Large-scale patterns in morphological diversity and species assemblages in Neotropical Triatominae (Heteroptera: Reduviidae).

We analysed the spatial variation in morphological diversity (MDiv) and species richness (SR) for 91 species of Neotropical Triatominae to determine the ecological relationships between SR and MDiv and to explore the roles that climate, productivity, environmental heterogeneity and the presence of biomes and rivers may play in the structuring of species assemblages. For each 110 km x 110 km-cell on a grid map of America, we determined the number of species (SR) and estimated the mean Gower index (MDiv) based on 12 morphological attributes. We performed bootstrapping analyses of species assemblages to identify whether those assemblages were more similar or dissimilar in their morphology than expected by chance. We applied a multi-model selection procedure and spatial explicit analyses to account for the association of diversity-environment relationships. MDiv and SR both showed a latitudinal gradient, although each peaked at different locations and were thus not strictly spatially congruent. SR decreased with temperature variability and MDiv increased with mean temperature, suggesting a predominant role for ambient energy in determining Triatominae diversity. Species that were more similar than expected by chance co-occurred near the limits of the Triatominae distribution in association with changes in environmental variables. Environmental filtering may underlie the structuring of species assemblages near their distributional limits.

Revalidation and redescription of Triatoma brasiliensis macromelasoma Galvão, 1956 and an identification key for the Triatoma brasiliensis complex (Hemiptera: Reduviidae: Triatominae).

Triatoma brasiliensis macromelasoma is revalidated based on the results of previous multidisciplinary studies on the Triatoma brasiliensis complex, consisting of crossing experiments and morphological, biological, ecological and molecular analyses. These taxonomic tools showed the closest relationship between T. b. macromelasoma and Triatoma brasiliensis brasiliensis. T. b. macromelasoma is redescribed based on specimens collected in the type locality and specimens from a F1 colony. The complex now comprises T. b. brasiliensis, T. b. macromelasoma, Triatoma melanica, Triatoma juazeirensis and Triatoma sherlocki. An identification key for all members of the complex is presented. This detailed comparative study of the morphological features of T. b. macromelasoma and the remaining members of the complex corroborates results from multidisciplinary analyses, suggesting that the subspecific status is applicable. This subspecies can be distinguished by the following combination of features: a pronotum with 1+1 narrow brownish-yellow stripes on the submedian carinae, not attaining its apex, hemelytra with membrane cells darkened on the central portion and legs with an incomplete brownish-yellow ring on the apical half of the femora. Because the T. brasiliensis complex is of distinct epidemiological importance throughout its geographic distribution, a precise identification of its five members is important for monitoring and controlling actions against Chagas disease transmission.

Description of the male genitalia of Belminus rugulosus Stål and Belminus corredori Galvão & Angulo, and comments on the holotype of Parabelminus yurupucu Lent & Wygodzinsky (Hemiptera: Heteroptera: Reduviidae: Triatominae: Bolboderini).

The male genitalia of Belminus rugulosus Stål and Belminus corredori Galvão & Angulo are described and illustrated for the first time. Comments on the holotype of Parabelminus yurupucu Lent & Wygodzinsky are presented (Hemiptera: Heteroptera: Reduviidae: Triatominae: Bolboderini). A discussion on previous data in the literature on male genitalia of species of Belminus Stål is provided.

New in morphometry: Geometric morphometry of the external female genitalia of Triatominae (Hemiptera: Reduviidae).

The study of geometric morphometry has an impact on Triatominae studies. Currently, several taxonomic and systematic studies use this approach. The Triatominae subfamily comprises three fossil species and 154 extant species potentially capable of transmitting Trypanosoma cruzi, the causative agent of Chagas disease. This study aims to evaluate the external female genitalia of adult triatomines using multivariate geometric morphometric approaches, not only for validation but also for systematic inferences. Specimens belonging to the genera Panstrongylus, Psammolestes, Rhodnius, and Triatoma were evaluated, in addition to two species previously included in Triatoma: T. longipennis and T. phyllosoma. The results show that the external female genitalia have operational morphology and allow characterization of the species and the genera of the Triatominae. In addition, the multivariate technique enabled delimitation of the phylogenetic relationships of the subfamily, presenting results consistent with systematic studies. It can be concluded that the external female genitalia evaluated by geometric morphometry is a useful character for the taxonomy and systematics of Triatominae.

Biological and genetic aspects of crosses between species of the genus Meccus (Hemiptera: Reduviidae Triatominae).

The degree of reproductive isolation between Meccus phyllosomus and the remaining five species of the genus Meccus, as well as between Meccus bassolsae and Meccus pallidipennis, Meccus longipennis and Meccus picturatus, was examined. Fertility and the segregation of morphological characteristics were examined in two generations of hybrids from crosses between these species. The percentage of couples with offspring (fertile) was high in the vast majority of sets of crosses, with the exception of that between ♀M. phyllosomus and ♂Meccus mazzottii. In sets of crosses involving M. bassolsae specimens, no first-generation (F1) individuals were morphologically similar to M. bassolsae, but instead shared the morphology of the other parental species. A similar phenomenon was observed in most sets of crosses involving M. phyllosomus. These results indicated that different degrees of reproductive isolation exist among the species of Meccus involved in this study. The biological evidence obtained in this study does not support the proposal that M. bassolsae is a full species. It could indicate that, on the contrary, it should be considered a subspecies of a single polytypic species. The biological evidence does support the proposal that M. phyllosomus is a full species.

Chagas Disease Vectors of Espírito Santo, Brazil: First Report of Triatoma infestans (Klug, 1834) (Hemiptera, Triatominae) in the Brazilian State and Development of an Identification Key Based on Cytogenetic Data.

Chagas disease is a potentially life-threatening illness caused by the protozoan Trypanosoma cruzi and transmitted, mainly, by hematophagous insects of the Triatominae subfamily. In Brazil, there are currently about 66 triatomine species distributed throughout the country's 27 states. Triatoma infestans is considered as a species of great vectorial importance, mainly because of its biological characteristics, such as the high degree of anthropophilia, adaptation to the home environment, ability to withstand long periods of fasting, and present a wide geographical distribution. Taking into account the epidemiological importance of these species, we carried out the first report of T. infestans in the Espírito Santo, Brazil, and development of an identification key for all species notified in that state, based on cytogenetic data. This information is important because they contribute to the direction of epidemiological surveillance activities carried out by vector control programs of the Espírito Santo, Brazil.

Under pressure: phenotypic divergence and convergence associated with microhabitat adaptations in Triatominae.

BACKGROUND: Triatomine bugs, the vectors of Chagas disease, associate with vertebrate hosts in highly diverse ecotopes. It has been proposed that occupation of new microhabitats may trigger selection for distinct phenotypic variants in these blood-sucking bugs. Although understanding phenotypic variation is key to the study of adaptive evolution and central to phenotype-based taxonomy, the drivers of phenotypic change and diversity in triatomines remain poorly understood. METHODS/RESULTS: We combined a detailed phenotypic appraisal (including morphology and morphometrics) with mitochondrial cytb and nuclear ITS2 DNA sequence analyses to study Rhodnius ecuadoriensis populations from across the species' range. We found three major, naked-eye phenotypic variants. Southern-Andean bugs primarily from vertebrate-nest microhabitats (Ecuador/Peru) are typical, light-colored, small bugs with short heads/wings. Northern-Andean bugs from wet-forest palms (Ecuador) are dark, large bugs with long heads/wings. Finally, northern-lowland bugs primarily from dry-forest palms (Ecuador) are light-colored and medium-sized. Wing and (size-free) head shapes are similar across Ecuadorian populations, regardless of habitat or phenotype, but distinct in Peruvian bugs. Bayesian phylogenetic and multispecies-coalescent DNA sequence analyses strongly suggest that Ecuadorian and Peruvian populations are two independently evolving lineages, with little within-lineage phylogeographic structuring or differentiation. CONCLUSIONS: We report sharp naked-eye phenotypic divergence of genetically similar Ecuadorian R. ecuadoriensis (nest-dwelling southern-Andean vs palm-dwelling northern bugs; and palm-dwelling Andean vs lowland), and sharp naked-eye phenotypic similarity of typical, yet genetically distinct, southern-Andean bugs primarily from vertebrate-nest (but not palm) microhabitats. This remarkable phenotypic diversity within a single nominal species likely stems from microhabitat adaptations possibly involving predator-driven selection (yielding substrate-matching camouflage coloration) and a shift from palm-crown to vertebrate-nest microhabitats (yielding smaller bodies and shorter and stouter heads). These findings shed new light on the origins of phenotypic diversity in triatomines, warn against excess reliance on phenotype-based triatomine-bug taxonomy, and confirm the Triatominae as an informative model system for the study of phenotypic change under ecological pressure .

TriatoDex, an electronic identification key to the Triatominae (Hemiptera: Reduviidae), vectors of Chagas disease: Development, description, and performance.

Correct identification of triatomine bugs is crucial for Chagas disease surveillance, yet available taxonomic keys are outdated, incomplete, or both. Here we present TriatoDex, an Android app-based pictorial, annotated, polytomous key to the Triatominae. TriatoDex was developed using Android Studio and tested by 27 Brazilian users. Each user received a box with pinned, number-labeled, adult triatomines (33 species in total) and was asked to identify each bug to the species level. We used generalized linear mixed models (with user- and species-ID random effects) and information-theoretic model evaluation/averaging to investigate TriatoDex performance. TriatoDex encompasses 79 questions and 554 images of the 150 triatomine-bug species described worldwide up to 2017. TriatoDex-based identification was correct in 78.9% of 824 tasks. TriatoDex performed better in the hands of trained taxonomists (93.3% vs. 72.7% correct identifications; model-averaged, adjusted odds ratio 5.96, 95% confidence interval [CI] 3.09-11.48). In contrast, user age, gender, primary job (including academic research/teaching or disease surveillance), workplace (including universities, a reference laboratory for triatomine-bug taxonomy, or disease-surveillance units), and basic training (from high school to biology) all had negligible effects on TriatoDex performance. Our analyses also suggest that, as TriatoDex results accrue to cover more taxa, they may help pinpoint triatomine-bug species that are consistently harder (than average) to identify. In a pilot comparison with a standard, printed key (370 tasks by seven users), TriatoDex performed similarly (84.5% correct assignments, CI 68.9-94.0%), but identification was 32.8% (CI 24.7-40.1%) faster on average-for a mean absolute saving of ~2.3 minutes per bug-identification task. TriatoDex holds much promise as a handy, flexible, and reliable tool for triatomine-bug identification; an updated iOS/Android version is under development. We expect that, with continuous refinement derived from evolving knowledge and user feedback, TriatoDex will substantially help strengthen both entomological surveillance and research on Chagas disease vectors.

New report of Eratyrus cuspidatus Stål, 1859 (Hemiptera: Reduviidae: Triatominae) in the State of Campeche, Mexico.

INTRODUCTION: Triatomine bugs are vectors of Trypanosoma cruzi, the etiological agent of Chagas disease. METHODS: Triatomine bugs were collected and identified following established protocols. In addition, infection with T. cruzi was detected by microscopic and molecular analysis. RESULTS: We captured an adult male specimen of the Eratyrus cuspidatus species that has not been reported in the state of Campeche. CONCLUSIONS: This finding provides new information on the distribution of E. cuspidatus in Mexico. However, more studies are needed to determine their epidemiological significance.

Structure and function of the stylets of hematophagous Triatominae (Hemiptera: Reduviidae), with special reference to Dipetalogaster maxima.

Kissing bugs (Hemiptera: Reduviidae: Triatominae) are able to bend their rod-like maxillae while searching for blood vessels in the tissue of their vertebrate hosts. Little is known about the working mechanisms of these bending movements and the distal opening of the food channel. We compared the morphological structure of the stylets (mandibles and maxillae) of four triatomine species and analyzed the feeding process of Dipetalogaster maxima (Uhler, 1894). The maxillae of triatomine bugs are interlocked by a tongue-and-groove system, allowing longitudinal sliding. While penetrating the host tissue, the animals perform rapid alternate back and forth movements of the maxillae. The resistance of the surrounding tissue pushes the asymmetric apex of the maxillae away from its straight path, i.e., if one individual maxilla is protracted alone, its tip curves inwards, and the other maxilla follows. Once a blood vessel is tapped, the spine-like tip of the left maxilla splays outwards. Apically, each of the maxillae features an abutment, the left one exhibiting a notch that presumably facilitates splaying. The mechanical interaction of the two maxillary abutments enables the distal opening of the food channel but might also support the movements of the maxillary bundle attributable to different bending moment distributions.

Morphological description of Mepraia spp. females (Hemiptera: Reduviidae, Triatominae).

Mepraia spinolai, M. gajardoi and M. parapatrica occur in distinct regions in Chile. The females of the three species are micropterous. The males of M. gajardoi are brachypterous, those of M. parapatrica can be brachypterous or macropterous and those of M. spinolai can be micropterous, brachypterous or macropterous. Morphological studies were carried out by scanning electron microscopy of female specimens collected in the wild. Head, thorax and abdomen characters of the three species there were not previously studied by SEM allowed a clear distinction amongst the three species.

Genital morphology and copulatory behavior in triatomine bugs (Reduviidae: Triatominae).

Triatomines (Heteroptera: Reduviidae) include around 139 species, widely known as vectors of Chagas disease. Our aim is to review the existing knowledge of the genital morphology and sexual behavior and provide some functional analysis of these traits in triatomines. A complex set of traits comprise genitalia and these are highly variable among species. The components of the phallus and seminal products (secreted by action of testes and two accessory glands) interact to allow successful sperm transfer to the female spermathecae (usually a pair of blind tubes that emerge from the common oviduct). Seminal products may inhibit female physiology and extend mating duration. Mating behavior in triatomines is best characterized as scramble competition. We suggest that males may evaluate female condition prior to copulation, given that female fitness is largely affected by food (blood) source. Although rearing several triatomine species may be difficult and discourage from undertaking studies on this group, any further investigation on sexual behavior and mating interactions may provide data for applicative studies including Chagas disease vectors control.

Comparative Study of the Antennal Phenotype in Species of the Belminus (Hemiptera: Triatominae) Genus Using Optical and Scanning Electron Microscopy.

The genus Belminus Stål, 1859 is distinguished by markedly entomophagous species. This genus is a poorly studied group of the Triatominae (Jeannel, 1919), which includes hematophagous species that are vectors of Trypanosoma cruzi (Chagas, 1909), the etiological agent of Chagas disease. This study reports for the first time the description of the antennal sensilla of Belminus corredori (Galvão & Angulo, 2003), Belminus herreri (Lent & Wygodzinsky, 1979), and Belminus ferroae (Sandoval, Pabón, Jurberg & Galvão, 2007) nymphs and adults throughout scanning electron microscopy and optical microscopy. Nine morphological types of sensilla were identified in the three species, including bristles I and II, trichobothria, tapered hairs, thin-walled trichoid, thick-walled trichoid, basiconic, campaniform, and coeloconica sensilla. The analysis of the most abundant types of sensilla and their distribution in nymphs and adults shows similarities with the antennal phenotypes described in other Triatominae. Quantitative differences showed the important phenotypic plasticity of this morphological trait in the genus and allowed for the separation of the species in both sexes. These differences were associated with sexual dimorphism and wing condition (macropterous and brachypterous). The role of the antennal phenotype in sexual behavior, its usefulness as a taxonomic tool, and its relationship with the dispersal capacity of these species are discussed.

Spermathecae: Morphofunctional features and correlation with fat bodies and trachea in six species of vectors of Chagas disease.

Since spermatheca is able to transport spermatozoa and maintain a specific microenvironment for the storage of viable sperm cells for long periods of time, specific morphofunctional features must be involved in this capacity, and an efficient nutritional and oxygen supply must be required. In this study, we investigated the histological features of spermathecae and fat bodies in six species of three genera of epidemiological importance for Chagas' disease. The association of the reproductive system with the fat bodies and tracheal system was also focused in these species. The reproductive system, tracheae and fat bodies were fixed in 4% formaldehyde, and embedded in glycol methacrylate. The sections were stained with H.E., picrosirius red and Periodic-Acid Schiff methods for morphological analyses. Paraffin-embedded spermatheca sections were submitted to immunofluorescence for detection of V-ATPase. In P. lignarius, R. montenegrensis and R. prolixus, the spermatheca contains a slightly dilated tubular distal portion. In P. megistus and T. tibiamaculata, the spermatheca shows a large bulbous distal portion, and in T. infestans, a large oval-shaped distal portion. In all species, this portion was surrounded by a thin muscular layer, and the epithelial height varied according to the shape of this terminal portion. All spermathecal proximal portions showed simple columnar epithelium surrounded by a thick muscular layer. The epithelial cells of spermathecae showed PAS-positive cytoplasm and V-ATPase immunofluorescence in the apical surface. Tracheoles and polysaccharide-rich fat body cells were found next or in close contact to the oviduct or spermathecal tissues. The results indicate that the spermatheca proximal portion is related to contraction and sperm transport, whose oxygen and energy supply is guaranteed by the associated tracheal branches and fat bodies. In the storage portion, fat bodies and tracheae seem to be crucial for the maintenance of an optimal spermathecal microenvironment and storage of viable sperm cells. The participation of V-ATPase in the spermathecae epithelial cells may contribute for the maintenance of an optimal luminal milieu to spermatozoa, by alkalinization and/or acidification of lumen, similarly to the other epithelial cell types in insects. Further studies are necessary to clarify the role of this proton pump in the spermathecal epithelial cells.

The Interspecific Hemelytra Differences Among Mepraia Species Males (Hemiptera, Reduviidae:Triatominae) in Chile.

The species of the genus Mepraia Mazza, Gajardo Tobar and Jörg (Hemiptera, Reduviidae:Triatominae) exhibit polymorphism in their hemelytra. The females of all species are always micropterous, but the males can be micropterous, brachypterous, or macropterous. Mepraia gajardoi Frías, Henry and González (Hemiptera: Reduviidae) males are always brachypterous, Mepraia parapatrica Frías-Lasserre (Hemiptera: Reduviidae) males are macropterous or brachypterous and Mepraia spinolai (Porter) (Hemiptera: Reduviidae) males are macropterous, brachypterous, or micropterous. Here, we determined distinctive characteristics of the hemelytra of the males of these three species and found that the length of the hemelytra of the brachypterous males in these three species differs statistically, as does their shape and morphology. These differences are particularly apparent at the apex of the hemelytra, the anterior part of the corium, in the morphology and number of the ctenidia of coaptors, and presence or absence of the cross vein of the hemelytra. Based on this, we propose a key based on hemelytra characteristics to identify the males of the three Mepraia species.

Morphology of the terminal abdominal segments in females of Triatominae (Insecta: Hemiptera: Reduviidae).

Triatominae (Insecta: Hemiptera: Reduviidae) includes 151 extant species that are all potential vectors of Chagas disease. The relationships among these species have been recently studied based on molecular and cytogenetical approaches, and although the morphology of these insects is fairly described, wide comparative studies and cladistics analysis based on this feature are lacking. A comparative study of the terminal abdominal segments in females of 26 species of Triatominae was performed in order to evaluate their importance for the distinction of genera and species, and obtain characters to be used in cladistics analyses. The results showed that the short combined segments IX and X in dorsal view is not diagnostic for Rhodnius, and the elongated trapezoidal dorsal shape of combined segments IX and X is not exclusive of Panstrongylus. There are diagnostic features at the generic level for Rhodnius and Dipetalogaster, but not for the other genera studied. Among the structures examined, tergite IX is the most valuable for distinguishing species of Triatominae. The female terminalia is useful for the specific identification of Triatominae, but cannot be used to diagnose most genera or to directly assess supraspecific relationships. These can only be unveiled by using additional morphological and/or molecular data in broad cladistics analyses.

External female genitalia of six species of the genus Meccus (Hemiptera: Reduviidae: Triatominae).

Triatomine classification is based on morphological characteristics. Studies have been conducted to improve their identification by observing many characteristics. However, there are problems of differentiating among highly interrelated species and new criteria are required. The purpose of this study was to determine the morphological differences in the external female genitalia of M. pallidipennis, M. longipennis, M. picturatus, M. bassolsae, M. mazzottii, and M. phyllosomus in order to distinguish among species using scanning electron microscopy. Observations were made of the dorsal, posterior, lateral, and ventral views of the female external genitalia for each species. In the six species we studied, relevant differences were observed in the dorsal view of the X segment, as well as the IX, VIII, and VII tergites. In the posterior and lateral view, the most visible differences were registered in the gonocoxite size of the segments VIII, IX, and X. Finally, in the ventral view of the VII sternite, differences among species were observed in the size of the inflection in the top and upper corner. Our results show that it was possible to differentiate among the triatominae species for each of the four views by using a scanning electron microscope to analyze morphological characteristics of the VII, VIII, IX, and X abdomen segments.

Morphology of the spermathecae of twelve species of Triatominae (Hemiptera, Reduviidae) vectors of Chagas disease.

Trypanosoma cruzi, the etiological agent of Chagas disease, is transmitted by triatomines that have been described in a large number of studies. Most of those studies are related to external morphology and taxonomy, but some biochemical, genetic and physiological studies have also been published. There are a few publications in the literature about the internal organs of Triatominae, for instance the spermathecae, which are responsible for storing and maintaining the viability of the spermatozoids until the fertilization of the oocytes. This work aims to study the spermathecae of twelve species of triatomines obtained from the Triatominae Insectarium of the Faculty of Pharmaceutical Sciences, UNESP, Araraquara, using optical microscopy and scanning electron microscopy. The spermathecae of the twelve species studied showed three morphological patterns: a) P. herreri sn, P. lignarius, P. megistus, Triatoma brasiliensis, T. juazeirensis, T. sherlocki and T. tibiamaculata have spermathecae with a thin initial portion and an oval-shaped final portion; b) R. montenegrensis, R. nasutus, R. neglectus, R. pictipes and R. prolixus have tubular and winding spermathecae; c) T. infestans has oval spermathecae. In addition to the three morphological patterns, it was noted that each of the twelve species has particular features that differentiate them.

Study of the Salivary Glands in Triatominae (Hemiptera, Reduviidae, Triatominae): Their Color and Application to the Chagas Disease Vector Evolution.

Chagas disease is caused by Trypanosoma cruzi and transmitted by feces of a triatomine that has the habit of defecating during blood feeding. The salivary glands of triatomines are important to hematophagy because their saliva is rich in anticoagulant and hemolytic proteins. The salivary glands of some Rhodnius species analyzed are reddish due to the presence of nitrophorins (antihemostatic activity). The present study aimed to analyze the color pattern of the salivary glands of 67 triatomine species to evaluate whether the presence of nitrophorins is a synapomorphy of Rhodnius or the tribe Rhodniini, or if it is shared with triatomines of the tribes Triatomini and Cavernicolini. Since only the species of the tribe Rhoniini present red glands, it is admitted that the presence of nitrophorin proteins is a synapomorphy of the tribe Rhodniini and that this tribe has derived more recently when compared with Triatomini and Cavernicolini.

Wing Polymorphism and Trypanosoma cruzi Infection in Wild, Peridomestic, and Domestic Collections of Mepraia spinolai (Hemiptera: Reduviidae) From Chile.

Mepraia spinolai (Porter) is a vector of Trypanosoma cruzi that causes Chagas disease. Females are always wingless, but males may be winged or wingless. We determined by PCR the infection percentage with T. cruzi of M. spinolai adults and nymphs in domestic, peridomestic, and wild collections, in different regions of Chile. In all regions, winged males were more abundant than females and wingless males. Winged males collected inside houses were less parasitized than were those from peridomestic and wild environments. Although winged males of M. spinolai have comparatively low levels of infection, this segment may still represent the greatest vector threat in this species for transmission of T. cruzi to humans and other vertebrates in domestic, wild, and peridomestic habitats. Winged males represent the dispersive form of this species that invades human dwellings. Feeding deprivation resulting from the time required to find a food source and to search for reproductive females could explain the lower infection rates (negatives) of winged males collected from inside houses in comparison with winged males collected from peridomestic and wild habitats.