Results 1 - 10 of 549
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[en] The study conducted in different bioclimatic areas, has revealed that mites particularly Oribatida present a staggering distribution inspace and time in correlation with the improvement of the ecological conditions.The arid and semi-arid areas constitute a less favorable environment in contrast tothe humid and sub humid zones which are characterised by a more favorable variety of vegetation and climatic conditions. These conditions constitute a favorable environment for the development of mites especially Oribati. There are 6 species in arid zones, 11 species in semi-arid zones and 30 in wetlands and sub-humid areas. This hierarchical classification of mites stands is in good agreement with the environmental conditions which prevail in this region. However, it can be noted that the behavior of mites species manifests itself differently. Certain species show tolerance to these variations and their distribution area is important and very large. On the contrary, the majority of species whose distribution area is limited are very demanding vis-a-vis these conditions. Their presence requires some moisture in the environment and an adequate nutritional support (litter). It constitutes an important biological indicator since it helps in understanding the natural or anthropogenic changes that can alter the environment. (author)
[en] The present study tests the effect of antiparasitic compound ivermectin in a constructed food-web system, a soil multi-species (SMS) higher tier test system. Mutualism, competition and predation within the SMS system were introduced by the addition of five collembolan species, one enchytraeid and a predatory mite species. Bait lamina sticks were incorporated as a measure of functional toxicity, attempting to the integrated feeding activity of the invertebrates. The study showed that on the community level all treatments were significantly affecting the community abundance and composition and that the decrease in abundance corresponded well with increasing exposure concentration for all species. Since all concentrations had significant adverse effect on the community structure, the community-based no-effect-concentration is below the lowest test concentration of 0.25 mg kg−1, whereas the EC10 for the individual species were as low as 0.05 mg kg−1. The bait lamina respond was only affected at the highest exposure concentration. - Highlights: ► A multi-species test system was used to evaluate the impact of hazardous substances. ► The pharmaceutical ivermectin was toxic to a wide set of soil invertebrates. ► The toxicity to springtails was higher when exposed in co-existence with a predator. ► Structural endpoints were more sensitive than functional ditto measured by Bait lamina. - Hazardous substances are shown more toxic to soil dwelling invertebrates when exposed in co-existence with other species including a predator.
[en] Much spider silk research to date has focused on its mechanical properties. However, the webs of many orb-web spiders have evolved for over 136 million years to evade visual detection by insect prey. It is therefore a photonic device in addition to being a mechanical device. Herein we use optical surface profiling of capture silks from the webs of adult female St Andrews cross spiders (Argiope keyserlingi) to successfully measure the geometry of adhesive silk droplets and to show a bowing in the aqueous layer on the spider capture silk between adhesive droplets. Optical surface profiling shows geometric features of the capture silk that have not been previously measured and contributes to understanding the links between the physical form and biological function. The research also demonstrates non-standard use of an optical surface profiler to measure the maximum width of a transparent micro-sized droplet (microlens).
[en] Tetranychus urticae (Acari: Tetranychidae) is an important pest of ornamental crops. A species of predatory mite used for its control is Neoseiulus californicus and Phytoseiulus persimilis (Acari: Phytoseiidae). This research proposes the use of joint releases of the two cited predators for the control of the pest. Several situations leading to interaction were evaluated: high density of one predator and low density of the other one, being the prey present or absent. The scenario with predators in equal densities and in presence of the prey was also evaluated. When a predator is in higher density and the prey present, the predator with the lower density increases the interference with the consumption of preys by the predator with higher density. On the other hand, when the consumption of T. urticae reduces, intraguild predation increases. P. persimilis shows intraguild predation behavior when t. urticae is absent and N. californicus is present, consuming all developmental stages of its conspecific. Instead, N. californicus only feed on conspecific larvae, when the fitofagous was absent and P. persimilis was present. When the two predators were present in the same assemblage and with the same population density, the quantity of T. urticae consumed by both of them was not higher than the consumed one when each predator was present in separate way.
[en] A method is presented for the calculation of association constants and the concentration of binding sites in a reaction of a ligand with a heterogeneous system of binding sites. The Scatchard plot for such a system is curvelinear and the method employs previously established relationships between the parameters of the limiting slopes to such a curve and the above mentioned association constants and concentrations of binding sites. The special case of a system with two different and non-interacting groups of binding sites was solved. The expressions thus obtained were used to characterize the reaction of a polypeptide neurotoxin with its specific binding sites in a membranal preparation from insect central nervous system. Moreover it is evident from these expressions that the widely accepted method to analyze such system, by an intuitive generalization of the method applicable to homogeneous systems, is erroneous and should be avoided. (author)
[en] This project was a collaborative FNCA project involving Malaysia, Thailand, Indonesia and Japan. The objective was to jointly produce new orchid mutants that resistant/tolerant to insect infestation. It focused on commercial hybrids or species of Dendrobium orchids; namely Dendrobium Sonia 17 Red from Thailand, Dendrobium jayakarta from Indonesia and Dendrobium mirbellianum from Malaysia. In this project, tissue culture orchid materials (proto corm-like-bodies or PLBs) were exchanged among the participated countries early in the project. The Malaysian research team had irradiated these PLBs with two ionizing mutagens; gamma rays and ion beams (JAEA). Following irradiation, regenerated plant lets were randomly selected from each dose and subjected to in vitro infestation with mites and thrips, to analyse their resistance towards these pests. The main aim of in vitro infestation was to pre-select potential mutants for secondary screening at flowering stage. Potential insect resistant orchid mutants were then selected and subsequently planted in the glass house. Secondary screenings were carried out at flowering stage by challenge-infestation with the target insects. This project, which was completed in December 2009, has successfully generated two D. jayakarta mutants tolerant to thrips, and one D. mirbellianum tolerant to both mite and thrips. (author)
[en] Weeds and non-cultivated plants have a great impact on abundance and diversity of beneficial arthropods in agriculture. The main aim of this work was to study the influence of the ecological infrastructure (meadows and weedy margins) on the arthropod composition in vineyard surrounding landscape. Research was carried out from May to October during three years. Sampling took place in the ecological infrastructure of three differently managed vineyards (organic, integrated and extensive). Three zones were chosen in each vineyard (3 m, 10 m, and 30 m from the edge of the vineyard). Samples were taken using a standardised sweep net method. In total, we captured 6032 spiders and 1309 insects belonging to 4 orders and 10 families. Arthropod fauna was numerically dominated by Aranea (82.1%); among insects, Coleoptera was the most abundant taxonomic group (10.6%); Neuroptera showed the lowest value (0.88%). Significant differences were found between sites and zones. Organic vineyard showed the highest abundance of arthropods (92.41% were spiders) and in the integrated vineyard there was a 23% of insects. Both the highest abundance of arthropods and the highest Shannon Index value (2.46) was found 3 m away from the edge of the vineyard. Results showed that spiders were the dominant arthropods and ladybugs the dominant insects. Weedy strips near the edge of the vineyard contained a high number of insects and spiders. Our results support the importance of weedy margins in enhancing the population of arthropods as well as in biodiversity promotion. Well-managed field margins could play important role in biological control of vineyard pests. (Author)