Multiple and frequent trypanosomatid co-infections of insects: the Cuban case study.

Trypanosomatids are obligate parasites of animals, predominantly insects and vertebrates, and flowering plants. Monoxenous species, representing the vast majority of trypanosomatid diversity, develop in a single host, whereas dixenous species cycle between two hosts, of which primarily insect serves as a vector. To explore in-depth the diversity of insect trypanosomatids including their co-infections, sequence profiling of their 18S rRNA gene was used for true bugs (Hemiptera; 18% infection rate) and flies (Diptera; 10%) in Cuba. Out of 48 species (molecular operational taxonomic units) belonging to the genera Vickermania (16 spp.), Blastocrithidia (7), Obscuromonas (4), Phytomonas (5), Leptomonas/Crithidia (5), Herpetomonas (5), Wallacemonas (2), Kentomonas (1), Angomonas (1) and two unnamed genera (1 + 1), 38 species have been encountered for the first time. The detected Wallacemonas and Angomonas species constitute the most basal lineages of their respective genera, while Vickermania emerged as the most diverse group. The finding of Leptomonas seymouri, which is known to rarely infect humans, confirms that Dysdercus bugs are its natural hosts. A clear association of Phytomonas with the heteropteran family Pentatomidae hints at its narrow host association with the insect rather than plant hosts. With a focus on multiple infections of a single fly host, using deep Nanopore sequencing of 18S rRNA, we have identified co-infections with up to 8 trypanosomatid species. The fly midgut was usually occupied by several Vickermania species, while Herpetomonas and/or Kentomonas species prevailed in the hindgut. Metabarcoding was instrumental for analysing extensive co-infections and also allowed the identification of trypanosomatid lineages and genera.

The spread of satellite DNAs in euchromatin and insights into the multiple sex chromosome evolution in Hemiptera revealed by repeatome analysis of the bug Oxycarenus hyalinipennis.

Satellite DNAs (satDNAs) are highly repeated tandem sequences primarily located in heterochromatin, although their occurrence in euchromatin has been reported. Here, our aim was to advance the understanding of satDNA and multiple sex chromosome evolution in heteropterans. We combined cytogenetic and genomic approaches to study, for the first time, the satDNA composition of the genome in an Oxycarenidae bug, Oxycarenus hyalinipennis. The species exhibits a male karyotype of 2n = 19 (14A + 2 m + X1 X2 Y), with a highly differentiated Y chromosome, as demonstrated by C-banding and comparative genomic hybridization, revealing an enrichment of repeats from the male genome. Additionally, comparative analysis between males and females revealed that the 26 identified satDNA families are significantly biased towards male genome, accumulating in discrete regions in the Y chromosome. Exceptionally, the OhyaSat04-125 family was found to be distributed virtually throughout the entire extension of the Y chromosome. This suggests an important role of satDNA in Y chromosome differentiation, in comparison of other repeats, which collectively shows similar abundance between sexes, about 50%. Furthermore, chromosomal mapping of all satDNA families revealed an unexpected high spread in euchromatic regions, covering the entire extension, irrespective of their abundance. Only discrete regions of heterochromatin on the Y chromosome and of the m-chromosomes (peculiar chromosomes commonly observed in heteropterans) were enriched with satDNAs. The putative causes of the intense enrichment of satDNAs in euchromatin are discussed, including the possible existence of burst cycles similar to transposable elements and as a result of holocentricity. These data challenge the classical notion that euchromatin is not enriched with satDNAs.

Ontogenetic change in effectiveness of chemical defence against different predators in Oxycarenus true bugs.

Many prey species change their antipredator defence during ontogeny, which may be connected to different potential predators over the life cycle of the prey. To test this hypothesis, we compared reactions of two predator taxa - spiders and birds - to larvae and adults of two invasive true bug species, Oxycarenus hyalinipennis and Oxycarenus lavaterae (Heteroptera: Oxycarenidae) with life-stage-specific chemical defence mechanisms. The reactions to larvae and adults of both true bug species strikingly differed between the two predator taxa. The spiders were deterred by the defences of adult bugs, but the larval defences were ineffective against them. By contrast, birds attacked the larvae considerably less often than the adult bugs. The results indicate a predator-specific ontogenetic change in defence effectiveness of both Oxycarenus species. The change in defence is likely linked to the life-stage-specific composition of secretions in both species: whereas secretions of larvae are dominated by unsaturated aldehydes, secretions of adults are rich in terpenoids, which probably serve dual function of defensive chemicals and pheromones. Our results highlight the variation in defence between different life stages and the importance of testing responses of different types of predators.

Juvenile hormone identification in the cabbage bug Eurydema rugosa.

Juvenile hormone (JH) plays a pivotal role in almost every aspect of insect development and reproduction. The chemical structure of the JH in heteropteran species has long remained elusive until methyl (2R,3S,10R)-2,3;10,11-bisepoxyfarnesoate, commonly named as juvenile hormone III skipped bisepoxide (JHSB3), was isolated from Plautia stali (Hemiptera: Heteroptera: Pentatomidae). Recently, several groups reported the presence of JHSB3 in other heteropteran species. However, most of the studies paid no attention to the determination of the relative and absolute structure of the JH. In this study, we investigated the JH of the cabbage bug Eurydema rugosa (Hemiptera: Heteroptera: Pentatomidae), known as a pest for wild and cultivated crucifers. JHSB3 was detected in the hexane extract from the corpus allatum (CA) product using a chiral ultraperformance liquid chromatography-tandem mass spectrometer (UPLC-MS/MS) which can inform the absolute stereochemistry of the JH. Its stereoisomers were not detected. Topical application of the synthetic JHSB3 to the last instar nymphs inhibited their metamorphosis and induced nymphal-type colouration of the dorsal abdomen in a dose-dependent manner. Additionally, the topical application of JHSB3 effectively terminated summer and winter diapauses in females. These results indicate that the JH of E. rugosa is JHSB3. Although individuals in summer and winter diapauses are physiologically distinct in E. rugosa, the results suggest that the physiological differences between these diapauses are based, not on the responsiveness to JH, but on the processes governing activation of the CA or on its upstream cascades.

Food habits of 3 myrmecophilous bug species on myrmecophytic Macaranga (Malpighiales: Euphorbiaceae) vary from herbivory to predation.

Myrmecophytes have mutualistic relationships with symbiotic ants. Although myrmecophytic Macaranga (Malpighiales: Euphorbiaceae) species are well protected by aggressive Crematogaster (Hymenoptera: Formicidae) ants, some bug species occur on the myrmecophytes. To clarify the associations of these bugs with the plants and the ants, we studied the food habits of 3 bug species, Pilophorus lambirensis Nakatani et Komatsu, 2013 (Hemiptera: Miridae: Phylinae), Phylinae sp. 1, and Arbela sp. 1 (Hemiptera: Nabidae). We conducted field observations in a Bornean rainforest. First, we located these bugs and studied their behavioral responses to the ants on Macaranga species; we then conducted stable isotope analyses. All bugs avoided direct contact with ants, but they occurred only on trees with active ants. Pilophorus lambirensis and Phylinae sp. 1 were most commonly observed on the apical parts of host trees, whereas Arbela sp. 1 was mainly in areas distant from the apical parts where ants were sparse. The stable isotope ratios indicated that Phylinae sp. 1 fed on food bodies, which are nutrient-rich spherical bodies produced by Macaranga trees on the apical parts for ants. Although the main diet of the other 2 species remains unclear, nitrogen isotopic signatures demonstrated that P. lambirensis is herbivorous, whereas Arbela sp. 1 is carnivorous. However, the distant location from ants and its isotopic signatures indicated that Arbela sp. 1 rarely fed on the ants. At least 2 mirid bug species might obtain enemy-free space in addition to the food provided by the myrmecophytes.

Phytoremediation of crude oil-contaminated sediment using Suaeda heteroptera enhanced by Nereis succinea and oil-degrading bacteria.

A 150-day experiment was performed to investigate the stimulatory effect of a promising phytoremediation strategy consisting of Suaeda heteroptera (S. heteroptera), Nereis succinea (N. succinea), and oil-degrading bacteria for cleaning up total petroleum hydrocarbons (TPHs) in spiked sediment. Inoculation with oil-degrading bacteria and/or N. succinea increased plant yield and TPH accumulation in S. heteroptera plants. The highest TPH dissipation (40.5%) was obtained in the combination treatment, i.e., S. heteroptera + oil-degrading bacteria + N. succinea, in which the sediment TPH concentration decreased from an initial value of 3955 to 2355 mg/kg in 150 days. BAF, BCF, and TF confirmed the role of N. succinea and oil-degrading bacteria in the amelioration and translocation of TPHs. In addition, TPH toxicity of S. heteroptera was alleviated by N. succinea and oil-degrading bacteria addition through the reduction of oxidative stress. Therefore, S. heteroptera could be used for cleaning up oil-contaminated sediment, particularly in the presence of oil-degrading bacteria + N. succinea. Field studies on oil-degrading bacteria + N. succinea may provide new insights on the rehabilitation and restoration of sediments contaminated by TPHs.

Our study attempted to investigate the stimulatory effect of a promising phytoremediation strategy consisting of Suaeda heteroptera (S. heteroptera), Nereis succinea (N. succinea), and oil-degrading bacteria for cleaning up TPH in spiked sediment. Planting S. heteroptera can greatly increase sediment TPH removal, and its removal was enhanced greater after inoculation with oil-degrading bacteria and/or N. succinea. Moreover, the promising phytoremediation strategy developed in the current work can serve as an efficient, novel approach to removal TPH in sediment/soil. In our opinions, these findings provide insights into the assessment of their ecological risks in the environments that are of interest to broad readership of International Journal of Phytoremediation.

Comparative analysis of detoxification-related gene superfamilies across five hemipteran species.

BACKGROUND: Hemiptera is one of the most speciose orders of insects, and the most speciose considering Hemimetabola. Through their evolutive history, hemipterans with different feeding habits have adapted to deal with different chemical challenges. Three major gene families are involved in xenobiotic detoxification in insects: the cytochromes P450 (CYPs), carboxyl/cholinesterases (CCEs), and glutathione transferases (GSTs). Here we perform a comparative analysis on the complement of these gene superfamilies across five hemipteran species; four heteropterans (the pentatomid plant feeders Nezara viridula and Halyomorpha halys; the hematophagous Cimex lectularius, Cimicidae, and Rhodnius prolixus, Reduviidae), and one Auchenorrhyncha plant feeder (Nilaparvata lugens). RESULTS: Our results point to an expansion of several enzyme families associated with xenobiotic detoxification in heteropterans with respect to other species and the existence of a dynamic evolution pattern including CYP3 clan, hormone and pheromone processing class in the CCE superfamily, and sigma class in GST superfamily. Other detoxification-related families are reduced in the hemipteran species analyzed here: reduction or even absence of epsilon class and reduced delta class in GST superfamily; absence of mitochondrial CYP12 family; absence of CYP9 family in CYP3 clan; and reduction or even absence of some dietary/detoxification groups of CCEs. Interestingly, the most polyphagous species analyzed here (H. halys) is also the one that presents the largest repertoire of detoxification enzymes. Gene cluster analysis suggests that this could be due to gene duplication events. CONCLUSIONS: The evolutionary analysis performed here reveals characteristics that are both common and particular for heteropterans. The composition and organization of detoxification-related gene families could shed light on evolutionary forces that shaped their divergence. These families are important for both the detoxification of diet products and for conferring tolerance or resistance to synthetic insecticides. Furthermore, we present the first comprehensive analysis of detoxification gene superfamilies in N. viridula, an understudied species in spite of its economic relevance as a crop pest. The information obtained is of interest for basic insect science as well as for the control of harmful species and the management of insecticide resistance.

Prevalence of an Insect-Associated Genomic Region in Environmentally Acquired Burkholderiaceae Symbionts.

Microbial symbionts are critical for the development and survival of many eukaryotes. Recent research suggests that the genes enabling these relationships can be localized in horizontally transferred regions of microbial genomes termed "symbiotic islands." Recently, a putative symbiotic island was found that may facilitate symbioses between true bugs and numerous Burkholderia species, based on analysis of five Burkholderia symbionts. We expanded on this work by exploring the putative island's prevalence, origin, and association with colonization across the bacterial family Burkholderiaceae. We performed a broad comparative analysis of 229 Burkholderiaceae genomes, including 8 new genomes of insect- or soil-associated Burkholderia sequenced for this study. We detected the region in 23% of the genomes; these were located solely within two Burkholderia clades. Our analyses suggested that the contiguous region arose at the common ancestor of plant- and insect-associated Burkholderia clades, but the genes themselves are ancestral. Although the region was initially discovered on plasmids and we did detect two likely instances of horizontal transfer within Burkholderia, we found that the region is almost always localized to a chromosome and does not possess any of the mobility elements that typify genomic islands. Finally, to attempt to deduce the region's function, we combined our data with information on several strains' abilities to colonize the insect's symbiotic organ. Although the region was associated with improved colonization of the host, this relationship was confounded with, and likely driven by, Burkholderia clade membership. These findings advance our understanding of the genomic underpinnings of a widespread insect-microbe symbiosis. IMPORTANCE Many plants and animals form intricate associations with bacteria. These pairings can be mediated by genomic islands, contiguous regions containing numerous genes with cohesive functionality. Pathogen-associated islands are well described, but recent evidence suggests that mutualistic islands, which benefit both host and symbiont, may also be common. Recently, a putative symbiosis island was found in Burkholderia symbionts of insects. We determined that this genomic region is located in only two clades of Burkholderia (the plant- and insect-associated species) and that although it has undergone horizontal transfer, it is most likely a symbiosis-associated region rather than a true island. This region is associated with improved host colonization, although this is may be due to specific Burkholderia clades' abilities to colonize rather than presence of the region. By studying the genomic basis of the insect-Burkholderia symbiosis, we can better understand how mutualisms evolve in animals.

The phylogenetic position of Arhaphe deviatica within Hemipteran insects: A potential model species for eco-devo studies of symbiosis.

Insecta is known to be the most diverse group of species, exhibiting numerous forms of endosymbiotic associations. Molecular techniques have provided significant indicators for insect-microbe interactions. The present study aimed to register one of the true bugs of pentatomomorpha and clarify its taxonomic position through phylogenetic analysis of the partial 16S rRNA gene region. A maximum likelihood analysis retrieved a generally well-supported phylogeny based on Tamura 3-parameter model. Based on the partial mitochondrial 16S rRNA gene sequences, a phylogenetic study of suborder Heteroptera relationships within Hemipteras' order was constructed. Sequences of 221 bases of the 3' end of the gene from 28 species within 16 families were analyzed. This analysis and bootstrap confidence revealed two major clades comprising four suborders within Hemiptera, with a close relationship between Heteroptera + (Sternorrhyncha + (Auchenorrhycha + Coleorrhyncha)). Infraorder Pentatomomorpha is forming a sister group with a substantial bootstrap value to Cimicomorpha. Pyrrhocoroidea forms a sister relationship with Lygaeoidea + Coreoidea. There is a close relationship between Largidae and Pyrrhocoridae within Pyrrhocoroidea. The results show that the present species is firmly embedded in the genus Arhaphe with 94.35% sequence resemblance to its congeners. Besides, the recovered hemipteran species considered a potential model group for studying different symbionts. We propose both phylogenetic and ecological evolutionary developmental biology viewpoints for a more synthetic understanding of insect populations' molecular evolution.

Benefits and costs of hosting facultative symbionts in plant-sucking insects: A meta-analysis.

Many animals have evolved associations with symbiotic microbes that benefit the host through increased growth, lifespan, and survival. Some interactions are obligate (essential for survival) while others are facultative (usually beneficial but not essential). Not all individuals host all facultative symbionts in a population, and thus there is probably a trade-off between the cost of hosting these symbionts and the benefits they confer to the host. Plant-sucking insects have been one of the most important models to test these costs and benefits experimentally. This research is now moving beyond the description of symbiont effects towards understanding the mechanisms of action, and their role in the wider ecological community. We present a quantitative and systematic analysis of the published evidence exploring this question. We found that whitefly and true bugs experience benefits through increased growth and fecundity, whereas aphids experience costs to their fecundity but benefits through increased resistance to natural enemies. We also report the lack of data in some plant-sucking groups, and explore variation in effect strengths and directions across aphid host, symbiont and plant species thus highlighting the importance of considering the context dependency of these interactions.

Ecological niche modeling (ENM) of Leptoglossus clypealis a new potential global invader: following in the footsteps of Leptoglossus occidentalis?

The introduction of alien species is one of the main problems in conservation. Many successful invaders cause severe economic and ecological damage. Such is the case of Leptoglossus occidentalis, a phytophagous true bug native to North America, which has become a pest in Europe, Asia, Africa and South America. Within the genus, another species whose distributional range is expanding toward the east of North America is Leptoglossus clypealis. As climate determines the successful establishment of insects, the identification of climatically suitable areas for invasive species based on ecological niche models (ENMs) offers an excellent opportunity for preventing invasions. In this study, ENMs were built for both species and their native climatic niches were compared. Their niche breath was also measured. The climatic niches of both species are identical and the niche breadth of L. clypealis is broader than that of L. occidentalis. In view of the great ecological resemblance between these two species, we believe that L. clypealis could became a major pest thus it should be carefully monitored. The results of the present worldwide ENMs showed numerous regions with suitable conditions for the establishment of both species. The future ENMs exhibited a retraction in the suitable areas in North America, Europe and Asia.

Juvenile hormone III skipped bisepoxide, not its stereoisomers, as a juvenile hormone of the bean bug Riptortus pedestris.

Juvenile hormone (JH) plays a pivotal role in many aspects of insect physiology. Although its presence was first reported in a blood-sucking bug belonging to the suborder Heteroptera (true bugs), JH species in the group has long been controversial. Although some recent studies proposed a putative JH molecular species in several Heteropteran species, it is not conclusive because physicochemical analyses were insufficient in most cases. Here, we studied this issue with an ultraperformance liquid chromatography-tandem mass spectrometer (UPLC-MS/MS) equipped with C18 and chiral columns in the bean bug Riptortus pedestris (Heteroptera, Alydidae), in which the JH species has long been controversial. Although a recent study describes JHSB3 as the major JH of this species, that finding was not conclusive because its chirality has not been clarified. In the present study, we detected methyl (2R,3S,10R)-2,3;10,11-bisepoxyfarnesoate, commonly named juvenile hormone III skipped bisepoxide (JHSB3), in the culture media of the corpora cardiaca-corpus allatum (CC-CA) complex and in the hemolymph of this species by a chiral ultraperformance liquid chromatography- tandem mass spectrometer (UPLC-MS/MS). Other JHSB3 stereoisomers were not detected. Topical application of JHSB3 effectively averted diapause. These results indicate that JHSB3 is the major JH of R. pedestris. The present study further revealed that JHSB3 and its (2R,3S,10S) isomer are more potent than (2S,3R,10R) and (2S,3R,10S) isomers, which suggests that there is a significance to the configuration of the 2,3-epoxide moiety in JH action. We further found a supplemental significance to the configuration of the 10-position.

Established Cotton Stainer Gut Bacterial Mutualists Evade Regulation by Host Antimicrobial Peptides.

Symbioses with microorganisms are ubiquitous in nature and confer important ecological traits to animal hosts but also require control mechanisms to ensure homeostasis of the symbiotic interactions. In addition to protecting hosts against pathogens, animal immune systems recognize, respond to, and regulate mutualists. The gut bacterial symbionts of the cotton stainer bug, Dysdercus fasciatus, elicit an immune response characterized by the upregulation of c-type lysozyme and the antimicrobial peptide pyrrhocoricin in bugs with their native gut microbiota compared to that in dysbiotic insects. In this study, we investigated the impact of the elicited antimicrobial immune response on the established cotton stainer gut bacterial symbiont populations. To this end, we used RNA interference (RNAi) to knock down immunity-related genes hypothesized to regulate the symbionts, and we subsequently measured the effect of this silencing on host fitness and on the abundance of the major gut bacterial symbionts. Despite successful downregulation of target genes by both ingestion and injection of double-stranded RNA (dsRNA), the silencing of immunity-related genes had no effect on either host fitness or the qualitative and quantitative composition of established gut bacterial symbionts, indicating that the host immune responses are not actively involved in the regulation of the nutritional and defensive gut bacterial mutualists. These results suggest that close associations of bacterial symbionts with their hosts can result in the evolution of mechanisms ensuring that symbionts remain insensitive to host immunological responses, which may be important for the evolutionary stability of animal-microbe symbiotic associations.IMPORTANCE Animal immune systems are central for the protection of hosts against enemies by preventing or eliminating successful infections. However, in the presence of beneficial bacterial mutualists, the immune system must strike a balance of not killing the beneficial symbionts while at the same time preventing enemy attacks. Here, using the cotton stainer bug, we reveal that its long-term associated bacterial symbionts are insensitive to the host's immune effectors, suggesting adaptation to the host's defenses, thereby strengthening the stability of the symbiotic relationship. The ability of the symbionts to elicit host immune responses but remain insensitive themselves may be a mechanism by which the symbionts prime hosts to fight future pathogenic infections.

Insight from an ultraconserved element bait set designed for hemipteran phylogenetics integrated with genomic resources.

Target enrichment of conserved genomic regions facilitates collecting sequences of many orthologous loci from non-model organisms to address phylogenetic, phylogeographic, population genetic, and molecular evolution questions. Bait sets for sequence capture can simultaneously target thousands of loci, which opens new avenues of research on speciose groups. Current phylogenetic hypotheses on the >103,000 species of Hemiptera have failed to unambiguously resolve major nodes, suggesting that alternative datasets and more thorough taxon sampling may be required to resolve relationships. We use a recently designed ultraconserved element (UCE) bait set for Hemiptera, with a focus on the suborder Heteroptera, or the true bugs, to test previously proposed relationships. We present newly generated UCE data for 36 samples representing three suborders, all seven heteropteran infraorders, 23 families, and 34 genera of Hemiptera and one thysanopteran outgroup. To improve taxon sampling, we also mined additional UCE loci in silico from published hemipteran genomic and transcriptomic data. We obtained 2271 UCE loci for newly sequenced hemipteran taxa, ranging from 265 to 1696 (average 904) per sample. These were similar in number to the data mined from transcriptomes and genomes, but with fewer loci overall. The amount of missing data correlates with greater phylogenetic divergence from taxa used to design the baits. This bait set hybridizes to a wide range of hemipteran taxa and specimens of varying quality, including dried specimens as old as 1973. Our estimated phylogeny yielded topologies consistent with other studies for most nodes and was strongly-supported. We also demonstrate that UCE loci are almost exclusively from the transcribed portion of the genome, thus data can be successfully integrated with existing genomic and transcriptomic resources for more comprehensive phylogenetic sampling, an important feature in the era of phylogenomics. UCE approaches can be used by other researchers for additional studies on hemipteran evolution and other research that requires well resolved phylogenies.

High Prevalence and Endemism of Trypanosomatids on a Small Caribbean Island.

We describe the monoxenous trypanosomatids parasitizing true bugs and flies on the island of Curaçao. Out of 248 examined true bugs belonging to 17 species, 93 individuals were found to be infected (overall 38% prevalence) by at least one trypanosomatid species (referred to as typing units; TUs). Out of 80 flies, six were infected. All detected trypanosomatids were compared based on their 18S rRNA sequences with TUs parasitizing bugs and flies described from mainland South America, allowing us to assess their diversity and distribution. Besides Leptomonas pyrrhocoris and Leptomonas seymouri, two known species of the subfamily Leishmaniinae, our analysis revealed six new TUs falling into the groups 'jaculum', Blastocrithidia and Herpetomonas. Moreover, two new members of the genus Phytomonas and three new TUs belonging to the monophyletic group designated as 'new clade II' sensu Mol. Phylogenet. Evol, 69, 255 (2013) were isolated. The detected trypanosomatids were characterized by moderate diversity (13 TUs) species richness. Out of nine and four TUs from the heteropteran and dipteran hosts, respectively, 11 TUs have not been encountered before. Although a sampling bias may partially affect the comparison between trypanosomatid communities on Curaçao and the mainland, the high proportion of unique TUs from the former location suggests that the prominent role of islands in increasing the global diversity of macroscopic organisms may also extend to their protistan parasites.

Giant fish-killing water bug reveals ancient and dynamic venom evolution in Heteroptera.

True Bugs (Insecta: Heteroptera) produce venom or saliva with diverse bioactivities depending on their feeding strategies. However, little is known about the molecular evolution of the venom toxins underlying these biological activities. We examined venom of the giant fish-killing water bug Lethocerus distinctifemur (Insecta: Belostomatidae) using infrared spectroscopy, transcriptomics, and proteomics. We report 132 venom proteins including putative enzymes, cytolytic toxins, and antimicrobial peptides. Over 73% (96 proteins) showed homology to venom proteins from assassin bugs (Reduviidae), including 21% (28 proteins from seven families) not known from other sources. These data suggest that numerous protein families were recruited into venom and diversified rapidly following the switch from phytophagy to predation by ancestral heteropterans, and then were retained over > 200 my of evolution. In contrast, trophic switches to blood-feeding (e.g. in Triatominae and Cimicidae) or reversions to plant-feeding (e.g., in Pentatomomorpha) were accompanied by rapid changes in the composition of venom/saliva, including the loss of many protein families.

Behavioural thermoregulation hastens spring mating activity in Pyrrhocoris apterus (Heteroptera: Pyrrhocoridae).

Post-diapause, overwintered adults of the true bug Pyrrhocoris apterus L. (Heteroptera, Pyrrhocoridae) form conspicuous aggregations at warm spots in early spring. Using a combination of laboratory experiments and field observations, we assessed the influence of this behaviour on the seasonal timing of reproduction. In the laboratory, post-diapause pairs mated after an accumulation of 80° days (dd), and females started to lay eggs after an additional 80 dd (considering 10.3 °C as a lower temperature threshold for post-diapause development). In the field, however, females mated as early as late March (based on data from four seasons), which corresponded to the accumulation of <15 dd (based on summing the temperatures recorded at a meteorology station). Such a 'discrepancy' between laboratory and field data is explained by thermoregulation. Aggregated adults bask in sunny spots, thereby increasing their body temperatures to ~25 °C, which is 7-16 °C above the temperature of the surrounding ground. This thermal excess speeds up their post-diapause development and enables early mating and oviposition. As a result, behavioural thermoregulation hastens the seasonal start of reproduction in P. apterus by > 1 month.

Compositional heterogeneity in true bug mitochondrial phylogenomics.

Mitochondrial phylogenomics is often controversial, in particular for inferring deep relationships. The recent rapid increase of mitochondrial genome data provides opportunities for better phylogenetic estimates and assessment of potential biases resulting from heterogeneity in nucleotide composition and mutation rates. Here, we gathered 76 mitochondrial genome sequences for Heteroptera representing all seven infraorders, including 17 newly sequenced mitochondrial genomes. We found strong heterogeneity in base composition and contrasting evolutionary rates among heteropteran mitochondrial genomes, which affected analyses with various datasets and partitioning schemes under site-homogeneous models and produced false groupings of unrelated taxa exhibiting similar base composition and accelerated evolutionary rates. Bayesian analyses using a site-heterogeneous mixture CAT+GTR model showed high congruence of topologies with the currently accepted phylogeny of Heteroptera. The results confirm the monophyly of the six infraorders within Heteroptera, except for Cimicomorpha which was recovered as two paraphyletic clades. The monophyly of Terheteroptera (Cimicomorpha and Pentatomomorpha) and Panheteroptera (Nepomorpha, Leptopodomorpha and Terheteroptera) was recovered demonstrating a significant improvement over previous studies using mitochondrial genome data. Our study shows the power of the site-heterogeneous mixture models for resolving phylogenetic relationships with Heteroptera and provides one more case showing that model adequacy is critical for accurate tree reconstruction in mitochondrial phylogenomics.

Habitat availability drives the distribution-abundance relationship in phytophagous true bugs in managed grasslands.

The nearly universal positive relationship between the distribution and abundance of species has been explained by several hypotheses but hitherto no consensus has been reached. Here, we used monitoring data of 105 phytophagous true bug species (Heteroptera) from 150 grassland sites over six years to test how (1) range position, (2) resource use, (3) resource availability, (4) density-dependent habitat selection, (5) metapopulation dynamics, and (6) habitat dispersal affect the distribution-abundance relationship. For the use in a confirmatory path analysis, we constructed causal pathways representing the hypothesized relationships and tested them separately and in a combined analysis. Our results show that the distribution-abundance relationship in phytophagous true bugs is driven by habitat-availability. An increasing local density of the host-plants increases the distribution of the species in the landscape, which in turn increases their local abundance. Thereby habitat availability facilitates dispersal success. We conclude that local abundance of herbivores facing habitat destruction could decline owing to a decrease in population dynamics between sites at the landscape scale. Finally, our results underline the potential of confirmatory path analysis for testing competing hypotheses.

Sperm dimorphism in the Triatoma brasiliensis species complex and its applications.

Morphological and structural features of the sperm of the Triatoma brasiliensis Neiva, 1911 (Hemiptera: Reduviidae) species complex were examined in this first study investigating the sperm of Heteroptera and the genus Triatoma. Males were dissected and their seminal vesicles removed. For measurement, seminal vesicles were squashed on glass slides, spread, fixed and observed under a photomicroscope. The images were analysed and measures of sperm were made. Data were analysed using one-way analysis of variance and Tukey's test to detect differentiation among taxa. Furthermore, seminal vesicles were prepared for studies of transmission electron microscopy. All taxa studied showed polymorphic (short and long) sperm. The sperm of Triatoma brasiliensis macromelasoma was significantly longer (in total length) than that of the other four members of the complex, which supports the hypothesis of hybrid speciation of this member of the complex as an increase in the size of typical hybrids under heterosis was previously shown. The sperm cells of the five taxa have similar ultrastructural morphology. The ultrastructural features observed confirm the hypothesis, raised by previous studies, that they are synapomorphic to the suborder Heteroptera.