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Parental environments have profound consequences for offspring fitness through transgenerational transmission of resources and epigenetic factors. Locomotor activity is a functional trait of considerable ecological importance, as it determines the ability of animals to find food and mates and to disperse to more favourable environments. Although there have been studies demonstrating that animals can plastically increase their locomotor capacity in response to nutritionally stressful environments, it remains largely unexplored whether and how parental diet can adjust offspring locomotor capacity and its related traits. In this study, we tested the hypothesis that the parental intake of a nutritionally suboptimal diet would induce hyperactivity in the offspring and that this transgenerational effect could lead to improved offspring performance in an insect herbivore, the bean bug (Riptortus pedestris Fabricius) (Hemiptera: Alydidae). We compared the locomotor activity, metabolic phenotype and performance traits of two groups of R. pedestris nymphs born to parents raised on soybeans [Glycine max (L.) Merr, Fabaceae; standard diet] or peanuts (Arachis hypogaea L., Fabaceae; high‐fat diet). Despite being smaller at birth, the offspring of peanut‐fed parents moved faster and more frequently than those of soybean‐fed parents during their early development. The newly hatched offspring born to peanut‐fed parents had higher relative energy reserves in somatic tissues than those born to soybean‐fed parents, indicating that differential parental provisioning could underpin this parental effect on offspring locomotor activity. Possibly through increased foraging activity, the hyperactive offspring of peanut‐fed parents grew faster into heavier adults than the offspring of soybean‐fed parents, implying that parentally induced increase in offspring locomotor activity is adaptive. This study provides experimental evidence for diet‐mediated transgenerational plasticity of locomotor activity in invertebrates and sheds novel insights into the role of parental diet history in shaping offspring phenotype. [ABSTRACT FROM AUTHOR]

To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.anbehav.2004.03.003 Byline: Stephen J. Simpson, Richard M. Sibly, Kwang Pum Lee, Spencer T. Behmer, David Raubenheimer Abstract: There is growing evidence that, rather than maximizing energy intake subject to constraints, many animals attempt to regulate intake of multiple nutrients independently. In the complex diets of animals such as herbivores, the consumption of nutritionally imbalanced foods is sometimes inevitable, forcing trade-offs between eating too much of nutrients present in the foods in relative excess against too little of those in deficit. Such situations are not adequately represented in existing formulations of foraging theory. Here we provide the necessary theory to fit this case, using an approach that combines state-space models of nutrition with Tilman's models of resource exploitation (Tilman 1982, Resource Competition and Community Structure, Princeton: Princeton University Press). Our approach was to construct a smooth fitness landscape over nutrient space, centred on a 'target' intake at which no fitness cost is incurred, and this leads to a natural classification of the simple possible fitness landscapes based on Taylor series approximations of landscape shape. We next examined how needs for multiple nutrients can be assessed experimentally using direct measures of animal performance as the common currency, so that the nutritional strategies of animals can be mapped on to the performance surface, including the position of regulated points of intake and points of nutrient balance when fed suboptimal foods. We surveyed published data and conducted an experiment to map out the performance landscape of a generalist leaf-feeding caterpillar, Spodoptera littoralis. Author Affiliation: (*) Department of Zoology and University Museum of Natural History, University of Oxford, U.K. (a ) School of Animal and Microbial Sciences, University of Reading, U.K. (a ) School of Biological Sciences, University of Auckland, New Zealand Article History: Received 26 August 2003; Revised 22 October 2003; Accepted 12 March 2004 Article Note: (miscellaneous) MS. number: 7831

Environments experienced during development have long‐lasting consequences for adult performance and fitness. The "environmental matching" hypothesis predicts that individuals perform best when adult and developmental environments match whereas the "silver spoon" hypothesis expects that fitness is higher in individuals developed under favorable environments regardless of adult environments. Temperature and nutrition are the two most influential determinants of environmental quality, but it remains to be elucidated which of these hypotheses better explains the long‐term effects of thermal and nutritional histories on adult fitness traits. Here we compared how the temperature and nutrition of larval environment would affect adult survivorship and reproductive success in the fruit fly, Drosophila melanogaster. The aspect of nutrition focused on in this study was the dietary protein‐to‐carbohydrate (P:C) ratio. The impact of low developmental and adult temperature was to improve adult survivorship. High P:C diet had a negative effect on adult survivorship when ingested during the adult stage, but had a positive effect when ingested during development. No matter whether adult and developmental environments matched or not, females raised in warm and protein‐enriched environments produced more eggs than those raised in cool and protein‐limiting environments, suggesting the presence of a significant silver spoon effect of larval temperature and nutrition. The effect of larval temperature on adult egg production was weak but persisted across the early adult stage whereas that of larval nutrition was initially strong but diminished rapidly after day 5 posteclosion. Egg production after day 5 was strongly influenced by the P:C ratio of the adult diet, indicating that the diet contributing mainly to reproduction had shifted from larval to adult diet. Our results highlight the importance of thermal and nutritional histories in shaping organismal performance and fitness and also demonstrate how the silver spoon effects of these aspects of environmental histories differ fundamentally in their nature, strength, and persistence. [ABSTRACT FROM AUTHOR]

Ants are among a few invertebrates that can use certain tools. For example, some ants can use debris and soil grains to transport liquid food. Although there has been evidence showing that ants can select the most efficient tools in transporting liquid food, little is known about their flexibility in using a specific tool under environmental pressure.Black imported fire ants Solenopsis richteri Forel, can use sand grains as a tool for foraging. We hypothesized that S. richteri can adjust their strategy of tool use in response to various foraging risks. The hypothesis was tested by studying their sand use behaviour in response to sugar water with different drowning risks.The results support our hypothesis. Solenopsis richteri indeed adjusted their strategy of tool use in response to increased drowning risks. Due to their hydrophobic cuticle, S. richteri can float on water surface to forage directly with the minimal risk of drowning. However, when the drowning risk was elevated by reducing the surface tension of sugar water in a food container by the addition of surfactant, ants used sand grains to build a structure that could effectively function as a syphon instead of directly foraging inside the container. This sand structure could draw sugar water out of the container then to be collected by the ants, which not only reduced the drowning risk of ants, but also provided a larger operational space for their collection of sugar water.This study demonstrates that ants can not only recognize the increase in foraging risks, but also make corresponding adjustments to their strategy by using a specific tool. Our results also suggest that social insects can be highly flexible in their tool use in response to ecological challenges. A free Plain Language Summary can be found within the Supporting Information of this article. [ABSTRACT FROM AUTHOR]

Drosophila melanogaster Meigen (Diptera: Drosophilidae) is a key model insect for studying life span and aging. Many laboratory strains of D. melanogaster are currently used by laboratories worldwide, but they are known to vary considerably in their physiology, behavior, and life histories. Although the importance of dietary protein:carbohydrate (P:C) balance as a predominant determinant of life span and other life‐history traits has been highlighted in recent research, it remains unexplored whether the impacts of P:C balance on these fitness‐related traits vary in a strain‐specific manner in D. melanogaster. In this study, we compared the life‐history consequences (life span, egg production rate, pre‐adult survival, development time, and body mass at eclosion) of six laboratory strains of D. melanogaster (w1118, yw, Oregon‐R, white Canton‐S, Canton‐S‐SNU, and Canton‐S‐Inha) allocated to one of four synthetic diets differing in P:C ratio (1:16, 1:4, 1:1, or 4:1). The effects of dietary P:C balance on various adult and larval life‐history traits were qualitatively similar across all strains studied in this study. Regardless of fly strain, adults exhibited a shortened life span and improved egg production on a diet with the highest P:C ratio of 4:1. In all strains, larvae raised on a diet comprising the lowest P:C ratio of 1:16 suffered high mortality, delayed development time, and reduced body mass. Despite the general similarity in the direction of the effect of P:C balance across strains, fly strains differed in the magnitude of their life‐history responses to dietary P:C balance, as indicated by a significant interaction between fly strain and dietary P:C ratio for all measured traits except body mass at eclosion. Possible mechanisms explaining such strain‐specific responses are discussed. [ABSTRACT FROM AUTHOR]

Studies examining how diet affects mortality risk over age typically characterise mortality using parameters such as aging rates, which condense how much and how quickly the risk of dying changes over time into a single measure. Demographers have suggested that decoupling the tempo and the magnitude of changing mortality risk may facilitate comparative analyses of mortality trajectories, but it is unclear what biologically meaningful information this approach offers. Here, we determine how the amount and ratio of protein and carbohydrate ingested by female Drosophila melanogaster affects how much mortality risk increases over a time-standardised life-course (the shape of aging) and the tempo at which animals live and die (the pace of aging). We find that pace values increased as flies consumed more carbohydrate but declined with increasing protein consumption. Shape values were independent of protein intake but were lowest in flies consuming ~90 μg of carbohydrate daily. As protein intake only affected the pace of aging, varying protein intake rescaled mortality trajectories (i.e. stretched or compressed survival curves), while varying carbohydrate consumption caused deviation from temporal rescaling (i.e. changed the topography of time-standardised survival curves), by affecting pace and shape. Clearly, the pace and shape of aging may vary independently in response to dietary manipulation. This suggests that there is the potential for pace and shape to evolve independently of one another and respond to different physiological processes. Understanding the mechanisms responsible for independent variation in pace and shape, may offer insight into the factors underlying diverse mortality trajectories. [ABSTRACT FROM AUTHOR]

Although the ecological and evolutionary importance of environmentally induced parental effects is now widely recognized, such effects are still typically studied by contrasting just two environments in a single parental sex. Yet, parental effects should generally be viewed as reaction norms, and a more complete understanding of their ecological role therefore requires examining continuously varying and interacting environmental variables in both parental sexes., We used nutritional geometry to investigate linear, nonlinear and interactive effects of protein and carbohydrate in maternal and paternal larval diets on offspring juvenile development and viability and adult body size and shape in the fly Telostylinus angusticollis (Diptera: Neriidae)., We found that egg hatching success was enhanced by protein in the maternal larval diet but reduced by protein in the paternal larval diet, while other juvenile traits were unaffected by parental diets., Maternal effects on offspring adult body size and head elongation (a secondary sexual trait in males) were mediated by linear and quadratic effects of protein, and were consistent in sons and daughters. In contrast, paternal effects on offspring body size and head elongation were mediated by carbohydrate effects or carbohydrate─protein interactions, and varied by offspring sex., Our findings show that macronutrients in the parental larval diet can have complex, nonlinear and interactive effects on offspring traits, and that the effects of maternal and paternal diets can be strikingly different. Effects of parental diet on offspring represent important fitness consequences of variation in nutrient intake, with potential implications for the evolution of foraging and reproductive strategies. [ABSTRACT FROM AUTHOR]

Dietary specialization in insect herbivores has long been hypothesized to predict tolerance of plant defences, with more specialized herbivores being highly tolerant of and sometimes sequestering plant secondary compounds. Plant variation in secondary compounds should thus play an important and predictable role in shaping the performance and distribution of insect communities., We compared the performance of four naturally co-occurring aphid species on twenty genotypes of the common milkweed Asclepias syriaca. Genotypes of milkweed consistently differed in functional traits, including concentrations of toxic cardenolides, while the diet breadths of the four aphids ranged from broadly generalized to monophagous., The two more generalized species had the highest population growth rate overall, while growth rates decreased with increasing specialization. In contrast, honeydew exudation as a measure of phloem consumption increased with specialization; thus, resource-use efficiency was lower in specialist aphids. The two more generalized aphids grew best on genotypes with the highest plant growth rate (as an approximation for resource availability), while specialist aphids were not affected by plant growth., All four species contained apolar cardenolides in their bodies and excreted polar cardenolides, but only the most specialized aphid Myzocallis asclepiadis was negatively affected by increasing cardenolide concentrations of the host plant. Sequestration of cardenolides increased with diet specialization, with M. asclepiadis accumulating twice as much as any other species, perhaps explaining its susceptibility to plant cardenolides., Heritable plant traits differentially impacted co-occurring insect herbivores within the same guild. Generalist aphids were susceptible to variation in plant vigour but not defensive compounds. Increased host specialization resulted in lower resource-use efficiency, increased phloem throughput and ultimately higher cardenolide sequestration. Variation in these traits is thus likely to determine the relative distribution of generalist and specialist herbivores on plants in natural communities. [ABSTRACT FROM AUTHOR]

Body condition indices, measures of body 'plumpness' or mass relative to frame size, are often used as a proxy for lipid reserves or fitness-related traits of animals and assumed to be positively related to fitness., The quantification and analysis of body condition indices has been the subject of debate for decades. Here, we summarize three additional concerns with the use of body condition indices., First, body condition index is often poorly correlated with lipid content in animals. Second, even if body condition index and lipid content are correlated, lipid content of an animal may not be the most important aspect of body composition influencing fitness. Finally, neither body condition index nor lipid reserves are likely to be directly positively related to fitness in animals, as many animals homeostatically regulate intermediate levels of condition index or lipid reserves, with both higher and lower values incurring fitness costs., A wide range of analytical methods, including some relatively inexpensive and simple measures, are available for more detailed measures of animal body composition or fitness-related traits. Replacing body condition indices with more direct measures of body composition - even relatively simple measures - can inform understanding of the physiological mechanisms underlying animal responses in a wide range of behavioural, ecological and evolutionary studies. [ABSTRACT FROM AUTHOR]

The relationship between abiotic stress and fitness in an individual is usually described by the intensity and duration of stress. Yet in natural systems, variability in abiotic stress is common. Since individuals have physiological and fitness responses to single bouts of stress, frequency of stress may also determine the lifetime success of an organism. However, the majority of laboratory studies have focused only on the effects of single stress events., We investigated the relative importance of stress parameters including duration, intensity and number of cold events on the short-term physiology and long-term fitness in the freeze-avoiding eastern spruce budworm Choristoneura fumiferana (Lepidoptera: Tortricidae, Clemens)., We exposed overwintering 2nd-instar larvae of C. fumiferana to −5 °C, −10 °C, −15 °C or −20 °C, for either a single exposure of 120 h or repeated 12 h exposures (3, 6 or 10 exposures). Changes in short-term physiology were quantified by cryoprotectant content, energetic stores and supercooling point. Long-term fitness effects were measured by rearing individuals after overwintering and recording successful eclosion as adults, development time from 2nd instar to adult, and adult size., We found that long-term survival of C. fumiferana was most strongly affected by the number of low-temperature stress events rather than intensity or duration, despite increased investment into cryoprotection at the expense of glycogen reserves. Sublethal measures such as adult size were unaffected by low-temperature stress., Thus, we show that frequency of stress is an important, yet frequently neglected, parameter in the study of the effects of abiotic stress. The responses we documented here suggest that frequency of stress may be an additional important parameter for modelling the effects of abiotic stress on populations. [ABSTRACT FROM AUTHOR]