Yersinia massiliensis (Enterobacteriales: Enterobacteriaceae) in the host Anaphes nitens (Hymenoptera: Mymaridae): first report of association with insects

Endosymbiont bacteria can affect biological parameters and reduce the effectiveness of natural enemies in controlling the target insect. The objective of this work was to identify endosymbiont bacteria in Anaphes nitens (Girault, 1928) (Hymenoptera: Mymaridae), the main natural enemy used to manage Gonipterus platensis (Marelli, 1926) (Coleoptera: Curculionidae). Genomic DNA from six A. nitens populations was extracted and polymerase chain reactions (PCR) were performed with the primers to detect endosymbiont bacteria in this insect. The PCR products were amplified, sequenced, and compared with sequences deposited in the GenBank for the bacteria identification. All A. nitens populations had the bacterium Yersinia massiliensis (Enterobacteriales: Enterobacteriaceae). This bacterium was originally described as free-living, and it is associated with and composes part of the A. nitens microbiota. This is the first report of Y. massiliensis in an insect host.

Honey Bee Larval and Adult Microbiome Life Stages Are Effectively Decoupled with Vertical Transmission Overcoming Early Life Perturbations

This work investigated host-microbiome interactions during a crucial developmental stage—the transition from larvae to adults, which is a challenge to both the insect host and its microbiome. Using the honey bee as a tractable model system, we showed that microbiome transfer after emergence overrides any variation in the larval microbiome in honey bees, indicating that larval and adult microbiome stages are effectively decoupled.

Cecropins contribute to Drosophila host defense against a subset of fungal and Gram-negative bacterial infection

Cecropins are small helical secreted peptides with antimicrobial activity that are widely distributed among insects. Genes encoding cecropins are strongly induced upon infection, pointing to their role in host-defense. In Drosophila, four cecropin genes clustered in the genome (CecA1, CecA2, CecB and CecC) are expressed upon infection downstream of the Toll and Imd pathways. In this study, we generated a short deletion ΔCecA-C removing the whole cecropin locus. Using the ΔCecA-C deficiency alone or in combination with other antimicrobial peptide (AMP) mutations, we addressed the function of cecropins in the systemic immune response. ΔCecA-C flies were viable and resisted challenge with various microbes as wild-type. However, removing ΔCecA-C in flies already lacking ten other AMP genes revealed a role for cecropins in defense against Gram-negative bacteria and fungi. Measurements of pathogen loads confirm that cecropins contribute to the control of certain Gram-negative bacteria, notably Enterobacter cloacae and Providencia heimbachae. Collectively, our work provides the first genetic demonstration of a role for cecropins in insect host defense, and confirms their in vivo activity primarily against Gram-negative bacteria and fungi. Generation of a fly line (ΔAMP14) that lacks fourteen immune inducible AMPs provides a powerful tool to address the function of these immune effectors in host-pathogen interactions and beyond.

Penetrative and non-penetrative interaction between Laboulbeniales fungi and their arthropod hosts

Laboulbeniales are a highly specialized group of fungi living only on arthropods. They have high host specificity and spend their entire life-cycle on an arthropod host. Taxonomic characters of Laboulbeniales are based on the architecture of the cells of the parenchymal thallus, i.e. the visible part of the fungus outside the host. The extent of the fungus spreading inside the host—the haustorium—remains largely unknown. The attachment to the arthropod host is fundamental to understand the fungus-animal interaction, but how this truly occurs is unclear. Recent evidences question the strictly parasitic life-style of Laboulbeniales. We used micro-computed tomography (µCT) and 3D reconstructions to visualize, for the first time, the complete structure of Laboulbeniales species in situ on their hosts. We compared the haustoriate species, Arthrorhynchus nycteribiae on an insect host to the non-haustoriate species, Rickia gigas on a millipede host. Our results confirm that some Laboulbeniales species are ectoparasitic and have a haustorial structure that penetrates the host’s cuticle, while others are ectobionts and are only firmly attached to the host’s cuticle without penetrating it. The presence and the morphology of the haustorium are important traits for Laboulbeniales evolution, and key factors for future understanding of host dependence and specificity.

Tachinobia sp. (Hymenoptera: Eulophidae) as parasitoid of Peckia Sarcodexia) lambens (Wiedemann, 1830) (Diptera: Sarcophagidae)

Insect parasitoids have an immature life stage that develops on or within a single insect host, ultimately killing the host, hence the value of parasitoids as natural enemies. This work reports the first occurrence of parasitoid Tachinobia sp. (Hymenoptera: Eulophidae) as parasitoid Peckia (Sarcodexia) lambens (Wiedemann, 1830) (Diptera: Sarcophagidae). The pupae were obtained by the flotation method. They were individually placed in gelatin capsules until the emergence of flies or their parasitoids. In November 2013, six pupae were obtained from P. (S) lambens, of which two pupae twelve specimens emerged Tachinobia sp. The percentage of parasitism was 33.3%. Most insect parasitoids only attack a particular life stage of one or several related species. The immature parasitoid develops on or within a pest, feeding on body fluids and organs, eventually leaving the host to pupate or emerging as an adult.

insectDisease: programmatic access to the Ecological Database of the World's Insect Pathogens

Curated databases of species interactions are instrumental to exploring and understanding the spatial distribution of species and their biotic interactions. In the process of conducting such projects, data development and curation efforts may give rise to a data product with utility beyond the scope of the original work, but which becomes inaccessible over time. Data describing insect host-pathogen interactions are fairly rare, and should thus be preserved and curated with appropriate metadata. Here, we introduce the insectDisease R package, a mechanism for curating, updating, and distributing data from the Ecological Database of the World's Insect Pathogens, a database of insect host-pathogen associations, including attempted inoculations and infection outcomes for insect hosts and pathogens (bacteria, fungi, nematodes, protozoans, and viruses). This dataset has been utilized for several projects since its inception, but without a well defined, curated and permanent repository, its existence and access have been limited to word-of-mouth connections. The current effort presented here aims to provide a means to preserve, augment, and disseminate the database in a documented and versioned format. This project is an example of the type of effort that will be necessary to maintain valuable databases after the original funding disappears.

Defensive Symbionts and the Evolution of Parasitoid Host Specialization

Insect host–parasitoid interactions abound in nature and are characterized by a high degree of host specialization. In addition to their behavioral and immune defenses, many host species rely on heritable bacterial endosymbionts for defense against parasitoids. Studies on aphids and flies show that resistance conferred by symbionts can be very strong and highly specific, possibly as a result of variation in symbiont-produced toxins. I argue that defensive symbionts are therefore an important source of diversifying selection, promoting the evolution of host specialization by parasitoids. This is likely to affect the structure of host–parasitoid food webs. I consider potential changes in terms of food web complexity, although the nature of these effects will also be influenced by whether maternally transmitted symbionts have some capacity for lateral transfer. This is discussed in the light of available evidence for horizontal transmission routes. Finally, I propose that defensive mutualisms other than microbial endosymbionts may also exert diversifying selection on insect parasitoids. Expected final online publication date for the Annual Review of Entomology, Volume 67 is January 2022. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.

Cross Talk between Viruses and Insect Cells Cytoskeleton

Viruses are excellent manipulators of host cellular machinery, behavior, and life cycle, with the host cell cytoskeleton being a primordial viral target. Viruses infecting insects generally enter host cells through clathrin-mediated endocytosis or membrane fusion mechanisms followed by transport of the viral particles to the corresponding replication sites. After viral replication, the viral progeny egresses toward adjacent cells and reaches the different target tissues. Throughout all these steps, actin and tubulin re-arrangements are driven by viruses. The mechanisms used by viruses to manipulate the insect host cytoskeleton are well documented in the case of alphabaculoviruses infecting Lepidoptera hosts and plant viruses infecting Hemiptera vectors, but they are not well studied in case of other insect–virus systems such as arboviruses–mosquito vectors. Here, we summarize the available knowledge on how viruses manipulate the insect host cell cytoskeleton, and we emphasize the primordial role of cytoskeleton components in insect virus motility and the need to expand the study of this interaction.

Influence of rice crop stage on the distribution of hymenopteran parasitoids of insect pests

A total of 43 insect parasitoid species belonging to fourteen families (Aphelinidae, Braconidae, Ceraphronidae, Diapriidae, Encyrtidae, Eulophidae, Eurytomidae, Ichneumonidae, Megaspilidae, Mymaridae, Platygasteridae, Proctotrupidae, Pteromalidae, Trichogrammatidae) has been documented in the rice ecosystem using yellow pan trap. The observations were made at four important stages of rice crop like early tillering, active tillering, booting and panicle development. The parasitoids were also compared with the occurrence of sixteen insect pests that were recorded simultaneously in each stage of the crop. The result revealed that, there is a significant difference in the occurrence of parasitoids according to the stage of the crop and insect host availability. This understanding help in the introduction of specific parasitoids at respective stages for effective biocontrol.

Influential Insider: Wolbachia, an Intracellular Symbiont, Manipulates Bacterial Diversity in Its Insect Host

Facultative intracellular symbionts like the α-proteobacteria Wolbachia influence their insect host phenotype but little is known about how much they affect their host microbiota. Here, we quantified the impact of Wolbachia infection on the bacterial community of the cabbage root fly Delia radicum by comparing the microbiota of Wolbachia-free and infected adult flies of both sexes. We used high-throughput DNA sequencing (Illumina MiSeq, 16S rRNA, V5-V7 region) and performed a community and a network analysis. In both sexes, Wolbachia infection significantly decreased the diversity of D. radicum bacterial communities and modified their structure and composition by reducing abundance in some taxa but increasing it in others. Infection by Wolbachia was negatively correlated to 8 bacteria genera (Erwinia was the most impacted), and positively correlated to Providencia and Serratia. We suggest that Wolbachia might antagonize Erwinia for being entomopathogenic (and potentially intracellular), but would favor Providencia and Serratia because they might protect the host against chemical plant defenses. Although they might seem prisoners in a cell, endocellular symbionts can impact the whole microbiota of their host, hence its extended phenotype, which provides them with a way to interact with the outside world.