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Bee-hawking by the wasp, Vespa velutina, on the honeybees Apis cerana and A. mellifera

- Tan, K, Radloff, Sarah E, Li, J J, Hepburn, H Randall, Yang, Ming-Xian, Zhang, L J, Neumann, Peter

Authors: Tan, K , Radloff, Sarah E , Li, J J , Hepburn, H Randall , Yang, Ming-Xian , Zhang, L J , Neumann, Peter
Date: 2007
Language: English
Type: text , Article
Identifier: vital:6941 , http://hdl.handle.net/10962/d1011965
Description: The vespine wasps, Vespa velutina, specialise in hawking honeybee foragers returning to their nests. We studied their behaviour in China using native Apis cerana and introduced A. mellifera colonies. When the wasps are hawking, A. cerana recruits threefold more guard bees to stave off predation than A. mellifera. The former also utilises wing shimmering as a visual pattern disruption mechanism, which is not shown by A. mellifera. A. cerana foragers halve the time of normal flight needed to dart into the nest entrance, while A. mellifera actually slows down in sashaying flight manoeuvres. V. velutina preferentially hawks A. mellifera foragers when both A. mellifera and A. cerana occur in the same apiary. The pace of wasp-hawking was highest in mid-summer but the frequency of hawking wasps was three times higher at A. mellifera colonies than at the A. cerana colonies. The wasps were taking A. mellifera foragers at a frequency eightfold greater than A. cerana foragers. The final hawking success rates of the wasps were about three times higher for A. mellifera foragers than for A. cerana. The relative success of native A. cerana over European A. mellifera in thwarting predation by the wasp V. velutina is interpreted as the result of co-evolution between the Asian wasp and honeybee, respectively.
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Date Issued: 2007

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Behavioural observations of the common octopus Octopus vulgaris in Baía dos Tigres, southern Angola

- de Beer, Chénelle L, Potts, Warren M

Authors: de Beer, Chénelle L , Potts, Warren M
Date: 2013
Language: English
Type: text , article
Identifier: http://hdl.handle.net/10962/123233 , vital:35419 , https://doi.org/10.2989/1814232X.2013.847496
Description: The common octopus Octopus vulgaris (Cuvier 1797) is a shallow-water cephalopod species that inhabits coastal rocky areas or reefs. It is the most studied and widely distributed species in its genus. This species has a short lifespan and a rapid growth rate of over 5% of body weight per day (García and Valverde 2006, Ibáñez and Keyl 2010). It is semelparous, with females laying large strings of eggs that they attach to the substrata in their dens (Hernández- García et al. 2002). There is a paucity of information on the preferred habitat and behaviour of O. vulgaris in its natural environment (Anderson 1997, Meisel et al. 2006). The species has been classified as highly mobile, yet resident individuals may exhibit high levels of territoriality. Its mobility allows it to move efficiently between a wide range of suitable habitats (Katsanevakis and Verriopoulos 2004). Octopus make use of both tactile and visual senses to forage, feed and seek suitable shelter (Forsythe and Hanlon 1997, Carvalho and Sousa Reis 2003, Rodríguez-Rúa et al. 2005). They are active feeders that seek out prey such as crustaceans, sessile molluscs and small fish (Forsythe and Hanlon 1997, Boyle and Rodhouse 2005), as well as their smaller conspecifics (Ibáñez and Keyl 2010). The majority of behavioural ecology studies on octopus have been on captive individuals. However, the activity patterns (Mather 1988), foraging strategies and aspects of the movement behaviour (Mather and O’Dor 1991) of juvenile O. vulgaris in the wild were described for an exploited population in Bermuda. Because intertidal octopus stocks are exploited by recreational, subsistence and artisanal fisheries (e.g. Oosthuizen and Smale 2003, Sauer et al. 2011), there are few opportunities to study the behavioural ecology of unexploited populations. An opportunity arose to study various behavioural patterns in an unexploited population in Baía dos Tigres, a large (~200 km2) coastal embayment situated on an isolated stretch of the southern Angolan coast (Figure 1). This study provides information on the population size structure, aspects of the movement behaviour, activity patterns and foraging strategies of O. vulgaris in this largely unstudied coastal embayment.
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Date Issued: 2013

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Beyond the threshold: explorations of liminality in literature. A book review

- Dass, Minesh

Authors: Dass, Minesh
Date: 2013
Language: English
Type: text , article
Identifier: http://hdl.handle.net/10962/142520 , vital:38087 , DOI: 10.1080/10131752.2013.783395
Description: Beyond the Threshold: Explorations of Liminality in Literature, an edited collection of essays, is the culmination of research project on liminality done under the title “Poetics of boundaries and Hybridity”. This venture was undertaken in what is now known as the Research Unit Languages and Literature in the South African Context at North-West University. Some of the articles were initially presented at a conference on “Hybridity, Liminality and Boundaries” which was held in Potchefstroom from 30 June to 2 July 2005. Furthermore, shorter versions of some chapters have already been published in a special edition of Literator (Vol. 27. 1).
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Date Issued: 2013

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Cleaning fouled membranes using sludge enzymes

- Melamane, Xolisa L, Pletschke, Brett I, Leukes, Wintson D, Whiteley, Chris G

Authors: Melamane, Xolisa L , Pletschke, Brett I , Leukes, Wintson D , Whiteley, Chris G
Date: 2003
Language: English
Type: text
Identifier: vital:6480 , http://hdl.handle.net/10962/d1006242
Description: Maintenance of membrane performance requires inevitable cleaning or "defouling" of fouled membranes. Membrane cleaning using sludge enzymes, was investigated by first characterising ostrich abattoir effluent for potential foulants, such as lipids, proteins and polysaccharides. Static fouling of polysulphone membranes using abattoir effluent was also performed. Biochemical analysis was performed using quantitative and qualitative methods for detection of proteins on fouled and defouled membranes. The ability of sulphidogenic proteases to remove proteins adsorbed on polysulphone membranes and capillary ultrafiltration membranes after static fouling, and ability to restore permeate fluxes and transmembrane pressure after dynamic fouling was also investigated. Permeate volumes were analysed for protein and amino acids concentrations. The abattoir effluent contained 553 μg/ml of lipid, 301 μg/ml of protein, 141 μg/ml of total carbohydrate, and 0.63 μg/ml of total reducing sugars. Static fouled membranes removed 23.4percent of proteins. Defouling of dynamically fouled capillary ultrafiltration membranes using sulphidogenic proteases was successful at pH 10, 37°C, within 1 h. Sulphidogenic protease activity was 2.1 U/ml and Flux Recovery (FR percent) was 64 percent.
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Date Issued: 2003

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Climate change, genetics or human choice: why were the shells of mankind’s earliest ornament larger in the Pleistocene than in the Holocene?

- Teske, Peter R, Papadopoulos, Isabelle, McQuaid, Christopher D, Newman, Brent K, Barker, Nigel P

Authors: Teske, Peter R , Papadopoulos, Isabelle , McQuaid, Christopher D , Newman, Brent K , Barker, Nigel P
Date: 2007
Language: English
Type: Article
Identifier: vital:6952 , http://hdl.handle.net/10962/d1011984
Description: The southern African tick shell, Nassarius kraussianus (Dunker, 1846), has been identified as being the earliest known ornamental object used by human beings. Shell beads dated from ~75,000 years ago (Pleistocene era) were found in a cave located on South Africa's south coast. Beads made from N. kraussianus shells have also been found in deposits in this region dating from the beginning of the Holocene era (<10,000 years ago). These younger shells were significantly smaller, a phenomenon that has been attributed to a change in human preference. We investigated two alternative hypotheses explaining the difference in shell size: a) N. kraussianus comprises at least two genetic lineages that differ in size; b) the difference in shell size is due to phenotypic plasticity and is a function of environmental conditions. To test these hypotheses, we first reconstructed the species' phylogeographic history, and second, we measured the shell sizes of extant individuals throughout South Africa. Although two genetic lineages were identified, the sharing of haplotypes between these suggests that there is no genetic basis for the size differences. Extant individuals from the cool temperate west coast had significantly larger shells than populations in the remainder of the country, suggesting that N. kraussianus grows to a larger size in colder water. The decrease in fossil shell size from Pleistocene to Holocene was likely due to increased temperatures as a result of climate change at the beginning of the present interglacial period. We hypothesise that the sizes of N. kraussianus fossil shells can therefore serve as indicators of the climatic conditions that were prevalent in a particular region at the time when they were deposited. Moreover, N. kraussianus could serve as a biomonitor to study the impacts of future climate change on coastal biota in southern Africa.
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Date Issued: 2007

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Complexes of zinc, cadmium and mercury with primary aromatic amines

- Haigh, John M, Van Dam, M A, Thornton, D A

Authors: Haigh, John M , Van Dam, M A , Thornton, D A
Date: 1967
Language: English
Type: Article
Identifier: vital:6369 , http://hdl.handle.net/10962/d1006070
Description: We have examined the infrared spectra of thirty-seven complexes derived from the reaction of zinc chloride, mercuric chloride and cadmium chloride, bromide and iodide with several primary aromatic amines. The object of the study was to ascertain whether the frequency data would shed light on the mechanisms of metal-donor atom bonding and electron shifts within the molecules and, in the case of the cadmium complexes, in order to obtain evidence for the transmission of electronic effects through a cadmium atom.
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Date Issued: 1967

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Consideration of the effect of nutritional status and disease patterns on the work output amongst Black South African workers involved in manual materials handling (MMH) tasks

- Christie, Candice J

Authors: Christie, Candice J
Date: 2001
Language: English
Type: Article
Identifier: vital:6746 , http://hdl.handle.net/10962/d1009315
Description: The prevalence of malnutrition amongst low-income earning South Africans has been well documented and is reported to be particularly high amongst Black South African males. This, combined with poor living conditions associated with their poor socio-economic status, results in an increased prevalence of infectious diseases amongst this sector of the population. Additionally, Black South African males are most often employed by companies requiring them to carry out heavy manual materials handling tasks. It would appear that limited research has focused on the relationship between inadequate dietary intake combined with poor health status and the impact this may have on the performance of manual workers. Energy intake is in all probability considerably less than energy expenditure.
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Date Issued: 2001

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COSATU press statement on the CEC decisions

- COSATU

Authors: COSATU
Date: May 1998
Subjects: COSATU
Language: English
Type: text
Identifier: http://hdl.handle.net/10962/109730 , vital:33184
Description: The COSATU Central Executive Committee met in its first session of the year over two days (5-6May 1998). The CEC received reports on a variety of issues and tool a number of policy decisions and approaches by on these matters. The CEC was characterised by anger and frustration on the scale of job losses in many industries and the failure of the current macro economic strategies to turn this tide around. Below are some of the issues discussed. The CEC endorsed the proposals submitted by Labour in NEDLAC on job 4^ creation in preparation for the Presidential Job Summit. The proposals will be further discussed in the coming Central Committee of COSATU scheduled for the 23-35 June 1998. COSATU shall use the Central Committee to further expand on the broad framework submitted in NEDLAC and get more proposals in line with how labour has categorised issues for the agenda of the Job Summit, i.e. (i) Measures to create jobs (ii) Measures to stop current job losses (iii) Measures to support the unemployed, (iv) Measures to assist the informal sector to be formal (v) Identification of long term issues to be negotiated beyond the Job Summit. COSATU is extremely concerned by the failure of both government and business to submit their proposals at NEDLAC. It is worth to note that various deadlines for them to submit proposals have passed. A million-dollar question is : Why does the government and business seem reluctant to submit their proposals? Clearly both government and business have abundance of capacity to deal with the proposals in a relatively short space of time. This is a major concern for COSATU. Whilst the delays continue, job losses are continuing unabated and the time bomb continue to click.
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Date Issued: May 1998

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Critical media literacy: a design for the future

- Prinsloo, Jeanne

Authors: Prinsloo, Jeanne
Date: 2006
Language: English
Type: text , Article
Identifier: vital:6331 , http://hdl.handle.net/10962/d1008476
Description: [From OPENSPACE Editor Alice Kanengoni's editorial]: Professor Jeanne Prinsloo notes in her article that "In fact, it has been argued that the significance of the media in people’s lives has increased to the extent that it has been described as their primary curriculum, thereby recasting formal education as the secondary curriculum." This therefore requires an incestment in media literacy; people's ability to to understand the world around them, as represented in the media. Thus, Professor Prinsloo argues for critical media literacy, citing the role that the media played in fuelling the genocide in Rwanda, as an illustrative case in point. She states that "While we can not attribute all blame in the Rwandan scenario to the radio use, it is clear that the media mattered." She indicates that "media representations and engagements play a significant role in the way we understand the world, its people and events, and ourselves therein." As such, societies should invest in building a critical citizenry that can read and deconstruct the various ideologies that are often carries in and through the media.
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Date Issued: 2006

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Cross-cultural communication in a north-eastern Cape farming community:

- Kaschula, Russell H

Authors: Kaschula, Russell H
Date: 1989
Language: English
Type: text , article
Identifier: http://hdl.handle.net/10962/175313 , vital:42564 , https://doi.org/10.1080/02572117.1989.10586786
Description: Cross-cultural communication is dealt with and more specifically, the communicative competence of 15 white English-speaking farmers when they speak Xhosa to their labourers is assessed. This research was conducted in the Elliot, Ugie, and Maclear areas of the north-eastern Cape. A broad sociolinguistic framework drawing on both ethnographic and ethnomethodological principles was used; complications caused by cross-cultural differences which are reflected in language, and which may lead to possible communication breakdown, were isolated. The actual analysis of speech in terms of ethnomethodological principles, such as turn-taking and the co-operative principle, was undertaken.
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Date Issued: 1989

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Cytotoxic activity of marine sponge extracts from the sub-Antarctic Islands and the Southern Ocean

- Olsen, Elisabeth, De Cerf, Christopher, Dziwornu, Godwin, Puccinelli, Eleonora, Parker-Nance, Shirley, Ansorge, Isabelle J, Samaai, Toufiek, Dingle, Laura, Edkins, Adrienne L, Sunassee, Suthananda N

Authors: Olsen, Elisabeth , De Cerf, Christopher , Dziwornu, Godwin , Puccinelli, Eleonora , Parker-Nance, Shirley , Ansorge, Isabelle J , Samaai, Toufiek , Dingle, Laura , Edkins, Adrienne L , Sunassee, Suthananda N
Date: 2016
Language: English
Type: text , article
Identifier: http://hdl.handle.net/10962/66300 , vital:28931 , https://doi.org/10.17159/sajs.2016/20160202
Description: publisher version , Over the past 50 years, marine invertebrates, especially sponges, have proven to be a valuable source of new and/or bioactive natural products that have the potential to be further developed as lead compounds for pharmaceutical applications. Although marine benthic invertebrate communities occurring off the coast of South Africa have been explored for their biomedicinal potential, the natural product investigation of marine sponges from the sub-Antarctic Islands in the Southern Ocean for the presence of bioactive secondary metabolites has been relatively unexplored thus far. We report here the results for the biological screening of both aqueous and organic extracts prepared from nine specimens of eight species of marine sponges, collected from around Marion Island and the Prince Edward Islands in the Southern Ocean, for their cytotoxic activity against three cancer cell lines. The results obtained through this multidisciplinary collaborative research effort by exclusively South African institutions has provided an exciting opportunity to discover cytotoxic compounds from sub-Antarctic sponges, whilst contributing to our understanding of the biodiversity and geographic distributions of these cold-water invertebrates. Therefore, we acknowledge here the various contributions of the diverse scientific disciplines that played a pivotal role in providing the necessary platform for the future natural products chemistry investigation of these marine sponges from the sub- Antarctic Islands and the Southern Ocean. Significance: This study will contribute to understanding the biodiversity and geographic distributions of sponges in the Southern Ocean. This multidisciplinary project has enabled the investigation of marine sponges for the presence of cytotoxic compounds. Further investigation will lead to the isolation and identification of cytotoxic compounds present in the active sponge extracts. , University of Cape Town; South African Medical Research Council; National Research Foundation (South Africa); CANSA; Rhodes University; Department of Science and Technology; Department of Environmental Affairs; SANAP
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Date Issued: 2016

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