The ultrastructure and chemical composition of the proboscis hooks and surrounding tegument of Acanthocephalus lucii (Müller, 1776), a parasite of European perch, Perca fluviatilis Linnaeus, were examined using scanning (SEM) and transmission (TEM) electron microscopy and X-ray microanalysis (EDXA). The blade of middle hooks consists of three layers: an outer homogeneous layer, an inner heterogeneous layer and a central core. TEM observation revealed the presence of hollow tubes, which spaced the central core; fibrous inner hook layer surrounded by an electron-dense margin and the basal tegumental layer filled with electron-dense bodies and outer layer. We found for the first time that the so-called ''epidermal covering'' surrounding of the exposed hook blade (outer hook layer) is a modified striped portion of the tegumental layer and there are no special contact sites between these two morphologically different structures, i.e. striped layer of the syncytial tegument and following proper outer hook layer, which is a homogeneous, moderately electron-dense layer of ~0.3 µm in thickness. The hook root is embedded into subtegumental fibrous layer. X-ray microanalysis of both the surface and internal parts of A. lucii hooks demonstrated the presence of calcium, magnesium, phosphorus and sulphur. The highest concentration of sulphur was recorded at the tip of hooks, whereas the middle part of the hooks was most rich in calcium, phosphorus and magnesium. The proximal part of the hooks contained lower concentrations of sulphur, calcium and phosphorus. In the proboscis tegument, only two elements, calcium and silicon, were found. The differences observed in the chemical composition of the hook ''epidermal covering'' and the proboscis tegument support our ultrastructural findings that the hook tegumental covering is a modified structure compared with that of the general proboscis tegument.
Influence of moderate chilling stress on vascular bundle sheath cell (BSC) and especially mesophyll cell (MC) chloroplasts of mature maize leaves was studied by electron microscopy and stereology. Plants of two inbred lines of maize, differing in their photosynthetic activity, and their F1 hybrids were cultivated during autumn in heated or unheated glasshouse. Generally, chilling temperatures resulted mainly in the decrease in stereological volume density (VD) of both granal and intergranal thylakoids of MC chloroplasts, while the ratio of granal to all thylakoids (granality) was less affected. The VD of peripheral reticulum and plastoglobuli usually increased after cold treatment of plants. The volume of MC chloroplasts usually increased under chilling stress, the shape of the chloroplasts changed only slightly. The ultra-structure of chloroplasts differed between individual genotypes; chilling-stressed hybrid plants showed positive heterosis particularly in the granal thylakoids' VD of MC chloroplasts. and J. Kutík ... [et al.].
Data on external ultrastructure of myxospores and internal ultrastructure of advanced pseudoplasmodia and myxospores of topotypic samples of Sphaerospora ranae (Morelle, 1929) from Rana dalmatina Bonaparte are provided, together with in situ hybridisation results. In both frogs examined, the infection was restricted to renal tubules and corpuscles. The infection site restriction was confirmed by light and transmission electron microscopy, as well as by in situ hybridisation. In addition, large myxospore masses measuring up to 500 μm were detected in seminal vesicles. Only late-sporogonic stages, i.e. pseudoplasmodia harbouring immature and/or mature myxospores, were observed and analysed. Scanning electron microscopy revealed that spores have smooth surface with exception of posterior valvular bulges, which possess numerous outwards opening internal canals. As revealed by both scanning and transmission electron microscopy, the canals are continuous invaginations of the outer spore surface. Myxospores of S. ranae are characterised by the presence of two uninucleate sporoplasms, bilayered polar capsules, S/H-shaped polar filaments in transversal section and multilayered polar filament eversion pole plugging complex. Ultrastructural observations are discussed in the context of available data for other species of Sphaerospora sensu stricto and apparent synchronisation of myxospore shedding with a brief aquatic breeding phase of vertebrate intermediate host is highlighted.
Four new species of monoxenous kinetoplastid parasites are described from Brachycera flies, namely Wallaceina raviniae Votýpka et Lukeš, 2014 and Crithidia otongatchiensis Votýpka et Lukeš, 2014 from Ecuador, Leptomonas moramango Votýpka et Lukeš, 2014 from Madagascar, and Crithidia pragensis Votýpka, Klepetková et Lukeš, 2014 from the Czech Republic. The new species are described here based on sequence analysis of their spliced leader (SL) RNA, glycosomal glyceraldehyde 3-phosphate dehydrogenase (gGAPDH) and small subunit (SSU) rRNA genes, as well as their morphology and ultrastructure. High-pressure freezing and Bernhard's EDTA regressive staining, used for the first time for monoxenous (one host) trypanosomatids, revealed the presence of viral particles with cytosolic localization in one and unique mitochondrial localization in another species. In accordance with previous observations, our results emphasize a discrepancy between morphology and molecular taxonomy of the family Trypanosomatidae. All four newly described species are represented by typical morphotypes (mainly choano- and promastigotes) and are virtually indistinguishable from other monoxenous trypanosomatids by morphology. Nevertheless, they all differ in their phylogenetic affinities. Whereas three of them grouped within the recently defined subfamily Leishmaniinae, which includes numerous representatives of the genera Leishmania Ross, 1903, Crithidia Léger, 1902 and Leptomonas Kent, 1880, the fourth species clusters together with the ''collosoma'' clade (named after ''Leptomonas'' collosoma Wallace, Clark, Dyer et Collins, 1960). Here we demonstrate that the ''collosoma'' group represents the elusive genus Wallaceina Podlipaev, Frolov et Kolesnikov, 1999. We redefine this genus in molecular terms based on similarities of the respective molecular markers and propose to use this taxon name for the group of species of the ''collosoma'' clade.
Ultrastructural characteristics of progenetic and monoxenic Archigetes sieboldi Leuckart, 1878 from the oligochaete Limnodrilus hoffmeisteri Claparède are described. Our observations demonstrate that progenetic Archigetes sieboldi shares characteristics of both larval (progenetic) and adult stages. The primary larval characteristics are: the presence of a cercomer; a surface filamentous coat covering the whole worm; the presence of the penetration glands and the absence of tegumental ones; wide sarcoplasmic processes connecting the circular and longitudinal external tegumental muscles; the absence of the dense homogenous zone of the basal lamina beneath the epithelial cytoplasm of all reproductive organs and ducts; non-functional gonopores; and an orthogonal plan of nervous system with three pairs of longitudinal nerve trunks. The principle adult characteristics are: oogenesis, spermiogenesis and vitellogenesis that produce fertilized eggs; the uterine glands; a well-developed longitudinal tegumental muscle layer between tegumental cytons; and the presence of different microtriches. As a result of this progenetic development there has been a secondary reduction in the life cycle of A. sieboldi. It is postulated that a similar process of progenesis may have played a major role in the early evolution of the Caryophyllidea by first appearing in a plerocercoid stage of an ancestral strobilate cestode from fish.
Mabuya vitatta (Olivier) (Scincidae) and Agama stellio (L.) (Agamidae) were infected with Hemolivia mariae Smallridge et Paperna, 1997 by ingestion of tick viscera from Amblyomma limbatum Neumann, fed as nymphs on naturally infected Australian sleepy lizards, Tiliqua rugosa Gray. The unnatural infection apparently interfered with the developmental schedule of the parasites. Transmission electron microscopic images of merogonic stages were obtained, as well as images of early developing gametocytes. Tissue and intraerythrocytic meronts were bound by a hardened wall. Intraerythrocytic gametocytes were lodged in a parasitophorous vacuole, which was filled with granular material, and were bound by a two-membrane wall. Small and large osmiophilic bodies were located in a sub-pellicular position. With differentiation, the wall membranes tightened with the parasitophorous vacuole wall, and the osmiophilic bodies disappeared. The outer parasite membrane consolidated into a thick encasing with distinct sutures. Late infection in A. stellio comprised gametocytes only.
The scolex surface of the mature spathebothriidean Cyathocephalus truncatus (Pallas, 1781), a parasite of the brown trout Salmo trutta fario L., was studied using scanning and transmission electron microscopy. A particular attention was paid to microtriches, unique structure on the surface of the Cestoda. The scolex of C. truncatus is covered with two types of filiform microtriches (filitriches): aciculate (≈ 3 µm long) and capillate (≈ 10 µm long). Capillate microtriches, which have never been reported in any other spathebothriideans, are described for the first time using transmission electron microscopy. The tegument covered with filiform microtriches only (no spiniform microtriches are present) is typical of cestode groups supposed to be the most basal, e.g., Gyrocotylidea, Spathebothriidea, and Caryophyllidea.
Ultrastructural characters of spermiogenesis and mature spermatozoon of Triaenorhina rectangula (Fuhrmann, 1908) are examined by transmission electron microscopy. Spermiogenesis follows the Bâ and Marchand's Type III spermiogenesis of cestodes. The process begins with the formation of a differentiation zone containing two centrioles and a cytoplasmic protrusion. The centrioles are associated with vestigial striated roots. One of the centrioles develops a free flagellum externally to the cytoplasmic protrusion. After a slight rotation, the free flagellum fuses with the cytoplasmic protrusion. In the final stage of spermiogenesis, a single crested body appears in the anterior part of the differentiating spermatozoon. The anterior extremity of the mature spermatozoon is characterised by an apical cone and a single crested body. The axoneme is of the 9+''1'' trepaxonematan type. A periaxonemal sheath and electron-dense rods are described in some parts of the mature spermatozoon. The nucleus is electron-dense and spirally coiled around the axoneme. The cortical microtubules are spirally arranged at an angle of about 40° to the spermatozoon axis. The present results show that the ultrastructural characters of spermiogenesis and mature spermatozoon of T. rectangula resemble most closely those in taeniids and metadilepidids. The comparison of these results with the only previous spermiological description of a paruterinid species reveals differences relative to the occurrence of filamentous rods of electron-dense material versus intracytoplasmic walls in the mature spermatozoon that may reflect the polyphyletic character of the Paruterinidae.
Ultrastructural analysis revealed that the spermatozoon of Discocotyle sagittata (Leuckart, 1842) is composed of two parallel axonemes, mitochondrion, nucleus and cortical microtubules. The nucleus, which occupies a central/distal position and has an unusual crescent-shaped profile, is slightly shorter than the mitochondrial rod. The two axonemes, which are of unequal length, and the cortical microtubules (up to 68 forming a continuous ring in the principal region) extend almost the entire length of the spermatozoon. A fold of the plasma membrane creates a unilateral flange or undulating membrane. Epifluorescence microscopy indicated that spermatogenesis gives rise to clusters of 64 spermatids connected to a common cytophore. Spermiogenesis and the structure of the filiform sperm of D. sagittata conform to the typical polyopisthocotylean pattern.