Biology subjects

Immler, S.

Publications and source records attributed to Immler, S..

At least 19 recordsLinked to original sources

bioRxiv2026

Dietary fibre responses emerge through host-dietary regime interplay: Apple pectin modulates immune reactivity in adult zebrafish

Dietary fibres are rarely consumed independently. Instead, they form part of an overall diet that includes dietary fibres from different sources, in varying amounts and consumed under different feeding patterns. Here, we tested how dietary regimes containing apple pectin, oat {beta}-glucan, or cellulose shaped the host. We analysed gut microbiome composition by 16S rRNA sequencing, measured brain and intestinal SCFA profiles by targeted metabolomics, and assessed immunomodulation by measuring gene expression systemically in the blood and locally in the spleen, as well as intestinal enzyme activity. The dietary intervention was conducted for 12 weeks on adult female and male zebrafish (Danio rerio). Our results show that the gut microbial composition can be relatively stable across different dietary fibre exposure patterns yet still vary significantly between the sexes. Additionally, the effect of sex on the gut microbiome may become more evident when dietary fibres are administered at high dosages, but intermittently. Dietary fibre regimes can alter intestinal short-chain fatty acid profiles more readily than brain profiles, which show a stronger sexually dimorphic response. Interestingly, apple pectin modulated the zebrafish immune response through interactions dependent on the overall regime, tissue, sex, and host immune status. Notably, tissue il1b gene expression differed depending on how apple pectin was administered and the host's physiological state. Collectively, our study emphasises the highly context-specific effects of dietary fibres, shaped by the dynamic interplay between the overall dietary regime and intertwined host factors.

systems biology↗

bioRxiv2026

Axillary gland gene expression and potency reveal the nature of mimetic relationships in Corydoradinae catfishes

The evolution of Mullerian or Batesian mimicry depends on the relative unpalatability of participating taxa, yet the mechanistic basis of such unpalatability remains poorly explored in many systems. Unpalatability in the Corydoradinae catfishes, known for their striking mimetic diversity, is underpinned by sharp, lockable spines, armoured bodies and the production of venoms/toxins. Here, we assess the contribution of the axillary gland, a structure at the base of the pectoral spine, to toxicity in two Corydoradinae genera, Corydoras and Hoplisoma. Using a brine shrimp cytotoxicity assay, we demonstrate that axillary gland extracts are significantly more toxic than muscle extracts in both genera, but toxicity does not differ significantly between genera. Transcriptomic analyses identified 539 candidate toxin genes upregulated in axillary gland tissue, relative to scute tissue, containing signal peptides and had predicted toxin functions based on amino acid sequences. Notably, candidate genes include domains typical of piscine venoms, such as lectins and peptidase S1. Although significant differences in gene expression were detected between genera in candidate toxins, log-fold changes were small, and predicted toxin potency was not significantly different between genera. Together, our findings indicate that axillary gland toxins are likely to contribute to unpalatability in Corydoradinae catfishes and provide support for Mullerian mimicry in this system.

evolutionary biology↗

bioRxiv2025

The germline-restricted chromosome orchestrates germ cell development in passerine birds

While the definition of germ cell fate has been extensively studied in model organisms, evolutionary innovations and mechanistic novelties may remain hidden in understudied systems. The phenomenon of programmed DNA elimination allows germ cells to acquire germline-restricted genes, offering a novel paradigm of germ cell specificity. In passerine birds, the germline-restricted chromosome (GRC) is eliminated from somatic cells in early embryogenesis, yet the role and consequences of its maintenance in the germ cells remain poorly understood. Here, using the zebra finch Taeniopygia guttata as a model, we combined RNA-seq and Spatial Transcriptomics to construct a high-resolution spatiotemporal expression map to understand the role of the GRC across germ cell development. We found a GRC-linked integrin-BMP signaling in maturing oocytes and tfebGRC upregulation at blastoderm embryos, suggesting the involvement of the GRC in oocyte maturation and germ cell determination. We also identified developmental specialization of GRC-linked gene expression relative to their paralogs on the autosomes and sex chromosomes, revealing a gene repertoire which promotes germline stemness and germline/soma distinction. Together, the passerine GRC constitutes a unique system that manifests germ cell complexity, whilst allowing pinpointing the effects on gene expression that may elucidate vertebrate germ cell fate.

developmental biology↗

bioRxiv2025

Lifespan-extending downregulation of insulin signalling reduces germline mutation load

Reduced insulin/IGF-1 signalling (IIS) robustly extends lifespan and enhances somatic stress resistance across taxa, yet its consequences for germline genome integrity remain unclear. Here we combine multigenerational mutation accumulation with whole-genome sequencing in C. elegans to test whether adulthood-only IIS downregulation can simultaneously promote somatic maintenance and limit germline mutational burden. We reduced IIS by adult-onset daf-2 RNAi in wild-type and heritable RNAi-deficient (hrde-1) backgrounds, allowing either spontaneous or UV-induced germline mutations to accumulate over multiple generations. In wild-type animals, reduced IIS lowered germline single-nucleotide mutation rates by up to [~]50% and prevented the UV-induced elevation in mutation rate, without detectable costs to fecundity or lineage persistence. By contrast, in hrde-1 mutants the same intervention increased both point mutations and transposable-element-driven insertions under UV exposure, accelerating lineage extinction. Thus, the genome-protective effect of reduced IIS critically requires the germline nuclear Argonaute HRDE-1, which mediates small-RNA-guided epigenetic silencing. Functional annotation of germline variants revealed enrichment in pathways linked to development, cellular maintenance and conserved longevity regulators, including IIS and mTOR, and identified high-impact mutations in genes with human orthologs implicated in neurodegeneration and cancer. Our findings show that IIS can coordinate somatic and germline maintenance in concert, rather than in competition, through an HRDE-1-dependent epigenetic pathway. This work positions nutrient-sensing IIS as a central regulator of germline genome stability and suggests that IIS downregulation can reduce germline mutation load while extending lifespan, with broad implications for biogerontology and evolutionary biology.

evolutionary biology↗

bioRxiv2025

Sex-specific responses of small RNAs and transposable elements to thermal stress in zebrafish germ cells

Climate change-induced thermal stress threatens germline genome stability and triggers a molecular response of small RNA pathways involved transposable element (TE) regulation. The difference in mitotic and meiotic activity in male and female germ cells suggests that this response differs, but the mechanisms are elusive. Here we integrate whole-genome and transcriptome sequencing, and small RNA profiling to examine how mild thermal elevation affects TE regulation in male and female zebrafish gonads. We find that ovaries maintain genomic integrity through coordinated upregulation of piRNAs and miRNAs linked to heat-shock responses, limiting TE mobilisation. In contrast, testes exhibit reduced small RNA abundance, widespread TE activation, and increased de novo insertions, reflecting compromised genome defence. Multi-omic network analyses reveal a piRNA-TE-miRNA regulatory network preserved in ovaries but disrupted in testes under thermal stress. These findings reveal a sex-specific divergence in genome defence mechanisms, with implications for fertility and heritable genome stability in changing environments.

evolutionary biology↗

bioRxiv2025

Evolutionary trade-offs between intergenerational and transgenerational fitness effects

Intergenerational and transgenerational fitness effects can shape evolutionary processes. Theoretically, however, intergenerational and transgenerational effects can trade-off with each other with profound consequences for evolutionary processes. Here we show that beneficial intergenerational effects that increase offspring fitness can result in detrimental transgenerational effects that decrease great-grand offspring fitness. We combined theoretical modelling and experimental approaches to investigate multigenerational fitness trade-offs induced by larval starvation in Caenorhabditis elegans. We demonstrate that larval starvation triggers a cascading effect: starved individuals suffered marked fitness losses, their direct offspring enjoyed fitness gains in both starvation and ad libitum environments, but great-grand-offspring paid fitness costs. Demographic simulation models revealed that genotypes exploiting this short-term intergenerational advantage outcompete rival genotypes despite the deferred transgenerational debt. Our findings demonstrate that adaptive intergenerational gains can be intrinsically linked to maladaptive transgenerational outcomes, challenging the assumption that transgenerational effects are inherently beneficial and highlighting the role of multigenerational trade-offs in evolution.

evolutionary biology↗

bioRxiv2025

Mutation accumulation underpins evolution of lifespan extension by dietary restriction

Dietary restriction (DR) extends lifespan in animals and plants, but its evolutionary causes are elusive. Adaptive hypotheses posit that DR extends lifespan because organisms reallocate resources from reproduction to survival ( disposable soma) or recycle cellular waste to maximize either their immediate reproduction ( nutrient recycling) or survival ( clean cupboards). We developed an experimental paradigm that tricks Caenorhabditis elegans nematodes into increasing their reproductive effort under DR via food odour, thus allowing us to test these hypotheses. We found that experimentally increased reproduction under DR does not affect immediate or long-term survival benefits compared to DR animals that did not reproduce, thus refuting all three adaptive hypotheses. Our data suggest that a large part of suppressed fertility under DR is a result of organisms refraining from producing offspring in a poor environment. We developed a model based on Hamiltonian forces of selection to show that lifespan extension under DR evolves because DR suppresses fertility, directly increasing selection against mortality in DR environment. Our analytical approach suggests that DR-driven lifespan extension can evolve under a broader range of conditions not previously anticipated, such as a relaxed need for physiological or genetic trade-offs. Instead, we show how reduced survival on plentiful food can evolve via mutation accumulation.

evolutionary biology↗

bioRxiv2024

Diverging transposon activity among polar bear sub-populations inhabiting different climate zones

A new subpopulation of polar bears (Ursus maritimus) was recently discovered in the South-East of Greenland. This isolated colony inhabits a warmer climate zone, akin to the predicted future environments of polar bears with vastly reduced sea ice habitats, rendering this population of bears particularly important. Over two-thirds of polar bears will be extinct by 2050 with total extinction predicted by the end of this century, therefore understanding possible mechanisms of adaptation via genomic analyses and preservation are critical. Transposable elements (TEs) are parasitic mobile elements that may play a role in an adaptive response to environmental challenges. We analysed transcriptome data from polar bear sub-populations in cooler North- East (NEG) and warmer South-East Greenland (SEG) to compare TE activity between the two populations and its correlation with temperature and associated changes in gene expression. We identified activity hotspots in the genome of regions with significantly differentially expressed TEs. LINE family TEs were the most abundant, and most differentially expressed and divergent in the SEG population compared to reference TEs. We report a significant shift in TE activity and age, with younger more abundant TEs in the SEG populations. Differentially expressed genes in SEG populations were linked to Foxo signalling, ageing and metabolic pathways. Our results provide insights into how a genomic response at the TE level may allow the SEG subpopulations to adapt and survive to climate change and provides a useful resource for conservation in polar bears.

evolutionary biology↗

bioRxiv2024

Environmentally induced variation in sperm sRNAs is linked to gene expression and transposable elements in zebrafish offspring

Environmental factors affect not only paternal condition but may translate into the following generations where sperm-mediated small RNAs (sRNAs) can contribute to the transmission of paternal effects. SRNAs play a key role in the male germ line in genome maintenance and repair, and particularly in response to environmental stress and the resulting increase in transposable element (TE) activity. Here, we investigated how the social environment (high competition, low competition) of male zebrafish Danio rerio affects small RNAs in sperm and how these are linked to gene expression and TE activity in their offspring. In a first experiment, we collected sperm samples after exposing males to each social environment for two weeks to test for differentially expressed sperm micro-(miRNA) and piwi-interacting RNAs (piRNA). In a separate experiment, we performed in vitro fertilisations after one two-week period using a split-clutch design to control for maternal effects and collected embryos at 24 hours to test for differentially expressed genes and transposable elements. We developed new computational prediction tools to link sperm sRNAs with differentially expressed TEs and genes in the embryos. Our results support the idea that the molecular stress response in the male germ line has significant down-stream effects on the molecular pathways, and we provide a direct link between sRNAs, TEs and gene expression. Author summaryThe discovery that sperm transmit more than just the fathers genome to the next generation is relatively recent and the potential implications are far reaching. What we do not know is whether these non-genetic components contained in sperm play a role in adaptation to changing environments or whether they are simply a result of the fathers stress response that also affects the germ cells. Environmentally induced stress is known to trigger a response to maintain and repair the germ cells to ensure the production of high quality sperm and key factors in this response are small RNAS. Small RNAs are guardians of the germ line and protect the germline genome against the activity of selfish genetic elements. We investigated how the social environment in male zebrafish affects the expression level of small RNAs in sperm and how these changes in small RNAs are linked to changes in the gene epxression and the activity of selfish genetic elements in the offspring. We developed specialised bioinformatic pipelines to provide a clear link between the response in the fathers germline to changes in the environment and gene expresssion in their offspring.

evolutionary biology↗

bioRxiv2024

Within-ejaculate haploid selection reduces disease biomarkers in human sperm

The germline is widely regarded as a checkpoint against the inheritance of damaged genomes, yet the mechanisms that could enact such filtering remain poorly resolved. Of the millions of sperm in a human ejaculate, only one fertilises the egg, creating a strong opportunity for selection among gametes. Combining within-ejaculate selection on sperm quality with whole-genome sequencing and proteomics in healthy donors, we find that this selection is biased against molecular signatures of age-related disease. The most reproducibly diverging genes are tumour suppressors, and genes diverging under sperm longevity-based selection are enriched for senescence-associated genes involved in genome maintenance and oxidative stress response. High-quality sperm are further depleted of inflammation- and cancer-associated proteins. This genomic signature is conserved in zebrafish, in which longer-lived sperm sire longer-lived offspring. We propose that within-ejaculate selection acts as a pre-fertilisation filter against age-related disease alleles, with implications for offspring lifespan and healthspan.

molecular biology↗

bioRxiv2024

Gum Arabic (Acacia senegal) enhances reproduction and modulates the microbiota-gut-brain axis of zebrafish in a sex-specific and dosage-dependent manner

Dietary fibres (DFs) constitute a wide range of heterogeneous compounds that resist digestion and have beneficial effects on general health. Gum Arabic (GA) is a tree exudate consisting of 90% arabinogalactan, a polymer of arabinose and galactose sugars with prebiotic properties. As a dietary fibre, GA improves renal function, metabolism, and immune response in humans and animals. However, the underlying mechanisms leading to these health benefits are poorly understood. We supplemented female and male zebrafish (Danio rerio) with two concentrations of GA (6% and 60%) for two weeks. We assessed the effects of GA supplementation on the gut microbiome composition, intestinal and brain metabolic profiles, reproductive fitness, and brain gene expression. We found that GA supplementation resulted in changes to the gut microbiome with a relative increase in Fusobacteria and a relative decrease in Proteobacteria where the beneficial genus Cetobacterium was significantly more abundant after supplementation. GA supplementation increased acetate levels, particularly in the brain, causing a decreased expression of cart1 in the brain of female zebrafish. While GA supplementation increased overall activity in male and female fish, reproductive fitness was negatively affected by GA supplementation in females. Our results suggest that while GA supplementation may have positive effects on metabolic rate and overall activity, it may come at a trade-off with reproductive fitness. Significance StatementDietary fibres, found in plant-based food sources, can improve health. They include natural gums like gum Arabic, a highly sought-after food additive used as a homogeniser. Despite our better understanding of nutrition, a fibre gap is still prevalent in the Western world with efforts being made to incorporate new sources to close this gap and boost well-being. Here, we showed that when gum Arabic was supplemented into the zebrafish diet, it had a beneficial modulatory effect on the microbiota-gut-brain axis and reproductive fitness. Our findings support the benefits of dietary fibres but also link their impact to sexual dimorphism and dosage. This has implications for developing nutrition guidelines for both animals and humans.

systems biology↗

bioRxiv2024

FishPi: a bioinformatic prediction tool to link piRNA and transposable elements in zebrafish

BackgroundPiwi-interacting RNAs (piRNA)s are non-coding small RNAs that post-transcriptionally affect gene expression and regulation. Through complementary seed region binding with transposable elements (TEs), piRNAs protect the genome from transposition. A tool to link piRNAs with complementary TE targets will improve our understanding of the role of piRNAs in genome maintenance and gene regulation. Existing tools such as TEsmall can process sRNA-seq datasets to produce differentially expressed piRNAs, and piRScan developed for nematodes can link piRNAs and TEs but it requires knowledge about the target region of interest and works backwards. ResultsWe have therefore developed FishPi to predict the pairings between piRNA and TEs for available genomes from zebrafish, medaka and tilapia, with full user customisation of parameters including orientation of piRNA, mismatches in the piRNA seed binding to TE and scored output lists of piRNA-TE matches. FishPi works with individual piRNAs or a list of piRNA sequences in fasta format. The software focuses on the piRNA-TE seed region and analyses reference TEs for piRNA complementarity. TE type is examined, counted and stored to a dictionary, with genomic loci recorded. Any updates to piRNA-TE binding rules can easily be incorporated by changing the seed-region options in the graphic user-interface. FishPi provides a graphic interface using tkinter for the user to input piRNA sequences to generate comprehensive reports on piRNA-TE interactions. FishPi can easily be adapted to genomes from other species and taxa opening the interpretation of piRNA functionality to a wide community. ConclusionsUsers will gain insight into genome mobility and FishPi will help further our understanding of the biological role of piRNAs and their interaction with TEs in a similar way that public databases have improved the access to and the understanding of the role of small RNAs.

evolutionary biology↗

bioRxiv2023

Paternal starvation affects metabolic gene expression during zebrafish offspring development and life-long fitness

Dietary restriction is a putative key to a healthier and longer life, but these benefits may come at a trade-off with reproductive fitness and may affect the following generation(s). The potential inter- and transgenerational effects of starvation are particularly poorly understood in vertebrates when they originate from the paternal line. We utilised the externally fertilising zebrafish amenable to a split-egg clutch design to explore the male-specific effects of starvation on fertility and fitness of offspring independently of maternal contribution. Eighteen days of fasting resulted in reduced fertility in exposed males. While average offspring survival was not affected, we detected higher larval growth in offspring from starved males and increased malformation rates at 24 hours post fertilisation in the F2 embryos produced by the offspring of the starved males. The transcriptome analysis of embryos from starved and fed fathers revealed robust and reproducible induction of muscle composition genes and a contrasting repressive effect on lipid metabolism and lysosome genes. A large proportion of these genes showed enrichment in the yolk syncytial layer suggesting gene regulatory responses associated with metabolism of nutrients through paternal impact on extra embryonic tissues which are loaded with maternally deposited factors. We compared the embryo transcriptome to adult transcriptome datasets and demonstrated comparable repressive effects on metabolism-associated genes. These similarities suggest a physiologically relevant, directed and potentially adaptive response transmitted by the father, independently from the offsprings nutritional state, which was defined by the mother.

developmental biology↗

bioRxiv2023

Gametic selection and mating systems show mutually dependent evolution

Competition among pollen or sperm (gametic selection) can cause evolution. Mating systems shape the intensity of gametic selection by determining the competitors involved, which can in turn cause mating system evolution. We model the bidirectional relationship between gametic selection and mating systems, focussing on variation in female mating frequency (monandry-polyandry) and self-fertilisation (selfing-outcrossing). First, we find that mating systems affect evolutionary responses to gametic selection, with more effective gametic selection when fertilisation success depends on haploid genotypes, rather than the diploid genotype of the father. Monandry and selfing both reduce the efficacy of gametic selection despite creating intense selection among pollen/sperm from heterozygous males with haploid expression. This effect means selfing can increase mutation load, in contrast to classic predictions where selfing purges deleterious mutations. Second, we show that mating systems can evolve via their effect on gametic selection, with polyandry evolving because it removes deleterious alleles more efficiently and increases offspring fitness. Our population genetic models reveal that this good sperm effect could plausibly give a selective advantage for polyandry over monandry of only around 1%. Selection for polyandry is lessened further if some loci experience balancing selection and is likely to be overwhelmed by any direct fitness effects of mating systems. Similarly, the indirect benefits from manipulating gametic selection have a weak influence on the evolution of selfing, which is dominated by automatic selection and inbreeding depression in our model. Nevertheless, gametic selection can be potentially decisive for selfing evolution because it significantly reduces inbreeding depression, which favours selfing. One test of the predicted interactions between gametic selection and mating system evolution would be to compare evolutionary rates in genes with different expression patterns across different mating systems.

evolutionary biology↗

bioRxiv2022

Fasting increases investment in soma upon refeeding at the cost of gamete quality in zebrafish

Fasting increases lifespan in invertebrates, improves biomarkers of health in vertebrates, and is increasingly proposed as a promising route to improve human health. Nevertheless, little is known about how fasted animals use resources upon refeeding, and how such decisions affect putative trade-offs between somatic growth and repair, reproduction, and gamete quality. Such fasting-induced trade-offs are based on strong theoretical foundations and have been recently discovered in invertebrates, but the data on vertebrates is lacking. Here we report that fasted female zebrafish, Danio rerio, increase investment in soma upon refeeding but it comes at a cost of egg quality. Specifically, an increase in fin re-growth was accompanied by a reduction in 24-hours post-fertilization offspring survival. Refed males showed a reduction in sperm velocity and impaired 24-hour post-fertilisation offspring survival. These findings underscore the necessity of considering the impact on eggs and sperm when assessing evolutionary and biomedical implications of lifespan-extending treatments in females and males and call for careful evaluation of the effects of fasting (both during and post) on fertilisation.

evolutionary biology↗

bioRxiv2022

Frequency-dependent viscosity of salmon ovarian fluid has biophysical implications for sperm-egg interactions

Gamete-level sexual selection of externally fertilising species is usually achieved by modifying sperm behaviour with mechanisms thought to alter the chemical environment in which gametes perform. In fish this can be accomplished through the ovarian fluid, a substance released with the eggs at spawning. While its biochemical effects in relation to sperm energetics have been investigated, the influence of the physical environment in which sperm compete remains poorly explored. Our objective was therefore to gain insights on the physical structure of this fluid and potential impacts on reproduction. Using soft-matter physics approaches of steady-state and oscillatory viscosity measurements, we subjected salmon ovarian fluids to variable shear stresses and frequencies resembling those exerted by sperm swimming through the fluid near eggs. We show that this fluid, which in its relaxed state is a gel-like substance, displays a non-Newtonian viscoelastic and shear-thinning profile, where the viscosity decreases with increasing shear rates. We concurrently find that this fluid obeys the Cox-Merz rule below 7.6 Hz and infringes it above, thus indicating a shear-thickening phase where viscosity increases provided it is probed gently enough. This suggests the presence of a unique frequency-dependant structural network with relevant implications on sperm energetics and fertilisation dynamics.

evolutionary biology↗

bioRxiv2020

Experimental evolution of adaptive divergence under varying degrees of gene flow

Adaptive divergence is the key evolutionary process generating biodiversity by means of natural selection. Yet, the conditions under which it can arise in the presence of gene flow remain contentious. To address this question, we subjected 132 sexually reproducing fission yeast populations sourced from two independent genetic backgrounds to disruptive ecological selection and manipulated the level of migration between environments. Contrary to theoretical expectations, adaptive divergence was most pronounced when migration was either absent ( allopatry) or maximal ( sympatry), but was much reduced at intermediate rates ( parapatry, local mating). This effect was apparent across central life history components (survival, asexual growth, and mating), but differed in magnitude between ancestral genetic backgrounds. The evolution of some fitness components was constrained by pervasive negative correlations (trade-off between asexual growth and mating), while others changed direction under the influence of migration (e.g. survival and mating). In allopatry, adaptive divergence was mainly conferred by standing genetic variation and resulted in ecological specialization. In sympatry, divergence was mainly mediated by novel mutations enriched in a subset of genes and was characterized by the repeated emergence of two strategies: an ecological generalist and an asexual growth specialist. Multiple loci showed consistent evidence for antagonistic pleiotropy across migration treatments and provide a conceptual link between adaptation and divergence. This evolve-and-resequence experiment demonstrates that rapid ecological differentiation can arise even under high rates of gene flow. It further highlights that adaptive trajectories are governed by complex interactions of gene flow, ancestral variation and genetic correlations.

evolutionary biology↗

bioRxiv2020

Reduced insulin signalling in adulthood protects soma and germline under mutation accumulation

Adulthood-only downregulation of insulin/IGF-1 signalling (IIS), an evolutionarily conserved pathway regulating resource allocation between somatic maintenance and reproduction, increases lifespan without fecundity cost in the nematode, Caenorhabditis elegans. However, long-term multigenerational effects of reduced IIS remain unexplored and are proposed to carry costs for offspring quality. To test this hypothesis, we ran a mutation accumulation (MA) experiment and downregulated IIS in half of the 400 MA lines by silencing daf-2 gene expression using RNA interference (RNAi) across 40 generations. Contrary to the prediction, adulthood-only daf-2 RNAi reduced extinction of MA lines both under UV-induced and spontaneous mutation accumulation. Fitness of the surviving UV-induced MA lines was higher under daf-2 RNAi. Reduced IIS increased intergenerational F1 offspring fitness under UV stress but had no quantifiable transgenerational effects. Functional hrde-1 was required for the benefits of multigenerational daf-2 RNAi. Overall, we found net benefit to fitness from multigenerational reduction of IIS and the benefits became more apparent under stress. Because reduced daf-2 expression during development carries fitness costs, we suggest that our findings are best explained by the developmental theory of ageing, which maintains that the decline in the force of selection with age results in poorly regulated gene expression in adulthood.

evolutionary biology↗