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The anaesthetic effectiveness of separate and combined eucalyptus Eucalyptus globulus and oregano Origanum vulgare essential oils (EO) were investigated in silver kob Argyrosomus inodorus and were compared with clove oil Eugenia caryophyllata. Argyrosomus inodorus adults (595.61 [SE 11.82] g) were exposed to three concentrations of oregano EO (OEO: 25, 50 and 100 µl l−1), eucalyptus EO (EEO: 300, 500 and 600 µl l−1), and their mixtures (12.5 µl l−1 OEO to 150 µl l−1 EEO; 12.5 µl l−1 OEO to 300 µl l−1 EEO; 25 µl l−1 OEO to 150 µl l−1 EEO), with each fish treated as a replicate. Fish were also exposed to 40 µl l−1 of clove oil (CEO), which acted as a control. The two EOs and their mixtures proved to possess anaesthetic capacity in A. inodorus. Anaesthesia induction time (seconds) decreased with increased concentrations, whereas the inverse was reported for the recovery response. Only OEO qualified as an ideal anaesthetic agent for A. inodorus, especially 25 and 50 µl l−1, as the anaesthesia induction times with these concentrations were less than 180 s and recovery was within 300 s. It seems that EEO could achieve greater anaesthetic effectiveness only at a higher concentration (600 µl l−1) or when mixed with OEO (at 25 µl l−1 OEO to 150 µl l−1 EEO). This study introduces oregano as a promising anaesthetic in A. inodorus compared with clove oil and EEO. However, further evaluations are deemed necessary. [ABSTRACT FROM AUTHOR]

Arthropods are valuable biological indicators owing to strong relationships with primary producers. The supposition that arthropod-plant interactions are constant over seasons was tested using Mantel tests on correlations between these groups. A total of 78 plant species and 108 arthropod families were sampled monthly from the endangered Bloemfontein Dry Grassland at the Free State National Botanical Gardens between April 2009 and March 2010. Interaction strengths between plants and arthropods varied within a calendar year; being strongest in winter months (July and August), initiation of the growth season (November) and peak growth season (February and March). It was hypothesised that variation was caused by changing primary productivity. The trophic composition of the arthropod community supported this hypothesis as the ratio between primary consumers (herbivores) and secondary consumers (predators and parasitoids) showed patterns that coincided with periods of strong arthropod-plant interactions. Patterns were explained by multiple theories linking plant and arthropod diversity. It was concluded that arthropod assemblages are closely linked to primary producers, the abiotic environment and top-down trophic forces at different times of the year. Future arthropod-based studies should be performed with clear objectives and seasonal benchmark conditions to overcome these variations. [ABSTRACT FROM AUTHOR]

Education usually correlates with economic development. In the transformation process of any traditional society education is most often assumed to provide the solution to or stimulus for development. Many governments are convinced that education or, more generally, capital investment in human beings contributes as much to economic growth as does investment in capital equipment. As a result the proportion of public expenditure on education in developing countries is often very high. This paper is an attempt to point out what the effects of public expenditure on education in Bophuthatswana are, given constraints such as economic efficiency and equity. In Bophuthatswana these economic effects of education tend to go beyond the borders of the country. [ABSTRACT FROM PUBLISHER]