Biological responses to a resumption in river flow in a freshwater-deprived, permanently open Southern African estuary
- Authors: Vorwerk, Paul D , Froneman, P William , Paterson, Angus W , Strydom, Nadine A , Whitfield, A K
- Date: 2008
- Language: English
- Type: text , Article
- Identifier: vital:6886 , http://hdl.handle.net/10962/d1011645
- Description: The Kariega Estuary is a freshwater-deprived system due to numerous impoundments in the catchment. This system has had little or no horizontal salinity gradient over the last 15 years, with hypersaline conditions sometimes predominating in the upper reaches. Following high rainfall events in the catchment during the spring of 2006, including a flood event (approximate 1:10 year) in August 2006, a series of riverine pulses entered the estuary and a horizontal salinity gradient was established. This study examined the influence of this freshwater pulse on four components of the biota within the estuary, namely the zooplankton, and larval, littoral and demersal fishes. The study demonstrated that in three of these components elevated densities were recorded following the riverine input, with only the littoral fishes retaining an almost constant density. In addition, changes in the relative contributions of the estuarine utilisation classes for all three fish groups examined indicated that freshwater input into these systems positively influences the abundances. This has significant implications for water managers as it demonstrates the importance of an Ecological Reserve (defined as ‘the water required to protect the aquatic ecosystems of the water resource’) for this system.
- Full Text:
- Date Issued: 2008
Recovery of the critically endangered river pipefish, Syngnathus watermeyeri, in the Kariega Estuary, Eastern Cape province
- Authors: Vorwerk, Paul D , Froneman, P William , Paterson, Angus W
- Date: 2007
- Language: English
- Type: text , Article
- Identifier: vital:6965 , http://hdl.handle.net/10962/d1012028
- Description: An intensive ichthyofaunal survey in the permanently open Kariega Estuary along the Eastern Cape coast has identified a breeding population of the critically endangered river pipefish, Syngnathus watermeyeri, within the middle and upper reaches of the system. This is the first recorded capture of this species in the estuary for over four decades. We suggest that the presence of S. watermeyeri is the result of the heavy rainfall within the region, which contributed to the establishment of optimum habitat requirements (mesohaline conditions and increased food availability) of the pipefish.
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- Date Issued: 2007
Rhodes University Graduation Ceremony 1990
- Authors: Rhodes University
- Date: 1990
- Language: English
- Type: text
- Identifier: vital:8124 , http://hdl.handle.net/10962/d1005707
- Description: Rhodes University Graduation Ceremonies on Friday, 6 April 1990 at 8 p.m. [and] on Saturday, 7 April 1990 at 10 a.m. in the 1820 Settlers National Monument. , Rhodes University East London Graduation Ceremony Saturday; 12 May 1990 at 11.30 a.m. in the Guild Theatre.
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- Date Issued: 1990
Rhodes University Graduation Ceremony 1991
- Authors: Rhodes University
- Date: 1991
- Subjects: Relly, Gavin Walter Hamilton
- Language: English
- Type: text
- Identifier: vital:8125 , http://hdl.handle.net/10962/d1006750 , Relly, Gavin Walter Hamilton
- Description: Rhodes University Graduation Ceremonies Friday, 12 April 1991 at 8 p.m. [and] Saturday, 13 April 1991 at 10 a.m. in the 1820 Settlers National Monument. , Rhodes University East London Graduation Ceremony Saturday, 18 May 1991 at 10.00 a.m. in the Guild Theatre. , The Installation of Gavin Walter Hamilton Relly as Chancellor of Rhodes University to be followed by a Graduation Ceremony Friday, 12 April 1991 at 10 a.m. in the 1820 Settlers National Monument.
- Full Text:
- Date Issued: 1991
Rhodes University Graduation Ceremony 1972
- Authors: Rhodes University
- Date: 1972
- Language: English
- Type: text
- Identifier: vital:8106 , http://hdl.handle.net/10962/d1004561
- Description: Rhodes University Graduation Ceremonies on Friday 7th April 1972 at 8 p.m. [and] on Saturday 8th April 1972 at 10:30 a.m. in the University Great Hall.
- Full Text:
- Date Issued: 1972
Biological control of cactaceae in South Africa
- Authors: Paterson, Iain D , Klein, Hildegard , Muskett, Phillippa C , Griffith, Tamzin C , Mayonde, Samalesu , Mofokeng, Kedibone , Mnqeta, Zezethu , Venter, Nic
- Date: 2021
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/${Handle} , vital:71034 , xlink:href="https://hdl.handle.net/10520/ejc-ento_v29_n3_a4"
- Description: Cactaceae are among the most problematic invasive alien plants in South Africa, posing serious negative consequences to agriculture and natural ecosystems. Fortunately, South Africa has a long and successful history of controlling cactus weeds using biological control (biocontrol). This paper reviews all the biocontrol programmes against invasive alien Cactaceae in South Africa, focusing on the decade since the last review published in 2011, up to, and including 2020. Biocontrol programmes against 16 target weeds are summarised, all of which rely on either the galling mealybug, Hypogeococcus sp. (Pseudococcidae), or various species or intraspecific lineages of cochineal insects (Dactylopius spp., Dactylopiidae) as agents. New agents are being considered for the three target weed species, Opuntia elata Salm-Dyck, Opuntia megapotamica Arechav. and Trichocereus spachianus (Lem.) Riccob., while permission to release a new agent against Cylindropuntia pallida (Rose) F.M. Knuth has recently been granted. The biocontrol agent, Dactylopius opuntiae (Cockrell) ‘stricta’, which has been utilised for the successful control of Opuntia stricta Haw., has shown some promise as an agent against one of the worst cactus weeds in the country, the North Cape/Free State variety of Opuntia engelmannii Salm-Dyck. Post-release monitoring and recent observations of the status of control for the 11 other cactus weeds, all of which have well-established agents, are provided. Taxonomic uncertainties and misidentifications of both target weeds and agents has been a constraint to biocontrol efforts, but this has been partially overcome through the use of genetic techniques. Biocontrol is particularly successful in controlling cactus weeds compared to most other taxonomic groups, and it is likely that past successes can be repeated with new target weeds. Mass-rearing and redistribution of agents are essential to gain the maximum possible benefit from cactus biocontrol agents, and recent increases in mass-rearing outputs have been beneficial.
- Full Text:
- Date Issued: 2021
The metabolic physiology of early stage Argyrosomus japonicus with insight into the potential effects of pCO2 induced ocean acidification
- Authors: Edworthy, Carla
- Date: 2018
- Subjects: Argyrosomus , Argyrosomus -- Growth , Argyrosomus -- Mortality , Argyrosomus -- Larvae -- Ecology , Ocean acidification , Marine ecology -- South Africa , Carbon dioxide -- Physiological effect
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/51417 , vital:26094
- Description: Ocean acidification is a phenomenon associated with global change and anthropogenic CO2 emissions that is changing the chemistry of seawater. These changes result in elevated pCO2 and reduced pH in seawater and this is impacting marine organisms in various ways. Marine fishes are considered generally tolerant to conditions of ocean acidification; however, these assumptions are based on juvenile and adult fish tolerance and the larval stages have not been frequently assessed. Furthermore, it has been suggested that temperate species, particularly those with an estuarine association, may be tolerant to variable CO2 and pH. This study used an eco-physiological approach to understand how the early life stages of Argyrosomus japonicus, an estuarine dependent marine fisheries species found in warm-temperate regions, may be impacted by ocean acidification. The metabolic response of early stage larvae (hatching to early juvenile stage) was assessed under conditions of elevated pCO2 and reduced pH in a controlled laboratory setting. Small volume static respirometry was used to determine the oxygen consumption rate of larvae raised in three pCO2 treatments including a low (pCO2 = 327.50 ± 80.07 µatm at pH 8.15), moderate (pCO2 477.40 ± 59.46 µatm at pH 8.03) and high treatment (PCO2 910.20 ± 136.45 µatm at pH 7.78). These treatment levels were relevant to the present (low) and projected conditions of ocean acidification for the years 2050 (moderate) and 2100 (high). Prior to experimentation with ocean acidification treatments, baseline metabolic rates and diurnal variation in oxygen consumption rates in early stage A. japonicus was determined. Distinct ontogenetic structuring of metabolic rates was observed in early stage A. japonicus, with no cyclical fluctuations in metabolic rate occurring during the 24 hour photoperiodic cycle. Pre-flexion larvae showed no metabolic response to ocean acidification treatments; however post-flexion stage larvae showed metabolic depression of standard metabolic rate in the moderate (32.5%) and high (9.5%) pCO2 treatments (P = 0.02). Larvae raised in the high pCO2 treatment also showed high levels of mortality with no individuals surviving past the post-flexion stage. Larvae raised in the moderate pCO2 treatment were unaffected. This study concluded that ocean acidification conditions expected for the end of the century will have significant impacts on the metabolism of early stage A. japonicus, which may result in reduced growth, retardation of skeletal development and ultimately survival as a result of increased mortality. Furthermore, the timing of reduced metabolic scope will significantly impact the recruitment ability of A. japonicus larvae into estuarine habitats. This could ultimately impact the sustainability of A. japonicus populations. Most importantly, this study highlighted the need to consider the combined effect of ontogeny and life-history strategy when assessing the vulnerability of species to ocean acidification.
- Full Text:
- Date Issued: 2018
Rhodes University Graduation Ceremony 2002
- Authors: Rhodes University
- Date: 2002
- Language: English
- Type: text
- Identifier: vital:8145 , http://hdl.handle.net/10962/d1007267
- Description: Rhodes University Graduation Ceremonies 1820 Settlers National Monument Friday, 5 April 2002 at 10:30; 14:30 & 18:00 [and] Saturday, 6 April 2002 at 10:30 , Graduation Ceremony Christian Centre, Wyse Street, East London Friday, 10 May 2002 at 18:00
- Full Text:
- Date Issued: 2002
Leadership development within a learner representative council: a Namibian primary school case study
- Authors: Tjihuro, Jaqueline
- Date: 2018
- Subjects: School management and organization Namibia , Educational leadership Namibia , Student participation in administration Namibia , Student government Namibia
- Language: English
- Type: text , Thesis , Masters , MEd
- Identifier: http://hdl.handle.net/10962/61558 , vital:28036
- Description: Learners in Namibian primary schools are seemingly not brave enough to stand and raise their voice on issues that concern them. This is what Shekupakela-Nelulu (2008) wrote after a study she conducted on the Learners’ Representative Council (LRC) of a school in Namibia. She refers to a time when “the involvement of students in school affairs was seen by the regime as a political act and attempts by student leaders to involve themselves in educational issues were often quashed” (ibid., p. i). This situation will be all too familiar to South African readers, where a public holiday, Youth Day, was declared to mark the apartheid regime’s brutal treatment of learner protestors on June 16, 1976. While Namibia has not experienced events of such magnitude, the notion of learner voice is equally problematic and worthy of investigation. The absence of leadership development opportunities for learners has led to this research study which seeks to answer the central research question: How can learner leadership be developed in a LRC? I used an interpretive paradigm, adopting a qualitative approach in the study. Concurrently, the study was framed and guided by the second generation of Cultural Historical Activity Theory (CHAT) as an analytical tool to achieve my research goal. The following questions guided the study in two phases. Phase one: What were the perceived causes for the nonsustainability of the learner leadership (LL) club at the school? Phase two: How is the notion of learner leadership understood in the school? How is leadership developed on the LRC? What enables and constrains leadership development of learners on the LRC? The research participants were thirty LRC members from grades 6 and 7 and15 teachers who teach the LRC members. The principal and three HOD’s were also research participants being part of the Senior Management team. One of the HOD’s also fulfils the role of the guardian teacher to the LRC. A school board chairperson also participated in the Change Laboratory Workshop. Data was generated through multiple data sources such as questionnaires, individual interviews, a focus group interview and observation. The findings from phase one of the study revealed that the learner leadership club’s intervention was a success during the 2014 academic year, but the absence of the learner leadership club as an extra-mural activity affected the sustainability of the club into the next academic year 2015. Findings from phase two revealed that leadership opportunities did exist at the school for learner leadership development. However, a few challenges emerged relating to traditional views of leadership and constraining factors that could affect learner leadership development at the school. Thus, Change Laboratory workshops were held to find solutions to the challenges, in order to promote and enhance learner leadership development, hopefully for the future of the Namibian child.
- Full Text:
- Date Issued: 2018
The use of the cochineal insect, Dactylopius tomentosus Lamarck, as a biological control agent for the invasive alien thistle cholla, Cylindropuntia pallida (Rose) F.M. Knuth in South Africa
- Authors: Zozo, Ekhona
- Date: 2022-04-06
- Subjects: Cochineal insect , Thistles Biological control South Africa , Alien plants South Africa , Invasive plants South Africa , Cactus South Africa , Biological assay
- Language: English
- Type: Master's thesis , text
- Identifier: http://hdl.handle.net/10962/233823 , vital:50131
- Description: Cylindropuntia pallida (Rose) F.M. Knuth (Cactaceae) is an invasive alien plant in South Africa indigenous in the southern U.S.A. and Mexico. Large infestations of this species can be found in the Kalahari and arid Karoo regions of South Africa, which is also present in Namibia. Because it is a very spiny cactus, dense infestations have a negative impact on agriculture and natural ecosystems. This cactus has become naturalised to the extent that eradication is impossible and the negative impacts are steadily increasing due to its increasing distribution and density. The cochineal insect, Dactylopius tomentosus Lamarck (Dactylopiidae), is native in Mexico and parts of North America, such as Texas, Arizona, and New Mexico in the U.S.A. This cochineal species is highly specialized and associated only with Cylindropuntia species, a group of cacti that are primarily restricted to the same areas. It has been introduced into Australia and South Africa as a biological control agent to control various invasive alien Cylindropuntia species. This cochineal species has several biotypes specific to certain Cylindropuntia species hosts. A biotype is a clade that cannot be differentiated morphologically from others but has different host ranges and impacts depending on the host plant species. Included amongst biotypes that have been released in South Africa are D. tomentosus ‘imbricata’ and D. tomentosus ‘cholla’ for the biological control of Cylindropuntia imbricata (Haw.) F.M. Knuth (Cactaceae) and Cylindropuntia fulgida (Engelmann) F.M. Knuth var. mamillata (Schott ex Engelmann) Backeb. (Cactaceae), respectively. These biotypes have resulted in both host plants being under substantial control in South Africa. The first part of this thesis evaluated which of the two D. tomentosus biotypes already in use in South Africa could be an effective biological control agent for C. pallida. This was done by assessing the fitness of the cochineals on the three cactus species and assessing the impact that each of the cochineals has on each of the target weed species. Should these biotypes prove ineffective, there is a third biotype, namely D. tomentosus ‘californica var. parkerii’, which researchers in Australia have worked on and have found to be suitably host-specific for release in Australia and suitably damaging to C. pallida in that country. Therefore, this new biotype could be released in South Africa if it is required. Sexually compatible biological control agents, especially those closely related and occurring in close spatial proximity to one another, may interbreed and the impacts of this hybridisation are difficult to predict. It is important to understand the outcomes of the hybridisation of cochineal because it can affect the impact of the biological control agents and thus the control of the target weed. The second part of this thesis investigated the impacts of the hybridisation of the two cochineal biotypes by assessing the damage the agents would have on the target weed, and on C. imbricata and C. fulgida var. mamillata, in the presence of one or both cochineal biotypes. The ‘cholla’ biotype performed better on C. pallida than the ‘imbricata’ biotype, but neither biotype could control C. pallida to an extent similar to the control they provide for their respective target weeds, C. imbricata and C. fulgida var. mamillata. Both the ‘cholla’ biotype and hybrids of the two biotypes of cochineal were effective at killing C. pallida when both C. imbricata and C. fulgida var. mamillata were also present. This suggests that the ‘cholla’ or hybrids may be effective at controlling C. pallida when either C. imbricata or C. fulgida var. mamillata are also present in the field due to the high population density of cochineal that results under these circumstances. There are, however, many C. pallida infestations in South Africa where the plant is problematic and is isolated from other Cylindropuntia species, and these populations are unlikely to be controlled by the ‘cholla’ biotype or the hybrids. Neither of the cochineal biotypes that are used for biological control in South Africa are suitably damaging to C. pallida to warrant their use as biological control agents for this species. Dactylopius tomentosus ‘californica var. parkerii’ is therefore recommended for release based on its host-specificity and impact to C. pallida in Australia. , Thesis (PhD) -- Faculty of Science, Zoology and Entomology, 2022
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- Date Issued: 2022-04-06
Rhodes University Graduation Ceremony 2001
- Authors: Rhodes University
- Date: 2001
- Language: English
- Type: text
- Identifier: vital:8146 , http://hdl.handle.net/10962/d1007296
- Description: Rhodes University Graduation Ceremonies 1820 Settlers National Monument Friday, 6 April 2001 at 10:30; 18:00 [and] Saturday, 7 April 2001 at 10:30 , Graduation Ceremony Christian Centre, Wyse Street, East London Friday, 1 May 2001 at 18:00
- Full Text:
- Date Issued: 2001
Do submarine canyons influence the structure and diversity of benthic fish assemblages on the continental shelf edge?
- Authors: Nyawo, Mpilonhle Aura June-Rose
- Date: 2020
- Subjects: Submarine valleys , iSimangaliso Wetland Park (South Africa) , Biotic communities -- South Africa -- iSimangaliso Wetland Park , Groundfishes -- South Africa -- iSimangaliso Wetland Park , Marine ecology -- South Africa -- iSimangaliso Wetland Park
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/167264 , vital:41462
- Description: Marine ecosystems play an important role in human welfare, such as providing food security and providing social, economic and environmental benefits to an increasing human population. However, due to the deleterious impact of overfishing as well as habitat degradation, pollution and climate change, many marine ecosystems and the substantial biodiversity they support, are under increasing threats. Submarine canyon ecosystems cut into the continental margin in all our oceans and are considered regions of enhanced diversity, abundance and biomass for many marine communities, including fish. In South Africa, the tropical Delagoa Ecoregion is characterised by numerous submarine canyons that are home to coelacanths Latimeria chalumnae, and a variety of commercially important line fish species. However, there is currently a lack of information on the ecological structure and functioning of these canyons, in relation to nearby non-canyon ecosystems. The aim of this thesis was to generate knowledge on the role of submarine canyons in influencing the benthic fish assemblage structure and diversity on the continental shelf and shelf edge within the high-latitude coral reef ecosystems in the tropical Delagoa Ecoregion of South Africa. First, a systematic literature review was conducted to examine the current knowledge on the role of submarine canyons on the benthic fish assemblages occurring on continental margins, as well as outline the trends in canyon research. For the fieldwork component of this thesis, baited remote underwater stereo-video systems were utilised to gather data. The first research chapter, chapter 3, investigated the effect of ecosystem and depth on the diversity and structure of benthic fish assemblages within iSimangaliso Wetland Park in the Delagoa Ecoregion. Data were collected in 2017 from Wright Canyon (canyon ecosystem) and adjacent slope ecosystems around the canyon (non-canyon ecosystem) at depths ranging between 70–240 m. The second research chapter, chapter 4, data were collected in 2018, from 60–100 m depths in three ubmarine canyons (Wright, Diepgat,Levens) and their adjacent habitat within iSimangaliso Wetland Park to investigate the diversity patterns and community structure of benthic fish and cons ider location as a factor. The systematic review showed that canyon research is still very much in its infancy, however more papers are expected to be published in the future. There were clear location associated biases detected, with more than 90% of the canyon research being concentrated in the Mediterranean Sea, while only one study was published from South Africa. Most of the reviewed literature focused on invertebrates, with benthic fish (including cartilaginous fish) being the second most studied taxa. A wide range of methods from both fishery- dependent and fishery-independent categories were used to gather the data of benthic fish from the canyons and adjacent areas. With over 8500 submarine canyons mapped globally, the number of submarine canyon research published and the detected location bias is of great concern. More studies are needed in order to understand the role of submarine canyons on adjacent slope habitats Overall, the results from the research chapters indicated that there were higher a bundances in the canyon ecosystem compared to the non-canyon ecosystem. In contrast, evenness and beta-diversity were higher in the non-canyon ecosystem. Relief, bottom type as well as depth played a major role in explaining the observed abundance and diversity patterns. Both evenness and beta-diversity decreased with increase in depth. The canyon and non-canyon also differed in terms of habitat structure. The canyon ecosystem was characterised by patched reef and reef habitats with high relief whereas the non-canyon ecosystem was characterised by flats and habitats, especially at shallower depths. Additionally, there were clear differences in terms of the fish community structure between the canyon and the non-canyon ecosystem. The heterogeneous and complex habitats of the canyon ecosystem were typified by species such as Epinephelus poecilonotus, Polysteganus coeruleopunctatus and Chrysoblephus puniceus in comparison to the less complex habitats outside the canyons that were preferred by species such as Lagocephalus sceleratus, and Rhinobatos leucospilus. The different locations sampled demonstrated that the canyon effect was not onsistent at all locations, with varying results detected in the different sample locations. This research demonstrates that clea r differences exists between the benthic fish assemblages associated with canyon and non-canyon ecosystems and provides important information on the role of submarine canyons in the iSimangaliso Wetland Park. From this thesis, it is clear that a ‘canyon effect’ exists in the continental shelf and shelf edge. The results suggested that heterogeneity of habitats was the most important environmental factor that differed between the canyon and non-canyon ecosystems and these differences in the habitat were driving the observed patterns. This thesis has provided a reference point, with regards to investigating the role and influence of these canyons on benthic fish assemblages occurring on the continental shelf edge. The information provided by this thesis can ultimately be used in other studies investigating benthic fish assemblages in other submarine canyons within iSimangaliso Wetland Park and the rest of South Africa./
- Full Text:
- Date Issued: 2020
Rhodes University Graduation Ceremony 1995
- Authors: Rhodes University
- Date: 1995
- Language: English
- Type: text
- Identifier: vital:8129 , http://hdl.handle.net/10962/d1006754
- Description: Rhodes University Graduation Ceremonies Thursday, 20 April 1995 at 8:15 p.m. [and] Friday, 21 April 1995 at 10:30 a.m. [and] 08:15 p.m. [and] Saturday, 22 April 1995 at 10:30 a.m. in the 1820 Settlers National Monument. , Rhodes University East London Graduation Ceremony Saturday, 13 May 1995 at 11.00 a.m. in the Guild Theatre.
- Full Text:
- Date Issued: 1995
Water restriction and vitamin c supplementation on Xhosa goats during summer: Effect on growth performance, blood biochemical profile, nutrient balance, carcass characteristics and meat quality
- Authors: Akinmoladun, Oluwakamisi Festus https://orcid.org/0000-0001-6462-374X
- Date: 2020-08
- Subjects: Goats -- Nutrition , Goats -- Feeding and feeds
- Language: English
- Type: Doctoral theses , text
- Identifier: http://hdl.handle.net/10353/22710 , vital:52664
- Description: This study aimed to evaluate the effect of single and extra vitamin C (VC) supplementation on water-stressed Xhosa goats during the summer by evaluating their growth performance, blood biochemical profile, nutrient balance, carcass characteristics and meat qualities. The objectives were to assess the effect of water restriction and vitamin C supplementation by evaluating: firstly, growth performance, heat tolerance responses, and blood metabolites; secondly, intake, nutrient digestibility, nitrogen and mineral balance; thirdly, stress indices, carcass characteristics and meat qualities parameters and lastly, fatty acid profile, oxidative stability of lipids and sensory attributes were evaluated. To achieve these objectives, forty-two (42) goats were divided equally into seven treatments (75-day trial); without water restriction (W0, control); water restriction of 70percent of ad libitum water intake WI (W70); water restriction of 50percent ad libitum WI (W50); water restriction of 70percent of ad libitum WI plus 3g VC daily (W70+); water restriction 50percent of ad libitum WI plus 3g VC daily (W50+); water restriction of 70percent of ad libitumWI plus 3g VC and extra 5gVC given every eight-day (70++); water restriction of 50percent of ad libitum WI plus 3g VC and extra 5gVC given every eight-day (W50++). In the first objective, growth performance parameters, body condition scores, rectal temperature, respiratory rate, heat tolerance response parameters and blood metabolites were measured.Weight loss due to water restriction was reduced by VC supplementation in treated groups. The attenuation effect of VC was significant (P<0.05) in responses to respiratory rate (RR), Na+, K+, Mg2+, Cl-, Ca2+ and urea. Supplementation of VC (either single or multiple) did not (P>0.05) improve the effect of water restriction on body condition scores (BCs), FAMACHA©, glucose, globulin, alanine aminotransferase (ALT) and high-density lipoprotein (HDL). In the second objective, intake, nutrient digestibility, nitrogen and mineral balance were evaluated. The reduced nutrient intake was similar (P>0.05) irrespective of water restrictions and VC supplementations. Water-restriction levels did not affect nutrient intake/metabolic weight. Retained nitrogen increased with water-restriction levels but not influenced by VC. NH3-N decreased with the levels of water restriction while the pH was similar across the water restricted groups. Supplementation of VC had no effect (P>0.05) on apparent digestibility and digestible nutrients induced by water restriction levels. The amount of Ca, K, Mg retained increased (P<0.05) with water-restriction levels. In the third objective, stress indices, carcass characteristics and meat quality parameters were evaluated. The level of plasma cortisol concentration due to water stress was lessened (P<0.05) by VC. Follicle stimulating hormone (FSH), Luteinizing hormone (LH) and insulin were not affected (P>0.05) by levels of water restriction. The hot and carcass weights were lower (P<0.05) in W70+ and W50+ compared to W70 and W50 respectively. Vitamin C treated goats had higher redness (a*) compared to W70, W50 and W0. The shear force and cooking loss increased (P<0.05) with water restriction levels, while thaw loss, pH45min and pH24h were not affected by water restriction levels. In the final objective, the treatments did not affect (P>0.05) the oxidative stability of lipids (TBARS). The moisture and fat content in the water restricted groups were lower (P<0.05) than W0. The consumer meat sensory appearance decreased (P<0.05) with levels of water restrictions. Regardless of VC concentration and supplementation, vaccenic, and docosahexaenoic acid increased (P<0.05) while linolenic acid decreased as the water restriction levels increased. Nonetheless, treatment did not affect (P>0.05) the saturated and unsaturated fatty acids. These studies showed that suboptimal water intake negatively affects the growth performance and nutrient intake of Xhosa goats. However, the reduction in body weight loss and decreased plasma cortisol (chief stress hormone) concentration following vitamin C supplementation (especially at a daily single dose [3g/d]) may well reduce the effect of water stress in goats. , Thesis (PhD) -- Faculty of Science and Agriculture, 2020
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- Date Issued: 2020-08
Rhodes University Graduation Ceremony 2016
- Authors: Rhodes University
- Date: 2016
- Language: English
- Type: text
- Identifier: vital:8150 , http://hdl.handle.net/10962/d1021288
- Description: Rhodes University Graduation Ceremonies 2016 [at] 1820 Settlers National Monument Thursday, 31 March at 10.00 & 17:00 [and] Friday, 1 April at 10:00; 14:30 & 18:30 [and] Saturday, 2 April at 10:00
- Full Text:
- Date Issued: 2016
Potential impact and host range of Pereskiophaga brasiliensis Anderson (Curculionidae): a new candidate biological control agent for the control of Pereskia aculeata Miller (Cactaceae) in South Africa
- Authors: Mdodana, Lumka Anita
- Date: 2018
- Subjects: Curculionidae -- South Africa , Cactus -- South Africa , Biological pest control agents , Alien plants-- South Africa , Pereskiophaga brasiliensis Anderson (Curculionidae) , Pereskia aculeata Miller (Cactaceae)
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/62350 , vital:28157
- Description: Pereskia aculeata Miller (Cactaceae) is a damaging invasive alien plant in South Africa that has negative impacts to indigenous biodiversity and ecosystem functioning. Mechanical and chemical control are not effective against P. aculeata so biological control is considered the only viable option. Two biological control agents, the leaf-feeding beetle Phenrica guerini Bechyne (Chrysomelidae) and the stem-wilting bug Catorhintha schaffneri (Coreidae), have been released in South Africa thus far. Post-release evaluations have indicated that P. guerini will not reduce P. aculeata densities to acceptable levels alone, while C. schaffneri was released very recently, so it is too soon to determine how effective that agent will be. Even if C. schaffneri is extremely damaging, it is likely that further agents will be required to reduce the densities of P. aculeata to acceptable levels within a reasonable time-scale. Additional agents should target the woody stems of P. aculeata which are not impacted by the damage of either of the released agents. Pereskiophaga brasiliensis Anderson (Curculionidae) is a promising potential candidate agent that feeds on the thick woody stems of the plant in the larval stage. Climatic matching, genetic matching and field based host specificity observations all indicated that P. brasiliensis was a promising candidate. In this study, the impact of P. brasiliensis to the target weed, P. aculeata, was quantified under quarantine conditions to determine whether it was sufficiently damaging to warrant release. This was followed by host specificity testing to determine whether P. brasiliensis was suitably host specific for release in South Africa. Impact studies indicated that P. brasiliensis was damaging to P. aculeata at insect densities that would be expected in the field. Pereskiophaga brasiliensis reduced the number of leaves of P. aculeata to a greater extent than it reduced shoot lengths, but both plant parameters were significantly reduced due to the feeding damage from the insect. This suggests that the damage from P. brasiliensis may be compatible with that of C. schaffneri which reduces shoot length to a greater degree than the number of leaves. Pereskiophaga brasiliensis is therefore sufficiently damaging to warrant release, and although interaction studies with the other agents would be required, it is expected that it should complement other existing agents. Although P. brasiliensis is sufficiently damaging, at present the host specificity data indicates that it is not suitably specific for release in South Africa because oviposition and larval development to the adult stage was recorded on both indigenous and alien plant species within the families Cactaceae and Basellaceae. This non-target feeding was recorded during no-choice tests, which are very conservative, but significant non-target damage and development to the adult stage was recorded on an indigenous plant from a different family to the target weed. Further host specificity testing, including paired and multiple choice tests, are required to confirm the broad host range of P. brasiliensis. Other biological control agents that damage the woody stems of P. aculeata should be considered. The stem-borer, Acanthodoxus machacalis (Cerambycidae) is considered the most promising of the other candidate agents as it can be sourced from a climatically matched region where genetically suitable P. aculeata plants are found, it is sufficiently damaging to the woody stems of P. aculeata and there is no evidence that the species has a broad host range. Acanthodoxus machacalis should be sourced from Rio de Janeiro, Brazil, and imported into quarantine in South Africa for host specificity testing.
- Full Text:
- Date Issued: 2018
Rhodes University Graduation Ceremony 1961
- Authors: Rhodes University
- Date: 1961
- Language: English
- Type: text
- Identifier: vital:8095 , http://hdl.handle.net/10962/d1004410
- Description: Rhodes University Graduation Ceremonies in the University Great Hall on Saturday , 8th April, 1961, at 11 a.m. [and] Saturday , 22nd April, 1961, at 11 a.m.
- Full Text:
- Date Issued: 1961
Know thy enemy: Investigating genetic contributions from putative parents of invasive Nymphaea mexicana hybrids in South Africa as part of efforts to develop biological control
- Authors: Reid, Megan K , Paterson, Iain D , Coetzee, Julie A , Gettys, Lyn A , Hill, Martin P
- Date: 2023
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/423540 , vital:72070 , xlink:href="https://doi.org/10.1016/j.biocontrol.2023.105291"
- Description: Hybridisation of alien invasive plants complicates efforts to develop biological control, because variations in the genetic makeup of the target plant can impact the survival of host specific agents that have evolved adaptations specific to the original host. To maximise the likelihood of success in a biological control program, potential agents should therefore be collected from populations in the region of origin that are genetically similar to plants in the invaded range. Molecular markers are useful tools to understand genetic contributions in hybrid populations, especially where morphological differentiation is difficult. Nymphaea mexicana Zuccarini (Nymphaeaceae) is an invasive alien plant in South Africa that is being targeted for biological control, but hybrids with intermediate morphological traits are also present at several sites. In this study, ISSR (inter simple sequence repeats) and ITS (internal transcribed spacer) markers were used to determine which Nymphaea species are likely to be putative parents of these hybrids, and morphological characters were also investigated to determine if genetic and morphological traits matched. Two major hybrid groups were identified, with one group clustering with Nymphaea odorata Aiton and the other clustering with Nymphaea alba L. A third, smaller group clustered with Nymphaea tetragona Georgi, whereas the remaining samples clustered with pure N. mexicana from the native range. Morphological features agreed with deductions drawn from molecular data. These results allow us to focus efforts to find compatible biological control agents and better understand the complicated genetic structure of N. mexicana and Nymphaea hybrids in South Africa.
- Full Text:
- Date Issued: 2023
The biological control of aquatic weeds in South Africa: current status and future challenges
- Authors: Hill, Martin P , Coetzee, Julie A
- Date: 2017
- Language: English
- Type: article , text
- Identifier: http://hdl.handle.net/10962/59909 , vital:27706 , https://doi.org/10.4102/abc.v47i2.2152
- Description: Aquatic ecosystems in South Africa have been prone to invasion by introduced macrophytes since the late 1800s, when water hyacinth, Eichhornia crassipes (Mart.) Solms-Laub. (Pontederiaceae), was first recorded as naturalised in KwaZulu-Natal (Cilliers 1991). Several other species of freshwater aquatic plants, all notorious weeds in other parts of the world, have also become invasive in many of the rivers, man-made impoundments, lakes and wetlands of South Africa (Hill 2003). These are Pistia stratiotes L. (Araceae) (water lettuce); Salvinia molesta D.S. Mitch. (Salviniaceae) (salvinia); Myriophyllum aquaticum (Vell. Conc.) Verd. (parrot's feather); and Azolla filiculoides Lam. (Azollaceae) (red water fern) (Hill 2003), which along with water hyacinth comprise the 'Big Bad Five' (Henderson & Cilliers 2002). Recently, new invasive aquatic plant species have been recorded which are still at their early stages of invasion, including the submerged species, Egeria densa Planch. (Hydrocharitaceae) (Brazilian water weed) and Hydrilla verticillata (L.f.) Royle (Hydrocharitaceae); the emergent species, Sagittaria platyphylla (Engelm.) J.G.Sm. and S. latifolia Willd. (Alismataceae); Lythrum salicaria L. (Lythraceae) (purple loosestrife), Nasturtium officinale W.T. Aiton. (Brassicaceae) (watercress); Iris pseudacorus L. (Iridaceae) (yellow flag); and Hydrocleys nymphoides (Humb. & Bonpl. ex Willd.) Buchenau (Alismataceae) (water poppy); and the new floating weeds, Salvinia minima Baker (Salviniaceae) and Azolla cristata Kaulf. (Azollaceae) (Mexican azolla); and the rooted floating Nymphaea mexicana Zucc. (Nymphaeceae) (Mexican water lily) (Coetzee et al. 2011a; Coetzee, Bownes & Martin 2011b). The mode of introduction of these species is mainly through the horticultural and aquarium trade (Martin & Coetzee 2011), and two issues contribute to the invasiveness of these macrophytes following establishment: the lack of co-evolved natural enemies in their adventive range (McFadyen 1998); and disturbance, the presence of nitrate- and phosphate-enriched waters, associated with urban, agricultural and industrial pollution that promotes plant growth (Coetzee & Hill 2012).
- Full Text:
- Date Issued: 2017
Rhodes University Graduation Ceremony 2006
- Authors: Rhodes University
- Date: 2006
- Language: English
- Type: text
- Identifier: vital:8141 , http://hdl.handle.net/10962/d1007254
- Description: Rhodes University Graduation Ceremonies [at] 1820 Settlers National Monument Thursday, 6 April 2006 at 18.00 [and] Friday, 7 April 2006 at 10:30; 14:30 & 18:00 [and] Saturday, 8 April 2006 at 10:30 , Inauguration Ceremony [of] Dr Saleem Badat [as] Principal and Vice-Chancellor [at the] 1820 Settlers National Monument [on] Wednesday, 27 September 2006 at 18:15.
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- Date Issued: 2006