Phylogeny and paraphyly among tetrapod blood flukes (Digenea: Schistosomatidae and Spirorchiidae)

The blood flukes of turtles (Digenea: Spirorchiidae) and the blood flukes of crocodilians, birds and mammals (Digenea: Schistosomatidae) have long been considered as closely related, but distinct evolutionary lineages. Recent morphological and molecular studies have considered these families as sister taxa within the Schistosomatoidea. Representatives of both families have similar furcocercous cercariae and similar two-host life cycles, but have different definitive hosts, distinct reproductive patterns and different morphologies. Sequences including approximately 1800 bases of the small subunit ribosomal DNA and 1200 bases of the large subunit ribosomal DNA were generated from representatives of eight spirorchiid genera. These sequences were aligned with pre-existing sequences of Schistosomatidae and other representatives of the Diplostomida and analysed for phylogenetic signal using maximum parsimony and Bayesian inference. These analyses revealed that the Spirorchiidae is paraphyletic and that the turtle blood flukes are basal to the highly derived schistosomatids. Three genera of spirorchiids from marine turtles form a sister group to the Schistosomatidae and five genera of spirorchiids from freshwater turtles occupy basal positions in the phylogeny of tetrapod blood flukes. Marine turtles are considered to be derived from freshwater turtles and the results of the current study indicate that the spirorchiid parasites of marine turtles are similarly derived from a freshwater ancestor. The close relationship of the marine spirorchiids to schistosomatids and the basal position of the marine transmitted Austrobilharzia and Ornithobilharzia in the schistosomatid clade suggests that schistosomatids arose after a marine turtle blood fluke ancestor successfully colonised birds.     

Description of embryonic development and ultrastructure in miracidia of Cardiocephaloides longicollis (Digenea,Strigeidae) in relation to active host finding strategy in a marine environment

The functional ultrastructure and embryonic development of miracidia in naturally released eggs of the trematode Cardiocephaloides longicollis were studied using light and transmission electron microscopy. This species has operculated eggs and embryogenesis occurs in the marine environment before an actively infecting ciliated miracidium hatches. Six different developmental stages were identified. The lack of pores in the eggshell indicates its impermeability and the miracidium's dependency on glycogen nutritive reserves, contained in numerous vitellocytes in early embryos. As the development advances, these merge into larger vitelline vacuoles that encircle the miracidium and may aid its hatching. Tissue and primary organ differentiation were observed in advanced stages, i.e., terebratorium, glands, cerebral ganglion, peripheral sensory endings, and eyespots. The anterior part of the body contains a single apical and paired lateral glands, as well as two types of sensory endings, which permit location, adhesion, and penetration of the host. No previous studies describe the embryonic development and ultrastructure of miracidia in strigeids, however, some of the structural features shared with other, well described species with unknown life cycles are emphasised. This study highlights that ultrastructural data have to be interpreted in relation to parasite biology to understand the structural requirements of specific parasite strategies.     

An ultrastructural study of the egg wall surrounding the miracidium of the digenean Brandesia turgida () (Plagiorchiida: Pleurogenidae), with the description of a unique cocoon-like envelope

The intrauterine eggs of the pleurogenid trematode Brandesia turgida (Brandes, 1888), exhibiting advanced stages of miracidial differentiation and fully formed, ciliated miracidia, were examined by means of transmission electron microscopy (TEM). Each embryonated egg is composed of a mature miracidium surrounded by a four-layered egg wall: (1) an outer, anucleate layer external to the eggshell, which forms a thick cocoon; (2) the operculate egg-shell; (3) a small remnant of the compact, granular cytoplasm of the outer embryonic envelope (sensu stricto); and (4) a relatively distinct cellular remnant of the inner embryonic envelope. Layers enveloping the egg apparently play an important role in the protection, metabolism and storage of nutritive reserves for the developing miracidium. The outer, anucleate layer, or cocoon, situated externally to the eggshell and composed of a transparent, electron-lucent substance with numerous dense, osmiophilic islands attached to its peripheral membrane, has never previously been seen in TEM studies of the eggs of parasitic platyhelminths. The origin, formation, functional ultrastructure and chemical composition of this peculiar layer remain enigmatic, although its function appears to be protective. The thick, electron-dense eggshell resembles that of other trematodes, exhibiting a characteristic fissure zone around the operculum. The very small, indistinct remnants of the outer embryonic envelope appear in the form of a very thin, compact, granular cytoplasm closely attached to the inner surface of the eggshell. Conversely, the inner embryonic envelope is frequently apparent at one or both poles of the developed egg as a syncytial envelope formed by the fusion of mesomeres. This envelope, even in eggs containing a fully formed miracidium, still has the features of a metabolically active layer with an energy storage capability. Lysosome-like structures observed in some eggs may be involved in the autolysis of the embryonic envelopes.     

An ultrastructural study of the egg wall surrounding the miracidium of the digenean Brandesia turgida ( ) (Plagiorchiida: Pleurogenidae), with the description of a unique cocoon-like envelope

The intrauterine eggs of the pleurogenid trematode Brandesia turgida ( Brandes, 1888), exhibiting advanced stages of miracidial differentiation and fully formed, ciliated miracidia, were examined by means of transmission electron microscopy (TEM). Each embryonated egg is composed of a mature miracidium surrounded by a four-layered egg wall: (1) an outer, anucleate layer external to the eggshell, which forms a thick cocoon; (2) the operculate egg-shell; (3) a small remnant of the compact, granular cytoplasm of the outer embryonic envelope (sensu stricto); and (4) a relatively distinct cellular remnant of the inner embryonic envelope. Layers enveloping the egg apparently play an important role in the protection, metabolism and storage of nutritive reserves for the developing miracidium. The outer, anucleate layer, or cocoon, situated externally to the eggshell and composed of a transparent, electron-lucent substance with numerous dense, osmiophilic islands attached to its peripheral membrane, has never previously been seen in TEM studies of the eggs of parasitic platyhelminths. The origin, formation, functional ultrastructure and chemical composition of this peculiar layer remain enigmatic, although its function appears to be protective. The thick, electron-dense eggshell resembles that of other trematodes, exhibiting a characteristic fissure zone around the operculum. The very small, indistinct remnants of the outer embryonic envelope appear in the form of a very thin, compact, granular cytoplasm closely attached to the inner surface of the eggshell. Conversely, the inner embryonic envelope is frequently apparent at one or both poles of the developed egg as a syncytial envelope formed by the fusion of mesomeres. This envelope, even in eggs containing a fully formed miracidium, still has the features of a metabolically active layer with an energy storage capability. Lysosome-like structures observed in some eggs may be involved in the autolysis of the embryonic envelopes.     

Life cycle of Psilotrema simillimum (Mühling, 1898) (Trematoda: Psilostomidae)

Psilotrema simillimum has one intermediate host, the mollusk Bithynia leachi. Cercariae emerging from the mollusk encyst in the environment. Adolescariae become infectious in 3-7 days. In the definitive host trematodes become mature on the 9th day. The development of miracidium in an egg finishes in 19 days at 20-24C. Egg, miracidium, redia, cercariae, adolescariae and marites obtained in the experiment are described.     

Composition, secretion, and fate of the glands in the miracidium and sporocyst of Fasciola hepatica L

The anterior end of the miracidium of Fasciola hepatica contains a large flask-shaped apical gland and four unicellular lateral glands, all of which have ducts which pass to the tip of the apical papilla. These glands appear to be involved in penetration of the larva into the snail host. The apical gland secretes as the miracidium proves the epidermis of the host before attachment. It seems likely that its secretion is a chemical which lyses the epidermal cells. The lateral glands are PAS-positive and may contain a neutral mucopolysaccharide. They also secrete as the miracidium probes the snail and a layer of PAS-positive material may be seen at the leading edge of the apical papilla as the larva penetrates into the host. Both the apical gland and the lateral glands may be visible in the sporocyst for several days after penetration.     

Ultrastructural and histochemical observations on the epidermis, presumptive tegument and glands of the miracidium of Gigantocotyle explanatum (Trematoda:Paramphistomidae)

Dunn T. S., Hanna R. E. B. and Nizami W. A. 1987. Ultrastructural and histochemical observations on the epidermis, presumptive tegument and glands of the miracidium of Gigantocotyle explanatum (Trematoda: Paramphistomidae). International Journal for Parasitology17: 885–895. The miracidium is invested with 20 ciliated epidermal cells arranged in four tiers (6: 8: 4: 2 = 20). Non-ciliated ridges of cytoplasm, located between the epidermal cells, are continuous with an extensive multivesiculate syncytium which underlies the body musculature and comprises the main bulk of the miracidium. It is suggested that the syncytium represents the presumptive sporocyst tegument. Two distinct types of glands are present in the anterior region of the miracidium, viz. a large, syncytial apical gland and a single pair of small, unicellular lateral glands. The apical papilla is formed by the bounding membrane of the apical gland, which is elevated into a complex network of anastomosing lamellae. The lateral glands terminate in discrete rosetteshaped areas on the apical papilla. The possible function of glands in digenetic miracidia and the nature of their secretions are discussed.     

Proteomic Analysis of the Schistosoma mansoni Miracidium

Despite extensive control efforts, schistosomiasis continues to be a major public health problem in developing nations in the tropics and sub-tropics. The miracidium, along with the cercaria, both of which are water-borne and free-living, are the only two stages in the life-cycle of Schistosoma mansoni which are involved in host invasion. Miracidia penetrate intermediate host snails and develop into sporocysts, which lead to cercariae that can infect humans. Infection of the snail host by the miracidium represents an ideal point at which to interrupt the parasite’s life-cycle. This research focuses on an analysis of the miracidium proteome, including those proteins that are secreted. We have identified a repertoire of proteins in the S. mansoni miracidium at 2 hours post-hatch, including proteases, venom allergen-like proteins, receptors and HSP70, which might play roles in snail-parasite interplay. Proteins involved in energy production and conservation were prevalent, as were proteins predicted to be associated with defence. This study also provides a strong foundation for further understanding the roles that neurohormones play in host-seeking by schistosomes, with the potential for development of novel anthelmintics that interfere with its various life-cycle stages.     

Diplostomum spathaceum (Rud. 1819): effect of miracidial age and lifespan on miracidial infectivity

Experiments were performed to study the effect of age and lifespan on the infection success of Diplostomum spathaceum miracidia. Specimens of Lymnaea peregra and L. stagnalis were individually exposed to single miracidia of D. spathaceum of different ages under conditions of constant illumination at 20 degrees C. The life-span of the free-swimming miracidium of D. spathaceum is 24 h at 20 degrees C. It was observed that as the miracidium ages, its ability to successfully infect snails declines rapidly.     

Der stammesgeschichtliche Aussagewert der Pterostigma-Oberflächenfeinstruktur bei Odonaten 1,2

The phylogenetic significance of ultrastructure of the pterostigma surface in Odonata Studies of the pterostigma surface in dragonflies with the stereoscan microscope have shown that its ultrastructure presents a phylogenetic significance and indicates evolutionary affinities. The constitution of this ultrastructure is not suitable for the distinction of genera; according to the results obtained up to now, all genera of the same family have the same surface structure. In the present paper, we have studied particularly the complex super-family of Calopterygoidea, and a new phylogenetic arrangement of its different families is suggested.     

First occurrence of Schistosomatidae infecting Aplexa hypnorum (Gastropoda, Physidae) in France

Due to the recrudescence of cercarial dermatitis in the world, larval Schistosomatidae have been researched during 20 months in gastropods of stagnant fresh waters in a wetland. Brevifurcate ocellate cercariae have been detected after crushing in a species of Physidae, Aplexa hypnorum, with a prevalence of 6.52%. Up to now, this species had never been found infected by larval trematodes. Lymnaeidae, Planorbidae and other Physidae didn't harbour schistosomatids. Cercariae of A. hypnorum present furcal fin-folds and the length of the tail stem is inferior to that of the body. Only cercariae of Heterobilharzia americana, Schistosomatidae of Carnivora in America, have also these two features. This species, not described in Physidae, is an agent of the human cercarial dermatitis. Schistosomatid cercariae in american species of Physidae have been compared with that of A. hypnorum. Brevifurcate ocellate cercariae of A. hypnorum, possible agent of the cercarial dematitis, probably belong to a new species with unknown genus.     

Specific and non-specific phosphatases in the miracidium of Fasciola hepatica L.

Localization and activities of alkaline phosphatase, ATPase, 5-nucleotidase, glucose-6-phosphatase, thiamine pyrophosphatase and nucleoside diphosphatase were studied in the miracidium of Fasciola hepatica L. Except for nucleoside diphosphatase whose activity in the miracidium was not observed, all the enzymes were most active in the archenteron, protonephridia and nerve ganglion. This localization of the reaction intensity allows the inference that the three organs mentioned are sites of both intense carbohydrate metabolism and lively active transport. The role of phosphatases in carbohydrate metabolism is discussed.     

Lecithochirium furcolabiatum (Jones 1933), Dawes 1947: the miracidium and mother sporocyst.

Experimental infections of the marine topshell Gibbula umbilicalis with Lecithochirium furcolabiatum (Digenea: Hemiuroidea) have allowed the development of a model system which will enable further studies of the molluscan host response. The long-lived intertidal prosobranch host is easily maintained in the laboratory, and experimental infection rates of 98% were consistently achieved. The miracidium and mother sporocyst have been studied at both light and ultrastructural levels, providing the first account of the morphology of these stages in Hemiuridae. The ingested egg hatches within the host intestine, treatment with L-cysteine and alkaline pH stimulating miracidial emergence in vitro. The general body surface of the miracidium is devoid of spines or cilia, the latter being restricted to four plates near the anterior extremity. The miracidium swims actively prior to penetration of the gut wall, the sporocyst being released from the miracidial epidermal coat within the haemocoel. Within 5 weeks of infection, the filamentous mother sporocyst contains 1 to 3 oval germ balls, daughter sporocysts being recorded free within the digestive gland haemocoel 7 weeks later. Twenty three weeks after ingestion of eggs, the daughter sporocyst extends into the host gill filaments, containing cystophorous cercariae ready for emergence.     

Schistosoma mansoni: origin and expression of a tegumental surface antigen on the miracidium and primary sporocyst

A monoclonal antibody, recognizing a carbohydrate epitope associated with several tegumental surface components on Schistosoma mansoni primary sporocysts, was used to follow tegumental formation during transformation of the miracidium to sporocyst and its subsequent development in vitro and in vivo. Indirect fluorescent antibody and direct immunogold labeling methods confirm a structural connection between the intercellular ridges and a submuscular, multinucleate syncytium in the miracidium. Immunoreactive vesicles within this latter system directly contribute to elaboration of the tegumental surface membrane, through the process of membrane fusion. Lateral expansion of intercellular ridges by vesicular fusion ultimately result in fully transformed sporocysts exhibiting vesicular membrane epitopes as prominent tegumental surface components. Light microscopical and ultrastructural observations, together with Western immunoblot analyses, suggest a gradual depletion of intracellular and surface immunoreactive material of vesicular origin in primary sporocysts grown in culture for up to 12 days. In contrast, similar immunoreactive vesicles appear to be continuously synthesized throughout in vivo primary sporocyst development. Monoclonal antibody reactive epitopes appear to be uniquely expressed in the miracidium/primary sporocyst since similar molecules are absent from daughter sporocysts, cercariae, adults, and snail tissues.     

Parthenites and cercaria of trematodes in the snails Lymnaea saridalensis (Gastropoda, Pulmonata), which inhabits the watershed area of Chany Lake (the South of Western Siberia)

The full list of parthenogenetic larvae and cercaria is presented for the first time for the freshwater snail L. saridalensis (Gastropoda, Pulmonata), which inhabits the watershed area of Chany Lake. It was found that this snail species plays a significant role as the first intermediate host in the life cycles of trematodes in the southern part of Western Siberia. The invasion parameters were calculated for different parasite species. It was found that 50% of the L. saridalensis population serves as the first intermediate host for eleven trematode species that belong to six families: Plagiorchiidae, Echinostomatidae, Diplostomatidae, Strigeidae, Notocotylidae, and Schistosomatidae. The prevalence of infection by each trematoda species in L. saridalensis was determined. Five species of trematodes from the Plagiorchiidae and Echinostomatidae families formed the center of the parasite community, viz., the species Plagiorchis elegans, P. mutationis, Opisthioglyphe ranae, Molinella anceps, and Echinoparyphium aconiatum. Two species, Plagiorchis mutationis and P. multiglandularis, were recorded in the studied area (the Chany Lake watershed area) for the first time at the stages of parthenite and cercaria. It was also found that 1% of L. saridalensis population have multiple (mostly two-species) infections.     

Schistosoma Mansoni Miracidium Under Phase Difference Microscopy

The living, immobilized miracidium form of the Schistosoma mansoni has been photographed at the same plane under ordinary bright field and under phase contrast illumination. Under the latter method more of the internal structures are visible.     

Cornea of ommatidia in Lepidoptera (Insecta)--a scanning electron microscope study

The external surface of facets of representatives of 19 families of Lepidoptera is discussed and illustrated. Two types of structures are recognized, this with nipples predominate. The other structures (pleats) developed probably in the course of a reduction. The ultrastructure of surface in the form of granulation is described.     

Schistosomiasis and nutritional myopathy in a Brazilian tapir (Tapirus terrestris)

Gross lesions suggestive of severe hepatoenteropathy and myopathy were noted in a 4.5-yr-old Brazilian tapir (Tapirus terrestris) from a zoo in Michigan (USA). The major microscopic lesions were granulomatous hepatitis and hemorrhagic enteritis associated with non-operculated eggs compatible with those of the Schistosomatidae (Digenea). Skeletal muscle and tongue contained foci of severe acute myodegeneration and necrosis. The hepatic vitamin E value of 1.3 ppm dry weight was considered critically low.     

Comparative study of sperm ultrastructure of five species of teiid lizards (Teiidae, Squamata), and Cercosaura ocellata (Gymnophthalmidae, Squamata)

Sperm ultrastructure of five teiid lizards (Callopistes flavipunctatus, Crocodilurus amazonicus, Dicrodon guttulatum, Dracaena guianensis, and Teius oculatus), and the gymnophthalmid Cercosaura ocellata is described for the first time. Comparisons of sperm ultrastructure among these species and with those of previously examined teiids and gymnophthalmids revealed that the two groups of Teiioidea (Gymnophthalmidae and Teiidae), and the two subfamilies of Teiidae (Teiinae and Tupinambinae) could be distinguished on the basis of sperm ultrastructure data. Significant differences in sperm dimensions between Cnemidophorus and Aspidoscelis support the recent splitting of these two lineages into different genera. Our results revealed high levels of inter-generic variability in sperm ultrastructure within Teiidae, which produces a data set useful in analyzing relationships between genera and families. In phylogenetic analyses, however, sampling multiple species within teiid genera is essential and recording sperm measurements may profitably complement qualitative ultrastructural characters, maximizing the information content of these structures.