Zdzisław Świderski

MESOCESTOIDES LINEATUS (GOEZE, 1782) (MESOCESTOIDIDAE): NEW DATA ON SPERM ULTRASTRUCTURE

Spermiogenesis and the ultrastructural characters of the spermatozoon of Mesocestoides lineatus are described by means of transmission electron microscopy, including cytochemical analysis for glycogen. Materials were obtained from a golden hamster (Mesocricetus auratus) after experimental infection with tetrathyridia metacestodes obtained from naturally infected lizards (Anolis carolinensis) from Louisiana. Spermiogenesis in M. lineatus is characterized by the orthogonal growth of a free flagellum, a flagellar rotation, and a proximodistal fusion. The zone of differentiation contains 2 centrioles associated with striated rootlets and a reduced intercentriolar body. The mature spermatozoon of M. lineatus lacks a mitochondrion, and it is characterized by the presence of (1) a single, spiraled, crested body 150 nm thick; (2) a single axoneme of the 9+‘1’ pattern of trepaxonematan Platyhelminthes; (3) a parallel and reduced row of submembranous cortical microtubules; (4) a spiraled cordon of glycogen granules; and (5) a spiraled nucleus encircling the axoneme.

Ultrastructure of spermiogenesis in the caryophyllidean cestode Wenyonia virilis Woodland, 1923, with re-assessment of flagellar rotation in Glaridacris catostomi Cooper, 1920

The ultrastructure of spermiogenesis in Wenyonia virilis Woodland, 1923, a caryophyllaeid cestode from the silurid Nile fish Synodontis schall (Bloch et Schneider, 1801), is described by means of transmission electron microscopy (TEM) for the first time. Spermiogenesis follows the characteristic caryophyllidean type and is initiated by the formation of a differentiation zone. This area, delimited at its base by a ring of arching membranes and bordered by cortical microtubules, contains two centrioles associated with typical striated rootlets with a reduced intercentriolar body between them. The apical area of the differentiation zone exhibits electron-dense material that is present only during the early stages of spermiogenesis. Only one of the centrioles develops into a free flagellum that grows at an angle of >90° in relation to the cytoplasmic extension. Spermiogenesis is also characterized by a flagellar rotation and a proximodistal fusion of the flagellum with the cytoplasmic extension. The most interesting features observed in W virilis are the presence of a reduced, very narrow intercentriolar body and the unique type of flagellar rotation >90°. Results are compared with those described in two caryophyllideans, Glaridacris catostomi Cooper, 1920 and Khawia armeniaca (Cholodkovski, 1915). Contrary to the original report of Świderski and Mackiewicz (2002), that flagellar rotation has never been observed in spermiogenesis of G. catostomi, re-assessment of their description and illustrations leads us to conclude that flagellar rotation must logically occur in that species. The value of various morphological features of sperm in phylogenetic inference is discussed.

Vitellocyte ultrastructure in the cestode Didymobothrium rudolphii [Monticelli, 1890]: possible evidence for the recognition of divergent taxa within the Spathebothriidea

In the spathebothriidean tapeworm Didymobothrium rudolphii (Monticelli, 1890) the fine structure of the vitellocytes at different stages of their development within the vitelline follicles, vitelline ducts and uterus was studied for the first time using transmission electron microscopy. The vitellocyte inclusions of D. rudolphii are shell globule clusters containing tightly packed shell globules associated with a matrix of moderate electron density, glycogen granules, large electron-lucent lipid droplets (up to 3 μm in diameter), and, occasionally, a lipid droplet may occur in the nucleus of the vitellocytes. The diameter of the clusters ranges from 0.4 to 2.5 μm, the number of shell globules in the clusters varies from 8 to 45, and the size of the globules ranges from 0.12 to 0.25 μm and they are of approximately homogeneous sizes within a cluster. Most vitellocyte lipid droplets have a heterogeneous configuration with a ‘cavity’ inside them when they are within vitelline ducts and intrauterine eggs. Vitellocytes of the eggs contain dark concentric bodies and lipid droplets. The interstitial tissue has a syncytial structure. The morphological parameters of the diameter and shape of shell globule clusters, arrangement of shell globules in clusters, number and diameter of globules within clusters, types of lipid droplets and presence of dark concentric bodies are compared with those of two other spathebothriidean genera, Cyathocephalus and Diplocotyle. The comparative data demonstrate that vitelline material morphology has unique features in three spathenothriidean genera and may be used as evidence for the recognition of separate taxa.

Ultrastructure of the spermatozoon of Dollfusiella spinulifera (Beveridge and Jones, 2000) Beveridge, Neifar and Euzet, 2004 (Trypanorhyncha, Eutetrarhynchidae)

The ultrastructural organization of the mature spermatozoon of the trypanorhynch cestode Dollfusiella spinulifera is described. The spermatozoon is a long filiform cell, tapered at both ends, which lacks mitochondria. Its cytoplasm contains (1) two axonemes of different lengths of the 9+‘1’ pattern of trepaxonematan Platyhelminthes, (2) two rows of parallel cortical microtubules, each of which is adjacent to the opposite sides of the plasma membrane, (3) the nucleus, and (4) glycogen in the form of both α-glycogen rosettes and β-glycogen particles. Unlike the majority of cestode spermatozoa, the spematozoon of D. spinulifera lacks crested bodies and periaxonemal sheath. In view of the present results, the postulated synapomorphic value of crested bodies for the Eucestoda is questioned.

Ultrastructure and cytochemistry of vitellogenesis in Wenyonia virilis Woodland, 1923 (Cestoda, Caryophyllidea).

Vitellogenesis in Wenyonia virilis was examined by transmission electron microscopy (TEM), including the cytochemical detection of glycogen at the ultrastructural level with the periodic acid-thiosemicarbazide-silver proteinate (PA-TSC-SP) technique. Mature vitelline follicles have cells in various stages of development, progressing from immature cells of gonial type near the periphery of the follicle to maturing and mature vitellocytes towards the centre. Maturation is characterized by: (1) increase in cell volume; (2) increase in nuclear surface area restoring the N/C (nucleo-cytoplasmic) ratio; (3) nucleolar transformation; (4) extensive development of parallel cisternae of GER, the shell-protein producing units; (5) development of Golgi complexes, engaged in shell-granule/shell-globule formation and packaging; (6) synthesis and storage of glycogen in the cytoplasm; (7) simultaneous, independent formation and storage of intranuclear glycogen; (8) continuous fusion of small shell-granules into larger shell-globules and fusion of these into large shell-globule clusters with a progressive increase in the number and size of the latter; and (9) disintegration of GER in the medial layer of vitellocyte cytoplasm, degenerative changes and accumulation of glycogen and shell-globule clusters within the cytoplasm. The functional significance of numerous shell-globule clusters and the relatively small amount of nuclear and cytoplasmic glycogen is analysed. Unlike vitellogenesis of other caryophyllids, the nuclear glycogen of mature vitellocytes in W. virilis is randomly dispersed in the nucleoplasm and never forms a high central accumulation, the so-called “nuclear vacuole”. The nutritive function of vitellocytes appears greatly reduced in W. virilis, a fact perhaps related to the intrauterine development of the early embryos. The ultrastructure of vitellogenesis in W. virilis is compared with that in other lower cestodes, both monozoic and polyzoic. Conclusions concerning interrelationships of the vitellogenesis pattern of the ultrastructural cytochemistry of mature vitellocytes of W. virilis to intrauterine embryonation, absence of uterine glands and an extensive uterus characteristic for this species, are drawn and discussed.

ULTRASTRUCTURE OF THE SPERMATOZOON OF PARACHRISTIANELLA TRYGONIS DOLLFUS, 1946 (TRYPANORHYNCHA: EUTETRARHYNCHIDAE)

The ultrastructural organization of the mature spermatozoon of the trypanorhynch cestode Parachristianella trygonis is described by transmission electron microscopy. The spermatozoon is a long and filiform cell, tapered at both ends, lacking both mitochondrion and crested bodies. Its cytoplasm contains 2 axonemes of the 9+‘1’ pattern of the Trepaxonemata longitudinally displaced, parallel cortical microtubules, the nucleus and glycogen in form of both α-glycogen rosettes and β-glycogen particles. The anterior extremity of the spermatozoon is characterized by the presence of an arclike row of up to 10 parallel cortical microtubules that partially surround the first axoneme. The present study emphasizes the ultrastructural similarity between mature spermatozoa of all 4 trypanorhynchs that have been studied to date. Nevertheless, several features, i.e., the characteristics of spermatozoa extremities, the absence of crested bodies, and the possible presence of an arclike layer of cortical microtubules, need a more thorough analysis or confirmation in some of these species.

An ultrastructural study of embryonic envelope formation in the anoplocephalid cestode Mosgovoyia ctenoides (Railliet, 1890) Beveridge, 1978

In this study the ultrastructural aspects of egg envelope formation in the anoplocephalid cestode Mosgovoyia ctenoides are described. In the early stage of oncospheral morphogenesis, formation of three following primary embryonic envelopes takes place: (1) the capsule, (2) the outer envelope, and (3) the inner envelope. The capsule is formed from the vitellocyte material. Two macromeres contribute to the formation of the outer envelope and three mesomeres take part in the formation of the inner envelope. The three primary envelopes undergo further differentiation and transformation into the secondary envelopes, the so-called oncospheral or egg envelopes. In the advanced preoncospheral phase, the inner envelope undergoes differentiation into three sublayers: (1) a thick extra-embryophoral cytoplasmic layer; (2) an electron-dense embryophore, as a stiff pyriform apparatus; and (3) a thin intra-embryophoral cytoplasmic layer containing mesomere nuclei. The oncosphere is located in the extended cupule-like part of the pyriform apparatus. The two embryophoral horns elongate and fuse, thus forming a rigid cone. Four egg envelopes surround the mature infective oncosphere of M. ctenoides: (1) a thick capsule; (2) the outer envelope; (3) the inner envelope with a characteristic embryophore, in the form of the pyriform apparatus; and (4) the oncospheral membrane. The differentiation and ultrastructure of the egg envelopes of M. ctenoides are compared, in particular to those described in other anoplocephalids, and in general to the oncospheres of other cestode species.

CELLULAR ORGANIZATION OF THE ONCOSPHERE OF MOSGOVOYIA CTENOIDES (CESTODA: ANOPLOCEPHALIDAE)

The ultrastructure of the infective oncosphere of the cestode Mosgovoyia ctenoides (Anoplocephalidae) is described. The surface of the infective oncosphere is covered by a thin cytoplasmic layer of tegument connected by a narrow cytoplasmic process with the binucleate subtegumental cell, situated deeper in the body. Below the basal matrix of the cytoplasmic layer of the tegument are situated wide bands of the peripheral, somatic musculature responsible for body movements. The 3 pairs of hooks and their muscles form a complex hook muscle system, responsible for coordinated hook action. Five major types of cells have been distinguished: (1) a binucleate subtegumental cell, (2) a binucleate penetration gland, (3) 2 nerve cells, (4) numerous somatic cells, and (5) about 6 germinative cells. The approximate number of cells is 24 (26 nuclei, including 2 syncytial structures). The results of this study, when compared with other published reports from other cestode taxa, support previous hypotheses that the progressive reduction of oncosphere cells is an adaptive feature in cestode evolution.

Ultrastructural and cytochemical studies on vitellogenesis in trypanorhynch cestode Dollfusiella spinulifera Beveridge, Neifar et Euzet, 2004 (Eutetrarhynchidae)

The first description of vitellogenesis in the Trypanorhyncha is presented in this paper. Though the type of vitellogenesis and mature vitellocyte in Dollfusiella spinulifera appear to be unique among the Eucestoda, to some extent they resemble that observed in the lower cestodes, namely the Tetraphyllidea and Pseudophyllidea. Maturation is characterized by: (1) an increase in cell volume; (2) extensive development of large, parallel, frequently concentric cisternae of GER that produce proteinaceous granules; (3) development of Golgi complexes engaged in packaging this material; (4) continuous enlargement of proteinaceous granules within vesicles and their transformation into shell globule clusters; and (5) progressive fusion of all vesicles, with flocculent material containing the proteinaceous granules and shell globule clusters, into a single very large vesicle that characterises mature vitellocytes of this tapeworm. Cell inclusions in and around the large vesicle consist of flocculent material of a very low density, a few shell globule clusters, moderately dense proteinaceous granules and numerous large droplets of unsaturated lipids. A new previously unreported mode of transformation of proteinaceous granules into shell globule clusters, that evidently differs from that of pseudophyllideans and tetraphyllideans, is described. Cytochemical staining with periodic acid-thiosemicarbazide-silver proteinate for polysaccharides indicates a strongly positive reaction for membrane-bound glycoproteins in all membranous structures such as GER, mitochondria, Golgi complexes, nuclear and cell plasma membranes. Similar staining revealed β-glycogen particles scattered in the cytoplasm of maturing vitellocytes. Typical cytoplasmic β-glycogen particles appear mainly during early vitellocyte maturation but it is characteristic for this species that they are only seldom visible in mature cells. Some working hypotheses concerning the interrelationship between this particular pattern of vitellogensis, possible mode of egg formation in D. spinulifera, its embryonic development and trypanorhynchean life cycle, are drawn and discussed.

Spermatological characteristics of Pleurogenidae (Digenea) inferred from the ultrastructural study of Pleurogenes claviger, Pleurogenoides medians and Prosotocus confusus

The present work constitutes the first ultrastructural analysis of the spermatozoon in the Pleurogenidae, with the study of three species belonging to three of the 16 genera included in this family, namely Pleurogenes claviger, Pleurogenoides medians and Prosotocus confusus. The mature spermatozoa of these pleurogenids present two axonemes of the 9+“1” trepaxonematan pattern, a nucleus, two mitochondria, two bundles of parallel cortical microtubules, external ornamentation, spine-like bodies and granules of glycogen. The organization of these characters in the sperm cell is similar in the three species. Thus, the anterior spermatozoon extremity is filiform and a continuous and submembranous layer of parallel cortical microtubules surrounds the axonemes at their anterior end. The posterior spermatozoon extremity exhibits the second axoneme and corresponds to the Cryptogonimidean type of Quilichini et al. (2010). Slight differences were noted between the spermatozoon of P. confusus and those of the two remaining species in the location of mitochondria.