An investigation of the leadership practices and organizational culture at a private Christian school
- Authors: Babu, Bithun
- Date: 2018
- Subjects: Church schools -- South Africa -- Eastern Cape , Leadership , Corporate culture
- Language: English
- Type: text , Thesis , Masters , MBA
- Identifier: http://hdl.handle.net/10962/62155 , vital:28133
- Description: The purpose of this study is to investigate the leadership practices and organizational culture at a private Christian school in the Eastern Cape. A preliminary review of leadership literature suggested that traces of servant leadership may be apparent at the organization. Thus servant leadership will form a key focus area for exploration in this study. An analysis of this nature can make one aware of the influence leadership has in shaping the organizational culture of an institution. This in turn can be used to inform the future thinking around leadership efforts with respect to culture formation within an organization. The issue was addressed by consulting various articles to view the issue from different perspectives. The school served as a vehicle to explore the tenets of leadership and organizational culture. The study will take the form of a descriptive quantitative study. It was concluded that leadership plays a significant role in establishing the culture at an organization. However, leadership is not the only factor that shapes the organizational culture of an institution. The beliefs and values of the organization also has a role in shaping the overall culture and identity of an organization.
- Full Text:
- Authors: Babu, Bithun
- Date: 2018
- Subjects: Church schools -- South Africa -- Eastern Cape , Leadership , Corporate culture
- Language: English
- Type: text , Thesis , Masters , MBA
- Identifier: http://hdl.handle.net/10962/62155 , vital:28133
- Description: The purpose of this study is to investigate the leadership practices and organizational culture at a private Christian school in the Eastern Cape. A preliminary review of leadership literature suggested that traces of servant leadership may be apparent at the organization. Thus servant leadership will form a key focus area for exploration in this study. An analysis of this nature can make one aware of the influence leadership has in shaping the organizational culture of an institution. This in turn can be used to inform the future thinking around leadership efforts with respect to culture formation within an organization. The issue was addressed by consulting various articles to view the issue from different perspectives. The school served as a vehicle to explore the tenets of leadership and organizational culture. The study will take the form of a descriptive quantitative study. It was concluded that leadership plays a significant role in establishing the culture at an organization. However, leadership is not the only factor that shapes the organizational culture of an institution. The beliefs and values of the organization also has a role in shaping the overall culture and identity of an organization.
- Full Text:
An investigation of the teaching of reading in isiXhosa in three Grade 1 classrooms in the Eastern Cape, South Africa
- Authors: Magadla, Noluthando
- Date: 2018
- Language: English
- Type: text , Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10962/63408 , vital:28408
- Full Text: false
- Authors: Magadla, Noluthando
- Date: 2018
- Language: English
- Type: text , Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10962/63408 , vital:28408
- Full Text: false
Analysis of the human HSP70-HSP90 organising protein (HOP) gene - characterisation of the promoter and identification of a novel isoform
- Authors: Mattison, Stacey
- Date: 2018
- Language: English
- Type: text , Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10962/62821 , vital:28296
- Description: Expected release date-April 2020
- Full Text:
- Authors: Mattison, Stacey
- Date: 2018
- Language: English
- Type: text , Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10962/62821 , vital:28296
- Description: Expected release date-April 2020
- Full Text:
Antibiotic-Resistant Pathogenic Escherichia Coli Isolated from Rooftop Rainwater-Harvesting Tanks in the Eastern Cape, South Africa
- Malema, Mokaba Shirley, Abia, Akebe Luther King, Tandlich, Roman, Zuma, Bonga, Kahinda, Jean-Marc Mwenge, Ubomba-Jaswa, Eunice
- Authors: Malema, Mokaba Shirley , Abia, Akebe Luther King , Tandlich, Roman , Zuma, Bonga , Kahinda, Jean-Marc Mwenge , Ubomba-Jaswa, Eunice
- Date: 2018
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/71729 , vital:29931 , https://doi.org/10.3390/ijerph15050892
- Description: Although many developing countries use harvested rainwater (HRW) for drinking and other household purposes, its quality is seldom monitored. Continuous assessment of the microbial quality of HRW would ensure the safety of users of such water. The current study investigated the prevalence of pathogenic Escherichia coli strains and their antimicrobial resistance patterns in HRW tanks in the Eastern Cape, South Africa. Rainwater samples were collected weekly between June and September 2016 from 11 tanks in various areas of the province. Enumeration of E. coli was performed using the Colilert®18/Quanti-Tray® 2000 method. E. coli isolates were obtained and screened for their virulence potentials using polymerase chain reaction (PCR), and subsequently tested for antibiotic resistance using the disc-diffusion method against 11 antibiotics. The pathotype most detected was the neonatal meningitis E. coli (NMEC) (ibeA 28%) while pathotype enteroaggregative E. coli (EAEC) was not detected. The highest resistance of the E. coli isolates was observed against Cephalothin (76%). All tested pathotypes were susceptible to Gentamicin, and 52% demonstrated multiple-antibiotic resistance (MAR). The results of the current study are of public health concern since the use of untreated harvested rainwater for potable purposes may pose a risk of transmission of pathogenic and antimicrobial-resistant E. coli.
- Full Text:
- Authors: Malema, Mokaba Shirley , Abia, Akebe Luther King , Tandlich, Roman , Zuma, Bonga , Kahinda, Jean-Marc Mwenge , Ubomba-Jaswa, Eunice
- Date: 2018
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/71729 , vital:29931 , https://doi.org/10.3390/ijerph15050892
- Description: Although many developing countries use harvested rainwater (HRW) for drinking and other household purposes, its quality is seldom monitored. Continuous assessment of the microbial quality of HRW would ensure the safety of users of such water. The current study investigated the prevalence of pathogenic Escherichia coli strains and their antimicrobial resistance patterns in HRW tanks in the Eastern Cape, South Africa. Rainwater samples were collected weekly between June and September 2016 from 11 tanks in various areas of the province. Enumeration of E. coli was performed using the Colilert®18/Quanti-Tray® 2000 method. E. coli isolates were obtained and screened for their virulence potentials using polymerase chain reaction (PCR), and subsequently tested for antibiotic resistance using the disc-diffusion method against 11 antibiotics. The pathotype most detected was the neonatal meningitis E. coli (NMEC) (ibeA 28%) while pathotype enteroaggregative E. coli (EAEC) was not detected. The highest resistance of the E. coli isolates was observed against Cephalothin (76%). All tested pathotypes were susceptible to Gentamicin, and 52% demonstrated multiple-antibiotic resistance (MAR). The results of the current study are of public health concern since the use of untreated harvested rainwater for potable purposes may pose a risk of transmission of pathogenic and antimicrobial-resistant E. coli.
- Full Text:
Aquatic habitat shift assessment in a groundwater-fed semi-arid stream: an investigation into the response of Karoo hydroecology to system variability
- Authors: Ellis, Natalie
- Date: 2018
- Subjects: Aquatic habitats -- South Africa -- Karoo , Arid regions -- South Africa -- Karoo , Biotic communities -- South Africa -- Karoo , Stream ecology -- South Africa -- Karoo
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/61882 , vital:28072
- Description: From introduction: The subject of biological response to changes in aquatic habitat is one which has been well explored in many regions of the world. Examples include work in south east Spain by Mellado Diaz et al. (2008) and Oliva-Paterna et al. (2003), in western United States of America by Hauer and Lorang (2004), and in West Germany by Meyer et al. (2003). Similarly, a number of studies have been conducted in semi-arid regions, exploring elements such as erosion, climate, lithology and landscape formations (e.g. Boardman et al., 2013; Le Maitre et al., 2007; Meyer et al., 2003). However, apart from the study by Uys (1997), and Uys and O’Keeffe (1997), there is a noticeable lack of literature on aquatic habitat shifts in semi-arid stream systems, despite these systems being recognised for their high natural variability. This study provides a base-level approach to conducting habitat shift assessments in a semi-arid stream system and monitoring the hydroecological responses to system variability.
- Full Text:
- Authors: Ellis, Natalie
- Date: 2018
- Subjects: Aquatic habitats -- South Africa -- Karoo , Arid regions -- South Africa -- Karoo , Biotic communities -- South Africa -- Karoo , Stream ecology -- South Africa -- Karoo
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/61882 , vital:28072
- Description: From introduction: The subject of biological response to changes in aquatic habitat is one which has been well explored in many regions of the world. Examples include work in south east Spain by Mellado Diaz et al. (2008) and Oliva-Paterna et al. (2003), in western United States of America by Hauer and Lorang (2004), and in West Germany by Meyer et al. (2003). Similarly, a number of studies have been conducted in semi-arid regions, exploring elements such as erosion, climate, lithology and landscape formations (e.g. Boardman et al., 2013; Le Maitre et al., 2007; Meyer et al., 2003). However, apart from the study by Uys (1997), and Uys and O’Keeffe (1997), there is a noticeable lack of literature on aquatic habitat shifts in semi-arid stream systems, despite these systems being recognised for their high natural variability. This study provides a base-level approach to conducting habitat shift assessments in a semi-arid stream system and monitoring the hydroecological responses to system variability.
- Full Text:
Arbuscular mycorrhizal fungi persist in dying Euphorbia ingens trees
- Vivas, M, Crous, C J, Dames, Joanna F, van der Linde, J A, Coetzee, M P A, Roux, J
- Authors: Vivas, M , Crous, C J , Dames, Joanna F , van der Linde, J A , Coetzee, M P A , Roux, J
- Date: 2018
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/440465 , vital:73784 , https://doi.org/10.1016/j.sajb.2017.12.009
- Description: Forest declines have been reported with increasing regularity during the last decade and are expected to increase due to the ongoing environmental changes. During adverse environmental conditions, plant symbioses with mycorrhizas can help to reduce plant stress. Mycorrhizas are symbiotic associations between fungi and roots of living plants. Plants offer carbohydrates to the fungus and the fungus improves the acquisition of nutrients and water to the plant. Specifically, arbuscular mycorrhizal (AM) fungi are the most abundant mycorrhizas. In South Africa, there are increasing reports describing the decline of native Euphorbia ingens trees. This study analysed the presence and abundance of AM fungal colonisation in the roots of E. ingens trees, and the number of AM fungal spores in the surrounding soil, with the aim to improve the understanding of the rapid decline of these trees. AM fungal colonisation and spores in relation to the soil properties were also analysed. Soil and root samples were collected from different rates of declining E. ingens trees at three sites in South Africa. AM fungal colonisation of the roots was assessed and fungal spores in the surrounding soil were enumerated. Soil phosphorus, mineral nitrogen and pH were analysed from the soil samples. The results showed that AM fungi are associated with E. ingens trees. AM abundance was influenced by site specific properties and not by E. ingens health. Moreover, the level of soil NO3− and soil texture significantly influenced AM colonisation in roots and the number of spores enumerated. These preliminary findings provide background information for further research into the large-scale decline of E. ingens populations in South Africa.
- Full Text:
- Authors: Vivas, M , Crous, C J , Dames, Joanna F , van der Linde, J A , Coetzee, M P A , Roux, J
- Date: 2018
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/440465 , vital:73784 , https://doi.org/10.1016/j.sajb.2017.12.009
- Description: Forest declines have been reported with increasing regularity during the last decade and are expected to increase due to the ongoing environmental changes. During adverse environmental conditions, plant symbioses with mycorrhizas can help to reduce plant stress. Mycorrhizas are symbiotic associations between fungi and roots of living plants. Plants offer carbohydrates to the fungus and the fungus improves the acquisition of nutrients and water to the plant. Specifically, arbuscular mycorrhizal (AM) fungi are the most abundant mycorrhizas. In South Africa, there are increasing reports describing the decline of native Euphorbia ingens trees. This study analysed the presence and abundance of AM fungal colonisation in the roots of E. ingens trees, and the number of AM fungal spores in the surrounding soil, with the aim to improve the understanding of the rapid decline of these trees. AM fungal colonisation and spores in relation to the soil properties were also analysed. Soil and root samples were collected from different rates of declining E. ingens trees at three sites in South Africa. AM fungal colonisation of the roots was assessed and fungal spores in the surrounding soil were enumerated. Soil phosphorus, mineral nitrogen and pH were analysed from the soil samples. The results showed that AM fungi are associated with E. ingens trees. AM abundance was influenced by site specific properties and not by E. ingens health. Moreover, the level of soil NO3− and soil texture significantly influenced AM colonisation in roots and the number of spores enumerated. These preliminary findings provide background information for further research into the large-scale decline of E. ingens populations in South Africa.
- Full Text:
Art topples monuments: artistic practice and colonial/postcolonial relations in the public space of Luanda
- Authors: Siegert, Nadine
- Date: 2018
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/147014 , vital:38585
- Description: Even though there have been very few modern and contemporary artworks in the urban space of Luanda in the years after independence in 1975—and especially after the end of the civil war in 2002—there are two works by Angolan artists that are of particular interest: the sculpture Mitologias II (1984) by António Ole (b. 1951) and the photographic series Redefining the Power (2011) by Kiluanji Kia Henda (b. 1978). Both works address the possibility of using contemporary art as a symbolic form of the replacement of power, since both are built on pedestals that had previously supported monuments of Portuguese colonial power. They might, therefore, be read as a form of substitution for monuments that would commemorate and celebrate independence or the end of colonialism. This article also discusses whether these two artworks can also be regarded as counter-monuments and this contributes to the discourse on the visual and material culture of Lusophone Africa.
- Full Text:
- Authors: Siegert, Nadine
- Date: 2018
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/147014 , vital:38585
- Description: Even though there have been very few modern and contemporary artworks in the urban space of Luanda in the years after independence in 1975—and especially after the end of the civil war in 2002—there are two works by Angolan artists that are of particular interest: the sculpture Mitologias II (1984) by António Ole (b. 1951) and the photographic series Redefining the Power (2011) by Kiluanji Kia Henda (b. 1978). Both works address the possibility of using contemporary art as a symbolic form of the replacement of power, since both are built on pedestals that had previously supported monuments of Portuguese colonial power. They might, therefore, be read as a form of substitution for monuments that would commemorate and celebrate independence or the end of colonialism. This article also discusses whether these two artworks can also be regarded as counter-monuments and this contributes to the discourse on the visual and material culture of Lusophone Africa.
- Full Text:
Aspects Allocentristes de l’Humanisme dans l’Univers Romanesque de Williams Sassine
- Authors: Dami, Emmanuel Naancin
- Date: 2018
- Subjects: Sassine, Williams, 1944-1997 -- Criticism and interpretation , Guinean fiction (French) -- 20th century -- History and criticism , Humanism in literature , Human beings in literature , Postcolonialism in literature , Existentialism in literature
- Language: French , English
- Type: text , Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10962/61957 , vital:28089
- Description: The human being, his behaviour and more importantly, his very essence have, for time immemorial, proven to be enigmatic to many a man and to researchers in particular. Consequently, the need for a thorough and more profound understanding of man has made him the epicentre of epistemic investigations across many academic disciplines. This, unfortunately, does not seem to have shaded bright lights on the grey areas bordering on his nature to his behavior. This, in turn, opens up other windows requiring further probes. For instance, proponents of the Neo-classical economic school contend that the human being is homo oeconomicus. This implies that man is intrinsically egocentric and a rational being whose decisions are based on informed choices driven by his urge for maximal utility geared towards his personal satisfaction (O’Boyle 2009; Caruso 2012). This stance invalidates man’s ability to do ‘disinterested good’ in any form. African francophone literature is replete with different and diverse images of man, his behaviour and existential conditions: sufferings and struggles. It, therefore, constitutes, inter alia, a laboratory in which researchers undertake investigative endeavours. This thesis beams its floodlights on the allocentric aspects of humanism in the novels of Williams Sassine. Thus, using the phenomenological and ‘clavieniste’ lenses as overarching operational theories, the thesis investigates Sassine’s novels with the view to shading a ray of light on the ‘humanistic man’ especially the allocentric dimensions of his nature and comportment. Emphasis is laid on the motives and motivations underlying the individual and the in-group struggle of the sassinien heroes in the emancipation of their society from the shackles of colonial and postcolonial domination, exploitation and subjugation resulting in self-determination and the subsequent disenchantment. Furthermore, the thesis examines the nature and character of human charity, generosity and sacrifices among the characters in the novels. In conclusion, the thesis establishes, through an x-ray of the nature of actions and decisions of certain characters in the novels, the examination of the conscious and subconscious intentions underlying these same actions and decisions which, on a face value, are apparently altruistic, that the sassinien heroes’ efforts and sacrifices are geared towards the common and greater good. This invariably means that man is, indeed, capable of posing disinterested acts of charity and bringing succour, devoid of any ulterior motives for personal gain, to his fellow humans. The position of the Neo-classical economists is consequently over-assuming, sweeping and tad generalizing. The sassinien characters have demonstrated beyond reasonable doubt that they are humanists. Their nature, the remote and immediate causes of their fights, the goals and objectives of their struggles and their spirit of abnegation have indeed proven that “human beings have the right and the responsibility to give meaning and shape to their own lives. [They have stood] for the building of a more humane society through an ethics based on the human and other natural values in a spirit of reason and free inquiry through human capabilities” (AHA 2017 : 3).
- Full Text:
- Authors: Dami, Emmanuel Naancin
- Date: 2018
- Subjects: Sassine, Williams, 1944-1997 -- Criticism and interpretation , Guinean fiction (French) -- 20th century -- History and criticism , Humanism in literature , Human beings in literature , Postcolonialism in literature , Existentialism in literature
- Language: French , English
- Type: text , Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10962/61957 , vital:28089
- Description: The human being, his behaviour and more importantly, his very essence have, for time immemorial, proven to be enigmatic to many a man and to researchers in particular. Consequently, the need for a thorough and more profound understanding of man has made him the epicentre of epistemic investigations across many academic disciplines. This, unfortunately, does not seem to have shaded bright lights on the grey areas bordering on his nature to his behavior. This, in turn, opens up other windows requiring further probes. For instance, proponents of the Neo-classical economic school contend that the human being is homo oeconomicus. This implies that man is intrinsically egocentric and a rational being whose decisions are based on informed choices driven by his urge for maximal utility geared towards his personal satisfaction (O’Boyle 2009; Caruso 2012). This stance invalidates man’s ability to do ‘disinterested good’ in any form. African francophone literature is replete with different and diverse images of man, his behaviour and existential conditions: sufferings and struggles. It, therefore, constitutes, inter alia, a laboratory in which researchers undertake investigative endeavours. This thesis beams its floodlights on the allocentric aspects of humanism in the novels of Williams Sassine. Thus, using the phenomenological and ‘clavieniste’ lenses as overarching operational theories, the thesis investigates Sassine’s novels with the view to shading a ray of light on the ‘humanistic man’ especially the allocentric dimensions of his nature and comportment. Emphasis is laid on the motives and motivations underlying the individual and the in-group struggle of the sassinien heroes in the emancipation of their society from the shackles of colonial and postcolonial domination, exploitation and subjugation resulting in self-determination and the subsequent disenchantment. Furthermore, the thesis examines the nature and character of human charity, generosity and sacrifices among the characters in the novels. In conclusion, the thesis establishes, through an x-ray of the nature of actions and decisions of certain characters in the novels, the examination of the conscious and subconscious intentions underlying these same actions and decisions which, on a face value, are apparently altruistic, that the sassinien heroes’ efforts and sacrifices are geared towards the common and greater good. This invariably means that man is, indeed, capable of posing disinterested acts of charity and bringing succour, devoid of any ulterior motives for personal gain, to his fellow humans. The position of the Neo-classical economists is consequently over-assuming, sweeping and tad generalizing. The sassinien characters have demonstrated beyond reasonable doubt that they are humanists. Their nature, the remote and immediate causes of their fights, the goals and objectives of their struggles and their spirit of abnegation have indeed proven that “human beings have the right and the responsibility to give meaning and shape to their own lives. [They have stood] for the building of a more humane society through an ethics based on the human and other natural values in a spirit of reason and free inquiry through human capabilities” (AHA 2017 : 3).
- Full Text:
Aspects of the nutritional physiology of the perlemoen Haliotis midae (L.) and red abalone H. rufescens (Swainson)
- Authors: Kemp, Justin Oliver Gordon
- Date: 2018
- Subjects: Haliotis midae , Haliotis midae fisheries , Red abalone , Haliotis midae -- Feeding and feeds , Red abalone -- Feeding and feeds , Haliotis midae -- Nutrition -- Requirements , Red abalone -- Nutrition -- Requirements , Haliotis midae -- Metabolism , Red abalone -- Metabolism , Haliotis midae -- Physiology , Red abalone -- Physiology , Stable isotopes , Algae as feed
- Language: English
- Type: text , Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10962/62314 , vital:28154
- Description: The source of abalone for human consumption has shown a dramatic shift away from wild-capture fisheries in the last 30 years, with over 90% of global production now coming from aquaculture. Farmers initially relied on the natural food of abalone (macroalgae) as a culture feed, though in regions where macroalgae availability was limiting, the need to develop formulated feeds was evident. Extensive research effort has led to the development of a number of formulated feed products currently employed in the industry. These feeds, however, differ markedly from the mixed macroalgal diets that abalone have evolved to utilise, particularly in terms of protein content and carbohydrate structure. The degree to which the nutritional physiology of abalone responds to these novel formulated diets, with and without macroalgal supplementation, was investigated in the current study. A multifaceted approach, combining growth trials, stable isotope nutrient tracers and metabolic experiments, was employed to gain insight into the post-absorption dynamics and utilisation of dietary nutrients under varying dietary regimes of fresh macroalgae and formulated feed. Growth trials conducted with both Haliotis rufescens and H. midae showed significantly higher growth and protein utilisation efficiency for abalone fed macroalgal diets compared to formulated feeds. Furthermore, when formulated feeds were supplemented with macroalgae to form combination diets, growth and the utilization of protein was improved compared to the formulated-feed-only diet. The poor utilisation of protein by H. midae fed the formulated feed could be traced, using a method combining stable isotope bio-markers with a Bayesian mixing model (SIAR), to the low incorporation of the fishmeal component of protein in the diet. The marked postprandial drop in the O:N ratio on abalone fed formulated feeds indicate that the protein was being diverted into catabolic metabolic pathways. The metabolic cost of digestion, termed specific dynamic action (SDA), was negated as a factor in the improved growth of abalone fed macroalgal diets, with the SDA coefficient 2.1 times that observed for formulated feed. Furthermore, the postprandial haemolymph glucose concentration (HGC) in H. midae was elevated when fed formulated feed compared to macroalgae. The high levels of circulating glucose are likely a result of the structure the carbohydrate source in formulated feeds and stimulate the deposition of glycogen through the allosteric control of glycogen synthase. Formulated feeds produced higher cooked meat yields in canning simulation trials, suggesting that muscle glycogen content may indirectly play a role in increasing canning yields through the displacement of collagen. The results of these empirical studies are synthesised under key themes, discussed within the context of their potential commercial relevance and future research directions are highlighted.
- Full Text:
- Authors: Kemp, Justin Oliver Gordon
- Date: 2018
- Subjects: Haliotis midae , Haliotis midae fisheries , Red abalone , Haliotis midae -- Feeding and feeds , Red abalone -- Feeding and feeds , Haliotis midae -- Nutrition -- Requirements , Red abalone -- Nutrition -- Requirements , Haliotis midae -- Metabolism , Red abalone -- Metabolism , Haliotis midae -- Physiology , Red abalone -- Physiology , Stable isotopes , Algae as feed
- Language: English
- Type: text , Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10962/62314 , vital:28154
- Description: The source of abalone for human consumption has shown a dramatic shift away from wild-capture fisheries in the last 30 years, with over 90% of global production now coming from aquaculture. Farmers initially relied on the natural food of abalone (macroalgae) as a culture feed, though in regions where macroalgae availability was limiting, the need to develop formulated feeds was evident. Extensive research effort has led to the development of a number of formulated feed products currently employed in the industry. These feeds, however, differ markedly from the mixed macroalgal diets that abalone have evolved to utilise, particularly in terms of protein content and carbohydrate structure. The degree to which the nutritional physiology of abalone responds to these novel formulated diets, with and without macroalgal supplementation, was investigated in the current study. A multifaceted approach, combining growth trials, stable isotope nutrient tracers and metabolic experiments, was employed to gain insight into the post-absorption dynamics and utilisation of dietary nutrients under varying dietary regimes of fresh macroalgae and formulated feed. Growth trials conducted with both Haliotis rufescens and H. midae showed significantly higher growth and protein utilisation efficiency for abalone fed macroalgal diets compared to formulated feeds. Furthermore, when formulated feeds were supplemented with macroalgae to form combination diets, growth and the utilization of protein was improved compared to the formulated-feed-only diet. The poor utilisation of protein by H. midae fed the formulated feed could be traced, using a method combining stable isotope bio-markers with a Bayesian mixing model (SIAR), to the low incorporation of the fishmeal component of protein in the diet. The marked postprandial drop in the O:N ratio on abalone fed formulated feeds indicate that the protein was being diverted into catabolic metabolic pathways. The metabolic cost of digestion, termed specific dynamic action (SDA), was negated as a factor in the improved growth of abalone fed macroalgal diets, with the SDA coefficient 2.1 times that observed for formulated feed. Furthermore, the postprandial haemolymph glucose concentration (HGC) in H. midae was elevated when fed formulated feed compared to macroalgae. The high levels of circulating glucose are likely a result of the structure the carbohydrate source in formulated feeds and stimulate the deposition of glycogen through the allosteric control of glycogen synthase. Formulated feeds produced higher cooked meat yields in canning simulation trials, suggesting that muscle glycogen content may indirectly play a role in increasing canning yields through the displacement of collagen. The results of these empirical studies are synthesised under key themes, discussed within the context of their potential commercial relevance and future research directions are highlighted.
- Full Text:
Aspects of the population ecology, habitat use and behaviour of the endangered Knysna seahorse (Hippocampus capensis Boulenger, 1900) in a residential marina estate, Knysna, South Africa: implications for conservation
- Authors: Claassens, Louw
- Date: 2018
- Subjects: Endangered species -- South Africa -- Knysna , Sea horses -- Behavior -- South Africa -- Knysna , Sea horses -- Habitat -- South Africa -- Knysna , Sea horses -- Ecology -- South Africa -- Knysna
- Language: English
- Type: text , Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10962/54789 , vital:26616
- Description: The Knysna seahorse Hippocampus capensis is South Africa’s only endemic seahorse species, and is found in only three adjacent estuaries along the southern coast. The conservation of this endangered species is important on a national and international level. This study presents the first research on this species within the Knysna estuary since 2001 and specifically focuses on aspects of its ecology within a residential marina estate (Thesen Islands Marina). The physico-chemical and habitat features of the marina were described and the population ecology, habitat use, and behaviour of the Knysna seahorse were investigated. Physico-chemical conditions within the western section of the marina, characterised by high water current velocities, were similar to that of the adjacent estuary. The eastern section of the marina was characterised by lower water current velocities and higher turbidity. Four major habitat types were identified within the marina canals: (I) artificial Reno mattress (wire baskets filled with rocks); (II) Codium tenue beds; (III) mixed vegetation on sediment; and (IV) barren canal floor. Seahorse densities within the marina were significantly higher compared to densities found historically within the estuary. Highest seahorse densities were specifically found within the artificial Reno mattress structures and within the western section of the marina. Seahorse density varied spatially and temporally and the type of habitat was an important predictor for seahorse occurrence. An experimental investigation found that H. capensis chooses artificial Reno mattress habitat over Zostera capensis when given a choice. GoPro cameras were used successfully to investigate daytime seahorse behaviour within the Reno mattress habitat. Seahorses were more active during the morning, spent most of their time (> 80 %) feeding, and morning courting behaviour for this species were confirmed. However, during the summer holiday period (mid-December to mid-January) few seahorses were observed on camera, which suggests that the increase in motor boat activity and the related increase in noise had a negative effect on H. capensis feeding and courting behaviour. The marina development, and in particular the Reno mattresses, created a new habitat for this endangered species within the Knysna estuary. In addition to the protection and restoration of natural habitats in which H. capensis is found, the conservation potential of artificial structures such as Reno mattresses should be realised.
- Full Text:
- Authors: Claassens, Louw
- Date: 2018
- Subjects: Endangered species -- South Africa -- Knysna , Sea horses -- Behavior -- South Africa -- Knysna , Sea horses -- Habitat -- South Africa -- Knysna , Sea horses -- Ecology -- South Africa -- Knysna
- Language: English
- Type: text , Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10962/54789 , vital:26616
- Description: The Knysna seahorse Hippocampus capensis is South Africa’s only endemic seahorse species, and is found in only three adjacent estuaries along the southern coast. The conservation of this endangered species is important on a national and international level. This study presents the first research on this species within the Knysna estuary since 2001 and specifically focuses on aspects of its ecology within a residential marina estate (Thesen Islands Marina). The physico-chemical and habitat features of the marina were described and the population ecology, habitat use, and behaviour of the Knysna seahorse were investigated. Physico-chemical conditions within the western section of the marina, characterised by high water current velocities, were similar to that of the adjacent estuary. The eastern section of the marina was characterised by lower water current velocities and higher turbidity. Four major habitat types were identified within the marina canals: (I) artificial Reno mattress (wire baskets filled with rocks); (II) Codium tenue beds; (III) mixed vegetation on sediment; and (IV) barren canal floor. Seahorse densities within the marina were significantly higher compared to densities found historically within the estuary. Highest seahorse densities were specifically found within the artificial Reno mattress structures and within the western section of the marina. Seahorse density varied spatially and temporally and the type of habitat was an important predictor for seahorse occurrence. An experimental investigation found that H. capensis chooses artificial Reno mattress habitat over Zostera capensis when given a choice. GoPro cameras were used successfully to investigate daytime seahorse behaviour within the Reno mattress habitat. Seahorses were more active during the morning, spent most of their time (> 80 %) feeding, and morning courting behaviour for this species were confirmed. However, during the summer holiday period (mid-December to mid-January) few seahorses were observed on camera, which suggests that the increase in motor boat activity and the related increase in noise had a negative effect on H. capensis feeding and courting behaviour. The marina development, and in particular the Reno mattresses, created a new habitat for this endangered species within the Knysna estuary. In addition to the protection and restoration of natural habitats in which H. capensis is found, the conservation potential of artificial structures such as Reno mattresses should be realised.
- Full Text:
Assessment of pharmaceutical equivalence of topical cream products containing hydrocortisone acetate using in vitro release testing (IVRT)
- Mudyahoto, Nyengeterai Amanda
- Authors: Mudyahoto, Nyengeterai Amanda
- Date: 2018
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/63384 , vital:28404
- Description: Expected release date-April 2020
- Full Text:
- Authors: Mudyahoto, Nyengeterai Amanda
- Date: 2018
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/63384 , vital:28404
- Description: Expected release date-April 2020
- Full Text:
Assessment of pheromone specificity in Thaumatotibia leucotreta (Meyrick) populations with focus on pest monitoring and the regional rollout of the sterile insect technique in citrus
- Authors: Joubert, Francois D
- Date: 2018
- Subjects: Cryptophlebia leucotreta , Pheromone traps , Citrus -- Diseases and pests -- South Africa , Cryptophlebia leucotreta -- Contol , Cryptophlebia leucotreta -- Biological control
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/60665 , vital:27812
- Description: False codling moth (FCM), Thaumatotibia leucotreta (Meyrick) (Lepidoptera: Tortricidae) is considered the most important indigenous pest of citrus in southern Africa. It is recognized by several markets as a phytosanitary organism and the efficient control of this pest is now more important than ever. The pheromone communication between the male and female moths has been exploited in order to control FCM through the sterile insect technique (SIT). The sterilized males used for all SIT programmes across South Africa come from a colony that originates from wild material collected from the Citrusdal area of the Western Cape Province. The aim of this study was to determine if any differences in attractiveness of females to males exist between different geographical populations of FCM and if so what impact this would have on the male’s ability to locate females from other populations via the volatile sex pheromone released by the female. Laboratory trials with Y-tube olfactometers and flight tunnels tested the attraction of male moths to virgin females, but did not yield any consistent results. Field experiments were conducted with sterile male Citrusdal moths released and recaptured in yellow delta traps in two separate trials. For one trial, the traps were baited with live virgin females from five different geographical populations including Addo, Nelspruit, Marble Hall, Citrusdal and the Old colony, which is a mixture of several populations. For the other trial traps were baited with various synthetic pheromone blends including three regional blends which included South Africa, Ivory Coast and Malawi and three commercial blends including Pherolure, Isomate and Checkmate. For the virgin female trial the Citrusdal males showed a significant preference for females from their own population. There was also a significant difference in the recaptures from the different synthetic pheromones. The South African blend was the most attractive of all the regional and commercial blends. A cross-mating trial was also conducted under laboratory conditions in petri dishes with five different FCM populations including Citrusdal, Addo, Marble Hall, Nelspruit and Old (mixed origin). Females produced more eggs when mated with males from the same population for the Addo, Marble Hall, Nelspruit and Old (mixed origin) populations. The only case in which this was statistically significant was for the Marble Hall population. All the crosses produced viable eggs and the origin of the male or female did not influence egg hatch. The results from this study may lead to improvements in both the control and monitoring of FCM populations. The control methods include mating disruption, attract-and-kill and SIT. Tailoring these methods for a specific growing area with a pheromone blend originating from the area or releasing sterile moths from a colony that originates from the area may optimize the available monitoring and control options.
- Full Text:
- Authors: Joubert, Francois D
- Date: 2018
- Subjects: Cryptophlebia leucotreta , Pheromone traps , Citrus -- Diseases and pests -- South Africa , Cryptophlebia leucotreta -- Contol , Cryptophlebia leucotreta -- Biological control
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/60665 , vital:27812
- Description: False codling moth (FCM), Thaumatotibia leucotreta (Meyrick) (Lepidoptera: Tortricidae) is considered the most important indigenous pest of citrus in southern Africa. It is recognized by several markets as a phytosanitary organism and the efficient control of this pest is now more important than ever. The pheromone communication between the male and female moths has been exploited in order to control FCM through the sterile insect technique (SIT). The sterilized males used for all SIT programmes across South Africa come from a colony that originates from wild material collected from the Citrusdal area of the Western Cape Province. The aim of this study was to determine if any differences in attractiveness of females to males exist between different geographical populations of FCM and if so what impact this would have on the male’s ability to locate females from other populations via the volatile sex pheromone released by the female. Laboratory trials with Y-tube olfactometers and flight tunnels tested the attraction of male moths to virgin females, but did not yield any consistent results. Field experiments were conducted with sterile male Citrusdal moths released and recaptured in yellow delta traps in two separate trials. For one trial, the traps were baited with live virgin females from five different geographical populations including Addo, Nelspruit, Marble Hall, Citrusdal and the Old colony, which is a mixture of several populations. For the other trial traps were baited with various synthetic pheromone blends including three regional blends which included South Africa, Ivory Coast and Malawi and three commercial blends including Pherolure, Isomate and Checkmate. For the virgin female trial the Citrusdal males showed a significant preference for females from their own population. There was also a significant difference in the recaptures from the different synthetic pheromones. The South African blend was the most attractive of all the regional and commercial blends. A cross-mating trial was also conducted under laboratory conditions in petri dishes with five different FCM populations including Citrusdal, Addo, Marble Hall, Nelspruit and Old (mixed origin). Females produced more eggs when mated with males from the same population for the Addo, Marble Hall, Nelspruit and Old (mixed origin) populations. The only case in which this was statistically significant was for the Marble Hall population. All the crosses produced viable eggs and the origin of the male or female did not influence egg hatch. The results from this study may lead to improvements in both the control and monitoring of FCM populations. The control methods include mating disruption, attract-and-kill and SIT. Tailoring these methods for a specific growing area with a pheromone blend originating from the area or releasing sterile moths from a colony that originates from the area may optimize the available monitoring and control options.
- Full Text:
Assessment of the likely sensitivity to climate change for the key marine species in the southern Benguela system
- Ortega-Cisneros, Kelly, Yokwana, Sibusiso, Sauer, Warwick H H, Cochrane, Kevern L, James, Nicola C, Potts, Warren M, Singh, L, Smale, Malcolm J, Wood, A, Pecl, Gretta T
- Authors: Ortega-Cisneros, Kelly , Yokwana, Sibusiso , Sauer, Warwick H H , Cochrane, Kevern L , James, Nicola C , Potts, Warren M , Singh, L , Smale, Malcolm J , Wood, A , Pecl, Gretta T
- Date: 2018
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/123211 , vital:35415 , https://doi.10.2989/1814232X.2018.1512526
- Description: Climate change is altering many environmental parameters of coastal waters and open oceans, leading to substantial present-day and projected changes in the distribution, abundance and phenology of marine species. Attempts to assess how each species might respond to climate change can be data-, resource- and time-intensive. Moreover, in many regions of the world, including South Africa, species may be of vital socioeconomic or ecological importance though critical gaps may exist in our basic biological or ecological knowledge of the species. Here, we adapt and apply a trait-based sensitivity assessment for the key marine species in the southern Benguela system to estimate their potential relative sensitivity to the impacts of climate change. For our analysis, 40 priority species were selected based on their socioeconomic, ecological and/or recreational importance in the system. An extensive literature review and consultation with experts was undertaken concerning each species to gather information on their life history, habitat use and potential stressors. Fourteen attributes were used to estimate the selected species’ sensitivity and capacity to respond to climate change. A score ranging from low to high sensitivity was given for each attribute, based on the available information. Similarly, a score was assigned to the type and quality of information used to score each particular attribute, allowing an assessment of data-quality inputs for each species. The analysis identified the white steenbras Lithognathus lithognathus, soupfin shark Galeorhinus galeus, St Joseph Callorhinchus capensis and abalone Haliotis midae as potentially the most sensitive species to climate-change impacts in the southern Benguela system. There were data gaps for larval dispersal and settlement and metamorphosis cues for most of the evaluated species. Our results can be used by resource managers to determine the type of monitoring, intervention and planning that may be required to best respond to climate change, given the limited resources and significant knowledge gaps in many cases.
- Full Text:
- Authors: Ortega-Cisneros, Kelly , Yokwana, Sibusiso , Sauer, Warwick H H , Cochrane, Kevern L , James, Nicola C , Potts, Warren M , Singh, L , Smale, Malcolm J , Wood, A , Pecl, Gretta T
- Date: 2018
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/123211 , vital:35415 , https://doi.10.2989/1814232X.2018.1512526
- Description: Climate change is altering many environmental parameters of coastal waters and open oceans, leading to substantial present-day and projected changes in the distribution, abundance and phenology of marine species. Attempts to assess how each species might respond to climate change can be data-, resource- and time-intensive. Moreover, in many regions of the world, including South Africa, species may be of vital socioeconomic or ecological importance though critical gaps may exist in our basic biological or ecological knowledge of the species. Here, we adapt and apply a trait-based sensitivity assessment for the key marine species in the southern Benguela system to estimate their potential relative sensitivity to the impacts of climate change. For our analysis, 40 priority species were selected based on their socioeconomic, ecological and/or recreational importance in the system. An extensive literature review and consultation with experts was undertaken concerning each species to gather information on their life history, habitat use and potential stressors. Fourteen attributes were used to estimate the selected species’ sensitivity and capacity to respond to climate change. A score ranging from low to high sensitivity was given for each attribute, based on the available information. Similarly, a score was assigned to the type and quality of information used to score each particular attribute, allowing an assessment of data-quality inputs for each species. The analysis identified the white steenbras Lithognathus lithognathus, soupfin shark Galeorhinus galeus, St Joseph Callorhinchus capensis and abalone Haliotis midae as potentially the most sensitive species to climate-change impacts in the southern Benguela system. There were data gaps for larval dispersal and settlement and metamorphosis cues for most of the evaluated species. Our results can be used by resource managers to determine the type of monitoring, intervention and planning that may be required to best respond to climate change, given the limited resources and significant knowledge gaps in many cases.
- Full Text:
Assessment of the long-term response to rehabilitation of two wetlands in KwaZulu-Natal, South Africa
- Authors: Cowden, Craig
- Date: 2018
- Subjects: Wetlands -- South Africa -- KwaZulu-Natal Wetland restoration -- South Africa -- KwaZulu-Natal Wetland management -- South Africa -- KwaZulu-Natal Wetland conservation -- South Africa -- KwaZulu-Natal Wetland ecology -- South Africa -- KwaZulu-Natal Ecosystem management -- South Africa -- KwaZulu-Natal
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/60606 , vital:27802
- Description: Assessing the outputs and outcomes of wetland rehabilitation activities is recognised by the 'Working for Wetlands' programme in South Africa as important, but to date has been limited. An assessment of the ecological outcomes and the structural outputs of the Working for Wetlands rehabilitation implemented in the Killarney and Kruisfontein wetlands, KwaZulu-Natal, in 2005 was undertaken. The assessment of outcomes included an evaluation of the changes in terms of ecological integrity and the supply of ecosystem services, using WET-Health and WET- EcoServices assessment techniques respectively, and vegetation composition. Improvements in hydrological and geomorphic integrity were recorded in both wetlands, resulting in improved ecosystem services delivery. However, investigation of vegetation composition using the Wetland Index Value and Floristic Quality Assessment Index showed that, seven years after rehabilitation, KiNamey's vegetation composition had improved, but Kruisfontein's vegetation was still largely dominated by pioneer species and appeared to be stable, but in a severely transformed state. The response of these wetlands has shown that sites for rehabilitation should be screened before work begins, and wetlands requiring intensive management of vegetation recovery should be assessed in terms of the objectives and the anticipated benefits of the project. The assessment of the outputs included an evaluation of structural integrity, survival and cost- effectiveness. Limited issues, mostly relating to deviations from the designs during construction, were identified with regards to the structural outputs at each of the wetlands. However, the spreader canals at both Killarney and Kruisfontein wetlands were not functioning as intended and concentrated flows from the spreader canals were evident in both wetlands. The use of spreader canals should therefore be carefully planned and implemented for future wetland rehabilitation projects. Consideration of ZAR per hectare equivalent re-instated/secured provided a useful initial means of determining the cost-effectiveness of the wetland rehabilitation. However, additional factors need to be considered, such as, the nature of the rehabilitation activities, the type and size of the problem being addressed, rehabilitation of priority wetlands, limitations imposed by funders, and risks that need to be addressed by the rehabilitation strategy. Furthermore, the evaluation of the Killarney and Kruisfontein wetlands highlighted the need to revise the Water Research Commission's Wetland Management Series, especially those documents or guidelines relating to rehabilitation planning (WET-RehabPlan), interventions (WET-RehabMethods), and monitoring and evaluation (WET-RehabEvaluate).
- Full Text:
- Authors: Cowden, Craig
- Date: 2018
- Subjects: Wetlands -- South Africa -- KwaZulu-Natal Wetland restoration -- South Africa -- KwaZulu-Natal Wetland management -- South Africa -- KwaZulu-Natal Wetland conservation -- South Africa -- KwaZulu-Natal Wetland ecology -- South Africa -- KwaZulu-Natal Ecosystem management -- South Africa -- KwaZulu-Natal
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/60606 , vital:27802
- Description: Assessing the outputs and outcomes of wetland rehabilitation activities is recognised by the 'Working for Wetlands' programme in South Africa as important, but to date has been limited. An assessment of the ecological outcomes and the structural outputs of the Working for Wetlands rehabilitation implemented in the Killarney and Kruisfontein wetlands, KwaZulu-Natal, in 2005 was undertaken. The assessment of outcomes included an evaluation of the changes in terms of ecological integrity and the supply of ecosystem services, using WET-Health and WET- EcoServices assessment techniques respectively, and vegetation composition. Improvements in hydrological and geomorphic integrity were recorded in both wetlands, resulting in improved ecosystem services delivery. However, investigation of vegetation composition using the Wetland Index Value and Floristic Quality Assessment Index showed that, seven years after rehabilitation, KiNamey's vegetation composition had improved, but Kruisfontein's vegetation was still largely dominated by pioneer species and appeared to be stable, but in a severely transformed state. The response of these wetlands has shown that sites for rehabilitation should be screened before work begins, and wetlands requiring intensive management of vegetation recovery should be assessed in terms of the objectives and the anticipated benefits of the project. The assessment of the outputs included an evaluation of structural integrity, survival and cost- effectiveness. Limited issues, mostly relating to deviations from the designs during construction, were identified with regards to the structural outputs at each of the wetlands. However, the spreader canals at both Killarney and Kruisfontein wetlands were not functioning as intended and concentrated flows from the spreader canals were evident in both wetlands. The use of spreader canals should therefore be carefully planned and implemented for future wetland rehabilitation projects. Consideration of ZAR per hectare equivalent re-instated/secured provided a useful initial means of determining the cost-effectiveness of the wetland rehabilitation. However, additional factors need to be considered, such as, the nature of the rehabilitation activities, the type and size of the problem being addressed, rehabilitation of priority wetlands, limitations imposed by funders, and risks that need to be addressed by the rehabilitation strategy. Furthermore, the evaluation of the Killarney and Kruisfontein wetlands highlighted the need to revise the Water Research Commission's Wetland Management Series, especially those documents or guidelines relating to rehabilitation planning (WET-RehabPlan), interventions (WET-RehabMethods), and monitoring and evaluation (WET-RehabEvaluate).
- Full Text:
Avian thermoregulation in the heat: is evaporative cooling more economical in nocturnal birds?
- O'Connor, Ryan S, Smit, Ben, Talbot, William A, Gerson, Alexander R, Brigham, R Mark, Wolf, Blair O, McKechnie, Andrew E
- Authors: O'Connor, Ryan S , Smit, Ben , Talbot, William A , Gerson, Alexander R , Brigham, R Mark , Wolf, Blair O , McKechnie, Andrew E
- Date: 2018
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/441518 , vital:73895 , https://journals.biologists.com/jeb/article/221/17/jeb181420/19595/Avian-thermoregulation-in-the-heat-is-evaporative
- Description: Evaporative cooling is a prerequisite for avian occupancy of hot, arid environments, and is the only avenue of heat dissipation when air temperatures (Ta) exceed body temperature (Tb). Whereas diurnal birds can potentially rehydrate throughout the day, nocturnal species typically forgo drinking between sunrise and sunset. We hypothesized that nocturnal birds have evolved reduced rates of evaporative water loss (EWL) and more economical evaporative cooling mechanisms compared with diurnal species, permitting nocturnal species to tolerate extended periods of intense heat without becoming lethally dehydrated. We used phylogenetically informed regressions to compare EWL and evaporative cooling efficiency [ratio of evaporative heat loss (EHL) and metabolic heat production (MHP); EHL/MHP] among nocturnal and diurnal birds at high Ta. We analyzed variation in three response variables: (1) slope of EWL at Ta between 40 and 46°C, (2) EWL at Ta=46°C and (3) EHL/MHP at Ta=46°C. Nocturnality emerged as a weak, negative predictor, with nocturnal species having slightly shallower slopes and reduced EWL compared with diurnal species of similar mass.
- Full Text:
- Authors: O'Connor, Ryan S , Smit, Ben , Talbot, William A , Gerson, Alexander R , Brigham, R Mark , Wolf, Blair O , McKechnie, Andrew E
- Date: 2018
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/441518 , vital:73895 , https://journals.biologists.com/jeb/article/221/17/jeb181420/19595/Avian-thermoregulation-in-the-heat-is-evaporative
- Description: Evaporative cooling is a prerequisite for avian occupancy of hot, arid environments, and is the only avenue of heat dissipation when air temperatures (Ta) exceed body temperature (Tb). Whereas diurnal birds can potentially rehydrate throughout the day, nocturnal species typically forgo drinking between sunrise and sunset. We hypothesized that nocturnal birds have evolved reduced rates of evaporative water loss (EWL) and more economical evaporative cooling mechanisms compared with diurnal species, permitting nocturnal species to tolerate extended periods of intense heat without becoming lethally dehydrated. We used phylogenetically informed regressions to compare EWL and evaporative cooling efficiency [ratio of evaporative heat loss (EHL) and metabolic heat production (MHP); EHL/MHP] among nocturnal and diurnal birds at high Ta. We analyzed variation in three response variables: (1) slope of EWL at Ta between 40 and 46°C, (2) EWL at Ta=46°C and (3) EHL/MHP at Ta=46°C. Nocturnality emerged as a weak, negative predictor, with nocturnal species having slightly shallower slopes and reduced EWL compared with diurnal species of similar mass.
- Full Text:
Avian thermoregulation in the heat: phylogenetic variation among avian orders in evaporative cooling capacity and heat tolerance
- Smit, Ben, Whitfield, Maxine C, Talbot, William A, Gerson, Alexander R, McKechnie, Andrew E, Wolf, Blair O
- Authors: Smit, Ben , Whitfield, Maxine C , Talbot, William A , Gerson, Alexander R , McKechnie, Andrew E , Wolf, Blair O
- Date: 2018
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/440517 , vital:73789 , https://doi.org/10.1242/jeb.174870
- Description: Little is known about the phylogenetic variation of avian evaporative cooling efficiency and heat tolerance in hot environments. We quantified thermoregulatory responses to high air temperature (Ta) in ∼100-g representatives of three orders, namely, the African cuckoo (Cuculus gularis, Cuculiformes), lilac-breasted roller (Coracias caudatus, Coraciiformes) and Burchell's starling (Lamprotornis australis, Passeriformes). All three species initiated respiratory mechanisms to increase evaporative heat dissipation when body temperature (Tb) approached 41.5°C in response to increasing Ta, with gular flutter observed in cuckoos and panting in rollers and starlings. Resting metabolic rate and evaporative water loss increased by quantitatively similar magnitudes in all three species, although maximum rates of evaporative water loss were proportionately lower in starlings. Evaporative cooling efficiency [defined as the ratio of evaporative heat loss (EHL) to metabolic heat production (MHP)] generally remained below 2.0 in cuckoos and starlings, but reached a maximum of ∼3.5 in rollers. The high value for rollers reveals a very efficient evaporative cooling mechanism, and is similar to EHL/MHP maxima for similarly sized columbids which very effectively dissipate heat via cutaneous evaporation. This unexpected phylogenetic variation among the orders tested in the physiological mechanisms of heat dissipation is an important step toward determining the evolution of heat tolerance traits in desert birds.
- Full Text:
- Authors: Smit, Ben , Whitfield, Maxine C , Talbot, William A , Gerson, Alexander R , McKechnie, Andrew E , Wolf, Blair O
- Date: 2018
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/440517 , vital:73789 , https://doi.org/10.1242/jeb.174870
- Description: Little is known about the phylogenetic variation of avian evaporative cooling efficiency and heat tolerance in hot environments. We quantified thermoregulatory responses to high air temperature (Ta) in ∼100-g representatives of three orders, namely, the African cuckoo (Cuculus gularis, Cuculiformes), lilac-breasted roller (Coracias caudatus, Coraciiformes) and Burchell's starling (Lamprotornis australis, Passeriformes). All three species initiated respiratory mechanisms to increase evaporative heat dissipation when body temperature (Tb) approached 41.5°C in response to increasing Ta, with gular flutter observed in cuckoos and panting in rollers and starlings. Resting metabolic rate and evaporative water loss increased by quantitatively similar magnitudes in all three species, although maximum rates of evaporative water loss were proportionately lower in starlings. Evaporative cooling efficiency [defined as the ratio of evaporative heat loss (EHL) to metabolic heat production (MHP)] generally remained below 2.0 in cuckoos and starlings, but reached a maximum of ∼3.5 in rollers. The high value for rollers reveals a very efficient evaporative cooling mechanism, and is similar to EHL/MHP maxima for similarly sized columbids which very effectively dissipate heat via cutaneous evaporation. This unexpected phylogenetic variation among the orders tested in the physiological mechanisms of heat dissipation is an important step toward determining the evolution of heat tolerance traits in desert birds.
- Full Text:
Bacterial colonisation and degradation of geologically weathered and discard coal
- Authors: Olawale, Jacob Taiwo
- Date: 2018
- Subjects: Coal mine waste , Coal -- Biodegradation , Coal mines and mining -- Environmental aspects , Land degradation , Electron microscopy , Extracellular polymeric substances , Flagella (Microbiology) , Fourier transform infrared spectroscopy , Microbiologically influenced corrosion
- Language: English
- Type: text , Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10962/61625 , vital:28043
- Description: Bacterial beneficiation of low-grade coal, coal discard, and waste has the potential to mitigate land degradation, water and soil pollution and, be a strategy for mining companies to responsibly extract and process coal with environmental sustainability. This study investigated the colonisation and biodegradation or depolymerisation of coal discard and geologically weathered coal by selected strains of bacteria, and an attempt has been made to describe the mechanisms associated with colonisation and biodegradation of this carbonaceous material. Ten bacterial strains, Bacillus strain ECCN 18b, Citrobacter strain ECCN 19b, Proteus strain ECCN 20b, Exiguobacterium strain ECCN 21b, Microbacterium strain ECCN 22b, Proteus strain ECCN 23b, Serratia strain ECCN 24b, Escherichia strain ECCN 25b, Bacillus strain ECCN 26b and Bacillus strain ECCN 41b, isolated from diesel-contaminated soil and coal slurry and identified using DNA sequencing, were rescreened and their coal biodegradation potential ranked. The ranking of the bacterial strains was undertaken using several indicators including; formation of brown halos on the plate culture (solid), change in colour intensity of the medium in liquid culture, change in culture media pH, and an increase in absorbance at 280nm and 450nm. Although, all the ten strains showed evidence of biodegradation of coal discard and geologically weathered coal based on the ranking employed, and the three strains considered the best candidates were Citrobacter strain ECCN 19b, Exiguobacterium strain ECCN 21b and Serratia strain ECCN 24b. The actions of the three bacterial strains were further studied and characterised in relation to coal degradation. Electron microscopy revealed that Citrobacter strain ECCN 19b, Exiguobacterium strain ECCN 21b and Serratia strain ECCN 24b attached to the surface of coal discard and geologically weathered coal by a process that appeared to involve extracellular polymeric substances (EPS), and flagella. The presence of flagella for Citrobacter strain ECCN 19b and Serratia strain ECCN 24b was confirmed by transmission electron microscopy. Bacterial degradation of coal discard and geologically weathered coal by these selected strains resulted in the release of soluble and insoluble products. Ultraviolet/ visible spectrophotometric (UV/VIS) analysis revealed that the soluble products resembled humic acid-like substances, which was confirmed following Fourier Transform Infrared (FTIR) spectroscopy. Analysis revealed that the coal-derived humic acid-like substances were similar to commercial humic acid extracted from bituminous coal. Elemental analysis of the insoluble product residue after bacterial biodegradation revealed the modification of the chemical compositions of the coal discard and geologically weathered coal substrates. Characterisation of the functional groups of the insoluble product using FTIR spectroscopy indicated changes, with the appearance of new peaks at 1737cm-1, 1366cm-1, 1228cm-1, and 1216cm-1 characteristic of aldehyde, ketones, carboxylic acids, esters, amines, and alkanes. Broad spectra regions of 3500 -3200cm-1, characteristic of alcohol and phenol, were also observed. Together, these results were taken as evidence for increased oxidation of the coal substrates, presumably as a consequence of bacterial catalysed biodegradation of coal discard and geologically weathered coal. During bacterial degradation of coal discard and geologically weathered coal, strains produced extracellular protein, which was detected and further investigated using sodium dodecyl sulphate polyacrylamide gel electrophoresis (SDS- PAGE). At least three protein bands with molecular mass 53 kDa, 72 kDa, and 82 kDa were common to the three bacterial strains. Following ammonium sulphate precipitation and gel filtration chromatography, additional bands with molecular mass 16 kDa, 33 kDa, 37 kDa, and 43 kDa were detected. An extracellular laccase activity was detected in cultures of Exiguobacterium strain ECCN 21b and Serratia strain ECCN 24b. Cytochrome P450 activity was detected in all the bacterial strains in the presence of both coal discard and geologically weathered coal. This is the first time that cytochrome P450 activity has been reported following exposure of these three bacterial strains to a coal substrate. Overall, this research has successfully demonstrated the partial degradation of coal discard and geologically weathered coal by Citrobacter strain ECCN 19b, Exiguobacterium strain ECCN 21b and Serratia strain ECCN 24b and the release of humic acid-like substances. Thus, the biodegradation process involved adherence to and growth of the bacteria on the surface of coal substrate and appeared to require the formation of alkaline substances and the combined activities of extracellular LAC and cytochrome P450. Since bacterial degradation of low-grade coal and discard appears to be viable, the bacteria isolated in this study can potentially be used either for conversion of discard into valuable chemicals or to mitigate the deleterious effects of stockpiled coal discard on the environment.
- Full Text:
- Authors: Olawale, Jacob Taiwo
- Date: 2018
- Subjects: Coal mine waste , Coal -- Biodegradation , Coal mines and mining -- Environmental aspects , Land degradation , Electron microscopy , Extracellular polymeric substances , Flagella (Microbiology) , Fourier transform infrared spectroscopy , Microbiologically influenced corrosion
- Language: English
- Type: text , Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10962/61625 , vital:28043
- Description: Bacterial beneficiation of low-grade coal, coal discard, and waste has the potential to mitigate land degradation, water and soil pollution and, be a strategy for mining companies to responsibly extract and process coal with environmental sustainability. This study investigated the colonisation and biodegradation or depolymerisation of coal discard and geologically weathered coal by selected strains of bacteria, and an attempt has been made to describe the mechanisms associated with colonisation and biodegradation of this carbonaceous material. Ten bacterial strains, Bacillus strain ECCN 18b, Citrobacter strain ECCN 19b, Proteus strain ECCN 20b, Exiguobacterium strain ECCN 21b, Microbacterium strain ECCN 22b, Proteus strain ECCN 23b, Serratia strain ECCN 24b, Escherichia strain ECCN 25b, Bacillus strain ECCN 26b and Bacillus strain ECCN 41b, isolated from diesel-contaminated soil and coal slurry and identified using DNA sequencing, were rescreened and their coal biodegradation potential ranked. The ranking of the bacterial strains was undertaken using several indicators including; formation of brown halos on the plate culture (solid), change in colour intensity of the medium in liquid culture, change in culture media pH, and an increase in absorbance at 280nm and 450nm. Although, all the ten strains showed evidence of biodegradation of coal discard and geologically weathered coal based on the ranking employed, and the three strains considered the best candidates were Citrobacter strain ECCN 19b, Exiguobacterium strain ECCN 21b and Serratia strain ECCN 24b. The actions of the three bacterial strains were further studied and characterised in relation to coal degradation. Electron microscopy revealed that Citrobacter strain ECCN 19b, Exiguobacterium strain ECCN 21b and Serratia strain ECCN 24b attached to the surface of coal discard and geologically weathered coal by a process that appeared to involve extracellular polymeric substances (EPS), and flagella. The presence of flagella for Citrobacter strain ECCN 19b and Serratia strain ECCN 24b was confirmed by transmission electron microscopy. Bacterial degradation of coal discard and geologically weathered coal by these selected strains resulted in the release of soluble and insoluble products. Ultraviolet/ visible spectrophotometric (UV/VIS) analysis revealed that the soluble products resembled humic acid-like substances, which was confirmed following Fourier Transform Infrared (FTIR) spectroscopy. Analysis revealed that the coal-derived humic acid-like substances were similar to commercial humic acid extracted from bituminous coal. Elemental analysis of the insoluble product residue after bacterial biodegradation revealed the modification of the chemical compositions of the coal discard and geologically weathered coal substrates. Characterisation of the functional groups of the insoluble product using FTIR spectroscopy indicated changes, with the appearance of new peaks at 1737cm-1, 1366cm-1, 1228cm-1, and 1216cm-1 characteristic of aldehyde, ketones, carboxylic acids, esters, amines, and alkanes. Broad spectra regions of 3500 -3200cm-1, characteristic of alcohol and phenol, were also observed. Together, these results were taken as evidence for increased oxidation of the coal substrates, presumably as a consequence of bacterial catalysed biodegradation of coal discard and geologically weathered coal. During bacterial degradation of coal discard and geologically weathered coal, strains produced extracellular protein, which was detected and further investigated using sodium dodecyl sulphate polyacrylamide gel electrophoresis (SDS- PAGE). At least three protein bands with molecular mass 53 kDa, 72 kDa, and 82 kDa were common to the three bacterial strains. Following ammonium sulphate precipitation and gel filtration chromatography, additional bands with molecular mass 16 kDa, 33 kDa, 37 kDa, and 43 kDa were detected. An extracellular laccase activity was detected in cultures of Exiguobacterium strain ECCN 21b and Serratia strain ECCN 24b. Cytochrome P450 activity was detected in all the bacterial strains in the presence of both coal discard and geologically weathered coal. This is the first time that cytochrome P450 activity has been reported following exposure of these three bacterial strains to a coal substrate. Overall, this research has successfully demonstrated the partial degradation of coal discard and geologically weathered coal by Citrobacter strain ECCN 19b, Exiguobacterium strain ECCN 21b and Serratia strain ECCN 24b and the release of humic acid-like substances. Thus, the biodegradation process involved adherence to and growth of the bacteria on the surface of coal substrate and appeared to require the formation of alkaline substances and the combined activities of extracellular LAC and cytochrome P450. Since bacterial degradation of low-grade coal and discard appears to be viable, the bacteria isolated in this study can potentially be used either for conversion of discard into valuable chemicals or to mitigate the deleterious effects of stockpiled coal discard on the environment.
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Baculovirus synergism: investigating mixed alphabaculovirus and betabaculovirus infections in the false codling moth, thaumatotibia leucotreta, for improved pest control
- Authors: Jukes, Michael David
- Date: 2018
- Subjects: Baculoviruses , Cryptophlebia leucotreta -- Biological control , Citrus -- Diseases and pests -- South Africa , Pests -- Integrated control , Nucleopolyhedroviruses , Natural pesticides , Cryptophlebia leucotreta granulovirus (CrleGV)
- Language: English
- Type: text , Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10962/61797 , vital:28061
- Description: Baculovirus based biopesticides are an effective and environmentally friendly approach for the control of agriculturally important insect pests. The false codling moth (FCM), Thaumatotibia leucotreta (Meyrick) (Lepidoptera: Tortricidae), is indigenous to southern Africa and is a major pest of citrus crops. This moth poses a serious risk to export of fruit to foreign markets and the control of this pest is therefore imperative. The Cryptophlebia leucotreta granulovirus (CrleGV) has been commercially formulated into the products Cryptogran™ and Cryptex®. These products have been used successfully for over a decade as part of a rigorous integrated pest management (IPM) programme to control T. leucotreta in South Africa. There is however, a continuous need to improve this programme while also addressing new challenges as they arise. An example of a rising concern is the possibility of resistance developing towards CrleGV. This was seen in Europe with field populations of the codling moth, Cydia pomonella (Linnaeus) (Lepidoptera: Tortricidae), which developed resistance to the Mexican isolate of the Cydia pomonella granulovirus (CpGV-M). To prevent such a scenario occurring in South Africa, there is a need to improve existing methods of control. For example, additional baculovirus variants can be isolated and characterised for determining virulence, which can then be developed as new biopesticides. Additionally, the potential for synergistic effects between different baculoviruses infecting the same host can be explored for improved virulence. A novel nucleopolyhedrovirus was recently identified in T. leucotreta larval homogenates which were also infected with CrleGV. This provided unique opportunities for continued research and development. In this study, a method using C. pomonella larvae, which can be infected by the NPV but not by CrleGV, was developed to separate the NPV from GV-NPV mixtures in an in vivo system. Examination of NPV OBs by transmission electron microscopy showed purified occlusion bodies with a single nucleopolyhedrovirus morphology (SNPV). Genetic characterisation identified the novel NPV as Cryptophlebia peltastica nucleopolyhedrovirus (CrpeNPV), which was recently isolated from the litchi moth, Cryptophlebia peltastica (Meyrick) (Lepidoptera: Tortricidae). To begin examining the potential for synergism between the two viruses, a multiplex PCR assay was developed to accurately detect CrleGV and/or CrpeNPV in mixed infections. This assay was applied to various samples to screen for the presence of CrpeNPV and CrleGV. Additionally, a validation experiment was performed using different combinations of CrpeNPV and/or CrleGV to evaluate the effectiveness of the mPCR assay. The results obtained indicated a high degree of specificity with the correct amplicons generated for each test sample. The biological activity of CrpeNPV and CrleGV were evaluated using surface dose bioassays, both individually and in various combinations, against T. leucotreta neonate larvae in a laboratory setting. A synergistic effect was recorded in the combination treatments, showing improved virulence when compared against each virus in isolation. The LC90 for CrpeNPV and CrleGV when applied alone against T. leucotreta was calculated to be 2.75*106 and 3.00*106 OBs.ml"1 respectively. These values decreased to 1.07*106 and 7.18*105 OBs.ml"1 when combinations of CrleGV and CrpeNPV were applied at ratios of 3:1 and 1:3 respectively. These results indicate a potential for developing improved biopesticides for the control of T. leucotreta in the field. To better understand the interactions between CrleGV and CrpeNPV, experiments involving the serial passage of these viruses through T. leucotreta larvae were performed. This was done using each virus in isolation as well as both viruses in different combinations. Genomic DNA was extracted from recovered occlusion bodies after each passage and examined by multiplex and quantitative PCR. This analysis enabled the detection of each virus present throughout this assay, as well as recording shifts in the ratio of CrleGV and CrpeNPV at each passage. CrleGV rapidly became the dominant virus in all treatments, indicating a potentially antagonistic interaction during serial passage. Additionally, CrpeNPV and CrleGV were detected in treatments which were not originally inoculated with one or either virus, indicating potential covert infections in T. leucotreta. Occlusion bodies recovered from the final passage were used to inoculate C. pomonella larvae to isolate CrpeNPV from CrleGV. Genomic DNA was extracted from these CrpeNPV OBs and examined by restriction endonuclease assays and next generation sequencing. This enabled the identification of potential recombination events which may have occurred during the dual GV and NPV infections throughout the passage assay. No recombination events were identified in the CrpeNPV genome sequences assembled from virus collected at the end of the passage assay. Lastly, the efficacy of CrpeNPV and CrleGV, both alone and in various combinations, was evaluated in the field. In two separate trials conducted on citrus, unfavorable field conditions resulted in no significant reduction in fruit infestation for both the virus and chemical treatments. While not statistically significant, virus treatments were recorded to have the lowest levels of fruit infestation with a measured reduction of up to 64 %. This study is the first to report a synergistic effect between CrleGV and CrpeNPV in T. leucotreta. The discovery of beneficial interactions creates an opportunity for the development of novel biopesticides for improved control of this pest in South Africa.
- Full Text:
- Authors: Jukes, Michael David
- Date: 2018
- Subjects: Baculoviruses , Cryptophlebia leucotreta -- Biological control , Citrus -- Diseases and pests -- South Africa , Pests -- Integrated control , Nucleopolyhedroviruses , Natural pesticides , Cryptophlebia leucotreta granulovirus (CrleGV)
- Language: English
- Type: text , Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10962/61797 , vital:28061
- Description: Baculovirus based biopesticides are an effective and environmentally friendly approach for the control of agriculturally important insect pests. The false codling moth (FCM), Thaumatotibia leucotreta (Meyrick) (Lepidoptera: Tortricidae), is indigenous to southern Africa and is a major pest of citrus crops. This moth poses a serious risk to export of fruit to foreign markets and the control of this pest is therefore imperative. The Cryptophlebia leucotreta granulovirus (CrleGV) has been commercially formulated into the products Cryptogran™ and Cryptex®. These products have been used successfully for over a decade as part of a rigorous integrated pest management (IPM) programme to control T. leucotreta in South Africa. There is however, a continuous need to improve this programme while also addressing new challenges as they arise. An example of a rising concern is the possibility of resistance developing towards CrleGV. This was seen in Europe with field populations of the codling moth, Cydia pomonella (Linnaeus) (Lepidoptera: Tortricidae), which developed resistance to the Mexican isolate of the Cydia pomonella granulovirus (CpGV-M). To prevent such a scenario occurring in South Africa, there is a need to improve existing methods of control. For example, additional baculovirus variants can be isolated and characterised for determining virulence, which can then be developed as new biopesticides. Additionally, the potential for synergistic effects between different baculoviruses infecting the same host can be explored for improved virulence. A novel nucleopolyhedrovirus was recently identified in T. leucotreta larval homogenates which were also infected with CrleGV. This provided unique opportunities for continued research and development. In this study, a method using C. pomonella larvae, which can be infected by the NPV but not by CrleGV, was developed to separate the NPV from GV-NPV mixtures in an in vivo system. Examination of NPV OBs by transmission electron microscopy showed purified occlusion bodies with a single nucleopolyhedrovirus morphology (SNPV). Genetic characterisation identified the novel NPV as Cryptophlebia peltastica nucleopolyhedrovirus (CrpeNPV), which was recently isolated from the litchi moth, Cryptophlebia peltastica (Meyrick) (Lepidoptera: Tortricidae). To begin examining the potential for synergism between the two viruses, a multiplex PCR assay was developed to accurately detect CrleGV and/or CrpeNPV in mixed infections. This assay was applied to various samples to screen for the presence of CrpeNPV and CrleGV. Additionally, a validation experiment was performed using different combinations of CrpeNPV and/or CrleGV to evaluate the effectiveness of the mPCR assay. The results obtained indicated a high degree of specificity with the correct amplicons generated for each test sample. The biological activity of CrpeNPV and CrleGV were evaluated using surface dose bioassays, both individually and in various combinations, against T. leucotreta neonate larvae in a laboratory setting. A synergistic effect was recorded in the combination treatments, showing improved virulence when compared against each virus in isolation. The LC90 for CrpeNPV and CrleGV when applied alone against T. leucotreta was calculated to be 2.75*106 and 3.00*106 OBs.ml"1 respectively. These values decreased to 1.07*106 and 7.18*105 OBs.ml"1 when combinations of CrleGV and CrpeNPV were applied at ratios of 3:1 and 1:3 respectively. These results indicate a potential for developing improved biopesticides for the control of T. leucotreta in the field. To better understand the interactions between CrleGV and CrpeNPV, experiments involving the serial passage of these viruses through T. leucotreta larvae were performed. This was done using each virus in isolation as well as both viruses in different combinations. Genomic DNA was extracted from recovered occlusion bodies after each passage and examined by multiplex and quantitative PCR. This analysis enabled the detection of each virus present throughout this assay, as well as recording shifts in the ratio of CrleGV and CrpeNPV at each passage. CrleGV rapidly became the dominant virus in all treatments, indicating a potentially antagonistic interaction during serial passage. Additionally, CrpeNPV and CrleGV were detected in treatments which were not originally inoculated with one or either virus, indicating potential covert infections in T. leucotreta. Occlusion bodies recovered from the final passage were used to inoculate C. pomonella larvae to isolate CrpeNPV from CrleGV. Genomic DNA was extracted from these CrpeNPV OBs and examined by restriction endonuclease assays and next generation sequencing. This enabled the identification of potential recombination events which may have occurred during the dual GV and NPV infections throughout the passage assay. No recombination events were identified in the CrpeNPV genome sequences assembled from virus collected at the end of the passage assay. Lastly, the efficacy of CrpeNPV and CrleGV, both alone and in various combinations, was evaluated in the field. In two separate trials conducted on citrus, unfavorable field conditions resulted in no significant reduction in fruit infestation for both the virus and chemical treatments. While not statistically significant, virus treatments were recorded to have the lowest levels of fruit infestation with a measured reduction of up to 64 %. This study is the first to report a synergistic effect between CrleGV and CrpeNPV in T. leucotreta. The discovery of beneficial interactions creates an opportunity for the development of novel biopesticides for improved control of this pest in South Africa.
- Full Text:
Barriers and drivers to the implementation of renewable energy technologies in South Africa’s aquaculture industry
- Authors: Van Wyk, Nicholas Kelly
- Date: 2018
- Subjects: Renewable energy sources South Africa , Aquaculture Environmental aspects South Africa , Sustainable aquaculture Economic aspects South Africa , Renewable energy sources Economic aspects South Africa , Renewable energy sources Environmental aspects South Africa
- Language: English
- Type: text , Thesis , Masters , MBA
- Identifier: http://hdl.handle.net/10962/61969 , vital:28090
- Description: South Africa is plagued by socio-economic issues of poverty, inequality and high rates of unemployment. The government of South Africa has as such launched an ambitious plan known as operation PHAKISA which will complement the National Development Plan in addressing the countries aforementioned shortcomings. In the operations first phase, the focus is on growing South Africa’s ocean economy. Within the ocean economy, the growth of aquaculture has been identified as an industry with the potential to create jobs and aid in economic growth of South Africa. Aquaculture, the farming of any aquatic organisms, has been the fastest growing food production sector for the past 50 years. While natural capture fisheries have stagnated in production capacity, aquaculture has grown exponentially in order to feed a global population which is fast approaching nine billion people. However, South Africa’s aquaculture production lags significantly behind other third world countries. The sustainability of aquaculture has frequently been called into question due to the possibility of various detrimental environmental effects it may cause. To further complicate the matter, Climate Change is today an overarching threat to life as we know it, and must be taken into account if we plan to keep growing our populations and economies. As such, if South Africa wants to grow its aquaculture sector, it must be done so in a sustainable manner. This research thus sought to investigate one aspect which may increase the sustainability of aquaculture in South Africa, that being the implementation of renewable energy in the sector. Renewable energy has been identified by the United Nations Intergovernmental Panel on Climate Change as key to mitigating the effects of climate change. In order to aid Renewable Energy (RE) implementation in South Africa’s aquaculture sector, this research aimed to identify the barriers and the drivers to implementing renewable energy within aquaculture. To do this, a literature review was conducted to identify possible barriers and drivers to renewable energy implementation. These were then drafted into an online questionnaire and sent via Email to all the aquaculture organisations in South Africa that could be contacted (n = 195). Respondents were asked to rank the proposed barriers and drivers to renewable energy according to their perceived importance on a Likert Scale. A total of 18 responses could be analysed with descriptive statistics. Further, three structured interviews were conducted with members of South African aquaculture organisations who had implemented some form of Renewable Energy Technology (RET). These interviews provided in-depth insights into the importance of the various proposed barriers and drivers. The results revealed the most important barriers to RE implementation were: High Initial investments, Utility monopoly of production, Lack of RE experts on a governmental level, Lack of incentives/subsidies from government, Lack of legal framework for Independent Power Producers and Power Purchase Agreements, and Diseconomy of scale respectively. The most important drivers to RE implementation were ranked as: Long term cost benefits, Reduction in cost of RETs, Innovation / advancement of RETS, Incentives or subsidies to implement renewable energy, Adequate legal framework and legislation for Power Purchase Agreement and Preference for environmentally-friendly electricity generation. Importantly, it was found that barriers and drivers are dependent on the type of RE being implemented. A Photo Voltaic (Solar Power) system will not necessarily experience the same barriers or drivers that a Wave Energy Converter system would. In order to drive investment in RE and remove the barriers that may be preventing its implementation in aquaculture, policy will have to be adapted. Particularly in terms of legislation around Power Purchase Agreements. Further, by providing subsidies for RE implementation, it is possible to sustainably grow South Africa’s aquaculture industry.
- Full Text:
- Authors: Van Wyk, Nicholas Kelly
- Date: 2018
- Subjects: Renewable energy sources South Africa , Aquaculture Environmental aspects South Africa , Sustainable aquaculture Economic aspects South Africa , Renewable energy sources Economic aspects South Africa , Renewable energy sources Environmental aspects South Africa
- Language: English
- Type: text , Thesis , Masters , MBA
- Identifier: http://hdl.handle.net/10962/61969 , vital:28090
- Description: South Africa is plagued by socio-economic issues of poverty, inequality and high rates of unemployment. The government of South Africa has as such launched an ambitious plan known as operation PHAKISA which will complement the National Development Plan in addressing the countries aforementioned shortcomings. In the operations first phase, the focus is on growing South Africa’s ocean economy. Within the ocean economy, the growth of aquaculture has been identified as an industry with the potential to create jobs and aid in economic growth of South Africa. Aquaculture, the farming of any aquatic organisms, has been the fastest growing food production sector for the past 50 years. While natural capture fisheries have stagnated in production capacity, aquaculture has grown exponentially in order to feed a global population which is fast approaching nine billion people. However, South Africa’s aquaculture production lags significantly behind other third world countries. The sustainability of aquaculture has frequently been called into question due to the possibility of various detrimental environmental effects it may cause. To further complicate the matter, Climate Change is today an overarching threat to life as we know it, and must be taken into account if we plan to keep growing our populations and economies. As such, if South Africa wants to grow its aquaculture sector, it must be done so in a sustainable manner. This research thus sought to investigate one aspect which may increase the sustainability of aquaculture in South Africa, that being the implementation of renewable energy in the sector. Renewable energy has been identified by the United Nations Intergovernmental Panel on Climate Change as key to mitigating the effects of climate change. In order to aid Renewable Energy (RE) implementation in South Africa’s aquaculture sector, this research aimed to identify the barriers and the drivers to implementing renewable energy within aquaculture. To do this, a literature review was conducted to identify possible barriers and drivers to renewable energy implementation. These were then drafted into an online questionnaire and sent via Email to all the aquaculture organisations in South Africa that could be contacted (n = 195). Respondents were asked to rank the proposed barriers and drivers to renewable energy according to their perceived importance on a Likert Scale. A total of 18 responses could be analysed with descriptive statistics. Further, three structured interviews were conducted with members of South African aquaculture organisations who had implemented some form of Renewable Energy Technology (RET). These interviews provided in-depth insights into the importance of the various proposed barriers and drivers. The results revealed the most important barriers to RE implementation were: High Initial investments, Utility monopoly of production, Lack of RE experts on a governmental level, Lack of incentives/subsidies from government, Lack of legal framework for Independent Power Producers and Power Purchase Agreements, and Diseconomy of scale respectively. The most important drivers to RE implementation were ranked as: Long term cost benefits, Reduction in cost of RETs, Innovation / advancement of RETS, Incentives or subsidies to implement renewable energy, Adequate legal framework and legislation for Power Purchase Agreement and Preference for environmentally-friendly electricity generation. Importantly, it was found that barriers and drivers are dependent on the type of RE being implemented. A Photo Voltaic (Solar Power) system will not necessarily experience the same barriers or drivers that a Wave Energy Converter system would. In order to drive investment in RE and remove the barriers that may be preventing its implementation in aquaculture, policy will have to be adapted. Particularly in terms of legislation around Power Purchase Agreements. Further, by providing subsidies for RE implementation, it is possible to sustainably grow South Africa’s aquaculture industry.
- Full Text:
Baseline isotopic data for Wolffia spp.: another option for tracing N-loading in freshwater systems?
- Authors: Hill, Jaclyn M
- Date: 2018
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/68721 , vital:29308 , https://0-doi.org.wam.seals.ac.za/10.1086/696126
- Description: δ15N values of aquatic plants can reflect anthropogenic N loading. Recent work suggests the duckweed Spirodela spp. effectively maps N loading in freshwater ecosystems, but its use may be complicated by a cyanobacterium–duckweed symbiosis that could reduce its utility in low-nutrient environments. I aimed to evaluate the potential of a 2nd duckweed species Wolffia spp., which lacks a cyanobacterial symbiosis, for use in pollution monitoring in freshwater ecosystems. I used a series of laboratory experiments to investigate δ15N equilibration rates and concentration-level effects of single-source N solutions in plant tissue over 16 d to provide baseline data for sewage-plume mapping with Wolffia spp. I also tested concentration-level effects in multisource solutions to investigate the effects of mixed-source inputs. Wolffia reflected environmental N sources with a 12- to 16-d isotopic equilibration time and showed enriched and depleted δ15N ratios for manure and KNO3 solutions, respectively, but distinguished poorly between lower concentrations of manure. Fractionations at isotopic equilibrium were opposite to expectations and decreased with increasing [N]. Wolffia showed a consistent preference for NH3 in mixed-source treatments, regardless of the proportion or concentration of NH3 or NO3– available, and a capacity for N storage, which may complicate mapping of N-loading in natural environments. Wolffia is likely to be a less useful bioindicator than the previously tested Spirodela. Future research should focus on field applications of Spirodela spp. to test its capacity for sewage-plume mapping of freshwater ecosystems in a natural environment.
- Full Text: false
Baseline isotopic data for Wolffia spp.: another option for tracing N-loading in freshwater systems?
- Authors: Hill, Jaclyn M
- Date: 2018
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/68721 , vital:29308 , https://0-doi.org.wam.seals.ac.za/10.1086/696126
- Description: δ15N values of aquatic plants can reflect anthropogenic N loading. Recent work suggests the duckweed Spirodela spp. effectively maps N loading in freshwater ecosystems, but its use may be complicated by a cyanobacterium–duckweed symbiosis that could reduce its utility in low-nutrient environments. I aimed to evaluate the potential of a 2nd duckweed species Wolffia spp., which lacks a cyanobacterial symbiosis, for use in pollution monitoring in freshwater ecosystems. I used a series of laboratory experiments to investigate δ15N equilibration rates and concentration-level effects of single-source N solutions in plant tissue over 16 d to provide baseline data for sewage-plume mapping with Wolffia spp. I also tested concentration-level effects in multisource solutions to investigate the effects of mixed-source inputs. Wolffia reflected environmental N sources with a 12- to 16-d isotopic equilibration time and showed enriched and depleted δ15N ratios for manure and KNO3 solutions, respectively, but distinguished poorly between lower concentrations of manure. Fractionations at isotopic equilibrium were opposite to expectations and decreased with increasing [N]. Wolffia showed a consistent preference for NH3 in mixed-source treatments, regardless of the proportion or concentration of NH3 or NO3– available, and a capacity for N storage, which may complicate mapping of N-loading in natural environments. Wolffia is likely to be a less useful bioindicator than the previously tested Spirodela. Future research should focus on field applications of Spirodela spp. to test its capacity for sewage-plume mapping of freshwater ecosystems in a natural environment.
- Full Text: false