Body Odors of Parasitized Caterpillars Give Away the Presence of Parasitoid Larvae to Their Primary Hyperparasitoid Enemies

Foraging success of parasitoids depends on the utilization of reliable information on the presence of their often, inconspicuous hosts. These parasitic wasps use herbivore-induced plant volatiles (HIPVs) that provide reliable cues on host presence. However, host searching of hyperparasitoids, a group of parasitoids that parasitize the larvae and pupae of other parasitoids, is more constrained. Their hosts do not feed on plants, and often are even concealed inside the body of the herbivore host. Hyperparasitoids recently have been found to use HIPVs of plants damaged by herbivore hosts in which the parasitoid larvae develop. However, hyperparasitoids that search for these parasitoid larvae may be confronted with healthy and parasitized caterpillars on the same plant, further complicating their host location. In this study, we addressed whether the primary hyperparasitoid Baryscapus galactopus uses caterpillar body odors to discriminate between unparasitized herbivores and herbivores carrying larvae of parasitoid hosts. We show that the hyperparasitoids made faster first contact and spent a longer mounting time with parasitized caterpillars. Moreover, although the three parasitoid hosts conferred different fitness values for the development of B. galactopus, the hyperparasitoids showed similar behavioral responses to caterpillar hosts carrying different primary parasitoid hosts. In addition, a two-chamber olfactometer assay revealed that volatiles emitted by parasitized caterpillars were more attractive to the hyperparasitoids than those emitted by unparasitized caterpillars. Analysis of volatiles revealed that body odors of parasitized caterpillars differ from unparasitized caterpillars, allowing the hyperparasitoids to detect their parasitoid host.     

Energy consumption and economic growth: The experience of African countries revisited

The aim of this paper is to re-examine the causal relationship between energy consumption and economic growth for seventeen African countries in a multivariate framework by including labor and capital as additional variables. We apply the variance decomposition analysis due to Pesaran and Shin [Pesaran M.H. and Shin, Y. Generalised impulse response analysis in linear multivariate models, Economics Letters, 1998; 58; 17–29.] to evaluate how important is the causal impact of energy consumption on economic growth relative to labor and capital. The results of our multivariate modified Granger causality analysis due to Toda and Yamamoto [Toda, H.Y. and Yamamoto, T. Statistical inference in vector autoregressions with possibly integrated process, Journal of Econometrics, 1995; 66; 225–250.] tend to reject the neutrality hypothesis for the energy–income relationship in fifteen out of the seventeen countries. In contrast, results of our variance decomposition analyses show that in eleven out of the seventeen countries, energy is no more than a contributing factor to output growth and not an important one when compared to capital and labor. Labor and capital are the most important factors in output growth in fifteen out of the seventeen countries. However, these results should be interpreted with care as they may not be sufficiently robust enough to support the inference that energy consumption plays a minor role in the economic growth of African countries.     

Polyethylene film as concrete curing material in a tropical climate

Concrete specimens were cast at and exposed to three different climatic regions in Ethiopia. The specimens were cured for different length of time, either covered with transparent polyethylene film, or by intermittent watering. At the end of the curing periods the specimens were stored at 20°C and 65% relative humidity until tested for compressive strength. Reference specimens were cast at 20°C and water cured, after 24 hours, for the next 6 days and finally stored at 20°C and 65% relative humidity. After 24 hours, the compressive strength of specimens exposed to the different climatic regions ranged from a high of 322% to a low of 77% of reference specimens, depending on the environmental conditions and type of curing media used. At higher ages, no deficiencies were observed from specimens cast at and exposed covered with polyethylene film. Others showed pronounced deficiencies.     

Levels of essential and non-essential metals in leaves of the tea plant (Camellia sinensis L.) and soil of Wushwush farms,Ethiopia

Five tea clones of the Camellia assamica variety grown in Wushwush tea plantation farms, Ethiopia, were analyzed for their contents of essential, non-essential and toxic metals (K, Ca, Mg, Fe, Mn, Cu, Zn, Na, Cd and Pb) by atomic absorption flame emission spectroscopy. Both the tea leaves and the soils of the study farms showed similar accumulation patterns in their contents of the studied macronutrients. Among the macronutrient metals, K was the most abundant element in the tea leaves (17.7–24.8 mg/g) and the soils (7.14–9.73 mg/g). Mn was the predominant micronutrient heavy metal in the tea leaf tissues ranging between 501 and 1281 mg/kg. Level of Fe (29.6–100 mg/kg) in the leaf tissue was found to be the second most abundant micronutrient next to Mn whereas concentrations of Cu and Co were relatively lower both in the soil and tea samples. The toxic heavy metals Pb and Cd in the leaf tissues were present at levels too low to be detected by the analytical technique used in this study. The soils were found to be acidic (pH 5.04–5.49) with high organic matter (5.48–6.02%). Fe was the most abundant metal followed by Mn, Na and Zn in the soils. Unlike the tea leaves, the soils were found to contain traces of the toxic metal, Cd (0.02–1.10 mg/kg). The levels of most of the metals determined in this study compared well with those reported for tea leaves from some other parts of the world.     

Bounds test approach to cointegration and causality between nuclear energy consumption and economic growth in India

This paper attempts to examine the dynamic relationship between economic growth, nuclear energy consumption, labor and capital for India for the period 1969–2006. Applying the bounds test approach to cointegration developed by Pesaran et al. (2001) we find that there was a short- and a long-run relationship between nuclear energy consumption and economic growth. Using four long-run estimators we also found that nuclear energy consumption has a positive and a statistically significant impact on India's economic growth. Further, applying the Toda and Yamamoto (1995) approach to Granger causality and the variance decomposition approach developed by Pesaran and Shin (1998), we found a positive and a significant uni-directional causality running from nuclear energy consumption to economic growth without feedback. This implies that economic growth in India is dependent on nuclear energy consumption where a decrease in nuclear energy consumption may lead to a decrease in real income. For a fast growing energy-dependent economy this may have far-reaching implications for economic growth. India's economic growth can be frustrated if energy conservation measures are undertaken without due regard to the negative impact they have on economic growth.     

A systematic tool for the minimization of the life cycle impact of solar assisted absorption cooling systems

In recent years, there has been a growing increase of the cooling demand in many parts of the world, which has led to major energy problems. In this context, solar assisted absorption cooling systems have emerged as a promising alternative to conventional vapor compression air conditioning systems, given the fact that in many cases the cooling demand coincide with the availability of solar radiation. In this work, we present a decision-support tool based on mathematical programming for the design of solar assisted absorption cooling systems. The design task is formulated as a bi-criteria mixed-integer nonlinear programming (MINLP) optimization problem that accounts for the minimization of the total cost of the cooling system and the associated environmental impact measured over its entire life cycle. The capabilities of the proposed method are illustrated in a case study that addresses the design of a solar assisted ammonia-water absorption cycle considering weather data of Barcelona (Spain).     

Herbivore-Mediated Effects of Glucosinolates on Different Natural Enemies of a Specialist Aphid

The cabbage aphid Brevicoryne brassicae is a specialist herbivore that sequesters glucosinolates from its host plant as a defense against its predators. It is unknown to what extent parasitoids are affected by this sequestration. We investigated herbivore-mediated effects of glucosinolates on the parasitoid wasp Diaeretiella rapae and the predator Episyrphus balteatus. We reared B. brassicae on three ecotypes of Arabidopsis thaliana that differ in glucosinolate content and on one genetically transformed line with modified concentrations of aliphatic glucosinolates. We tested aphid performance and the performance and behavior of both natural enemies. We correlated this with phloem and aphid glucosinolate concentrations and emission of volatiles. Brevicoryne brassicae performance correlated positively with concentrations of both aliphatic and indole glucosinolates in the phloem. Aphids selectively sequestered glucosinolates. Glucosinolate concentration in B. brassicae correlated negatively with performance of the predator, but positively with performance of the parasitoid, possibly because the aphids with the highest glucosinolate concentrations had a higher body weight. Both natural enemies showed a positive performance-preference correlation. The predator preferred the ecotype with the lowest emission of volatile glucosinolate breakdown products in each test combination, whereas the parasitoid wasp preferred the A. thaliana ecotype with the highest emission of these volatiles. The study shows that there are differential herbivore-mediated effects of glucosinolates on a predator and a parasitoid of a specialist aphid that selectively sequesters glucosinolates from its host plant.