Histology and histochemistry of the accessory gland of the female reproductive tract of Rhodnius neglectus Lent, 1954 (Hemiptera: Reduviidae).

Rhodnius neglectus is a wild triatomine, vector of the protozoan Trypanosoma cruzi, which causes Chagas' disease, and feeds on the blood of small mammals, being essential for its growth and reproduction. Accessory glands of the female reproductive tract are important in insect reproduction, but their anatomy and histology in R. neglectus are poorly studied. The aim of this work was to describe the histology and histochemistry of the accessory gland of the female reproductive tract of R. neglectus. The reproductive tract of five females of R. neglectus was dissected and the accessory glands transferred to Zamboni's fixative solution, dehydrated in a crescent series of ethanol, embedded in historesin, sectioned at 2 µm thick, stained with toluidine blue for histological analysis or mercury bromophenol blue for detection of total proteins. The accessory gland R. neglectus is tubular, without branches, opening in the dorsal region of the vagina and differing along its length in proximal and distal regions. In the proximal region, the gland is lined by the cuticle with a layer of columnar cells associated with muscle fibers. In the distal region of the gland, the epithelium has spherical secretory cells with terminal apparatus and conducting canaliculi opening in the lumen through pores in the cuticle. Proteins were identified in the gland lumen, terminal apparatus, nucleus and cytoplasm of secretory cells. The histology of the R. neglectus gland is similar to that found in other species of this genus, but with variations in the shape and size of its distal region.

Investigation of Rhodnius prolixus head anatomy using microtomography.

In the last years, microtomography has proved to be a powerful technique on insects' studies, allowing a detailed view of the structures' internal with a high resolution. One of the most important advantages about the use of microtomography in these studies is the fact that the dissection is not necessary, which decreases considerably the number of samples used on the insects' research. Some insects are used constantly in studies about morphology, metamorphosis, and reproduction, because they work as a model for others, and Rhodnius prolixus is one of the most studied in this group. This insect is also one of the main insect vectors of Chagas disease that kills around 12,000 people every year in Latin America. Some studies using laboratory microtomography conventional scanners combining with the correct staining methods have proved that it could be a powerful tool in biological research, allowing the visualisation of low-density tissues. The main goal of the present work was to use staining protocols to study Rhodnius prolixus with laboratory microtomography conventional scanners. The experiments were carried out at the imaging lab in the Theoretical Biology Department, University of Vienna, using an Xradia MicroXCT and at the University of Oslo, using a Skyscan 2211.

Microanatomical and secretory characterization of the salivary gland of the Rhodnius prolixus (Hemiptera, Reduviidae, Triatominae), a main vector of Chagas disease.

Rhodnius prolixus is the principal vector of Trypanosoma cruzi, the aetiological agent of Chagas disease in American countries. This insect is haematophagous during all life cycles and, to antagonize its haemostatic, inflammatory and immune systems, it secretes saliva while feeding on the vertebrate host's blood. Here, we investigated characteristic changes of the salivary glands (SG) that occur during insect development. Two pairs of lobules and ducts comprise the SG of R. prolixus. The organ's size increases over time, but the microanatomical structures are preserved during insect development. Both lobules have a single layer epithelium formed by binucleated cells, which surrounds the saliva reservoir. The principal lobule presents higher polysaccharide and total protein contents than the accessory lobe. A network of external muscle layers is responsible for organ contraction and saliva release. Apocrine, merocrine and holocrine secretion types occur in the secretory epithelium. Dopamine, serotonin and tyrosine-hydroxylase are neural-related molecules that regulate SG function both during and after feeding.

New findings on the functional morphology of the male genitalia of the blood-feeding bug Rhodnius prolixus in the light of a different observation on living tissue.

Among insect species, the male genitalia evolved many different anatomical features to ensure reproductive success. Males of primitive insects do not copulate but transfer sperm packaged in a spermatophore to the female, whereas males of the most advanced insects copulate and deliver free sperm to the storage organ, the spermatheca, in the female reproductive tract. Based on previous studies on several species of triatomine bugs (Rhodnius prolixus included), Triatominae are thought to use an intermediate form of sperm transfer in which the male genitalia have evolved to carry out both copulation and spermatophore formation. Previous observations on chemically fixed tissue of R. prolixus appear to show that the penis, the aedeagus, contains a much-folded internal cuticle which is a collapsed sac that everts from the aedeagus during copulation for the formation and delivery of the spermatophore directly to the female genital chamber. However, observations on living tissue of these structures in R. prolixus show that this internal cuticle functions as a tube through which male secretions pass through the aedeagus to the vagina. The organization of this cuticle in the context of the various anatomical structures of the aedeagus, its different morpho-functional meaning during sperm transfer in R. prolixus, the use of living versus chemically fixed tissue and a new understanding of previous observations are discussed.

Morphological and ultrastructural analysis of an important place of sexual communication of Rhodnius prolixus (Heteroptera: Reduviidae): the Metasternal Glands.

Rhodnius prolixus is an important vector of Trypanosoma cruzi, the etiological agent of Chagas disease. Insect adults have a pair of Metasternal Glands (MGs) and the secretion emitted by these glands acts as sex pheromone. Recent studies have focused on the chemical composition of this pheromone, electrophysiological responses to MGs compounds and mating behavior assays. Morphological studies of these glands are still scarce. Thus, considering the relevance of MGs in the sex pheromone biosynthesis, we investigated the morphology and ultrastructure of R. prolixus MGs. The glandular apparatus presents a tubular structure containing secretory cells with canalicules that fuse with the central duct which conducts the secretion to a pear-shaped reservoir connected to the exterior by a droplet-shape orifice. The secretory cells are classified as class III, they present a well-developed rough and smooth endoplasmic reticulum. Smooth endoplasmic reticulum is a site of lipid biosynthesis that may be involved in the mevalonate pathway, a probable route of the sex pheromone biosynthesis in this insect. The presence of rough endoplasmic reticulum indicates a possible peptides/proteins secretions site which were still not characterized in MGs. Several mitochondria are scattered in the cytoplasm that may suggest a high metabolic activity. Further studies should be carried out to correlate these data with the sex pheromone biosynthesis in this vector.

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.

Differentiation of Rhodnius neglectus and Rhodnius prolixus (Hemiptera: Reduviidae: Triatominae) by multiple parameters.

INTRODUCTION: The genus Rhodnius in the subfamily Triatominae comprises 20 species, which can transmit Trypanosoma cruzi and Trypanosoma rangeli. Due to the development of molecular techniques, Triatominae species can now be characterized by mitochondrial and nuclear markers, making it possible to verify and/or correct the existing data on these species. The results achieved in this study provide a more detailed and accurate differentiation of the Rhodnius species, helping the establishment of a more appropriate classification. METHODS: Data collection was performed by DNA analysis, morphological and morphometric studies to distinguish four populations of R. neglectus and four of R. prolixus. Phylogenetic data were compared to morphological and morphometric data. RESULTS: The analysis of Cytb fragments suggests that the four colonies designated to Rhodnius neglectus as well as those of R. prolixus were correctly identified. CONCLUSIONS: The morphological characters observed in the specimens of the colonies originally identified as R. prolixus and R. neglectus, such as the presence or absence of collar in the eggs, the patterns of the median process of the pygophore, and anterolateral angle, are consistent with the species. Geometric morphometrics also show an intraspecific variability in R. prolixus.

First report of Rhodnius montenegrensis (Hemiptera, Reduviidae, Triatominae) in Amazonas, Brazil.

INTRODUCTION: Triatomines are hematophagous insects of epidemiological importance because they are vectors of Chagas disease. We present here the first report of Rhodnius montenegrensis in Amazonas, Brazil. METHODS: Triatomines were collected from Attalea butyracea palm trees in the municipality of Guajará. RESULTS: Two adult female R. montenegrensis specimens were identified. CONCLUSIONS: The present study confirms that the number of triatomine species within the Amazon has increased from 10 to 11, and the number of Brazilian states with R. montenegrensis has increased from two to three.

First report of Rhodnius montenegrensis (Hemiptera, Reduviidae, Triatominae) in Amazonas, Brazil

Abstract INTRODUCTION: Triatomines are hematophagous insects of epidemiological importance because they are vectors of Chagas disease. We present here the first report of Rhodnius montenegrensis in Amazonas, Brazil. METHODS: Triatomines were collected from Attalea butyracea palm trees in the municipality of Guajará. RESULTS: Two adult female R. montenegrensis specimens were identified. CONCLUSIONS: The present study confirms that the number of triatomine species within the Amazon has increased from 10 to 11, and the number of Brazilian states with R. montenegrensis has increased from two to three.

Differentiation of Rhodnius neglectus and Rhodnius prolixus (Hemiptera: Reduviidae: Triatominae) by multiple parameters

Abstract Introduction: The genus Rhodnius in the subfamily Triatominae comprises 20 species, which can transmit Trypanosoma cruzi and Trypanosoma rangeli. Due to the development of molecular techniques, Triatominae species can now be characterized by mitochondrial and nuclear markers, making it possible to verify and/or correct the existing data on these species. The results achieved in this study provide a more detailed and accurate differentiation of the Rhodnius species, helping the establishment of a more appropriate classification. Methods: Data collection was performed by DNA analysis, morphological and morphometric studies to distinguish four populations of R. neglectus and four of R. prolixus. Phylogenetic data were compared to morphological and morphometric data. Results: The analysis of Cytb fragments suggests that the four colonies designated to Rhodnius neglectus as well as those of R. prolixus were correctly identified. Conclusions: The morphological characters observed in the specimens of the colonies originally identified as R. prolixus and R. neglectus, such as the presence or absence of collar in the eggs, the patterns of the median process of the pygophore, and anterolateral angle, are consistent with the species. Geometric morphometrics also show an intraspecific variability in R. prolixus.

First report of Rhodnius neglectus (Hemiptera, Reduviidae, Triatominae) from the State of Acre, Brazil, and the Brazilian Western Amazon Region.

INTRODUCTION: This communication reports the occurrence of Rhodnius neglectus in the State of Acre, Brazil. METHODS: An adult male R. neglectus specimen was collected from the Catuaba Experimental Reserve, which is located in the municipality of Senador Guiomard. RESULTS: This increases the number of triatomine species reported from the State of Acre to eight and is also the first report of R. neglectus from the Brazilian Western Amazon Region. CONCLUSIONS: The occurrence of R. neglectus is alarming because even though the species is wild, it can invade and colonize human dwellings and peridomiciles, thereby increasing Chagas disease transmission.

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.

First report of Rhodnius neglectus (Hemiptera, Reduviidae, Triatominae) from the State of Acre, Brazil, and the Brazilian Western Amazon Region

Abstract INTRODUCTION This communication reports the occurrence of Rhodnius neglectus in the State of Acre, Brazil. METHODS An adult male R. neglectus specimen was collected from the Catuaba Experimental Reserve, which is located in the municipality of Senador Guiomard. RESULTS This increases the number of triatomine species reported from the State of Acre to eight and is also the first report of R. neglectus from the Brazilian Western Amazon Region. CONCLUSIONS The occurrence of R. neglectus is alarming because even though the species is wild, it can invade and colonize human dwellings and peridomiciles, thereby increasing Chagas disease transmission.

Third record of Rhodnius amazonicus and comparative study with R. pictipes (Hemiptera, Reduviidae, Triatominae).

Rhodnius amazonicus Almeida et al. (1973) is a triatomine of rare occurrence. This species was found for the third time in Breves city, Pará state, Brazil. Morphometric and morphological studies were carried out on one male and one female. Lent and Wygodzinsky (1979) considered this species as a synonym of R. pictipes, until its revalidation after 23 years by Bérenger and Pluot-Sigwalt (2002). Considering the synonym mentioned above, a comparative study between these two species was performed in order to report the third encounter of this species, and increase the number of morphological characters that distinguish R. amazonicus from R. pictipes. The dorsal side of the head, the dorsal and ventral portions of the thorax, the dorsal, ventral and posterior sides of the female genitalia, eggs and the median process of the pygophore were examined by scanning electronic microscopy (SEM). The head, thorax, abdomen and egg parameters of these two species were also measured. The identification of characters on the head, stridulatory sulcus, mesosternum, metasternum, scutellum, process of urotergite I, external female genitalia, pygophore and eggs made the distinction between R. amazonicus and R. pictipes possible. This study has shown the new characters recorded and described for the first time for R. amazonicus and R. pictipes by SEM here made it possible to confirm the morphological separation between these two species. The morphometric analysis also confirmed that the above two taxa are different at specific level.

Phenotypic Variability of the Amazonian Species Rhodnius brethesi (Hemiptera: Reduviidae).

The wild species Rhodnius brethesi (Matta, 1919) (Hemiptera: Reduviidae) is found in areas of piassabais in microregion of Rio Negro, Amazonas, Brazil. Its geographical distribution overlaps the areas of Leopoldinia piassaba palm. In areas where palm trees are found, transmission cycle of Trypanosoma cruzi is related to the extractive activity of the palm fiber, exposing workers to wild vector transmission of this parasite. The close association with the palm tree L. piassaba suggests that this wild triatomine has special features in its sensory system allowing specificity of ecotope. The objective of the study is to identify the antennal sensilla phenotype and morphologically characterize the size and shape of the wings of wild R. brethesi, and to compare with the phenotype present in individuals reared in the laboratory. From the samples taken in the field, the presence of the species R. brethesi was found on both banks of the Rio Negro. The techniques used to verify the morphological patterns are important resources for observations of the triatomine populations, be they in an artificial or natural habitat.

First report of Rhodnius stali (Hemiptera, Reduviidae, Triatominae) in the State of Acre and in the Brazilian Amazon.

INTRODUCTION: This paper reports, for the first time, the presence of Rhodnius stali in the state of Acre and in the Brazilian Amazon. METHODS: Specimens of R. stali were collected by the Federal University of Acre in Rio Branco. RESULTS: The number of Triatominae species in the State of Acre increased from five to six. This was also the first report of R. stali in the Brazilian Amazon. CONCLUSIONS: The occurrence of R. stali is worrisome, since this species has been found naturally infected by Trypanosoma cruzi and there has been evidence of its domiciliation capabilities.

Ecdysis period of Rhodnius prolixus head investigated using phase contrast synchrotron microtomography.

Microtomography using synchrotron sources is a useful tool in biological imaging research since the phase coherence of synchrotron beams can be exploited to obtain images with high contrast resolution. This work is part of a series of works using phase contrast synchrotron microtomography in the study of Rhodnius prolixus head, the insect vector of Chagas' disease, responsible for about 12,000 deaths per year. The control of insect vector is the most efficient method to prevent this disease and studies have shown that the use of triflumuron, a chitin synthesis inhibitor, disrupted chitin synthesis during larval development and it's an alternative method against insect pests. The aim of this work was to investigate the biological effects of treatments with triflumuron in the ecdysis period (the moulting of the R. prolixus cuticle) using the new imaging beamline IMX at LNLS (Brazilian Synchrotron Light Laboratory). Nymphs of R. prolixus were taken from the Laboratory of Biochemistry and Physiology of Insects, Oswaldo Cruz Foundation, Brazil. Doses of 0.05mg of triflumuron were applied directly to the abdomen on half of the insects immediately after feeding. The insects were sacrificed 25days after feeding (intermoulting period) and fixed with glutaraldehyde. The results obtained using phase contrast synchrotron microtomography in R. prolixus showed amazing images of the effects of triflumuron on insects in the ecdysis period, and the formation of the new cuticle on those which were not treated with triflumuron. Both formation and malformation of this insect's cuticle have never been seen before with this technique.

First report of Rhodnius montenegrensis (Hemiptera, Reduviidae, Triatominae) in the State of Acre, Brazil

This paper reports, for the first time, the presence of Rhodnius montenegrensis in the State of Acre, Brazil.

First report of Rhodnius montenegrensis (Hemiptera, Reduviidae, Triatominae) in the State of Acre, Brazil.

INTRODUCTION: This paper reports, for the first time, the presence of Rhodnius montenegrensis in the State of Acre, Brazil. METHODS: Two female R. montenegrensis were collected in a dwelling in the rural area of Rio Branco, Acre, Brazil. RESULTS: The occurrence of this species was confirmed, and the number of Triatominae species in the State of Acre increased from four to five. CONCLUSIONS: Further studies should be performed to reach a clearer understanding of the ecology of this arthropod, its possible role in transmitting Chagas' disease and rangeliosis, and its current geographical distribution in the region.