Biology subjects

Meunier, J.

Publications and source records attributed to Meunier, J..

8 recordsLinked to original sources

bioRxiv2026

Deltamethrin-induced neurotoxicity: A stage-specific analysis of the European earwig head proteome

Pesticides are ubiquitous in agroecosystems and pose substantial risks to non-target organisms. Traditional ecotoxicological assessments focus on survival, reproduction, or overt behavior, yet these endpoints may fail to detect subtle, molecular-level stress. Here, we investigated the effects of sublethal deltamethrin exposure on the head proteome of field-collected European earwig (Forficula auricularia) females, sampled at two life stages (pre-oviposition and post-family life) to account for physiological context. Our results reveal that deltamethrin induces a robust proteomic response shared across developmental stages, including the regulation of key detoxification enzymes (NADPH- cytochrome P450 reductase, arginine kinase). In parallel, stage-specific responses were observed, involving proteins related to metabolism, stress response, and cellular organization. Strikingly, these molecular perturbations occurred without detectable changes in reproductive traits, highlighting a disconnect between cellular stress and organismal phenotypes. Several uncharacterized proteins were consistently regulated, representing promising targets for future studies on pesticide adaptation and potential detoxification pathways. Overall, these findings suggest that classical phenotypic assays may underestimate sublethal pesticide effects, and that proteomic profiling provides a sensitive framework to uncover underlying molecular responses. By integrating natural variability, realistic exposure, and reproductive physiology, our study emphasizes the need for molecular approaches in environmental risk assessment and offers a new perspective on the subtle, cryptic effects of agrochemicals.

ecology↗

bioRxiv2024

Cadmium ingestion does not disrupt the social transmission of the microbiome in juveniles of a subsocial insect

Symbiotic microbes are essential for host health and fitness. In family-living species, these microbes are often acquired through vertical transmission from parents and horizontal transmission from siblings. However, it is unclear how environmental stressors, such as chemical pollution, influence these contributions to the juvenile microbiome. Here, we tested the independent and interactive effects of social environment and cadmium ingestion - a highly toxic and common heavy metal pollutant - on the microbiome of juvenile European earwigs. We reared 900 juveniles either alone, with siblings or with siblings plus the mother. We exposed them to cadmium-enriched food at 0, 25 or 100mg.L-1, and analysed their microbiome composition and diversity at the end of the family life period. Our results showed that both social environment and cadmium exposure shaped the juvenile microbial community composition (phylogenetic beta-diversity), with no evidence of an interaction between these factors. In contrast, the microbial local richness (alpha-diversity) remained unaffected by either factor or their interaction. Notably, several specific bacterial taxa, including putatively pathogenic (Serratia) and mutualistic (Lactobacillus) symbionts, were more abundant in juveniles reared with family members than in those reared in isolation, reflecting classical patterns observed in social species. Overall, our findings suggest that while both social environment and cadmium shape the microbiome of earwig juveniles, family life neither amplifies nor mitigates the effects of chemical exposure. This highlights the robustness of microbial sharing within families, even under strong environmental stress.

microbiology↗

bioRxiv2024

Microbiome turnover during offspring development varies with maternal care, but not moult, in a hemimetabolous insect

The ecological success of insects often depends on their association with beneficial microbes. However, insect development involves repeated moults, which can have dramatic effects on their microbial communities. Here, we investigated whether and how moulting affects the microbiome of a hemimetabolous insect, and whether maternal care can modulate these effects. We reared European earwig juveniles with or without mothers and used 16S rRNA metabarcoding to analyse the prokaryotic fraction of the core microbiome of eggs, recently and old moulted individuals at four developmental stages and the resulting adults. The 218 samples obtained showed that the microbiome diversity changed non-linearly during development and that these changes were associated with bacterial biomarkers. Surprisingly, these changes did not occur during moulting, but rather between the beginning and end of certain developmental stages. We also found that access to maternal care affected the microbiome of both juveniles and adults, even when the last contact with mothers was two months before adulthood. Overall, these results provide new insights into our understanding of the (in)stability of the prokaryotic microbiome in hemimetabolous insects and its independence from moult. More generally, they question the role of microbiome acquisition through maternal care in maintaining family life in species where this behaviour is facultative.

microbiology↗

bioRxiv2024

Relationship between weapon size and six key behavioural and physiological traits in males of the European earwig

In many animals, male weapons are large and extravagant morphological structures that typically enhance fighting ability and reproductive success. It is generally assumed that growing and carrying large weapons is costly, thus only males in the best condition can afford it. In the European earwig, males carry weapons in the form of forceps-like cerci, which can vary widely in size within populations. While long forceps appear to increase males access to females, it is unknown whether it also correlates with other important male lifen-history traits. This information is important, however, in determining the potential reliability of forceps length as an indicator of male quality and the stability of this signalling system. Here, we tested whether forceps length is associated with six important behavioural and physiological traits in males of the European earwig. We sampled hundreds of males from two populations, selected 60 males with the longest and shortest forceps from each population, and then measured locomotor performance, boldness, aggregation behaviour, survival under harsh conditions, sperm storage, and survival after pathogen exposure. Contrary to our predictions, we detected no main association between forceps length and the traits measured. This lack of association was consistent between the two populations, although there were population-specific levels of boldness, aggregation and survival in harsh conditions (for long-forceps males only). Overall, these results challenge our current understanding of the function and quality signal of forceps length in this species and raise questions about the evolutionary drivers that could explain the maintenance of weapon size diversity within and between populations.

evolutionary biology↗

bioRxiv2021

Temperature shapes oviposition site selection and post-oviposition egg transport in an insect with parental care

AO_SCPLOWBSTRACTC_SCPLOWDepositing eggs in an area with adequate temperature is often crucial for mothers and their offspring, as the eggs are immobile and therefore cannot avoid exposure to sub-optimal temperatures. However, the importance of temperature on oviposition site selection is less clear when mothers can avoid these potential adverse effects by both moving their eggs after oviposition and providing other forms of egg care. In this study, we addressed this question in the European earwig, an insect in which mothers care for the eggs during several months in winter, frequently moving them during this period. We set up 60 females from two random natural populations (as this species often exhibits population-specific life-history traits and behaviours) under controlled thermal gradients, and recorded the temperature at which they built their nests, tested whether they moved their eggs after an experimental temperature change, and measured the effects on egg development and hatching rate. Our results demonstrate that females indeed select oviposition sites according to temperature, and can move their eggs to reach warmer temperatures. We also show that these warmer temperatures are necessary to ensure egg hatching. Although this set of behavioural thermoregulations is present in the two tested populations, we found a population-specific modality of expression. These included the range of temperatures explored before oviposition, temperature selected at oviposition and dynamics of egg transport following a temperature change. Overall, our study sheds light on a new post-oviposition strategy in female insects that overwinter with their eggs for coping with temperature changes. More generally, it also reveals that egg care and/or egg transport do not prevent behavioural thermoregulation via oviposition site selection and highlights the diversity of behaviours that insects can adopt to enhance their tolerance to global climate change.

evolutionary biology↗

bioRxiv2020

Alteration of gut microbiota with rifampicin does not impair maternal care in the European earwig

AO_SCPLOWBSTRACTC_SCPLOWThe microbes residing within the gut of an animal host often increase their own fitness by modifying their hosts physiological, reproductive, and behavioural functions. Whereas recent studies suggest that they may also shape host sociality and therefore have critical effects on animal social evolution, the impact of the gut microbiota on maternal care remains unexplored. This is surprising, as this behaviour is widespread among animals, often determines the fitness of both juveniles and parents, and is essential in the evolution of complex animal societies. Here, we tested whether life-long alterations of the gut microbiota with rifampicin - a broad-spectrum antibiotic - impair pre- and post-hatching maternal care in the European earwig. Our results first confirm that rifampicin altered the mothers gut microbial communities and indicate that the composition of the gut microbiota differs before and after egg care. Contrary to our predictions, however, the rifampicin-induced alterations of the gut microbiota did not modify pre- or post-hatching care. Independent of maternal care, rifampicin increased the females feces production and resulted in lighter eggs and juveniles. By contrast, rifampicin altered none of the other 21 physiological, reproductive and longevity traits measured over the 300 days of a females lifetime. Overall, these findings reveal that altering the gut microbiota with a large spectrum antibiotic such as rifampicin does not necessarily affect host sociality. They also emphasize that not all animals have evolved a co-dependence with their microbiota and call for caution when generalizing the central role of gut microbes in host biology.

evolutionary biology↗

bioRxiv2019

The successful invasion of the European earwig across North America reflects adaptations to thermal regimes but not mean temperatures

Understanding the mechanisms by which an introduced species adapt to newly encountered habitats is a major question in ecology. A key method to address this question is to collect data on introduced species that have successfully invaded a broad diversity of novel environments, and analyze how their life-history traits changed with these new constraints. Here, we present and analyze such a unique data set in the European earwig Forficula auricularia L, an insect that invaded North America during the last century. We conducted a common garden experiment, in which we measured 13 life-history traits in 4158 individuals from 19 populations across North America. Our results demonstrate that the successful invasion of this species came with changes in 10 of their life-history traits in response to thermal regimes (winter-summer and autumn-spring temperatures), but with no change in response to the overall mean temperatures of the invaded locations. Importantly, we show that some of these changes are by-products of novel thermal regimes, whereas others reflect adaptive strategies of females to these constraints. Overall, our findings reveal the importance of thermal regimes over mean temperatures in climate adaptation, and emphasize that studying adaptive capabilities is crucial to predict the limits of biological invasions.

evolutionary biology↗

bioRxiv2017

The evolution of social life in family groups

Family life forms an integral part of the life-history of species across the animal kingdom, and plays a crucial role in the evolution of animal sociality. Our current understanding of family life, however, is almost exclusively based on studies that (i) focus on parental care and associated family interactions (such as those arising from sibling rivalry and parent-offspring conflict), and (ii) investigate these phenomena in the advanced family systems of mammals, birds, and eusocial insects. Here, we argue that these historical biases have fostered the neglect of key processes shaping social life in ancestral family systems, and thus profoundly hamper our understanding of the (early) evolution of family life. Based on a comprehensive survey of the literature, we first illustrate that the strong focus on parental care in advanced social systems has deflected scrutiny of other important social processes such as sibling cooperation, parent-offspring competition and offspring assistance. We then show that accounting for these neglected processes - and their changing role in the course of evolution - could profoundly change our understanding of the evolutionary origin and subsequent consolidation of family life. Finally, we outline how this diachronic perspective on the evolution of family living could provide novel insights into general processes driving social evolution. Overall, we infer that the explicit consideration of thus far neglected facets of family life, together with their study across the whole diversity of family systems, are crucial to advance our understanding of the processes that shape the evolution of social life.

evolutionary biology↗