Selection for resistance to methoxyfenozide and 20-hydroxyecdysone in cells of the beet armyworm Spodoptera exigua

In this report with an ecdysteroid-responsive cell line of the beet armyworm, Spodoptera exigua (Se4) selection for resistance against methoxyfenozide and the insect moulting hormone (20-hydroxyecdysone, 20E) was carried out to analyze the resulting resistant cells in order to elucidate possible mechanisms of resistance towards these compounds. From these cultures, five methoxyfenozide- and four 20E-resistant subclones were selected starting from 0.1 nM methoxyfenozide up to 100 mu M and from 10 nM 20E up to 100 mu M, respectively. To date, the selected cells kept their loss of susceptibility for 100 PM. Here we evaluated two processes known to be important in insecticide resistance, namely metabolism and pharmacokinetics, in the selected methoxyfenozide- and 20E-resistant subclones. Synergism experiments with piperonyl butoxide, S,S,S-tributyl phosphorotrithioate, and diethyl maleate, which are respective inhibitors of monooxygenases, esterases, and gluthation-S-transferases, did not affect the level of the resistance. To check the possible existence of active transport in the resistant cells, we used ouabain, an inhibitor of active membrane transport. In parallel, the absorption profile was studied in resistant and susceptible cells with use of C-14-methoxyfenozide. Interestingly, resistant subclones showed cross-resistance towards methoxyfenozide and 20E. The resistance was irreversible even after the compounds were removed from the medium

Inheritance of resistance to imidacloprid and chlorpyrifos in greenhouse whitefly, Trialeurodes vaporariorum

Inheritance of resistance of the greenhouse whitefly, Trialeurodes vaporariorum Westwood (Hemiptera: Aleyrodidae), to imidacloprid and chlorpyrifos was studied. In this study, the Filistan population (FL) and the Fardis population (FR) were used as resistant and susceptible parents, which collected from Varamin and Karaj cities, respectively. The resistance ratios (RR) of FL population obtained for imidacloprid and chlorpyrifos were about 13.62 and 14.91-fold, respectively. LC50 values of chlorpyrifos on F1 (R♂×S♀) and Fʹ1 (R♀×S♂) crosses did not show any significant difference. Therefore, the resistance of T. vaporariorum to chlorpyrifos is autosomal. Also, the values of dominance factor indicated that the resistance of greenhouse whitefly to chlorpyrifos is inherited in incomplete recessive form. In addition, by using the expected mortality of the F2 generation with the generations resulting from crossing, it was determined that the resistance of T. vaporariorum to chlorpyrifos is polygenic. The results obtained from imidacloprid bioassays showed that the resistance of the greenhouse whitefly to this compound is autosomal, incompletely dominant, and polygenic. The present study suggests that according to the knowledge of the inheritance of resistance of T. vaporariorum, it is possible to delay the spread of resistance by using timely, correct, intermittent, and mixed insecticides

Plasticity in the gut microbial community and uptake of Enterobacteriaceae (Gammaproteobacteria) in Bombus terrestris bumblebees' nests when reared indoors and moved to an outdoor environment

Bombus nests consisting of one queen, brood, and worker adults, are produced indoors for biological pollination in agriculture. In this study, we investigated the gut microbial community in workers of Bombus terrestris when the environment is stable (indoors) or variable (outdoors). When nests were reared indoors under standardized conditions, we identified a small gut microbial community consisting of Neisseriaceae, Orbaceae, Lactobacillaceae, and Bifidobacteriaceae, and the age of bumblebee nests and workers did not affect the alpha and beta diversity, confirming a stable microbiota. Secondly, when indoor-reared nests were moved to outdoors, we observed a major shift in the microbial community, especially in the newborn workers fully developed in the outdoor conditions, with a significant colonization of Enterobacteriaceae. Our new findings are discussed in relation to host-associated core and non-core bacteria in bumblebees including possible implications for host functioning

Lack of population genetic structure in the marine nematodes Ptycholaimellus pandispiculatus and Terschellingia longicaudata in beaches of the Persian Gulf, Iran

We investigated genetic diversity and population genetic structure of two common benthic nematode species, Ptycholaimellus pandispiculatus and Terschellingia longicaudata, from sandy beaches in the area of Bandar Abbas (Iran), Persian Gulf. Based upon partial mitochondrial cytochrome oxidase c subunit 1 (COI) gene data, 17 and two haplotypes were found for P.pandispiculatus and Te.longicaudata, respectively. Analysis of molecular variance did not reveal a significant population genetic structure for either species. The absence of genetic structuring indicates substantial dispersal and gene flow in our study area. To assess the species structure of Te.longicaudata at a larger geographic scale, we compared 18S rDNA and COI sequences from Iran and the Scheldt Estuary in The Netherlands to ascertain whether they truly belong to the same species. Our data confirmed previous studies that Te.longicaudata likely constitutes a complex of multiple cryptic species, with one of these species having a (near) cosmopolitan distribution