Aleksandra Oliveira-Menezes

Morphological aspects of Angiostrongylus costaricensis by light and scanning electron microscopy.

Angiostrongylus costaricensis is a parasitic nematode that can cause severe gastrointestinal disease, known as abdominal angiostrongiliasis, in humans. This paper presents the characterization of first- and third-stage larvae and male and female adult worms of A. costaricensis by scanning electron and light microscopy. Several novel anatomical structures were identified by scanning electron microscopy, including details of the cuticular striations of the spicules in male worms and a protective flap of the cuticle covering the vulvar aperture in female worms. Other taxonomic features revealed by light microscopy include the gubernaculum and the esophageal-intestinal valve. The use of two microscopy techniques allowed a detailed characterization of the morphology of this nematode. A number of previously identified taxonomic features, such as the striated nature of the spicules and the lateral alae were confirmed; however, the use of scanning electron microscopy resulted in a reassessment of the correct number of papillae distributed around the oral opening and behind the cloacal opening. These observations, in combination with light microscopy-based characterization of the gubernaculum and esophageal valves, have allowed a more detailed description of this nematode taxonomy.

New insight into the morphology of Eurytrema coelomaticum (Trematoda, Dicrocoeliidae) cercariae by light, scanning, and transmission electron microscopies

Eurytrema coelomaticum is a digenetic trematode that parasitizes the pancreatic ducts of ruminants. In the present study, the morphology of the cercariae was analyzed using light, scanning, and transmission electron microscopies. The size of the larvae was larger than that reported in the literature. An oral sucker with many papillae and an oral aperture in its center and a ventral sucker with few discrete papillae on the edge were observed. No stylet at the anterior end of the larval body and spines on the tegument of the end of the tail were observed. The cercariae had lateral penetration glands and (central) pre-acetabular glands, from which ducts lead to the anterior region and open into a small anterior pocket. The flame cells were located laterally and communicated with fine branches, converging to two lateral excretory collecting ducts that opened into an excretory bladder, centrally located at the posterior end of the body. The tegument presented an external layer loosely attached to the larval body, below which an amorphous syncytial outer layer with many mitochondrial profiles was observed. This region exhibited many secretions and released secretory granules, indicating intense secretory activity. The circular and longitudinal muscle layers were arranged in sequence below the outer layer. The outer layer was connected by cytoplasmic bridges crossing the muscular layers to the internal region of the tegument, where the cell body with nucleus was located. In the cercarial body, it was possible to observe a typical flame cell with the barrel region, where cilia and the internal and external ribbed regions were found. The somatic cells seem to have an active metabolism, with a well-developed endoplasmic reticulum, secretory granules, and evident nuclei. The results are discussed in the light of the biology and taxonomy of this species.

Light and scanning electron microscopy of sporocysts of Eurytrema coelomaticum (Giard et Billet, 1892) Looss, 1907

Eurytrema coelomaticum is a fluke that infects ruminants in South America, Europe and Asia. The morphology of the mother and daughter sporocysts of E. coelomaticum obtained from Bradybaena similaris, the first intermediate host, is described for the first time by light and scanning electron microscopy. The intermediate host was exposed to E. coelomaticum eggs and after 30 days the mother sporocyst was found in the coelom adhered to the intestine wall. This sporocyst was a rounded or elongated mass (0.1078 mm), with numerous germinal balls in it, and a folded tegument with no specializations. The daughter sporocysts obtained following dissection of infected snails have varied shape, one hollow tapered region with many transversal and longitudinal striations, named anterior end. The expelled daughter sporocyst presented an oval sac-like central region with a small anterior and a posterior longer filament-like prolongation. The measures of the expelled sporocysts are presented and compared to previous descriptions.

Further description of Aspidodera raillieti (Nematoda: Aspidoderidae) from Didelphis marsupialis (Mammalia: Didelphidae) by light and scanning electron microscopy

Nematodes of the family Aspidoderidae (Nematoda: Heterakoidea) Freitas 1956 are widely distributed from Americas. The species of the genus Aspidodera Railliet and Henry 1912 are parasites of mammals of the orders Edentata, Marsupialia, and Rodentia. In the present work, Aspidodera raillieti (L. Travassos, Mem Inst Oswaldo Cruz 5(3):271–318, 1913), collected from the large intestine of Didelphis marsupialis (Mammalia: Didelphidae) from Valle del Cauca, Colombia, is redescribed. The association of light and scanning electron microscopy (SEM) allowed a detailed analysis of the morphology and ultrastructure of this nematode. Some taxonomic features, such as cephalic region, topography of the cuticle, sucker, spicules, posterior end of males, localization of vulva, the anus, and posterior end of females were observed. Important structures such as amphid, details of cephalic region, phasmid, and number and localization of caudal papillae are documented by SEM, for the first time adding characters to identify this species. Colombia is a new geographical record for A. raillieti.

Ultrastructure of the sporocysts of Eurytrema coelomaticum (Giard Et Billet, 1892) Looss, 1907

The digenetic trematode Eurytrema coelomaticum is a parasite of pancreatic ducts of ruminants. The ultrastructure of the mother and daughter sporocysts of E. coelomaticum was analyzed. The mother sporocyst was attached to the coelome of the intestine wall of intermediate snail host Bradybaena similaris, intimately adhered in some regions. It presents a highly folded tegument with granules and the body wall was composed by an outer syncitial layer, basal lamina, and circular and longitudinal muscle layer. Below was the cell body (cyton) with the nucleus. The daughter sporocysts obtained by dissection exhibited many granules and secretory vesicle in the outer layer indicating an intense secretory activity. The body wall presented the same layers of the mother sporocysts, but the outer syncitial layer invaginated and an amorphous layer was present between the syncitial and circular muscle layers. The protonephridial excretory system was viewed. The anterior and posterior end of the expelled sporocyst exhibit a degenerated structure, but biological activity still occurred in these regions. The swollen middle of the body was filled by a lamellar structure formed by degenerating membranes, but the excretory system was preserved. The endocyst wall was fibrilar and filled by cercariae and amorphous, membranous and secretory material inside it. These results were discussed.

Cuticular architecture of Hassalstrongylus epsilon (Nematoda: Trichostrongyloidea)

Abstract Hassalstrongylus epsilon is a small nematode, whose adult forms are found among the intestinal microvilli of the water rat Nectomys squamipes, Brants 1827 (Rodentia: Muridae). The external appearance of the cuticle, which presents transversal striations and longitudinal ridges, is described using scanning electron microscopy. Transmission electron microscopy of thin sections and replicas of quick-frozen, freeze-fractured, deep-etched and rotatory shadowed samples showed the presence in the cuticle of struts that arise from the fluid median layer, extending outward to the epicuticle. The cuticle showed the presence of five layers: epicuticle, cortical, fibril-rich, fluid median and fibrous. The cuticle layers were made of an assemblage of fibers that create compartments, which were larger in the fluid region than in the fibril-rich median layer.

Histopathological changes in the kidneys of vertebrate hosts infected naturally and experimentally with Paratanaisia bragai (Trematoda, Digenea).

Paratanaisia bragai is a trematode parasite that reaches sexual maturity in the kidney collecting ducts of domesticated and wild fowl and whose intermediate hosts are the snails Subulina octona and Leptinaria unilamellata. There are some discrepancies in descriptions of the pathology of this parasite in bird kidneys. Therefore, the purpose of this study was to analyze the kidneys of rock pigeons (Columba livia) naturally infected and of chickens (Gallus gallus) experimentally infected with Paratanaisia bragai, by means of macroscopic observation and by light and scanning electron microscopy. Both bird species showed significantly dilated collecting ducts. In addition, lymphocyte infiltration was observed in the kidneys of C. livia and metaplasia in the epithelial lining of the kidney collecting ducts of G. gallus.

New Aspidoderidae species parasite of Didelphis aurita (Mammalia: Didelphidae): a light and scanning electron microscopy approach.

Nematodes of the family Aspidoderidae (Nematoda: Heterakoidea) Skrjabin and Schikobalova, 1947, are widely distributed in the Americas. The family Aspidoderidae includes the subfamilies Aspidoderinae Skrjabin and Schikobalova, 1947, and Lauroiinae Skrjabin and Schikobalova, 1951. These two subfamilies are delineated by the presence or absence of cephalic cordons at the anterior region. The nematodes in the subfamily Aspidoderinae, which includes the genus AspidoderaRailliet and Henry, 1912, are represented by nematodes with anterior cephalic cordons at the anterior end. The nematodes of the genus AspidoderaRailliet and Henry, 1912, are found in the cecum and large intestine of mammals of the orders Edentata, Marsupialia and Rodentia. Species within this genus have many morphological similarities. The use of scanning electron microscopy allows the specific characterization of the species within this genus. In the present work, we describe a new species of Aspidodera parasite of the large intestine of Didelphis aurita (Mammalia: Didelphidae) Wied-Neuwied, 1826, collected from Cachoeiras de Macacu, Rio de Janeiro. The combination of light and scanning electron microscopy allowed us a detailed analysis of this nematode.

Ultrastructural analysis of Wuchereria bancrofti (Nematoda: Filarioidea) body wall.

Bancroftian filariasis constitutes the principal mosquito-borne nematode infection of humans and the surface of adult of Wuchereria bancrofti seems to be especially important in the intricate interplay between host and parasite. The study of the parasites surface structure might help to understand the localization and function of various organelles. W. bancrofti adult worms were recovered from untreated patients during hydrocele repair surgery and studied by transmission electron microscopy. The body wall of adult parasite is composed of cuticle, hypodermis and muscular layer. Cuticle is the external layer and shows transverse cuticular striation. It is composed by an epicuticle, cortical layers, median layer, fibrous layers and basal layer. The epicuticle is the most external cuticular layer and appears as a single laminar electron-dense layer. The cortical external region is more electron-dense and granular in appearance than the inner cortical layer. Electron-dense structures, called bosses are randomly distributed filling the cuticular striation. The median layer is formed by an electron-dense and continuous thick line. The fibrous layer is subdivided in inner and external layers connected by projections. The basal layer includes a large quantity of membranous projections directed toward the hypodermis. The hypodermis is a syncytium where some cellular organelles are observed. The somatic musculature is meromyarian. The muscle fibers consist of contractile and non-contractile regions and the contractile region is composed of myofilaments separated by dense body. This is the first study of W. bancrofti adult worms obtained from untreated patients and studied by transmission electron microscopy.

Additional study of the morphology of eggs and miracidia of Eurytrema coelomaticum (Trematoda)

Abstract The morphology of the eggs and miracidia of Eurytrema coelomaticum was analyzed. The eggshell presented different composition according to the maturation stage of the egg, as seen by distinct birefringence after polarized light microscopic analysis. Detailed morphology of the brownish eggs, measuring 44.97±3.83 (38.67 - 51.40) μm in length and 30.71±2.54 (25.79 -34.47) μm in width, and the different electrondensities of the inner, middle and outer layers of the eggs were determined using light (bright field and DIC) and electronic microscopy (scanning and transmission). The morphometry of the eggs is in accordance to those measures presented in previous studies. The miracidia were observed using light microscopy, inside and outside the egg. It was possible to observe the terebratorium at the anterior end of the body, the ciliated epidermal plates, placed according the formula E=2E1 + 2E2, and the interepidermal ridge, but eyespots were not observed. The excretory vesicle was laterally placed in the posterior middle of the body and the germ balls were observed. The miracidium inside the egg was observed by routine techniques, but the miracidium was not well preserved. Thus, the eggs were processed using high pressure-freeze substitution technique and reasonable preservation was achieved. The cilia covering the larval body, with a typical ciliary organization, the terebratorium with folds and the junction of the epidermal ciliated cell with the larval body were seen. For the first time detailed information on the eggs and miracidia of E. coelomaticum is given, which can be the basis for new studies.