Fatty acids reveal the importance of autochthonous non-vascular plant inputs to an austral river food web

We hypothesised that the dominant organic source supporting macroinvertebrate consumers in a South African river is autochthonously produced non-vascular algae (regardless of season), and that the prevalence of autochthony increases with increasing distance from the headwaters. Fatty acid profiles of macroinvertebrates from six sites and four sample times were assessed to characterise the consumer diets and estimate the relative assimilation of autochthonous versus allochthonous-based sources in the food web. Fatty acid markers, ordination analyses and mixing models confirmed that the ultimate nutritional source for the invertebrate assemblages was autochthonous-produced carbon, with some contributions occurring from vascular plants (potentially of allochthonous and autochthonous origin, as some vascular plants were aquatic macrophytes). However, contrary to our second hypothesis, the prevalence of autochthony did not change predictably along the river. Such an autochthonous-based food web is consistent with many large rivers in well-researched regions of the world, although the complexity and variability that we observed in the fatty acid profiles of macroinvertebrate consumers in a small South African river should help stimulate renewed interest in investigations of carbon flow within small rivers from less-studied regions (particularly in arid climates).     

Micropropagation of Anacardiaceae species of economic importance: advances and future prospects

The Anacardiaceae family comprises tropical and subtropical deciduous trees with growing economic potential namely, Pistacia vera L. (pistachio), Mangifera indica L. (mango), Anacardium occidentale L. (cashew), and Sclerocarya birrea (A. Rich.) Hochst. subsp. caffra (Sond.) Kokwaro (marula). The rich gene pool offered by their respective wide genetic diversity as well as the greater adaptation to semi-arid environments makes these species ideal candidates for the development of future commercial cultivars. Some notable achievements have been recorded in the micropropagation of these Anacardiaceae species in the order M. indica > P. vera > A. occidentale > S. birrea subsp. caffra. This review highlights advances, challenges, and future prospects in micropropagation research of these Anacardiaceae family members for the past three decades. In addition, the review discusses the potential of liquid cultures and synthetic seed encapsulation technologies in the development of future research strategies.     

Preparation of poly(methyl methacrylate)–grafted Hyparrhenia hirta for methyl red removal from colored solutions

Poly(methyl methacrylate)–grafted Hyparrhenia hirta (PMMA-g-Hh) biopolymer was prepared through radical polymerization using potassium persulfate (KPS) and applied in adsorption of methyl red from colored solutions. Solvent amount, initiator concentration, monomer concentration, temperature, and reaction time were the reaction parameters investigated for grafting. The biopolymer was characterized by scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), and x-ray diffraction spectroscopy (XRD). The adsorption process was investigated with respect to pH, contact time, initial concentration, adsorbent dosage, and temperature. The optimum adsorption parameters were pH 6, contact time 90 min, adsorbent dosage 0.6 g, and initial concentration 50 mg/L. The Langmuir adsorption model best fitted the adsorption process, with maximum adsorption capacities of 19.95, 6.89, and 4.02 mg/g at adsorbent dosages of 0.2, 0.6, and 1.0 g, respectively. The pseudo-second-order model described the kinetics data better. The adsorption process was physical, spontaneous, and endothermic. The adsorbent was still active after 10 adsorption-desorption cycles, showing its suitability for use in colored solutions treatment.     

Stream fish assemblage and habitat structure in a tropical African river basin (Nyagui River, Zimbabwe)

Few studies have been carried out on stream ecology in southern Africa although many species are endangered. This study investigated the stream fish assemblage and their habitat associations over a period of 3 months (October 2004 to January 2005), in view of the proposal to build a dam across the Nyagui River. Twenty-four fish species were collected and were separated into groups based on preferred microhabitats. The first group, dominated by Barbus paludinosus , comprised species collected from the upstream stations with slow flow, shallow depth (pools) and fine substrate type. Species associated with riffles, which included Chiloglanis neumanni , Labeobarbus marequensis and Opsaridium zambezense , comprised the second group on the downstream. The last group comprised species preferring pools with rock substrate and slow flow such as Pharyngochromis acuticeps and Pseudocranilabrus philander . The species were consistently associated with their habitat types throughout the sampling period. This relationship may be explained by the fish's morphological adaptations. Species richness increased from nine in the upstream section to twenty in the downstream section and this was related to increasing habitat complexity downstream. The construction of the Kunzvi Dam across the Nyagui River is likely to lead to loss of rheophilic species while cichlids and introduced species may increase.