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"Hemiptera"
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Prey Preference and Life Table of Amblyseius orientalis on Bemisia tabaci and Tetranychus cinnabarinus
Amblyseius orientalis (Ehara) (Acari: Phytoseiidae) is a native predatory mite species in China. It used to be considered as a specialist predator of spider mites. However, recent studies show it also preys on other small arthropod pests, such as Bemisia tabaci (Gennadius) (Hemiptera: Aleyrodidae). Experiments were conducted to investigate (1) prey preference of A. orientalis between Tetranychus cinnabarinus (Boisd.) (Acari: Tetranychidae) and B. tabaci, and (2) development, consumption and life table parameters of A. orientalis when reared on T. cinnabarinus, B. tabaci or a mix of both prey species. When preying on different stages of T. cinnabarinus, A. orientalis preferred protonymphs, whereas when preying on different stages of B. tabaci, A. orientalis preferred eggs. When these two most preferred stages were provided together (T. cinnabarinus protonymphs and B. tabaci eggs), A. orientalis randomly selected its prey. Amblyseius orientalis was able to complete its life cycle on B. tabaci eggs, T. cinnabarinus protonymphs, or a mix of both prey. However, its developmental duration was 53.9% and 30.0% longer when reared on B. tabaci eggs than on T. cinnabarinus and a mix of both prey, respectively. In addition, it produced only a few eggs and its intrinsic rate of increase was negative when reared on B. tabaci eggs, which indicates that B. tabaci is not sufficient to maintain A. orientalis population. The intrinsic rates of increase were 0.16 and 0.23 when A. orientalis was fed on the prey mix and T. cinnabarinus, respectively. These results suggest that although B. tabaci is a poor food resource for A. orientalis in comparison to T. cinnabarinus, A. orientalis is able to sustain its population on a mix of both prey. This predatory mite may thus be a potential biological control agent of B. tabaci when this pest co-occurs with the alternative minor pest T. cinnabarinus.
Journal Article
Does Supplementing Dipnet Samples with Activity Traps Improve the Ability to Assess the Biological Integrity of Macroinvertebrate Communities in Depressional Wetlands?
Dipnet (DN) sampling is routinely employed for macroinvertebrate bioassessments in wetlands, but it has been demonstrated that some taxa are more effectively collected with activity traps (AT). The Minnesota Pollution Control Agency (MPCA) used both DN and AT methods to evaluate the biological condition of depressional wetlands in the Mixed Wood Plains (MWP) and Temperate Prairies (TP) ecoregions. Two indices of biotic integrity (IBIs) were developed for each ecoregion using: 1) DN data alone and 2) composite samples consisting of both DN and AT data. ATs collected more active taxa such as diving beetles and swimming Hemiptera. DNs collected more taxa and collected more skating taxa and those associated with sediment or vegetation. A comparison of the effectiveness of the IBIs to evaluate biological condition indicated that the composite data had a slightly better relationship with anthropogenic disturbance and was marginally more precise. A comparison of sampling and processing costs revealed that sampling using composite samples was 130 % greater and processing was 50 % greater compared to DN-only samples. Based on the cost and limited benefit of adding AT samples, a DN-only sampling protocol is recommended to assess biological condition in depressional wetlands.
Journal Article
Two insulin receptors determine alternative wing morphs in planthoppers
Some insects have alternative wing morphs, one that is long-winged and changes habitat to follow resources, and one that is short-winged and flightless but has high fertility; here, the molecular details of this switch are revealed, with opposite effects of two insulin receptors controlling the development of different wing morphs in the planthopper.
Insect double identity is insulin-linked
Some types of insect can exist in two forms, both as long-winged morphs that can move from habitat to habitat to follow resources, and as short-winged flightless morphs with high fertility, but the molecular details of this switch have remained unclear. One species that leads this double life is the migratory brown planthopper
Nilaparvata lugens
, a serious pest in rice-growing regions of Asia. Chuan-Xi Zhang and colleagues show that long-wing versus short-wing development in
N. lugens
is controlled through the opposing effects of two insulin receptors, InR1 and InR2, on the activity of the forkhead transcription factor Foxo.
Wing polyphenism is an evolutionarily successful feature found in a wide range of insects
1
. Long-winged morphs can fly, which allows them to escape adverse habitats and track changing resources, whereas short-winged morphs are flightless, but usually possess higher fecundity than the winged morphs
1
,
2
,
3
. Studies on aphids, crickets and planthoppers have revealed that alternative wing morphs develop in response to various environmental cues
1
,
2
,
4
,
5
,
6
,
7
,
8
, and that the response to these cues may be mediated by developmental hormones, although research in this area has yielded equivocal and conflicting results about exactly which hormones are involved
4
,
8
,
9
,
10
. As it stands, the molecular mechanism underlying wing morph determination in insects has remained elusive. Here we show that two insulin receptors in the migratory brown planthopper
Nilaparvata lugens
, InR1 and InR2, have opposing roles in controlling long wing versus short wing development by regulating the activity of the forkhead transcription factor Foxo. InR1, acting via the phosphatidylinositol-3-OH kinase (PI(3)K)–protein kinase B (Akt) signalling cascade, leads to the long-winged morph if active and the short-winged morph if inactive. InR2, by contrast, functions as a negative regulator of the InR1–PI(3)K–Akt pathway: suppression of InR2 results in development of the long-winged morph. The brain-secreted ligand Ilp3 triggers development of long-winged morphs. Our findings provide the first evidence of a molecular basis for the regulation of wing polyphenism in insects, and they are also the first demonstration—to our knowledge—of binary control over alternative developmental outcomes, and thus deepen our understanding of the development and evolution of phenotypic plasticity.
Journal Article
Biotype Characterization, Developmental Profiling, Insecticide Response and Binding Property of Bemisia tabaci Chemosensory Proteins: Role of CSP in Insect Defense
Chemosensory proteins (CSPs) are believed to play a key role in the chemosensory process in insects. Sequencing genomic DNA and RNA encoding CSP1, CSP2 and CSP3 in the sweet potato whitefly Bemisia tabaci showed strong variation between B and Q biotypes. Analyzing CSP-RNA levels showed not only biotype, but also age and developmental stage-specific expression. Interestingly, applying neonicotinoid thiamethoxam insecticide using twenty-five different dose/time treatments in B and Q young adults showed that Bemisia CSP1, CSP2 and CSP3 were also differentially regulated over insecticide exposure. In our study one of the adult-specific gene (CSP1) was shown to be significantly up-regulated by the insecticide in Q, the most highly resistant form of B. tabaci. Correlatively, competitive binding assays using tryptophan fluorescence spectroscopy and molecular docking demonstrated that CSP1 protein preferentially bound to linoleic acid, while CSP2 and CSP3 proteins rather associated to another completely different type of chemical, i.e. α-pentyl-cinnamaldehyde (jasminaldehyde). This might indicate that some CSPs in whiteflies are crucial to facilitate the transport of fatty acids thus regulating some metabolic pathways of the insect immune response, while some others are tuned to much more volatile chemicals known not only for their pleasant odor scent, but also for their potent toxic insecticide activity.
Journal Article
Rapid Spread of a Bacterial Symbiont in an Invasive Whitefly Is Driven by Fitness Benefits and Female Bias
Maternally inherited bacterial symbionts of arthropods are common, yet symbiont invasions of host populations have rarely been observed. Here, we show that Rickettsia sp. nr. bellii swept into a population of an invasive agricultural pest, the sweet potato whitefly, Bemisia tabaci, in just 6 years. Compared with uninfected whiteflies, Rickettsia-infected whiteflies produced more offspring, had higher survival to adulthood, developed faster, and produced a higher proportion of daughters. The symbiont thus functions as both mutualist and reproductive manipulator. The observed increased performance and sex-ratio bias of infected whiteflies are sufficient to explain the spread of Rickettsia across the southwestern United States. Symbiont invasions such as this represent a sudden evolutionary shift for the host, with potentially large impacts on its ecology and invasiveness.
Journal Article
Molecular evolutionary trends and feeding ecology diversification in the Hemiptera, anchored by the milkweed bug genome
The Hemiptera (aphids, cicadas, and true bugs) are a key insect order, with high diversity for feeding ecology and excellent experimental tractability for molecular genetics. Building upon recent sequencing of hemipteran pests such as phloem-feeding aphids and blood-feeding bed bugs, we present the genome sequence and comparative analyses centered on the milkweed bug Oncopeltus fasciatus, a seed feeder of the family Lygaeidae.
Journal Article
Global genetic diversity and geographical distribution of Bemisia tabaci and its bacterial endosymbionts
Bemisia tabaci is one of the most threatening pests in agriculture, causing significant losses to many important crops on a global scale. The dramatic increase and availability of sequence data for B. tabaci species complex and its bacterial endosymbionts is critical for developing emerging sustainable pest management strategies which are based on pinpointing the global diversity of this important pest and its bacterial endosymbionts. To unravel the global genetic diversity of B. tabaci species complex focusing on its associated endosymbionts, along with Israeli whitefly populations collected in this study, we combined available sequences in databases, resulting in a total of 4,253 mitochondrial cytochrome oxidase I (mtCOI) sequences from 82 countries and 1,226 16S/23S rRNA endosymbiont sequences from 32 countries that were analyzed. Using Bayesian phylogenetic analysis, we identified two new B. tabaci groups within the species complex and described the global distribution of endosymbionts within this complex. Our analyses revealed complex divergence of the different endosymbiont sequences within the species complex, with overall one Hamiltonella, two Porteria (P1 and P2), two Arsenophonus (A1 and A2), two Wolbachia (super-groups O and B), four Cardinium (C1-C4) and three Rickettsia (R1-R3) groups were identified. Our comprehensive analysis provides an updated important resource for this globally important pest and its secondary symbionts, which have been a major subject for research in last three decades.
Journal Article
Wolbachia enhances ovarian development in the rice planthopper Laodelphax striatellus through elevated energy production
The endosymbiont
Wolbachia
can both benefit host nutrition and manipulate host reproduction to its own advantage. However, the mechanisms of its nutritional benefits remain unclear. We show that
Wolbachia
enhances ovarian development in the small brown planthopper
Laodelphax striatellus
by boosting energy production.
Wolbachia
-infected females have increased fecundity, accelerated ovarian development, and prolonged oviposition. Enhanced activity of mitochondrial complex I is linked to increased ATP production and the expression of energy metabolism-related genes. We further identify that
Wolbachia
-synthesized riboflavin is crucial for ATP production and ovarian development. A riboflavin transporter,
slc52a3a
, positively correlates with
Wolbachia
density and is required for normal ovarian maturation. Our findings demonstrate that
Wolbachia
-produced riboflavin drives energy production and accelerates ovarian maturation, thus improving host fecundity. This research reveals insights into symbiont-host metabolic interactions and underscores the role of nutrient delivery in symbiosis.
Wolbachia
affects host reproduction and nutrition, but the underlying mechanisms are unclear. This study suggests
Wolbachia
enhances ovarian development in
Laodelphax striatellus
via riboflavin synthesis, driving ATP production and ovarian maturation.
Journal Article
Fossils reshape the Sternorrhyncha evolutionary tree (Insecta, Hemiptera)
The Sternorrhyncha, which comprise about 18,700 described recent species, is a suborder of the Hemiptera, one of big five most diverse insect orders. In the modern fauna, these tiny phytophages comprise insects of great ecological and economic importance, like aphids (Aphidomorpha), scale insects (Coccidomorpha), whiteflies (Aleyrodomorpha) and psyllids (Psylloidea). Their evolutionary history can be traced back to the Late Carboniferous, but the early stages of their evolution and diversification is poorly understood, with two known extinct groups—Pincombeomorpha and Naibiomorpha variously placed in classifications and relationships hypotheses. Most of the recent Sternorrhyncha groups radiated rapidly during the Cretaceous. Here we report the new finding of very specialised sternorrhynchans found as inclusions in mid-Cretaceous amber from Kachin state (northern Myanmar), which represent another extinct lineage within this hemipteran suborder. These fossils, proposed to be placed in a new infraorder, are revealed to be related to whiteflies and psyllids. We present, also for the first time, the results of phylogenetic analyses covering extinct and extant lineages of the Sternorrhyncha.
Journal Article