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.

Ultrastructural analysis of the nucleolar aspects at spermiogenesis in triatomines (Heteroptera, Triatominae).

In this study the ultrastructural technique was used to analyze seminiferous tubule cells of the triatomine species Panstrongylus megistus, Rhodnius pallescens and Triatoma infestans. The data obtained provided evidence of the phenomenon known as persistence of the nucleolar material in initial spermatids at early differentiation. Our results confirmed the presence of the nucleolus and its products during spermiogenesis up to the formation of the axoneme and during spermatid elongation in all three species studied, similar to the process that takes place during cell division. In early spermatids, the nucleoli had a reticulate appearance and a well defined nucleolonema in P. megistus; showed a clear distinction between the fibrillar and the granular component in T. infestans; and had a compact aspect in R. pallescens. In this study, ultrastructural analyses at spermiogenesis indicated that these nucleolar products may represent RNP complexes that will probably be needed at early spermiogenesis when important changes such as chromatin condensation and acrosome and flagellum formation take place. Therefore, it was concluded from the ultrastructural analysis that the triatomine nucleolus does not totally disappear but remains as corpuscles that gather to form the next nucleolar cycle that in the case of meiosis, will be completed if fertilization occurs and a zygote is formed.

Characterization of the external female genitalia of six species of Triatominae (Hemiptera: Reduviidade) by scanning electron microscopy.

By macroscopic and microscopic dorsal side observation, it was noted that the IX and X segments of two species each of Panstrongylus and Triatoma terminate in an elongated way, whereas they terminate abruptly in the two species of Rhodnius. Scanning observation of the dorsal, ventral, lateral and posterior sides of the female genitalia of Panstrongylus herreri, Panstrongylus megistus, Rhodnius colombiensis, Rhodnius prolixus, Triatoma infestans and Triatoma vitticeps revealed that these six species are generally and specifically distinguished based on these elements. We describe several components that distinguish P. herreri from P. megistus: four on the dorsal side: the VII, VIII, IX and X segments, on the ventral view, three: VII sternite, VIII gonocoxite and VIII gonapophyse, on the lateral view one character, VIII gonocoxite and on the posterior view three characters: VIII and IX gonocoxite and XI gonopophyse. Comparing R. colombiensis and R. prolixus, there were three distinct characters on the dorsal side: the VII, VIII and X segments, on the ventral view three characters: the IX and X segments and VIII gonocoxite and on the posterior view four characters: the VIII, IX, X segments and VIII gonapophyse that distinguish the two species. T. infestans and T. vitticeps have four different characters on the dorsal side: the VII, VIII, IX and X segments, on the ventral view four characters: the VII and X segments, VIII gonocoxite and VIII gonapophyse, on the lateral view two characters, IX and X segments and on the posterior view four characters: the IX and X segments, VIII gonocoxite and VIII gonapophyse that distinguish the two species. Examination of the external female genitalia of six triatomine species by scanning suggests that these components are useful for taxonomical studies.

Characterization of the external female genitalia of six species of Triatominae (Hemiptera: Reduviidade) by scanning electron microscopy

By macroscopic and microscopic dorsal side observation, it was noted that the IX and X segments of two species each of Panstrongylus and Triatoma terminate in an elongated way, whereas they terminate abruptly in the two species of Rhodnius. Scanning observation of the dorsal, ventral, lateral and posterior sides of the female genitalia of Panstrongylus herreri, Panstrongylus megistus, Rhodnius colombiensis, Rhodnius prolixus, Triatoma infestans and Triatoma vitticeps revealed that these six species are generally and specifically distinguished based on these elements. We describe several components that distinguish P. herreri from P. megistus: four on the dorsal side: the VII, VIII, IX and X segments, on the ventral view, three: VII sternite, VIII gonocoxite and VIII gonapophyse, on the lateral view one character, VIII gonocoxite and on the posterior view three characters: VIII and IX gonocoxite and XI gonopophyse. Comparing R. colombiensis and R. prolixus, there were three distinct characters on the dorsal side: the VII, VIII and X segments, on the ventral view three characters: the IX and X segments and VIII gonocoxite and on the posterior view four characters: the VIII, IX, X segments and VIII gonapophyse that distinguish the two species. T. infestans and T. vitticeps have four different characters on the dorsal side: the VII, VIII, IX and X segments, on the ventral view four characters: the VII and X segments, VIII gonocoxite and VIII gonapophyse, on the lateral view two characters, IX and X segments and on the posterior view four characters: the IX and X segments, VIII gonocoxite and VIII gonapophyse that distinguish the two species. Examination of the external female genitalia of six triatomine species by scanning suggests that these components are useful for taxonomical studies.

Cytochemical characterization of Triatoma infestans and Panstrongylus megistus salivary gland cells (Hemiptera, Reduviidae, Triatominae).

The Triatominae subfamily has medical sanitary importance, since these insects are vectors of Trypanosoma cruzi, etiologic agent of Chagas Disease, and Trypanosoma rangeli, which develops in the salivary glands and it is frequently found in mixed infections with T. cruzi. Triatomines of Triatoma and Panstrongylus genera possess a salivary gland complex composed of a pair with three well differentiated units: the anterior (D1), median (D2) and posterior (D3). Saliva is secreted during blood meal and antagonizes hemostatic, inflammatory and immunological systems imposed by the host, which facilitate the hematophagy. In order to identify nuclear structures, we studied interphase nuclei of salivary gland cells of adult insects, males and females, of Triatoma infestans and Panstrongylus megistus. The glands were removed from insects, fixed in acetic acid (45%) and lactic acid (50%), squashed and submitted to different cytochemical methods: lacto-acetic orcein, silver ion impregnation, Feulgen reaction, Toluidine Blue, Variant method of critical electrolyte concentration and C-banding. The preparations were examined with a Zeiss Jenaval photomicroscope and photographed. The results evidenced predominance of binucleated cells in D1 and D2 glands and mononucleated ones in D3. In all salivary glands were observed bulky and polyploid nucleus, a clear association between nucleolar and heterochromatic corpuscles, cytoplasmatic metachromasy and many pre-secretion vesicles in cytoplasm. Such characteristics were associated with intense synthesis activity to produce the saliva. Species were mainly differentiated by a larger heterochromatic corpuscle observed only in T. infestans (called as chromocenter), while P. megistus showed a predominance of euchromatin, with some heterochromatic corpuscles just in males. Females of both species showed a smaller quantity of heterochromatin, which could be related to the high metabolism because of the oviposition.

Stridulatory sound emission of Panstrongylus rufotuberculatus Champion, 1899, (Hemiptera: Reduviidae: Triatominae).

This study contains the first report of stridulatory sound observed in Panstrongylus rufotuberculatus Champion, 1899, and also a new record of this species in Venezuela. The conditions in which stridulation occurred are described, as well as the general environmental characteristics of the localities where it was found. This triatomine only performs the sound in conditions of extreme provocation.

Stridulatory sound emission of Panstrongylus rufotuberculatus Champion, 1899, (Hemiptera: Reduviidae: Triatominae)

Este estudo contém o primeiro reporte da estridulação observada em Panstrongylus rufotuberculatus Champion, 1899, e um novo registro desta espécie na Venezuela. Descrevem-se as condições em que ocorre a estridulação, como também as características gerais das localidades onde foi capturado. Este triatomino só emite som em condições de extrema provocação.

Diferença no tamanho de cascas de ovos de colônias de Panstrongylus megistus / Differences in the size of eggshells among three Pangstrongylus megistus colonies

O objetivo do estudo foi avaliar as mensuraçöes de cascas de ovos de duas colônias laboratoriais e uma silvestre de P. megistus. De cada uma das colônias, 50 cascas de ovos foram mensuradas por meio de microscópio estereoscópico e sistema de análise de imagem QWin. A análise estatística foi efetuada utilizando o teste t-Student, näo pareado no programa INSTAT. A largura, o comprimento e o diâmetro da abertura opercular das cascas de ovos de uma colônia silvestre foram maiores que de duas colônias laboratoriais de P. megistus

Nuclear phenotype changes after heat shock in Panstrongylus megistus (Burmeister).

The nuclear phenotypes of Malpighian tubule epithelial cells of male nymphs of the blood-sucking insect, Panstrongylus megistus, subjected to short- and long-duration heat shocks at 40oC were analyzed immediately after the shock and 10 and 30 days later. Normal nuclei with a usual heterochromatic body as well as phenotypes indicative of survival (unravelled heterochromatin, giants) and death (apoptosis, necrosis) responses were observed in control and treated specimens. However, all nuclear phenotypes, except the normal ones, were more frequent in shocked specimens. Similarly altered phenotypes have also been reported in Triatoma infestans following heat shock, although at different frequencies. The frequency of the various nuclear phenotypes observed in this study suggests that the forms of cell survival observed were not sufficient or efficient enough to protect all of the Malpighian tubule cells from the deleterious effects of stress. In agreement with studies on P. megistus survival following heat shock, only long-duration shock produced strongly deleterious effects.

Scanning electron microscopy of the dorsal vessel of Panstrongylus megistus (Burmeister, 1835) (Hemiptera: Reduviidae)

In this study we analyzed the microanatomy of the dorsal vessel of the triatomine Panstrongylus megistus. The organ is a tuble anatomically divided into an anterior aorta anad a posterior heart, connected to the body wall through 8 pairs of alary muscles. The heart is divided in 3 chambers by means of 2 pairs of cardiac valves. a pair of ostia can be observed in the lateral wall of each chamber. A bundle of nerve fibers was found outside the organ, running dorsally along its major axis. A group of longitudinal muscular fibers was found in the ventral portion of the vessel. The vessel was found to be lined both internally and externally by pericardial cells covered by a thin laminar membrane. Inseide the vessel the pericardial cells were disposed in layers and on the outside they formed clusters or rows

Scanning electron microscopy of the dorsal vessel of Panstrongylus megistus (Burmeister, 1835) (Hemiptera: Reduviidae).

In this study we analyzed the microanatomy of the dorsal vessel of the triatomine Panstrongylus megistus. The organ is a tubule anatomically divided into an anterior aorta and a posterior heart, connected to the body wall through 8 pairs of alary muscles. The heart is divided in 3 chambers by means of 2 pairs of cardiac valves. A pair of ostia can be observed in the lateral wall of each chamber. A bundle of nerve fibers was found outside the organ, running dorsally along its major axis. A group of longitudinal muscular fibers was found in the ventral portion of the vessel. The vessel was found to be lined both internally and externally by pericardial cells covered by a thin laminar membrane. Inside the vessel the pericardial cells were disposed in layers and on the outside they formed clusters or rows.

Histogical and ultrastructural aspects of the brindley's glands of pantrongylus megistus (Burmeister, 1835) (Hemiptera: Reduviidae)

The Brindley's glands of Panstrongylus megistus were studied under the antomic, histologic and ultrastructural point of view. These glands located in the insect's methatorax are paired and have an opening near the third parir of the feet. Beside this aperture, ther are evaporation areas. Shape, sixe and aspect of the gland vary according to the feeding status. The glands are composed by a tubular part corresponding to the duct and a sack-like portion corrsponding to the secretory part. By electron microscopy we observed that the basal part of the epithelium has many interdigitations associated with mitochondria. On the apical surface where epicuticular foldings are located an electonlucent space is often seen. The glands are composed of the following elements: 1) superficial epithelial cells, located just below the apical surface foldings; 2) secretory cells; which are long and have an intracellular canalicule which changes according to the functional state of the cell; 3) a collecting duct to the secretory cells and covered with an epicuticle, reaching up to the gland's lumen; and 4) cells around the duct

Ultrastructural studies of the hemocytes of Panstrongylus megistus (Hemiptera: Reduvidae)

Estudos ao microscópio eletrônico de transmissäo revelaram a presença de seis tipos de hemócitos na hemolinfa de Panstrongylus megistus. Estes resultados confirmam parcialmente os obtidos anteriormente através da microscopia de luz. Pró-hemócitos: células pequenas e arredondadas, cuja delgada faixa citoplasmática é especialmente rica em ribossomos livres e pobre em sistemas membranosos. Plasmatócitos: células polimórficas, cujo citoplasma caracteriza-se por um retículo endoplasmático rugoso (RER) bem desenvolvido e principalmente pela sua abundância em lisossomos. Säo células tipicamente fagocitárias. Algumas vezes, seu citoplasma mostra-se extremamente vacuolizado. Granulócitos: hemócitos granulares, cujos grânulos mostram diferentes graus de eletrondensidade e podem ou näo apresentar estruturaçäo interna. Coagulócitos: hemócitos ovalados ou fusiformes que se caracterizam pela presença de acentuadas cisternas perinucleares. O citoplasma é geralmente eletrondenso, pobre em organelas membranosas e contêm grânulos frágeis. Enocitóides: hemócitos grandes e muito estáveis em sua morfologia. Seu citoplasma é homogêneo, rico em ribossomos livres e pobre em sistemas membranosos. Adipo-hemócitos: células grandes que apresentam inclusöes lipídicas características. Seu citoplasma é também rico em glicogênio RER e mitocôndrias grandes. As contagens totais (THC) e diferenciais (DHC) de hemócitos foram também calculadas. A THC cresce de 2.900 hemócitos/mm3 de hemolinfa em ninfas de 4§ estágio para 4.350 em ninfas de 5§ estágio. Há, no entanto, um decréscimo significativo nos adultos, onde a THC passa para 1.950 hemócitos/mm3 de hemolinfa. Plasmatócitos e coagulócitos säo os hemócitos hemolinfa. Plasmatócitos e coagulócitos säo os hemócitos predominantes em P. megistus

Ultrastructural studies of the hemocytes of Panstrongylus megistus (Hemiptera: Reduviidae).

Ultrastructural analyses revealed the presence of six hemocyte types in the hemolymph of Panstrongylus megistus, partially confirming our previous results obtained through light microscopy. Prohemocytes: small, round hemocytes with a thin cytoplasm layer, especially rich in free ribosomes and poor in membranous systems. Plasmatocytes: polymorphic cells, whose cytoplasm contains many lysosomes and a well developed rough endoplasmic reticulum (RER). They are extremely phagocytic. Sometimes, they show a large vacuolation. Granulocytes: granular hemocytes whose granules show different degrees of electrodensity. Most of them, have an internal structuration. Coagulocytes: oval or elongated hemocytes, which show pronounced perinuclear cisternae as normally observed in coagulocytes. The cytoplasm is usually electrodense, poor in membranous systems and contains many labile granules. Oenocytoids: large and very stable hemocytes, whose homogeneous cytoplasm is rich in loose ribosomes and poor in membranous systems. Adipohemocytes: large cells, containing several characteristic lipid droplets. The cytoplasm is also rich in glycogen, RER and large mitochondria. The total and differential hemocyte count (THC and DHC) were also calculated for this reduviid. THC increases from 2,900 hemocytes/mm3 of hemolymph in the 4th instar to 4,350 in the 5th and then, decreases to 1,950 in the adults. Plasmatocytes and coagulocytes are the predominant hemocyte types.

Aspectos ultra-estruturais do corpus cardiacum, corpus allatum e aorta de Panstronggylus megistus (Hemiptera: reduviidae) / Ultrastructural aspects of corpus cardiacum, corpus allatum and aorta of Panstrongylus megistus (Hemiptera: Reduviidae)

Em P. megistus o corpus cardiacum e a aorta têm uma estrutura semelhante. Ambos apresentam axônios de neurônios secretores cerebrais. A presença de grânulos de neurossecreçäo e o revestimento por uma bainha conjuntiva reforçam a idéia da funçäo neurohemal da aorta. O corpus allatum mostra células de formas diferentes. Os núcleos säo volumosos e muitos deles têm nucléolos desenvolvidos. Numerosas mitocôndrias granulares e filamentosas säo vistas concentradas em determinadas regiöes das células. Os contornos das células e dos núcleos säo regulares, características de células do corpus allatum ativo

Electron microscope observations of Trypanosoma cruzi during development inside the haemocytes of Triatominae.

The haemolymph of Panstrongylus megistus, infected by Trypanosoma cruzi, was examined by light and electron microscopy. Numerous parasites lie inside the haemocytes, each one in a vacuole. Their well-preserved morphological features support the concept of parasite multiplication in cells of the insect haemolymph.