RESUMO
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.
Assuntos
Phlebotomus/ultraestrutura , Sensilas/ultraestrutura , Animais , Feminino , Phlebotomus/fisiologia , Sensilas/fisiologiaRESUMO
BACKGROUND: Sand flies are vectors of Leishmania spp., the causative agents of leishmaniasis in vertebrates, including man. The sand fly saliva contains powerful pharmacologically active substances that prevent hemostasis and enhance Leishmania spp. infections. On the other hand, salivary proteins can protect vaccinated mice challenged with parasites. Therefore, sand fly salivary proteins are relevant for the epidemiology of leishmaniasis and can be a potential target for a vaccine against leishmaniasis. Despite this, studies on sand fly salivary glands (SGs) are limited. METHODS: The present study analyzes, in detail, the morphology, anatomy and ultrastructure of the SGs of sand fly vectors of the genera Lutzomyia and Phlebotomus. We used histology, transmission and scanning electron microscopy and lectin labeling associated with confocal laser microscopy. RESULTS: The SGs have conserved and distinct morphological aspects according to the distinct sand fly species. Each SG has a single rounded lobe constituting of c.100-120 secretory cells. The SG secretory cells, according to their ultrastructure and lectin binding, were classified into five different subpopulations, which may differ in secretory pathways. CONCLUSIONS: To the best of our knowledge, these morphological details of sand fly salivary glands are described for the first time. Further studies are necessary to better understand the role of these different cell types and better relate them with the production and secretion of the saliva substances, which has a fundamental role in the interaction of the sand fly vectors with Leishmania.
Assuntos
Psychodidae/ultraestrutura , Glândulas Salivares/ultraestrutura , Animais , Vetores de Doenças , Leishmaniose/transmissão , Microscopia Eletrônica , Mosquitos Vetores/anatomia & histologia , Mosquitos Vetores/parasitologia , Mosquitos Vetores/ultraestrutura , Phlebotomus/anatomia & histologia , Phlebotomus/parasitologia , Phlebotomus/ultraestrutura , Psychodidae/anatomia & histologia , Psychodidae/parasitologia , Glândulas Salivares/parasitologiaRESUMO
In the present study, some morphological structures of antennae, maxillary palps and caudal setae of fourth instar larvae of laboratory-reared phlebotomine sand flies (Lutzomyia longipalpis, L. migonei, L. evandroi, L. lenti, L. sericea, L. whitmani and L. intermedia) of the State of Ceará, Brazil, were examined under scanning electron microscopy. The antennal structures exhibited considerable variation in the morphology and position. A prominent digitiform distal segment has been observed only on the antenna of species of the subgenus Nyssomyia. The taxonomic relevance of this and other antennal structure is discussed. The papiliform structures found in the maxillae and the porous structures of the caudal setae of all species examined may have chemosensory function. Further studies with transmission electron microscopy are needed to better understand the physiological function of these external structures.
Assuntos
Phlebotomus/ultraestrutura , Órgãos dos Sentidos/ultraestrutura , Animais , Larva/ultraestrutura , Microscopia Eletrônica de VarreduraRESUMO
A morphological study of the midgut of Lutzomyia intermedia, the primary vector of cutaneous leishmaniasis, in southeast Brazil, was conducted by light, scanning and transmission electron microscopy. The midgut is formed by a layer of epithelium of columnar cells on a non-cellular basal lamina, under which there is a musculature, which consists of circular and longitudinal muscular fibers. A tracheolar network is observed surrounding and penetrating in the musculature. Females were examined 12, 24, 48, 72 h and 5 days following a blood meal and were analyzed comparatively by transmission electron microscopy with starved females. In starved females, the epithelium of both the anterior and posterior sections of the midgut present whorl shaped rough endoplasmic reticulum. The posterior section does not present well-developed cellular structures such as mitochondria. Observations performed at 12, 24, 48 and 72 h after the blood meal showed morphological changes in the cellular structures in this section, and the presence of the peritrophic matrix up to 48 h after the blood meal. Digestion is almost complete and a few residues are detected in the lumen 72 h after blood feeding. Finally, on the 5th day after the blood meal all cellular structures present the original feature resembling that seen in starved sand flies. Morphometric data confirmed the morphological observations. Mitochondria, nuclei and microvilli of midgut epithelial cells are different in starved and blood fed females. The mitochondria present a similar profile in the epithelium of both the anterior and posterior section of the midgut, with higher dimension in starved females. The cell microvilli in the posterior section of the midgut of starved females are twice the size of those that had taken a blood meal. We concluded that there are changes in the midgut cellular structures of L. intermedia during the digestion of blood, which are in agreement with those described for other hematophagous diptera.
Assuntos
Mucosa Intestinal/ultraestrutura , Phlebotomus/ultraestrutura , Animais , Feminino , Microscopia Eletrônica de VarreduraRESUMO
The life cycle of Leishmania panamensis in Phlebotomus papatasi was studied to characterize barriers limiting parasite colonization, differentiation, migration, and attachment in an unnatural sand fly host. The insects were fed a suspension of L. panamensis-infected macrophages and human erythrocytes, and were examined up to 16 days post-infection by light and electron microscopy. Histologic examination of 401 flies showed the peritrophic membrane to be the first important barrier to parasite establishment in the gut lumen. In most flies, parasites were unable to escape from the closed peritrophic sac, which was either excreted or retained intact in the midgut. After five days, only 31% of the flies were infected; attached parasites colonized the pylorus-ileum and/or colon regions of the hindgut. Anterior migration into the cardia region of the midgut occurred in less than 1% of infected flies; no parasites colonized the foregut. In the bloodmeal and residual bloodmeal, five morphologic forms developed from ingested amastigotes: stumpy, spatulate, elongate, short nectomonad promastigotes, and paramastigotes. Abnormal retention of amastigotes in macrophages and delayed development of promastigote stages was observed. The primary form attached in the hindgut was a pear-shaped haptomonad promastigote. Differentiation of L. panamensis in Ph. papatasi appeared to be similar to that described in natural hosts, except that metacyclic infective forms were not observed, and some forms developed in unusual locations. Phlebotomus papatasi was a partly refractory biological host for L. panamensis. The peritrophic membrane adversely affected the infection rate; rare anterior migration and a lack of metacyclic promastigotes may preclude transmission by bite.