Electron microscopic study of spermatogenesis in the lung fluke (Paragonimus miyazakii)

Spermiogenesis and spermatozoon ultrastructure in basal polyopisthocotylean monogeneans, Hexabothriidae and Chimaericolidae, and their significance for the phylogeny of the Monogenea

Sperm ultrastructure provides morphological characters useful for understanding phylogeny; no study was available for two basal branches of the Polyopisthocotylea, the Chimaericolidea and Diclybothriidea. We describe here spermiogenesis and sperm in Chimaericola leptogaster (Chimaericolidae) and Rajonchocotyle emarginata (Hexabothriidae), and sperm in Callorhynchocotyle callorhynchi (Hexabothriidae). Spermiogenesis in C. leptogaster and R. emarginata shows the usual pattern of most Polyopisthocotylea with typical zones of differentiation and proximo-distal fusion of the flagella. In all three species, the structure of the spermatozoon is biflagellate, with two incorporated trepaxonematan 9 + "1" axonemes and a posterior nucleus. However, unexpected structures were also seen. An alleged synapomorphy of the Polyopisthocotylea is the presence of a continuous row of longitudinal microtubules in the nuclear region. The sperm of C. leptogaster has a posterior part with a single axoneme, and the part with the nucleus is devoid of the continuous row of microtubules. The spermatozoon of R. emarginata has an anterior region with membrane ornamentation, and posterior lateral microtubules are absent. The spermatozoon of C. callorhynchi has transverse sections with only dorsal and ventral microtubules, and its posterior part shows flat sections containing a single axoneme and the nucleus. These findings have important implications for phylogeny and for the definition of synapomorphies in the Neodermata. We point out a series of discrepancies between actual data and interpretation of character states in the matrix of a phylogeny of the Monogenea. Our main conclusion is that the synapomorphy "lateral microtubules in the principal region of the spermatozoon" does not define the Polyopisthocotylea but is restricted to the Mazocraeidea.

Transition Zone Migration: A Mechanism for Cytoplasmic Ciliogenesis and Postaxonemal Centriole Elongation

The cilium is an elongated and continuous structure that spans two major subcellular domains. The cytoplasmic domain contains a short centriole, which serves to nucleate the main projection of the cilium. This projection, known as the axoneme, remains separated from the cytoplasm by a specialized gatekeeping complex within a ciliary subdomain called the transition zone. In this way, the axoneme is compartmentalized. Intriguingly, however, this general principle of cilium biology is altered in the sperm cells of many animals, which instead contain a cytoplasmic axoneme domain. Here, we discuss the hypothesis that the formation of specialized sperm giant centrioles and cytoplasmic cilia is mediated by the migration of the transition zone from its typical location as part of a structure known as the annulus and examine the intrinsic properties of the transition zone that may facilitate its migratory behavior.

Ultrastructure of spermatogenesis in the testis of Paragonimus heterotremus

Lung fluke, Paragonimus heterotremus, is a flatworm causing pulmonary paragonimiasis in cats, dogs, and humans in Southeast Asia. We examined the ultrastructure of the testis of adult P. heterotremus with special attention to spermatogenesis and spermiogenesis using scanning and transmission electron microscopy. The full sequence of spermatogenesis and spermiogenesis, from the capsular basal lamina to the luminal surface, was demonstrated. The sequence comprises spermatogonia, spermatocytes with obvious nuclear synaptonemal complexes, spermatids, and eventual spermatozoa. Moreover, full steps of spermatid differentiation were shown which consisted of 1) early stage, 2) differentiation stage representing the flagella, intercentriolar body, basal body, striated rootlets, and electron dense nucleus of thread-like lamellar configuration, and 3) growing spermatid flagella. Detailed ultrastructure of 2 different types of spermatozoa was also shown in this study.

Ultrastructural study on spermatogenesis in Ganeo tigrinum, an intestinal trematode of Rana tigrina

Spermatogenesis and the structure of the spermatozoon of the frog intestinal fluke, Ganeo tigrinum has been examined by electron microscopy. Each testis is covered by a tunica consisting of sustentacular cells and fibrous material. Internally the testis is lined by undifferentiated spermatogonial cells, with cytoplasm rich in free ribosomes. The arrangement of the diverse spermatogonic cell populations is similar to those studied in other digeneans. During spermatogenesis the elongation and spiralling of nuclear materials occurs synchronously in the late spermatid stage. The G. tigrinum spermatozoon appears to be biflagellate due to the presence of two filaments. Between the two filaments is an elongated nucleus; these elements fuse to form the monopartite shaft of the sperm. The spermatozoon of G. tigrinum is characterized by the presence of an unusually long nucleus that even surpasses the length of the mitochondrion. At almost half the length of the spermatozoon there is sharp rotation between first axial filament, mitochondrion and the nucleus. Both the axial filaments show 9+1 arrangement of axonemal units throughout the spermatozoon.

Sperm ultrastructure of the digenean Siphoderina elongata (Platyhelminthes, Cryptogonimidae) intestinal parasite of Nemipterus furcosus (Pisces, Teleostei)

The ultrastructure of the spermatozoon of Siphoderina elongata was studied by transmission electron microscopy. A description and drawings of the mature spermatozoon are presented in this paper. Several ultrastructural elements of this male gamete have been observed: a nucleus, two mitochondria, two axonemes of 9 + "1" pattern, external ornamentation of the plasma membrane, spine-like bodies and cortical microtubules. The presence, the location or the number of these elements have been compared with other digenean spermatozoa. Moreover, a close attention was paid to the organization of the external ornamentation region. This zone presents a single row of cortical microtubules disposed in a semi-circle around a mitochondrion and associated with external ornamentation and spine-like bodies. The aim of this study is to highlight criteria which can be interesting in Platyhelminthes phylogeny.

Spermiogenesis and sperm ultrastructure of Carmyerius endopapillatus (Digenea, Gastrothylacidae), a parasite of Bos taurus in Senegal

Ultrastructural study of spermiogenesis and of the spermatozoon of Carmyerius endopapillatus has enabled to describe some characteristics of this digenea. The intercentriolar body situated between the two striated roots and the two centrioles, presents a symmetric organization. Both external bands of this intercentriolar body are made up of a row of granules. During spermiogenesis, a flagellar rotation of 90° is described. The old spermatid does not present external ornamentations. The spermatozoon is characterized, in its anterior region, by the presence of a lateral expansion exhibiting one spinelike body. In C. endopapillatus, external ornamentations are localized only at the level where the lateral expansion appears. The posterior extremity of spermatozoon exhibits a nucleus surrounded by a plasmic membrane lacking microtubules, but presenting a small lateral expansion. This is the first species of Gastrothylacidae family studied by transmission electron microscopy.

Ultrastructural study of the spermatozoon of Pronoprymna ventricosa (Digenea, Baccigerinae), parasite of the twaite shad Alosa fallax Lacepede (Pisces, Teleostei)

In this paper, we describe the ultrastructural organisation of the spermatozoon of a Digenea Baccigerinae Pronoprymna ventricosa. This spermatozoon possesses the elements found in the others digeneans: two axonemes with 9 + "1" pattern, a mitochondrion, a nucleus, cortical microtubules and external ornamentations. However, this spermatozoon presents two particularities. The first is the presence of a single field of cortical microtubules disposed in the ventral side (mitochondrion side) of the spermatozoon. In the other digeneans, two fields of cortical microtubules are observed between the two axonemes. The second is the presence of external ornamentations not associated with cortical microtubules. These two points have, to our knowledge, never been described in another digenean. Moreover, a separation in two groups of the digenean spermatozoa is proposed in relation to the localisation of the external ornamentations. We propose to distinguish a first group exhibiting these elements in the proximal part of the spermatozoon and a second one with external ornamentations in a second part of the gamete.

ULTRASTRUCTURAL STUDY OF SPERMIOGENESIS AND THE SPERMATOZOON OF CREPIDOSTOMUM METOECUS (DIGENEA: ALLOCREADIIDAE), A PARASITE OF SALMO TRUTTA (PISCES: TELEOSTEI)

Spermiogenesis and the spermatozoon of Crepidostomum metoecus, an intestinal parasite of brown trout Salmo trutta, were studied by transmission electron microscopy. Spermiogenesis begins with the formation of a differentiation zone in front of 2 centrioles associated by an intercentriolar body. Each centriole is linked to a striated rootlet, and gives rise to a flagellum. The rotation of flagella is greater than 90 degrees; their fusion with the median cytoplasmic extension is proximodistal and asynchronous. The spermatozoon is formed after constriction of arched membranes. The spermatozoon possesses 2 axonemes of the 9 + "1" pattern, a nucleus, mitochondria, and glycogen. A major feature is the presence, in the anterior part, of external ornamentation and a lateral expansion associated with spinelike bodies. Another attribute is the presence of 2 mitochondria rather than just 1, as in most of the digenean spermatozoa. To our knowledge, this study is the first undertaken with a species of the Allocreadiidae.

Ultrastructure of spermiogenesis and the spermatozoon of Paramphistomum microbothrium [Fischoeder 1901] (Digenea: Paramphistomidae), a parasite of Bos taurus in Senegal

The ultrastructural study of spermiogenesis and the spermatozoon of Paramphistomum microbothrium gave evidence of some characteristics of this digenean. The intercentriolar body located between two striated roots and two centrioles exhibits a symmetric plane. The two external bands of this intercentriolar body are made up of a line of granules. The striated roots are about 3.7 microm long. During spermiogenesis, a flagellar rotation of 90 degrees is described. The spermatozoon is characterized in its anterior part by the existence of external ornamentations and a lateral expansion exhibiting a "spine-like body". Such a spine-like body has never been described before in a digenean. The region II of the spermatozoon is asymmetrical and also characterized by the absence of mitochondrion. The posterior end of this spermatozoon exhibits a nucleus and a few microtubules.

Ultrastructure of spermiogenesis and the spermatozoon of Paramphistomum microbothrium (Fischoeder 1901; Digenea, Paramphistomidae), a parasite of Bos taurus in Senegal

The ultrastructural study of spermiogenesis and the spermatozoon of Paramphistomum microbothrium gave evidence of some characteristics of this digenean. The intercentriolar body located between two striated roots and two centrioles exhibits a symmetric plane. The two external bands of this intercentriolar body are made up of a line of granules. The striated roots are about 3.7-microm long. During spermiogenesis, a flagellar rotation of 90 degrees is described. The spermatozoon is characterized in its anterior part by the existence of external ornamentations and a lateral expansion exhibiting a "spine-like body." Such a spine-like body has never been described before in a digenean. The region II of the spermatozoon is asymmetrical and also characterized by the absence of mitochondrion. The posterior end of this spermatozoon exhibits a nucleus and a few microtubules.

Dicrocoelium hospes Looss, 1907 (Digenea, Dicrocoeliidae): spermiogenesis, mature spermatozoon and ultrastructural comparative study

This work describes the first ultrastructural results on spermiogenesis and on the mature spermatozoon of Dicrocoelium hospes (Trematoda, Digenea) collected in Bos indicus from Senegal (Africa). Examination of this species was processed by TEM. Spermiogenesis follows the general pattern found in the digenean, but reveals a particularity consisting of the appearance of glycogen granules in the late spermatids within the testes. The mature spermatozoon possesses five distinct regions and presents all features found in Digenea gametes: two axonemes, mitochondria, nucleus and parallel cortical microtubules. However, several characters allow us to distinguish D. hospes from other digenetic trematodes within the Dicrocoeliidae family. In fact, we observed several structures that are absent in the other species of Dicrocoeliidae studied until now, such as: a cytoplasmic expansion, extramembranar ornamentation, spine-like bodies and two parallel mitochondria in the mature sperm. Moreover, additional particular characteristics were observed in this species in both extremities of the spermatozoon. This work produced new data on the ultrastructure of this trematode family which may be useful for phylogenetic purposes.

SPERMIOGENESIS AND ULTRASTRUCTURE OF THE SPERMATOZOON OF THE LIVER FLUKE FASCIOLA GIGANTICA COBBOLD, 1856 (DIGENEA: FASCIOLIDAE), A PARASITE OF CATTLE IN SENEGAL

The present paper describes the spermiogenesis and the ultrastructure of the spermatozoon of Fasciola gigantica, as revealed by transmission electron microscopy. Spermiogenesis in F. gigantica begins with the formation of a differentiation zone containing 2 centrioles with associated striated roots and an intercentriolar body between them. Each centriole develops a flagellum. Proximodistal fusion of these flagella with the median cytoplasmic extension gives rise to the spermatozoon. Spermiogenesis in F. gigantica is characterized by the formation of a dorsolateral cytoplasmic expansion, an external ornamentation of the cell membrane, and spinelike bodies. These 3 structures were also observed in the anterior part of the spermatozoon. Our study describes for the first time the simultaneous presence of dorsolateral cytoplasmic expansion, external ornamentation of the plasma membrane, and spinelike bodies in the spermatozoon of a trematode.

Ultrastructural observation of spermatozoa and fertilization in Schistosoma japonicum

The ultrastructure of the sperm and the process of fertilization are described in Schistosoma japonicum. The sperm of S. japonicum has an elongated head and a single tail. The head measures 6.2 x 1.4 microm in average size. No acrosome is present. A mass of mitochondria locates in front of the nucleus. A layer of about 100-120 peripheral microtubules is parallel with the long axis of the head under plasma membrane. The nucleus is dense with some electron-lucent patches. The tail is a single flagellum with unique axoneme, which originates from a centriole. The structure of axoneme includes two types: 9 x 2 + <<l>> in the main part of the flagellum, and 9 x 2 + 0 near the end of the flagellum. The sperm ultrastructure of S. japonicum is similar to that of other schistosomes, apart from the fact that two types of configuration coexisted in the same axoneme, and there is no striated root found in S. japonicum. The sperm differs distinctly from other Digenea. The aberrant ultrastructure of S. japonicum reflects that its evolution is far away from other genera in Digenea. Fertilization occurs at the posterior part of oviduct, in which region the oviduct wall lacks lamellae. Some cortical granules (CG) fuse with plasma membrane, and discharge their content on the surface of the fertilized ovum. The other CGs break down or degenerate in the cytoplasm. By the secondary mature division, the secondary oocyte finally divides to form a female pronucleus. During this period a male pronucleus also forms. The female and male pronucleus approach each other, come into contact in the central region and finally fuse to form a zygote. The function of CGs is discussed.

Spermiogenesis and spermatozoon of Echinostoma caproni (Platyhelminthes, Digenea): transmission and scanning electron microscopy, and tubulin immunocytochemistry

Spermiogenesis and the spermatozoon of Echinostoma caproni (from experimentally infested laboratory mice) were investigated by several methods. Transmission electron microscopy shows that spermiogenesis consists of proximo-distal fusion of three processes followed by elongation of the spermatid. Scanning electron microscopy shows that the spermatozoon is a filiform cell, 235 microns in length, with a cylindrical anterior extremity and a broader posterior extremity. Epifluorescence microscopy, including immunocytochemistry of tubulin and labelling of nucleus with specific dyes, has provided valuable additional information. Migration of the nuclei from the common cytoplasmic mass of spermatids to the distal part of the elongating spermatids is visualized, and centrioles demonstrated in the proximal, anterior region, and the nucleus in the distal, posterior region of the spermatozoon. One axoneme has a distal extremity which in the mature spermatozoon extends 30 microns more distally than the other, with the result that the posterior part of the spermatozoon contains a single axoneme and nucleus. Immunocytochemistry experiments show that a region, 15 microns in length, not labelled by the anti-tubulin antibodies with certain fixation-permeabilization procedures, corresponds to a region which, by transmission electron microscopy, shows external ornamentation on the membrane. This region has a bilaterally asymmetric pattern (in TEM), forms angles or coils according to the fixation used, and marks the boundary between two distinct patterns of movement. Spermiogenesis and the spermatozoon in E. caproni correspond to the general pattern found in the digeneans, with the exception of this asymmetric region. It is emphasized that the use of various methods provides a better understanding of sperm structure than transmission electron microscopy alone, particularly in the case of long, filiform spermatozoa.

[Transmission electron microscopic ultrastructures of the male germinal cells of Fibricola seoulensis]

A transmission electron microscopic study was performed to observe the ultrastructures of the male germinal cells and spermatozoa of Fibricola seoulensis. Spermatogonia were found in the periphery of the testis and characterized by large nuclei and comparatively little cytoplasms. Spermatocytes contained an oval to spherical nucleus. Their nuclear volume was little larger in comparative to that of cytoplasm, and the chromatin was comparatively little. The early spermatids were characterized by a great amount of cytoplasm, and numerous mitochondria encircled the nucleus. In a more advanced spermatids the electron-dense strands of chromatin appeared in the nucleus, and a pair of rootlet of the axoneme and a microtubule-organizing center (MTOC) were observed near the nucleus. The sectioned spermatozoa were found in the testis and the seminal vesicle. Their cross sectional views were divided into 6 types when they were distinguished on the basis of the morphology and components. The spermatozoa of F. seoulensis showed two flagella of 9+1 type axoneme.

Ultrastructure of sperm and spermatogenesis of Rugogaster hydrolagi, Schell 1973 (Platyhelminthes, Trematoda, Aspidogastrea, Rugogastridae)

Mature sperm of Rugogaster hydrolagi exhibit the structure typical of Trematoda, with 2 axonemes of the 9+ "1" pattern being incorporated into the sperm body, dorsal and ventral microtubules occurring in the principal region that contains the nucleus and mitochondrion, and a complete row of peripheral microtubules lying in the proximal region surrounding the two axonemes. During spermiogenesis, a zone of differentiation develops that comprises a row of microtubules along the cell membrane and an adjacent dense region along the nuclear membrane. The intercentriolar body and centrioles appear between the microtubules and the nucleus. Free flagella with striated rootlets grow out in opposite directions, the cell membrane protrudes and lengthens into a median cytoplasmic process (MCP), the nucleus and mitochondrion move into the MCP and the flagella rotate and eventually fuse with the process. A dense region develops in the spermatid shaft some distance from the proximal end, but it is not present in the mature sperm. The spermatid elongates and is eventually pinched off from the residual body at the level of the arching membranes after the rootlets and intercentriolar body have disappeared. Thus, spermatogenesis and sperm in the aspidogastrean Rugogaster hydrolagi correspond to those in digenean Trematoda.

Morphological features of spermatozoa of Paragonimus ohirai (Trematoda: Platyhelminthes) examined by a silver nitrate staining technique

The mature thread-like spermatozoon of Paragonimus ohirai was shown to be composed of 7 distinct segments which have morphologically different characteristics, following staining with silver nitrate. The first segment (1S) is a needle-shaped structure with a perforatorium. The 2S is composed of two filaments loosely paired; 3S consists of a somewhat coarse thread (vestige of the cytoplasmic projection); 4S is composed of two flagella tightly paired; in 5S, two silver-positive filaments are independently seen as in 2S; 6S has a 'spiral' structure composed of two flagella; in 7S, two filaments are seen dissociated from each other. The sperm nucleus exists within the 'spiral' structure of 6S and this structure may serve to hold and/or protect the nucleus. The technique presented here is useful for gross morphological observations of the long sperm of flatworms.

Fasciola hepatica: disruption of spermatogenesis by the microfilament inhibitor cytochalasin B

The distribution of actin filaments in the spermatogenic cells of Fasciola hepatica was determined using a fluorescent derivative of phalloidin. Actin was localised primarily in the region of separation of a secondary spermatogonium from a primary spermatogonium, in the inner faces at the centre of four-cell clusters of tertiary spermatogonia and in the cytophore region of spermatocyte and spermatid rosettes. The effect of the microfilament inhibitor cytochalasin B (100 micrograms/ml) on the ultrastructure of the spermatogenic cells was determined in vitro by transmission electron microscopy using tissue-slice material. Cytochalasin B treatment led to the formation of bi- and multinucleate cells, whose frequency increased with progressively longer incubation periods. Few typical rosettes of spermatocyte and spermatid cells were evident from 6 h onwards, being replaced by syncytial masses of cells. Spermatozoon formation became abnormal in the longer treatment periods, the spermatozoa containing variable numbers of axonemes and an altered distribution of cortical microtubules. Multiple axonemes were observed in the cytoplasm of spermatid cells. The results are discussed in relation to the established role of actin in the cytokinesis phase of cell division and to the effects of cytochalasin B on other tissues and organ systems within the fluke.

Spermatogenesis and the fine structure of the mature spermatozoon of the liver fluke, Fasciola hepatica (Trematoda: Digenea)

Spermatogenesis and the fine structure of the mature spermatozoon of Fasciola hepatica have been studied by transmission electron microscopy. The primary spermatogonia display a typical gonial morphology and occupy the periphery of the testis. They undergo 3 mitotic divisions to give rise to 8 primary spermatocytes forming a rosette of cells connected to a central cytophore. The primary spermatocytes undergo 2 meiotic divisions, resulting in 32 spermatids that develop into spermatozoa. Intranuclear synaptonemal complexes in primary spermatocytes confirm the first meiotic division. The onset of spermiogenesis is marked by the formation of the zone of differentiation which contains 2 basal bodies and a further centriole derivative, the central body. The zone extends away from the spermatid cell to form the median process; into this migrates the differentiated and elongate nucleus. Simultaneously, 2 axonemes develop from the basal bodies. During development, they rotate through 90 degrees to extend parallel to the median process. The migration of the nucleus to the distal end of the median process coincides with the fusion of the axonemes to the latter to form a monopartite spermatozoon. The mature spermatozoon possesses 2 axonemes of the 9 + '1' pattern typical of parasitic platyhelminths, 2 elongate mitochondria and a variable array of peripheral microtubules. The nuclear region of the spermatozoon is immotile. The value of sperm ultrastructure as a taxonomic tool in platyhelminth phylogeny is discussed.

Ultrastructural study on the spermiogenesis and spermatozoon of the metacercariae of Microphallus primas (Digenea), a parasite of Carcinus maenas

The thread-like spermatozoon of the crab parasite Microphallus primas was studied by electron microscopy. A survey of the head region of the spermatozoon reveals three features hitherto unknown in Platyhelminthes spermatozoa. The first is the aberrant inclusion of the nucleus within one of the two axonemes, limited to the head end region. The second is the coexistence, in the same axoneme, of two patterns, 9 + 0 (doublets without dynein arms) and 9 + "1". The third is the presence of a layer of cortical microtubules running longitudinally from the zone where the nucleus goes from axoneme to the tail region (where the two flagella start). The sequence of events in spermatogenesis is similar to that described for most of the Digenea trematodes, and the spermiogenesis process conforms to a common plan in nearly the whole group.

Transmission and scanning electron microscopy of the male reproductive system of Schistosoma margrebowiei Le Roux, 1933

The structure of the male reproductive system of Schistosoma margrebowiei as viewed by light, scanning and transmission electron microscopy is described. The cirrus tube opens at the genital pore without the presence of a cirrus and is spongy and leaf-like. The structure of the germinal and non-germinal cells of the testes are described. The spermatozoon consists of a head, without an acrosome, and a flagellum with a 9 + 0 arrangement of microtubules in the axial filament. A large mass of mitochondria is situated in the anterior end of the head and cortically arranged longitudinally running microtubules are present. The apical region of the epithelial cells of the vas deferens extends into the lumen of the duct forming convoluted lamellae. This arrangement, together with the presence of dense bodies within the cells, suggests that these cells have a secretory function.

Ultrastructure of spermatozoa of the lung fluke, Paragonimus ohirai (Trematoda: Troglotrematidae), in the seminal receptacle

The seminal receptacle of Paragonimus ohirai contains not only mature spermatozoa, but also atypical and degenerate ones, suggesting that abnormal spermatozoa are retained in this organ. The spermatozoon is of a parallel biflagellar type with cortical microtubules, consisting of the anterior region, first mitochondrial region, intermediate (amitochondrial) region, second mitochondrial region, posterior nuclear region (PNR) and tail region (TR). The first third of the spermatozoon exhibits typical undulatory movement, while the middle part shows vibratory movement. At the area between head and midsections (H-M area) the peripheral doublets of axonemes are interrupted, and the external ornamentation is distributed widely around this portion. Throughout the immotile PNR and TR, the axonemes lack the dynein arms of their peripheral doublets. H-M, PNR, and TR ultrastructural characteristics are specific in P. ohirai spermatozoon and seem to be closely related to its pattern of movement.

[Ultrastructure of the integument of adult Paragonimus westermani]

The present study was performed to observe the ultrastructure of the integument of adult Paragonimus westermani. Dogs experimentally infected with 60 metacercariae of P. westermani were autopsied 4 months after the infection. Adult P. westermani were extracted from the dogs and the fine structure was studied by means of scanning and transmission electron microscope. The findings are as follows: Scanning electron microscopic findings showed that the spines and the papillae are distributed at whole body surface but the well developed spines or papaillae are shown around the oral suckrer and ventral sucker. At the end of the body, excretory pore was found, the shape was irregular. Transmission electron microscopic findings showed that plasma membrane, tegument, basal lamina, connective tissue, circular muscle layer, longitudinal muscle layer, nerve axon and tegumental cell were observed. In higher magnification, plasma membrane and bar-shaped granules were found at the outer surface of the tegument.

[A study on the fine structure of Clonorchus sinensis, a liver Fluke V. The mature spermatozoa]

An ultrastructural study on the mature spermatozoa of Clonorchis sinensis was carried out. For this study, the liver flukes were collected from the livers of rabbits and rats artificially infected with the metacercariae obtained from the fresh water fish, Pseudorasbora parva. Six-month old worms were used. The collected liver flukes were washed with 0.85 percent saline solution and then immediately moved to cold 2 percent glutaraldehyde buffered with 0.l M Millonig's phosphate buffer (pH 7.4). The materials were dissected into appropriate pieces in the fixative about 30 minutes after beginning of the fixation. Two hours later the materials containing the seminal receptacle were rinsed several times with the buffer and were secondarily fixed with cold, buffered 1 percent osmium tetroxide for 2 hours. The fully fixed tissue blocks were dehydrated in a series of graded concentrations of acetone and were embedded in Epon 812 mixture. Thin sections obtained from LKB-5 ultramicrotome were stained with uranyl acetate and Reynold's lead citrate. Observations of the sections were carried out with JEM-100CX II electron microscope. In general, the mature sperm was long thread-like form with a sickle-shaped head. According to the longitudinal sectioned view of the sperm tail, the nucleus seemed to be spirally coiled and run a little far along the tail. The acrosome was not observed. The cytoplasm of the tail was biflagellated as usual in trematodes. Unlike other platyhelminth spermatozoa, the sperm tail of Clonorchis sinensis showed the [9+2] pattern in the microtubular arrangement. The mitochondria with poorly developed cristae were observed throughout the middle piece. The middle piece of the tail showed dull ladder or triangular shapes with the two flagella at the bottom. But, the principal piece of the tail was slightly flattened cylindrical shape with two flagella within the cytoplasm. The end piece was uniflagellated. It was not clearly identified whether the end piece was subdivided into two by flagellum or the lengths of the two flagella were different. The glycogen granules were rich in the cytoplasm throughout the length of the spermatozoa. These granules might be the energy source for the movement of the spermatozoa.

[Comparative ultrastructural study of spermiogenesis in Monogenea. 1. Megalocotyle (Monopisthocotylea Capsalidae)]

In Megalocotyle the zones of differentiation (ZD) are short and incomplete; there is no median cytoplasmic process or free flagella. Some peripheral microtubules are present in early ZD, but they disappear. Each nucleus of the common cytoplasmic mass inserts one extremity into a ZD. The mitochondria fuse around this extremity and form a beadlike perforated sphere. Later this sphere slides along the nucleus away from the plasmic membrane like a bead on a string. Each mitochondrial bead (MB), as it moves, trails part of its bulk in the form of a solid streamer; two parallel centrioles follow the MB, each generating a trailing 9 + "1" flagellum. The result is a four-part ensemble extending from each MB to each ZD: the two axonemes, the streamer, and the nucleus, with no membrane separating it from the surrounding cytoplasm. Subsequently a cytoplasmic canal (CC) is formed. The arching membranes, originally located at the base of the ZD, migrate along the four-part ensembles as far as the MB, leaving behind two membranes which define the CC. This formation of the CC is remarkable in that it occurs after migration of the centrioles. At the end of spermiogenesis, the cytoplasmic mass reveals 64 parallel CC each containing an immature spermatozoid whose free rear extremity lengthens out. Each spermatozoid is then detached at its anterior extremity set in the cytoplasmic mass. As in most monopisthocotylean monogeneans, the mature spermatozoid of Megalocotyle lacks peripheral microtubules, although its early ZD has microtubules which subsequently disappear. This feature distinguishes it from trematodes and polyopisthocotylean monogeneans, whose mature spermatozoid keep their ZD microtubules.

Histochemical studies of glycosidase activity in juveniles and adults of the lung fluke Paragonimus

Glycosidase activities in the adults and juveniles of the lung fluke Paragonimus ohirai and P. westermani adults were demonstrated histochemically. For comparative studies, histochemical examination was also made on the adults of the liver fluke Fasciola hepatica. The enzymes examined were N-acetyl-beta-glucosaminidase (EC 3.2.1.30), beta-glucuronidase (EC 3.2.1.31), beta-galactosidase (EC 3.2.1.23), alpha-glucosidase (EC 3.2.1.20) and beta-glucosidase (EC 3.2.1.21). The distribution of beta-glucosaminidase was similar in juveniles and adults. Strong reaction sites for the enzyme were the caecal brush border, tegument, subtegumental cells and tests. In contrast, no staining reaction occurred in the caeca of F. hepatica, although the tegument and parenchymal cells were weakly stained. beta-glucuronidase activity was associated only with the luminal surface of the caeca in the juveniles. However, luminal contents also appeared stained and this might suggest that the activity in the caeca is not endogenous. beta-galactosidase was localized in the caeca, sub-tegmental cells and tegument in both juveniles and adults. No reaction occurred for the other two enzymes, alpha- and beta-glucosidase.

Schistosoma mansoni: the sustentacular cells of the testes

Studies on the multiple compact tests of Schistosoma mansoni have revealed 2 principle cell types: germinal and non-germinal cells. Two morphological forms representing different stages in the cytomorphosis of the sustentacular cells have been considered. The polymorphic sustentacular cells which are conspicuously stained with potassium permanganate contain abundant ribosomal endoplasmic reticulum, glycogen particles and ribosomal masses in comparison with the germinal component of the testes. Golgi complexes with associated secretory bodies and vacuoles are present in the cells. The cytoplasm of the sustentacular cells interdigitate between other cells in the testes. Based on their morphology, nutritive, supportive and phagocytic functions have been attributed to the sustentacular cells. The possible recycling of nutrients by the cells is discussed. It is suggested that the cell regulate the production of spermatozoa from a nutritive viewpoint and also that the translocation of nutrients from the parenchyma to the testes is facilitated by these cells whose cytoplasm extends directly adjacent to the basal lamina.

A Morphological Study On Spermatogenesis In The Liver Fluke, Clonorchis Sinensis

Spermatogenesis in liver flukes, C. sinensis, was investigated by using light and electron microscopes. The epithelium of the testis was composed of a basement membrane, numerous lamellae protuded from the membrance and large number of spermatogonia supported by the lamellae. The lumen of the testis was filled with numerous 8, 16 and 32-cell groups representing primary spermatocytes, secondary spermatocytes and spermatids respectively. None of cell groups with over 32 or under 8 cells was noticed. The process of spermatogenesis is presumably as follows; A cell group of 8 spermatogonia, attached together by a cytophore, is separated from the testis epithelium during the growth period, thus becoming primary spermatocytes. The primary spermatocytes divide to form a cell group of 16 secondary spermatocytes giving rise to a cell group of 32 spermatids through meiotic germ cell division. The spermatids begin to undergo a spermiogenesis. The newly formed sperms remain attached together in the lumen for a while before migrating through the vasa efferentia.

[Electron microscope study of spermatogenesis in two cestodes acanthobothrium filicolle benedenii Loennberg, 1889 and Onchobothrium uncinatum (Rud., 1819) (Tetraphyllidea, Onchobothriidae) (author's transl)]

The spermatogenesis, spermatozoon differentiation and fine structure of Acanthobothrium filicolle benedenii Loennberg, 1889 and Onchobothrium uncinatum (Rud., 1819) were studied by means of light and electron microscopy. Spermatogenesis in both species is of the rosette type. During sperm differentiation, the five following stages have been distinguished: (1) formation of arching membranes and differentiation zone; (2) nuclear elongation; (3) formation of two flagella with a median cytoplasmic process; (4) flagellar rotation; (5) fusion of two flagella with the median cytoplasmic process induced by the migration of nucleus into the latter. The mature spermatozoa of both species are threadlike structures about 250 mum long. They consist of two axonemes of the platyhelminth type (9+1 pattern), elongated nucleus and cortical microtubules embedded in a cytoplasmic matrix containing numerus beta-glycogen particles. The body which appears on cross-sections as crest, lateral with respect to the axoneme, is present in both species. Such a body is reported for the first time in Cestode spermatozoa. There is no mitochondrion in the two Onchobothriidae sperms studied.