Ultrastructure of the forebody and foregut tegument and eccrine gland cells of Crepidostomum metoecus (Trematoda: Digenea: Allocreadiidae)

The forebody and foregut of Crepidostomum metoecus Braun, 1900 are invested with a tegument bearing regularly arranged surface tubercles comparable with the aspidogastrean surface structures. The tegument of the ventrolateral lobes and of the prepharynx is penetrated by ducts of eccrine gland cells. The frontal and prepharyngeal gland cells, localised in the parenchyma, discharge electron-dense granules. Their ducts are lined by peripheral microtubules and fixed to the tegument plasmalemma by a septate junction. The functional roles of these glands are discussed.     

Ultrastructural observations on the redia of Echinostoma revolutum (Froelich, 1802)

E. revolutum redia digestive and excretory system ultrastructure, as well as body wall tegument were studied in TEM. The body tegument protrudes in short microvilli and contains uni- and multiciliate sensory endings. The anterior part of the digestive system (pharynx, short oesophagus) is lined with body tegument, the caecum being covered with a flat epithelium with sporadic microvilli. Oesophageal gland cells are filled with minute electron-dense granules. The excretory capillaries joined to large flame cells are composed of spirally wrapped cells, in the cytoplasm of which there are clusters of microtubules. The special features of the digestive system of echinostome rediae, as well as their significance in the antagonistic relationship to the partenitae of other families of trematodes and their pathogenic effect on the intermediate host, are discussed.     

Histochemistry of gland cells of Eurytrema pancreaticum cercariae.

The cercariae of Eurytrema pancreaticum (Janson, 1889) possess four types of gland cells - proper cystogenic, penetration, ventral and dorsal gland cells. The secretion of ventral and dorsal gland cells is released into the tegument. The proper cystogenic gland cells are the largest and their contents serve for the formation of the cyst wall of metacercariae in the second intermediate host. The secretion of proper cystogenic gland cells contains besides neutral mucosubstances also acid mucosubstances with both carboxyl- and sulphogroups digestible with beta-glucuronidase. The secretion of penetration gland cells contains neutral mucosubstances and proteins with tyrosine, tryptophan and SS groups. The ventral gland cells contain mostly acid mucosubstances with sulphogroups, which are digested with beta-glucuronidase, and proteins with tyrosine, tryptophan and SH groups. The rudimentary dorsal gland cells contain a small amount of acid mucosubstances. The whole tegument of cercariae and the two main collecting canals of the excretory system exhibit a high alkaline phosphatase activity. The nerve ring and the main nerve truncs contain proteins with SH groups and hydrophilic lipids and exhibit a cholinesterase activity. The suckers contain a larger amount of glycogen.     

Morphological features of Prosorhynchus crucibulum and P. aculeatus (Digenea: Bucephalidae), intestinal parasites of Conger conger (Pisces: Congridae), elucidated by scanning electron microscopy

The external morphology of two bucephalid digenean parasites of Conger conger (Linnaeus) (Congridae, Anguilliformes) caught northwest of the Iberian Peninsula, Prosorhynchus crucibulum (Rudolphi, 1819) Odhner, 1905 and P. aculeatus Odhner, 1905, were studied using scanning electron microscopy (SEM). SEM techniques elucidated new external morphological details, mainly relating to the tegument and protruding organs, such as, in P. crucibulum, a papilla-like structure associated with the pharynx and, in P. aculeatus, the cirrus. The tegument bears scale-like spines, which in both species are arranged quincuncially. The spines of P. crucibulum are wider than long and cover the major part of the body and rhynchus. However, no spines were found in either the central apical depression of the rhynchus or in the middle of the ventral indentation. Also, spines were rarely seen on the tegument around mouth, around the genital aperture or close to the excretory pore. P. aculeatus has spines of a different shape, as wide as they are long and with a rounded margin. They cover the whole body and almost the entire rhynchus, but none were found in the middle of the rhynchus or on its neck region.     

Histochemistry of the racemose form of Cysticercus cellulosae.

The racemose form of brain cysticercosis arises from an intense proliferation of the bladder wall after the scolex part has degenerated. The proliferating zones are 2-3 times thicker than the remaining parts of the bladder and are characterized by a densely folded tegument and thick subtegumental and parenchymal layers. The tegument and subtegumental cells contain a large amount of acid mucosubstances with sulpho groups and hydrophilic lipids, and exhibit a high activity of alkaline and acid phosphatases. The parenchyma contains a large amount of glycogen. With the gradual aging of the bladder wall and with the first signs of autolysis, the enzymatic activity as well as the amounts of glycogen, neutral and acid mucosubstances, and proteins decrease, and the hydrophobic lipids prevail over the hydrophilic ones. The results obtained are important for the differential diagnostics of cestode larval stages in the human brain.     

Histochemistry and fine structure of the bladder tegument of a larval Multiceps endothoracicus

Certain differences were found in the histochemistry and fine structure of an active bladder tegument of an infective larva of M. endothoracicus and a regressively changing bladder of an aging larva of this species. The bladder tegument of an aging larva contained an accumulation of acid mucosubstances and phospholipids, that of a younger larva neutral mucosubstances, and it reacted less strongly than the former to tyrosine, cystine and tryptophane. Evidence was obtained with the scanning (SEM) and transmission (TEM) microscope for regressive changes in the bladder of an aging larva: its microtriches were more slender, less tightly packed and fibrously interconnected, and there were spherical formations adhering to the microthrix border. Sometimes, the vacuolation of rod-shaped bodies was so much advanced that these bodies looked like vacuoles arising to the surface of the distal cytoplasm. Another sign of bladder regression was the formation of vacuoles in the cytoplasm of subtegumental cells with contents of a granular to crystalline structure.     

Cysticercus bovis: pinocytosis in the Cysticercus tegument

The authors have found that pinocytosis occurs in the tegument of C. bovis from the fourth week after infection. Electron-lucid bladders surrounded by plasma membrane were encountered in the distal cytoplasm. The pinocytosis occurred in form of micropinocytotic bladders only in the bladder tegument but not in the scolex. The bladders appeared first in the superficial part of the distal cytoplasm. During the following periods of development of the larva they were dispersed in the whole distal cytoplasm and were found even in the processes of subtegumental cells and inside these cells near the heterolysosomes.     

Ultrastructure of the male reproductive system of the trematode Brachylaimus aequans

The transmission electron microscopic studies of the trematode Brachylaimus aequans revealed that the seminal vesicle and ejaculatory duct are lined with syncytial epithelium with numerous lamellate processes. The cirrus and genital pore are covered with a spineless tegument, which is almost identical with the body tegument. The testes contain tailed spermatozoa developing during spermiogenesis from biflagellate spermatids whose flagella (9 + 1) fuse with the median cytoplasmic process. The lumina of seminal vesicle, ejaculatory duct and cirrus are filled with spermatozoa.     

Ultrastructure of the ovarian follicles, oviducts and oocytes of Gyrocotyle urna (Neodermata: Gyrocotylidea)

An ultrastructural study of the ovarian follicles and their associated oviducts of the cestode Gyrocotyle urna Grube et Wagener, 1852, a parasite from the spiral valve of the rabbit fish, Chimaera monstrosa L., was undertaken. Each follicle gives rise to follicular oviduct, which opens into one of the five collecting ducts, through which pass mature oocytes. These collecting ducts open into an ovarian receptacle which, in turn, opens via a muscular sphincter (the oocapt) to the main oviduct. The maturation of oocytes surrounded by the syncytial interstitial cells within the ovarian follicles of G. urna follows a pattern similar to that in Eucestoda. The ooplasm of mature oocytes contain lipid droplets (2.0 x 1.8 microm) and cortical granules (0.26 x 0.19 microm). The cytoplasm of primary and secondary oocytes contains centrioles, indicating the presence of the so-called "centriole cycle" during oocyte divisions. A morphological variation between different oviducts was observed. The luminal surface of the follicular and the collecting oviducts is smooth. The zones of the septate junctions are present within the distal portion of the net-like epithelial wall of the collecting ducts close to the ovarian receptacle. The syncytial epithelial lining of the ovarian receptacle, oocapt and main oviduct is covered with lamellae and cilia. Cortical granules secreted from mature oocytes occur freely within the lumen of the main oviduct that functions as a fertilisation canal. A division of the ovary into separated parts with their own collecting ducts as that typical of Gyrocotyle has been observed in neodermates, basal monogenean family Chimaericolidae, and Neoophora (some Proseriata and Fecampiidae). Ultrastructural data thus reveal several unique morphological characteristics of gyrocotylideans, the most basal taxon of tapeworms (Cestoda).     

Ultrastructure of the tail of Echinostoma revolutum cercaria

The ultrastructure of the tail fins and muscles of Echinostoma revolutum cercaria is described. The longitudinal muscles consist of a primitive type of transversely striated muscle fibres with a well-developed sarcoplasmic reticulum in the Z-band. The fins are formed by a longitudinal tegument fold containing the same components as the remaining part of the tail tegument. The difference between the body and tail tegument is discussed.     

滑刃线虫属一新种——西洋参叶线虫

 1990~1991年在吉林左家中国农科院特产研究所试验地的西洋参叶片上发现多角形褐色病斑,由一种滑刃线虫为害引起。其种的鉴别特征为:口针较短(7.5~10.0 μm),唇区基部缢缩,排泄孔的位置位于神经环和贲门之间,尾尖突为星状,雄虫的交合刺具较明显的顶尖和喙突,与滑刃线虫属内的其它种不同。经鉴定为滑刃线虫一新种,定名为西洋参叶线虫Aphelenchoides panaxofolia.     

Ultrastructure of the cyst of Hymenolepis diminuta larvae

Electron microscopical studies of the cyst of 1-month-old H. diminuta larvae revealed considerable thickening of the superficial syncytium of tegument and formation of a large number of cavities and canals. The cytoplasm of the tegument is filled with microtubules produced by cytons of parenchymal layer which are analogs of tonofibrils. These peculiarities, together with numerous processes of the external fibrous layer, are regarded as adaptative to the changes of the hydrostatic pressure of the hemocoel of the intermediate host. The superficial syncytium is covered with microvilli and keeps polycellular cytoplasmatic bonds with cytons, which ensures energetic and plastic requirements for the stabilization of the hypertrophied syncytium and its physiological regeneration. Accumulations of fibres identical with those of the connective tissue were found in the cytons of the tegument. The cyst parenchyma consists mostly of cells with widened canals of granular endoplasmic reticulum associated with the microfibrils and production of fibrous filaments. The internal fibrous layer is produced by typical fibroblasts. The tegument of the cercomer is thinner and is considered to be less differentiated.     

A New Root-Knot Nematode, Meloidogyne baetica n. sp. (Nematoda: Heteroderidae), Parasitizing Wild Olive in Southern Spain

ABSTRACT High infection rates of wild olive (Olea europaea sp. sylvestris) feeder roots and soil infestation by a new root-knot nematode were found in sandy soil at Vejer de la Frontera (Cádiz), southern Spain. Morphometric traits and analyses of the nematode esterase electrophoretic pattern as well as of the internal transcribed spacer 1 (ITS1)-5.8S gene and D2-D3 fragment of the 28S gene of rDNA showed that specimens differed clearly from known root-knot nematodes. Studies of host-parasite relationships showed a typical susceptible reaction in naturally infected wild olive plants and in olive planting stocks (cvs. Arbequina and Picual) artificially inoculated with the nematode. However, the nematode did not reproduce in artificially inoculated chickpea, pea, and tomato. Because of the ability of this new nematode to infect wild and cultivated olives only, we suggest the common name, "Mediterranean olive root-knot nematode." The species is herein described and illustrated, and named as Meloidogyne baetica n. sp. The new root-knot nematode can be distinguished from other Meloidogyne spp. by (i) the perineal pattern, which is almost similar to that of M. artiellia, characterized by distinct inner striae forming two distinct longitudinal bands, extending throughout the perineum to just below the vulva; (ii) female excretory pore anterior to the level of stylet knobs, excretory pore distance from anterior end/length of stylet ratio extremely small (0.5 to 0.8); and (iii) second-stage juveniles with elongate-conoid tail. Phylogenetic trees derived from maximum parsimony analyses showed that M. baetica is closely related to M. artiellia, the cereal and legume root-knot nematode.     

Transmission electron microscopy of intra-tegumental sensory receptors in the forebody of Crepidostomum metoecus (Digenea: Allocreadiidae)

In the adult fish trematode Crepidostomum metoecus (Braun, 1900), four types of sensory receptors were observed inside the forebody tegument and one type beneath the tegument basal lamina. Two types of sensory receptors extend through the thickness of tegument and have a free cilium inside a pit (types I and II). Two types (III and IV) are nonciliate and entirely intra-tegumental in location. Type IV receptor with large horizontal and thin vertical rootlets was described earlier in aspidogastreans only. Below the basal lamina, nerve endings in close association with muscle fibres, comparable with those in the Aspidogastrea, were detected.     

Ultrastructure of the secondary osmoregulatory canals in the scolex and neck region of Silurotaenia siluri (Batsch, 1786) (Cestoda: Proteocephalidae)

The secondary osmoregulatory canals in the scolex and neck region of Silurotaenia siluri, a parasite of the catfish Silurus glanis (L.), terminate below the tegument basal plasma membrane. The basal plasma membrane of the osmoregulatory canal syncytium is in tight contact with the tegument basal plasma membrane.     

Multiciliate sensory endings in the redia of Echinostoma revolutum (Trematoda, Echinostomatidae)

In addition to uniciliate sensory endings, three types of multiciliate sensory endings have been demonstrated on the anterior end of Echinostoma revolutum redia using transmission and scanning electron microscopy. This is the first finding of multiciliate sensory endings in the parthenogenetic generation of trematodes. In the first type, 12 cilia are situated in a pit communicating with the tegument surface. In the second and third types, there are two and four short cilia, respectively. They protrude from the nerve bulb above the surface of the tegument. The significance of multiciliate sensory endings in rediae and their similarity to multiciliate sensory endings in miracidia and cercariae is discussed.     

A new root-knot nematode, Meloidogyne silvestris n. sp. (Nematoda: Meloidogynidae), parasitizing European holly in northern Spain

High infection rates of European holly ( Ilex aquifolium ) feeder roots by an unknown root-knot nematode were found in a holly forest at Arévalo de la Sierra (Soria province) in northern Spain. Holly trees infected by the root-knot nematode showed some decline and low growth. Infected feeder roots were distorted and showed numerous root galls of large (8–10 mm) to moderate (2–3 mm) size. Morphometry, esterase and malate dehydrogenase electrophoretic phenotypes and phylogenetic trees of sequences within the ribosomal DNA (rDNA) demonstrated that this nematode species differs clearly from other previously described root-knot nematodes. Studies of host-parasite relationships showed a typical susceptible reaction in naturally infected European holly plants, but did not reproduce on a number of cultivated plants, including tomato, grapevine, princess-tree and olive. The species is described here, illustrated and named as Meloidogyne silvestris n. sp. The new root-knot nematode can be morphologically distinguished from other Meloidogyne spp. by: (i) roundish perineal pattern, dorsal arch low, with fine, sinuous cuticle striae, lateral fields faintly visible; (ii) female excretory pore level with stylet knobs, or just anterior to them, EP/ST ratio about 0·8; (iii) second-stage juveniles with hemizonid located 1 to 2 annuli anterior to excretory pore and short, sub-digitate tail; and (iv) males with lateral fields composed of four incisures, with areolated outer bands. Phylogenetic trees derived from maximum parsimony analysis based on 18S, ITS1-5·8S-ITS2 and D2–D3 of 28S rDNA showed that M. silvestris n. sp. can be differentiated from all described root-knot nematode species, and it is clearly separated from other species with resemblance in morphology, such as M. ardenensis , M. dunensis and M. lusitanica .     

Ultrastructure of the digestive tract of Echinostoma revolutum cercaria

The digestive tract of a fully formed free-swimming cercaria of Echinostoma revolutum (Froelich, 1802) Dietz, 1909 was studied by electron microscopy. The oral sucker and pharynx are covered by a tegument. The oesophagus and the caeca are not luminized. They are packed with giant epithelial cells with electron-dense granules of irregular shape, rough endoplasmic reticulum and its cisterns, and Golgi apparatus. The tegument of the oral sucker cavity contains numerous uniciliate receptors.     

Ultrastructure of the scolex, rhyncheal system and bothridial pits of Otobothrium mugilis (Cestoda: Trypanorhyncha)

The ultrastructure of the scolex tegument, bothridial pits (=ciliated pits) and rhyncheal system of Otobothrium mugilis Hiscock, 1954 is described from plerocerci collected from the teleosts Arius graeffei Kner et Steindachner and Mugil cephalus Linnaeus. Scanning electron microscopy revealed that filamentous microtriches with shortened caps are abundant across the entire surface of the tegument. Palmate microtriches are dominant on the bothridia and their margins. The surfaces of bothridial pits were covered with large bifid microtriches. The bothridial pits are strongly muscularised invaginations of the tegument. Nervous tissues were not observed within the pits and it is probable that these structures function as accessory attachment structures. The wall of each tentacle sheath consists of one to three bands of fibrils, lined internally by a thin cytoplasmic layer. The tentacular walls are cellular, containing myofilaments. The fibrils of the tentacular walls are arranged into discrete blocks of parallel fibrils and appear to be intracellular. Tentacular walls are lined externally by a modified membrane with an external glycocalyx. Tentacular hooks are solid, bound externally by a membrane. The body of the hook contains numerous longitudinal canaliculi and an electron-opaque medulla lies at the centre of the hook.     

Sense organs of the nematodes Trichinella pseudospiralis Garkavi, 1972 and T. nativa Britov et Boev, 1972

The structure and distribution of the sense organs of the head and the tail of two day-old Trichinella species (females) have been determined by transmission (TEM) and scanning (SEM) electron microscopy. In both species occur 16 cephalic sense organs, which contain three modified dendritic processes, in addition to the amphids. The nerve cell bodies are situated in the area above the nerve ring. The amphid contains ten dendritic processes. The sense organs open to the external environment by pores through the cuticle. Above the bulbous tip, the dendritic processes are surrounded by hypodermal cells. They enter posteriorly the pseudocoelom and join in subventral, subdorsal and two sublateral nerves, with transparent nuclei, in the area above the nerve ring. The distribution of the sense organs of larvae from the muscles and from the uterus is similar to that of the adults. The dendritic processes are short, most of their distal chamber is compacted with a dense, filamentous material. The rectum in the tail end of the female is innervated from the dorsal ganglion composed by multipolar cells with numerous dendrites and a single axon. Close to the excretory pore occurs a hemizonid which consists of six to eight dendrites and is situated between the hypodermis and the muscles. This organ has not been found in the larva.