Disruption of the Serine/Threonine Kinase Akt Gene Affects Ovarian Development and Fecundity in the Cigarette Beetle, Lasioderma serricorne.

Serine/threonine kinase Akt, an important component of the insulin signaling pathway, plays an essential role in many physiological processes. In this study, we identified and characterized an Akt gene (designated LsAkt) from the cigarette beetle, Lasioderma serricorne. LsAkt contains a 1614 bp open reading frame encoding a 537 amino acid protein that possesses a conserved pleckstrin homology domain and a serine/threonine kinase domain. The expression of LsAkt was high in pupal stages and peaked in day-4 female pupae. In adult tissues, LsAkt was highly expressed in the thorax, ovary, and midgut. The expression of LsAkt was induced by methoprene or bovine insulin in vivo, but significantly decreased by 20-hydroxyecdysone. RNA interference-mediated knockdown of LsAkt resulted in severely blocked ovarian development and reduced fecundity and hatchability. The vitellogenin (Vg) content and juvenile hormone (JH) titers of LsAkt-depletion beetles were decreased, and expressions of Vg and four JH signaling and biosynthetic genes were significantly decreased. Silencing of LsAkt reduced the amounts of glucose, glycogen, and trehalose in female adults and affected the expressions of seven key carbohydrate metabolic genes. Taken together, it is inferred that Akt implicates in L. serricorne reproduction by modification of Vg synthesis, juvenile hormone production and carbohydrate metabolism.

Diaporthe taoicola and D. siamensis, Two New Records on Citrus sinensis in China.

Two Diaporthe species isolated from fruit of Citrus sinensis in China were characterized based on morphology and multilocus phylogeny of ITS, tef1, and tub2 gene sequences. The phylogeny indicated that the two species match Diaporthe taoicola and D. siamensis. A critical examination of phenotypic characteristics confirmed the phylogenetic results. Diaporthe taoicola was morphologically characterized by producing Alpha conidia with tapering toward both ends. Meanwhile, D. siamensis produced cylindrical or ellipsoidal Alpha conidia with two oil drops. Pathogenicity tests revealed that both species were pathogenic to fruit of C. sinensis. To our knowledge, the two species were firstly reported on Citrus sinensis in China.

The complete mitochondrial genome and phylogenetic analysis of Phintella cavaleriei (Araneae: Salticidae).

The complete mitochondrial genome of Phintella cavaleriei is 14,325 bp in length, containing 13 protein-coding genes (PCGs), 22 transfer RNA genes (tRNAs), two ribosomal RNA genes, and a putative control region. The overall nucleotide composition is 35.04% A, 8.46% C, 13.41% G, and 43.09% T, with a total of A + T content of 78.13%. Ten PCGs start with typical ATN codons, two genes (cox2 and cox3) begin with TTG, and cox1 use TTA as initiation codon. Ten PCGs use usual termination codon of TAA or TAG, whereas the remaining three PCGs had an incomplete termination codon (T-). Seven tRNAs (trnY, trnC, trnG, trnN, trnH, trnP, and trnV) lacked the TΨC arm stem, while two tRNAs (trnS1 and trnS2 ) lost the dihydrouracil (DHU) arm. Phylogenetic analysis based on 13 PCGs indicated that P. cavaleriei was closely related to Cheliceroides longipalpis, and clustered within Salticidae clade.

Effects of Prey Distribution and Heterospecific Interactions on the Functional Response of Harmonia axyridis and Aphidius gifuensis to Myzus persicae.

Natural enemy guilds normally forage for prey that is patchily distributed simultaneously. Previous studies have investigated the influence of conspecific interactions and prey distribution on the functional response of natural enemies. However, little is known about how prey distribution and heterospecific interactions between natural enemies could affect their foraging efficiency. We examined the effects of prey distribution (aggregate and uniform) and heterospecific interactions on the functional response of a predator, Harmonia axyridis (Pallas) (Coleoptera: Coccinellidae) and a parasitoid, Aphidius gifuensis Ashmead (Hymenoptera: Braconidae) to the green peach aphid, Myzus persicae (Sulzer) (Hemiptera: Aphididae). Type II functional responses were observed in all experiments. Functional response curves of single H. axyridis or A. gifuensis were higher in the aggregate treatment than in the uniform treatment when aphid densities were between 40-180 or 70-170, respectively. When comparing between aggregate and uniform treatments with the heterospecific enemy occurrence, no differences were found in the parasitism efficiency of A. gifuensis, while H. axyridis consumed more aphids in the aggregate treatment than in the uniform treatment when aphid densities were between 50-230. The functional response of individual H. axyridis was not affected by A. gifuensis under two aphid distributions. However, the functional response of a single A. gifuensis and the treatment when A. gifuensis concurrently with H. axyridis overlapped in uniform treatment of above approximately 150 aphids. Our results indicate that the predation rate of H. axyridis was affected by aphid distribution, but was not affected by heterospecific interactions. The parasitism rate of A. gifuensis was affected by aphid distribution, and by heterospecific interactions in both the aggregate and uniform treatments. Thus, to optimize the management efficiency of M. persicae, the combined use of H. axyridis and A. gifuensis should be considered when M. persicae is nearly uniformly distributed under relatively high density.

Effects of mummy consumption on fitness and oviposition site selection on Harmonia axyridis.

Intraguild predation (IGP) has been commonly reported between predators and parasitoids used as biological control agents as predators consuming parasitoids within their hosts. However, the effect of parasitoid-mummy consumption on the fitness of the predator and subsequent oviposition site selection have not been well studied. In our study, we conducted two laboratory experiments to examine the influence of Aphidius gifuensis Ashmead (Hymenoptera: Braconidae) mummies as prey on fitness and subsequently oviposition site selection of Harmonia axyridis (Pallas) (Coleoptera: Coccinellidae). Results indicate that when H. axyridis was reared on A. gifuensis mummies only, its larval development was prolonged, and body weight of the 4th instar larvae and newly emerged adults, and fecundity decreased. Moreover, H. axyridis did not exhibit oviposition preference on plants infested with unparasitized aphids or aphids parasitized for shorter than 9 days. However, compared with plants with mummies (parasitized ≥9 days), H. axyridis laid more eggs on plants with unparasitized aphids. In contrast, H. axyridis previously fed with A. gifuensis mummies did not show a significant oviposition preference between plants with unparasitized aphids and those with mummies (parasitized ≥9 days). Overall, our results suggest that mummy consumption reduced the fitness of H. axyridis. Although H. axyridis avoided laying eggs on plants with A. gifuensis mummies, prior feeding experience on A. gifuensis mummies could alter the oviposition site preference. Thus, in biological control practice, prior feeding experience of H. axyridis should be carefully considered for reduction of IGP and increase of fitness of H. axyridis on A. gifuensis.

[Geostatistical analysis on distribution dynamics of Myzus persicae (Sulzer) in flue-cured tobacco field].

Abstract: Myzus persicae belonging to Aphididae, Hemiptera, is an important migratory pest in tobacco field. As nymph and adult, it sucks the juice, breeds the mildew stains disease, spreads tobacco virus diseases and causes huge losses to the yield and quality. The distribution pattern and dynamics of winged and wingless aphids in the field were investigated from the transplanting of tobacco to the harvesting stage of mid-place tobacco leaves in Enshi, Hubei. The semivariable function characteristics were analyzed by geostatistical method, and the field migration pattern were simulated. The results showed that the population dynamics of winged aphids in Enshi were of bimodal curve, with two peaks at 3 weeks after transplanting and 2 weeks after multi-topping of tobacco leaves, and there were five-step process such as random, aggregation, random, aggregation and random. The population dynamics of wingless peach aphids were of single-peak curve, getting its peak before multi-topping, and had random, aggregation, random three-step process. Human factors and the hosts had considerable effects on the population density. Spatial distribution simulation-interpolation-figure could clearly reflect the dynamics of tobacco aphids. Combined with the Pearson correlation analysis, we found that the population density was low and highly concentrated as winged type in the immigration period, which was the key period for the management of peach aphids.

[Geostatistical analysis on distribution pattern of the tobacco budworm larva in Enshi, Hubei, China].

Tobacco budworm (Helicoverpa assulta) larvae feed on tobacco leaves (Nicotiana sp.), resulting in significant loss in tobacco production. Geostatistical method was used to analyze H. assulta spatial patterns and dynamics in this paper. The results showed that, H. assulta larvae appeared 40 days after the tobacco plants transplanting, and reached its peak at the early-mature period. The nested spherical and exponential model was the major model for tobacco budworm larva in the field, suggesting its aggregated distribution. The spatial variability C/(C0 + C) was larger than 0.75, which indicated H. assulta larva had wider structural variation and narrower random variation. There was a massive migration of tobacco budworm larva in the fast-growing stage of tobacco. Its quantity became stable after that, especially at the mature stage of tobacco.