Acclimation and transgenerational plasticity support increased cadmium tolerance in Gammarus populations exposed to natural metal contamination in headwater streams

Considering long-term population effects of chronic exposure to contaminants remains limited in ecological risk assessment. Field evidence that multigenerational exposure influences organisms' sensitivity is still scarce, and mechanisms have yet to be elucidated in the environmental context. This study focuses on the crustacean Gammarus fossarum, for which an increased tolerance to cadmium (Cd) has previously been reported in a naturally low-contaminated headwater stream. Our objectives were to investigate whether Cd tolerance is a common phenomenon in headwater populations, and to elucidate the nature of the tolerance and its intergenerational transmission. For this, we carried out an in-depth in situ characterization of Cd exposure (gammarids' caging) and levels of tolerance in nine populations on a regional scale, as well as laboratory maintenance and cross-breeding of contaminated and uncontaminated populations. Acute tolerance levels correlate positively with bioavailable Cd contamination levels among streams. The contaminated and non-contaminated populations differ about two-fold in sensitivity to Cd. Tolerance was found in all age classes of contaminated populations, it can be transiently lost during the year, and it was transmissible to offspring. In addition, tolerance levels dropped significantly when organisms were transferred to a Cd-free environment for two months. These organisms also ceased producing tolerant offspring, confirming a non-genetic transmission of Cd tolerance between generations. These findings support that Cd tolerance corresponds to non-genetic acclimation combined with transgenerational plasticity. Moreover, cross-breeding revealed that tolerance transmission to offspring is not limited to maternal effect. We suggest epigenetics as a plausible mechanism for the plasticity of Cd sensitivity observed in the field. Our results therefore highlight the neglected role of plasticity and non-genetic transmission of modified sensitivities during the long-term exposure of natural populations to environmental contamination.

Parental cadmium exposure during the spawning period reduces cadmium sensitivity through the antioxidant system in rare minnow (Gobiocypris rarus) larvae

Cadmium (Cd) is a noxious heavy metal widely dispersed in aquatic systems. Parental Cd exposure of fish species at environmental concentrations has been shown to cause deformities and stunted growth in their offspring. However, the long-term effects and the mechanisms underlying parental Cd exposure in fish species on Cd sensitivity in their offspring remain unclear. To explore the impacts of parental Cd exposures on Cd sensitivity, rare minnow (Gobiocypris rarus) larvae whose parents were exposed to Cd at 0, 5 or 10 μg/L for 28 days were established. Results showed that parental Cd exposure in rare minnow increased the Cd content of its larvae. In terms of malformation rate, mortality rate and total length at 7 days of rare minnow larvae, parental Cd exposure at 5 or 10 μg/L reduced Cd sensitivity. Further mechanistic investigation demonstrated that parental Cd exposure significantly upregulated the expression of antioxidant gene regulated by nuclear factor erythroid 2-related factor 2 (Nrf2) and nuclear factor-kappa B (NF-кB) in rare minnow larvae. In addition, parental Cd exposure significantly elevated the level of reactive oxygen species (ROS) and malondialdehyde (MDA), but markedly decreased catalase (CAT), superoxide dismutase (SOD) and oxidized glutathione (GST) activity. The impact of parental Cd exposure to metallothionein (MT) content and the expression of MT mRNA, a detoxifying metallothionein, showed that parental Cd exposure of rare minnow induced oxidative stress in the larvae. Meanwhile, these results indicated that parental Cd exposure in rare minnow reduced the Cd sensitivity of the larvae via activating the Nrf2-mediated antioxidant system. This project helps us to further understand the toxicological mechanism of Cd in fish species and properly assess its potential ecological risk.

The trade-offs of foraging at landfills: Landfill use enhances hatching success but decrease the juvenile survival of their offspring on white storks (Ciconia ciconia)

During the last decades, landfills have become a valuable food source for wildlife, being in some cases determinants of large avian population increases. Superabundant food resources at landfills can increase reproductive and/or survival parameters; however, negative effects such as intoxication, plastic ingestion, skeletal deformities, unbalanced oxidative stress, and other health problems have also been reported. White stork (Ciconia ciconia) commonly benefits from landfill resources. Here, we evaluate potential landfill effects on demographic parameters (reproduction and offspring survival) at the individual level in a single population. Our results show that a more intense use of landfills by breeders has a positive effect on hatching success but a negative effect on juvenile survival probability after emancipation, at least during the first year of life. High amount of food and proximity to landfill may explain their beneficial effect on reproductive parameters. On the other hand, poor quality food, pollutants, and pathogens acquired during early development from a diet based on refuse may be responsible for reduced future survival probability. Consequently, both positive and negative effects were detected, being foraging at landfills at low to medium levels the better strategy. Although our study shows that intense foraging on rubbish can imply both costs and benefits at an individual level, the benefits of superabundant food provisioning observed at population level by other studies cannot be ignored. Management actions should be designed to improve natural food resources, reduce non-natural mortality and/or human disturbances to guarantee the species viability under current European Union regulations designed to ban open-air landfills in a near future.

Anticipatory parental effects in a subtropical lizard in response to experimental warming

Parental effects may produce adaptive or maladaptive plasticity that either facilitates persistence or increases the extinction risk of species and populations in a changing climate. However, empirical evidence of transgenerational adaptive plastic responses to climate change is still scarce. Here we conducted thermal manipulation experiments with a factorial design in a Chinese lacertid lizard (Takydromus septentrionalis) to identify the fitness consequences of parental effects in response to climate warming. Compared to present climate conditions, a simulated warming climate significantly advanced the timing of oviposition, depressed the immune capability of post-partum females, and decreased the hatching success of embryos, but did not affect female reproductive output (clutch size and egg mass). These results indicate that maternal warming negatively affects female health, and embryonic hatchability. More interestingly, we found that offspring from parents exposed to warming environments survived well under a simulated warming climate, but not under a present climate scenario. Accordingly, our study demonstrates anticipatory parental effects in response to a warming climate in an ectothermic vertebrate. However, the fitness consequences of this parental effect will depend on future climate change scenarios.

Parental exposure to heavy fuel oil induces developmental toxicity in offspring of the sea urchin Strongylocentrotus intermedius

The present study investigated the toxic effects of parental (maternal/paternal) exposure to heavy fuel oil (HFO) on the adult reproductive state, gamete quality and development of the offspring of the sea urchin Strongylocentrotus intermedius. Adult sea urchins were exposed to effluents from HFO-oiled gravel columns for 7 days to simulate an oil-contaminated gravel shore, and then gametes of adult sea urchins were used to produce embryos to determine developmental toxicity. For adult sea urchins, no significant difference in the somatic size and weight was found between the various oil loadings tested, while the gonad weight and gonad index were significantly decreased at higher oil loadings. The spawning ability of adults and fecundity of females significantly decreased. For gametes, no effect was observed on the egg size and fertilization success in any of the groups. However, a significant increase in the percentage of anomalies in the offspring was observed and then quantified by an integrative toxicity index (ITI) at 24 and 48 h post fertilization. The offspring from exposed parents showed higher ITI values with more malformed embryos. The results confirmed that parental exposure to HFO can cause adverse effects on the offspring and consequently affect the recruitment and population maintenance of sea urchins.

Environmental causes and transgenerational consequences of ecdysteroid hormone provisioning in Acheta domesticus

An animal's phenotype may be shaped by its genes, but also reflects its own environment and often that of its parents. Nongenetic parental effects are often mediated by steroid hormones, and operate between parents and offspring through mechanisms that are well described in vertebrate and model systems. However, less is understood about the strength and frequency of hormone mediated nongenetic parental effects across more than one generation of descendants, and in nonmodel systems. Here we show that the concentration of active ecdysteroid hormones provided by a female house cricket (Acheta domesticus) affects the growth rate of her offspring. We also reveal that variation in the active ecdysteroid hormones provided by a female house cricket to her eggs derives primarily from the quality of nutrition available to her maternal grandmother, regardless of genetic background. This finding is in stark contrast to most previous work that documents a decline in the strength of environmentally based parental effects with each passing generation. Strong grandparental effects may be adaptive under predictable, cyclical changes in the environment. Our results also suggest that hormone-mediated grand-maternal effects represent an important potential mechanism by which organisms can respond to environmental variability, and that further study of hormone-mediated carryover effects in this context could be profitable.

A novel type of gene interaction in D. melanogaster

The genes interact according to classical mechanisms, namely, complementation, modification, polymery, and epistasis, in the cells and organisms carrying these genes. Here we describe a novel type of gene interaction when the interacting genes reside in parents, whereas the interaction event takes place in their progenies lacking these genes. The conditional mutations in the D. melanogaster male X chromosome caused the "prohibition on producing daughters" in its offspring. The chromosomal rearrangements in chromosomes 2 and 3 of its female partner removed the prohibition. The phenomena of "prohibition" and "removal of prohibition" appeared as a parental effect in both the male and female. Both phenomena ensued from the presence of the studied mutations in parents rather than their unviable or survived progenies. Thus, the gene interaction when the genes themselves are absent at the site of interaction and during the interaction event takes place in drosophila.

Plasticity and regeneration of gonads in the annelid Pristina leidyi

Background

Gonads are specialized gamete-producing structures that, despite their functional importance, are generated by diverse mechanisms across groups of animals and can be among the most plastic organs of the body. Annelids, the segmented worms, are a group in which gonads have been documented to be plastic and to be able to regenerate, but little is known about what factors influence gonad development or how these structures regenerate. In this study, we aimed to identify factors that influence the presence and size of gonads and to investigate gonad regeneration in the small asexually reproducing annelid, Pristina leidyi.

Results

We found that gonad presence and size in asexual adult P. leidyi are highly variable across individuals and identified several factors that influence these structures. An extrinsic factor, food availability, and two intrinsic factors, individual age and parental age, strongly influence the presence and size of gonads in P. leidyi. We also found that following head amputation in this species, gonads can develop by morphallactic regeneration in previously non-gonadal segments. We also identified a sexually mature individual from our laboratory culture that demonstrates that, although our laboratory strain reproduces only asexually, it retains the potential to become fully sexual.

Conclusions

Our findings demonstrate that gonads in P. leidyi display high phenotypic plasticity and flexibility with respect to their presence, their size, and the segments in which they can form. Considering our findings along with relevant data from other species, we find that, as a group, clitellate annelids can form gonads in at least four different contexts: post-starvation refeeding, fission, morphallactic regeneration, and epimorphic regeneration. This group is thus particularly useful for investigating the mechanisms involved in gonad formation and the evolution of post-embryonic phenotypic plasticity.

Electronic supplementary material

The online version of this article (doi:10.1186/s13227-016-0059-1) contains supplementary material, which is available to authorized users.

Effect of growth temperature on glucosinolate profiles in Arabidopsis thaliana accessions

Glucosinolates are plant secondary metabolites with important roles in plant defence against pathogens and pests and are also known for their health benefits. Understanding how environmental factors affect the level and composition of glucosinolates is therefore of importance in the perspective of climate change. In this study we analysed glucosinolates in Arabidopsis thaliana accessions when grown at constant standard (21 °C), moderate (15 °C) and low (9 °C) temperatures during three generations. In most of the tested accessions moderate and pronounced chilling temperatures led to higher levels of glucosinolates, especially aliphatic glucosinolates. Which temperature yielded the highest glucosinolate levels was accession-dependent. Transcriptional profiling revealed also accession-specific gene responses, but only a limited correlation between changes in glucosinolate-related gene expression and glucosinolate levels. Different growth temperatures in one generation did not consistently affect glucosinolate composition in subsequent generations, hence a clear transgenerational effect of temperature on glucosinolates was not observed.

Phenotypic Evolution With and Beyond Genome Evolution

DNA does not make phenotypes on its own. In this volume entitled "Genes and Phenotypic Evolution," the present review draws the attention on the process of phenotype construction-including development of multicellular organisms-and the multiple interactions and feedbacks between DNA, organism, and environment at various levels and timescales in the evolutionary process. First, during the construction of an individual's phenotype, DNA is recruited as a template for building blocks within the cellular context and may in addition be involved in dynamical feedback loops that depend on the environmental and organismal context. Second, in the production of phenotypic variation among individuals, stochastic, environmental, genetic, and parental sources of variation act jointly. While in controlled laboratory settings, various genetic and environmental factors can be tested one at a time or in various combinations, they cannot be separated in natural populations because the environment is not controlled and the genotype can rarely be replicated. Third, along generations, genotype and environment each have specific properties concerning the origin of their variation, the hereditary transmission of this variation, and the evolutionary feedbacks. Natural selection acts as a feedback from phenotype and environment to genotype. This review integrates recent results and concrete examples that illustrate these three points. Although some themes are shared with recent calls and claims to a new conceptual framework in evolutionary biology, the viewpoint presented here only means to add flesh to the standard evolutionary synthesis.

Do female newts modify thermoregulatory behavior to manipulate egg size?

Reproductive females manipulate offspring phenotypes by modifying conditions during embryogenesis. In ectotherms, the environmental control over embryogenesis is often realized by changes in maternal thermoregulation during gravidity. To determine if reproduction influences thermoregulatory behavior in species where females lay eggs shortly after fertilization (strict oviparity), we compared preferred body temperatures (Tp) between reproductive (egg-laying) and non-reproductive female newts, Ichthyosaura alpestris. Next, we exposed reproductive females to temperatures mimicking Tp ranges of reproductive and non-reproductive individuals to find out whether the maternally modified thermal regime influences ovum and jelly coat volume, and early cleavage rates at the time of oviposition. In the thermal gradient, reproductive females maintained their body temperatures within a narrower range than non-reproductive individuals. The exposure of ovipositing females to temperatures preferred during their reproductive and non-reproductive period had a negligible influence on egg size and early cleavage rates. We conclude that the modification of maternal thermoregulatory behavior provides a limited opportunity to manipulate egg traits in newts.

Parents' and peers' contribution to risky driving of male teen drivers

The current study joins efforts devoted to understanding the associations of parents' personality, attitude, and behavior, and to evaluating the added contribution of peers to the driving behavior of young drivers during their solo driving. The study combines data gathered using in-vehicle data recorders from actual driving of parents and their male teen driver with data collected from self-report questionnaires completed by the young drivers. The sample consists of 121 families, who participated in the study for 12 months, beginning with the licensure of the teen driver. The current examination concentrates on the last 3 months of this first year of driving. The experimental design was based on a random control assignment into three treatment groups (with different forms of feedback) and a control group (with no feedback). Findings indicate that the parents' (especially the fathers') sensation seeking, anxiety, and aggression, as well as their risky driving events rate were positively associated with higher risky driving of the young driver. In addition, parents' involvement in the intervention, either by feedback or by training, led to lower risky driving events rate of young drivers compared to the control group. Finally, higher cohesion and adaptability mitigated parents' model for risky driving, and peers norms' of risky driving were associated with higher risk by the teen drivers. We conclude by claiming that there is an unequivocal need to look at a full and complex set of antecedents in parents' personality, attitudes, and behavior, together with the contribution of peers to the young drivers' reckless driving, and address the practical implications for road safety.

A test of maternal programming of offspring stress response to predation risk in threespine sticklebacks

Non-genetic maternal effects are widespread across taxa and challenge our traditional understanding of inheritance. Maternal experience with predators, for example, can have lifelong consequences for offspring traits, including fitness. Previous work in threespine sticklebacks showed that females exposed to simulated predation risk produced eggs with higher cortisol content and offspring with altered anti-predator behavior. However, it is unknown whether this maternal effect is mediated via the offspring glucocorticoid stress response and if it is retained over the entire lifetime of offspring. Therefore, we tested the hypothesis that maternal exposure to simulated predation risk has long-lasting effects on the cortisol response to simulated predation risk in stickleback offspring. We measured circulating concentrations of cortisol before (baseline), 15 min after, and 60 min after exposure to a simulated predation risk. We compared adult offspring of predator-exposed mothers and control mothers in two different social environments (alone or in a group). Relative to baseline, offspring plasma cortisol was highest 15 min after exposure to simulated predation risk and decreased after 60 min. Offspring of predator-exposed mothers differed in the cortisol response to simulated predation risk compared to offspring of control mothers. In general, females had higher cortisol than males, and fish in a group had lower cortisol than fish that were by themselves. The buffering effect of the social environment did not differ between maternal treatments or between males and females. Altogether the results show that while a mother's experience with simulated predation risk might affect the physiological response of her adult offspring to a predator, sex and social isolation have much larger effects on the stress response to predation risk in sticklebacks.