26 research outputs found

    War in the darkness: Association of semiochemicals and entomopathogens to control wireworms

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    Wireworms (Coleoptera: Elateridae) are generalist insect pests attacking a wide range of plants, causing significant damages in agriculture. They feed on seeds, roots or crown and are particularly impactful on young seedlings. Wireworms locate their hosts using different cues including Volatiles Organic Compounds (VOCs) released in the rhizosphere and guiding the larvae to an appropriate host. In this study, we aimed at developing an Attract-and-kill strategy by setting up two distinct objectives : (1) comparing the attraction potential of different semiochemicals and (2) identify strains of entomopathogenic fungi and nematodes that are efficient in killing wireworms. Plant natural extracts were encapsulated in alginate beads and were shown to attract up to 76% of the tested wireworms, during behavioral assays performed in two-way olfactometers. We then performed volatile collection on these alginate beads and revealed that beads released a blend of eight VOCs, of which acetoin was the one released in higher quantity. Finally, the virulence of twelve strains of entomopathogenic fungi and eleven strains of entomopathogenic nematodes was evaluated. Two species of Metarhizium and one species of Ophiocordyceps were the most virulent against wireworms, leading to mortality levels of 39%, 50% and 57%, respectively. Three entomopathogenic nematodes strains of species Heterorhabditis bacteriophora were highly effective in killing wireworms (88 %, 53 %, and 53 % of mortality). The encapsulation of natural extracts in alginate beads appears to be a promising lure to manipulate wireworms behavior, while the co-encapsulation with entomopathogenic fungi and nematodes remains the major challenge for the development of a new Attract-and-kill strategyNEMACO

    Behavioural study of interactions between wandering wolf spider female, Pardosa saltans (Araneae), and her egg-sac.

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    Les soins parentaux sont observés dans de nombreux taxons et sont exprimés de façon plus ou moins complexe. L’étude de ces comportements chez les arthropodes, en particulier chez les araignées, nous permet de mieux comprendre comment les soins à la progéniture se sont mis en place au cours de l’évolution. Au cours de cette thèse nous avons étudié le comportement d’une espèce errante Pardosa saltans (Lycosidae) vis-à-vis de son cocon, puis de ses jeunes. Nous avons décrit les comportements manifestés par la mère pendant toute la période de soin au cocon (période de développement embryonnaire et postembryonnaire des jeunes). Notre étude a permis de mettre en évidence qu’il existe une ontogenèse comportementale dans le cadre des soins parentaux chez cette espèce. Elle a permis également d’évaluer les dépenses énergétiques subies par la mère pendant cette période. Et enfin nous avons identifié, pour la première fois, les composés chimiques présents à la surface du cocon. Nos expériences montrent que ces composés chimiques associés aux vibrations émises par les juvéniles à l’intérieur du cocon sont utilisés par la mère détecter l’état de développement de sa progéniture.Parental care is widespread among animal kingdom and is more or less expressed. Thus, the study of these behaviours among primitive species, can let us understand how parental behaviours were implemented during evolution. In this thesis we studied maternal behaviour in a wandering spider Pardosa saltans (Lycosidae) with her egg-sac and her young which she actively transports. We have described maternal behaviour towards the egg-sac and highlighted the presence of ontogeny of maternal behavior in this species. Furthermore, we were able to evaluate some of the physiological and ecological investment associated with maternal care of the egg-sac and young. Finally, we have, for the first time, identify chemical compounds on the surface of the silk egg-sac, and placed in evidence the presence of a chemical and vibrational communication between the mother and her cocoon

    Étude comportementale des interactions entre une mère lycose errante, Pardosa saltans (Araneae), et son cocon

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    Parental care is widespread among animal kingdom and is more or less expressed. Thus, the study of these behaviours among primitive species, can let us understand how parental behaviours were implemented during evolution. In this thesis we studied maternal behaviour in a wandering spider Pardosa saltans (Lycosidae) with her egg-sac and her young which she actively transports. We have described maternal behaviour towards the egg-sac and highlighted the presence of ontogeny of maternal behavior in this species. Furthermore, we were able to evaluate some of the physiological and ecological investment associated with maternal care of the egg-sac and young. Finally, we have, for the first time, identify chemical compounds on the surface of the silk egg-sac, and placed in evidence the presence of a chemical and vibrational communication between the mother and her cocoon.Les soins parentaux sont observés dans de nombreux taxons et sont exprimés de façon plus ou moins complexe. L’étude de ces comportements chez les arthropodes, en particulier chez les araignées, nous permet de mieux comprendre comment les soins à la progéniture se sont mis en place au cours de l’évolution. Au cours de cette thèse nous avons étudié le comportement d’une espèce errante Pardosa saltans (Lycosidae) vis-à-vis de son cocon, puis de ses jeunes. Nous avons décrit les comportements manifestés par la mère pendant toute la période de soin au cocon (période de développement embryonnaire et postembryonnaire des jeunes). Notre étude a permis de mettre en évidence qu’il existe une ontogenèse comportementale dans le cadre des soins parentaux chez cette espèce. Elle a permis également d’évaluer les dépenses énergétiques subies par la mère pendant cette période. Et enfin nous avons identifié, pour la première fois, les composés chimiques présents à la surface du cocon. Nos expériences montrent que ces composés chimiques associés aux vibrations émises par les juvéniles à l’intérieur du cocon sont utilisés par la mère détecter l’état de développement de sa progéniture

    Physiological costs during maternal care in Pardosa saltans (Araneae, Lycosidae)

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    International audienceMany arachnids, like other terrestrial arthropods, provide extensive maternal care. Few studies have quantified the underlying physiological costs of maternalcare. We investigated how maternal care affects the free-moving wolf spider’s (Pardosa saltans) energy requirements. Our aim was to evaluate the contributions of protein, glucose and lipids to the maintenance of female P. saltans’ energy

    Les termites s'invitent en région Centre-Val de Loire

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    Physiological costs during the first maternal care in the wolf spider Pardosa saltans (Araneae, Lycosidae)

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    International audienceMany arachnids like other terrestrial arthropods, provide extensive maternal care. Few studies havequantified the underlying physiological costs of maternal care. We investigated how maternal care affectsthe free-moving wolf spider’s (Pardosa saltans) energy requirements. We described in detail their basicreproduction biology (i.e. carrying cocoon and young) and we evaluated the variation in the females’energy reserves during maternal care. Our results show that mothers guard eggs until hatching and thenguard their spiderlings for 27–30 more days. Laboratory observations indicated that spiderlings startleaving the maternal abdomen gradually 5–7 days after hatching. Females carry an egg sac (cocoon) thatcan weigh up to 77% of their post-reproduction weight and carry young that weigh 87–100% of their bodymass. Females lost weight over time despite regular food intake, while carrying cocoon and young; buttheir weights increased gradually during the dispersal of young. The contributions of proteins, glucoseand triglycerides to maintain females’ energy were calculated. Their energetic state varied duringmaternal care, in particular lipid levels declined, during the care of spiderlings when the females’ predatorybehaviour was inhibited. Our results show that the maternal care provided by P. saltans females isparticularly costly physiologically, during the 30 days following egg sac formation and development ofspiderlings, even when food is available

    Chemical signals during egg-sac care in spiders Pardosa saltans (Lycosidae)

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    National audienceIn the major part of arthropods, included arachnids, the female limits her progeny cares at the construction of an egg-sac before abandoning it.But in some species of spiders, the female stay near her egg-sac and take care of it until the young emergence. Pardosa saltans is a wanderingspider who transports her egg-sac attached to her spinnerets and takes care of it throughout the incubation period. The aim of our study is toidentify the effect of the egg-sac developmental status and the contact chemical signals perceived by the mother to start and maintain thismaternal behaviour

    Age and egg-sac loss determine maternal behaviour and locomotor activity of wolf spiders (Araneae, Lycosidae)

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    International audienceWolf spiders’ (Lycosidae) maternal behaviour includes a specific phase called “egg brooding” which consists of guarding and carrying an egg-sac throughout the incubation period. The transport of an egg-sac can restrict mothers’ exploratory and locomotor activity, in particular when foraging. The present study details the ontogeny of maternal behaviour and assesses the influence of age of egg-sac (or embryos’ developmental stage) on vagrant wolf spider Pardosa saltans females’ exploration and locomotion. We observed these spiders’ maternal behaviour in the laboratory and evaluated their locomotor activity using a digital activity recording device. Our subjects were virgin females (without egg-sac) and first time mothers (with her egg-sac) who were divided into three groups. The first group of mothers were tested on the day the egg-sac was built (day 0), and the females of the other two groups were tested 10 or 15 days after they had built their egg-sac. We evaluated the effects of the presence and the loss of egg-sac on mothers’ activity. Pardosa saltans females’ behaviour depended on mothers’ physiological state and/or age of egg-sac (developmental stage of embryos). Virgin females’ behaviour was not modified by the presence of an egg-sac in their environment. Mothers’ reactions to the presence, the loss and the recovery of their egg-sac varied during the maternal cycle. Maternal behaviour changed with age of egg-sac, but the levels of locomotor activity of mothers with egg-sacs was similar to those of virgin females. Loss of egg-sac modified the maternal behaviour and locomotor activity of all mothers; these modifications were greater on “day 15” when embryos had emerged from eggs. All mothers were able to retrieve their egg-sacs and to re-attach them to their spinnerets

    Maternal behaviour, locomotor activity and reproduction cycle of females spider Pardosa saltans (Lycosidae) with a foreign or dead egg-sac

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    National audienceChez de nombreuses espèces d’araignées la femelle limite les soins à la progéniture à la confection d’un cocon livré ensuite à lui-même. Cependant dans la majorité des familles on rencontre des espèces où la mère reste à proximité ou même en contact étroit avec son cocon : c’est le « gardiennage » du cocon. De nombreuses fonctions ont été attribuées à la présence de la mère près de son cocon, mais peu de démonstrations expérimentales existent. Parmi ces fonctions, certaines incluent la protection du cocon envers les prédateurs et les parasites, la régulation hydrique et l’ouverture du cocon afin de permettre l’émergence des jeunes. Chez des araignées errantes, comme les lycoses, les mères se déplacent sans cesse en milieu naturel en transportant leur cocon accroché à leurs filières tout au long de la phase d’incubation. Il est possible pour ces mères de perdre le cocon au cours de leur déplacement. De récentes études ont mis en évidence qu’une femelle lycose peut, après une perte de son cocon, accrocher à ses filaires le cocon d’une congénère ou un leurre. On peut, donc, se poser la question de la valeur fonctionnelle de ce « gardiennage » du cocon et des conditions d’apparition-maintien de ce comportement chez une araignée errante. Nos observations mettent en évidence chez une araignée Lycose Pardosa saltans, l’effet de l’état du cocon (embryons vivants ou morts, et cocon connu ou inconnu) qu’elle transporte sur son comportement locomoteur et maternel ainsi que sur la suite de son cycle reproducteur
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