net/10962/d1007613 , English language -- Study and teaching (Foreign speakers) -- South Africa , Computational linguistics , Black English -- South Africa , Black people -- South Africa -- Eastern Cape -- Education
- Description: This study is an investigation of Xhosa English as used by teachers in the Grahamstown area of the Eastern Cape. The aims of the study were firstly, to compile a 20 000 word mini-corpus of the spoken English of Xhosa mother-tongue teachers in Grahamstown, and to use this data to describe the characteristics of Xhosa English used in the classroom context; and secondly, to assess the usefulness of a corpus-based approach to a study of this nature. The English of five Xhosa mother-tongue teachers was investigated. These teachers were recorded while teaching in English and the data was then transcribed for analysis. The data was analysed using Wordsmith Tools to investigate patterns in the teachers' language. Grammatical, lexical and discourse patterns were explored based on the findings of other researchers' investigations of Black South African English and Xhosa English. In general, many of the patterns reported in the literature were found in the data, but to a lesser extent than reported in literature which gave quantitative information. Some features not described elsewhere were also found. The corpus-based approach was found to be useful within the limits of pattern-matching. , KMBT_363 , Adobe Acrobat 9.54 Paper Capture Plug-in
- Full Text:
- Date Issued: 2004
- Authors: Platt, Candice Lee
- Date: 2004 , 2013-06-03
- Subjects: English language -- Study and teaching (Foreign speakers) -- South Africa , Computational linguistics , Black English -- South Africa , Black people -- South Africa -- Eastern Cape -- Education
- Language: English
- Type: Thesis , Masters , MA
- Identifier: vital:2379 , http://hdl.handle.net/10962/d1007613 , English language -- Study and teaching (Foreign speakers) -- South Africa , Computational linguistics , Black English -- South Africa , Black people -- South Africa -- Eastern Cape -- Education
- Description: This study is an investigation of Xhosa English as used by teachers in the Grahamstown area of the Eastern Cape. The aims of the study were firstly, to compile a 20 000 word mini-corpus of the spoken English of Xhosa mother-tongue teachers in Grahamstown, and to use this data to describe the characteristics of Xhosa English used in the classroom context; and secondly, to assess the usefulness of a corpus-based approach to a study of this nature. The English of five Xhosa mother-tongue teachers was investigated. These teachers were recorded while teaching in English and the data was then transcribed for analysis. The data was analysed using Wordsmith Tools to investigate patterns in the teachers' language. Grammatical, lexical and discourse patterns were explored based on the findings of other researchers' investigations of Black South African English and Xhosa English. In general, many of the patterns reported in the literature were found in the data, but to a lesser extent than reported in literature which gave quantitative information. Some features not described elsewhere were also found. The corpus-based approach was found to be useful within the limits of pattern-matching. , KMBT_363 , Adobe Acrobat 9.54 Paper Capture Plug-in
- Full Text:
- Date Issued: 2004
An assessment of the potential use of excess warehousing space of Spoornet property management to support the industrial development zones in the Eastern Cape region
- Authors: Pitout, Evert Philippus
- Date: 2004
- Subjects: Warehouses -- Management , Warehouses -- South Africa -- Eastern Cape , Industrial floor space -- South Africa -- Eastern Cape , Industrial development projects -- South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Masters , MBA
- Identifier: vital:10922 , http://hdl.handle.net/10948/149 , Warehouses -- Management , Warehouses -- South Africa -- Eastern Cape , Industrial floor space -- South Africa -- Eastern Cape , Industrial development projects -- South Africa -- Eastern Cape
- Description: The research problem addressed in this study was to analyse and report on the potential use of Spoornet’s excess warehousing to support the Industrial Development Zones (IDZs) in the Eastern Cape. In order to achieve this objective, a literature study was undertaken to ascertain the world-class practices for warehousing. A study was conducted on Spoornet strategy in order to determine whether the company can apply its existing strategy for warehouse operations. The empirical results obtained, indicated that there would be a need for warehousing to support the IDZs in the Eastern Cape. There would be opportunities for storage of raw materials, distribution of parts for production, and finished goods to be delivered to consumers. Spoornet has gained ground on its competitor with respect to logistics and has progressed with its “Freight Logistics Solution” initiative. In conclusion it was recommended that Spoornet uses its existing strategy and convert their goods sheds into world-class warehousing. The warehouse space can be used as a trade-off to gain rail clients.
- Full Text:
- Date Issued: 2004
- Authors: Pitout, Evert Philippus
- Date: 2004
- Subjects: Warehouses -- Management , Warehouses -- South Africa -- Eastern Cape , Industrial floor space -- South Africa -- Eastern Cape , Industrial development projects -- South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Masters , MBA
- Identifier: vital:10922 , http://hdl.handle.net/10948/149 , Warehouses -- Management , Warehouses -- South Africa -- Eastern Cape , Industrial floor space -- South Africa -- Eastern Cape , Industrial development projects -- South Africa -- Eastern Cape
- Description: The research problem addressed in this study was to analyse and report on the potential use of Spoornet’s excess warehousing to support the Industrial Development Zones (IDZs) in the Eastern Cape. In order to achieve this objective, a literature study was undertaken to ascertain the world-class practices for warehousing. A study was conducted on Spoornet strategy in order to determine whether the company can apply its existing strategy for warehouse operations. The empirical results obtained, indicated that there would be a need for warehousing to support the IDZs in the Eastern Cape. There would be opportunities for storage of raw materials, distribution of parts for production, and finished goods to be delivered to consumers. Spoornet has gained ground on its competitor with respect to logistics and has progressed with its “Freight Logistics Solution” initiative. In conclusion it was recommended that Spoornet uses its existing strategy and convert their goods sheds into world-class warehousing. The warehouse space can be used as a trade-off to gain rail clients.
- Full Text:
- Date Issued: 2004
Apartheid South Africa's foreign relations with African states, 1961-1994
- Authors: Pfister, Roger
- Date: 2004
- Subjects: Apartheid -- South Africa -- History -- 20th century Government, Resistance to -- South Africa Democracy -- South Africa South Africa -- Politics and government -- 20th century South Africa -- History -- 1961-1994 South Africa -- Foreign relations -- Africa
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:2863 , http://hdl.handle.net/10962/d1007632
- Description: This thesis examines South Africa's foreign relations, viewed from a South African perspective, with the black African countries beyond southern Africa from 1961 to 1994. These relations were determined by the conflict between Pretoria's apartheid ideology on the one hand, and African continental rejection of South Africa's race discrimination policies and its exclusion from the community of African states on the other. The documentary material used primarily stems from the Department of Foreign Affairs archive in Pretoria, supplemented by research conducted in other archives. Furthermore, we conducted interviews and correspondence, and consulted the relevant primary and secondary literature. Given the main source of information, we chose to make this work a case study in Diplomatic History. In consequence, and constituting the core of the study, Chapters 3 to 6 explore the interaction between South Africa and the black African states in a chronological order. At the same time, we draw on the analytical concepts from the academic disciplines of Political Science and its derivative, International Relations, to comprehend developments more fully. We discuss the significance of the approaches from these two disciplines in both the Introduction and Chapter 2. In particular, we emphasise that this study is about Pretoria's foreign policy, involving state and non-state actors, and we suggest that the unequal status between South Africa and the other African states constitutes an inherent factor in the relationship between them. The Conclusion examines the role of the state and non-state actors in determining Pretoria's foreign relations and the relevance of the structural imbalance between South Africa and the black African states in this context.
- Full Text:
- Date Issued: 2004
- Authors: Pfister, Roger
- Date: 2004
- Subjects: Apartheid -- South Africa -- History -- 20th century Government, Resistance to -- South Africa Democracy -- South Africa South Africa -- Politics and government -- 20th century South Africa -- History -- 1961-1994 South Africa -- Foreign relations -- Africa
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:2863 , http://hdl.handle.net/10962/d1007632
- Description: This thesis examines South Africa's foreign relations, viewed from a South African perspective, with the black African countries beyond southern Africa from 1961 to 1994. These relations were determined by the conflict between Pretoria's apartheid ideology on the one hand, and African continental rejection of South Africa's race discrimination policies and its exclusion from the community of African states on the other. The documentary material used primarily stems from the Department of Foreign Affairs archive in Pretoria, supplemented by research conducted in other archives. Furthermore, we conducted interviews and correspondence, and consulted the relevant primary and secondary literature. Given the main source of information, we chose to make this work a case study in Diplomatic History. In consequence, and constituting the core of the study, Chapters 3 to 6 explore the interaction between South Africa and the black African states in a chronological order. At the same time, we draw on the analytical concepts from the academic disciplines of Political Science and its derivative, International Relations, to comprehend developments more fully. We discuss the significance of the approaches from these two disciplines in both the Introduction and Chapter 2. In particular, we emphasise that this study is about Pretoria's foreign policy, involving state and non-state actors, and we suggest that the unequal status between South Africa and the other African states constitutes an inherent factor in the relationship between them. The Conclusion examines the role of the state and non-state actors in determining Pretoria's foreign relations and the relevance of the structural imbalance between South Africa and the black African states in this context.
- Full Text:
- Date Issued: 2004
Pollination biology of Bergeranthus multiceps (Aizoaceae) with preliminary observations of repeated flower opening and closure
- Peter, Craig I, Dold, Anthony P, Barker, Nigel P, Ripley, Bradley S
- Authors: Peter, Craig I , Dold, Anthony P , Barker, Nigel P , Ripley, Bradley S
- Date: 2004
- Language: English
- Type: Article
- Identifier: vital:6529 , http://hdl.handle.net/10962/d1005970
- Description: Little is known about pollination of the Aizoaceae (Mesembryanthemaceae). There are sparse reports of generalist pollination in the family by a variety of insects (predominantly bees). Furthermore, most species are self-incompatible in cultivation. In this study, observations were made on two populations of Bergeranthus multiceps (Salm-Dyck) Schwantes growing in the Eastern Cape province of South Africa. Insects visiting the flowers were collected and examined for pollen. While 79 individual insects (in 24 genera representing 14 families and four orders) were collected visiting the flowers, the majority (43 individuals) were female Allodapula variegata bees (Apidae, subfamily Xylocopinae, tribe Allodapini)collecting pollen. All other bee visitors were also female, suggesting pollen collection as the primary activity at the flowers. The protandrous flowers were found to be self-incompatible, pointing to the importance of bee-mediated xenogamy in this species. The flowers of B. multiceps are bright yellow in the human visual spectrum. In addition, the petals of this species reflect ultraviolet light. In contrast, the yellow anthers absorb UV. Flower opening and closing is common in the Aizoaceae. Interestingly, in B. multiceps flowers open at about 15:30 and remain open for approximately three hours before closing again in the late afternoon. These afternoon flower opening events were found to be closely correlated to ambient temperatures above 23°C, relative humidity lower than 50% and vapour pressure deficit below 1.05 kPa measured from as early as 09:00 on the days when flowers opened.
- Full Text:
- Date Issued: 2004
- Authors: Peter, Craig I , Dold, Anthony P , Barker, Nigel P , Ripley, Bradley S
- Date: 2004
- Language: English
- Type: Article
- Identifier: vital:6529 , http://hdl.handle.net/10962/d1005970
- Description: Little is known about pollination of the Aizoaceae (Mesembryanthemaceae). There are sparse reports of generalist pollination in the family by a variety of insects (predominantly bees). Furthermore, most species are self-incompatible in cultivation. In this study, observations were made on two populations of Bergeranthus multiceps (Salm-Dyck) Schwantes growing in the Eastern Cape province of South Africa. Insects visiting the flowers were collected and examined for pollen. While 79 individual insects (in 24 genera representing 14 families and four orders) were collected visiting the flowers, the majority (43 individuals) were female Allodapula variegata bees (Apidae, subfamily Xylocopinae, tribe Allodapini)collecting pollen. All other bee visitors were also female, suggesting pollen collection as the primary activity at the flowers. The protandrous flowers were found to be self-incompatible, pointing to the importance of bee-mediated xenogamy in this species. The flowers of B. multiceps are bright yellow in the human visual spectrum. In addition, the petals of this species reflect ultraviolet light. In contrast, the yellow anthers absorb UV. Flower opening and closing is common in the Aizoaceae. Interestingly, in B. multiceps flowers open at about 15:30 and remain open for approximately three hours before closing again in the late afternoon. These afternoon flower opening events were found to be closely correlated to ambient temperatures above 23°C, relative humidity lower than 50% and vapour pressure deficit below 1.05 kPa measured from as early as 09:00 on the days when flowers opened.
- Full Text:
- Date Issued: 2004
"My novel, Hill of Fools"
- Peteni, R L, Wright, Laurence
- Authors: Peteni, R L , Wright, Laurence
- Date: 2004
- Language: English
- Type: text , article
- Identifier: vital:7038 , http://hdl.handle.net/10962/d1007376 , http://hdl.handle.net/10520/EJC47869
- Description: preprint , R.L. Peteni - 'There is a tendency in human beings to pay no heed to events in small remote areas. They would rather concern themselves only with those events which make headlines, with political upheavals and industrial conflicts centred in large metropolitan regions. Yet there is always drama and human conflict in the humblest rural village. In selecting a pastoral theme and small fictitious villages in an obscure corner of Keiskammahoek as the setting of the novel, I had an ironic intention. Themes illustrated in these obscure villages would, I believed, have more universal application than they would if I had selected a larger centre, identifiable personages and known political trends. I did not want anybody to sit back, complacent, feeling that the spotlight was on Lennox Sebe’s Ciskei alone, or Kaiser Matanzima’s Transkei, or John Vorster’s apartheid South Africa. The spotlight is on the Ciskei, yes, on Transkei, on South Africa, on any other country where public life and personal relationships are bedevilled by tribalism or racialism or any form of sectionalism.
- Full Text:
- Date Issued: 2004
- Authors: Peteni, R L , Wright, Laurence
- Date: 2004
- Language: English
- Type: text , article
- Identifier: vital:7038 , http://hdl.handle.net/10962/d1007376 , http://hdl.handle.net/10520/EJC47869
- Description: preprint , R.L. Peteni - 'There is a tendency in human beings to pay no heed to events in small remote areas. They would rather concern themselves only with those events which make headlines, with political upheavals and industrial conflicts centred in large metropolitan regions. Yet there is always drama and human conflict in the humblest rural village. In selecting a pastoral theme and small fictitious villages in an obscure corner of Keiskammahoek as the setting of the novel, I had an ironic intention. Themes illustrated in these obscure villages would, I believed, have more universal application than they would if I had selected a larger centre, identifiable personages and known political trends. I did not want anybody to sit back, complacent, feeling that the spotlight was on Lennox Sebe’s Ciskei alone, or Kaiser Matanzima’s Transkei, or John Vorster’s apartheid South Africa. The spotlight is on the Ciskei, yes, on Transkei, on South Africa, on any other country where public life and personal relationships are bedevilled by tribalism or racialism or any form of sectionalism.
- Full Text:
- Date Issued: 2004
iLanga: A next generation VOIP-based, TDM-enabled PBX
- Authors: Penton J , Terzoli, Alfredo
- Date: 2004
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/427591 , vital:72449 , https://www.researchgate.net/profile/Alfredo-Terzoli/publication/228963823_iLanga_a_next_generation_VoIP-based_TDM-enabled_PBX/links/02bfe51344c9db1c75000000/iLanga-a-next-generation-VoIP-based-TDM-enabled-PBX.pdf
- Description: iLanga is a complete, cost-effective, computer-based PBX built and be-ing prepared as a commercial product at Rhodes University. Running on a single PC (in its minimal configuration), iLanga provides all the fea-tures of a conventional PBX together with full support for VoIP. In this paper we introduce and discuss iLanga’s architecture, emphasising its main components, Asterisk, SIP Express Router (SER) and OpenH323 Gatekeeper (OpenGK). We also discuss the development of new ser-vices and features in iLanga as well as the possibility to manage and customize it. The paper concludes with the description of a pilot de-ployment of iLanga that we are using to test and refine the system.
- Full Text:
- Date Issued: 2004
- Authors: Penton J , Terzoli, Alfredo
- Date: 2004
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/427591 , vital:72449 , https://www.researchgate.net/profile/Alfredo-Terzoli/publication/228963823_iLanga_a_next_generation_VoIP-based_TDM-enabled_PBX/links/02bfe51344c9db1c75000000/iLanga-a-next-generation-VoIP-based-TDM-enabled-PBX.pdf
- Description: iLanga is a complete, cost-effective, computer-based PBX built and be-ing prepared as a commercial product at Rhodes University. Running on a single PC (in its minimal configuration), iLanga provides all the fea-tures of a conventional PBX together with full support for VoIP. In this paper we introduce and discuss iLanga’s architecture, emphasising its main components, Asterisk, SIP Express Router (SER) and OpenH323 Gatekeeper (OpenGK). We also discuss the development of new ser-vices and features in iLanga as well as the possibility to manage and customize it. The paper concludes with the description of a pilot de-ployment of iLanga that we are using to test and refine the system.
- Full Text:
- Date Issued: 2004
The effect of diet type and feeding rate on growth, morphological development and behaviour of larval and juvenile goldfish Carassius auratus (L.)
- Authors: Paulet, Timothy Guy
- Date: 2004
- Subjects: Goldfish -- Growth , Goldfish -- Nutrition , Goldfish -- Development , Goldfish -- Larvae
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5271 , http://hdl.handle.net/10962/d1005115 , Goldfish -- Growth , Goldfish -- Nutrition , Goldfish -- Development , Goldfish -- Larvae
- Description: Intensive grow-out of goldfish, Carassius auratus (L.), larvae and juveniles in closed recirculating systems requires the control of environmental conditions and feeding. This study investigated the effect of different diets, environmental condition and feeding level on growth, development and survival of goldfish larvae and juveniles. Prey preference for Artemia nauplii or decapsulated Artemia cysts as well as agonistic behaviour was recorded. The micrometer device used to measure mouth-gape was shown to produce accurate measurements which could be used to estimate the maximal particle size that can be ingested by goldfish larvae of a particular age. Goldfish completed metamorphosis earlier with an increased feeding level of Artemia cysts and by making the cysts more accessible to the fish using up-welling water movement. Morphometric plasticity in goldfish larvae was exhibited within two weeks of growth and it may be possible to induce changes in morphology by manipulating diet and rearing environment. Fish that fed on moving prey items had a significantly larger mouth-gape than those that browsed cysts from the tank bottom or dry food items. The development of mouth-gape was not affected by the feeding level of cysts. Condition factor increased with an increase in the number of cysts fed per fish per day. Goldfish larvae and juveniles grew faster and had a higher survival when fed on decapsulated Artemia cysts than on instar I Artemia nauplii or a mixed live/dry diet of Artemia nauplii and dry food. Feeding at least 155 cysts per fish per day, in tanks with upwelling water movement, gave the best growth and survival and the smallest size variation. In addition, cysts remained available to the fish for longer periods, and were easier to prepare and feed. Goldfish larvae preferred decapsulated Artemia cysts to nauplii and rejected fewer prey items as they grew older. The frequency of agonistic behaviour increased as fish grew but no cannibalism was recorded for cyst-fed fish. This study showed that decapsulated Artemia cysts are a good alternative to Artemia nauplii as a diet for larval goldfish. Good growth and high survival was achieved for cyst-fed goldfish larvae and juveniles at 23 ± 1.5°C and at an initial stocking density of 12 fish per litre. This research also contributes to an understanding of feeding behaviour and attempts to minimise under- or over-feeding of Artemia cysts in order to reduce grow-out costs due to the high value of the feed type.
- Full Text:
- Date Issued: 2004
- Authors: Paulet, Timothy Guy
- Date: 2004
- Subjects: Goldfish -- Growth , Goldfish -- Nutrition , Goldfish -- Development , Goldfish -- Larvae
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5271 , http://hdl.handle.net/10962/d1005115 , Goldfish -- Growth , Goldfish -- Nutrition , Goldfish -- Development , Goldfish -- Larvae
- Description: Intensive grow-out of goldfish, Carassius auratus (L.), larvae and juveniles in closed recirculating systems requires the control of environmental conditions and feeding. This study investigated the effect of different diets, environmental condition and feeding level on growth, development and survival of goldfish larvae and juveniles. Prey preference for Artemia nauplii or decapsulated Artemia cysts as well as agonistic behaviour was recorded. The micrometer device used to measure mouth-gape was shown to produce accurate measurements which could be used to estimate the maximal particle size that can be ingested by goldfish larvae of a particular age. Goldfish completed metamorphosis earlier with an increased feeding level of Artemia cysts and by making the cysts more accessible to the fish using up-welling water movement. Morphometric plasticity in goldfish larvae was exhibited within two weeks of growth and it may be possible to induce changes in morphology by manipulating diet and rearing environment. Fish that fed on moving prey items had a significantly larger mouth-gape than those that browsed cysts from the tank bottom or dry food items. The development of mouth-gape was not affected by the feeding level of cysts. Condition factor increased with an increase in the number of cysts fed per fish per day. Goldfish larvae and juveniles grew faster and had a higher survival when fed on decapsulated Artemia cysts than on instar I Artemia nauplii or a mixed live/dry diet of Artemia nauplii and dry food. Feeding at least 155 cysts per fish per day, in tanks with upwelling water movement, gave the best growth and survival and the smallest size variation. In addition, cysts remained available to the fish for longer periods, and were easier to prepare and feed. Goldfish larvae preferred decapsulated Artemia cysts to nauplii and rejected fewer prey items as they grew older. The frequency of agonistic behaviour increased as fish grew but no cannibalism was recorded for cyst-fed fish. This study showed that decapsulated Artemia cysts are a good alternative to Artemia nauplii as a diet for larval goldfish. Good growth and high survival was achieved for cyst-fed goldfish larvae and juveniles at 23 ± 1.5°C and at an initial stocking density of 12 fish per litre. This research also contributes to an understanding of feeding behaviour and attempts to minimise under- or over-feeding of Artemia cysts in order to reduce grow-out costs due to the high value of the feed type.
- Full Text:
- Date Issued: 2004
CREWS : a Component-driven, Run-time Extensible Web Service framework
- Authors: Parry, Dominic Charles
- Date: 2004
- Subjects: Component software -- Development , Computer software -- Reusability , Software reengineering , Web services
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4628 , http://hdl.handle.net/10962/d1006501 , Component software -- Development , Computer software -- Reusability , Software reengineering , Web services
- Description: There has been an increased focus in recent years on the development of re-usable software, in the form of objects and software components. This increase, together with pressures from enterprises conducting transactions on the Web to support all business interactions on all scales, has encouraged research towards the development of easily reconfigurable and highly adaptable Web services. This work investigates the ability of Component-Based Software Development (CBSD) to produce such systems, and proposes a more manageable use of CBSD methodologies. Component-Driven Software Development (CDSD) is introduced to enable better component manageability. Current Web service technologies are also examined to determine their ability to support extensible Web services, and a dynamic Web service architecture is proposed. The work also describes the development of two proof-of-concept systems, DREW Chat and Hamilton Bank. DREW Chat and Hamilton Bank are implementations of Web services that support extension dynamically and at run-time. DREW Chat is implemented on the client side, where the user is given the ability to change the client as required. Hamilton Bank is a server-side implementation, which is run-time customisable by both the user and the party offering the service. In each case, a generic architecture is produced to support dynamic Web services. These architectures are combined to produce CREWS, a Component-driven Runtime Extensible Web Service solution that enables Web services to support the ever changing needs of enterprises. A discussion of similar work is presented, identifying the strengths and weaknesses of our architecture when compared to other solutions.
- Full Text:
- Date Issued: 2004
- Authors: Parry, Dominic Charles
- Date: 2004
- Subjects: Component software -- Development , Computer software -- Reusability , Software reengineering , Web services
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4628 , http://hdl.handle.net/10962/d1006501 , Component software -- Development , Computer software -- Reusability , Software reengineering , Web services
- Description: There has been an increased focus in recent years on the development of re-usable software, in the form of objects and software components. This increase, together with pressures from enterprises conducting transactions on the Web to support all business interactions on all scales, has encouraged research towards the development of easily reconfigurable and highly adaptable Web services. This work investigates the ability of Component-Based Software Development (CBSD) to produce such systems, and proposes a more manageable use of CBSD methodologies. Component-Driven Software Development (CDSD) is introduced to enable better component manageability. Current Web service technologies are also examined to determine their ability to support extensible Web services, and a dynamic Web service architecture is proposed. The work also describes the development of two proof-of-concept systems, DREW Chat and Hamilton Bank. DREW Chat and Hamilton Bank are implementations of Web services that support extension dynamically and at run-time. DREW Chat is implemented on the client side, where the user is given the ability to change the client as required. Hamilton Bank is a server-side implementation, which is run-time customisable by both the user and the party offering the service. In each case, a generic architecture is produced to support dynamic Web services. These architectures are combined to produce CREWS, a Component-driven Runtime Extensible Web Service solution that enables Web services to support the ever changing needs of enterprises. A discussion of similar work is presented, identifying the strengths and weaknesses of our architecture when compared to other solutions.
- Full Text:
- Date Issued: 2004
The feeding biology and potential impact of introduced giraffe (Giraffa camelopardalis) in the Eastern Cape Province, South Africa
- Authors: Parker, Daniel Matthew
- Date: 2004
- Subjects: Giraffe -- South Africa -- Eastern Cape , Animal-plant relationships -- South Africa -- Eastern Cape , Giraffe -- Food -- South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5694 , http://hdl.handle.net/10962/d1005380
- Description: Giraffe (Giraffa camelopardalis) are extralimital (non-native) to the Eastern Cape Province, South Africa yet they have and continue to be introduced to the region. Financial gain has arguably been the driving force behind these introductions as foreign tourists associate giraffe with Africa and the African wildlife experience. This raises a number of ethical, ecological and philosophical questions especially when it is considered that the impact of these browsers on the indigenous vegetation has remained largely unquantified. In this study I assessed the diet and potential impact of three populations of giraffe in the Eastern Cape Province between January 2002 and October 2003. The diet was assessed by both direct observations and faecal analysis. There was no significant difference (P > 0.05) between the results of the two methods of analysis, although direct observations appeared to be a superior method for assessing the diet of giraffe. The diet of giraffe in the Eastern Cape Province was similar to that within their native range with a deciduous species from the genus Acacia (Acacia karroo) being the most important component of the diet. However, giraffe in the Eastern Cape Province consumed more evergreen plant species than those within their native range. The relative lack of deciduous species in the Eastern Cape Province provides a likely explanation for such a result. Seasonal variation in the consumption of the most important species in the diet was evident and this was attributed to the deciduous nature of A. karroo and the seasonal growth of new shoots which were more palatable. The vegetation of the areas most commonly utilised by giraffe at each site was sampled using the point-centred-quarter method and the results related to the frequency of each species in the diet to calculate preference indices. Giraffe preference was strongest for A. karroo and this was attributed to the highly favourable chemical composition of the species. The browse utilisation of giraffe at each site was determined using the twig-length method and intake rates for the three most important species in the diet calculated using a pre-existing regression equation. Male giraffe fed at a higher rate than females. This was probably due to males adopting a “time-minimising” strategy to their feeding in order to allow more time for reproductive pursuits. Giraffe browse utilisation was highest where giraffe density was highest. However, several species were more heavily browsed than others even when giraffe density was low, suggesting that giraffe are capable of negatively affecting the indigenous flora of the province. I conclude that giraffe numbers should be reduced relative to property size in the Eastern Cape Province and that research into the impact of not only giraffe but the combined effects of giraffe and other extralimital herbivores on the indigenous flora and fauna be continued.
- Full Text:
- Date Issued: 2004
- Authors: Parker, Daniel Matthew
- Date: 2004
- Subjects: Giraffe -- South Africa -- Eastern Cape , Animal-plant relationships -- South Africa -- Eastern Cape , Giraffe -- Food -- South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5694 , http://hdl.handle.net/10962/d1005380
- Description: Giraffe (Giraffa camelopardalis) are extralimital (non-native) to the Eastern Cape Province, South Africa yet they have and continue to be introduced to the region. Financial gain has arguably been the driving force behind these introductions as foreign tourists associate giraffe with Africa and the African wildlife experience. This raises a number of ethical, ecological and philosophical questions especially when it is considered that the impact of these browsers on the indigenous vegetation has remained largely unquantified. In this study I assessed the diet and potential impact of three populations of giraffe in the Eastern Cape Province between January 2002 and October 2003. The diet was assessed by both direct observations and faecal analysis. There was no significant difference (P > 0.05) between the results of the two methods of analysis, although direct observations appeared to be a superior method for assessing the diet of giraffe. The diet of giraffe in the Eastern Cape Province was similar to that within their native range with a deciduous species from the genus Acacia (Acacia karroo) being the most important component of the diet. However, giraffe in the Eastern Cape Province consumed more evergreen plant species than those within their native range. The relative lack of deciduous species in the Eastern Cape Province provides a likely explanation for such a result. Seasonal variation in the consumption of the most important species in the diet was evident and this was attributed to the deciduous nature of A. karroo and the seasonal growth of new shoots which were more palatable. The vegetation of the areas most commonly utilised by giraffe at each site was sampled using the point-centred-quarter method and the results related to the frequency of each species in the diet to calculate preference indices. Giraffe preference was strongest for A. karroo and this was attributed to the highly favourable chemical composition of the species. The browse utilisation of giraffe at each site was determined using the twig-length method and intake rates for the three most important species in the diet calculated using a pre-existing regression equation. Male giraffe fed at a higher rate than females. This was probably due to males adopting a “time-minimising” strategy to their feeding in order to allow more time for reproductive pursuits. Giraffe browse utilisation was highest where giraffe density was highest. However, several species were more heavily browsed than others even when giraffe density was low, suggesting that giraffe are capable of negatively affecting the indigenous flora of the province. I conclude that giraffe numbers should be reduced relative to property size in the Eastern Cape Province and that research into the impact of not only giraffe but the combined effects of giraffe and other extralimital herbivores on the indigenous flora and fauna be continued.
- Full Text:
- Date Issued: 2004
An evaluation of "on-line" banking web sites in South Africa to determine essential design criteria
- Authors: Palmer, Lydia
- Date: 2004
- Subjects: Banks and banking -- South Africa Banks and banking -- Customer services -- South Africa Home banking services -- South Africa Electronic funds transfers -- South Africa Web sites -- Design
- Language: English
- Type: Thesis , Masters , MBA
- Identifier: vital:811 , http://hdl.handle.net/10962/d1007667
- Description: The use of the Web to carry out business on the Internet has become a viable option in all business sectors, and Internet banking in South Africa is no exception. The nature of business on the Internet in South Africa and the World is investigated. The extent of Internet banking in South Africa is ascertained and the expectations and perceived problems of online bankers are discussed. The importance of Human Computer Interface and Web Interface Design for successful business is promoted with a discussion of their guidelines and principles. Web Evaluation techniques and Tools are assessed and The "Gartner" Web evaluation tool is selected to evaluate the three bank Web sites. The results of the evaluation indicate that there are several generally well implemented design criteria used by all of the banks while some criteria are not implemented at all. Each bank is discussed individually to identify strong and weak features of their Web site design. Essential aspects of Web design have been proposed for inclusion during the design of "online" Banking Web sites.
- Full Text:
- Date Issued: 2004
- Authors: Palmer, Lydia
- Date: 2004
- Subjects: Banks and banking -- South Africa Banks and banking -- Customer services -- South Africa Home banking services -- South Africa Electronic funds transfers -- South Africa Web sites -- Design
- Language: English
- Type: Thesis , Masters , MBA
- Identifier: vital:811 , http://hdl.handle.net/10962/d1007667
- Description: The use of the Web to carry out business on the Internet has become a viable option in all business sectors, and Internet banking in South Africa is no exception. The nature of business on the Internet in South Africa and the World is investigated. The extent of Internet banking in South Africa is ascertained and the expectations and perceived problems of online bankers are discussed. The importance of Human Computer Interface and Web Interface Design for successful business is promoted with a discussion of their guidelines and principles. Web Evaluation techniques and Tools are assessed and The "Gartner" Web evaluation tool is selected to evaluate the three bank Web sites. The results of the evaluation indicate that there are several generally well implemented design criteria used by all of the banks while some criteria are not implemented at all. Each bank is discussed individually to identify strong and weak features of their Web site design. Essential aspects of Web design have been proposed for inclusion during the design of "online" Banking Web sites.
- Full Text:
- Date Issued: 2004
The development of a toxicity database using freshwater macroinvertebrates, and its application to the protection of South African water resources
- Palmer, Carolyn G, Muller, Wilhelmine J, Gordon, Andrew K, Scherman, Patricia A, Davies-Coleman, Heather D, Pakhomova, L, de Kock, E
- Authors: Palmer, Carolyn G , Muller, Wilhelmine J , Gordon, Andrew K , Scherman, Patricia A , Davies-Coleman, Heather D , Pakhomova, L , de Kock, E
- Date: 2004
- Language: English
- Type: text , Article
- Identifier: vital:7073 , http://hdl.handle.net/10962/d1009528
- Description: There is a growing international trend towards the protection of freshwater resources from pollution by imposing instream guidelines and specified waste-discharge conditions. Current methods for devising freshwater quality guidelines are based on species sensitivity distributions (SSDs) that are used to identify pollutant concentrations, ensuring the protection of a modelled percentage of species (95% protection is a common goal). SSDs are derived from the toxicity test results of as many taxa as possible for each polluting substance. Waste-discharge licences can be for single substances, specified in terms of chemical concentrations, and derived in conjunction with instream guidelines; or for complex mixtures, specified in terms of toxic units. In both cases toxicity test results are the core data used. The emphasis on SSDs calls into question the species constituting the test populations. It is likely that SSDs based in part on the responses of local organisms will achieve superior site-specific ecological protection. Until the early 1990s, there were very few data on the tolerances of South African freshwater organisms. In the intervening decade, the Unilever Centre for Environmental Water Quality at Rhodes University has developed a toxicity database that, to date, records the responses of 21 South African freshwater taxa to 26 single-substance pollutants or mixtures. This is the most comprehensive database of South African toxicity responses available and has been used in the drawing up of methods and guidelines to protect water resources. This paper aims to make these data available and to describe applications of the data using selected case studies.
- Full Text:
- Date Issued: 2004
- Authors: Palmer, Carolyn G , Muller, Wilhelmine J , Gordon, Andrew K , Scherman, Patricia A , Davies-Coleman, Heather D , Pakhomova, L , de Kock, E
- Date: 2004
- Language: English
- Type: text , Article
- Identifier: vital:7073 , http://hdl.handle.net/10962/d1009528
- Description: There is a growing international trend towards the protection of freshwater resources from pollution by imposing instream guidelines and specified waste-discharge conditions. Current methods for devising freshwater quality guidelines are based on species sensitivity distributions (SSDs) that are used to identify pollutant concentrations, ensuring the protection of a modelled percentage of species (95% protection is a common goal). SSDs are derived from the toxicity test results of as many taxa as possible for each polluting substance. Waste-discharge licences can be for single substances, specified in terms of chemical concentrations, and derived in conjunction with instream guidelines; or for complex mixtures, specified in terms of toxic units. In both cases toxicity test results are the core data used. The emphasis on SSDs calls into question the species constituting the test populations. It is likely that SSDs based in part on the responses of local organisms will achieve superior site-specific ecological protection. Until the early 1990s, there were very few data on the tolerances of South African freshwater organisms. In the intervening decade, the Unilever Centre for Environmental Water Quality at Rhodes University has developed a toxicity database that, to date, records the responses of 21 South African freshwater taxa to 26 single-substance pollutants or mixtures. This is the most comprehensive database of South African toxicity responses available and has been used in the drawing up of methods and guidelines to protect water resources. This paper aims to make these data available and to describe applications of the data using selected case studies.
- Full Text:
- Date Issued: 2004
A comparative study of egg development in two species of Siphonariid limpets with contrasting developmental modes
- Authors: Pal, Purba
- Date: 2004
- Subjects: Siphonariidae -- Eggs Siphonariidae -- Spawning Limpets
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5826 , http://hdl.handle.net/10962/d1007663
- Description: The family Siphonariidae is considered primitive amongst the basommatophorans although the ancestry and evolutionary relationships of these marine pulmonates are far from settled. This thesis investigates and compares different aspects of egg development and the female reproductive system in two sympatric species of Siphonaria with different developmental mode (S. capensis, a planktonic developer and S. serrata, a direct developer). The study on the seasonality of gametogenesis and spawning shows that they are both spring/summer spawners with continuous sperm production. The egg production is highest in spring and summer with a brief interruption in winter months. The gametogenic cycle when examinated, reveals that both species are simultaneous hermaphrodites once sexually mature. Amongst various factors that are investigated, density of animals has a positive effect on the number of spawn only during peak spawning. Larger individuals of S. capensis and S. serrata contains more mature oocytes in the gonad indicating that the shell length and fecundity of these two limpets are positively correlated. By contrast, parasitism by trematodes has a drastic effect on the reproductive output of these limpets leaving them completely castrated. Egg development in S. capensis and S. serrata shows that both produce yolk auto synthetically (with the help of organelles like RER, Golgi bodies) but S. serrata also incorporates some high molecular weight precursors via endocytotis. The structure as well as the biochemical composition of the egg ribbons is also different between these two species with higher carbohydrate and protein content of collar shaped spawn of S. serrata. S. capensis produces egg ribbons of less fibrous nature containing thinner egg capsules compared to the direct developer. A comparison of both the glandular complex and spermatheca between these two limpets shows no inter specific difference in the structure although the glandular complex of the siphonariids shows fine structural and histochemical similarities with the albumen gland and membrane gland of the opisthobranchs. The structure of the spermatheca suggests that in both species the organ most possibly receives sperm (for degradation only?) and may transport them via the spermathecal duct (for fertilization?). Finally, it is suggested that S. capensis and S. serrata exhibit primitive features (e.g., an autosynthetic mode of vitellogenesis in S. capensis and a single glandular complex composed of an albumen and a mucous gland) compared to other basommatophorans, which should be considered in future phylogenetic investigations.
- Full Text:
- Date Issued: 2004
- Authors: Pal, Purba
- Date: 2004
- Subjects: Siphonariidae -- Eggs Siphonariidae -- Spawning Limpets
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5826 , http://hdl.handle.net/10962/d1007663
- Description: The family Siphonariidae is considered primitive amongst the basommatophorans although the ancestry and evolutionary relationships of these marine pulmonates are far from settled. This thesis investigates and compares different aspects of egg development and the female reproductive system in two sympatric species of Siphonaria with different developmental mode (S. capensis, a planktonic developer and S. serrata, a direct developer). The study on the seasonality of gametogenesis and spawning shows that they are both spring/summer spawners with continuous sperm production. The egg production is highest in spring and summer with a brief interruption in winter months. The gametogenic cycle when examinated, reveals that both species are simultaneous hermaphrodites once sexually mature. Amongst various factors that are investigated, density of animals has a positive effect on the number of spawn only during peak spawning. Larger individuals of S. capensis and S. serrata contains more mature oocytes in the gonad indicating that the shell length and fecundity of these two limpets are positively correlated. By contrast, parasitism by trematodes has a drastic effect on the reproductive output of these limpets leaving them completely castrated. Egg development in S. capensis and S. serrata shows that both produce yolk auto synthetically (with the help of organelles like RER, Golgi bodies) but S. serrata also incorporates some high molecular weight precursors via endocytotis. The structure as well as the biochemical composition of the egg ribbons is also different between these two species with higher carbohydrate and protein content of collar shaped spawn of S. serrata. S. capensis produces egg ribbons of less fibrous nature containing thinner egg capsules compared to the direct developer. A comparison of both the glandular complex and spermatheca between these two limpets shows no inter specific difference in the structure although the glandular complex of the siphonariids shows fine structural and histochemical similarities with the albumen gland and membrane gland of the opisthobranchs. The structure of the spermatheca suggests that in both species the organ most possibly receives sperm (for degradation only?) and may transport them via the spermathecal duct (for fertilization?). Finally, it is suggested that S. capensis and S. serrata exhibit primitive features (e.g., an autosynthetic mode of vitellogenesis in S. capensis and a single glandular complex composed of an albumen and a mucous gland) compared to other basommatophorans, which should be considered in future phylogenetic investigations.
- Full Text:
- Date Issued: 2004
On the mocvd growth of ZnO
- Authors: Pagni, Olivier Demeno
- Date: 2004
- Subjects: Zinc oxide thin films , Metal organic chemical vapor deposition
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:11075 , http://hdl.handle.net/10948/382 , Zinc oxide thin films , Metal organic chemical vapor deposition
- Description: Zinc oxide (ZnO) is a II-VI semiconductor material that offers tremendous potential as a light emitter in the blue-to-UV range. It has a wurtzite structure, and a direct band gap that can be tuned from 3.0 to 4.0 eV by alloying with Cd or Mg, respectively. In this work, ZnO thin films were grown by metalorganic chemical vapor deposition (MOCVD) on n-Si 2 ° off (100), amorphous glass, n-GaAs (100), and c-plane sapphire substrates. Diethyl zinc (DEZn) and tert-butanol (TBOH) were chosen as precursors. For the first time, Second Harmonic Generation Imaging was applied to the mapping of ZnO epilayers. The images obtained highlighted the polycrystalline character of the thin films, and provided insight as to the growth mode of ZnO on Si. The influence of substrate temperature on the structural properties of the epilayers was investigated by X-ray diffraction and optical microscopy. Grain sizes as high as 54 nm were measured. The optimum temperature range for this system proved to be 450 – 500 °C. The influence of the VI:II ratio during growth on the optical properties of the epilayers was studied by UV-vis-near IR spectroscopy. The lowest Urbach tail E0 parameter was measured for material grown at a VI:II ratio of 18:1. The films’ free electron concentration was shown to decrease by over two orders of magnitude, from 1019 to 1017 cm-3, as the VI:II ratio increased from 10 to 60:1. This decrease in carrier concentration with rising VI:II ratio was paralleled to the surge at 12 K of a photoluminescence (PL) emission band characteristic of p-type ZnO. The band gap energies extracted from room temperature transmission spectra ranged between 3.35 and 3.38 eV, in agreement with the value of 3.35 eV measured by room temperature PL. Moreover, variable temperature PL spectra were recorded between 12 and 298 K on ZnO grown on Si. The 12 K spectrum was dominated by a donor-bound exciton (D°X) at 3.36 eV, while the 298 K scan displayed strong free exciton emission (FX) at 3.29 eV. The width of the D°X band proved to be as narrow as 7 meV. The intensity ratio between the room temperature near-band edge emission and the defect-related green band was as high as 28:1, highlighting the optical quality of the layers deposited in this work. The electrical properties of the thin films were studied by Hall measurements (van der Pauw configuration), and a maximum room temperature mobility of 11 cm2/Vs was recorded. Furthermore, a palladium (Pd) Schottky barrier diode on ZnO was fabricated. The barrier height and ideality factor were calculated from current–voltage measurements to be 0.83 eV and 1.6, respectively. The capacitance–voltage curve of the diode yielded a carrier concentration in the depletion region of 8·1017 cm-3. This study has shown that the optical and electrical properties of ZnO depend strongly on the growth conditions employed. A suitable choice of growth parameters can yield high quality ZnO that may be used for various devices. Keywords: Hall, MOCVD, optical spectroscopy, photoluminescence, Schottky barrier diode, SH Imaging, X-ray diffraction, ZnO.
- Full Text:
- Date Issued: 2004
- Authors: Pagni, Olivier Demeno
- Date: 2004
- Subjects: Zinc oxide thin films , Metal organic chemical vapor deposition
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:11075 , http://hdl.handle.net/10948/382 , Zinc oxide thin films , Metal organic chemical vapor deposition
- Description: Zinc oxide (ZnO) is a II-VI semiconductor material that offers tremendous potential as a light emitter in the blue-to-UV range. It has a wurtzite structure, and a direct band gap that can be tuned from 3.0 to 4.0 eV by alloying with Cd or Mg, respectively. In this work, ZnO thin films were grown by metalorganic chemical vapor deposition (MOCVD) on n-Si 2 ° off (100), amorphous glass, n-GaAs (100), and c-plane sapphire substrates. Diethyl zinc (DEZn) and tert-butanol (TBOH) were chosen as precursors. For the first time, Second Harmonic Generation Imaging was applied to the mapping of ZnO epilayers. The images obtained highlighted the polycrystalline character of the thin films, and provided insight as to the growth mode of ZnO on Si. The influence of substrate temperature on the structural properties of the epilayers was investigated by X-ray diffraction and optical microscopy. Grain sizes as high as 54 nm were measured. The optimum temperature range for this system proved to be 450 – 500 °C. The influence of the VI:II ratio during growth on the optical properties of the epilayers was studied by UV-vis-near IR spectroscopy. The lowest Urbach tail E0 parameter was measured for material grown at a VI:II ratio of 18:1. The films’ free electron concentration was shown to decrease by over two orders of magnitude, from 1019 to 1017 cm-3, as the VI:II ratio increased from 10 to 60:1. This decrease in carrier concentration with rising VI:II ratio was paralleled to the surge at 12 K of a photoluminescence (PL) emission band characteristic of p-type ZnO. The band gap energies extracted from room temperature transmission spectra ranged between 3.35 and 3.38 eV, in agreement with the value of 3.35 eV measured by room temperature PL. Moreover, variable temperature PL spectra were recorded between 12 and 298 K on ZnO grown on Si. The 12 K spectrum was dominated by a donor-bound exciton (D°X) at 3.36 eV, while the 298 K scan displayed strong free exciton emission (FX) at 3.29 eV. The width of the D°X band proved to be as narrow as 7 meV. The intensity ratio between the room temperature near-band edge emission and the defect-related green band was as high as 28:1, highlighting the optical quality of the layers deposited in this work. The electrical properties of the thin films were studied by Hall measurements (van der Pauw configuration), and a maximum room temperature mobility of 11 cm2/Vs was recorded. Furthermore, a palladium (Pd) Schottky barrier diode on ZnO was fabricated. The barrier height and ideality factor were calculated from current–voltage measurements to be 0.83 eV and 1.6, respectively. The capacitance–voltage curve of the diode yielded a carrier concentration in the depletion region of 8·1017 cm-3. This study has shown that the optical and electrical properties of ZnO depend strongly on the growth conditions employed. A suitable choice of growth parameters can yield high quality ZnO that may be used for various devices. Keywords: Hall, MOCVD, optical spectroscopy, photoluminescence, Schottky barrier diode, SH Imaging, X-ray diffraction, ZnO.
- Full Text:
- Date Issued: 2004
Determination of 2′, 3′-Dideoxyinosine Using Iron (II) Phthalocyanine Modified Carbon Paste Electrode
- Ozoemena, Kenneth I, Stefan, Raluca-Ioana, Nyokong, Tebello
- Authors: Ozoemena, Kenneth I , Stefan, Raluca-Ioana , Nyokong, Tebello
- Date: 2004
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/300298 , vital:57914 , xlink:href="https://doi.org/10.1081/AL-200031940"
- Description: An amperometric sensor, based on carbon paste impregnated with iron (II) phthalocyanine complex (FePc), has been constructed for the assay of anti‐HIV agent dideoxyinosine (didanosine, DDI). Using chronoamperometry (E = +1.04 V versus Ag/AgCl) technique, the amperometric sensor can be used reliably for dideoxyinosine assay at pH 7.4 phosphate buffer in the 1.5–9.5 nmol/L concentration range with a detection limit of 5.7 × 10−10 mol/L. The surface of the electrode can easily be regenerated by simple polishing, obtaining a fresh surface ready for use in a new assay. The new amperometric sensor proved to be highly reliable for the assay of dideoxyinosine purity in raw material as well as for the uniformity content test of Videx® tablets.
- Full Text:
- Date Issued: 2004
- Authors: Ozoemena, Kenneth I , Stefan, Raluca-Ioana , Nyokong, Tebello
- Date: 2004
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/300298 , vital:57914 , xlink:href="https://doi.org/10.1081/AL-200031940"
- Description: An amperometric sensor, based on carbon paste impregnated with iron (II) phthalocyanine complex (FePc), has been constructed for the assay of anti‐HIV agent dideoxyinosine (didanosine, DDI). Using chronoamperometry (E = +1.04 V versus Ag/AgCl) technique, the amperometric sensor can be used reliably for dideoxyinosine assay at pH 7.4 phosphate buffer in the 1.5–9.5 nmol/L concentration range with a detection limit of 5.7 × 10−10 mol/L. The surface of the electrode can easily be regenerated by simple polishing, obtaining a fresh surface ready for use in a new assay. The new amperometric sensor proved to be highly reliable for the assay of dideoxyinosine purity in raw material as well as for the uniformity content test of Videx® tablets.
- Full Text:
- Date Issued: 2004
The enzymology of sludge solubilisation under biosulphidogenic conditions : isolation, characterisation and partial purification of endoglucanases
- Authors: Oyekola, Oluwaseun Oyekanmi
- Date: 2004
- Subjects: Sewage -- Purification -- Anaerobic treatment , Anaerobic bacteria , Sewage sludge , Hydrolysis
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:3921 , http://hdl.handle.net/10962/d1003980 , Sewage -- Purification -- Anaerobic treatment , Anaerobic bacteria , Sewage sludge , Hydrolysis
- Description: Endoglucanases play an important function in cellulose hydrolysis and catalyse the initial attack on the polymer by randomly hydrolysing the β-1,4 glucosidic bonds within the amorphous regions of cellulose chains. Cellulolytic bacteria have been isolated and characterised from the sewage sludge and the activation of several hydrolytic enzymes under biosulphidogenic conditions of sewage hydrolysis has been reported. The aims of this study were to: identify, induce production, locate and isolate, characterise (physicochemical and kinetic) and purify endoglucanases from anaerobic biosulphidogenic sludge. The endoglucanase activities were shown to be associated with the pellet particulate matter and exhibited a pH optimum of 6 and temperature optimum of 50 °C. The enzymes were thermally more stable when immobilised to the floc matrix of the sludge than when they were released into the aqueous solution via sonication. For both immobilised and released enzymes, sulphate was slightly inhibitory; activity was reduced to 84 % and 77.5 % of the initial activity at sulphate concentrations between 200 and 1000 mg/l, respectively. Sulphite was stimulatory to the immobilised enzymes between 200 and 1000 mg/l. Sulphide stimulated the activities of the immobilised endoglucanases, but inhibited activities of the soluble enzymes above 200 mg/l. The enzyme fraction did not hydrolyse avicel (a crystalline substrate), indicating the absence of any exocellulase activity. For CMC (carboxymethylcellulose) and HEC (hydroxylethylcellulose) the enzyme had K_m,app_ values of 4 and 5.1 mg/ml respectively and V_max,app_ values of 0.297 and 0.185 μmol/min/ml respectively. Divalent ions (Cu²⁺, Ni²⁺ and Zn²⁺) proved to be inhibitory while Fe²⁺, Mg²⁺ and Ca²⁺ stimulated the enzyme at concentrations between 200 and 1000 mg/l. All the volatile fatty acids studied (acetic acid, butyric acid, propionic acid and valeric acid) inhibited the enzymes, with acetic acid eliciting the highest degree of inhibition. Sonication released ~74.9 % of the total enzyme activities into solution and this was partially purified by PEG 20 000 concentration followed by DEAE-Cellulose ion exchange chromatography, which resulted in an appreciable purity as measured by the purification factor, 25.4 fold.
- Full Text:
- Date Issued: 2004
- Authors: Oyekola, Oluwaseun Oyekanmi
- Date: 2004
- Subjects: Sewage -- Purification -- Anaerobic treatment , Anaerobic bacteria , Sewage sludge , Hydrolysis
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:3921 , http://hdl.handle.net/10962/d1003980 , Sewage -- Purification -- Anaerobic treatment , Anaerobic bacteria , Sewage sludge , Hydrolysis
- Description: Endoglucanases play an important function in cellulose hydrolysis and catalyse the initial attack on the polymer by randomly hydrolysing the β-1,4 glucosidic bonds within the amorphous regions of cellulose chains. Cellulolytic bacteria have been isolated and characterised from the sewage sludge and the activation of several hydrolytic enzymes under biosulphidogenic conditions of sewage hydrolysis has been reported. The aims of this study were to: identify, induce production, locate and isolate, characterise (physicochemical and kinetic) and purify endoglucanases from anaerobic biosulphidogenic sludge. The endoglucanase activities were shown to be associated with the pellet particulate matter and exhibited a pH optimum of 6 and temperature optimum of 50 °C. The enzymes were thermally more stable when immobilised to the floc matrix of the sludge than when they were released into the aqueous solution via sonication. For both immobilised and released enzymes, sulphate was slightly inhibitory; activity was reduced to 84 % and 77.5 % of the initial activity at sulphate concentrations between 200 and 1000 mg/l, respectively. Sulphite was stimulatory to the immobilised enzymes between 200 and 1000 mg/l. Sulphide stimulated the activities of the immobilised endoglucanases, but inhibited activities of the soluble enzymes above 200 mg/l. The enzyme fraction did not hydrolyse avicel (a crystalline substrate), indicating the absence of any exocellulase activity. For CMC (carboxymethylcellulose) and HEC (hydroxylethylcellulose) the enzyme had K_m,app_ values of 4 and 5.1 mg/ml respectively and V_max,app_ values of 0.297 and 0.185 μmol/min/ml respectively. Divalent ions (Cu²⁺, Ni²⁺ and Zn²⁺) proved to be inhibitory while Fe²⁺, Mg²⁺ and Ca²⁺ stimulated the enzyme at concentrations between 200 and 1000 mg/l. All the volatile fatty acids studied (acetic acid, butyric acid, propionic acid and valeric acid) inhibited the enzymes, with acetic acid eliciting the highest degree of inhibition. Sonication released ~74.9 % of the total enzyme activities into solution and this was partially purified by PEG 20 000 concentration followed by DEAE-Cellulose ion exchange chromatography, which resulted in an appreciable purity as measured by the purification factor, 25.4 fold.
- Full Text:
- Date Issued: 2004
Economic feasibility of an experimental octopus fishery in South Africa
- Authors: Oosthuizen, Ané
- Date: 2004
- Language: English
- Type: Article
- Identifier: vital:6760 , http://hdl.handle.net/10962/d1007773
- Description: Octopus vulgaris was identified as a new marine resource to be commercially exploited through an experimental fishery. A recent policy on developing fisheries in South Africa emphasizes the importance of investigating the economic feasibility of a fishery as part of its management framework. The study reported here generated baseline information necessary in the design of the experimental fishery, giving guidelines as to which vessels, fishing gear and markets would be most feasible. The proposed fishery, gear and vessel type, fishing techniques and expected catch rates are described, the results of market research are outlined, and the cost of fishing is estimated. The potential business should consist of small and medium-sized vessels deploying unbaited pots attached to long lines. The longline pot fishery could be economically feasible, provided a 30 percent catch in 6600 pots/month is attained. Only existing, debt-free vessels should be used. The minimum catch per unit effort (CPUE) for various fishing operation scenarios was calculated to determine economic feasibility. This is an estimated minimum CPUE, based on assumptions that cannot be confirmed until the fishery starts. Furthermore, this economic analysis also needs to be assessed by stakeholders with experience of fishery operations , Rhodes Centenary issue of: South African Journal of Science.
- Full Text:
- Date Issued: 2004
- Authors: Oosthuizen, Ané
- Date: 2004
- Language: English
- Type: Article
- Identifier: vital:6760 , http://hdl.handle.net/10962/d1007773
- Description: Octopus vulgaris was identified as a new marine resource to be commercially exploited through an experimental fishery. A recent policy on developing fisheries in South Africa emphasizes the importance of investigating the economic feasibility of a fishery as part of its management framework. The study reported here generated baseline information necessary in the design of the experimental fishery, giving guidelines as to which vessels, fishing gear and markets would be most feasible. The proposed fishery, gear and vessel type, fishing techniques and expected catch rates are described, the results of market research are outlined, and the cost of fishing is estimated. The potential business should consist of small and medium-sized vessels deploying unbaited pots attached to long lines. The longline pot fishery could be economically feasible, provided a 30 percent catch in 6600 pots/month is attained. Only existing, debt-free vessels should be used. The minimum catch per unit effort (CPUE) for various fishing operation scenarios was calculated to determine economic feasibility. This is an estimated minimum CPUE, based on assumptions that cannot be confirmed until the fishery starts. Furthermore, this economic analysis also needs to be assessed by stakeholders with experience of fishery operations , Rhodes Centenary issue of: South African Journal of Science.
- Full Text:
- Date Issued: 2004
A development and management framework for a new Octopus vulgaris fishery in South Africa
- Authors: Oosthuizen, Ané
- Date: 2004
- Subjects: Common octopus -- South Africa Octopus fisheries -- South Africa Octopus fisheries -- South Africa -- Economic aspects Fishery management -- South Africa
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5255 , http://hdl.handle.net/10962/d1005098
- Description: A new policy incorporating an operational protocol was developed for the establishment of new fisheries in South Africa. The common octopus, Octopus vulgaris was used as a candidate species for the project. The operational protocol consisted of a three-phased development framework, namely information gathering (Phase 0), an experimental fishery (Phase 1) and the final implementation of a commercial fishery (Phase 2). The present study focussed on phase 0 of this theoretical framework and protocol and was implemented by using a proposed octopus pot fishery in South Africa as a case study. Phase 0 included a desktop study, information gathering in the field, an economic feasibility study and the formulation of a Fishery Management Plan and experimental design for the fishery. Information gaps identified during the desktop study were addressed during field investigations into the population structure and biology of O. vulgaris along the southeast coast. Immature females were found to use the intertidal area to feed and grow before migrating to the subtidal area to mature and spawn. Mean size differed substantially between intertidal and subtidal areas, with larger octopus found subtidally. Age and growth trials using tetracycline as a marker showed that O. vulgaris deposit daily growth lines in their beaks. A genetic study showed that there is most likely only one panmitic population along the coast. The economic feasibility study indicated that a longline pot fishery could be feasible provided a 30% catch in 6600 pots/month is attained. Only existing, debt-free vessels should be used in this fishery. The Fishery Management Plan proposed in this study includes management measures such as effort limitation of licences and gear, size restrictions, vessel monitoring systems, and observer programmes. Based on the population dynamics and biology of O. vulgaris it is suggested that a precautionary approach to developing fisheries for this species in both the inter- and subtidal areas along the South African coast.
- Full Text:
- Date Issued: 2004
- Authors: Oosthuizen, Ané
- Date: 2004
- Subjects: Common octopus -- South Africa Octopus fisheries -- South Africa Octopus fisheries -- South Africa -- Economic aspects Fishery management -- South Africa
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5255 , http://hdl.handle.net/10962/d1005098
- Description: A new policy incorporating an operational protocol was developed for the establishment of new fisheries in South Africa. The common octopus, Octopus vulgaris was used as a candidate species for the project. The operational protocol consisted of a three-phased development framework, namely information gathering (Phase 0), an experimental fishery (Phase 1) and the final implementation of a commercial fishery (Phase 2). The present study focussed on phase 0 of this theoretical framework and protocol and was implemented by using a proposed octopus pot fishery in South Africa as a case study. Phase 0 included a desktop study, information gathering in the field, an economic feasibility study and the formulation of a Fishery Management Plan and experimental design for the fishery. Information gaps identified during the desktop study were addressed during field investigations into the population structure and biology of O. vulgaris along the southeast coast. Immature females were found to use the intertidal area to feed and grow before migrating to the subtidal area to mature and spawn. Mean size differed substantially between intertidal and subtidal areas, with larger octopus found subtidally. Age and growth trials using tetracycline as a marker showed that O. vulgaris deposit daily growth lines in their beaks. A genetic study showed that there is most likely only one panmitic population along the coast. The economic feasibility study indicated that a longline pot fishery could be feasible provided a 30% catch in 6600 pots/month is attained. Only existing, debt-free vessels should be used in this fishery. The Fishery Management Plan proposed in this study includes management measures such as effort limitation of licences and gear, size restrictions, vessel monitoring systems, and observer programmes. Based on the population dynamics and biology of O. vulgaris it is suggested that a precautionary approach to developing fisheries for this species in both the inter- and subtidal areas along the South African coast.
- Full Text:
- Date Issued: 2004
Genetic analysis of the Octopus vulgaris population on the coast of South Africa
- Oosthuizen, Ané, Jiwaji, Meesbah, Shaw, Paul W
- Authors: Oosthuizen, Ané , Jiwaji, Meesbah , Shaw, Paul W
- Date: 2004
- Language: English
- Type: Article
- Identifier: vital:6761 , http://hdl.handle.net/10962/d1007922
- Description: This study on Octopus vulgaris focused on the COIII gene region of mitochondrial DNA. Sequences from 21 samples from the Eastern Cape, and 14 samples from the Western Cape, were compared to determine whether different populations exist along the South African coast. A 380-bp segment of the COIII region of mtDNA was amplified using the polymerase chain reaction with specific designed primers. Phylogenetic inference was made using maximum parsimony (MP), maximum likelihood (ML), and distance based methods. All sequences conformed to a single haplotype. Lack of variation within and between east and west coast samples precluded further population genetic analysis. The sequence obtained in this study was also compared with other sequences lodged in the Genbank database. Phylogenetically, the South African O. vulgaris is closely related to O. vulgaris from Senegal (0.67% divergence) and the Mediterranean (1.51% divergence). Within the Mediterranean group, O. vulgaris from South Africa displayed less sequence divergence from Senegalese and Mediterranean individuals than O. vulgaris from Venezuela (3.85%) and Taiwan (3.87%). These data do not, therefore, refute the hypothesis of a single O. vulgaris genetic population around the coast.
- Full Text:
- Date Issued: 2004
- Authors: Oosthuizen, Ané , Jiwaji, Meesbah , Shaw, Paul W
- Date: 2004
- Language: English
- Type: Article
- Identifier: vital:6761 , http://hdl.handle.net/10962/d1007922
- Description: This study on Octopus vulgaris focused on the COIII gene region of mitochondrial DNA. Sequences from 21 samples from the Eastern Cape, and 14 samples from the Western Cape, were compared to determine whether different populations exist along the South African coast. A 380-bp segment of the COIII region of mtDNA was amplified using the polymerase chain reaction with specific designed primers. Phylogenetic inference was made using maximum parsimony (MP), maximum likelihood (ML), and distance based methods. All sequences conformed to a single haplotype. Lack of variation within and between east and west coast samples precluded further population genetic analysis. The sequence obtained in this study was also compared with other sequences lodged in the Genbank database. Phylogenetically, the South African O. vulgaris is closely related to O. vulgaris from Senegal (0.67% divergence) and the Mediterranean (1.51% divergence). Within the Mediterranean group, O. vulgaris from South Africa displayed less sequence divergence from Senegalese and Mediterranean individuals than O. vulgaris from Venezuela (3.85%) and Taiwan (3.87%). These data do not, therefore, refute the hypothesis of a single O. vulgaris genetic population around the coast.
- Full Text:
- Date Issued: 2004