Morphological Characterization of the Antennal Sensilla of the Afrotropical Sand Fly, Phlebotomus duboscqi (Diptera: Psychodidae)

We investigated by scanning electron microscopy the morphology, distribution, and abundance of antennal sensilla of females Phlebotomus duboscqi sand fly, an important vector of zoonotic cutaneous leishmaniasis at Afrotropical region. Thirteen well-differentiated sensilla were identified, among six types of cuticular sensilla. The probable function of these sensillary types is discussed in relation to their external structure and distribution. Five sensillary types were classified as olfactory sensilla, as they have specific morphological characters of sensilla with this function. Number and distribution of sensilla significantly differed between antennal segments. The results of the present work, besides corroborating in the expansion of the morphological and ultrastructural knowledge of P. duboscqi, can foment future electrophysiological studies for the development of volatile semiochemicals, to be used as attractants in traps for monitoring and selective vector control of this sand fly.

Ultrastructure of the Antennae and Sensilla of Nyssomyia intermedia (Diptera: Psychodidae), Vector of American Cutaneous Leishmaniasis

The antennal sensilla and the antenna of females Nyssomyia intermedia, one of the main vectors of American cutaneous leishmaniasis, were studied by scanning electron microscopy. The main goal was to characterize the quantity, typology, and topography of the sensilla with particular attention to the olfactory types. The insects were captured in the city of Corte de Pedra, State of Bahia, Brazil, by CDC-type light traps and raised in a laboratory as a new colony. Fourteen well-differentiated sensilla were identified, among six cuticular types: trichoidea, campaniformia, squamiformia, basiconica, chaetica, and coeloconica. Of these, six sensilla were classified as olfactory sensilla due to their specific morphological features. Smaller noninnervated pilosities of microtrichiae type were also evidenced by covering all antennal segments. The antennal segments differ in shapes and sizes, and the amount and distribution of types and subtypes of sensilla. This study may foment future taxonomic and phylogenetic analysis for a better evolutionary understanding of the sand flies. Besides, it may assist the targeting of future electrophysiological studies by Single Sensillum Recording, and aim to develop alternative measures of monitoring and control of this vector.

Microanatomy of the American Malaria Vector Anopheles aquasalis (Diptera: Culicidae: Anophelinae) Midgut: Ultrastructural and Histochemical Observations

The mosquito gut is divided into foregut, midgut, and hindgut. The midgut functions in storage and digestion of the bloodmeal. This study used light, scanning (SEM), and transmission (TEM) electron microscopy to analyze in detail the microanatomy and morphology of the midgut of nonblood-fed Anopheles aquasalis females. The midgut epithelium is a monolayer of columnar epithelial cells that is composed of two populations: microvillar epithelial cells and basal cells. The microvillar epithelial cells can be further subdivided into light and dark cells, based on their affinities to toluidine blue and their electron density. FITC-labeling of the anterior midgut and posterior midgut with lectins resulted in different fluorescence intensities, indicating differences in carbohydrate residues. SEM revealed a complex muscle network composed of circular and longitudinal fibers that surround the entire midgut. In summary, the use of a diverse set of morphological methods revealed the general microanatomy of the midgut and associated tissues of An. aquasalis, which is a major vector of Plasmodium spp. (Haemosporida: Plasmodiidae) in America.

The Midgut Muscle Network of Anopheles aquasalis (Culicidae, Anophelinae): Microanatomy and Structural Modification After Blood Meal and Plasmodium vivax (Haemosporida, Plasmodiidae) Infection

The mosquito midgut is divided into two regions named anterior midgut (AMG) and posterior midgut (PMG). The midgut expands intensely after the blood ingestion to accommodate a large amount of ingested food. To efficiently support the bloodmeal-induced changes, the organization of the visceral muscle fibers has significant adjustments. This study describes the spatial organization of the Anopheles aquasalis (Culicidae, Anophelinae) midgut muscle network and morphological changes after bloodmeal ingestion and infection with Plasmodium vivax (Haemosporida, Plasmodiidae). The midgut muscle network is composed of two types of fibers: longitudinal and circular. The two types of muscle fibers are composed of thick and thin filaments, similar to myosin and actin, respectively. Invagination of sarcoplasm membrane forms the T-system tubules. Sarcoplasmic reticulum cisternae have been observed in association with these invaginations. At different times after the bloodmeal, the fibers in the AMG are not modified. A remarkable dilation characterizes the transitional area between the AMG and the PMG. In the PMG surface, after the completion of bloodmeal ingestion, the stretched muscle fibers became discontinued. At 72 h after bloodmeal digestion, it is possible to observe the presence of disorganized muscle fibers in the midgut regions. The Plasmodium oocyst development along the basal layer of the midgut does not have a significant role in the visceral musculature distribution. This study provides features of the visceral musculature at different blood feeding times of An. aquasalis and shows important changes in midgut topography including when the mosquitoes are infected with P. vivax.