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.

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.

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.

Morphology and morphometry of the scutellum of six species in the genus Meccus (Hemiptera: Triatominae).

We studied the morphology and morphometry of scutella from six species of the hemipteran genus Meccus to identify new tools to help solve taxonomic problems in closely related insect species of epidemiological relevance. Scutellum samples were observed by scanning electron microscopy and were subjected to morphometric analysis. The results mainly show differences in central depression shape, posterior process, and vestiture. We found significant dimensional differences in scutellum morphometry and a clear sexual dimorphism among species. A combination of morphology and morphometry can be used to differentiate among species of the genus Meccus.

Anatomy of the spermatophore in triatomines (Hemiptera, Reduviidae, Triatominae) and its applications to the study of Chagas disease vector biology.

The present study focused on spermatophore structure, transfer, and subsequent destination inside bloodfeeding females of the species Triatoma infestans and Rhodnius neglectus. The morphology of the spermatophore differed between the species studied, such that in T. infestans, the shape was ovaloid, whereas in R. neglectus, the shape resembled a rod. Structures' spine-like cuticulars distributed across the inner surface of the vagina of both species were observed; however, the role of these cuticulars is unknown in Triatominae. In both species, there was an opening in the spermatophore exactly where the common oviduct is connected, thereby making it possible to confirm that the process of spermatozoid migration takes place through this opening. The results obtained show that the spermatophores of T. infestans and R. neglectus differ in size, shape, and structure. Therefore, they can be used as taxonomic markers and may provide information regarding physiology and evolution.

Description of the cave organ in three species of the genus Belminus (Hemiptera: Reduviidae: Triatominae) by optical and scanning electron microscopy.

The cave organ is a sensory receptor in the antenna pedicel of some Reduviidae. This paper describes this organ for the first time in three species of the genus Belminus, Belminus corredori, Belminus ferroae and Belminus herreri, by optical and scanning electron microscopy. The structures presented a general pattern similar to one reported for other species of Triatominae.

Description of the cave organ in three species of the genus Belminus (Hemiptera: Reduviidae: Triatominae) by optical and scanning electron microscopy

The cave organ is a sensory receptor in the antenna pedicel of some Reduviidae. This paper describes this organ for the first time in three species of the genus Belminus, Belminus corredori, Belminus ferroae and Belminus herreri, by optical and scanning electron microscopy. The structures presented a general pattern similar to one reported for other species of Triatominae.

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.

[Morphologic, morphometrical, and histological aspects of the eggs of four species of the genera Meccus (Hemiptera, Reduviidae, Triatominae)]. / Estudo de ovos de quatro espécies do gênero Meccus (Hemiptera, Reduviidae, Triatominae), vetores da doença de Chagas.

The objective of this work was to analyze the morphological, morphometrical, and histological characteristics of eggs of four triatomine bugs species still not studied, in order to understand phylogenetic aspects and to facilitate parameters used in taxonomy, with the purpose of a specific and generic characterization of these vectors in public health. The eggs of each species had come from the collections of the Laboratory of Triatomine bugs and Culicid mosquitoes of the Faculdade de Saúde Pública - USP (Faculty of Public Health/USP). The morphologic studies were carried out through optic microscopy (OM) and scanning electronic microscopy (SEM). The eggs were measured with the help of the digital paquimeter Starrett 727. In relation to histological measures, Microtome Leica RM 2145 was used. Similarities were evidenced in the exocorial architecture of the eggs when they were studied by OM and SEM. This similarity among the eggs suggests a recent speciation, probably derived from common ancestry, representing a monophyletic group. Some structures were also detected by the histological cuts. The study has contributed to the magnification and recognition in generic and specific terms of the Triatominae subfamily. These new data will be able to subsidize a better understanding to determine roles for each vector species and to facilitate parameters to be used in taxonomy.

Estudo de ovos de quatro espécies do gênero Meccus (Hemiptera, Reduviidae, Triatominae), vetores da doença de Chagas / Morphologic, morphometrical, and histological aspects of the eggs of four species of the genera Meccus (Hemiptera, Reduviidae, Triatominae)

The objective of this work was to analyze the morphological, morphometrical, and histological characteristics of eggs of four triatomine bugs species still not studied, in order to understand phylogenetic aspects and to facilitate parameters used in taxonomy, with the purpose of a specific and generic characterization of these vectors in public health. The eggs of each species had come from the collections of the Laboratory of Triatomine bugs and Culicid mosquitoes of the Faculdade de Saúde Pública - USP (Faculty of Public Health/USP). The morphologic studies were carried out through optic microscopy (OM) and scanning electronic microscopy (SEM). The eggs were measured with the help of the digital paquimeter Starrett® 727. In relation to histological measures, Microtome Leica RM 2145® was used. Similarities were evidenced in the exocorial architecture of the eggs when they were studied by OM and SEM. This similarity among the eggs suggests a recent speciation, probably derived from common ancestry, representing a monophyletic group. Some structures were also detected by the histological cuts. The study has contributed to the magnification and recognition in generic and specific terms of the Triatominae subfamily. These new data will be able to subsidize a better understanding to determine roles for each vector species and to facilitate parameters to be used in taxonomy.

Estudo de ovos de dez espécies da subfamília Triatominae (Hemiptera, Reduviidae) / Study of eggs of ten species of the subfamily Triatominae (Hemiptera, Reduviidae)

Objetivo. Analisar as características morfológicas, morfométricas e histológicas de ovos de dez espécies de triatomíneos ainda näo estudadas, visando melhor compreender aspectos filogenéticos e facilitar parâmetros usados em taxonomia, com a finalidade de uma caracterizaçäo específica e genérica desses vetores de Trypanosoma cruzi. Métodos. A investigaçäo constou de pesquisa bibliográfica, seguida de pesquisa morfológica, morfométrica e histológica de ovos de espécies provenientes do acervo do Laboratório de Triatomíneos e Culicídeos da Faculdade de Saúde Pública - USP, do Insetário do Serviço Especial de Saúde de Araraquara / SESA e do insetário de triatomíneos do Laboratório Nacional e Internacional de Referência em taxonomia de triatomíneos da FIOCRUZ/RJ. Os estudos morfológicos foram realizados por meio de Microscopia Optica e Microscopia Eletrônica de Varredura; as análises estatísticas foram estabelecidas por Análise de Variância e teste de Tukey. Na histologia utilizou-se micrótomo Leica RM 2145®. Resultados. Das dez espécies estudadas, foi possível visualizar diferenças morfológicas significantes em seis delas. No entanto, em quatro espécies houve grandes semelhanças que näo oferecem condiçöes para distinçäo das mesmas. A análise estatística revelou diferenças significantes (p<0,001, pelo teste F) entre as médias de comprimento e largura. Algumas estruturas também foram detectadas pelos cortes histológicos. Conclusöes. O estudo contribuiu para a ampliaçäo do reconhecimento genérico e específico da subfamília Triatominae. As características identificadas no exocório das cascas dos ovos podem auxiliar na separaçäo de espécies próximas. Esses novos parâmetros poderäo subsidiar a elaboraçäo de futuras chaves dicotômicas, auxiliando na determinaçäo de cada espécie vetora, e ampliando o conceito específico.

Comparative study of enzymes in testes and ovaries from adult Dipetalogaster maximus (Uhler) and triatoma infestans (Klug) (Hemiptera: Reduviidae). correlation with fine structural organization.

Activities of hexokinase (HK), glucose-6-phosphate dehydrogenase (G6PDH), fructose-6-phosphate kinase (F6PK), glutamate dehydrogenase (GlutDH), aspartate aminotransferase (AAT), malate dehydrogenase (MDH) and glycerol-3-phosphate dehydrogenase (GPDH) were determined in tissue extracts of testes and ovaries of adult Dipetalogaster maximus (Uhler) and Triatoma infestans (Klug) (Hemiptera: Reduviidae), insect vectors of Chagas disease. The fine structure organization of the same organs were studied by electron microscopy. Results allow the following inferences: in testes from both species, most of the glucose would be utilized through the glycolytic pathway. Amino acid catabolism for energy purposes appears to be unimportant. The number of mitochondria and the development of the rough endoplasmic reticulum in cells of the spermatogenic line indicate the occurrence of active oxidative metabolism and protein synthesis; in ovaries, levels of G6PDH indicate the existence of an active pentose pathway which would supply the NADPH required for fat and ecdysteroid synthesis. Amino acid catabolism appears to be relatively more important in ovary than in testis. Fat and glycogen are stored in follicular cells of D. maximus; oocytes of both species contain numerous fat droplets. Abundant mitocondria are present in follicular cells and oocytes. A well developed rough endoplasmic reticulum and free ribosomes are also conspicuous in these cells. The malate/aspartate H-transfer system seemed to be relatively more important than the glycerophosphate shuttle in ovaries as well in testes.

Aspectos morfológicos de abdômen de ninfas de 5§ estádio de seis espécies de triatominae (Hemiptera, Reduviidae) por microscopia óptica / Morphological studies of abdomen of fifth instar nymphs of six species of Triatominae (Hemiptera, Reduviidae), through optical microscopy

Descreveu-se, com o auxílio da microscopia óptica, os segmentos abdominais dorsais e ventrais de ninfas de 5§ estádio de Panstrongylus megistus, Rhodnius neglectus, Triatoma brasiliensis, T. infestans, T. matogrossensis e T. tibiamaculata. As estruturas estudadas foram: conexivo, áreas glabras, áreas brilhantes, placa quitinosa, estigmas, respiratórios e tubérculos dorsais.

[Morphological study of ovum and nymphs of Dipetalogaster maximus (Uhler, 1894) (Hemiptera, Reduviidae, Triatominae)]. / Estudo morfológico de ovos e ninfas de Dipetalogaster maximus (Uhler, 1894) (Hemiptera, Reduviidae, Triatominae).

Intending to provide new parameters to be used in Triatomines' Taxonomy, vectors of Chaga's Disease and to amplify a large range of knowledge about this species, a study of the structure of the egg and external morphology of the five nymphal instars was done. The eggs show under optical microscope (M.O.), the chorium's surface of the body and the operculum formed by poligonal areas, clearer under scanning electronic microscope (MEV). The apex of the third rostrum segment in all 5 instars nymphs, show 1 + 1 invaginated and elongated structures and the apical portion of the second tarsal segment presents a group of more or less numerous, very long, delicated and golden hairs.

Estudo morfológico de ovos e ninfas de Dipetalogaster maximus (Uhler, 1894) (Hemiptera, Reduviidae, Triatominae) / Morphological study of ovum and nymphs of Dipetalogaster maximus (Uhler, 1894) (Hemiptera, Reduviidae, Triatominae)

A fim de proporcionar novos parâmetros a serem usados na Taxonomia dos Triatomíneos, vetores da Doença de Chagas e ampliar os conhecimentos a respeito desta espécie, realizou-se um estudo da estrutura de ovos e da morfologia externa dos cinco estádios ninfais, através de microscopia óptica e eletrônica de varredura. Os ovos mostram em microscopia óptica (M.O.), a superfície do exocório do corpo e opérculo formada por áreas poligonais, mais nítidas quando observadas em microscopia eletrônica de varredura (MEV). Os 5 estádios ninfais apresentam no ápice do 3§ segmento do rostro 1+1 estruturas alongadas, que se exteriorizam; anida no 2§ segmento tarsal, um adensado apical de cerdas longas e delicadas, de coloraçäo dourada (Lent and Wygodzinsky, 1979)

Aspects of classification of Hemiptera hemocytes from six triatomine species

The objective of this work was to characterize, and compare different morphological types of hemocytes of Rhodnius prolixus, Rhodnius, Rhodnius neglectus, Triatoma infestans, Panstrongylus megistus, and Dipetalogaster maximus. This information provides the basis for studying the cellular immune systems of these insects. Seven morphological hemocyte types wereidentified by phase-contrast microscopy: prohemocytes, plasmatocytes, granular cells, cytocytes, oenocytoids, adipohemocytes and giant cells. All seven types of hemocytes are not present in every species. For example, adipohemocytes and oenocytoids were not observed in P. megistus and P. infestans, and giant cells were rarely found in any of the species studied. The hemocytes of rhodnius and Dipetalogaster are more similar to each other than those from Triatoma and Panstrongylus which in turn closely resemble each other. Emphasis is placed on methodological problems arising in this work wicah are discussed in detail

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.