Comparison of surface topography of three species of Diphyllobothrium (Cestoda, Pseudophyllidea) by scanning electron microscopy

Stereoscan observations on the surface topography of Gastrothylax crumenifer (Creplin, 1847) Poirier, 1883 and Paramphistomum epiclitum Fischoeder, 1904 (Trematoda: Digenea)

The critical-point-dried specimens of Gastrothylax crumenifer (Creplin, 1847) Poirier, 1883 and Paramphistomum epiclitum Fischoeder, 1904, both recovered from the rumen of sheep, were studied by scanning electron microscopy at magnifications ranging from 10 to 10,000 x to reveal the structural differences of the tegument between the two species.

In G. crumenifer, both dorsal and ventral surfaces have tubercle-like tegumental elevations, devoid of spines. A row of prominent, regularly arranged, button-like protuberances encircle the rim of mouth. It is suggested that these are sensory in nature. The lining of the buccal tube also bears papillae, some of which appear balloon-like. The tegument near the outer acetabular rim is thrown into prominent ridges bearing groups of six to eight small papilla-like elevations. Towards the interior of the acetabular cavity this pattern merges into one with stout, finger-like projections with groups of papillae at their blunt tips. From their structure, these projections appear to aid strong anchorage to the host's surface and the papillae to be secretory.

P. epiclitum has a similar tuberculated pattern on the dorsal and ventral surfaces. In the oral region, the tegument has some irregular, patch-like elevated areas. The acetabular surface is thrown into a pattern of deep folds and craters.

Researches on Pseudophyllidea (Carus, 1813) in the south of Chile. IV Occurrence of Diphyllobothrium dendriticum (Nitzch)

Experimental infections were established with Diphyllobothrium sp. plerocercoids obtained from Salmo gairdneri. a fish introduced at the beginning of the 1900s in the lake region of Chile. These permitted us to obtain adult parasites in Larus dominicanus and Canis familiaris.

The histological features of the plerocercoids, their relation to the host, adult pattern and susceptibility of hosts allowed us to determine the presence of Diphyllobothrium dendriticum (Nitzch) for the first time in South America in the lacustrine region of southern Chile.

It is believed that this cestode was introduced to this ecosystem by infected persons travelling from North America or Europe or, alternatively, brought by migratory birds, e.g., Sterna hirundo, S. paradisea or Larus pipixcan on their winter visits to South America.

Ultrastructure of the proglottid tegument (neodermis) of the cestode Echinophallus wageneri (Pseudophyllidea: Echinophallidae), a parasite of the bathypelagic fish Centrolophus niger

Ultrastructural data are provided on the tegument (or neodermis) of proglottids of the cestode Echinophallus wageneri Monticelli, 1890, the first representative of the family Echinophallidae (Pseudophyllidea), parasites of bathypelagic fish, studied using transmission and scanning electron microscopy. The surface of the ventral concave side of proglottids is covered with filiform microtriches about 1.7 microm long. Their glycocalyx, although very thick, is less extensively developed compared to that on digitiform microtriches localized on the dorsal side of the proglottids, which is also covered with filiform microtriches. The digitiform microtriches of the convex dorsal side are about 0.6 microm long, with a very short, rounded spine and the extraordinarily extensive glycocalyx seen as flocculent material. Short digitiform microtriches of E. wageneri seem to differ from microthrix types previously reported in other cestodes by transmission electron microscopy. The posterodorsal margin of all proglottids is typical in possessing a transverse band of large spiniform, tusk-shaped microtriches with a very long spine (approximately 13 microm in length), merged with filiform microtriches. Marked regional differences found in the morphology and distribution of microtriches on the proglottids of E. wageneri may be related to the different functions of the individual parts of the strobila because of the curling of the tapeworm body within the intestine of its fish host.

COMPARISON OF MICROTHRIX ULTRASTRUCTURE AND MORPHOLOGY ON THE PLEROCERCOID AND ADULT SCOLEX OF CALLIOBOTHRIUM CF. VERTICILLATUM (TETRAPHYLLIDEA: ONCHOBOTHRIIDAE)

The distal bothridial surfaces of adult triloculate onchobothriids are covered with short structures that have been tentatively classified as very short filitriches, but this hypothesis has never been tested. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) were used to investigate microthrix morphology in the plerocercoid and adult forms of Calliobothrium cf. verticillatum, a triloculate onchobothriid tapeworm from Long Island Sound (Connecticut). Plerocercoids of C. cf. verticillatum were collected from the anterior midgut ceaca of Pagurus pollicaris Say, 1817 (flat-clawed hermit crab), and adults were collected from the spiral intestine of the dusky smooth hound Mustelis canis (Mitchell, 1815). Two plerocercoids and 2 adults were examined using SEM; 2 plerocercoids and 2 adults were examined using TEM. Microthrix distribution and morphology (including measurements of total length, base length, shaft length, and base width) were investigated on all surfaces of the plerocercoid and adult scolex. Slender filitriches and large bladelike spinitriches were observed extending from the tegument of plerocercoid and adult forms. The filitriches were found to have significantly narrower bases than the spinitriches (65-167 nm vs. 466-1,936 nm, respectively). The scolex proper of the plerocercoid and adult forms were found to have filitriches of medium-length and bladelike spinitriches. The distal bothridial surfaces differed dramatically in microthrix morphology between plerocercoid and adult forms; on the distal surfaces of the plerocercoids were long filitriches and bladelike spinitriches. However, the distal surfaces of the adults had short structures (previously hypothesized to be short filitriches) and a few bladelike spinitriches. Serial transverse sections revealed that the short structures on the distal bothridial surfaces of the adults were homologous with filitriches. They included all of the structural components of a filithrix as well as a base width that conformed to the filitriches found on other surfaces. The bothridial margins of the plerocercoid and adult forms had a microthrix pattern similar to that seen on the proximal bothridial surfaces except that the filitriches on the margins were significantly longer than those found anywhere else on the bothridia. The most dramatic difference between the plerocercoid and adult forms occurred on the distal bothridial surfaces, where the filitriches of the adult cestodes were significantly shorter and narrower, and the spinitriches were almost entirely lacking.

Microtriches of tetraphyllidean metacestodes from Western Mediterranean striped dolphins (Stenella coeruleoalba)

The tegumental structures of two types of tetraphyllidean plerocercoids and two types of merocercoids (Phyllobothrium delphini and Monorygma grimaldii) from Mediterranean striped dolphins, Stenella coeruleoalba, are described for the first time using scanning electron microscopy. The tegument of all of the specimens was fully covered with microtriches. Four basic types were found: filitriches, blade-like spinitriches of different sizes and shapes, cone-shaped spinitriches (with two parallel small projections of equal length at the apex), and crowned cylindrical spinitriches (with 6-7 small papillae forming a crown at the apex); the two latter types are newly described. The two types of plerocercoids had a similar morphology and distribution of microtriches; in addition, cilium-like projections appeared interspersed among the microtriches on the apical sucker, accessory suckers, and distal bothridial loculus. Merocercoids exhibited a greater variety of tegumental structures, especially on the distal bothridial loculus. Both merocercoid types had regularly spaced papillae or "buttons" on the accessory suckers and the distal bothridial loculus that were composed of a central cilium-like projection surrounded by numerous filitriches. However, crowned cylindrical spinitriches were specific to P. delphini and cone-shaped spinitriches were specific to M. grimaldii. Differences in the morphology and distribution of scolex microtriches of adult cestodes have been considered useful for species identification. A previous molecular study has suggested that P. delphini and M. grimaldii are actually different congeneric species. Our study has shown that significant differences in the morphology and distribution of microtriches occur between these species at the merocercoid stage.

Nomimoscolex semenasae n sp (proteocephalidea: Monticelliidae), a cestode parasite of Diplomystes viedmensis (Pisces: Siluriformes) from the Patagonian region of Argentina

Nomimoscolex semenasae n. sp. is described from the primitive fish Diplomystes viedmensis (Siluriformes) from the Patagonian region of Argentina. The new species is placed in Nomimoscolex because of the cortical position of the vitelline follicles, medullary position of the testes, ovary and uterus, and having a scolex with four uniloculate suckers. N. semenasae differs from all other species in the genus by the following combination of characters: (1.apical organ absent; (2). strobila acraspedote; (3). vagina anterior or posterior to cirrus-sac and lacking a sphincter; (4). testes in one irregular layer and in two fields connected anteriorly; (5). uterine stem cortical in immature proglottides, growing from cortical stem into medullary region in mature proglottides; (6). long uteroduct; and (7). presence of spiniform microtriches on all regions of the scolex, proliferation zone and immature proglottis. This is the first record of a proteocephalidean tapeworm in D. viedmensis and in the family Diplomystidae.

The scanning electron microscopy of scolices in a case of hydatid cyst from human liver

The scanning electron microscopic (SEM) features of hydatid scolices from a case of hydatid disease of the liver are described. The scolex when fully everted has a double circle of hooklets which occupy a large area of the parasite. The hooklets are inserted into the rostellum with one row of hooklets overlapping the other. Each hooklet is about 20 to 40 um long, has a basic round structure sharp at the distal end and broadens as it curves towards the point of insertion at the rostellum, where 2 blunt projections correspond to the 2 annular bundles of muscle fibres at the orifice of the scolex. The function of the hooklets is not fully understood but they are possibly used for anchorage and/or for the purpose of propulsion in a fluid medium by the act of invagination and evagination of the hooklets.

Ultrastructure studies on the papillae and the nonciliated sensory receptors of adult Spirometra erinacei (Cestoda, Pseudophyllidea)

The small numerous papillae on the ventral surface of the gravid proglottid of adult Spirometra erinacei were studied by scanning electron microscopy. The arrangement of clumps of papillae was recognized on the surface of the central portion around the genital atrium, with lateral clumps being located above a pair of longitudinal nerve cords and marginal ones, on both sides of the proglottid. By transmission electron microscopy, two types of nonciliated sensory receptors were observed within the papillae. The type I, single receptor was embedded within a papilla. This dome-like sensory receptor contained two electron-dense collars and four rootlets surrounded by numerous thin filaments. The type II receptor was found arranged in groups in the area between the papillae, and the apical end was exposed to the external environment. This simple, club-like sensory receptor contained electron-lucent vesicles and microtubules. We believe that the papillae play an important role in cross-insemination.

Scanning electron microscopic study of four Diphyllobothrium species

Three-dimensional observation was carried out on plerocercoids and adults of Diphyllobothrium dendriticum, D. ditremum, D. latum, and D. vogeli using scanning electron microscopy. The species-specific differences between plerocercoids were recognized in the shapes of the whole body, scolex, and bothrium and the wrinkle pattern on the body surface. The differences between adult worms were also observed in the shapes of the scolex, neck, and genital papillae around the genital pore and the pattern on the egg surface. The significance of species specificity in the three-dimensional morphology of diphyllobothriid cestodes is briefly discussed.

[Studies On The Bladder Worm, Cysticercus Cellulosae: The Ultrastructure Of C. Cellulosae]

An electron microscopic study was performed to know the basic tegumental structure of Cysticercus cellulosae. The scolex and bladder portions of cysticerci (human and porcine strains) were prepared for transmission and scanning electron microscopy by conventional procedures. In general, the tegument of C. cellulosae showed the basic ultrastructure of cestode tegument on electron micrographs. The teguments of both scolex and bladder portions consisted of such components i.e., an outer vesicular layer with numerous microtriches and inner fibrous layer. Below the fibrous layer, there were layers of muscle bundles and tegumental cells. The microtriches which covered the surface of cysticercus revealed two distinctly different shapes. The characteristic bladder-like, elongated pyramid shaped 'tetrahedral form' was observed on the surface of the scolex portion, whereas the elongated cylindrical 'filamentous form' was distributed on the surface of bladder portion. In spite of the difference of isolated host and location, the cysticerci showed the same result. But dimensional variations of the tegument according to topography of the worm were observed. The possibility of application in making differential diagnosis from other larval cestodes and possible functions of this larval tegument were discussed.

An ultrastructural study of the microtriches of adult Proteocephalus tidswelli (Cestoda: Proteocephalidea)

Ultrastructural observations on adult Proteocephalus tidswelli revealed a marked microtrichial polymorphism. Structural and dimensional variations of microtriches between different regions of the strobila and scolex, as well as within the same region, were observed. The authors suggest that microtriches are involved in a diversity of functions, and possible functional activities are discussed.

The development of the tapeworm Diphyllobothrium latum (L. 1756) (Cestoda; Pseudophyllidea) in its definitive hosts, with special references to the growth patterns of D. dendriticum (Nitzsch, 1824) and D. ditremum (Creplin, 1827)

When Diphyllobothrium latum develops from larva to adult in a definitive host, it first sheds the entire larval 'body' before growth of an adult strobila starts. This process of shedding off the entire larval abothrial extremity, piece by piece, takes about 48 h. By this time the larva has usually reached the anterior third of the small intestine of the host. D. dendriticum and D. ditremum develop quite differently, although exhibiting similar anterior migrations. In these two species the larvae develop directly into adults without the larval 'body' first being shed. The implications of the observed differences in growth pattern between these three species of Diphyllobothrium to the classification of diphyllobothriid cestodes is discussed briefly.

A marine Diphyllobothrium plerocercoid (cestoda, pseudophyllidea) from blue whiting (micromestius poutasson)

A type of Diphyllobothrium plerocercoid found in blue whiting, Micromestius poutasson, caught near the north edge of the Faeroe Banks, is described. The most dominant characters of these larvae are their typical dorsoventrally flattened body and their fully extruded and "adult"-like scolex. A morphological comparison with perocercoids of D. dendriticum, D. ditremum and D. latum is given.

Ultrastructural studies on Diphyllobothrium ditremum and D. dendriticum (Cestoda, Pseudophyllidea), with emphasis on the scolex tegument and the tegument in the area around the genital atrium

The scolices of D. ditremum and D. dendriticum are similar in regard to general morphology and ultrastructure of the tegument. At the scolex apex and along the upper bothrial edges sensory endings are numerous. The inner bothrium surface of D. ditremum appears to be plain or smooth, the distal cytoplasm is only about 0.6 mum thick and covered with long and slender microtriches. When D. ditremum is attached to the host gut an adhesive layer of secreted substance exists between the inner bothrium surface and the host intestinal villi. In D. dendriticum, however, no secreted layer exists between the inner bothrium surface and the host intestinal villi and the inner bothrium surface of this species appears to be lobed or lappet formed. The lobes are protrusions of the distal cytoplasm and are covered with long and slender microtriches. Large conglomerations of secretion globules appearing to be enclosed by a double membrane, are observed in the scolices of D. dendriticum and D. ditremum, although more frequent in the latter. Differences existing between the distal cytoplasm of the scolex and the gravid proglottid are described. The papillae around the genital atrium in mature and gravid segments were studied. Each papilla appears as a thickening of the distal cytoplasm, which in this region is 10-12 mum thick, when studied with transmission electron microscope. From the area between the papillae sensory endings appearing in sections to be either single, double or triple are described.