Search

The importance of natural enemies as the foundation of integrated pest management (IPM) is widely accepted, but few studies conduct the manipulative field experiments necessary to directly quantify their impact on pest populations in this context. This is particularly true for predators. Studying arthropod predator-prey interactions is inherently difficult: prey items are often completely consumed, individual predator-prey interactions are ephemeral (rendering their detection difficult) and the typically fluid or soft-bodied meals cannot be easily identified visually within predator guts. Serological techniques have long been used in arthropod predator gut-contents analysis, and current enzyme linked immunosorbent assays (ELISA) are highly specific and sensitive. Recently, polymerase chain reaction (PCR) methods for gut-contents analysis have developed rapidly and they now dominate the diagnostic methods used for gut-contents analysis in field-based research. This work has identified trophic linkages within food webs, determined predator diet breadth and preference, demonstrated the importance of cannibalism and intraguild predation within and between certain taxa, and confirmed the benefits (predator persistence) and potential disadvantages (reduced feeding on pest species) of the availability of alternative nonpest prey. Despite considerable efforts to calibrate gut-contents assays, these methods remain qualitative. Available techniques for predator gut-contents analysis can provide rapid, accurate, cost-effective identification of predation events. As such, they perfectly compliment the ecological methods developed to directly assess predator impacts on prey populations but which are imperfect at identifying the key predators. These diagnostic methods for gut-contents analysis are underexploited in agricultural research and they are almost never applied in unison with the critical field experiments to measure predator impact. This paper stresses the need for a combined approach and suggests a framework that would make this possible, so that appropriate natural enemies can be targeted in conservation biological control., (© 2014 Institute of Zoology, Chinese Academy of Sciences.)

A new species of entomopathogenic nematode (EPN) named Steinernema balochiense n. sp. belonging to the family Steinernematidae was isolated from Psidium guajava L., rhizophere soil samples of Balochistan, Pakistan. This new species belongs to the carpocapsae group. The new species can be separated from other described species by morphological and morphometrics characteristics as well as DNA sequence polymorphisms. This new nematode species is morphologically characterized by features of infective juveniles (IJ) and males. For the IJ average body length was (455; 415-528) µm, distance from anterior end to excretory pore (35; 32-38) µm, pharynx length (90; 85-98) µm, tail length (44.3; 40-51) µm, D% and E% values (39; 36-44) and (80; 70-92), respectively. For male specimens, the diagnostic characters included total body length (1330; 1135-1632) µm, gubernaculum length (44.4; 40-47) µm, D% (43.8; 40-51) and ratio of GS (63.8; 53-75). Morphological diagnostic traits for new species include the presence of a funnel shaped gubernaculum at the proximal end. S. balochiense n. sp. differs from infective stage juveniles of closest species S. nepalense by having 6 ridges vs 7 ridges in the lateral field. Molecular phylogenetic trees based on sequence of ITS-rDNA, D2D3 regions and the mitochondrial 12S rRNA gene supports the description of this nematode isolate as a new species.

Within Metazoa, it has been proposed that as many as two-thirds of all species are parasitic. This propensity towards parasitism is also reflected within insects, where several lineages independently evolved a parasitic lifestyle. Parasitic behaviour ranges from parasitic habits in the strict sense, but also includes parasitoid, phoretic or kleptoparasitic behaviour. Numerous insects are also the host for other parasitic insects or metazoans. Insects can also serve as vectors for numerous metazoan, protistan, bacterial and viral diseases. The fossil record can report this behaviour with direct (parasite associated with its host) or indirect evidence (insect with parasitic larva, isolated parasitic insect, pathological changes of host). The high abundance of parasitism in the fossil record of insects can reveal important aspects of parasitic lifestyles in various evolutionary lineages. For a comprehensive view on fossil parasitic insects, we discuss here different aspects, including phylogenetic systematics, functional morphology and a direct comparison of fossil and extant species., (Copyright © 2015 Elsevier Ltd. All rights reserved.)

Natural enemies often cause significant levels of mortality for their prey and thus can be important agents of natural selection. It follows, then, that selection should favor traits that enable organisms to escape from their natural enemies into "enemy-free space" (EFS). Natural selection for EFS was originally proposed as a general force in structuring ecological communities, but more recently has become conceptually narrow and is typically only invoked when studying the evolutionary ecology of host plant use by specialized insect herbivores. By confining the application of EFS to specialist herbivores, its potential value to community and evolutionary ecology has been marginalized. As a first step toward exploring the potential explanatory power of EFS in structuring ecological niches of higher trophic-level organisms, we consider host use by parasitoids. Here, we present three distinct mechanisms from our studies of caterpillar host-parasitoid interactions suggesting that parasitoids may be under selection to exploit traits of their hosts and the plants on which those hosts feed to garner EFS for their developing offspring. The neglect of EFS as a top-down selective force on host use by parasitoids may be a serious limitation to basic and applied ecology, given the great diversity of parasitoids and their significance in controlling herbivore populations in both natural and managed ecosystems. Parasitoids and other mesopredators represent excellent candidates for further developments of EFS theory and testing of its broader importance.

Background: Ecological studies routinely show genotype-genotype interactions between insects and their parasites. The mechanisms behind these interactions are not clearly understood. Using the bumblebee Bombus terrestris/trypanosome Crithidia bombi model system (two bumblebee colonies by two Crithidia strains), we have carried out a transcriptome-wide analysis of gene expression and alternative splicing in bees during C. bombi infection. We have performed four analyses, 1) comparing gene expression in infected and non-infected bees 24 hours after infection by Crithidia bombi, 2) comparing expression at 24 and 48 hours after C. bombi infection, 3) determining the differential gene expression associated with the bumblebee-Crithidia genotype-genotype interaction at 24 hours after infection and 4) determining the alternative splicing associated with the bumblebee-Crithidia genotype-genotype interaction at 24 hours post infection., Results: We found a large number of genes differentially regulated related to numerous canonical immune pathways. These genes include receptors, signaling pathways and effectors. We discovered a possible interaction between the peritrophic membrane and the insect immune system in defense against Crithidia. Most interestingly, we found differential expression and alternative splicing of immunoglobulin related genes (Dscam and Twitchin) are associated with the genotype-genotype interactions of the given bumblebee colony and Crithidia strain., Conclusions: In this paper we have shown that the expression and alternative splicing of immune genes is associated with specific interactions between different host and parasite genotypes in this bumblebee/trypanosome model.

A meta-analysis of the effects of vector saliva on the immune response and progression of vector-transmitted disease, specifically with regard to pathology, infection level, and host cytokine levels was conducted. Infection in the absence or presence of saliva in naïve mice was compared. In addition, infection in mice pre-exposed to uninfected vector saliva was compared to infection in unexposed mice. To control for differences in vector and pathogen species, mouse strain, and experimental design, a random effects model was used to compare the ratio of the natural log of the experimental to the control means of the studies. Saliva was demonstrated to enhance pathology, infection level, and the production of Th2 cytokines (IL-4 and IL-10) in naïve mice. This effect was observed across vector/pathogen pairings, whether natural or unnatural, and with single salivary proteins used as a proxy for whole saliva. Saliva pre-exposure was determined to result in less severe leishmaniasis pathology when compared with unexposed mice infected either in the presence or absence of sand fly saliva. The results of further analyses were not significant, but demonstrated trends toward protection and IFN-γ elevation for pre-exposed mice.

Host orientation is the most important step in host-searching nematodes; however, information on direct cues from hosts to evoke this behaviour is limited. Caenorhabditis japonica establishes a species-specific phoresy with Parastrachia japonensis. Dauer larvae (DL), the non-feeding and phoretic stage of C. japonica, are predominantly found on female phoretic hosts, but the mechanisms underlying the establishment of this phoresy remain unknown. To determine whether C. japonica DL are able to recognize and orient themselves to a host using a volatile cue from the host, we developed a Y-tube olfactory assay system in which C. japonica DL were significantly attracted to the air from P. japonensis but not to the air from three other insects or to CO2. These results demonstrated that C. japonica DL utilize volatiles for host recognition and orientation and that the presence of a specific volatile kairomone released by the host attracts C. japonica DL., (© 2014. Published by The Company of Biologists Ltd.)

The life cycle of the African trypanosome Trypanosoma brucei, is characterised by a transition between insect and mammalian hosts representing very different environments that present the parasite with very different challenges. These challenges are met by the expression of life-cycle stage-specific cohorts of proteins, which function in systems such as metabolism and immune evasion. These life-cycle transitions are also accompanied by morphological rearrangements orchestrated by microtubule dynamics and associated proteins of the subpellicular microtubule array. Here we employed a gel-based comparative proteomic technique, Difference Gel Electrophoresis, to identify cytoskeletal proteins that are expressed differentially in mammalian infective and insect form trypanosomes. From this analysis we identified a pair of novel, paralogous proteins, one of which is expressed in the procyclic form and the other in the bloodstream form. We show that these proteins, CAP51 and CAP51V, localise to the subpellicular corset of microtubules and are essential for correct organisation of the cytoskeleton and successful cytokinesis in their respective life cycle stages. We demonstrate for the first time redundancy of function between life-cycle stage specific paralogous sets in the cytoskeleton and reveal modification of cytoskeletal components in situ prior to their removal during differentiation from the bloodstream form to the insect form. These specific results emphasise a more generic concept that the trypanosome genome encodes a cohort of cytoskeletal components that are present in at least two forms with life-cycle stage-specific expression.

Entomopathogenic nematodes (EPN) are lethal parasites of insects, used as biocontrol agents. The objectives of this work were to survey the presence of EPN in continental Portugal and to characterize the different species. Of the 791 soil samples collected throughout continental Portugal, 53 were positive for EPN. Steinernema feltiae and Heterorhabditis bacteriophora were the two most abundant species. Analysis of EPN geographical distribution revealed an association between nematode species and vegetation type. Heterorhabditis bacteriophora was mostly found in the Alentejo region while S. feltiae was present in land occupied by agriculture with natural vegetation, broadleaved forest, mixed forest and transitional woodland-shrub, agro-forestry areas, complex cultivated patterns and non-irrigated arable land. Although no clear association was found between species and soil type, S. feltiae was typically recovered from cambisols and H. bacteriophora was more abundant in lithosols. Sequencing of the internal transcribed spacer (ITS) region indicated that S. feltiae was the most abundant species, followed by H. bacteriophora. Steinernema intermedium and S. kraussei were each isolated from one site and Steinernema sp. from two sites. Phylogenetic analyses of ITS, D2D3 expansion region of the 28S rRNA gene, as well as mitochondrial cytochrome c oxidase subunit I (COXI) and cytochrome b (cytb) genes, was performed to evaluate the genetic diversity of S. feltiae and H. bacteriophora. No significant genetic diversity was found among H. bacteriophora isolates. However, COXI seems to be the best marker to study genetic diversity of S. feltiae. This survey contributes to the understanding of EPN distribution in Europe.

The life cycle of four Steinernema species was observed in 4 insect micro-insect host species (less than 5mm long). Several parameters were measured: sex ratio of invading nematodes, percentages of host infection and offspring production, penetration rate of infective juveniles per insect and number of new generation of infective juveniles. All parameters varied among nematode species, micro-host species and application rates. All Steinernema species were capable to invade micro-insect hosts, however, invasion decreased as insect size decreased and as nematode species size increased. None of the nematode species achieved 100% mortality in the micro-hosts. Due to size differences in the nematode species, Steinernema glaseri was less capable of completing its life cycle and unable to invade smaller hosts whereas S. riobrave completed its life cycle in smaller hosts more frequently. The number of invading nematodes and the number of offspring produced had the same levels regardless of the nematode application rates, those results showed a maximum top in the number of individuals per micro-insect host. The offspring production in thrips species was only possible by endotokia matricida in S. riobrave. The sex of the invader nematodes also impeded the life cycle of S. affine because males colonized the entire body of the micro-insect host leaving no room for female invasion. The size of the host plays an irrefutable role in limiting the development of nematodes and it appears improbable that an entomopathogenic nematode population can persist in the soil without the presence of bigger insects., (Copyright © 2014 Elsevier Inc. All rights reserved.)

Pseudomonas taiwanensis is a broad-host-range entomopathogenic bacterium that exhibits insecticidal activity toward agricultural pests Plutella xylostella, Spodoptera exigua, Spodoptera litura, Trichoplusia ni and Drosophila melanogaster. Oral infection with different concentrations (OD = 0.5 to 2) of wild-type P. taiwanensis resulted in insect mortality rates that were not significantly different (92.7%, 96.4% and 94.5%). The TccC protein, a component of the toxin complex (Tc), plays an essential role in the insecticidal activity of P. taiwanensis. The ΔtccC mutant strain of P. taiwanensis, which has a knockout mutation in the tccC gene, only induced 42.2% mortality in P. xylostella, even at a high bacterial dose (OD = 2.0). TccC protein was cleaved into two fragments, an N-terminal fragment containing an Rhs-like domain and a C-terminal fragment containing a Glt symporter domain and a TraT domain, which might contribute to antioxidative stress activity and defense against macrophagosis, respectively. Interestingly, the primary structure of the C-terminal region of TccC in P. taiwanensis is unique among pathogens. Membrane localization of the C-terminal fragment of TccC was proven by flow cytometry. Sonicated pellets of P. taiwanensis ΔtccC strain had lower toxicity against the Sf9 insect cell line and P. xylostella larvae than the wild type. We also found that infection of Sf9 and LD652Y-5d cell lines with P. taiwanensis induced apoptotic cell death. Further, natural oral infection by P. taiwanensis triggered expression of host programmed cell death-related genes JNK-2 and caspase-3.

Increasing evidence indicates that the Trypanosoma brucei flagellum (synonymous with cilium) plays important roles in host-parasite interactions. Several studies have identified virulence factors and signaling proteins in the flagellar membrane of bloodstream-stage T. brucei, but less is known about flagellar membrane proteins in procyclic, insect-stage parasites. Here we report on the identification of several receptor-type flagellar adenylate cyclases (ACs) that are specifically upregulated in procyclic T. brucei parasites. Identification of insect stage-specific ACs is novel, as previously studied ACs were constitutively expressed or confined to bloodstream-stage parasites. We show that procyclic stage-specific ACs are glycosylated, surface-exposed proteins that dimerize and possess catalytic activity. We used gene-specific tags to examine the distribution of individual AC isoforms. All ACs examined localized to the flagellum. Notably, however, while some ACs were distributed along the length of the flagellum, others specifically localized to the flagellum tip. These are the first transmembrane domain proteins to be localized specifically at the flagellum tip in T. brucei, emphasizing that the flagellum membrane is organized into specific subdomains. Deletion analysis reveals that C-terminal sequences are critical for targeting ACs to the flagellum, and sequence comparisons suggest that differential subflagellar localization might be specified by isoform-specific C termini. Our combined results suggest insect stage-specific roles for a subset of flagellar adenylate cyclases and support a microdomain model for flagellar cyclic AMP (cAMP) signaling in T. brucei. In this model, cAMP production is compartmentalized through differential localization of individual ACs, thereby allowing diverse cellular responses to be controlled by a common signaling molecule., (Copyright © 2014, American Society for Microbiology. All Rights Reserved.)

The many ways parasites can impact their host species have been the focus of intense study using a range of approaches. A particularly promising but under-used method in this context is experimental evolution, because it allows targeted manipulation of known populations exposed to contrasting conditions. The strong potential of applying this method to the study of insect hosts and their associated parasites is demonstrated by the few available long-term experiments where insects have been exposed to parasites. In this review, we summarize these studies, which have delivered valuable insights into the evolution of resistance in response to parasite pressure, the underlying mechanisms, as well as correlated genetic responses. We further assess findings from relevant artificial selection studies in the interrelated contexts of immunity, life history, and reproduction. In addition, we discuss a number of well-studied Tribolium castaneum-Nosema whitei coevolution experiments in more detail and provide suggestions for research. Specifically, we suggest that future experiments should also be performed using nonmodel hosts and should incorporate contrasting experimental conditions, such as population sizes or environments. Finally, we expect that adding a third partner, for example, a second parasite or symbiont, to a host-parasite system could strongly impact (co)evolutionary dynamics., (© 2013 Institute of Zoology, Chinese Academy of Sciences.)

Entomopathogenic nematodes (a.k.a. EPN) represent a group of soil-inhabiting nematodes that parasitize a wide range of insects. These nematodes belong to two families: Steinernematidae and Heterorhabditidae. Until now, more than 70 species have been described in the Steinernematidae and there are about 20 species in the Heterorhabditidae. The nematodes have a mutualistic partnership with Enterobacteriaceae bacteria and together they act as a potent insecticidal complex that kills a wide range of insect species. Herein, we focus on the most common techniques considered for collecting EPN from soil. The second part of this presentation focuses on the insect-baiting technique, a widely used approach for the isolation of EPN from soil samples, and the modified White trap technique which is used for the recovery of these nematodes from infected insects. These methods and techniques are key steps for the successful establishment of EPN cultures in the laboratory and also form the basis for other bioassays that consider these nematodes as model organisms for research in other biological disciplines. The techniques shown in this presentation correspond to those performed and/or designed by members of S. P. Stock laboratory as well as those described by various authors.

The bacterial symbionts SF41T and SF783 were isolated from populations of the insect pathogenic nematode Heterorhabditis zealandica collected in South Africa. Both strains were closely related to strain Q614 isolated from a population of Heterorhabditis sp. collected from soil in Australia in the 1980s. Sequence analysis based on a multigene approach, DNA-DNA hybridization data and phenotypic traits showed that strains SF41T, SF783 and Q614 belong to the same species of the genus Photorhabdus with Photorhabdus temperata subsp. cinerea as the most closely related taxon (DNA-DNA hybridization value of 68%). Moreover, the phylogenetic position of Photorhabdus temperata subsp. cinerea DSM 19724T initially determined using the gyrB sequences, was reconsidered in the light of the data obtained by our multigene approach and DNA-DNA hybridization experiments. Strains SF41T, SF783 and Q614 represent a novel species of the genus Photorhabdus, for which the name Photorhabdus heterorhabditis sp. nov. is proposed (type strain SF41T=ATCC BAA-2479T=DSM 25263T).

A new steinernematid nematode, herein described as Steinernema poinari sp. n., was recovered by baiting soil samples with the last instar wax moth larvae Galleria mellonella in three localities of southwest Bohemia, Czech Republic. Morphological and molecular data confirmed this nematode as a new species which belongs to the affine/intermedium group. S. poinari sp. n. was characterized by male, female and infective juvenile morphological observations. Male spicules are robust with a pointed tip, SW% = 109 (98-123) and GS% = 70 (58-87). The tail terminus of the first generation have a papillated mucron, whereas in the second generation a short filamentous mucron sometimes develops. Females of the first generation have a moderately protruding vulva, postanal swelling absent or slightly developed. Second generation females have a long filamentous mucron on the tail tip. Infective juvenile have a body length of 768 µm, lateral field formula 2, 5, 6, 5, 2, 1, ratio D% of 46 (40-55), E% of 84 (76-95) and H% of 50 (43-56). The new species was characterized by sequences of ITS and D2D3 regions of ribosomal DNA. S. poinari sp. n. can also be separated from S. affine and S. intermedium by cross-breeding tests.

Movement behavior of foraging animals is critical to the determination of their spatial ecology and success in exploiting resources. Individuals sometimes gain advantages by foraging in groups to increase their efficiency in garnering these resources. Group movement behavior has been studied in various vertebrates. In this study we explored the propensity for innate group movement behavior among insect parasitic nematodes. Given that entomopathogenic nematodes benefit from group attack and infection, we hypothesised that the populations would tend to move in aggregate in the absence of extrinsic cues. Movement patterns of entomopathogenic nematodes in sand were investigated when nematodes were applied to a specific locus or when the nematodes emerged naturally from infected insect hosts; six nematode species in two genera were tested (Heterorhabditis bacteriophora, Heterorhabditis indica, Steinernema carpocapsae, Steinernema feltiae, Steinernema glaseri and Steinernema riobrave). Nematodes were applied in aqueous suspension via filter paper discs or in infected insect host cadavers (to mimic emergence in nature). We discovered that nematode dispersal resulted in an aggregated pattern rather than a random or uniform distribution; the only exception was S. glaseri when emerging directly from infected hosts. The group movement may have been continuous from the point of origin, or it may have been triggered by a propensity to aggregate after a short period of random movement. To our knowledge, this is the first report of group movement behavior in parasitic nematodes in the absence of external stimuli (e.g., without an insect or other apparent biotic or abiotic cue). These findings have implications for nematode spatial distribution and suggest that group behavior is involved in nematode foraging., (Published by Elsevier Ltd.)

Invasive plants can disrupt a range of trophic interactions in native communities. As a novel resource they can affect the performance of native insect herbivores and their natural enemies such as parasitoids and predators, and this can lead to host shifts of these herbivores and natural enemies. Through the release of volatile compounds, and by changing the chemical complexity of the habitat, invasive plants can also affect the behavior of native insects such as herbivores, parasitoids, and pollinators. Studies that compare insects on related native and invasive plants in invaded habitats show that the abundance of insect herbivores is often lower on invasive plants, but that damage levels are similar. The impact of invasive plants on the population dynamics of resident insect species has been rarely examined, but invasive plants can influence the spatial and temporal dynamics of native insect (meta)populations and communities, ultimately leading to changes at the landscape level.

Investigations were undertaken using light and transmission electron microscopy to clearly delineate the morphology of the cercomer, i.e. the protective envelopes and tail appendage, in cysticercoids of Microsomacanthus paraparvula, which develop in the haemocoel of the caddisworm Grensia praeterita (Insecta: Trichoptera). Two protective envelopes, the exocyst and endocyst, were identified. The non-cellular exocyst is found to consist of granular material and of thin, dense membrane-like layers, which are located parallel to each other. The exocyst of the mature metacestode tightly adjoins the outer surface of the endocyst, containing prospective parts (the scolex and the neck), except for the areas at its poles. A long tail appendage is located outside the exocyst. Evidence was found to indicate the existence of active synthetic processes occurring in the tail appendage. Non-cellular exocysts are widely distributed within metacestodes of the families Hymenolepididae and Dilepididae, and, presumably, are formed by means of glandular secretions from the oncosphere, given the early appearance of non-cellular exocysts in ontogeny.

Two novel microsporidia infecting the fat body tissues in larvae of two hosts, Halesus digitatus and Micropterna sequax (Trichoptera, Limnephilidae), were investigated using light and electron microscopy and rDNA sequence analyses. The molecular and morphological characters of these isolates warrant creation of a new microsporidian genus, Zelenkaia gen. n., with two species, one named herein. Developmental stages of Zelenkaia spp. have single nuclei. In sporogony, a plasmodium with four nuclei gives rise by rosette-like budding to two pairs of uninucleate sporoblasts, each within a thin-walled, subpersistent sporophorous vesicle. Sporoblasts and mature spores adhere temporary together, forming doublets oriented in parallel, within the sporophorous vesicle. Spores are long-oval and uninucleate, and those of the type species Z. trichopterae measure 10.3×3.5μm and have 24-25 polar filament coils. Phylogenetic analysis based on rDNA places Zelenkaia spp. within the aquatic clade of microsporidia and, more specifically, in the clade containing some microporidia from amphipod hosts., (Copyright © 2013 Elsevier Inc. All rights reserved.)

Research on hedgerow design for supporting communities of natural enemies for biological control lags behind farmer innovation in California, where assemblages of perennial plant species have been used on crop field margins in the last decade. We compared natural enemy to pest ratios between fields with hedgerows and fields with weedy margins by sampling beneficial insects and key pests of vegetables on sticky cards. We used biweekly vacuum samples to measure the distribution of key insect taxa among native perennial plant species with respect to the timing and intensity of bloom. Sticky cards indicated a trend that field margins with hedgerows support a higher ratio of natural enemies to pests compared with weedy borders. Hedgerow plant species hosted different relative densities of a generally overlapping insect community, and the timing and intensity of bloom only explained a small proportion of the variation in insect abundance at plant species and among hedgerows, with the exception of Orius spp. on Achillea millefolium L. and Baccharis pilularis De Candolle. Indicator Species Analysis showed an affinity of parasitic wasps, especially in the super-family Chalcidoidea, for B. pilularis whether or not it was in flower. A. millefolium was attractive to predatory and herbivorous homopterans; Heteromeles arbutifolia (Lindley) Roemer and B. pilularis to Diabrotica undecimpunctata undecimpunctata Mannerheim; and Rhamnus californica Eschsch to Hemerobiidae. Perennial hedgerows can be designed through species selection to support particular beneficial insect taxa, but plant resources beyond floral availability may be critical in providing structural refuges, alternative prey, and other attractive qualities that are often overlooked.

Steinernema carpocapsae is an entomopathogenic nematode widely used for the control of insect pests due to its virulence, which is mainly attributed to the ability the parasitic stage has to overcome insect defences. To identify the mechanisms underlying such a characteristic, we studied a novel serpin-like inhibitor (sc-srp-6) that was detected in a transcriptome analysis. Recombinant Sc-SRP-6 produced in Escherichia coli had a native fold of serpins belonging to the α-1-peptidase family and exhibited inhibitory activity against trypsin and α-chymotrypsin with Ki of 0.42 × 10(-7) M and 1.22 × 10(-7) M, respectively. Functional analysis revealed that Sc-SRP-6 inhibits insect digestive enzymes, thus preventing the hydrolysis of ingested particles. Moreover, Sc-SRP-6 impaired the formation of hard clots at the injury site, a major insect defence mechanism against invasive pathogens. Sc-SRP-6 does not prevent the formation of clot fibres and the activation of prophenoloxidases but impairs the incorporation of the melanin into the clot. Binding assays showed a complex formation between Sc-SRP-6 and three proteins in the hemolymph of lepidopteran required for clotting, apolipophorin, hexamerin and trypsin-like, although the catalytic inhibition occurred exclusively in trypsin-like. This data allowed the conclusion that Sc-SRP-6 promotes nematode virulence by inhibiting insect gut juices and by impairing immune clot reaction.

Parasitic infections are often followed by changes in host behaviour. Numerous and exquisite examples of such behavioural alterations are known, covering a broad spectrum of parasites and hosts. Most descriptions of such parasite-induced changes in host behaviour are observational reports, while experimentally confirmed examples of parasite genes inducing these changes are limited. In this study, we review changes in invertebrate host behaviour observed upon infection by parasites and discuss such changes in an evolutionary context. We then explore possible mechanisms involved in parasite-induced changes in host behaviour. Genes and pathways known to play a role in invertebrate behaviour are reviewed, and we hypothesize how parasites (may) affect these pathways. This review provides the state of the art in this exciting, interdisciplinary field by exploring possible pathways triggered in hosts, suggesting methodologies to unravel the molecular mechanisms that lead to changes in host behaviour., (© 2013 John Wiley & Sons Ltd.)

How global warming will affect insect parasitoids and their role as natural enemies of insect pests is difficult to assess within a short period of time. Considering that elevation gradients can be used as analogues for global warming, we carried out meta-analyses of 27 correlations between parasitoid richness and elevation and 140 correlations between parasitism rate and elevation in natural and semi-natural environments. We also explored various covariates that may explain the observed responses. Both parasitism rates and parasitoid species richness significantly decreased with increasing elevation. The decrease was greater for ectoparasitoids and parasitoids of ectophagous insects than for endoparasitoids and parasitoids of endophagous hosts, possibly because these latter are better protected from adverse and extreme climatic conditions occurring at higher elevations. Although our results suggest an increase of parasitism with increasing temperature, other factors regulating herbivorous insects have to be considered before concluding that climate warming will lead to a decrease in pest density.

Background: An acaricidal effect of lime sulfur has not been demonstrated for Polyphagotarsonemus latus. However, lime sulfur can cause toxicity to natural enemies and to host plants. In this study, the toxicity of different concentrations of lime sulfur to P. latus, to the predatory mite Amblyseius herbicolus and to the predatory insect Chrysoperla externa was evaluated. Additionally, the phytotoxicity of lime sulfur to two P. latus hosts, chili pepper and physic nut plants, was determined., Results: Lime sulfur at a concentration of 9.5 mL L(-1) restrained P. latus population growth. However, this concentration was deleterious to natural enemies. The predatory mite A. herbicolus showed a negative value of instantaneous growth rate, and only 50% of the tested larvae of C. externa reached adulthood when exposed to 10 mL L(-1) . Physic nut had severe injury symptoms when sprayed with all tested lime sulfur concentrations. For chili pepper plants, no phytoxicity was observed at any tested concentration., Conclusion: Lime sulfur might be used for P. latus control on chili pepper but not on physic nut owing to phytotoxicity. Care should be taken when using lime sulfur in view of negative effects on natural enemies. Selective lime sulfur concentration integrated with other management tactics may provide an effective and sustainable P. latus control on chili pepper., (© 2012 Society of Chemical Industry.)

The loss of natural enemies is a key feature of species introductions and is assumed to facilitate the increased success of species in new locales (enemy release hypothesis; ERH). The ERH is rarely tested experimentally, however, and is often assumed from observations of enemy loss. We provide a rigorous test of the link between enemy loss and enemy release by conducting observational surveys and an in situ parasitoid exclusion experiment in multiple locations in the native and introduced ranges of a gall-forming insect, Neuroterus saltatorius, which was introduced poleward, within North America. Observational surveys revealed that the gall-former experienced increased demographic success and lower parasitoid attack in the introduced range. Also, a different composition of parasitoids attacked the gall-former in the introduced range. These observational results show that enemies were lost and provide support for the ERH. Experimental results, however, revealed that, while some enemy release occurred, it was not the sole driver of demographic success. This was because background mortality in the absence of enemies was higher in the native range than in the introduced range, suggesting that factors other than parasitoids limit the species in its native range and contribute to its success in its introduced range. Our study demonstrates the importance of measuring the effect of enemies in the context of other community interactions in both ranges to understand what factors cause the increased demographic success of introduced species. This case also highlights that species can experience very different dynamics when introduced into ecologically similar communities.

Gravity on Earth is a constant stimulus and many organisms are able to perceive and respond to it. However, there is no clear evidence that nematodes respond to gravity. In this study, we demonstrated negative gravitaxis in a nematode using dauer larvae (DL) of Caenorhabditis japonica, which form an association with their carrier insect Parastrachia japonensis. Caenorhabditis japonica DL demonstrating nictation, a typical host-finding behavior, had a negative gravitactic behavior, whereas non-nictating C. japonica and C. elegans DL did not. The negative gravitactic index of nictating DL collected from younger nematode cultures was higher than that from older cultures. After a 24 h incubation in M9 buffer, nictating DL did not alter their negative gravitactic behavior, but a longer incubation resulted in less pronounced negative gravitaxis. These results are indicative of negative gravitaxis in nictating C. japonica DL, which is maintained once initiated, seems to be affected by the age of DL and does not appear to be a simple passive mechanism.

Xenos is a strepsipteran genus whose members are parasitic to eusocial wasps, including the hornet genus Vespa. We undertook an extensive sampling of strepsipterans in Xenos from hornets collected in East Asia and performed molecular phylogenetic analyses based on mitochondrial cytochrome c oxidase subunit I gene sequences (652 bp) to investigate the cryptic diversity among 21 individuals of strepsipterans. The analyses, accompanied by morphological examination, revealed that these strepsipterans represent two distinct species, X. moutoni du Buysson, 1903 and X. oxyodontes sp. nov. The two species differed in their host-utilization pattern: the latter was almost specific to Vespa analis and V. simillima, whereas the former was associated with other species in Vespa.

Selection imposed by coinfection may vary with the mechanism of within-host competition between parasites. Exploitative competition is predicted to favor more virulent parasites, whereas interference competition may result in lower virulence. Here, we examine whether exploitative or interference competition determines the outcome of competition between two nematode species (Steinernema spp.), which in combination with their bacterial symbionts (Xenorhabdus spp.), infect and kill insect hosts. Multiple isolates of each nematode species, carrying their naturally associated bacteria, were characterized by (1) the rate at which they killed insect hosts, and by (2) the ability of their bacteria to interfere with each other's growth via bacteriocidal toxins called "bacteriocins." We found that both exploitative and interference abilities were important in predicting which species had a selective advantage in pairwise competition experiments. When nematodes carried bacteria that did not interact via bacteriocins, the faster killing isolate had a competitive advantage. Alternatively, nematodes could gain a competitive advantage when they carried bacteria able to inhibit the bacteria of their competitor. Thus, the combination of nematode/bacterial traits that led to competitive success depended on which isolates were paired, suggesting that variation in competitive interactions may be important for maintaining species diversity in this community., (© 2012 The Author(s). Evolution© 2012 The Society for the Study of Evolution.)

While nectaries are commonly found in flowers, some plants also form extrafloral nectaries on stems or leaves. For the first time in the family Brassicaceae, here we report extrafloral nectaries in Brassica juncea. The extrafloral nectar (EFN) was secreted from previously amorphic sites on stems, flowering stalks and leaf axils from the onset of flowering until silique formation. Transverse sections at the point of nectar secretion revealed a pocket-like structure whose opening was surrounded by modified stomatal guard cells. The EFN droplets were viscous and up to 50% of the total weight was sugars, 97% of which was sucrose in the five varieties of B. juncea examined. Threonine, glutamine, arginine and glutamate were the most abundant amino acids. EFN droplets also contained glucosinolates, mainly gluconapin and sinigrin. Nectar secretion was increased when the plants were damaged by chewing above- and belowground herbivores and sap-sucking aphids. Parasitoids of each herbivore species were tested for their preference, of which three parasitoids preferred EFN and sucrose solutions over water. Moreover, the survival and fecundity of parasitoids were positively affected by feeding on EFN. We conclude that EFN production in B. juncea may contribute to the indirect defence of this plant species., (© 2012 Blackwell Publishing Ltd.)

We demonstrated the disembarkation of the bacterial-feeding nematode Caenorhabditis japonica dauer larvae (DL) from adult Parastrachia japonensis female insects and observed the propagation of nematodes in artificial insect nests. Our results clarify the process of propagation in this nematode species and provide insights into the nematode-insect relationship. Quiescent C. japonica DL resumed their mobility only at > 99.9% relative humidity (RH) at 25°C in the presence or absence of the carrier insect. In artificial nests with > 99.9% RH, DL resumed their mobility and the number of DL on female insects decreased gradually after oviposition, although numerous DL remained on the insects. Very few DL were detected on mother insects after hatching. Nematode propagation was observed on the egg mass after hatching and on nymphal carcasses; the total number of nematodes in the nest increased dramatically after this point. These results indicate that humidity is an important factor for disembarkation of C. japonica DL and that C. japonica propagates in the nest of P. japonensis where it feeds on the remains of eggs and nymph carcasses, indicating that C. japonica and P. japonensis have a unique phoretic and necromenic association.

Entomopathogenic nematodes are effective biological control agents against insect pests but their commercial application is restricted by their limited shelf life. This study applies our knowledge of the cold tolerance of nematodes to this problem and investigates further the cold tolerance mechanisms of Steinernema feltiae and Heterorhabditis bacteriophora infective juveniles. When frozen using a fast freezing regime these nematodes are moderately freezing tolerant, with a lower lethal temperature of -5°C. Survival is significantly enhanced by slow freezing overnight (at -1°C), with a decrease in the lower lethal temperature to -14°C. This may indicate that these nematodes are capable of cryoprotective dehydration. Acclimation at 5°C further enhanced freezing survival in S. feltiae but only by a small amount. Nematodes that had survived freezing to -13°C retained their pathogenicity to an insect host. Rapid cold hardening or exposure to a cold shock had no significant effect on freezing survival. The further development of methods based on cryoprotective dehydration may result in a method for the commercial storage of these nematodes., (Copyright © 2012 Elsevier Inc. All rights reserved.)

Nutrition is critical to immune defence and parasite resistance, which not only affects individual organisms, but also has profound ecological and evolutionary consequences. Nutrition and immunity are complex traits that interact via multiple direct and indirect pathways, including the direct effects of nutrition on host immunity but also indirect effects mediated by the host's microbiota and pathogen populations. The challenge remains, however, to capture the complexity of the network of interactions that defines nutritional immunology. The aim of this paper is to discuss the recent findings in nutritional research in the context of immunological studies. By taking examples from the entomological literature, we argue that insects provide a powerful tool for examining the network of interactions between nutrition and immunity due to their tractability, short lifespan and ethical considerations. We describe the relationships between dietary composition, immunity, disease and microbiota in insects, and highlight the importance of adopting an integrative and multi-dimensional approach to nutritional immunology., (Crown Copyright © 2012. Published by Elsevier Ltd. All rights reserved.)

Fifteen species of freshwater Nematomorpha have been described from India, five of which belong to the genus Chordodes. This paper describes one new species of horsehair worms (Nematomorpha): Chordodes lasuboni and a new record, C. moutoni from North-East India, which raises the total number of described species from India to 17. Chordodes lasuboni is characterized by a novel cuticular pattern in the head region and by the presence of slender, hooked thorn areoles on the body cuticle. Compared to the large size and ecological diversity of India, the nematomorph fauna is regarded as under-sampled and several new species are to be expected.

Immature development of parasitoid wasps is restricted to resources found in a single host that is often similar in size to the adult parasitoid. When two or more parasitoids of the same or different species attack the same host, there is competition for monopolization of host resources. The success of intrinsic competition differs between parasitoids attacking growing hosts and parasitoids attacking paralyzed hosts. Furthermore, the evolution of gregarious development in parasitoids reflects differences in various developmental and behavioral traits, as these influence antagonistic encounters among immature parasitoids. Fitness-related costs (or benefits) of competition for the winning parasitoid reveal that time lags between successive attacks influence the outcome of competition. Physiological mechanisms used to exclude competitors include physical and biochemical factors that originate with the ovipositing female wasp or her progeny. In a broader multitrophic framework, indirect factors, such as plant quality, may affect parasitoids through effects on immunity and nutrition.

The immune response affects host's survival and reproductive success. Insurmountable immune function has not evolved because it is costly and there is a trade-off between other life-history traits. In previous studies several factors such as diet and temperature have been proposed to cause interpopulation differences in immune response. Moreover, the insect immune system may be functionally more protective upon secondary exposure, thus infection history may associate with the immune response. Here we measured how geographical location and parasite burden is related to variation in immune response between populations. We included 13 populations of the Northern Damselfly Coenagrion hastulatum (Odonata: Coenagrionidae) in Finland over a latitudinal range of 880 km to this study. We found that water mites associated strongly with the immune response at interpopulation level: the more the mites, the higher the immune response. Also, in an alternative model based on AIC, latitude and individual size associated with the immune response. In turn, endoparasitic gregarines did not affect the immune response. To conclude, a positive interpopulation association between the immune response and the rate of water mite infection may indicate (i) local adaptation to chronic parasite stress, (ii) effective 'induced' immune response against parasites, or (iii) a combined effect of both of these.

Millions of years of co-evolution have driven parasites to display very complex and exquisite strategies to manipulate the behaviour of their hosts. However, although parasite-induced behavioural manipulation is a widespread phenomenon, the underlying neuronal mechanisms are only now beginning to be deciphered. Here, we review recent advancements in the study of the mechanisms by which parasitoid wasps use chemical warfare to manipulate the behaviour of their insect hosts. We focus on a particular case study in which a parasitoid wasp (the jewel wasp Ampulex compressa) performs a delicate brain surgery on its prey (the American cockroach Periplaneta americana) to take away its motivation to initiate locomotion. Following a brief background account of parasitoid wasps that manipulate host behaviour, we survey specific aspects of the unique effects of the A. compressa venom on the regulation of spontaneous and evoked behaviour in the cockroach host.

The entomopathogenic nematode (EPN) Heterorhabditis bacteriophora is used in biological plant protection to control pest insects. In the past, several attempts targeted at an enhancement of the desiccation tolerance of EPN by genetic selection in order to improve their storage stability. The subsequent loss of improved beneficial traits after release of selection pressure has often been reported. In order to stabilize progress of selective breeding, selection during liquid culturing was tested against propagation in host insects. After release of the selection pressure, the tolerance was monitored over additional reproductive cycles in vivo and in vitro to compare the stability of the trait. Furthermore, it was tested whether the virulence of the selected strains would be impaired. Exposure to desiccation stress prior to propagation, in vivo or in vitro, both resulted in increasing desiccation tolerance. When selection pressure was released, the gained tolerance was lost again during in vivo production, whereas the tolerance was maintained at a high level when EPNs were cultured in liquid culture. In Heterorhabditis sp., liquid culture conditions produce highly homozygous, genetically stable inbred lines. The investigation provides easily applicable methods to improve and stabilize beneficial traits of heterorhabditid EPNs through selective breeding in liquid culture. Compared to nematodes from in vivo propagation, production in liquid media yielded EPN of higher virulence.

Several new species of trypanosomatids (Euglenozoa, Kinetoplastea, Trypanosomatidae), isolated from the intestines of Neotropical insects (Heteroptera), were genotyped on the basis of spliced leader RNA, and also defined phylogenetically using gene sequences of small subunit ribosomal RNA and glycosomal glyceraldehyde phosphate dehydrogenase. The taxonomic descriptions also included characterization using morphometry and electron microscopy. Our phylogenetic analyses placed the new species within the clade, previously designated "SE" for "Slowly Evolving" sequences of ribosomal RNA genes, a clade that also includes numerous monoxenous parasites of insects from the genera Crithidia, Leptomonas, and Wallaceina, as well as the dixenous genus Leishmania. Based on the high phylogenetic support for this clade, which is consistently recovered in all recent phylogenetic reconstructions, a proposal is put forward to recognize this natural taxon as a new subfamily, Leishmaniinae, within the family Trypanosomatidae., (© 2012 The Author(s) Journal of Eukaryotic Microbiology © 2012 International Society of Protistologists.)

Entomopathogenic nematodes are widely used as biological control agents that can suppress or evade the host immune defense upon entry into insects. The surface coat of Steinernema glaseri has been shown to play important roles in defeating the host immune system. In this work, a protein fraction with antiphagocytic activity was separated by electro-elution and further analyzed by two-dimensional electrophoresis (2-DE). LC-MS/MS analysis of one protein spot from a 2-DE gel gave five peptides that were highly similar to enolases of many organisms. A 1311 bp cDNA was cloned that encodes a 47 kDa protein with high sequence identity to enolases from different species of nematodes. The deduced protein, Sg-ENOL, was expressed in Escherichia coli, and its glycolytic activity was demonstrated by the conversion of 2-phospho-d-glycerate to phosphoenolpyruvate. Recombinant Sg-ENOL significantly reduced the LT(50)s of Xenorhabdus poinarii and Metarhizium anisopliae when co-injected into Galleria mellonella and Locusta migratoria manilensis Meyen, respectively. Using immuno-gold transmission electron microscopy, native Sg-ENOL was confirmed to be localized to both the nematode cuticle and the surface coat. In vitro, secretion of Sg-ENOL was inducible rather than constitutive. In vivo, Sg-ENOL was detected in the host hemolymph after infection of G. mellonella with S. glaseri, indicating that Sg-ENOL was secreted into the insect hemocoel and was involved in infection. This is the first report of the cloning and characterization of a surface coat protein in an entomopathogenic nematode. Our findings provide clear evidence for an important role for a cell surface enolase in S. glaseri infection and host immune suppression., (Copyright © 2012 Elsevier B.V. All rights reserved.)

Mitochondrial ND8 gene is pan-edited in most known trypanosomatid species and 5'-edited only in a few trypanosomatid species. In this work, the ND8 nucleotide sequences from three species of insect trypanosomatids ("Wallaceina" sp. Wsd, Leptomonas rigidus and Leptomonas collosoma) were obtained and compared with previously known ND8 cryptogene sequences and mature mRNA sequences from other trypanosomatid species. We found a new pattern of editing: only 18 U residues are inserted in the 5' region of the primary transcript in all investigated species and the potential start codon is encoded on the DNA level. This is the first case when a pre-edited ND8 sequence is found to contain a putative ORF. Previously, a 5'-edited ND8 cryptogene was known only from Strigomonas oncopelti, but it contained only about half of the ORF and no start codon. Here we present the ND8 gene sequence from Angomonas deanei which has similar cryptogene structure. We also show that according to 18S rRNA phylogenetic analysis, the species with the encoded ORF group together and so do species with the 5'-edited and pan-edited forms of the gene. This result sheds light on the evolution of cryptogene structure which involved multiple events of editing domain length reduction., (Copyright © 2011 Elsevier GmbH. All rights reserved.)

While often studied in isolation, host-parasite interactions are typically embedded within complex communities. Other community members, including predators and alternative hosts, can therefore alter parasite transmission (e.g., the dilution effect), yet few studies have experimentally evaluated more than one such mechanism. Here, we used data from natural wetlands to design experiments investigating how alternative hosts and predators of parasites mediate trematode (Ribeiroia ondatrae) infection in a focal amphibian host (Pseudacris regilla). In short-term predation bioassays involving mollusks, zooplankton, fish, larval insects, or newts, four of seven tested species removed 62-93% of infectious stages. In transmission experiments, damselfly nymphs (predators) and newt larvae (alternative hosts) reduced infection in P. regilla tadpoles by -50%, whereas mosquitofish (potential predators and alternative hosts) did not significantly influence transmission. Additional bioassays indicated that predators consumed parasites even in the presence of alternative prey. In natural wetlands, newts had similar infection intensities as P. regilla, suggesting that they commonly function as alternative hosts despite their unpalatability to downstream hosts, whereas mosquitofish had substantially lower infection intensities and are unlikely to function as hosts. These results underscore the importance of studying host-parasite interactions in complex communities and of broadly linking research on predation, biodiversity loss, and infectious diseases.

The life-history stages of Ganeo tigrinus Mehra & Negi, 1928 infecting the Indian bull frog Hoplobatrachus tigerinus (Daudin) are described, those from cercaria to egg-producing adult having been established in the laboratory. Non-virgulate xiphidiocercariae are released by the planorbid snail Indoplanorbis exustus (Deshayes). Metacercariae occur in the haemocoel of dragonfly nymphs and become infective to the frog H. tigerinus within 15 days. The pre-patent period is 45 days. Growth and development of both metacercariae and adults are described in detail. Comments on the systematic position of Ganeo Klein, 1905 are included.

Three hundred and eighty-six heteropteran specimens belonging to more than 90 species captured in Ghana, Kenya and Ethiopia were examined for the presence of trypanosomatid flagellates. Of those, 100 (26%) specimens were positive for trypanosomatids and the spliced leader RNA gene sequence was obtained from 81 (80%) of the infected bugs. Its sequence-based analysis placed all examined flagellates in 28 typing units. Among 19 newly described typing units, 16 are restricted to sub-Saharan Africa, three belong to previously described species and six to typing units found on other continents. This result was corroborated by the analysis of the ssrRNA gene, sequenced for at least one representative of each major spliced leader RNA-based clade. In all trees obtained, flagellates originating from sub-Saharan Africa were intermingled with those isolated from American, Asian and European hosts, revealing a lack of geographic correlation. They are dispersed throughout most of the known diversity of monoxenous trypanosomatids. However, a complex picture emerged when co-evolution with their heteropteran hosts was taken into account, since some clades are specific for a single host clade, family or even species, whereas other flagellates display a very low host specificity, with a capacity to parasitise heteropteran bugs belonging to different genera/families. The family Reduviidae contains the widest spectrum of trypanosomatids, most likely a consequence of their predatory feeding behaviour, leading to an accumulation of a variety of flagellates from their prey. The plant pathogenic genus Phytomonas is reported here from Africa, to our knowledge for the first time. Finding the same typing units in hosts belonging to different heteropteran families and coming from different continents strongly indicates that the global diversity of the insect trypanosomatids is most likely lower than was predicted on the basis of the "one host-one parasite" paradigm. The analysis presented significantly extends the known diversity of monoxenous insect trypanosomatids and will be instrumental in building a new taxonomy that reflects their true phylogenetic relationships., (Copyright © 2012. Published by Elsevier Ltd.)