Sublethal larval exposure to imidacloprid impacts adult behaviour in Drosophila melanogaster

Pesticides are now chronically found in numerous ecosystems incurring widespread toxic effects on multiple organisms. For insects, the larvae are very exposed to pesticide pollution and the acute effect of insecticides on larvae has been characterized in a range of species. However, the carry‐on effects in adults of sublethal exposure occurring in larvae are not well characterized. Here, we use a collection of strains of Drosophila melanogaster differing in their larval resistance to a commonly used insecticide, imidacloprid, and we test the effect of larval exposure on behavioural traits at the adult stage. Focusing on locomotor activity and on courtship and mating behaviour, we observed a significant carry‐on effect of imidacloprid exposure. The heritability of activity traits measured in flies exposed to imidacloprid was higher than measured in controls and in these, courtship traits were genetically less correlated from mating success. Altogether, we did not observe a significant effect of the larval insecticide resistance status on adult behavioural traits, suggesting that selection for resistance in larvae does not involve repeatable behavioural changes in adults. This lack of correlation between larval resistance and adult behaviour also suggests that resistance at the larval stage does not necessarily result in increased behavioural resilience at a later life stage. These findings imply that selection for resistance in larvae as well as for behavioural resilience to sublethal exposure in adult will combine and impose a greater evolutionary constraint. Our conclusions further substantiate the need to encompass multiple trait measures and life stages in toxicological assays to properly assess the environmental impact of pesticides.     

Stem cells and genetic disease

Abstract.  Stem cell research is now a very broad field encompassing cells derived from all stages of life from the embryonic stem cells of the early blastocyst through to the adult stem cells of many tissues of the body. Adult stem cells from a variety of tissues are proving to be pluripotent and can differentiate into cell types different from the tissues from which they derive. Pre-clinical animal models indicate that adult stem cells do not cause tumours, not even, teratomas when transplanted. These properties, combined with the possibility of autologous transplantation, indicate significant advantages over embryonic stem cells in many proposed clinical applications.     

Induction of reverse development in two marine Hydrozoans

Cnidarians are unique organisms in the animal kingdom because of their unequalled potential to undergo reverse development (RD). The life cycle of some species can temporarily shift ordinary, downstream development from zygote to adult into the opposite ontogenetic direction by back-transformation of some life stages. The potential for RD in cnidarians offers the possibility to investigate how integrative signalling networks operate to control directionality of ontogeny (reverse vs. normal development). Striking examples are found in some hydrozoans, where RD of medusa bud or liberated medusa stages leads to rejuvenation of the post-larval polyp stage. Artificial stress may determine ontogeny reversal. We describe here the results of experimental assays on artificial induction of RD by different chemical and physical inducers on two marine hydrozoans, Turritopsis dohrnii and Hydractinia carnea, showing a different potential for RD. A cascade of morphogenetic events occurs during RD by molecular mechanisms and cellular patterns recalling larval metamorphosis. For the first time, we show here that exposure to cesium chloride (CsCl), an inducer of larval metamorphosis, may also induce RD, highlighting similarities and differences between these two master ontogenetic processes in cnidarians.     

Neonatal programming of innate immune function

The early life environment can be crucial in influencing the development of an animal's long-term physiology. There is now much evidence to suggest that perinatal challenges to an animal's immune system will result in changes in adult rat behavior, physiology, and molecular pathways following a single inflammatory event during development caused by the bacterial endotoxin lipopolysaccharide (LPS). In particular, it is now apparent that neonatal LPS administration can influence the adult neuroimmune response to a second LPS challenge through hypothalamic-pituitary-adrenal axis modifications, some of which are caused by alterations in peripheral prostaglandin synthesis. These pronounced changes are accompanied by a variety of alterations in a number of disparate aspects of endocrine physiology, with significant implications for the health and well-being of the adult animal. In this review, we discuss the newly elucidated mechanisms by which neonatal immune challenge can permanently alter an animal's endocrine and metabolic physiology and the implications this has for various disease states.     

Agarose Microchambers for Long-term Calcium Imaging of Caenorhabditis elegans

Behavior is controlled by the nervous system. Calcium imaging is a straightforward method in the transparent nematode Caenorhabditis elegans to measure the activity of neurons during various behaviors. To correlate neural activity with behavior, the animal should not be immobilized but should be able to move. Many behavioral changes occur during long time scales and require recording over many hours of behavior. This also makes it necessary to culture the worms in the presence of food. How can worms be cultured and their neural activity imaged over long time scales? Agarose Microchamber Imaging (AMI) was previously developed to culture and observe small larvae and has now been adapted to study all life stages from early L1 until the adult stage of C. elegans. AMI can be performed on various life stages of C. elegans. Long-term calcium imaging is achieved without immobilizing the animals by using short externally triggered exposures combined with an electron multiplying charge-coupled device (EMCCD) camera recording. Zooming out or scanning can scale up this method to image up to 40 worms in parallel. Thus, a method is described to image behavior and neural activity over long time scales in all life stages of C. elegans.     

SpatialDemography: a spatially explicit,stage‐structured,metacommunity model

The responses of species and populations to changes in the environment (e.g. changes in climate and land use) are often complex and difficult to predict. We have created the SpatialDemography model (R package: spatialdemography). The model is a spatially explicit, stage‐structured, matrix‐based metacommunity model, with the potential for modeling species’ and populations’ potential responses to environmental heterogeneity and change. The SpatialDemography model assumes a cellular landscape populated by organisms with four life stages: a mobile dispersing stage, two sessile non‐reproductive stages, and a reproductive adult stage. Individuals are assumed to originate at the center of a given cell and disperse according to a specified dispersal kernel (e.g. log‐normal). All adult individuals are capable of producing offspring. The model approach and framework are described in the context of a hypothetical example with multiple competing species in a four cell landscape. In this example simulation, both spatial location and species interactions were important for understanding population dynamics. SpatialDemography can be applied to questions where an understanding of transient and long‐term demographic responses to spatiotemporal changes is desired. It is primarily applicable to metapopulations and metacommunities of organisms with early dispersal and sessile adults (i.e. modular organisms such as plants and some marine organisms). SpatialDemography differs from other population models in that it is spatially explicit, can incorporate biotic interactions, and is implemented in R.     

Prenatal exposure to glucocorticoids and adult disease

There is evidence to suggest that an individual's susceptibility to cardiovascular disease cannot be entirely explained by differences in life style factors (i.e., low physical activity, high fat/salt diet), or genetic causes, but may also be influenced by factors encountered during intrauterine life. Epidemiological studies found the link between low birth weight for gestational age (a broad index of sub-optimal intrauterine environment) and increased incidence of cardiovascular and metabolic diseases in adulthood. Many animal models in which the intrauterine environment was altered during early/late or throughout gestation demonstrated long-term effects on adult health. In general stress in early gestation is more likely to be associated with adult cardiovascular disease including hypertension, whereas late gestation stress may also be associated with adult hypotension in addition to metabolic/endocrine abnormalities. Two systems have been widely hypothesised to serve as mechanisms via which adverse prenatal influences impinge on adult cardiovascular and metabolic disease; hippocampal-hypothalamo-pituitary-adrenal axis (HHPA) and renin-angiotensin system (RAS). Interestingly, at least in our animal model of adult hypertension after brief/early prenatal glucocorticoid exposure, HHPA axis is not altered when studied either in late gestation or at several stages during adulthood. However, our more recent results, using the same animal model, suggest a major role for the central and renal RAS. This review will mainly focus on animal models and potential mechanisms via which a perturbed intrauterine environment (undernutrition or steroid exposure) lead to adult cardiovascular and/or metabolic disease.     

Sublethal concentrations of waterborne copper induce cellular stress and cell death in zebrafish embryos and larvae

Copper is an essential ion that forms part of the active sites of many proteins. At the same time, an excess of this metal produces free radicals that are toxic for cells and organisms. Fish have been used extensively to study the effects of metals, including copper, present in food or the environment. It has been shown that different metals induce different adaptive responses in adult fish. However, until now, scant information has been available about the responses that are induced by waterborne copper during early life stages of fish. Here, acute toxicity tests and LC50 curves have been generated for zebrafish larvae exposed to dissolved copper sulphate at different concentrations and for different treatment times. We determined that the larvae incorporate and accumulate copper present in the medium in a concentration-dependent manner, resulting in changes in gene expression. Using a transgenic fish line that expresses enhanced green fluorescent protein (EGFP) under the hsp70 promoter, we monitored tissue-specific stress responses to waterborne copper by following expression of the reporter. Furthermore, TUNEL assays revealed which tissues are more susceptible to cell death after exposure to copper. Our results establish a framework for the analysis of whole-organism management of excess external copper in developing aquatic animals.     

Rapid shift in thermal resistance between generations through maternal heat exposure

Given the current rapid climate change, understanding the mechanisms underlying heat tolerance and its plasticity is an important goal of global change biology. Soil fauna communities are especially vulnerable because of their limited dispersal ability. It is generally recognized that transgenerational effects can contribute to the expression of phenotypic plasticity. Nevertheless, transgenerational plasticity in belowground organisms has received relatively little attention in the context of climate change, despite their major role in soil functioning. Here we test for transgenerational effects of heat shock exposure in the soil arthropod Orchesella cincta, a springtail species that regularly experiences heat stress conditions in its natural environment. We exposed females to heat stress, and subsequently investigated the effects of the same stress on the survival of their offspring. Thermal resistance of the progeny from treated and untreated mothers was compared at three life stages: egg, juvenile and adult. We provide evidence that exposure to heat shock induces a life stage‐dependent increase in thermal resistance in the subsequent generation. The induced adaptive maternal effect persisted into the adult stage of the progeny. However, there is also a tradeoff resulting in reduced clutch size of treated females. These results are of broad significance to understanding the potential of organisms to cope with a changing climate.     

Mouse ovarian germ cell cysts undergo programmed breakdown to form primordial follicles

In many organisms, early germline development takes place within cysts of interconnected cells that form by incomplete cytokinesis and later undergo programmed breakdown. We recently identified similar cell clusters within the fetal mouse ovary, but the fate and functional significance of these germ cell cysts remained unclear. Here, we show that mouse cysts undergo programmed breakdown between 20.5-22.5 dpc, during which approximately 33% of the oocytes survive to form primordial follicles. This process accounts for most of the perinatal reduction in germ cell numbers and germ cell apoptosis reported by previous authors, and suggests that perinatal germ cell loss is a developmentally regulated process that is distinct from the follicular atresia that occurs during adult life. Our observations also suggest a novel function for a transient cyst stage of germ cell development. Prior to breakdown, mitochondria and ER reorganize into perinuclear aggregates, and can be seen within the ring canals joining adjacent germ cells. Cysts may ensure that oocytes destined to form primordial follicles acquire populations of functional mitochondria, through an active process that has been evolutionarily conserved.     

Trait Performance Correlations across Life Stages under Environmental Stress Conditions in the Common Frog,Rana temporaria

If an organism''s juvenile and adult life stages inhabit different environments, certain traits may need to be independently adapted to each environment. In many organisms, a move to a different environment during ontogeny is accompanied by metamorphosis. In such organisms phenotypic induction early in ontogeny can affect later phenotypes. In laboratory experiments we first investigated correlations between body morphology and the locomotor performance traits expressed in different life stages of the common frog, Rana temporaria: swimming speed and acceleration in tadpoles; and jump-distance in froglets. We then tested for correlations between these performances across life stages. We also subjected tadpoles to unchanging or decreasing water levels to explore whether decreasing water levels might induce any carry-over effects. Body morphology and performance were correlated in tadpoles; morphology and performance were correlated in froglets: hence body shape and morphology affect performance within each life stage. However, performance was decoupled across life stages, as there was no correlation between performance in tadpoles and performance in froglets. While size did not influence tadpole performance, it was correlated with performance of the metamorphosed froglets. Experiencing decreasing water levels accelerated development time, which resulted in smaller tadpoles and froglets, i.e., a carry-over effect. Interestingly, decreasing water levels positively affected the performance of tadpoles, but negatively affected froglet performance. Our results suggest that performance does not necessarily have to be correlated between life stages. However, froglet performance is size dependent and carried over from the tadpole stage, suggesting that some important size-dependent characters cannot be decoupled via metamorphosis.     

Stress exposure in early post-natal life reduces telomere length: an experimental demonstration in a long-lived seabird

Exposure to stressors early in life is associated with faster ageing and reduced longevity. One important mechanism that could underlie these late life effects is increased telomere loss. Telomere length in early post-natal life is an important predictor of subsequent lifespan, but the factors underpinning its variability are poorly understood. Recent human studies have linked stress exposure to increased telomere loss. These studies have of necessity been non-experimental and are consequently subjected to several confounding factors; also, being based on leucocyte populations, where cell composition is variable and some telomere restoration can occur, the extent to which these effects extend beyond the immune system has been questioned. In this study, we experimentally manipulated stress exposure early in post-natal life in nestling European shags (Phalacrocorax aristotelis) in the wild and examined the effect on telomere length in erythrocytes. Our results show that greater stress exposure during early post-natal life increases telomere loss at this life-history stage, and that such an effect is not confined to immune cells. The delayed effects of increased telomere attrition in early life could therefore give rise to a ‘time bomb’ that reduces longevity in the absence of any obvious phenotypic consequences early in life.     

Biological preservation of plant derived animal feed with antifungal microorganisms: safety and formulation aspects

During storage of moist animal feed, growth of detrimental fungi causing spoilage, or being mycotoxigenic or pathogenic, is a severe problem. Addition of biopreservative yeasts or lactic acid bacteria can significantly reduce this problem. However, their use requires several careful considerations. One is the safety to the animal, humans and the environment, tightly connected to legal aspects and the need for pre-market authorisation when supplementing feed with microorganisms. Although both yeasts and lactic acid bacteria are considered comparatively safe organisms due to low production of toxic metabolites, it is of great importance to understand the mechanisms behind the biopreservative abilities. Another important issue concerns practical aspects, such as the economic production of large amounts of the organisms and the development of a suitable formulation giving the organisms a long shelf life. These aspects are discussed and a recommendation of this review is that both safety and formulation aspects of a specific microbe should be considered at an early stage in the selection of new organisms with biopreservation potential.     

Local adaptation of reproductive performance during thermal stress

Considerable evidence exists for local adaptation of critical thermal limits in ectotherms following adult temperature stress, but fewer studies have tested for local adaptation of sublethal heat stress effects across life‐history stages. In organisms with complex life cycles, such as holometabolous insects, heat stress during juvenile stages may severely impact gametogenesis, having downstream consequences on reproductive performance that may be mediated by local adaptation, although this is rarely studied. Here, we tested how exposure to either benign or heat stress temperature during juvenile and adult stages, either independently or combined, influences egg‐to‐adult viability, adult sperm motility and fertility in high‐ and low‐latitude populations of Drosophila subobscura. We found both population‐ and temperature‐specific effects on survival and sperm motility; juvenile heat stress decreased survival and subsequent sperm motility and each trait was lower in the northern population. We found an interaction between population and temperature on fertility following application of juvenile heat stress; although fertility was negatively impacted in both populations, the southern population was less affected. When the adult stage was also subject to heat stress, the southern population exhibited positive carry‐over effects whereas the northern population's fertility remained low. Thus, the northern population is more susceptible to sublethal reproductive consequences following exposure to juvenile heat stress. This may be common in other organisms with complex life cycles and current models predicting population responses to climate change, which do not take into account the impact of juvenile heat stress on reproductive performance, may be too conservative.     

Traffic noise exposure affects telomere length in nestling house sparrows

In a consistently urbanizing world, anthropogenic noise has become almost omnipresent, and there are increasing evidence that high noise levels can have major impacts on wildlife. While the effects of anthropogenic noise exposure on adult animals have been widely studied, surprisingly, there has been little consideration of the effects of noise pollution on developing organisms. Yet, environmental conditions experienced in early life can have dramatic lifelong consequences for fitness. Here, we experimentally manipulated the acoustic environment of free-living house sparrows (Passer domesticus) breeding in nest boxes. We focused on the impact of such disturbance on nestlings’ telomere length and fledging success, as telomeres (the protective ends of chromosomes) appear to be a promising predictor of longevity. We showed that despite the absence of any obvious immediate consequences (growth and fledging success), nestlings reared under traffic noise exposure exhibited reduced telomere lengths compared with their unexposed neighbours. Although the mechanisms responsible for this effect remain to be determined, our results provide the first experimental evidence that noise alone can affect a wild vertebrate''s early-life telomere length. This suggests that noise exposure may entail important costs for developing organisms.     

Developmental exposure to lead and late life abnormalities of nervous system

Role of developmental exposure to environmental agents in altering the disease process is well known. Exposure to chemical agents at critical periods of development may cause some permanent changes in the functioning of various vital systems including the nervous system in the organisms. It is not surprising to see an extensive response due to exposure to chemical agents early in life as the organ systems are more vulnerable to chemical insults during developmental stages. In some cases the response to low level environmental insults may not be obvious until adult or old age. Results from several studies have shown such latency in response to the nervous system leading to neurodegeneration in old age. Studies conducted in murine and primate models provided ample evidence for the association of developmental exposure to low levels of heavy metal lead (Pb) and Alzheimer's disease-like pathology during senescence. It is not clear about the reasons behind such response; however, the contribution of epigenetic mechanisms could explain the role of early events in life in inducing the late life abnormalities of nervous system. It is possible that environmental agents epigenetically modulate the gene regulation to persist the response silent for a long period of time and to result pathological outcomes significantly later in life. This article will summarize the association of early life exposure to environmental agents and late-life abnormalities with an emphasis on developmental exposure to Pb and neurodegeneration in old age.     

The evolutionary pattern of early life history in water currents

Explanation of the characteristics of the early developmental stage of organisms is an important problem in evolutionary biology. In studies to date, evolutionary biologists have proposed some theories that successfully explain egg size variation. Mesoscale water movements may transport early life stage organisms in the aquatic biosphere. We propose a novel biological view to explain the duration of the retention period at the spawning ground and egg size variations in aquatic organisms with a planktonic stage at least during the early part of their life history. We develop a life history model of the early life stage of such aquatic organisms that takes into account their adaptations to water currents and biotic environmental gradients in the currents. We hypothesize that the distance from the spawning grounds to the nursery grounds and the biological richness of the currents affect the adaptive life history design of these aquatic organisms, including adaptive retention time at the spawning ground and egg size. Various studies of fish biology describe in passing phenomena that suggest the validity of our deductions, but explicit empirical attempts to evaluate our predictions in the field of evolutional biology are needed.     

Early stress and genetic influences on hypothalamic-pituitary-adrenal axis functioning in adulthood.

During early development, environmental challenges set the stage for permanent changes in the functioning of the pituitary-adrenal stress response. Since these data have been reported almost exclusively in single rat strains the role of phenotypic and genotypic factors in shaping the stress response is relatively unknown. This study examined whether the phenotypic/genetic profile of the rat influences the long-term response to challenge after early exposure to stress. Two strains of Sprague-Dawley rats were used in this study: one is a stress-induced animal model of "learned helpless" (LH) behavior and the other a resistant strain developed through selective breeding. Stress-induced adrenocorticotropic hormone (ACTH) and corticosterone release was monitored in adult congenital learned helpless (cLH) rats and congenital non-learned helpless (cNLH) rats. The rats were exposed to cold stress or maternal deprivation (on either postnatal day 7 or day 21). After the early acute stress exposure, animals remained undisturbed until challenged in adulthood (day 90) with footshock stress. In cLH animals (adults) early cold stress (particularly after acute stress on postnatal day 21) and maternal deprivation stress resulted in an enhancement of stress-induced ACTH release compared to nonstressed cLH and cNLH controls. In contrast, adrenal responsiveness was generally suppressed in cLH animals that were acutely stressed with cold stress or maternal deprivation stress early in life. The above results suggest that the genetic/phenotypic profile of the animal is a determinant in the changes observed in the adult stress response after early exposure to stressors.