The External Morphology of the Eggs of Culex (Culex) saltanensis (Diptera: Culicidae) Under Scanning Electron Microscopy.

The aim of the present study was to describe the morphology of the eggs of Culex (Culex) saltanensis Dyar that occurs in the Neotropical region. Eggs of the Cx. (Cux.) saltanensis were collected at the Mata Atlântica FIOCRUZ campus, fixed in 1% osmium tetroxide, prepared for mounting on metal supports, observed under a scanning electron microscope, and described morphologically. The eggs had a coniform shape with a length of approximately 0.5 mm (505-510 µm) and a width in the median portion of 117 µm (113-123 µm). Upper portion is lined with tubers of irregular shape and varying sizes (0.64-1.31 µm), located on a cross-linked matrix forming bands observed under optical microscopy. The micropyle is encased in a necklace of approximately 6.6-µm plates arranged in a flower-like shape. Comparing Cx. (Cux.) saltanensis eggs with several species of different genera, important divergent characteristics can be observed. However, this study points to the need for new descriptions of eggs of species belonging to the same subgenus in order to analyze if there will be differences between them. Culex (Cux.) saltanensis eggs have particular characteristics not observed in eggs of other Culicidae genera.

Auditory Efferent System Modulates Mosquito Hearing.

The performance of vertebrate ears is controlled by auditory efferents that originate in the brain and innervate the ear, synapsing onto hair cell somata and auditory afferent fibers [1-3]. Efferent activity can provide protection from noise and facilitate the detection and discrimination of sound by modulating mechanical amplification by hair cells and transmitter release as well as auditory afferent action potential firing [1-3]. Insect auditory organs are thought to lack efferent control [4-7], but when we inspected mosquito ears, we obtained evidence for its existence. Antibodies against synaptic proteins recognized rows of bouton-like puncta running along the dendrites and axons of mosquito auditory sensory neurons. Electron microscopy identified synaptic and non-synaptic sites of vesicle release, and some of the innervating fibers co-labeled with somata in the CNS. Octopamine, GABA, and serotonin were identified as efferent neurotransmitters or neuromodulators that affect auditory frequency tuning, mechanical amplification, and sound-evoked potentials. Mosquito brains thus modulate mosquito ears, extending the use of auditory efferent systems from vertebrates to invertebrates and adding new levels of complexity to mosquito sound detection and communication.

A 'NanoSuit' surface shield successfully protects organisms in high vacuum: observations on living organisms in an FE-SEM.

Although extremely useful for a wide range of investigations, the field emission scanning electron microscope (FE-SEM) has not allowed researchers to observe living organisms. However, we have recently reported that a simple surface modification consisting of a thin extra layer, termed 'NanoSuit', can keep organisms alive in the high vacuum (10(-5) to 10(-7) Pa) of the SEM. This paper further explores the protective properties of the NanoSuit surface-shield. We found that a NanoSuit formed with the optimum concentration of Tween 20 faithfully preserves the integrity of an organism's surface without interfering with SEM imaging. We also found that electrostatic charging was absent as long as the organisms were alive, even if they had not been coated with electrically conducting materials. This result suggests that living organisms possess their own electrical conductors and/or rely on certain properties of the surface to inhibit charging. The NanoSuit seems to prolong the charge-free condition and increase survival time under vacuum. These findings should encourage the development of more sophisticated observation methods for studying living organisms in an FE-SEM.

[Updated inventory of mosquitoes (Diptera: Culicidae) of the island of La Réunion, Indian Ocean]. / Inventaire actualisé des moustiques (Diptera : Culicidae) de l'île de La Réunion, océan Indien.

A literature analysis coupled with new entomological surveys conducted between 2009 and 2012 led to changes in the list of mosquito species present on the island of La Réunion. Using morphological criteria, Orthopodomyia arboricollis is replaced by Or. reunionensis. On the basis of morphometrical and genetic criteria, Culex univittatus is replaced by Cx. neavei. Cx. poicilipes, which was already reported missing 40 years ago, has not been found again. Anopheles arabiensis is confirmed as the only species of the Gambiae complex present on the island. Thus, twelve species are currently known. For each of them, elements of taxonomic, biological and medical interest are listed. An. arabiensis is a major vector of human Plasmodium (last case of indigenous malaria in 1967). In the Indian Ocean, Aedes albopictus and Ae. aegypti both are competent for transmitting dengue and chikungunya viruses. In Africa, Cx. quinquefasciatus transmits Wuchereria bancrofti and Cx. neavei transmits the Sindbis virus; both species also transmit the West Nile virus. Cx. tritaeniorhynchus is the major vector of Japanese Encephalitis virus in Asia. Two species are endemic (Ae. dufouri and Or. reunionensis), the ten other ones are also found in Madagascar and on the African continent (An. coustani, An. arabiensis, Ae. fowleri, Cx. tritaeniorhynchus, Cx. neavei, Cx. insignis, Lutzia tigripes), with three of them having also a cosmopolitan distribution (Ae. aegypti, Ae. albopictus and Cx. quinquefasciatus). Among the twelve recorded taxa, eight species are anthropophilic, three are supposedly zoophilic and one is a predatory species. No new invasive anthropophilic species did settle on the island. Updated identification keys of larval and adult stages are proposed.

Scanning electron microscopy of the four larval instars of the lymphatic filariasis vector Culex quinquefasciatus (Say) (Diptera: Culicidae).

Since Culex pipiens quinquefasciatus is the main vector of lymphatic filariasis in tropics and subtropics, the identification and quantification of this mosquito is an important task. Scanning electron microscopy reveals that morphological changes during larval development as the number of comb scale varies greatly and their complexity increases from first to the fourth instar. Also, their structures are more complex with a varying number of subapical denticles. The amount of pecten shows modifications at different larval instars with regard to the number and complexity of their spines. The pecten teeth increase in their number and complexity during development. The number of lateral palatal brush filaments increases during larval development from the first to the fourth instar. The ventral brush of the abdominal segment X in the first and second instars is composed of two respectively three pairs of setae while the third and fourth instars have four pairs of sturdy setae.

Caracterização e detecção molecular de alelos de resistência ao biolarvicida Bacillus sphaericus em culex quinquefasciatus / Characterization and molecular detection of resistance alleles to the Bacillus sphaericus biolarvicide in Culex quinquefasciatus

A resistência de Culex quinquefasciatus à toxina inseticida (Bin) de Bacillus sphaericus (Bsp) pode estar associada a uma falha da ligação da toxina com os receptores Cqm1, localizados no microvilli intestinal das larvas através de uma âncora GPI. Mutações no gene cqm1 podem impedir a expressão de proteínas Cqm1 funcionais e gerar um alto nível de resistência. O objetivo deste trabalho foi caracterizar e avaliar a frequência de alelos de resistência (r) em populações e colônias de C. quinquefasciatus. Neste estudo, o alelo r cqm1REC, selecionado e identificado anteriormente na colônia R2362, foi detectado por PCR alelo-específica em quatro populações de Recife com frequências entre 0,001 e 0,017. Em duas populações foram identificados novos alelos r, o cqm1REC-D16 e o cqm1REC- D25, com frequência entre 0,002-0,006. Estes alelos são caracterizados por deleções de 16 e 25-nt, respectivamente, as quais geram códon de terminação da tradução prematuro (CTTP) e não codificam proteínas com âncora GPI. Um segundo alelo r (cqm1REC- 2) foi identificado na colônia R2362 e possui uma mutação nonsense (G1292A) que também gera um CTTP, impedindo a localização de receptores Cqm1 no epitélio. O alelo cqm1REC-2 foi co-selecionado com o cqm1REC na colônia R2362 e uma análise da competição entre eles mostrou que o cqm1REC-2 predomina sob pressão de seleção com Bsp, enquanto que o cqm1REC é majoritário na ausência de Bsp. A expressão relativa dos alelos cqm1REC e cqm1REC-2, avaliada por PCR em tempo real, mostrou que ambos possuem uma expressão significativamente menor em relação ao cqm1. Amostras de microvilli intestinal de larvas homozigotas para cada alelo apresentaram uma baixa capacidade de interação com a toxina Bin, corroborando os dados de expressão gênica e o fenótipo de resistência. Este estudo mostrou a detecção e caracterização de novos alelos de C. quinquefasciatus que conferem resistência a Bsp e estes dados são fundamentais para o diagnóstico e manejo da resistência em programas de controle.

Scanning electron microscopic studies on egg surface morphology and morphometrics of Culex pipiens pipiens (Lin.) (northern house mosquito) and Culex quinquefasciatus (Say) (southern house mosquito) (Diptera: Culicidae).

During this study the surface morphology and morphometric of Culex pipiens pipiens (Lin.) and Culex quinquefasciatus (Say) eggs were described and compared using scanning electron microscopy for the first time. The results indicate that eggs of both species appear to be similar to great extent in surface morphology. However, morphometric provide 71.621% demarking attributes out of 44 attributes at various significant levels (P < 0.05-0.001), i.e., egg length, width and ratio of length/width, attributes of micropylar apparatus including corolla, disc, mound, tubercles size, and length of tubercular rows in micropylar region, size and density of tubercles, exochorionic pore in conical-shaped regions of eggs, and size of tubercular wheel units. Structurally, the additional presence of large tubercles strengthens the micropylar region to bear various collapsing forces in these species.

Cytopathological effects of Bacillus sphaericus Cry48Aa/Cry49Aa toxin on binary toxin-susceptible and -resistant Culex quinquefasciatus larvae.

The Cry48Aa/Cry49Aa mosquitocidal two-component toxin was recently characterized from Bacillus sphaericus strain IAB59 and is uniquely composed of a three-domain Cry protein toxin (Cry48Aa) and a binary (Bin) toxin-like protein (Cry49Aa). Its mode of action has not been elucidated, but a remarkable feature of this protein is the high toxicity against species from the Culex complex, besides its capacity to overcome Culex resistance to the Bin toxin, the major insecticidal factor in B. sphaericus-based larvicides. The goal of this work was to investigate the ultrastructural effects of Cry48Aa/Cry49Aa on midgut cells of Bin-toxin-susceptible and -resistant Culex quinquefasciatus larvae. The major cytopathological effects observed after Cry48Aa/Cry49Aa treatment were intense mitochondrial vacuolation, breakdown of endoplasmic reticulum, production of cytoplasmic vacuoles, and microvillus disruption. These effects were similar in Bin-toxin-susceptible and -resistant larvae and demonstrated that Cry48Aa/Cry49Aa toxin interacts with and displays toxic effects on cells lacking receptors for the Bin toxin, while B. sphaericus IAB59-resistant larvae did not show mortality after treatment with Cry48Aa/Cry49Aa toxin. The cytopathological alterations in Bin-toxin-resistant larvae provoked by Cry48Aa/Cry49Aa treatment were similar to those observed when larvae were exposed to a synergistic mixture of Bin/Cry11Aa toxins. Such effects seemed to result from a combined action of Cry-like and Bin-like toxins. The complex effects caused by Cry48Aa/Cry49Aa provide evidence for the potential of these toxins as active ingredients of a new generation of biolarvicides that conjugate insecticidal factors with distinct sites of action, in order to manage mosquito resistance.

Light and electron microscopic studies on the development of the ovaries of Culex pipiens quinquefasciatus (Say) (Diptera: Culicidae).

Christopher's stages of ovarian development are redefined in Culex pipiens quinquefasciatus to provide a more useful description of mosquito physiology. During this ovarian development, seven growing stages of the oocyte are observed in the adult stage. Two distinct periods of egg follicle growth, the previtellogenesis and vitellogenesis, are seen first. The gradual increase in the oocyte size during these phases is attributed to yolk deposition. During vitellogenesis, the oocyte and nurse cell nucleus are similar in size (stage I). Then, the oocyte enlarges and occupies one third of the egg follicle, while the nurse cell (NC) occupies the remaining two thirds. At this phase, the yolk granules (stage III) enlarge, occupying about half of the egg follicle, while the NC contain the other half (stage IV). An increase and accumulation of yolk granules leads to the filling of about three fourths of the egg bulk and makes the oocyte nucleus hardly visible during stage V. The oocyte undergoes a remarkable growth, occupying nine tenth of the length of the follicle in stage VI. Stage VII corresponds to a mature cigar-shaped egg and contains two kinds of yolk globules: a large one and a small one. The oocyte and the NC at all stages are surrounded by a single layer of epithelial cells which increase in number and form the vitelline membrane and the chorion. The mitochondria in the NC, oocyte, and follicular epithelium appear in light microscopy as granules of different sizes. The Golgi apparatus appears in different sizes and shapes, since in the early stages of development, it is restricted to the perinuclear zone. When the development proceeds, it enlarges in size, spreads over the whole cytoplasm, and participates in the formation of the yolk.

Characterization of antennal trichoid sensilla from female southern house mosquito, Culex quinquefasciatus Say.

Culex quinquefasciatus, the southern house mosquito, is highly dependent on its olfactory system for vector-related activities such as host seeking and oviposition. The antennae are the primary olfactory organs in mosquitoes. We describe 5 morphological types of sensilla on the antenna of C. quinquefasciatus: 1) a pair of sensilla coeloconica located at the distal tip, 2) long and short sensilla chaetica present on all 13 antennal flagella, 3) sensilla ampullacea found on the 2 proximal-most flagella, 4) 2 morphological types of grooved pegs dispersed throughout the flagella, and 5) 5 morphological subtypes of sensilla trichodea distributed among all flagella. Antennal trichoid and grooved peg sensilla of mosquitoes have been demonstrated to house the olfactory receptor neurons (ORNs) that detect many of the odors involved in eliciting vector-related behaviors. In order to initiate the functional characterization of the peripheral olfactory system in female C. quinquefasciatus, we mapped the physiological responses of all 5 morphological subtypes of sensilla trichodea to an odor panel of 44 behaviorally relevant odor compounds. We identified 17 functional classes of sensilla trichodea: 3 short sharp-tipped, 9 short blunt-tipped type I, and 5 short blunt-tipped type II sensilla. One morphological subtype remains unclassified as the long sharp-tipped sensilla did not respond to any of the volatiles tested. The functional classes of the ORNs were analyzed with respect to stimulus response profiles, stimuli sensitivity, and temporal coding patterns. Comparisons with other functionally classified mosquito antennal sensilla trichodea are discussed.

Ultrastructural analysis of midgut cells from Culex quinquefasciatus (Diptera: Culicidae) larvae resistant to Bacillus sphaericus.

The larvicidal action of the entomopathogen Bacillus sphaericus towards Culex quinquefasciatus is due to the binary (Bin) toxin present in crystals, which are produced during bacterial sporulation. The Bin toxin needs to recognize and bind specifically to a single class of receptors, named Cqm1, which are 60-kDa alpha-glucosidases attached to the apical membrane of midgut cells by a glycosylphosphatidylinositol anchor. C. quinquefasciatus resistance to B. sphaericus has been often associated with the absence of the alpha-glucosidase Cqm1 in larvae midgut microvilli. In this work, we aimed to investigate, at the ultrastructural level, the midgut cells from C. quinquefasciatus larvae whose resistance relies on the lack of the Cqm1 receptor. The morphological analysis showed that midgut columnar cells from the resistant larvae are characterized by a pronounced production of lipid inclusions, throughout the 4th instar. At the end of this stage, resistant larvae had an increased size and number of these inclusions in the midgut cells, while only a small number were observed in the cells from susceptible larvae. The morphological differences in the midgut cells of resistant larvae found in this work suggested that the lack of the Cqm1 receptor, which also has a physiological role as being an alpha-glucosidase, can be related to changes in the cell metabolism. The ultrastructural effects of Bin toxin on midgut epithelial cells from susceptible and resistant larvae were also investigated. The cytopathological alterations observed in susceptible larvae treated with a lethal concentration of toxin included breakdown of the endoplasmic reticulum, mitochondrial swelling, microvillar disruption and vacuolization. Some effects were observed in cells from resistant larvae, although those alterations did not lead to larval death, indicating that the receptor Cqm1 is essential to mediate the larvicidal action of the toxin. This is the first ultrastructural study to show differences in the cell morphology of resistant larvae and further investigation is needed to understand the impact of the lack of expression of midgut enzymes on the physiology of resistant insects.

The invasion of the midgut of the mosquito Culex (Culex) quinquefasciatus Say, 1823 by the helminth Litomosoides chagasfilhoi Moraes Neto, Lanfredi and De Souza, 1997.

The Litomosoides chagasfilhoi helminth was studied as a model for microfilaria invasion of the midgut of Culex quinquefasciatus mosquito, vector of Wuchereria bancrofti helminth, causative agent of the human filariasis. Histology and transmission and scanning electron microscopy were utilized to show the topography of mosquito midgut invasion by the helminth. An analysis of midguts dissected at different time points after a blood meal demonstrated that the microfilariae interacted and crossed the peritrophic matrix and the midgut epithelium of C. quinquefasciatus. The microfilariae invaded preferentially the mosquito abdominal midgut and the invasion process occurred between 2 and 3h after the blood feeding. In some cases, microfilariae caused an opening in the midgut that separated the epithelial cells, while in others cases, the worms caused the detachment of cells from the epithelium. Ultimately, L. chagasfilhoi crossing activity appeared to damage the midgut. It was also observed that the microfilariae lost their sheaths during their passage through the fibrous material of the peritrophic matrix, before they reached the midgut epithelium. Since the exsheathment process is necessary for the continuity of larvae development, it seems that the passage through the peritrophic matrix is an important step for the parasite's life cycle. This experimental model revealed details of the interaction process of helminthes within the vector midgut, contributing to the knowledge of factors involved in the vector competence of C. quinquefasciatus as a vector of filariasis.

Ultrastructural study of West Nile virus pathogenesis in Culex pipiens quinquefasciatus (Diptera: Culicidae).

The ultrastructural features of West Nile virus (WNV) replication and dissemination in orally infected Culex pipiens quinquefasciatus Say were analyzed over a 25-d infection period. To investigate the effects of virus replication on membrane induction, cellular organization, and cell viability in midgut and salivary gland tissues, midguts were dissected on days 3, 7, 14, and 21, and salivary glands were collected on days 7, 14, 21, and 25 postinfection (d.p.i.) for examination by transmission electron microscopy (TEM). Whole mosquito heads were embedded for TEM analysis 14 d.p.i. to localize WNV particles and to investigate the effects of replication on nervous tissues of the brain. Membrane proliferation was induced by WNV in the midgut epithelium, midgut muscles, and salivary glands, although extensive endoplasmic reticulum swelling was a unique feature of salivary gland infection. TEM revealed WNV-induced pathology in salivary glands at 14, 21, and 25 d.p.i., and we hypothesize that long-term virus infection of this tissue results in severe cellular degeneration and apoptotic-like cell death. This finding indicates that the efficiency of WNV transmission may decrease with mosquito age postinfection.

Ultrastructural characterization of the hemocytes of Culex quinquefasciatus (DIPTERA: Culicidae).

Six hemocytes cell types from Culex quinquefasciatus were identified by light and transmission electron microscopy: They are prohemocytes (9.3%), spherulocytes (1.6%), adipohemocytes (0.8%), oenocytoids (4.6%), plasmatocytes (43.4%) and granulocytes (40.3%). The prohemocytes were the smallest hemocytes encountered in the hemolymph, displaying a large and centrally located nucleus, almost filling the whole cell. The spherulocytes, which were small hemocytes, presented small and numerous spherules with a lamellar pattern and an electron-dense core. Rare adipohemocytes were observed in the C. quinquefasciatus hemolymph, presenting large nucleus with an evident nucleolus, cytoplasm containing rough endoplasmic reticulum (RER), mitochondriae and lipid inclusions. C. quinquefasciatus oenocytoids showed homogeneous cytoplasm with several granules, completely or partially filled with amorphous material. These cells showed abundant smooth endoplasmic reticulum (SER) and dense mitochondriae. By light microscopy analysis we identified two morphological types of plasmatocytes, granular and agranular. However, ultrastructural investigation revealed that the granular cells contained lipid inclusion between RER membranes, instead of membrane-bounded granules. The granulocytes presented a fusiform or circular profile and displayed a unique and very complex process of granules formation, including organization of polysomes inside vesicles that protrude from the Golgi system, synthesis of a proteinaceous material, condensation of the granule matrix and recycling of endoplasmic membranes. Intense endocytic pathways were also observed in the granulocytes.

Blocked stomodeal valve of the insect vector: similar mechanism of transmission in two trypanosomatid models.

The regurgitation of metacyclic stages from the sand fly cardia is thought to be the prevailing mechanism of Leishmania transmission. This regurgitation may result through damage of the stomodeal valve and its mechanical block by the parasites. We found this phenomenon in three sand fly-Leishmania models and also in avian trypanosomes transmitted by Culex mosquitoes. Phlebotomus duboscqi, Phlebotomus papatasi, Lutzomyia longipalpis, and Culex pipiens were membrane-fed on blood containing Leishmania major, Leishmania chagasi (syn. infantum) and an unidentified avian Trypanosoma from Trypanosoma corvi clade, respectively. Females with the late-stage infections were processed for the optical and transmission electron microscopy. Localization of the parasites and changes to the stomodeal valve were in some aspects similar in all vector-parasite pairs studied: (i) a large plug of flagellates was observed in cardia region, (ii) parasites were attached to the chitin lining of the stomodeal valve by the formation of zonal hemidesmosome-like plaques. Leishmania promastigotes were found both attached to the valve as well as unattached in the lumen of midgut. The stomodeal valve of infected sand flies was opened, its chitin lining was destroyed and the unique filamentous structures on the apical end of cylindrical cells were degraded. In the Culex-Trypanosoma model, the whole population of epimastigotes was found in close contact with the chitin lining, and degenerative changes of the valve were less pronounced. We suggest that the phenomenon involving a blocked valve facilitating the regurgitation of parasites into the vertebrate host may occur generally in heteroxenous trypanosomatids transmitted by the bite of nematoceran Diptera.

Three-dimensional visualization of insect morphology using confocal laser scanning microscopy.

Cuticular structures of insects are often microscopic and intricately complex; among the most complex structures are male genitalia. Genitalic structures are essential in taxonomic and phylogenetic studies of insects. Using well-described species from two disparate dipteran genera, we demonstrate the utility of confocal laser scanning microscopy for studying the morphological characters of fly genitalia by taking advantage of the autofluorescent properties of cuticle material. Reconstructions of confocal data sets obtained from genitalic structures embedded in two commonly used entomological mounting media (euparal and glycerin jelly) are presented. Aberration artefacts often observed in confocal data obtained from thick specimens were analysed and strategies for their minimization are discussed. Our results indicate that confocal laser scanning microscopy and 3D reconstruction are excellent techniques for visualizing small, complex, autofluorescent structures in flies. These techniques could have a profound impact on the quality of information provided by 3D representations of insect structures over more traditional methods of visualization.

Ultrastructural studies on the sporogony of Hepatozoon spp. in Culex quinquefasciatus say, 1823 fed on infected Caiman crocodilus and Boa constrictor from northern Brazil.

Laboratory reared Culex quinquefasciatus Say, 1823 originating from the vicinity of Belem, in northern Brazil, were allowed to engorge on caimans (Caiman c. crocodilus) infected with Hepatozoon caimani (Carini, 1909) and boas (Boa constrictor) infected with H. cf. terzii (Sambon and Seligmann, 1907) both from Para State. Engorged mosquitoes killed on successive days post-feeding (p.f.) were studied by transmission electron microscopy. Images of oocysts from 13 days p.f., caiman-fed mosquitoes were also examined by scanning electron microscopy. The Hepatozoon spp. from the respective hosts differed in their ability to develop in C. quinquefasciatus. Most female mosquitoes fed on caimans, became fully engorged, and survived beyond 22 days p.f., whereas those engorged on boa became debilitated and did not survive beyond 9 days p.f. In boa-fed mosquitoes oocysts were found on the 6th day p.f. The few mosquitoes surviving to the 9th day p.f. contained either undivided oocysts or those that had already commenced sporogenic division. By 8-10 days p.f. caiman-fed mosquitoes contained uninucleate oocysts. Sporogonic divisions were observed from day 12 p.f. onwards. Although sporogenic development conformed in general with the previously reported accounts, the study allowed a more detailed examination of the plasmalemmal endocytotic system, and the consolidation of the crystalline body in specialized 'factories' of cystalline material. Sporozoite differentiation occasionally started on the 18th day p.f., but otherwise was observed only on day 22 p.f.

Laboratory evaluation of Bacillus sphaericus recycling in mosquito larvae.

After ingestion by Culex pipiens and Anopheles pharoensis 4th instar larvae, spores of Bacillus sphaericus strain faiyoum rapidly germinated inside live mosquito midgut. Bacterial counts and electron microscopic observations on intoxicated larvae revealed that the number of viable spores rapidly decreased during the first 12 h, with a maximum between 12 and 24 h. In cadavers, the number of heat-resistant spores quickly increased between the first and second day post-feeding. After one week, the number of spores inside dead larvae reached approximately 20 times the number of ingested spores for both mosquito species (4 x 16(5) spores/larva). Ultrathin sections of recycled spores showed the presence of a crystalline inclusion identical to that initially present in spores before ingestion. Bioassay on Cx pipiens 4th instar larvae showed a similar toxicity between in vivo recycled spores (LC50 = 1.1 +/- 0.3 x 10(5) spores/ml after 24h exposure) and culture-medium-grown spores of B. sphaericus strain faiyoum (LC50 = 1.7 +/- 10(5) spores/ml).

A morfologia do intestino médio de Culex quinquefasciatus Say, 1823 e sua interação experimental com microfilárias de Litomosoides chagasfilhoi Moraes Neto, Lanfredi e De Souza, 1997 e Wuchereria bancrofti (Cobbold, 1877) Seurat, 1921 / The morphology of the midgut of Culex quinquefasciatus Say, 1823 and its interaction with experimental microfilariae of Litomosoides chagasfilhoi Moraes Neto, Lanfredi and De Souza, 1997 and Wuchereria bancrofti (Cobbold, 1877) Seurat, 1921

Analisamos a morfologia do intestino médio do mosquito Culex quiquefasciatus de região endêmica e a sua interação com as microfilárias de Wuchereria bancrofti (agente da filariose humana) e de Litomosoides chagasfilhoi (agente de filariose de roedores). O intestino médio está dividido em regiões torácica e abdominal como visto em outras espécies de mosquitos. Porém, o intestino médio torácico é formado por dois tipos celulares: células principais e basais; e o intestino médio abdominal por três tipos: células principais clara e basais. Existe uma rede muscular organizada revestindo externamente o órgão, a qual sofre mudanças irreversíveis no intestino médio abdominal após o repasto sangüíneo. A estrutura da matriz peritrófica e a sua formação induzida pela alimentação sangüínea são distintas das demais espécies de mosquitos. O L. chagasfilhoi invade o intestino médio entre 1h e 3h após o repasto infectivo, enquanto que a W. bancrofti entre 30 minutos e 5 horas com o maior número de invasão nas primeiras 2 horas. O L. chagasfilhoi preferencialmente invade o intestino médio abdominal enquanto que a W. bancrofti invade o intestino médio torácico, principalmente perto da região abdominal. Ambas espécies de microfilárias cruzam o intestino médio através do espaço intercelular, causando hipertrofia e extrusão de uma a duas células epiteliais. A perda da bainha pelas microfilárias de ambas espécies não é um pré-requisito para a evasão do intestino. Etapas subseqüentes do ciclo da W. bancrofti, tais como, a melanização na hemocele e a invasão precoce da musculatura de vôo foram também observadas. Não foi possível observar tais etapas nos mosquitos infectados com L. chagasfilhoi porque eles morreram poucas horas após a invasão do intestino médio. Estas diferenças no processo de interação das espécies de microfilárias provavelmente estão relacionados com a capacidade vetorial do mosquito.

A morfologia do intestino médio de Culex quinquefasciatus Say, 1823 e sua interação experimental com microfilárias de Litomosoides chagasfilhoi Moraes Neto, Lanfredi e De Souza, 1997 e Wuchereria bancrofti (Cobbold, 1877) Seurat, 1921

Analisamos a morfologia do intestino médio do mosquito Culex quiquefasciatus de região endêmica e a sua interação com as microfilárias de Wuchereria bancrofti (agente da filariose humana) e de Litomosoides chagasfilhoi (agente de filariose de roedores). O intestino médio está dividido em regiões torácica e abdominal como visto em outras espécies de mosquitos. Porém, o intestino médio torácico é formado por dois tipos celulares: células principais e basais; e o intestino médio abdominal por três tipos: células principais clara e basais. Existe uma rede muscular organizar revestindo externamente o órgão, a qual sofre mudanças irreversíveis no intestino médio abdominal após o repasto sangüíneo. A estrutura da matriz peritrófica e a sua formação induzida pela alimentação sangüínea são distintas das demais espécies de mosquitos. O L. chagasfilhoi invade o intestino médio entre 1h e 3h após o repasto infectivo, enquanto que a W. bancrofti entre 30 minutos e 5 horas com o maior número de invasão nas primeiras 2 horas. O L. chagasfilhoi preferencialmente invade o intestino médio abdominal enquanto que a W. bancrofti invade o intestino médio torácico, principalmente perto da região abdominal. Ambas espécies de microfilárias cruzam o intestino médio através do espaço intercelular, causando hipertrofia e extrusão de uma a duas células epiteliais. A perda da bainha pelas microfilárias de ambas espécies não é um pré-requisito para a evasão do intestino. Etapas subseqüentes do ciclo da W. bancrofti, tais como, a melanização na hemocele e a invasão precoce da musculatura de vôo foram também observadas. Não foi possível observar tais etapas nos mosquitos infectados com L. chagasfilhoi porque eles morreram poucas horas após a invasão do intestino médio. Estas diferenças no processo de interação das espécies de microfilárias provavelmente estão relacionados com a capacidade vetorial do mosquito