Scielo RSS http://www.scielo.org.za/rss.php?pid=0038-235320090002&lang=es vol. 105 num. 3-4 lang. es http://www.scielo.org.za/img/en/fbpelogp.gif http://www.scielo.org.za http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0038-23532009000200001&lng=es&nrm=iso&tlng=es http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0038-23532009000200002&lng=es&nrm=iso&tlng=es http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0038-23532009000200003&lng=es&nrm=iso&tlng=es http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0038-23532009000200004&lng=es&nrm=iso&tlng=es http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0038-23532009000200005&lng=es&nrm=iso&tlng=es http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0038-23532009000200006&lng=es&nrm=iso&tlng=es http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0038-23532009000200007&lng=es&nrm=iso&tlng=es http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0038-23532009000200008&lng=es&nrm=iso&tlng=es http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0038-23532009000200009&lng=es&nrm=iso&tlng=es South Africa uniquely lies at the junction of two major currents, the Agulhas and the Benguela. The waters overlying the continental shelf exhibit exceptionally high short-, medium- and long-term (days to inter-decadal) variability compared with most other shelf areas, and strongly contrasting oceanographic conditions are observed on the east and west coasts. South Africa is rich in fisheries resources and associated environmental data collected over more than a century. The South African marine scientific community has a history of multidisciplinary studies of marine foodwebs, from the driving forces such as wind, currents and solar heating, to the top predators, with the development of kelp bed, sub-tidal reefs and estuarine ecosystem studies in the 1970s; the Benguela Ecology Programme, which ran through four successive five-year stages, focused on the pelagic marine resources. Various approaches have been used to observe the continental shelf at different time and space scales, including: macroscale but frequent satellite imagery, mesoscale environmental and fishery surveys, dedicated cross-shelf transects in key areas, measurements of dynamic processes, use of moored buoys and coastal weather stations, and integrated monitoring approaches, including modelling and simulation studies. Between 30 and 50 years of comprehensive marine data now exist, which are proving useful in the application of an ecosystem approach to fisheries monitoring and management, as decadal changes become discernible. These observations need to continue; even though the single-species stock assessment and operational management procedures have not yet formally used environmental factors for fisheries management advice, they help us to understand the factors affecting fish population fluctuations and early life histories and to identify large-scale regime shifts where marine trophic structure and functioning alter to a new state. http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0038-23532009000200010&lng=es&nrm=iso&tlng=es This review article describes the nature of the soybean rust pathogen, its interaction with the soybean host and documents some of the history of soybean rust in South Africa. Soybean rust has affected soybean cropping in parts of South Africa since 2001. The disease causes leaf lesions, which may progress to premature defoliation and ultimately result in grain yield loss in susceptible soybean genotypes. Chemical control measures have been successfully employed to limit commercial yield losses in South Africa; however, controlling the effects of this disease through host-resistance or tolerance mechanisms remains a long-term goal. http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0038-23532009000200011&lng=es&nrm=iso&tlng=es Gene flow between related plant species, and between transgenic and non-transgenic crop varieties, may be considered a form of biological invasion. Brassica napus (oilseed rape or canola) and its relatives are well known for intra- and inter-specific gene flow, hybridisation and weediness. Gene flow associated with B. napus poses a potential ecological risk in the Fynbos Biome of South Africa, because of the existence of both naturalised (alien, weedy) and native relatives in this region. This risk is particularly pertinent given the proposed use of B. napus for biofuel and the potential future introduction of herbicide-tolerant transgenic B. napus. Here we quantify the presence and co-occurrence of B. napus and its wild and weedy relatives in the Fynbos Biome, as a first step in the ecological risk assessment for this crop. Several alien and at least one native relative of B. napus were found to be prevalent in the region, and to be spatially congruent with B. napus fields. The first requirement for potential gene flow to occur has thus been met. In addition, a number of these species have elsewhere been found to be reproductively compatible with B. napus. Further assessment of the potential ecological risks associated with B. napus in South Africa is constrained by uncertainties in the phylogeny of the Brassicaceae, difficulties with morphology-based identification, and poor knowledge of the biology of several of the species involved, particularly under South African conditions. http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0038-23532009000200012&lng=es&nrm=iso&tlng=es The interaction of metals and biological materials is of interest for reasons such as metal recovery, toxicity and production of high-value products such as gold and platinum nanoparticles. Understanding the way in which metals interact with the biomass surface and intracellular components provides insights into the biosorption and bioaccumulation processes and increases the potential for process optimisation. Three technologies are available for the qualitative visualisation of metal-biomass interactions in South Africa, namely, micro-PIXE, transmission electron microscopy and scanning electron microscopy coupled with energy-dispersive analysis of X-rays. Each technique provides unique information and has specific shortcomings which should be taken into account when selecting the appropriate technology. This paper focuses on evaluating the various techniques. http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0038-23532009000200013&lng=es&nrm=iso&tlng=es W Ursae Majoris (W UMa)-type variable stars are over-contact eclipsing binary stars. To understand how these systems form and evolve requires observations spanning many years, followed by detailed models of as many of them as possible. The All Sky Automated Survey (ASAS) has an extensive database of these stars. Using the ASAS V band photometric data, models of W UMa-type stars are being created to determine the parameters of these stars. This paper discusses the classification of eclipsing binary stars, the methods used to model them as well as the results of the modelling of ASAS 120036-3915.6, an over-contact eclipsing binary star that appears to be changing its period. http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0038-23532009000200014&lng=es&nrm=iso&tlng=es A population of Anopheles arabiensis, a major malaria vector in South Africa, was collected during 2005 from inside sprayed houses in Mamfene, northern KwaZulu-Natal, South Africa, using window exit traps. None of these specimens (n = 300 females) was found to be infected with Plasmodium falciparum. Insecticide susceptibility assays on 2-3 day old F1 progeny using WHO susceptibility kits revealed 100% susceptibility to bendiocarb, resistance to deltamethrin (95.91%) was suspected, while resistance to permethrin (78.05%) was confirmed. The knockdown resistant (kdr) genotype was not found in the surviving mosquitoes. Biochemical analysis using enzyme assays showed elevated levels of monooxygenase that correlated with the permethrin bioassay data. While elevated levels of non-specific esterase were found in some families (11/12 for α- and 6/12 for β-esterases), the data did not show any correlation with the permethrin bioassay. Analysis of permethrin and bendiocarb tolerant lines, selected in the laboratory to characterise biochemical resistance profiles, showed increased levels of non-specific esterase and monooxygenase activity in the case of the permethrin-selected cohorts, and elevated glutathione S-transferases and general esterases in that of the bendiocarb-selected line. Synergist assays, using piperonyl butoxide, confirmed the involvement of monooxygenase and glutathione S-transferase in pyrethroid and bendiocarb resistance. This study underlines the importance of routine surveillance for insecticide susceptibility in wild anopheline populations. http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0038-23532009000200015&lng=es&nrm=iso&tlng=es Modern breeding practices strive to achieve distinctive phenotypic uniformity in breeds of dogs, but these strategies are associated with the inevitable loss of genetic diversity. Thus, in parallel with the morphological variation displayed by breeds, purebred dogs commonly express genetic defects as a result of the inbreeding associated with artificial selection and the reduction of selection against disease phenotypes. Microsatellite marker analyses of 15 polymorphic canine loci were used to investigate measures of genetic diversity and population differentiation within and between German-bred and South African-bred German shepherd dogs. These data were quantified by comparison with typically outbred mongrel or crossbred dogs. Both the imported and locally-bred German shepherd dogs exhibited similar levels of genetic diversity. The breed is characterised by only a moderate loss of genetic diversity relative to outbred dogs, despite originating from a single founding sire and experiencing extensive levels of inbreeding throughout the history of the breed. Non-significant population differentiation between the ancestral German and derived South African populations indicates sufficient contemporary gene flow between these populations, suggesting that migration resulting from the importation of breeding stock has mitigated the effects of random genetic drift and a population bottleneck caused by the original founder event in South Africa. Significant differentiation between the combined German shepherd dog population and the outbred dogs illustrates the effects of selection and genetic drift on the breed since its establishment just over 100 years ago. http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0038-23532009000200016&lng=es&nrm=iso&tlng=es We present a summary of the methods of Lie symmetry and Painlevé singularity analyses and apply them to a number of well-known epidemiological models to demonstrate the utility of these analyses in the analysis of dynamical systems which arise during investigations of the evolution of diseases. http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0038-23532009000200017&lng=es&nrm=iso&tlng=es Medicinal plants with a high content of sterols and sterolins, such as Bulbine natalensis (rooiwortel) and Hypoxis hemerocallidea (African potato), are commonly and inappropriately used in South Africa for the treatment of HIV/AIDS due to the inaccessibility of antiretroviral drugs. This study investigated the presence of active compounds, such as sterols and sterolins, in the herbal medicines. The research was carried out in the Nelson Mandela Metropole area. The effect of microbial contaminants isolated from the medicines on sterols and sterolins of rooiwortel extracts was assessed. Sterols and sterolins were detected in rooiwortel, raw African potatoes and one ready-made mixture. Co-incubation of rooiwortel with bacteria (Bacillus spp. and Pseudomonas putida) and fungi (Aspergillus spp., Penicillium spp. and Mucor spp.) that were isolated from these samples increased the rate of degradation of sterols and sterolins over time, with slower degradation at 4°C than at 28°C. http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0038-23532009000200018&lng=es&nrm=iso&tlng=es Bathymetry as a discriminatory tool for targeting suitable coelacanth habitats is explored. A regional bathymetry, garnered from pre-existing data sets, and geo-referenced bathymetric charts for the western Indian Ocean is collated and incorporated into a geographical information system (GIS). This allows the suitability of coelacanth habitation, based on criteria concerning depth and shelf morphology from known coelacanth habitats, to be interrogated. A best guess for further detailed exploration is provided, targeting northern Mozambique, between Olumbe and Port Amelia, and the Port St Johns-Port Shepstone stretch of coastline in South Africa. Sparse data prevent the identification of Tanzanian and Madagascan target sites, though these should not be ignored. Ultimately, the GIS is envisioned as a flexible tool within which other spatial data collected in these areas concerning coelacanths may be incorporated. http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0038-23532009000200019&lng=es&nrm=iso&tlng=es The previous report of the presence of lovebirds (Agapornis) at the Plio-Pleistocene Kromdraai B fossil locality is confirmed by the identification of a humerus from Member 3. That fossil specimen differs from extant lovebird species in morphology, and its slightly smaller size indicates that it likely represents an extinct taxon. This lovebird specimen is likely from the early Pleistocene (younger than 1.95 Myr) and appears to have been deposited around the same time as the fossil hominid specimens that have been uncovered at the site. The modern preference of lovebirds for a wide variety of wooded and forested habitats adds support to the mammalian-based idea that the palaeohabitat around Kromdraai B where Australopithecus robustus lived in the early Pleistocene was a mosaic that included wooded or forested habitats. http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0038-23532009000200020&lng=es&nrm=iso&tlng=es A nutritional and phytochemical evaluation of cultivated Psathyrella atroumbonata Pegler was carried out at the immature and mature stages of the mushroom. The cultivated mushroom is very rich in protein and fibres compared with the wild species, and has a low lipid and sugar content. The nutrient composition is dependent upon the stage of its development and nutrient content was at a maximum at immature stage and decreased during further development. Alkaloids were detected in the mature fruit body, but not in the immature stage. However, saponins and tannins were present in both immature and mature stages. Flavonoids and anthraquinones were absent in the mushroom. The importance of these findings is discussed.