Scanning and transmission electron microscopy of the tegument of Paranaella luquei Kohn, Baptista-Farias & Cohen, 2000 (Microcotylidae, Monogenea), parasite of a Brazilian catfish, Hypostomus regani

The surface topography and ultrastructure of the tegument of Paranaella luquei Kohn, Baptista-Farias & Cohen, 2000, a microcotylid monogenean parasite from the gills of Hypostomus regani (Ihering, 1905) (Loricariidae) was studied by scanning (SEM) and transmission electron microscopy (TEM). By SEM, it was observed that the tegument presents transversal ridges, forming folds in the ventral and dorsal surfaces and microvillous-like tegumental projections in the anterior and median regions of body. These projections were also observed by TEM. The tegument is made up of a syncytium delimited by apical and basal plasma membranes, containing inclusion bodies and mitochondria, connected to the nucleated region by means of cytoplasmatic processes. The tegumental cells present a well developed nucleus and cytoplasm containing inclusion bodies, similar to those found on the external layer, mitochondria, rough endoplasmatic reticulum and free ribossomes.     

Ultrastructure and cytochemistry of the tegument of Orthocoelium scoliocoelium and Paramphistomum cervi (Trematoda: Digenea)

The tegument of Orthocoelium scoliocoelium and Paramphistomum cervi was examined using histochemical techniques and electron microscopy. On the basis of the distribution of acid and alkaline phosphatase (E.C. 3.1.3.2, E.C. 3.1.3.1), non-specific esterase (E.C. 3.1.1.1), cholinesterase (E.C. 3.1.1.7) and succinate dehydrogenase (E.C. 1.3.99.1) at light microscope level two distinct regions were recognized, an outer and an inner zone. Electron microscopy revealed that the tegument comprises an outer surface syncytium underlain by a thick subsyncytial zone and musculature. Deeper still occur the nucleated "tegumental cells". The latter are in cytoplasmic continuity with the surface syncytium via vacuolated cytoplasmic trabeculae which traverse the muscle layers and the subsyncytial zone. Three types of tegumental cells each lacking mitochondria were observed. The T1 cells synthesize discoid and electron dense T1 bodies while T2 cells produce oval and electron lucent T2 bodies. The third type of tegumental cells apparently produce no secretory bodies and may represent an embryonic cell type. The surface syncytium contains T1 and T2 secretory bodies and is bounded apically by a plasma membrane invested externally by a fuzzy and filamentous glycocalyx. The surface syncytium lacks mitochondria and is traversed by infoldings of the basal plasma membrane. Beneath the surface syncytium the subsyncytial zone is largely comprised of fibrous interstitial material. This zone, which is particularly thick in the amphistomes, is traversed by trabeculae and extensions of underlying parenchymal cells which usually contain mitochondria and lysosomes. The subsyncytial zone overlies numerous circular and longitudinal muscle fibres. The absence of mitochondria and enzymes associated with active transport suggests that the amphistome tegument may be mainly specialized for protection of the worm against mechanical and chemical conditions prevailing in the rumen. Active uptake of nutrients is probably not a primary function.     

Actin cytoskeleton in adults and metacercariae of Brachylaima sp

Experimental adults and natural metacercariae of Brachylaima sp. (Digenea: Brachylaimidae) were processed for transmission and scanning electron microscopy, for tetramethyl rhodamine isothiocyanate phalloidin fluorescence, conventional and confocal microscopy and for monoclonal anti-actin antibody immunoelectron microscopy, to describe the ultrastructural features of the tegument and to localize actin in several regions of the body. The general body tegument is spinous and contains membrane-bound disc-shaped biconcave vesicles in adults and metacercariae. Spines are flat and apically indented in the adult. A thick glycocalyx covers the body of the metacercaria. Direct fluorescence revealed filamentous actin in the spines and the subtegumental musculature of the adult. The subtegumental musculature comprises two systems consisting of an outer circular layer and an inner layer composed of cross-linked longitudinal and diagonal fibres. Immunoreactivity in adults and metacercariae revealed the presence of actin in the spines and subtegumental musculature but not in the tegumental matrix, interstitial fibrous material nor the parenchyma. Actin was detected in the dense collar and bulb matrix of the tegumental ciliated sensilla and, for the first time, in the apical cytoplasmatic projections of the digestive cell of the adult.     

The action of fenasal on the ultrastructure of the tegument in Caryophyllaeus laticeps cestodes

The effect of the anthelmintic preparation fenasal on the fine structure of tegument of the cestode Caryophyllaeus laticeps, a parasite of Cyprinidae, was studied in vitro. 10 mcg/ml concentration of fenasal causes numerous evaginations of the external cytoplasmic layer in the scolex of helminth. Inside these formations there are granules of secretion, mitochondria, vacuoles. At the same time microtrichia disappear from the surface, cytoplasmic layer gets thinner and its mitochondria degenerate. In the middle part of the body the number of microtrichia decreases, the layer of tegumental cells swells and conformational condition of its mitochondria changes. The degree of injury depends on the exposition time which was from 0 to 4 hours.     

An ultrastructural study of the early cercarial development in Prosorhynchoides borealis (Digenea: Bucephalidae) with special reference to formation of the primitive epithelium

Primitive epithelium and outer tegumental layer formation during early cercarial development was studied in Prosorhynchoides borealis using electron microscopy. It demonstrated that germinal cells freely floating in the sporocyst body cavity divide to give rise to naked cell aggregates. These early embryos are highly irregular in outline and are composed of blastomeres differing in size and structure. In embryos consisting of about 12-14 cells a few (possibly only two) superficial macromeres become concave and produce thin extensions which envelop the embryonic mass before fusing to form a syncytial primitive epithelium. This primitive epithelium forms syncytial connections with underlying embryonic cells. Primordial tegumental cells become apparent in late germinal balls below the primitive epithelium. These cells expand and fuse to give rise to an embryonic nucleated tegument. The embryonic tegument is connected to peripheral embryonic cells by thin cytoplasmic bridges until the basement lamina is formed. Subsequently, the primitive epithelium is shed by the embryos and the nuclei in the embryonic tegument undergo pyknotic degeneration. These results are analysed and compared with data from studies on other trematode species and it is concluded that the primitive epithelium is derived from the embryo in at least the majority of digeneans.     

Ultrastructure of the tail appendage in microphallid cercariae (Trematoda, Microphallidae)

The tail structure of larvae of Maritrema subdolum and Microphallus claviformes is similar in essence. Its wall is made by the tegument and underlying layers of muscles. The syncytial anucleated tegumental lamina with the only type of secretory inclusions forms regular circular folds along the tail. The outer muscle layer is formed by the smooth muscular cells. It is underlaid by the longitudinal cross-striated muscles with the strongly pronounced sarcomere organization. The nucleus-containing bodies of the muscle cells occupy the axial part of the tail excepting the central cavity. The functional joining of tail and body musculatures is provided by thick muscle bundles in the caudal department of the larval body.     

东方杯叶吸虫体被的超微结构

扫描电镜显示东方杯叶吸虫体被有许多族生棘,具纤毛乳突和无纤毛窝状乳突,附着器皮层特化为微毛。透射电镜观察表明,皮层是由合胞体、基膜和肌肉层组成,合胞体通过细胞通道与皮层细胞相连。文中详细描述了这些结构,揭示无纤毛窝状乳突为腺乳突,皮层细胞间存在线粒体细胞和附着器皮层形成微毛,探讨了这些结构的生理功能。体外培养成虫皮层结构的某些不正常变化,如皮层细胞的空虚松散,可作为评价吸虫体外培养的一种指标。     

Ultrastructural and histochemical observations on the tegument of Gastrodiscoides hominis (Paramphistoma: Digenea).

The tegument of the paramphistome, Gastrodiscoides hominis, is basically similar to that of other digeneans. It is folded into concentrically arranged furrows and ridges bearing numerous tightly packed tubercules, and extends into the oral cavity. An area of specialized tegument is present on the ventral surface, anterior to the disc region. Mitochondria are absent from the tegumental syncytium and underlying tegumental cells, suggesting that the tegument may serve principally as a protective layer rather than in active uptake phenomena. However, extensions of the lymph and parenchyma systems are closely associated with the base of the tegumental syncytium and may provide ATP for active processes. Ciliated and non-ciliated sensory papillae are present, particularly around the oral opening. Numerous lymph channels are present in the sub-tegument and may be involved in osmoregulation.     

Ultrastructural and histochemical observations on the tegument of Gastrodiscoides hominis (Paramphistoma: Digenea)

The tegument of the paramphistome, Gastrodiscoides hominis, is basically similar to that of other digeneans. It is folded into concentrically arranged furrows and ridges bearing numerous tightly packed tubercules, and extends into the oral cavity. An area of specialized tegument is present on the ventral surface, anterior to the disc region. Mitochondria are absent from the tegumental syncytium and underlying tegumental cells, suggesting that the tegument may serve principally as a protective layer rather than in active uptake phenomena. However, extensions of the lymph and parenchyma systems are closely associated with the base of the tegumental syncytium and may provide ATP for active processes. Ciliated and non-ciliated sensory papillae are present, particularly around the oral opening. Numerous lymph channels are present in the sub-tegument and may be involved in osmoregulation.     

Ultrastructure of the tegument of the metacercaria of Timoniella imbutiforme

The spinous body tegument of the metacercaria of Timoniella imbutiforme (Molin, 1859) is described in detail and found to comprise an outer tegumental syncytium connected to subjacently situated subtegumentary 'cells'. There are four types of secretory bodies in the outer syncytial layer as well as serrated overlapping spines and mitochondria. The subtegumentary 'cells' are characterized by the presence of four secretory body types as well as giant bodies which may be involved in the elaboration of the secretory bodies or spine material. The normal configuration of the somatic muscles of T. imbutiforme show that the muscular machinery necessary for activity once the larval stage becomes excysted is already in place. The sensory endings are found to be of the uniciliate type occurring in groups of up to eight in raised domes distributed over the body. Secretory gland cells are numerous and possess long ducts connected to the basal lamina of the outer syncytial layer via septate desmosomes.     

Ultrastructural observations on the tegument and associated structures of the monogenean Cichlidogyrus halli typicus (Price & Kirk, 1967) Paperna, 1979.

The tegument of the ancyrocephaline monogenean gill parasite Cichlidogyrus halli typicus is basically similar to that of other monogeneans. However, there are some tegumental features shared with relatively few other monogeneans, namely the presence in the surface tegument of extensive regions of homogeneous granular cytoplasm, a close association between myofibres and the basal region of the tegument and the production of two different tegumental secretory bodies by the same cyton. It is suggested that the regions of homogeneous granular cytoplasm found in the troughs between the circular muscle fibres provide some kind of support for the tegument, perhaps related to contraction of the tegumental circular muscle fibres and body shape changes. Three kinds of transtegumental sensory structures are recognized, namely a uniciliated bulb, a bulb bearing a non-ciliary process and a non-ciliated bulb. The latter two kinds are reported for the first time in monogenans. Possible functions of these sensory structures are discussed.     

Ultrastructure of the Tegumental Basement Membrane of Fasciola hepatica(Trematoda)

The fine–structural characteristics of the basement membrane of the tegument of F. hepatica were examined following extraction fixations and tannic acid infiltration. The basement membrane was shown to consist of three layers: lamina lucida, lamina densa, and lamina reticularis. The lamina densa appeared amorphous and homogeneous with tannic acid impregnation. The lamina reticularis appeared as a dense network of 10–12 nm fibrils. Anchoring fibrils cross this layer and form loops. Along their length they contact hemidesmosomes of muscles, thus connecting muscle to muscle and to tegument. The tegument/basement membrane contact is enhanced by extensions of the lamina densa into infoldings of the tegumental basal membrane. Where tegumental spines reach the basement membrane, the contact is reinforced by hemidesmosomes that connect to anchoring fibrils reaching toward the underlying muscles. The basement membrane thus seems to be a complex structure integrating the distal tegumental layer with underlying tissues and transducing muscle contractions to the tegument and its spines.     

Ultrastructure of the tegument of Saccocoelioides godoyi

The tegument of adult Saccocoelioides godoyi Kohn & Froes, 1986 (Digenea: Haploporidae), specimens of which were collected from the intestine of the freshwater fish, Leporinus friderici (Bloch, 1794) (Anostomidae) from the reservoir of Itaipu Hydroelectric Power Station, Parana State, Brazil, was studied by transmission electron microscopy. The tegument comprises an external anucleate layer, covered by a surface plasma membrane and associated glycocalyx. The surface layer is bound by the basal plasma membrane and contains spines, two types of inclusion bodies and mitochondria. Tegumental cell bodies are located beneath the surface musculature and contain a single nucleus, cytoplasm with rough endoplasmic reticulum, mitochondria, ribosomes, and inclusion bodies similar to those found in the external layer. Cytoplasmic strands connect the cell bodies to the external surface layer, suggesting that the inclusion bodies are produced in these cells and pass up into the syncytium, as is known for other digeneans from experimental evidence.     

Cellular organization of the oncosphere of Mosgovoyia ctenoides (Cestoda: Anoplocephalidae)

The ultrastructure of the infective oncosphere of the cestode Mosgovoyia ctenoides (Anoplocephalidae) is described. The surface of the infective oncosphere is covered by a thin cytoplasmic layer of tegument connected by a narrow cytoplasmic process with the binucleate subtegumental cell, situated deeper in the body. Below the basal matrix of the cytoplasmic layer of the tegument are situated wide bands of the peripheral, somatic musculature responsible for body movements. The 3 pairs of hooks and their muscles form a complex hook muscle system, responsible for coordinated hook action. Five major types of cells have been distinguished: (1) a binucleate subtegumental cell, (2) a binucleate penetration gland, (3) 2 nerve cells, (4) numerous somatic cells, and (5) about 6 germinative cells. The approximate number of cells is 24 (26 nuclei, including 2 syncytial structures). The results of this study, when compared with other published reports from other cestode taxa, support previous hypotheses that the progressive reduction of oncosphere cells is an adaptive feature in cestode evolution.     

Paragonimus westermani possesses aerobic and anaerobic mitochondria in different tissues,adapting to fluctuating oxygen tension in microaerobic habitats

We previously showed that adult Paragonimus westermani, the causative agent of paragonimiasis and whose habitat is the host lung, possesses both aerobic and anaerobic respiratory chains, i.e., cyanide-sensitive succinate oxidase and NADH-fumarate reductase systems, in isolated mitochondria (Takamiya et al., 1994). This finding raises the intriguing question as to whether adult Paragonimus worms possess two different populations of mitochondria, one having an aerobic succinate oxidase system and the other an anaerobic fumarate reductase system, or whether the worms possess a single population of mitochondria possessing both respiratory chains (i.e., mixed-functional mitochondria). Staining of trematode tissues for cytochrome c oxidase activity showed three types of mitochondrial populations: small, strongly stained mitochondria with many cristae, localised in the tegument and tegumental cells; and two larger parenchymal cell mitochondria, one with developed cristae and the other with few cristae. The tegumental and parenchymal mitochondria could be separated by isopycnic density-gradient centrifugation and showed different morphological characteristics and respiratory activities, with low-density tegumental mitochondria having cytochrome c oxidase activity and high-density parenchymal mitochondria having fumarate reductase activity. These results indicate that Paragonimus worms possess three different populations of mitochondria, which are distributed throughout trematode tissues and function facultatively, rather than having mixed-functional mitochondria.     

Immunocytochemistry of cytoskeletal proteins in adult Schistosoma mansoni

Antisera to vertebrate actin and actin-binding proteins were used to characterize the cytoskeleton of adult Schistosoma mansoni. Actin, alpha-actinin and tropomyosin immunoreactivities were detected in the cytoplasm of the apical tegument. Antiserum to alpha-actinin bound to the tegumental spines and this protein may be involved in cross-linking of spine actin filaments. Actin, alpha-actinin and tropomyosin antisera bound to the musculature. Strongest immunoreactivity was seen in the parenchyma. Antisera to actin, alpha-actinin, tropomyosin and spectrin bound to parenchyma cells including those of the tubercles, suggesting that these proteins are located in muscle cell bodies. The distribution of cytoskeletal proteins is discussed in relation to tegumental repair processes.     

Schistosoma mansoni: the effects of a subcurative dose of praziquantel on the ultrastructure of worms in vivo

The in vivo effects of a subcutaneously-administered subcurative dose (200 mg/kg body weight of mouse) of praziquantel on the structure of Schistosoma mansoni was investigated. Worms were collected at varying times post-treatment and processed for both SEM and TEM examination. Praziquantel caused extensive structural changes to both male and female worms within 15 min of treatment although variations in the amount of drug-induced damaged was observed between male and female worms. In female worms although some tegumental vacuolation was observed within 15 min, the major structural change was an often extensive vacuolisation of the subtegumental tissues followed by varying degrees of structural disruption to the subtegumental and gastrodermal musculature. In male worms the initial effects were a vacuolisation of parts of the dorsal tegument and loss of tegumental cytoplasm due to the pinching off of evaginations of the outer surface. With increasing time post-treatment there was an increase in the amount of tegumental damage, particularly in male worms, with total disruption of parts of the outer surface occurring. Also in male worms there was an increase in the amounts of vacuolisation of the parenchymal tissues and in the degree of structural damage to the musculature. In those female worms where subtegumental damage was not extensive changes in the structure of the differentiating vitelline cells were noted.     

Antigenic localities in the tissues of Metagonimus yokogawai observed by immunogoldlabeling method]

In order to determine the antigenic localization in the tissues of the adult Metagonimus yokogawai, immunogoldlabeling method was applied using serum immunoglobulins(IgG) of cats which were infected with isolated metacercariae from Plecoglossus altivelis. The sectioned worm tissue was embedded in Lowicryl HM 20 medium and stained with infected serum IgG and protein A gold complex(particle size: 12 nm). It was observed by electron microscopy at each tissue of the worm. The gold particles were observed on the tegumental syncytium as well as cytoplasm of tegumental cells and epithelial lamella of the caecum. The gold particles were not observed on the basal lamina of the tegument, interstitial matrix of the parenchyma, the muscle tissue and mitochondria of the tegument. The gold particles were specifically labeled in the secretory granules in the vitelline cells. They were also labeled on the lumen of bladder and egg shell. The above findings showed that antigenic materials in the tissue of adult worms were specifically concentrated on the tegumental syncytium as well as cytoplasm of tegumental cells and epithelial lamella of the caecum.     

Topography and ultrastructure of the tegument of Lecithochirium musculus (digenea: Hemiuridae), a parasite of the European eel Anguilla anguilla (osteichthyes: Anguillidae)

The tegumental ultrastructure of the stomach fluke Lecithochirium musculus was studied using scanning and transmission electron microscopy. The surface of the tegument was smooth and covered by transverse cytoplasmic ridges. Cobblestone‐like units of the tegument were observed on the ventral surface. Invagination and evagination of the ecsoma induced variations in the tegumental surface. The ultrastructural study revealed that the tegument of L. musculus had a typical syncytial organization with a distal cytoplasm lying over a basal matrix and cytons. Two types of intra‐tegumental sensory structures were observed. Type 1 sensory receptor was a domed‐like fusiform structure consisting of a smooth elevation of the tegument. Four receptors of this type were observed on the anterior dorsal surface of the fluke. Three nerve bulbs filled with electron‐lucent material and mitochondria composed this receptor. Hemispherical electron‐dense collars were observed at the top of the nerve bulbs. Striated rootlets laid just beneath the hemispherical electron‐dense collars. Type 2 sensory receptor presented two morphological variations, i.e., a bulb‐like monolobed structure, and a bulb‐like bilobed structure observed at two different degrees of evagination. For both variations, the nerve bulb enclosed mitochondria, electron‐lucent material, and a conical electron‐dense collar from which extended a striated rootlet. Numerous sensory receptors of this type were observed around the ventral sucker. J. Morphol., 2012. © 2011 Wiley Periodicals, Inc.     

Ultrastructural observations on the redial tegument of Paramphistomum epiclitum from the planorbid snail, Indoplanorbis exustus.

The morphology of the tegument in the redia of Paramphistomum epiclitum (Digenea: Paramphistomidae) resembles that shown by most larval and adult digeneans; an outer surface syncytium is in continuity with the cytoplasm of in-sunken, nucleated cytons. Although tegumental cytons usually contain a single nucleus, some display up to six nuclei. The tegumental syncytium lining the pharynx of P. epiclitum rediae lack underlying cytons. The apical membrane of the tegument is elaborated by folds and microvilli, which presumably facilitate uptake of nutrients and/or exchange of ions involved in osmoregulation. A single type of secretory body, resulting from the fusion of smaller vesicles produced at Golgi complexes in the cytons, occurs throughout the tegument. Uniciliate sensory receptors occur in the surface syncytium particularly around the oral opening.