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Global rising of average temperatures and increase in extreme climatic events may largely impact animal survival and reproduction. Yet, how variation in temperature may affect male fertility, in particular ejaculate traits, and whether this can in turn affect offspring fitness, is seldom addressed. Paternal effects may be of key importance as they could impact the rate and direction of evolutionary change in response to climate change. We tested the effects of temperature experienced by males on sperm traits, and asked whether the paternal environmental temperature affected offspring phenotype. We further explored the potential for paternal effects to be adaptive, which would occur when offspring fitness increased under the same environmental conditions experienced by the fathers. We exposed male field crickets to high or low temperatures at two life stages, either throughout development or as adults, and tested sperm traits (number and quality) and offspring fitness (hatching success and survival). We further assessed sperm traits in offspring, after they had also been exposed to the same or different temperature experienced by their father. We found that temperature affected sperm traits depending on the life‐stage of individuals. When the exposure was given during adulthood, males exposed to high temperature produced less sperm and of lower quality compared to males exposed to lower temperature, while if exposure was given during development, males exposed to high temperature produced more sperm and of better quality compared to males exposed to low temperatures. Offspring fitness was significantly affected by paternal temperature, evidence for anticipatory paternal effects on sperm traits was not found. Our study indicates that temperature can mediate cross‐generational effects, and that paternal effects may be mediated by changes in temperature and therefore much more widespread in nature than previously assumed. A plain language summary is available for this article. Plain Language Summary

Maternal effects triggered by changes in the environment (e.g., nutrition or crowding) can influence the outcome of offspring–parasite interactions, with fitness consequences for the host and parasite. Outside of the classic example of antibody transfer in vertebrates, proximate mechanisms have been little studied, and thus, the adaptive significance of maternal effects on infection is not well resolved. We sought to determine why food‐stressed mothers give birth to offspring that show a low rate of infection when the crustacean Daphnia magna is exposed to an orally infective bacterial pathogen. These more‐resistant offspring are also larger at birth and feed at a lower rate. Thus, reduced disease resistance could result from slow‐feeding offspring ingesting fewer bacterial spores or because their larger size allows for greater immune investment. To distinguish between these theories, we performed an experiment in which we measured body size, feeding rate, and susceptibility, and were able to show that body size is the primary mechanism causing altered susceptibility: Larger Daphnia were less likely to become infected. Contrary to our predictions, there was also a trend that fast‐feeding Daphnia were less likely to become infected. Thus, our results explain how a maternal environmental effect can alter offspring disease resistance (though body size), and highlight the potential complexity of relationship between feeding rate and susceptibility in a host that encounters a parasite whilst feeding. Food‐stressed Daphnia give birth to offspring that are larger, feed at a lower rate, and show a low rate of infection when exposed to an orally infective bacterial pathogen. This reduced disease resistance could result from slow‐feeding offspring ingesting fewer bacterial spores or because their larger size allows for greater immune investment. Our data show that the primary mechanism causing altered susceptibility was body size, with feeding rate being less important.

Trans‐generational immune priming (TGIP) describes the transfer of immune stimulation to the next generation. As stress and immunity are closely connected, we here address the question whether trans‐generational effects on immunity and resistance can also be elicited by a nonpathogen stress treatment of parents. General stressors have been shown to induce immunity to pathogens within individuals. However, to our knowledge, it is as of yet unknown whether stress can also induce trans‐generational effects on immunity and resistance. We exposed a parental generation (mothers, fathers, or both parents) of the red flour beetle Tribolium castaneum, a species where TGIP has been previously been demonstrated, to either a brief heat or cold shock and examined offspring survival after bacterial infection with the entomopathogen Bacillus thuringiensis. We also studied phenoloxidase activity, a key enzyme of the insect innate immune system that has previously been demonstrated to be up‐regulated upon TGIP. We quantified parental fecundity and offspring developmental time to evaluate whether trans‐generational priming might have costs. Offspring resistance was found to be significantly increased when both parents received a cold shock. Offspring phenoloxidase activity was also higher when mothers or both parents were cold‐shocked. By contrast, parental heat shock reduced offspring phenoloxidase activity. Moreover, parental cold or heat shock delayed offspring development. In sum, we conclude that trans‐generational priming for resistance could not only be elicited by pathogens or pathogen‐derived components, but also by more general cues that are indicative of a stressful environment. The interaction between stress responses and the immune system might play an important role also for trans‐generational effects. Trans‐generational immune priming describes the transfer of immune stimulation to offspring. Here we show that also the exposure of parents to non‐pathogen stress (cold shock) increased offspring resistance and immunity. This suggests that connections between stress and immunity also act across generations.

Reproductive performance is often age-dependent, showing patterns of improvement and/or senescence as well as trade-offs with other traits throughout the lifespan. High levels of extrinsic mortality (e.g., from predators) have been shown to sometimes, but not always, select for accelerated actuarial senescence in nature and in the lab. Here, we explore the inductive (i.e., plastic) effects of predation risk (i.e., nonlethal exposure to chemical cues from predators) on the reproductive success of freshwater snails (Physa acuta). Snails were reared either in the presence or absence of chemical cues from predatory crayfish and mated early in life or late in life (a 2 × 2 factorial design); we measured egg hatching and early post-hatching survival of their offspring. Both age and predation risk reduced reproductive success, illustrating that predation risk can have a cross-generational effect on the early survival of juveniles. Further, the decline in reproductive success was over three times faster under predation risk compared to the no-predator treatment, an effect that stemmed from a disproportionate, negative effect of predation risk on the post-hatching survival instead of hatching rate. We discuss our results in terms of a hypothesized consequence of elevated stress hormone levels.

Mothers are expected to use environmental cues to modify maternal investment to optimize their fitness. However, when the environment varies unpredictably, cues may not be an accurate proxy of future conditions. Under such circumstances, selection favors a diversifying maternal investment strategy. While there is evidence that the environment is becoming more uncertain, the extent to which mothers are able to respond to this unpredictability is generally unknown. In this study, we test the hypothesis that Daphnia magna increase the variance in maternal investment in response to unpredictable variation in temperature consistent with global change predictions. We detected significant variability across temperature treatments in brood size, neonate size at birth, and time between broods. The estimated variability within-brood size was higher (albeit not statistically significant) in mothers reared in unpredictable temperature conditions. We also detected a cross-generational effect with the temperature history of mothers modulating the phenotypic response of F1’s. Notably, our results diverged from the prediction that increased variability poses a greater risk to organisms than changes in mean temperature. Increased unpredictability in temperature had negligible effects on fitness-correlated traits. Mothers in the unpredictable treatment, survived as long, and produced as many F1’s during lifetime as those produced in the most fecund treatment. Further, increased unpredictability in temperature did not affect the probability of survival of F1’s. Collectively, we provide evidence that daphnia respond effectively to thermal unpredictability. But rather than increasing the variance in maternal investment, daphnia respond to uncertainty by being a jack of all temperatures, master of none. Importantly, our study highlights the essential need to examine changes in variances rather than merely on means, when investigating maternal responses.

Cross‐generational effects refer to nongenetic influences of the parental phenotype or environment on offspring phenotypes. Such effects are commonly observed, but their adaptive significance is largely unresolved. We examined cross‐generational effects of parental temperature on offspring fitness (estimated via a serial‐transfer assay) at different temperatures in a laboratory population of Drosophila melanogaster. Parents were reared at 18°C, 25°C, or 29°C (Tpar) and then their offspring were reared at 18°C, 25°C, or 29°C (Toff) to evaluate several competing hypotheses (including an adaptive one) involving interaction effects of parental and offspring temperature on offspring fitness. The results clearly show that hotter parents are better; in other words, the higher the temperature of the parents, the higher the fitness of their offspring, independent of offspring thermal environment. These data contradict the adaptive cross‐generational hypothesis, which proposes that offspring fitness is maximal when the offspring thermal regime matches the parental one. Flies with hot parents have high fitness seemingly because their own offspring develop relatively quickly, not because they have higher fecundity early in life.

The consequences of early developmental conditions for performance in later life are now subjected to convergent interest from many different biological sub-disciplines. However, striking data, largely from the biomedical literature, show that environmental effects experienced even before conception can be transmissible to subsequent generations. Here, we review the growing evidence from natural systems for these cross-generational effects of early life conditions, showing that they can be generated by diverse environmental stressors, affect offspring in many ways and can be transmitted directly or indirectly by both parental lines for several generations. In doing so, we emphasize why early life might be so sensitive to the transmission of environmentally induced effects across generations. We also summarize recent theoretical advancements within the field of developmental plasticity, and discuss how parents might assemble different ‘internal’ and ‘external’ cues, even from the earliest stages of life, to instruct their investment decisions in offspring. In doing so, we provide a preliminary framework within the context of adaptive plasticity for understanding inter-generational phenomena that arise from early life conditions.

Adaptation to stressful environments is one important factor influencing species invasion success. Tolerance to one stress may be complicated by exposure to other stressors experienced by the preceding generations. We studied whether parental temperature stress affects tolerance to insecticide in the invasive Colorado potato beetle Leptinotarsa decemlineata. Field‐collected pyrethroid‐resistant beetles were reared under either stressful (17°C) or favourable (23°C) insecticide‐free environments for three generations. Then, larvae were exposed to pyrethroid insecticides in common garden conditions (23°C). Beetles were in general tolerant to stress. The parental temperature stress alone affected beetles positively (increased adult weight) but it impaired their tolerance to insecticide exposure. In contrast, offspring from the favourable temperature regime showed compensatory weight gain in response to insecticide exposure. Our study emphasizes the potential of cross‐generational effects modifying species stress tolerance. When resistant pest populations invade benign environments, a re‐application of insecticides may enhance their performance via hormetic effects. In turn, opposite effects may arise if parental generations have been exposed to temperature stress. Thus, the outcome of management practices of invasive pest species is difficult to predict unless we also incorporate knowledge of the evolutionary and recent (preceding generations) stress history of the given populations into pest management.

Background The present nursing workforce comprises four generational of nurses working side–by–side. While such a generation blend adds invaluable diversity to the workforce, it also brings added complexity. The study aimed to describe and summarise work values and attitudes of four nursing generations, namely Baby boomers, Generation X, Y and Z. Method A cross-sectional questionnaire study was adopted. A total of 778 nurses from an acute hospital in Singapore completed the online questionnaire. The Work Value and Attitude scale measuring seven constructs (Work Centrality, Non-compliance, Technology Challenge, Work life balance, leadership, Power, and Recognition) was employed for data collection. Results The Cronbach’s alpha was 0.714 for the overall instrument. Statistically significant differences amongst the four generations of nurses emerged in the Work Value and Attitude scale in the construct of non-compliance (p = 0.007), technology challenge (p = 0.027), work-life balance (p < 0.001), and recognition (p < 0.001). No statistically significant differences were noted for the rest of the constructs. Discussion and conclusion The findings of this study highlight that differences in work values and attitudes exist among nurses of different generations. Generation X are less likely to challenge the conventional norm and supervisors. Generation Y and Z are the most tech-savvy generations and can adapt quickly to new technology. There is also a greater emphasis on work-life balance as the generation gets younger. Generation Y and Z nurses perceived that younger nurses do not get due respect and recognition from their colleagues. Acknowledging the generational differences in work values and attitudes can facilitate nursing management to tailor strategies to improve individual and organisation performance while creating a work environment that enhances intergeneration harmony and teamwork.

Despite increased awareness, maternal cigarette smoking during pregnancy continues to be a common habit causing risk for numerous documented negative health consequences in the exposed children. It has been proposed that epigenetic mechanisms constitute the link between prenatal exposure to maternal cigarette smoking (PEMCS) and the diverse pathologies arising in later life. We here review the current literature, focusing on DNA methylation. Alterations in the global DNA methylation patterns were observed after exposure to maternal smoking during pregnancy in placenta, cord blood and buccal epithelium tissue. Further, a number of specific genes exemplified by CYP1A1, AhRR, FOXP3, TSLP, IGF2, AXL, PTPRO, C11orf52, FRMD4A and BDNF are shown to have altered DNA methylation patterns in at least one of these tissue types due to PEMCS. Investigations showing persistence and indications of trans-generational inheritance of DNA methylation alterations induced by smoking exposure are also described. Further, smoking-induced epigenetic manifestations can be both tissue-dependent and gender-specific which show the importance of addressing the relevant sex, tissue and cell types in the future studies linking specific epigenetic alterations to disease development. Moreover, the effect of paternal cigarette smoking and second-hand smoke exposure is documented and accordingly not to be neglected in future investigations and data evaluations. We also outline possible directions for the future research to address how DNA methylation alterations induced by maternal lifestyle, exemplified by smoking, have direct consequences for fetal development and later in life health and behavior of the child.