Transgenerational effects of pest management strategy on fluctuating asymmetry in the European earwig Forficula auricularia: Being the progeny of a mother who lived in conventional orchards makes you more asymmetric than having a mother who lived in insecticide free orchards.

Transgenerational effects of pest management strategy on fluctuating asymmetry in the European earwig Forficula auricularia: Being the progeny of a mother who lived in conventional orchards makes you more asymmetric than having a mother who lived in insecticide free orchards. | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Research Article Transgenerational effects of pest management strategy on fluctuating asymmetry in the European earwig Forficula auricularia: Being the progeny of a mother who lived in conventional orchards makes you more asymmetric than having a mother who lived in insecticide free orchards. Joffrey Moiroux, Doufoungognon C. Koné, Adrien Le Navenant, Séverine Suchail, and 1 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-1395448/v1 This work is licensed under a CC BY 4.0 License Status: Posted Version 1 posted You are reading this latest preprint version Abstract Fluctuating asymmetry (FA), defined as the random non-directional deviation from perfect bilateral symmetry, is considered to reflect developmental instability in bilaterally symmetrical organisms. It has been commonly used as a reliable biomarker of environmental stresses in natural populations. In agroecosystems, FA may arise through transgenerational influence of insecticides. We measured fluctuating asymmetry on unexposed progeny of Forficula auricularia mothers sampled in orchards that used no to frequent insecticides’ applications. Seven morphometric traits were measured on both right and left side and fluctuating asymmetry was calculated. Among these seven traits, four were more asymmetric when the progeny was born from a mother who lived in conventional orchards that used insecticides frequently compared to a mother who lived in insecticide free orchards. Males were more asymmetric than females for all traits but pest management strategy influenced FA in a similar way for both sexes. Measuring FA on unexposed daughters and sons of individuals originating from natural ecosystems may thus be a reliable easy-to-use tool to monitor mid-term effects of insecticides in the environment. Biomarker Developmental stability Morphometry Pesticides Terrestrial arthropods Figures Figure 1 Figure 2 Introduction Chemical insecticides are a prominent strategy to manage insect pests despite their well-documented negative impact on ecosystems (Pisa et al. 2021 ; Stehle & Schulz 2015; Schulz et al. 2021 ). They are indeed known to commonly induce lethal and sublethal effects on non-target species, including beneficial organisms for agriculture such as pollinators or natural enemies (Desneux et al. 2007 ; Müller 2018 ). Their toxicity may last over time, sometimes several years after their use (Chiaia-Hernandez et al. 2017 ; Wu et al. 2020 ), and their long-term influence may extend over generations. Several studies thus reported transgenerational effects of parents’ exposure to insecticides on unexposed progeny (Costa et al., 2014 ; Le Navenant et al. 2021 ), such as longer development and reduced hatching success (Guo et al. 2013 ) or increased tolerance to insecticides (Le Navenant et al. 2019 ). These transgenerational effects may arise from several processes, including a reduced ability of the parents to invest energy in their offspring (Szabo et al. 2019), heritable epigenetic modifications (Brevik et al. 2018 ), an accumulation of insecticides in ovaries (Müller et al. 2017 ) or changes in ovaries’ composition (Ge et al. 2009 , Habes et al. 2013 ). These two last mechanisms may notably affect developmental stability of offspring, causing indirect effects of insecticides on the next generation. It has been proposed that developmental instability may be estimated by measuring fluctuating asymmetry (FA) (Palmer & Strobeck, 1986 ), defined as the random non-directional deviation from perfect bilateral symmetry in normally bilaterally symmetrical organisms (Clarke 1993 ; Lens et al. 2002 ). Many studies reported for example that FA was more pronounced when aquatic or terrestrial insects faced an environmental stress during their development, including insecticide exposure (Chang et al. 2007 ; Mpho et al. 2001 ), reduced nutrition (Hunt & Simmons 1997 ), or increased parasite load (Bonn et al. 1996 ). FA has thus been used as a reliable easy-to-use monitoring biomarker of environmental stresses in natural populations (Beasley et al. 2013 ; Benitez et al. 2020). Although measuring fluctuating asymmetry on unexposed progeny of individuals originating from natural populations may be an interesting procedure to monitor mid-term effects of insecticides, it has never been tested to our knowledge. In this paper, we investigated the transgenerational influence of pest management strategy on fluctuating asymmetry of the European earwig Forficula auricularia L. 1758 (Dermaptera: Forficulidae). This species is considered beneficial in apple and pear orchards since it predates several pest species such as aphids, leaf rollers and psyllids ( Dib et al. 2011 ). Several studies reported that insecticides directly affect their morphology (Suchail et al. 2018 ), biochemical pathways (Malagnoux et al. 2014 ) or behavior (Sauphanor et al. 1993 ; Malagnoux et al. 2015 ). Transgenerational effects have also been observed. Unexposed F1 females whose parents were previously sampled in conventional orchards indeed exhibited a significantly smaller femur than those whose parents were sampled in integrated or organic orchards (Le Navenant et al. 2021 ). We measured FA on unexposed progeny of earwig mothers sampled in orchards with no to frequent insecticides’ applications to test for the relevance of this procedure as a biomarker of long-term impact of pest management strategy on natural populations. We hypothesized that FA would be more pronounced for progeny born from mothers sampled in orchards using frequently insecticides than for progeny born from mothers sampled in orchards using no to few treatments. Material And Methods 1.1 Sampling and rearing Forficula auricularia adults were sampled in October 2015 using cardboard traps placed on tree branches in nine orchards located in the vicinity of Avignon, south-eastern France. These 6 apple and 3 pear orchards were classified in three different categories depending on their legal classification (Organic) and respective pesticide management strategy (Integrated Pest Management (IPM) vs Conventional). The three conventional orchards used 6 to 9 chemical insecticide treatments while the three IPM orchards used one to two insecticide treatments in 2015. The three organic orchards did not use any insecticide, including those approved in organic farming such as spinosyns. Sampled females were placed separately in Petri Dishes in an open shelter, under natural photoperiod and climate. Food and water were provided ad libitum . Eggs were laid starting from December and progeny were kept with their mother until they reached the third instar. L3 earwigs were then placed altogether until their reached adulthood. Fifteen to twenty-five individuals per orchard and per sex were then removed randomly and frozen for later measurement. Since insecticides applications stopped mid-August in the sampled orchards and mating generally occurs in late august and early September in south-eastern France for this species, individuals used for measurements were never directly exposed to insecticides during their development, although they may have been in maternal tissues where traces of products may have remained. 1.2 Morphometric measurements After being slightly thawed at room temperature, each earwig was positioned carefully under a binocular (Nikon SMZ 745T) linked to a camera (TOUPCAM U3CMOS) and seven morphometric variables were measured twice on both right and left side using the software ToupView. We measured (1) the first antennal segment length, (2) forceps length and (3) width, (4) elytra length, and on hind legs, the femur (5) length and (6) width and (7) tibia length, as described in Figure 1. 1.3 Statistical analysis. Repeated measures ANOVA confirmed significantly greater variance between individuals than between repeated measures. The mean value of the two measures performed per side was thus used for statistical analyses. Signed fluctuating asymmetry was calculated as the value of left minus right measures. These values were normally distributed for all morphometric parameters, we therefore considered that significant differences from zero would indicate fluctuating asymmetry. Unsigned fluctuating asymmetry, i.e. the absolute values of left minus right measures (Polak & Starmer 2001; Stige et al. 2006), was used for statistical analyses. ANOVA were performed to test for differences in the mean value of each side and on unsigned fluctuating asymmetry of the seven morphometric variables with sex and pest management strategy as explanatory factors. ANCOVA were also performed with the mean of the trait as a covariate but it did not significantly influence the effect of pest management strategy on asymmetry for any trait. Results We did not observe any influence of the sex on the mean value of the morphometric traits except for longer (left: F = 28.71, p < 0.005; right: F = 55.87, p < 0.005) and wider (left: F = 155.14, p < 0.005; right: F = 166.97, p < 0.005) forceps in males. The interaction between sex and pest management strategy did not influence any morphometric trait but pest management strategy alone did for femur length (left: F = 34.02, p < 0.005; right: F = 32.75, p < 0.005), forceps length (left: F = 13.01, p < 0.005; right: F = 25.20, p < 0.005) and width (left: F = 20.62, p < 0.005; right: F = 11.89, p < 0.005), and elytra length (left: F = 18.31, p < 0.005; right: F = 25.83, p < 0.005). Progeny of earwigs sampled in conventional orchards were commonly smaller for these four traits than those whose parents were sampled in organic orchards. Sex and pest management strategy both significantly influenced unsigned asymmetry of several morphometric traits while the interaction between these two factors did not, except for tibia length (F = 3.24, p = 0.03). Asymmetry was more pronounced in males than females for every trait, i.e. the first antennal segment (F = 20.42, p < 0.005), tibia length (F = 59.37, p < 0.005), femur length (F = 27.11, p < 0.005) and width (F = 8.84, p = 0.02), forceps length (F = 29.11, p < 0.005) and width (F = 27.59, p < 0.005), and elytra length (F = 9.78, p = 0.001). Pest management strategy significantly influenced unsigned asymmetry of the first antennal segment length (F = 39.58, p < 0.005), tibia length (F = 59.37, p < 0.005), femur width (F = 17.16, p < 0.005), and forceps length (F = 15.79, p < 0.005) but not of femur length (F = 1.099, p = 0.12), forceps width (F = 2.61, p = 0.07) and elytra length (F = 1.57, p = 0.21). Asymmetry was commonly more pronounced for the progeny of earwigs sampled in conventional orchards compared to organic orchards (Fig. 2 ). Discussion Fluctuating asymmetry (FA) has been frequently used in bilaterian animals as a biomarker of developmental instability caused by various environmental stresses (Beasley et al. 2013 ; Benitez et al. 2020) although it may sometimes estimate instability only poorly (Dongen 2006 ). In this study, we observed that FA also appeared through transgenerational effects in natural populations of the European earwig Forficula auricularia . Unexposed progeny of mothers from orchards using insecticides were indeed more asymmetric for four morphometric traits than those born from mothers sampled in orchards that did not use insecticides. Our results are consistent with many studies on arthropods that reported an increased FA caused by experimental insecticide exposure during development (Abaga et al. 2011 ; Chang et al. 2007 ) and a higher FA in natural populations exposed to treatments (Natero et al. 2019). Müller et al. ( 2017 ) reported in the beetle Phaedon cochleariaea that experimental exposure to pyrethroid of parents originating from lab breeding stock also increased FA of the antennae in the following unexposed generation, revealing transgenerational effects of insecticides on FA. Our study indicates that such transgenerational influence also occurs in natural earwig populations. Differences in FA between pest management strategies may not result from differences in insecticides’ applications but from differences in the mean value of the traits between populations (Hunt & Simmons 1997 ). Similarly to Le Navenant et al. ( 2021 ), we found for five bilateral traits that unexposed F1 individuals whose parents were sampled in conventional orchards exhibited smaller mean values than those whose parents were sampled in organic orchards. However, we did not detect any difference in FA between treatments for three traits -i.e. femur length, forceps width and elytra length- that differed in their mean value while we detected differences in FA for three traits -i.e. first antennal segment length, tibia length and femur width- that did not differ in their mean value. Differences in FA could thus not be explained by differences in mean values in our study. It is likely that increased FA in unexposed F1 was caused by insecticides’ applications. Moreover we noticed that FA was more pronounced in males than females for all traits, independently of pest management strategy, while there was no difference in mean size between sexes except for forceps length and width. We may hypothesize that FA would be counter-selected and thus less pronounced in the competitive sex than in the choosy one if mate choice based on symmetry occurred, as observed in several species (Møller 1993 ). In earwigs however, several studies confirmed that forceps length of males was used as a cue for mate choice by females but failed to observe any influence of FA of forceps length on sexual selection (Tomkins & Simmons 1995 ; Tomkins & Simmons 1998 ). Differential selection for symmetry between sexes could thus not explain our results. Pest management strategy had however a similar influence on FA for females and males, insecticides thus probably affect developmental stability in a similar way for both sexes. This result differs from Müller et al. ( 2017 ) who reported transgenerational influence of pyrethroid on FA only in females but not in males. Measuring FA on unexposed daughters and sons of individuals originating from natural ecosystems may thus be a reliable easy-to-use tool to monitor mid-term effects of insecticides in the environment. Declarations Funding. The authors declare that no funds, grants, or other support were received during the preparation of this manuscript. Competing interests. The authors have no relevant financial or non-financial interests to disclose. Author contributions. Joffrey Moiroux conceptualized and designed the experiment. Material preparation, data collection and analysis were performed by Joffrey Moiroux, Doufoungognon Carine Koné, Adiren le Navenant, Séverine Suchail and Magali Rault. The first draft of the manuscript was written by Joffrey Moiroux and all authors commented on previous versions of the manuscript. All authors read and approved the final manuscript. Ethical approval. Not applicable. Consent to participate. Not applicable. Consent for publication. Not applicable. Data availability. Not applicable. References Abaga NOZ, Alibert P, Dousset S, Savadogo PW, Savadogo M, Sedogo M (2011) Insecticide residues in cotton soils of Burkina Faso and effects of insecticides on fluctuating asymmetry in honey bees ( Apis mellifera Linnaeus). Chemosphere 83: 585-592 Albouy V, Caussanel C (1990) Dermaptères ou Perce-oreilles. Fédération française des sociétés de sciences naturelles Beasley DAE, Bonisoli-Alquati A, Mousseau TA -2013) The use of fluctuating asymmetry as a measure of environmentally induced developmental instability: A meta-analysis. Ecol Indic 30: 218-226 Benítez HA, Lemic D, Villalobos-Leiva A, Bažok R, Órdenes-Claveria R, Pajač Živković I, Mikac KM (2020) Breaking symmetry: Fluctuating asymmetry and geometric morphometrics as tools for evaluating developmental instability under diverse agroecosystems. Symmetry 12: 1789 Bonn A, Gasse M, Rolff J, Martens A (1996) Increased fluctuating asymmetry in the damselfly Coenagrion puella is correlated with ectoparasitic water mites: implications for fluctuating asymmetry theory. Oecologia 108: 596-598 Brevik K, Lindström L, McKay SD, Chen YH (2018) Transgenerational effects of insecticides—implications for rapid pest evolution in agroecosystems. Curr Opin Insect Sci 26: 34-40 Chang X, Zhai B, Wang M, Wang B (2007) Relationship between exposure to an insecticide and fluctuating asymmetry in a damselfly (Odonata, Coenagriidae). Hydrobiologia 586: 213-220 Chiaia-Hernandez AC, Keller A, Wächter D, Steinlin C, Camenzuli L, Hollender J, Krauss M (2017) Long-term persistence of pesticides and TPs in archived agricultural soil samples and comparison with pesticide application. Environ Sci Tech 51: 10642-10651 Clarke GM (1993). Fluctuating asymmetry of invertebrate populations as a biological indicator of environmental quality. Environ Pollut 82: 207-211 Costa MA, Moscardini VF, da Costa Gontijo P, Carvalho GA, de Oliveira RL, de Oliveira HN (2014) Sublethal and transgenerational effects of insecticides in developing Trichogramma galloi (Hymenoptera: Trichogrammatidae). Ecotoxicology 23: 1399-1408 Desneux N, Decourtye A, Delpuech J-M (2007) The sublethal effects of pesticides on beneficial arthropods. Annu Rev Entomol 52: 81–106 Dib H, Jamont M, Sauphanor B, Capowiez Y (2011) Predation potency and intraguild interactions between generalist ( Forficula auricularia ) and specialist ( Episyrphus balteatus ) predators of the rosy apple aphid ( Dysaphis plantaginea ). Biol Control 59: 90-97 Dongen SV (2006) Fluctuating asymmetry and developmental instability in evolutionary biology: past, present and future. J Evol Biol 19: 1727-1743 Ge LQ, Hu JH, Wu JC, Yang GQ, Gu H (2009) Insecticide-induced changes in protein, RNA, and DNA contents in ovary and fat body of female Nilaparvata lugens (Hemiptera: Delphacidae). J Econ Entomol 102: 1506-1514 Guo L, Desneux N, Sonoda S, Liang P, Han P, Gao XW (2013) Sublethal and transgenerational effects of chlorantraniliprole on biological traits of the diamondback moth, Plutella xylostella L. Crop Prot 48: 29-34 Habes D, Messiad R, Gouasmia S, Grib L (2013) Effects of an inorganic insecticide (boric acid) against Blattella germanica : Morphometric measurements and biochemical composition of ovaries. Afr J Biotech 12: 2492-2497 Hunt J, Simmons LW (1997) Patterns of fluctuating asymmetry in beetle horns: an experimental examination of the honest signalling hypothesis. Behav Ecol Sociobiol 41: 109-114 Le Navenant A, Brouchoud C, Capowiez Y, Rault M, Suchail S (2021) How lasting are the effects of pesticides on earwigs? A study based on energy metabolism, body weight and morphometry in two generations of Forficula auricularia from apple orchards. Sci Total Environ 758 : 14360 Le Navenant A, Siegwart M, Maugin S, Capowiez Y, Rault M (2019) Metabolic mechanisms and acetylcholinesterase sensitivity involved in tolerance to chlorpyrifos-ethyl in the earwig Forficula auricularia . Chemosphere 227: 416-424 Lens LUC, Van Dongen S, Kark S, Matthysen E (2002) Fluctuating asymmetry as an indicator of fitness: can we bridge the gap between studies? Biol Rev 77: 27-38 Malagnoux L, Capowiez Y, Rault M (2014) Tissue distribution, characterization and in vitro inhibition of B-esterases in the earwig Forficula auricularia. Chemosphere 112: 456-464 Malagnoux L, Capowiez Y, Rault M (2015) Impact of insecticide exposure on the predation activity of the European earwig Forficula auricularia . Environ Sci Pollut Res 22: 14116-14126 Møller AP (1993) Patterns of fluctuating asymmetry in sexual ornaments predict female choice. J Evol Biol 6: 481-491 Mpho M, Holloway GJ, Callaghan A (2001) A comparison of the effects of organophosphate insecticide exposure and temperature stress on fluctuating asymmetry and life history traits in Culex quinquefasciatus . Chemosphere 45: 713-720 Müller T, Prosche A, Müller C (2017) Sublethal insecticide exposure affects reproduction, chemical phenotype as well as offspring development and antennae symmetry of a leaf beetle. Environ Pollut 230: 709-717 Müller C (2018) Impacts of sublethal insecticide exposure on insects—Facts and knowledge gaps. Basic Appl Ecol 30: 1-10 Nattero J, Piccinali RV, Gaspe MS, Gürtler RE (2019) Fluctuating asymmetry and exposure to pyrethroid insecticides in Triatoma infestans populations in northeastern Argentina. Infection, Genetics and Evolution 74: 103925 Palmer AR, Strobeck C (1986) Fluctuating asymmetry: measurement, analysis, patterns. Annu Rev Ecol Syst 17: 391-421 Pisa L, Goulson D, Yang EC, Gibbons D, Sánchez-Bayo F, Mitchell E, ... & Bonmatin JM (2021) An update of the Worldwide Integrated Assessment (WIA) on systemic insecticides. Part 2: impacts on organisms and ecosystems. Environ Sci Pollut Res 28: 11749-11797 Polak M, Starmer WT (2001) The quantitative genetics of fluctuating asymmetry. Evolution 55 : 498-511 Sauphanor B, Chabrol L, d'Arcier FF, Sureau F, Lenfant C (1993) Side effects of diflubenzuron on a pear psylla predator: Forficula auricularia . Entomophaga 38: 163-174 Schulz R, Bub S, Petschick LL, Stehle S, Wolfram J (2021) Applied pesticide toxicity shifts toward plants and invertebrates, even in GM crops. Science 372: 81-84 Stehle S, Schulz R (2015) Agricultural insecticides threaten surface waters at the global scale. Proc Natl Acad Sci USA 112, 5750–5755 Stige LC, Hessen DO, Vøllestad LA (2006) Fitness, developmental instability, and the ontogeny of fluctuating asymmetry in Daphnia magna . Biol J Linn Soc 88: 179-192 Suchail S, Le Navenant A., Capowiez Y, Thiéry A, Rault M (2018) An exploratory study of energy reserves and biometry as potential tools for assessing the effects of pest management strategies on the earwig Forficula auricularia L. Environ Sci Pollut Res 25: 22766-22774 Szabó B, Lang Z, Bakonyi G, Mariën J, Roelofs D, van Gestel CA, Seres A (2019) Transgenerational and multigenerational stress gene responses to the insecticide etofenprox in Folsomia candida (Collembola). Ecotoxicol Environ Safe 175: 181-191 Tomkins JL, Simmons LW (1995) Patterns of fluctuating asymmetry in earwig forceps: no evidence for reliable signalling. Proc R Soc London B 259: 89-96 Tomkins JL, Simmons LW (1998) Female choice and manipulations of forceps size and symmetry in the earwig Forficula auricularia L. Anim Behav 56: 347-356 Wu RL, He W, Li YL, Li YY, Qin YF, Meng Q, ... Xu FL (2020). Residual concentrations and ecological risks of neonicotinoid insecticides in the soils of tomato and cucumber greenhouses in Shouguang, Shandong Province, East China. Sci Total Environ 738: 140248 Cite Share Download PDF Status: Posted Version 1 posted You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. As a division of Research Square Company, we’re committed to making research communication faster, fairer, and more useful. We do this by developing innovative software and high quality services for the global research community. Our growing team is made up of researchers and industry professionals working together to solve the most critical problems facing scientific publishing. Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-1395448","acceptedTermsAndConditions":true,"allowDirectSubmit":true,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":88735089,"identity":"54f4ac8e-d4d0-4082-ad4d-21ed50e703f0","order_by":0,"name":"Joffrey Moiroux","email":"data:image/png;base64,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","orcid":"https://orcid.org/0000-0002-0132-3763","institution":"UMR7263: Institut mediterraneen de biodiversite et d'ecologie marine et continentale","correspondingAuthor":true,"submittingAuthor":false,"prefix":"","firstName":"Joffrey","middleName":"","lastName":"Moiroux","suffix":""},{"id":88735090,"identity":"6915b2dd-ddfd-41bc-a0f2-face2e9f8704","order_by":1,"name":"Doufoungognon C. Koné","email":"","orcid":"","institution":"UMR7263: Institut mediterraneen de biodiversite et d'ecologie marine et continentale","correspondingAuthor":false,"submittingAuthor":false,"prefix":"","firstName":"Doufoungognon","middleName":"C.","lastName":"Koné","suffix":""},{"id":88735091,"identity":"6dccd6c1-8060-4a9c-b315-267cdb0d5f0c","order_by":2,"name":"Adrien Le Navenant","email":"","orcid":"","institution":"INRAE: Institut National de Recherche pour l'Agriculture l'Alimentation et l'Environnement","correspondingAuthor":false,"submittingAuthor":false,"prefix":"","firstName":"Adrien","middleName":"Le","lastName":"Navenant","suffix":""},{"id":88735092,"identity":"f8569b0e-0d41-41e2-b84a-e780f1264205","order_by":3,"name":"Séverine Suchail","email":"","orcid":"","institution":"UMR7263: Institut mediterraneen de biodiversite et d'ecologie marine et continentale","correspondingAuthor":false,"submittingAuthor":false,"prefix":"","firstName":"Séverine","middleName":"","lastName":"Suchail","suffix":""},{"id":88735093,"identity":"228c9ae7-bee1-4f5b-a32d-8bedcfaf4e76","order_by":4,"name":"Magali Rault","email":"","orcid":"","institution":"UMR7263: Institut mediterraneen de biodiversite et d'ecologie marine et continentale","correspondingAuthor":false,"submittingAuthor":false,"prefix":"","firstName":"Magali","middleName":"","lastName":"Rault","suffix":""}],"badges":[],"createdAt":"2022-02-25 10:22:25","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-1395448/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-1395448/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":19039429,"identity":"1dd0ead6-3402-4301-a716-e661399f0903","added_by":"auto","created_at":"2022-03-09 19:14:13","extension":"jpg","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":134699,"visible":true,"origin":"","legend":"\u003cp\u003eScanning electron microscope photography (Philips XL 30 ESEMwith detector SE) of a \u003cem\u003eForficula auricularia\u003c/em\u003e female (left). The equipment was set to operate at 20 kV acceleration voltage, at ×35 for the magnification and at 28.9 mm for the working distance. \u003c/p\u003e\u003cp\u003eMorphometric traits measured on \u003cem\u003eF. auricularia \u003c/em\u003eafter positioning adequately the individual are detailed on the right (adapted from Albouy \u0026amp; Caussanel 1990). ANL = first antennal segment length, FOL = forceps length, FOW = forceps width, ELL = elytra length, FML = femur length, FMW = femur width, TBL = tibia length. Measures of tibia and femur were performed on hind legs.\u003c/p\u003e\u003cp\u003e\u003cbr\u003e\u003c/p\u003e","description":"","filename":"FigureAF.jpg","url":"https://assets-eu.researchsquare.com/files/rs-1395448/v1/b58f5eb1bb6dc42a97022e34.jpg"},{"id":19039430,"identity":"5df6d16f-a7f4-4e81-8844-e04de50c8524","added_by":"auto","created_at":"2022-03-09 19:14:13","extension":"jpg","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":87933,"visible":true,"origin":"","legend":"\u003cp\u003e\u0026nbsp;Boxplots of unsigned fluctuating asymmetry of four morphometric traits that were significantly influenced by sex and pest management strategy in \u003cem\u003eF. auricularia\u003c/em\u003e. Different letters indicate significant differences between pest management strategy and sex (p\u0026lt;0.05).\u003c/p\u003e","description":"","filename":"Forfi.jpg","url":"https://assets-eu.researchsquare.com/files/rs-1395448/v1/7e8606243e9c52935955f845.jpg"},{"id":104003148,"identity":"67b0c34f-784f-40d6-83fb-ae108639a47b","added_by":"auto","created_at":"2026-03-05 14:27:16","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":700674,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-1395448/v1/df89524c-6ebc-47f8-a557-75400d1dbf39.pdf"}],"financialInterests":"","formattedTitle":"Transgenerational effects of pest management strategy on fluctuating asymmetry in the European earwig Forficula auricularia: Being the progeny of a mother who lived in conventional orchards makes you more asymmetric than having a mother who lived in insecticide free orchards.","fulltext":[{"header":"Introduction","content":"\u003cp\u003eChemical insecticides are a prominent strategy to manage insect pests despite their well-documented negative impact on ecosystems (Pisa et al. \u003cspan citationid=\"CR29\" class=\"CitationRef\"\u003e2021\u003c/span\u003e; Stehle \u0026amp; Schulz 2015; Schulz et al. \u003cspan citationid=\"CR32\" class=\"CitationRef\"\u003e2021\u003c/span\u003e). They are indeed known to commonly induce lethal and sublethal effects on non-target species, including beneficial organisms for agriculture such as pollinators or natural enemies (Desneux et al. \u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e2007\u003c/span\u003e; M\u0026uuml;ller \u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e2018\u003c/span\u003e). Their toxicity may last over time, sometimes several years after their use (Chiaia-Hernandez et al. \u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e2017\u003c/span\u003e; Wu et al. \u003cspan citationid=\"CR39\" class=\"CitationRef\"\u003e2020\u003c/span\u003e), and their long-term influence may extend over generations. Several studies thus reported transgenerational effects of parents\u0026rsquo; exposure to insecticides on unexposed progeny (Costa et al., \u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e2014\u003c/span\u003e; Le Navenant et al. \u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e2021\u003c/span\u003e), such as longer development and reduced hatching success (Guo et al. \u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e2013\u003c/span\u003e) or increased tolerance to insecticides (Le Navenant et al. \u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e2019\u003c/span\u003e). These transgenerational effects may arise from several processes, including a reduced ability of the parents to invest energy in their offspring (Szabo \u003cem\u003eet al.\u003c/em\u003e 2019), heritable epigenetic modifications (Brevik et al. \u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e2018\u003c/span\u003e), an accumulation of insecticides in ovaries (M\u0026uuml;ller et al. \u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e2017\u003c/span\u003e) or changes in ovaries\u0026rsquo; composition (Ge et al. \u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e2009\u003c/span\u003e, Habes et al. \u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e2013\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eThese two last mechanisms may notably affect developmental stability of offspring, causing indirect effects of insecticides on the next generation. It has been proposed that developmental instability may be estimated by measuring fluctuating asymmetry (FA) (Palmer \u0026amp; Strobeck, \u003cspan citationid=\"CR28\" class=\"CitationRef\"\u003e1986\u003c/span\u003e), defined as the random non-directional deviation from perfect bilateral symmetry in normally bilaterally symmetrical organisms (Clarke \u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e1993\u003c/span\u003e; Lens et al. \u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e2002\u003c/span\u003e). Many studies reported for example that FA was more pronounced when aquatic or terrestrial insects faced an environmental stress during their development, including insecticide exposure (Chang et al. \u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e2007\u003c/span\u003e; Mpho et al. \u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e2001\u003c/span\u003e), reduced nutrition (Hunt \u0026amp; Simmons \u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e1997\u003c/span\u003e), or increased parasite load (Bonn et al. \u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e1996\u003c/span\u003e). FA has thus been used as a reliable easy-to-use monitoring biomarker of environmental stresses in natural populations (Beasley et al. \u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e2013\u003c/span\u003e; Benitez \u003cem\u003eet al.\u003c/em\u003e2020).\u003c/p\u003e \u003cp\u003eAlthough measuring fluctuating asymmetry on unexposed progeny of individuals originating from natural populations may be an interesting procedure to monitor mid-term effects of insecticides, it has never been tested to our knowledge. In this paper, we investigated the transgenerational influence of pest management strategy on fluctuating asymmetry of the European earwig \u003cem\u003eForficula auricularia\u003c/em\u003e L. 1758 (Dermaptera: Forficulidae). This species is considered beneficial in apple and pear orchards since it predates several pest species such as aphids, leaf rollers and psyllids ( Dib et al. \u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e2011\u003c/span\u003e). Several studies reported that insecticides directly affect their morphology (Suchail et al. \u003cspan citationid=\"CR35\" class=\"CitationRef\"\u003e2018\u003c/span\u003e), biochemical pathways (Malagnoux et al. \u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e2014\u003c/span\u003e) or behavior (Sauphanor et al. \u003cspan citationid=\"CR31\" class=\"CitationRef\"\u003e1993\u003c/span\u003e; Malagnoux et al. \u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e2015\u003c/span\u003e). Transgenerational effects have also been observed. Unexposed F1 females whose parents were previously sampled in conventional orchards indeed exhibited a significantly smaller femur than those whose parents were sampled in integrated or organic orchards (Le Navenant et al. \u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e2021\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eWe measured FA on unexposed progeny of earwig mothers sampled in orchards with no to frequent insecticides\u0026rsquo; applications to test for the relevance of this procedure as a biomarker of long-term impact of pest management strategy on natural populations. We hypothesized that FA would be more pronounced for progeny born from mothers sampled in orchards using frequently insecticides than for progeny born from mothers sampled in orchards using no to few treatments.\u003c/p\u003e"},{"header":"Material And Methods","content":"\u003ch2\u003e1.1 Sampling and rearing\u003c/h2\u003e\n\u003cp\u003e\u003cem\u003eForficula auricularia\u003c/em\u003e adults were sampled in October 2015 using cardboard traps placed on tree branches in nine orchards located in the vicinity of Avignon, south-eastern France. These 6 apple and 3 pear orchards were classified in three different categories depending on their legal classification (Organic) and respective pesticide management strategy (Integrated Pest Management (IPM) vs Conventional). The three conventional orchards used 6 to 9 chemical insecticide treatments while the three IPM orchards used one to two insecticide treatments in 2015. The three organic orchards did not use any insecticide, including those approved in organic farming such as spinosyns.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eSampled females were placed separately in Petri Dishes in an open shelter, under natural photoperiod and climate. Food and water were provided \u003cem\u003ead libitum\u003c/em\u003e. Eggs were laid starting from December and progeny were kept with their mother until they reached the third instar. L3 earwigs were then placed altogether until their reached adulthood. Fifteen to twenty-five individuals per orchard and per sex were then removed randomly and frozen for later measurement.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eSince insecticides applications stopped mid-August in the sampled orchards and mating generally occurs in late august and early September in south-eastern France for this species, individuals used for measurements were never directly exposed to insecticides during their development, although they may have been in maternal tissues where traces of products may have remained.\u0026nbsp;\u003c/p\u003e\n\u003ch2\u003e1.2 Morphometric measurements\u003c/h2\u003e\n\u003cp\u003eAfter being slightly thawed at room temperature, each earwig was positioned carefully under a binocular (Nikon SMZ 745T) linked to a camera (TOUPCAM U3CMOS) and seven morphometric variables were measured twice on both right and left side using the software ToupView. We measured (1) the first antennal segment length, (2) forceps length and (3) width, (4) elytra length, and on hind legs, the femur (5) length and (6) width and (7) tibia length, as described in Figure 1.\u0026nbsp;\u003c/p\u003e\n\u003ch2\u003e1.3 Statistical analysis.\u0026nbsp;\u003c/h2\u003e\n\u003cp\u003eRepeated measures ANOVA confirmed significantly greater variance between individuals than between repeated measures. The mean value of the two measures performed per side was thus used for statistical analyses. Signed fluctuating asymmetry was calculated as the value of left minus right measures. These values were normally distributed for all morphometric parameters, we therefore considered that significant differences from zero would indicate fluctuating asymmetry. Unsigned fluctuating asymmetry, i.e. the absolute values of left minus right measures (Polak \u0026amp; Starmer 2001; Stige\u0026nbsp;\u003cem\u003eet al.\u003c/em\u003e 2006), was used for statistical analyses. ANOVA were performed to test for differences in the mean value of each side and on unsigned fluctuating asymmetry of the seven morphometric variables with sex and pest management strategy as explanatory factors. ANCOVA were also performed with the mean of the trait as a covariate but it did not significantly influence the effect of pest management strategy on asymmetry for any trait.\u003cbr\u003e\u0026nbsp;\u003c/p\u003e"},{"header":"Results","content":"\u003cp\u003eWe did not observe any influence of the sex on the mean value of the morphometric traits except for longer (left: F\u0026thinsp;=\u0026thinsp;28.71, p\u0026thinsp;\u0026lt;\u0026thinsp;0.005; right: F\u0026thinsp;=\u0026thinsp;55.87, p\u0026thinsp;\u0026lt;\u0026thinsp;0.005) and wider (left: F\u0026thinsp;=\u0026thinsp;155.14, p\u0026thinsp;\u0026lt;\u0026thinsp;0.005; right: F\u0026thinsp;=\u0026thinsp;166.97, p\u0026thinsp;\u0026lt;\u0026thinsp;0.005) forceps in males. The interaction between sex and pest management strategy did not influence any morphometric trait but pest management strategy alone did for femur length (left: F\u0026thinsp;=\u0026thinsp;34.02, p\u0026thinsp;\u0026lt;\u0026thinsp;0.005; right: F\u0026thinsp;=\u0026thinsp;32.75, p\u0026thinsp;\u0026lt;\u0026thinsp;0.005), forceps length (left: F\u0026thinsp;=\u0026thinsp;13.01, p\u0026thinsp;\u0026lt;\u0026thinsp;0.005; right: F\u0026thinsp;=\u0026thinsp;25.20, p\u0026thinsp;\u0026lt;\u0026thinsp;0.005) and width (left: F\u0026thinsp;=\u0026thinsp;20.62, p\u0026thinsp;\u0026lt;\u0026thinsp;0.005; right: F\u0026thinsp;=\u0026thinsp;11.89, p\u0026thinsp;\u0026lt;\u0026thinsp;0.005), and elytra length (left: F\u0026thinsp;=\u0026thinsp;18.31, p\u0026thinsp;\u0026lt;\u0026thinsp;0.005; right: F\u0026thinsp;=\u0026thinsp;25.83, p\u0026thinsp;\u0026lt;\u0026thinsp;0.005). Progeny of earwigs sampled in conventional orchards were commonly smaller for these four traits than those whose parents were sampled in organic orchards.\u003c/p\u003e \u003cp\u003eSex and pest management strategy both significantly influenced unsigned asymmetry of several morphometric traits while the interaction between these two factors did not, except for tibia length (F\u0026thinsp;=\u0026thinsp;3.24, p\u0026thinsp;=\u0026thinsp;0.03). Asymmetry was more pronounced in males than females for every trait, i.e. the first antennal segment (F\u0026thinsp;=\u0026thinsp;20.42, p\u0026thinsp;\u0026lt;\u0026thinsp;0.005), tibia length (F\u0026thinsp;=\u0026thinsp;59.37, p\u0026thinsp;\u0026lt;\u0026thinsp;0.005), femur length (F\u0026thinsp;=\u0026thinsp;27.11, p\u0026thinsp;\u0026lt;\u0026thinsp;0.005) and width (F\u0026thinsp;=\u0026thinsp;8.84, p\u0026thinsp;=\u0026thinsp;0.02), forceps length (F\u0026thinsp;=\u0026thinsp;29.11, p\u0026thinsp;\u0026lt;\u0026thinsp;0.005) and width (F\u0026thinsp;=\u0026thinsp;27.59, p\u0026thinsp;\u0026lt;\u0026thinsp;0.005), and elytra length (F\u0026thinsp;=\u0026thinsp;9.78, p\u0026thinsp;=\u0026thinsp;0.001). Pest management strategy significantly influenced unsigned asymmetry of the first antennal segment length (F\u0026thinsp;=\u0026thinsp;39.58, p\u0026thinsp;\u0026lt;\u0026thinsp;0.005), tibia length (F\u0026thinsp;=\u0026thinsp;59.37, p\u0026thinsp;\u0026lt;\u0026thinsp;0.005), femur width (F\u0026thinsp;=\u0026thinsp;17.16, p\u0026thinsp;\u0026lt;\u0026thinsp;0.005), and forceps length (F\u0026thinsp;=\u0026thinsp;15.79, p\u0026thinsp;\u0026lt;\u0026thinsp;0.005) but not of femur length (F\u0026thinsp;=\u0026thinsp;1.099, p\u0026thinsp;=\u0026thinsp;0.12), forceps width (F\u0026thinsp;=\u0026thinsp;2.61, p\u0026thinsp;=\u0026thinsp;0.07) and elytra length (F\u0026thinsp;=\u0026thinsp;1.57, p\u0026thinsp;=\u0026thinsp;0.21). Asymmetry was commonly more pronounced for the progeny of earwigs sampled in conventional orchards compared to organic orchards (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e).\u003c/p\u003e \u003cp\u003e \u003c/p\u003e"},{"header":"Discussion","content":"\u003cp\u003eFluctuating asymmetry (FA) has been frequently used in bilaterian animals as a biomarker of developmental instability caused by various environmental stresses (Beasley et al. \u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e2013\u003c/span\u003e; Benitez \u003cem\u003eet al.\u003c/em\u003e2020) although it may sometimes estimate instability only poorly (Dongen \u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e2006\u003c/span\u003e). In this study, we observed that FA also appeared through transgenerational effects in natural populations of the European earwig \u003cem\u003eForficula auricularia\u003c/em\u003e. Unexposed progeny of mothers from orchards using insecticides were indeed more asymmetric for four morphometric traits than those born from mothers sampled in orchards that did not use insecticides.\u003c/p\u003e \u003cp\u003eOur results are consistent with many studies on arthropods that reported an increased FA caused by experimental insecticide exposure during development (Abaga et al. \u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e2011\u003c/span\u003e; Chang et al. \u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e2007\u003c/span\u003e) and a higher FA in natural populations exposed to treatments (Natero \u003cem\u003eet al.\u003c/em\u003e2019). M\u0026uuml;ller et al. (\u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e2017\u003c/span\u003e) reported in the beetle \u003cem\u003ePhaedon cochleariaea\u003c/em\u003e that experimental exposure to pyrethroid of parents originating from lab breeding stock also increased FA of the antennae in the following unexposed generation, revealing transgenerational effects of insecticides on FA. Our study indicates that such transgenerational influence also occurs in natural earwig populations.\u003c/p\u003e \u003cp\u003eDifferences in FA between pest management strategies may not result from differences in insecticides\u0026rsquo; applications but from differences in the mean value of the traits between populations (Hunt \u0026amp; Simmons \u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e1997\u003c/span\u003e). Similarly to Le Navenant et al. (\u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e2021\u003c/span\u003e), we found for five bilateral traits that unexposed F1 individuals whose parents were sampled in conventional orchards exhibited smaller mean values than those whose parents were sampled in organic orchards. However, we did not detect any difference in FA between treatments for three traits -i.e. femur length, forceps width and elytra length- that differed in their mean value while we detected differences in FA for three traits -i.e. first antennal segment length, tibia length and femur width- that did not differ in their mean value. Differences in FA could thus not be explained by differences in mean values in our study. It is likely that increased FA in unexposed F1 was caused by insecticides\u0026rsquo; applications.\u003c/p\u003e \u003cp\u003eMoreover we noticed that FA was more pronounced in males than females for all traits, independently of pest management strategy, while there was no difference in mean size between sexes except for forceps length and width. We may hypothesize that FA would be counter-selected and thus less pronounced in the competitive sex than in the choosy one if mate choice based on symmetry occurred, as observed in several species (M\u0026oslash;ller \u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e1993\u003c/span\u003e). In earwigs however, several studies confirmed that forceps length of males was used as a cue for mate choice by females but failed to observe any influence of FA of forceps length on sexual selection (Tomkins \u0026amp; Simmons \u003cspan citationid=\"CR37\" class=\"CitationRef\"\u003e1995\u003c/span\u003e; Tomkins \u0026amp; Simmons \u003cspan citationid=\"CR38\" class=\"CitationRef\"\u003e1998\u003c/span\u003e). Differential selection for symmetry between sexes could thus not explain our results. Pest management strategy had however a similar influence on FA for females and males, insecticides thus probably affect developmental stability in a similar way for both sexes. This result differs from M\u0026uuml;ller et al. (\u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e2017\u003c/span\u003e) who reported transgenerational influence of pyrethroid on FA only in females but not in males. Measuring FA on unexposed daughters and sons of individuals originating from natural ecosystems may thus be a reliable easy-to-use tool to monitor mid-term effects of insecticides in the environment.\u003c/p\u003e "},{"header":"Declarations","content":"\u003ch2\u003e\u003cem\u003eFunding.\u003c/em\u003e\u003cem\u003e\u0026nbsp;\u003c/em\u003e\u003c/h2\u003e\n\u003cp\u003e\u003cem\u003eThe authors declare that no funds, grants, or other support were received during the preparation of this manuscript.\u003c/em\u003e\u003cem\u003e\u0026nbsp;\u003c/em\u003e\u003c/p\u003e\n\u003ch2\u003e\u003cem\u003eCompeting interests.\u003c/em\u003e\u003cem\u003e\u0026nbsp;\u003c/em\u003e\u003c/h2\u003e\n\u003cp\u003e\u003cem\u003eThe authors have no relevant financial or non-financial interests to disclose.\u003c/em\u003e\u003cem\u003e\u0026nbsp;\u003c/em\u003e\u003c/p\u003e\n\u003ch2\u003eAuthor contributions.\u0026nbsp;\u003c/h2\u003e\n\u003cp\u003eJoffrey Moiroux conceptualized and designed the experiment. Material preparation, data collection and analysis were performed by Joffrey Moiroux, Doufoungognon Carine Kon\u0026eacute;, Adiren le Navenant, S\u0026eacute;verine Suchail and Magali Rault. The first draft of the manuscript was written by Joffrey Moiroux and all authors commented on previous versions of the manuscript. All authors read and approved the final manuscript.\u0026nbsp;\u003c/p\u003e\n\u003ch2\u003eEthical approval.\u0026nbsp;\u003c/h2\u003e\n\u003cp\u003eNot applicable.\u0026nbsp;\u003c/p\u003e\n\u003ch2\u003eConsent to participate.\u0026nbsp;\u003c/h2\u003e\n\u003cp\u003eNot applicable.\u0026nbsp;\u003c/p\u003e\n\u003ch2\u003eConsent for publication.\u0026nbsp;\u003c/h2\u003e\n\u003cp\u003eNot applicable.\u0026nbsp;\u003c/p\u003e\n\u003ch2\u003eData availability.\u0026nbsp;\u003c/h2\u003e\n\u003cp\u003eNot applicable.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\n \u003cli\u003eAbaga NOZ, Alibert P, Dousset S, Savadogo PW, Savadogo M, Sedogo M (2011) Insecticide residues in cotton soils of Burkina Faso and effects of insecticides on fluctuating asymmetry in honey bees (\u003cem\u003eApis mellifera\u003c/em\u003e Linnaeus). Chemosphere 83: 585-592\u003c/li\u003e\n \u003cli\u003eAlbouy V, Caussanel C (1990) Dermapt\u0026egrave;res ou Perce-oreilles. F\u0026eacute;d\u0026eacute;ration fran\u0026ccedil;aise des soci\u0026eacute;t\u0026eacute;s de sciences naturelles\u003c/li\u003e\n \u003cli\u003eBeasley DAE, Bonisoli-Alquati A, Mousseau TA -2013) The use of fluctuating asymmetry as a measure of environmentally induced developmental instability: A meta-analysis. Ecol Indic 30: 218-226\u003c/li\u003e\n \u003cli\u003eBen\u0026iacute;tez HA, Lemic D, Villalobos-Leiva A, Bažok R, \u0026Oacute;rdenes-Claveria R, Pajač Živković I, Mikac KM (2020) Breaking symmetry: Fluctuating asymmetry and geometric morphometrics as tools for evaluating developmental instability under diverse agroecosystems. Symmetry 12: 1789\u003c/li\u003e\n \u003cli\u003eBonn A, Gasse M, Rolff J, Martens A (1996) Increased fluctuating asymmetry in the damselfly \u003cem\u003eCoenagrion puella\u003c/em\u003e is correlated with ectoparasitic water mites: implications for fluctuating asymmetry theory. Oecologia 108: 596-598\u003c/li\u003e\n \u003cli\u003eBrevik K, Lindstr\u0026ouml;m L, McKay SD, Chen YH (2018) Transgenerational effects of insecticides\u0026mdash;implications for rapid pest evolution in agroecosystems. Curr Opin Insect Sci 26: 34-40\u003c/li\u003e\n \u003cli\u003eChang X, Zhai B, Wang M, Wang B (2007) Relationship between exposure to an insecticide and fluctuating asymmetry in a damselfly (Odonata, Coenagriidae). Hydrobiologia 586: 213-220\u003c/li\u003e\n \u003cli\u003eChiaia-Hernandez AC, Keller A, Wächter D, Steinlin C, Camenzuli L, Hollender J, Krauss M (2017) Long-term persistence of pesticides and TPs in archived agricultural soil samples and comparison with pesticide application. Environ Sci Tech 51: 10642-10651\u003c/li\u003e\n \u003cli\u003eClarke GM (1993). Fluctuating asymmetry of invertebrate populations as a biological indicator of environmental quality. Environ Pollut 82: 207-211\u003c/li\u003e\n \u003cli\u003eCosta MA, Moscardini VF, da Costa Gontijo P, Carvalho GA, de Oliveira RL, de Oliveira HN (2014) Sublethal and transgenerational effects of insecticides in developing \u003cem\u003eTrichogramma galloi\u003c/em\u003e (Hymenoptera: Trichogrammatidae). Ecotoxicology 23: 1399-1408\u003c/li\u003e\n \u003cli\u003eDesneux N, Decourtye A, Delpuech J-M (2007) The sublethal effects of pesticides on beneficial arthropods. Annu Rev Entomol 52: 81\u0026ndash;106\u003c/li\u003e\n \u003cli\u003eDib H, Jamont M, Sauphanor B, Capowiez Y (2011) Predation potency and intraguild interactions between generalist (\u003cem\u003eForficula auricularia\u003c/em\u003e) and specialist (\u003cem\u003eEpisyrphus balteatus\u003c/em\u003e) predators of the rosy apple aphid (\u003cem\u003eDysaphis plantaginea\u003c/em\u003e). Biol Control 59: 90-97\u003c/li\u003e\n \u003cli\u003eDongen SV (2006) Fluctuating asymmetry and developmental instability in evolutionary biology: past, present and future. J Evol Biol 19: 1727-1743\u003c/li\u003e\n \u003cli\u003eGe LQ, Hu JH, Wu JC, Yang GQ, Gu H (2009) Insecticide-induced changes in protein, RNA, and DNA contents in ovary and fat body of female \u003cem\u003eNilaparvata lugens\u003c/em\u003e (Hemiptera: Delphacidae). J Econ Entomol 102: 1506-1514\u003c/li\u003e\n \u003cli\u003eGuo L, Desneux N, Sonoda S, Liang P, Han P, Gao XW (2013) Sublethal and transgenerational effects of chlorantraniliprole on biological traits of the diamondback moth, \u003cem\u003ePlutella xylostella\u003c/em\u003e L. Crop Prot 48: 29-34\u003c/li\u003e\n \u003cli\u003eHabes D, Messiad R, Gouasmia S, Grib L (2013) Effects of an inorganic insecticide (boric acid) against \u003cem\u003eBlattella germanica\u003c/em\u003e: Morphometric measurements and biochemical composition of ovaries. Afr J Biotech 12: 2492-2497\u003c/li\u003e\n \u003cli\u003eHunt J, Simmons LW (1997) Patterns of fluctuating asymmetry in beetle horns: an experimental examination of the honest signalling hypothesis. Behav Ecol Sociobiol 41: 109-114\u003c/li\u003e\n \u003cli\u003eLe Navenant A,\u0026nbsp;Brouchoud C, Capowiez Y, Rault M, Suchail S (2021) How lasting are the effects of pesticides on earwigs? A study based on energy metabolism, body weight and morphometry in two generations\u0026nbsp;of \u003cem\u003eForficula auricularia\u003c/em\u003e from apple orchards. Sci Total Environ 758 : 14360\u003c/li\u003e\n \u003cli\u003eLe Navenant A, Siegwart M, Maugin S, Capowiez Y, Rault M (2019) Metabolic mechanisms and acetylcholinesterase sensitivity involved in tolerance to chlorpyrifos-ethyl in the earwig \u003cem\u003eForficula auricularia\u003c/em\u003e. Chemosphere 227: 416-424\u003c/li\u003e\n \u003cli\u003eLens LUC, Van Dongen S, Kark S, Matthysen E (2002) Fluctuating asymmetry as an indicator of fitness: can we bridge the gap between studies? Biol Rev 77: 27-38\u003c/li\u003e\n \u003cli\u003eMalagnoux L, Capowiez Y, Rault M (2014)\u0026nbsp;Tissue distribution,\u0026nbsp;characterization and in vitro inhibition of B-esterases in the earwig \u003cem\u003eForficula auricularia.\u003c/em\u003e Chemosphere 112: 456-464\u003c/li\u003e\n \u003cli\u003eMalagnoux L, Capowiez Y, Rault M (2015)\u0026nbsp;Impact of insecticide exposure on the predation activity of the European earwig \u003cem\u003eForficula auricularia\u003c/em\u003e. Environ Sci Pollut Res 22: 14116-14126\u003c/li\u003e\n \u003cli\u003eM\u0026oslash;ller\u0026nbsp;AP (1993) Patterns of fluctuating asymmetry in sexual ornaments predict female choice. J Evol Biol 6: 481-491\u003c/li\u003e\n \u003cli\u003eMpho M, Holloway GJ, Callaghan A (2001) A comparison of the effects of organophosphate insecticide exposure and temperature stress on fluctuating asymmetry and life history traits in \u003cem\u003eCulex quinquefasciatus\u003c/em\u003e. Chemosphere 45: 713-720\u003c/li\u003e\n \u003cli\u003eM\u0026uuml;ller T, Prosche A, M\u0026uuml;ller C (2017) Sublethal insecticide exposure affects reproduction, chemical phenotype as well as offspring development and antennae symmetry of a leaf beetle. Environ Pollut 230: 709-717\u003c/li\u003e\n \u003cli\u003eM\u0026uuml;ller C (2018) Impacts of sublethal insecticide exposure on insects\u0026mdash;Facts and knowledge gaps. Basic Appl Ecol 30: 1-10\u003c/li\u003e\n \u003cli\u003eNattero J, Piccinali RV, Gaspe MS, G\u0026uuml;rtler RE (2019) Fluctuating asymmetry and exposure to pyrethroid insecticides in \u003cem\u003eTriatoma infestans\u003c/em\u003e populations in northeastern Argentina. Infection, Genetics and Evolution 74: 103925\u003c/li\u003e\n \u003cli\u003ePalmer AR, Strobeck C (1986) Fluctuating asymmetry: measurement, analysis, patterns. Annu Rev Ecol Syst 17: 391-421\u003c/li\u003e\n \u003cli\u003ePisa L, Goulson D, Yang EC, Gibbons D, S\u0026aacute;nchez-Bayo F, Mitchell E, ... \u0026amp; Bonmatin JM (2021) An update of the Worldwide Integrated Assessment (WIA) on systemic insecticides. Part 2: impacts on organisms and ecosystems.\u0026nbsp;Environ Sci Pollut Res\u0026nbsp;28: 11749-11797\u003c/li\u003e\n \u003cli\u003ePolak M, Starmer WT (2001) The quantitative genetics of fluctuating asymmetry. Evolution 55\u0026nbsp;: 498-511\u003c/li\u003e\n \u003cli\u003eSauphanor B, Chabrol L, d\u0026apos;Arcier FF, Sureau F, Lenfant C (1993) Side effects of diflubenzuron on a pear psylla predator: \u003cem\u003eForficula auricularia\u003c/em\u003e. Entomophaga 38: 163-174\u003c/li\u003e\n \u003cli\u003eSchulz R, Bub S, Petschick LL, Stehle S, Wolfram J (2021) Applied pesticide toxicity shifts toward plants and invertebrates, even in GM crops. Science 372: 81-84\u003c/li\u003e\n \u003cli\u003eStehle S, Schulz R (2015) Agricultural insecticides threaten surface waters at the global scale. Proc Natl Acad Sci USA 112, 5750\u0026ndash;5755\u003c/li\u003e\n \u003cli\u003eStige LC, Hessen DO, V\u0026oslash;llestad LA (2006) Fitness, developmental instability, and the ontogeny of fluctuating asymmetry in \u003cem\u003eDaphnia magna\u003c/em\u003e. Biol J Linn Soc 88: 179-192\u003c/li\u003e\n \u003cli\u003eSuchail S, Le Navenant A., Capowiez Y, Thi\u0026eacute;ry A, Rault M (2018) An exploratory study of energy reserves and biometry as potential tools for assessing the effects of pest management strategies on the earwig \u003cem\u003eForficula auricularia\u003c/em\u003e L.\u0026nbsp;Environ Sci Pollut Res\u0026nbsp;\u0026nbsp;25: 22766-22774\u0026nbsp;\u003c/li\u003e\n \u003cli\u003eSzab\u0026oacute; B, Lang Z, Bakonyi G, Mari\u0026euml;n J, Roelofs D, van Gestel CA, Seres A (2019) Transgenerational and multigenerational stress gene responses to the insecticide etofenprox in \u003cem\u003eFolsomia candida\u003c/em\u003e (Collembola). Ecotoxicol Environ Safe 175: 181-191\u003c/li\u003e\n \u003cli\u003eTomkins JL, Simmons LW (1995) Patterns of fluctuating asymmetry in earwig forceps: no evidence for reliable signalling. Proc R Soc London B 259: 89-96\u003c/li\u003e\n \u003cli\u003eTomkins JL, Simmons LW (1998) Female choice and manipulations of forceps size and symmetry in the earwig \u003cem\u003eForficula auricularia\u003c/em\u003e L. Anim Behav 56: 347-356\u003c/li\u003e\n \u003cli\u003eWu RL, He W, Li YL, Li YY, Qin YF, Meng Q, ... Xu FL (2020). Residual concentrations and ecological risks of neonicotinoid insecticides in the soils of tomato and cucumber greenhouses in Shouguang, Shandong Province, East China. Sci Total Environ 738: 140248\u003c/li\u003e\n\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":true,"highlight":"","institution":"","isAcceptedByJournal":false,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true},"keywords":"Biomarker, Developmental stability, Morphometry, Pesticides, Terrestrial arthropods","lastPublishedDoi":"10.21203/rs.3.rs-1395448/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-1395448/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eFluctuating asymmetry (FA), defined as the random non-directional deviation from perfect bilateral symmetry, is considered to reflect developmental instability in bilaterally symmetrical organisms. It has been commonly used as a reliable biomarker of environmental stresses in natural populations. In agroecosystems, FA may arise through transgenerational influence of insecticides. We measured fluctuating asymmetry on unexposed progeny of \u003cem\u003eForficula auricularia\u003c/em\u003e mothers sampled in orchards that used no to frequent insecticides\u0026rsquo; applications. Seven morphometric traits were measured on both right and left side and fluctuating asymmetry was calculated. Among these seven traits, four were more asymmetric when the progeny was born from a mother who lived in conventional orchards that used insecticides frequently compared to a mother who lived in insecticide free orchards. Males were more asymmetric than females for all traits but pest management strategy influenced FA in a similar way for both sexes. Measuring FA on unexposed daughters and sons of individuals originating from natural ecosystems may thus be a reliable easy-to-use tool to monitor mid-term effects of insecticides in the environment.\u003c/p\u003e","manuscriptTitle":"Transgenerational effects of pest management strategy on fluctuating asymmetry in the European earwig Forficula auricularia: Being the progeny of a mother who lived in conventional orchards makes you more asymmetric than having a mother who lived in insecticide free orchards.","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2022-03-09 19:14:11","doi":"10.21203/rs.3.rs-1395448/v1","editorialEvents":[{"type":"communityComments","content":0}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"e7113b1a-a939-472b-a743-63cf856a632e","owner":[],"postedDate":"March 9th, 2022","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"posted","subjectAreas":[],"tags":[],"updatedAt":"2026-03-05T14:25:06+00:00","versionOfRecord":[],"versionCreatedAt":"2022-03-09 19:14:11","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-1395448","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-1395448","identity":"rs-1395448","version":["v1"]},"buildId":"-HB7Z8yhvgn0wM9Nzuekk","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}