RESUMEN
Chlorpyrifos is one of the most widely used insecticides worldwide. It has been shown to have deleterious effects on survival of nontarget insects, but its impact on behavior has received less attention. In this study, we investigated the sublethal effects of this insecticide on sexual pheromone discrimination in two Trichogramma species. In these species, sexual pheromones arrest partners belonging to the same species. This specificity is important for reproduction efficacy because interspecific matings are sterile. We used two sympatric and closely related species of Trichogramma to study how two doses (LD 20 and LD 0.1) of chlorpyrifos can alter the discrimination by males and the emission by females of pheromones from both species. When exposed to the LD 20, the males of both species showed a decrease in the discrimination of conspecific sexual pheromones. For one of the two species (T. evanescens Westwood), this decrease even led to a total annihilation of discrimination. A dose as low as the LD 0.1, inducing no apparent mortality, induced the same decrease in pheromone discrimination for T. semblidis Aurivillius males. However, no effect was observed on the discrimination by males of sexual pheromones emitted by females either exposed to an LD 20 or an LD 0.1 of chlorpyrifos. By decreasing the discrimination by males of sexual pheromones, chlorpyrifos may induce interspecific interactions and attempts at copulating that would decrease the fitness of parasitoids. The implications of these results in relation to environmental pollution, the mode of action of the insecticide and the status of natural enemy of Trichogramma are discussed.
Asunto(s)
Cloropirifos/farmacología , Insecticidas/farmacología , Mariposas Nocturnas/efectos de los fármacos , Atractivos Sexuales , Conducta Sexual Animal/efectos de los fármacos , Comunicación Animal , Animales , Conducta Apetitiva/efectos de los fármacos , Femenino , Locomoción , Masculino , Especificidad de la Especie , Pruebas de ToxicidadRESUMEN
Hymenopterous parasitoids are key species involved in the regulation of insect populations. Kairomone perception is an important step leading to host parasitization. The massive use of insecticides induces environmental pollution that can interact with the reproduction of parasitoids. In this work, we have determined the sublethal effects of two insecticides, an organophosphorus (chlorpyrifos) and a pyrethroid (deltamethrin), on the arrestment, by host kairomones, of female parasitoids surviving an LD 20 for 24 h. The behavior of the parasitoids has been recorded with a video-computerized system. The analysis of the behaviors in control conditions versus exposed to an LD 20 have shown that both insecticides significantly increased the arrestment of parasitoids by kairomones. This increase was not followed up by a modification of the kinetics of the behavior. In both control and exposed conditions, parasitoids regularly increased their residence time on the kairomone patch indicating that no saturation to kairomones had occurred. In a field situation where hosts could be scarce, this increase in arrestment could be advantageous for parasitoids by increasing their host finding.
Asunto(s)
Conducta Animal/efectos de los fármacos , Control de Insectos/métodos , Insecticidas/toxicidad , Feromonas , Avispas/efectos de los fármacos , Animales , Cloropirifos/toxicidad , Drosophila/crecimiento & desarrollo , Drosophila/parasitología , Femenino , Interacciones Huésped-Parásitos , Masculino , Nitrilos/toxicidad , Piretrinas/toxicidad , Olfato/efectos de los fármacos , Factores de Tiempo , Pruebas de Toxicidad Aguda , Avispas/fisiologíaRESUMEN
Due to the wide use of insecticides and their contribution to environmental pollution, the determination of their sublethal effects on the reproduction of parasitoids regulating pest populations is a necessity. In this work, sublethal effects of a lethal dose 20% of chlorpyrifos on the reproduction and the sex ratio of Trichogramma brassicae were assessed. The organophosphorus insecticide chlorpyrifos is one of the most used insecticides for agricultural and domestic purposes in a worldwide market. A decrease in the number of parasitized hosts was observed for females surviving the insecticide. Furthermore, while untreated females presented a very biased sex ratio in favor of daughters, the offspring of treated females surviving the insecticide presented an almost balanced sex ratio due to a decrease in the number of daughters. This decrease in sex ratio was interpreted to be resulting from a decrease in fertilized eggs due to the perturbation of nerve transmissions induced by the insecticide. These results highlight the need for considering not only the direct mortality induced by insecticides but also sublethal effects liable to modify important fitness traits involved in the dynamic of beneficial insect populations.
Asunto(s)
Cloropirifos/envenenamiento , Insecticidas/envenenamiento , Razón de Masculinidad , Avispas/fisiología , Animales , Femenino , Interacciones Huésped-Parásitos , Masculino , Avispas/efectos de los fármacosRESUMEN
Parasitoids are key species involved in the regulation of natural populations. Host parasitization is realized via some important steps in which kairomone perception is essential. Due to the wide use of insecticides and their contribution to environmental pollution, the determination of their sublethal effects on behaviors involved in the reproduction of parasitoids becomes a necessity. In this work, we analyzed the effects of a lethal dose 20% of chlorpyrifos, an organophosphorus insecticide, on the behavior of L. boulardi toward the kairomone of its host. The insecticide significantly modified the kinetics of the residence time of parasitoids on a patch marked by kairomones. Females exposed to the insecticide were less efficient in finding the kairomone patch than control females, and they tended to stay on that patch, whereas control females rapidly left it. These effects are discussed considering the mode of action of the insecticide. Because search time allocation of host is an important component for parasitism efficiency, this modification of behavior could interfere with the reproduction capacity of parasitoids. Therefore, in a context of environmental pollution, the repercussions of such sublethal effects on the population biology of insects need to be considered.
Asunto(s)
Cloropirifos/efectos adversos , Insecticidas/efectos adversos , Movimiento , Feromonas , Avispas , Animales , Conducta Animal , Femenino , Interacciones Huésped-Parásitos , Cinética , Masculino , Plantas Comestibles , OlfatoRESUMEN
Pyrethroid insecticides are widely used and lead to a sizable environmental pollution that could interfere with the population biology of insects. Trichogramma is a beneficial insect used in biological control and which natural populations contribute to the control of Lepidopterus pests. In this work, we determined the effect of a sublethal dose of deltamethrin on the sex pheromonal communication of Trichogramma. The dose used (LD 0.1) induces no detectable mortality (the theoretical mortality is only one insect over 1000) and can be a good representation of contamination by this insecticide from environmental pollution. The insecticide was shown to have opposite effects on the sex pheromonal communication of Trichogramma, depending on which sex was exposed (Delpuech, J.M., Legallet, B., Terrier, O., Fouillet, P., 1999. Chemosphere 38, 729-739). We show that, when both sexes are simultaneously exposed to the insecticide, this effect is only partially neutralized. The mean response of treated males responding to the sex pheromone from treated females is not significantly different from that of controls, but the kinetics of their response is not the same. When both sexes are treated, the response of males to the sex pheromone is lower at the beginning but their response does not decrease during time contrary to controls and becomes finally higher than that of controls. Therefore, the sublethal effect of deltamethrin in the field can be either advantageous or disadvantageous depending on the difficulty in finding females and their scarcity.
Asunto(s)
Comunicación Animal , Himenópteros/fisiología , Insecticidas/efectos adversos , Piretrinas/efectos adversos , Atractivos Sexuales , Animales , Conducta Animal/efectos de los fármacos , Relación Dosis-Respuesta a Droga , Femenino , Cinética , Masculino , NitrilosRESUMEN
Waters and colleagues recently suggested [Waters, L. C., Zelhof, A. C., Shaw, B. J. & Ch'ang, L.-Y. (1992) Proc. Natl. Acad. Sci. USA 89, 4855-4859] that an insertion of a long terminal repeat of transposable element 17.6 into the 3' untranslated region of a P450 gene leads to susceptibility to the insecticide DDT in Drosophila melanogaster. We tested this hypothesis by screening lines from around the world and found that the presence or absence of a long terminal repeat was uncorrelated with resistance in 31 strains of D. melanogaster and Drosophila simulans. Thus we must reject the hypothesis that the insertion of a long terminal repeat leads to DDT susceptibility in Drosophila.