Clonal variation in acetylcholinesterase biomarkers and life history traits following OP exposure in Daphnia magna

Two clones of Daphnia magna (Standard and Ruth) were exposed for 7 days to sub-lethal concentrations of acephate (5.0 and 10.0 mg/L). Survivorship, individual growth, reproduction and the population growth rate (lambda) were evaluated over three weeks. Acetylcholinesterase (AChE) activity was measured on days 2, 7 and 21. Acephate exposure inhibited AChE activity but had no direct effect on life history (LH) traits. There was also no effect of clone on AChE activity, LH and lambda. However, a significant interaction between clone and acephate concentration was found on both fecundity and AChE inhibition at 48 h was associated with a decrease in lambda the Standard clone and an increase in lambda in clone Ruth. Therefore, our findings show that genotypic variation will influence the link between AChE activity and toxic effects at higher levels of biological organisation in D. magna. (c) 2007 Elsevier Inc. All rights reserved.

The costs and consequences of parasitoid attack for the predatory hoverfly, Episyrphus balteatus

Question: What are the life-history costs for a predatory insect of surviving parasitoid attack, and can parasitoid attack alter predator-prey interactions? Hypotheses: Survivorship is influenced by host age. Hosts that suffer parasitoid attack grow more slowly and consume fewer prey. Those that survive attack are smaller as adults and show reduced survivorship. Organisms: The aphidophagous hoverfly Episyrphus balteatus, its endoparasitoid wasp Diplazon laetatorius and its prey, the pea aphid, Acyrthosiphon pisum. Site of experiments: All experiments were conducted in controlled temperature rooms and chambers in the laboratory. Methods: Episyrphus balteatus larvae of each instar were exposed to attack by Diplazon laetatorius, then dissected to measure the encapsulation response (a measure of immunity). Second instar larvae were either attacked or not attacked by D. laetatorius. Their development rates and numbers of prey consumed were noted. The size and survivorship of surviving (immune) and control hoverflies were compared following eclosion. Conclusions: Successful immune response increased with larval age (first instar 0%, second instar 40%, third instar 100% survival). Second instar larvae that successfully resisted parasitoid attack were larger as pupae (but not as adults) and showed reduced adult survivorship. Female adult survivors were more likely than male survivors to have died within 16 days of eclosion, but there was no difference between unattacked male and female control hoverflies. Attacked larvae, irrespective of immune status, consumed fewer aphids than unattacked individuals. Episyrphus balteatus suffers significant costs of resisting parasitoid attack, and parasitoid attack can reduce the top-down effects of an insect predator, irrespective of whether the host mounts an immune response or not.

Post-traumatic stress symptoms in childhood brain tumour survivors and their parents

Objectives This study aimed to investigate post-traumatic stress symptoms (PTSS) in childhood brain tumour survivors and their parents. A further aim was to explore the relationship between objective illness parameters, parent–child interactions, coping styles and PTSS. Methods A cross-sectional correlational design was employed. Fifty-two childhood brain tumour survivors, aged 8–16, and 52 parents completed a battery of questionnaires designed to assess quality of parent–child interactions, monitoring and blunting attentional coping styles and PTSS. Results Over one-third (35%) of survivors and 29% of their parents reported severe levels of PTSS (suggestive of post-traumatic stress disorder ‘caseness’). Increased parent–child conflict resolution for survivors and number of tumour recurrences for parents independently predicted the variance in PTSS. Conclusions For a substantial proportion of brain tumour survivors and their parents the process of survivorship is a considerably distressing experience.

Supplementary feeding of wild birds indirectly affects the local abundance of arthropod prey

Providing supplementary food for wild birds is a globally popular past-time; almost half of the households in many developed countries participate and billions of US dollars are spent annually. Although the direct influence of this additional resource on bird survivorship and fecundity has been studied, there is little understanding of the wider ecological consequences of this massive perturbation to (what are usually) urban ecosystems. We investigated the possible effects of wild bird feeding on the size and survivorship of colonies of a widespread arthropod prey species of many small passerine birds, the pea aphid [Acyrthosiphon pisum (Harris); Hemiptera: Aphididae], in suburban gardens in a large town in southern England. We found significantly fewer aphids and shorter colony survival times in colonies exposed to avian predation compared to protected controls in gardens with a bird feeder but no such differences between exposed and protected colonies in gardens that did not feed birds. Our work therefore suggests that supplementary feeding of wild birds in gardens may indirectly influence population sizes and survivorship of their arthropod prey and highlights the need for further research into the potential effects on other species.

Islamic mutual funds' financial performance and international investment style: evidence from 20 countries

We pursue the first large-scale investigation of a strongly growing mutual fund type: Islamic funds. Based on an unexplored, survivorship bias-adjusted data set, we analyse the financial performance and investment style of 265 Islamic equity funds from 20 countries. As Islamic funds often have diverse investment regions, we develop a (conditional) three-level Carhart model to simultaneously control for exposure to different national, regional and global equity markets and investment styles. Consistent with recent evidence for conventional funds, we find Islamic funds to display superior learning in more developed Islamic financial markets. While Islamic funds from these markets are competitive to international equity benchmarks, funds from especially Western nations with less Islamic assets tend to significantly underperform. Islamic funds’ investment style is somewhat tilted towards growth stocks. Funds from predominantly Muslim economies also show a clear small cap preference. These results are consistent over time and robust to time varying market exposures and capital market restrictions.