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The immunocompetence handicap hypothesis (ICHH) of Folstad and Karter has inspired a large number of studies that have tried to understand the causal basis of parasite-mediated sexual selection. Even though this hypothesis is based on the double function of testosterone, a hormone restricted to vertebrates, studies of invertebrates have tended to provide(More)
Sexual dimorphism in immune function is a common pattern in vertebrates and also in a number of invertebrates. Most often, females are more 'immunocompetent' than males. The underlying causes are explained by either the role of immunosuppressive substances, such as testosterone, or by fundamental differences in male and female life histories. Here, we(More)
Ecological immunology is a rapidly expanding field that examines the causes and consequences of variation in immune function in the context of evolution and of ecology. Millions of invertebrate species rely solely on innate immunity, compared with only 45,000 vertebrate species that rely additionally on an acquired immune system. Despite this difference in(More)
There are well documented costs of mating in insects but little evidence for underlying mechanisms. Here, we provide experimental evidence for a hormone-based mechanism that reduces immunity as a result of mating. We examined the mealworm beetle Tenebrio molitor and show that (i) mating reduces a major humoral immune effector-system (phenoloxidase) in both(More)
During 400 million years of existence, insects have rarely succumbed to the evolution of microbial resistance against their potent antimicrobial immune defenses. We found that microbial clearance after infection is extremely fast and that induced antimicrobial activity starts to increase only when most of the bacteria (99.5%) have been removed. Our(More)
Central to the conceptual basis of ecological immunity is the notion that immune effector systems are costly to produce, run, and/or maintain. Using the mealworm beetle, Tenebrio molitor, as a model we investigated two aspects of the costs of innate immunity. We conducted an experiment designed to identify the cost of an induced immune response, and the(More)
The pathology of many of the world's most important infectious diseases is caused by the immune response. Additionally age-related disease is often attributed to inflammatory responses. Consequently a reduction in infections and hence inflammation early in life has been hypothesized to explain the rise in lifespan in industrialized societies. Here we(More)
The absence of continued evolutionary change despite the presence of genetic variation and directional selection is very common. Genetic correlations between traits can reduce the evolvability of traits. One intriguing example might be found in a sexual conflict over sexually dimorphic traits: a common genetic architecture constrains the response to(More)
The influence of ectoparasitic water mite larvae (Arrenurus) on the fluctuating asymmetry (FA) of forewing length and cell number in the foreweings of the damselfly Coenagrion puella has been investigated. We show a significant correlation between the FA of forewing length and the mite load. Most explanations for increases in FA implicate environmental(More)