Cheikh Tidiane Bâ

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.

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-μm long. During spermiogenesis, a flagellar rotation of 90° 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.

Spermiogenesis and sperm ultrastructure of Cotylophoron cotylophorum (Trematoda, Digenea, Paramphistomidae), a parasite of Bos taurus in Senegal

Ultrastructure of spermiogenesis and mature spermatozoon of Cotylophoron cotylophorum are described with transmission electron microscopy. The description gives evidence of some characteristics of this digenean. The intercentriolar body situated between two striated roots and two centrioles exhibits a symmetric plane. The external bands of this intercentriolar body are formed of a line 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 part, by the presence of a lateral expansion exhibiting a spinelike body. External ornamentations of the plasmic membrane are only present at the level of the ventral field of cortical microtubules. The posterior end of this spermatozoon exhibits a nucleus surrounded by a plasmic membrane without cortical microtubules, but exhibiting a small lateral expansion.

Ultrastructure of the spermatozoon of Sandonella sandoni (Cestoda, Proteocephalidea, Sandonellinae)

Summary The mature S. sandoni spermatozoon exhibits an apical cone of electron-dense material about 1 μm long and a helicoidal crest-like body 50–100 nm thick. The cortical microtubules, varying in number from 0 to 18 depending on where the section is cut, are of different lengths, spiralized, and in close contact with the plasma membrane in regions III and IV of the spermatozoon where they form one or two fields of 1 to 9 units, which are associated with electron-dense subjacent material and are either laterally delimited or not by submembranous thickenings. The cytoplasm contains amorphous electron-dense material in regions II, III and IV of the gamete. The nucleus is a fine cord coiled in a spiral around the axoneme. This is of the 9+“1” pattern. Its posterior extremity is made up of only the axial element surrounded by nine singlets formed by the A microtubules attached to the plasma membrane. This type of posterior extremity of the flagellum has never been described in a platyhelminth. Similarly, sub...

Spermatological characters of the digenean Rubenstrema exasperatum (Rudolphi, 1819) (Plagiorchioidea, Omphalometridae)

We present the first ultrastructural description of spermiogenesis and of the spermatozoon of Rubenstrema exasperatum (Omphalometridae), an intestinal parasite of Sorex araneus (Soricidae). Spermiogenesis begins with the formation of the differentiation zone delimited at the base by the ring of the arched membranes and bordered by cortical microtubules. This area contains two centrioles associated with striated rootlets and with an intercentriolar body. It also contains the nucleus and numerous mitochondria. The intercentriolar body is made up of seven electron-dense layers. The two centrioles give rise to two free flagella that grow orthogonally to the median cytoplasmic process. Additionally, flagellar rotation is followed by the proximodistal fusion of the flagella with the median cytoplasmic process, while the nucleus and mitochondria migrate along the spermatid. The constriction of the ring of arched membranes gives rise to the young spermatozoon. The mature spermatozoon of R. exasperatum shows several ultrastructural characters found in digenean spermatozoa such as two axonemes, mitochondrion, two bundles of parallel cortical microtubules, nucleus, and granules of glycogen. External ornamentation of the plasma membrane and spinelike bodies are also present in the spermatozoon of this species. In the present study, we produced additional spermatological data concerning a previously unexplored family, and we also compare our data to the existent ultrastructural descriptions within the Digenea in order to assess the use of several characters proposed as phylogenetic tools.

Ultrastructure of spermiogenesis of Dipylidiumcaninum (Cestoda, Cyclophyllidea, Dipylidiidae), an intestinal parasite of Canis familiaris

We describe for the first time the ultrastructure of spermiogenesis of a representative of the family Dipylidiidae, Dipylidium caninum. Spermiogenesis begins with the formation of a differentiation zone. This conical area presents two centrioles with associated striated roots. One of the centrioles develops a flagellum and posteriorly a proximodistal fusion is produced between the axoneme and a median cytoplasmic process. In a final stage of spermiogenesis a condensation of electron-dense material between cortical microtubules is observed in the anterior part of the differentiation zone. This is the origin of the crest-like body that appears at the end of spermiogenesis. The presence of striated roots associated with centrioles constitutes the first report of these structures in the spermiogenesis of a cyclophyllidean cestode.

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.

Ultrastructure of the spermatozoon of Holorchis micracanthum (Digenea: Lepocreadiidae), an intestinal parasite of Plectorhinchus mediterraneus (Pisces, Teleostei) in Senegal

The mature Holorchis micracanthum spermatozoon exhibits an apical cone of electron-dense material forming a lateral extension, extramembranar ornamentations, and two fields of cortical microtubules, delimited by attachment zones. The axonemes, of the 9 + “1” pattern of the Platyhelminthes, are shifted longitudinally, one compared to the other. The nucleus, with a fibrous chromatin and a more or less circular section, granules of electron-dense material, and a moniliform mitochondrion are present. The latter, in longitudinal sections, appears in the form of successive bulges, connected to each other by a fine mitochondrial cord, and extends along almost the whole length of the gamete. To our knowledge, a moniliform mitochondrion has never been described before in a digenean. Likewise, the presence of a lateral extension of an apical cone of electron-dense material has never been previously reported in the Lepocreadioidea. In addition, in this work, we show for the first time the existence of extramembranar ornamentations in a species of the Lepocreadiidae.

Ultrastructure of spermiogenesis and the spermatozoon of Vampirolepis microstoma (Cestoda, Hymenolepididae), intestinal parasite of Rattus rattus

Spermiogenesis in Vampirolepis microstoma begins with the formation of a nuclear cone and a differentiation zone. This is delimited at the front by arched membranes, bordered by cortical microtubules, and contains two parallel centrioles linked together at their bases by electron‐dense, amorphous material. The nuclear cone elongates, becomes filiform, and migrates into the spermatid body. Later, one of the centrioles gives rise to a flagellum that grows at the same pace as the cortical microtubules. Subsequently, 6 crested bodies form and the old spermatid separates from the residual cytoplasm. The mature V. microstoma spermatozoon is filiform and lacks mitochondria. Its anterior end exhibits six crested bodies 100 to 200 nm thick of unequal lengths. The axoneme is of the 9+”1” pattern. The cortical microtubules are spiralized and make an angle of about 20 to 30° to the spermatozoon axis, except at their posterior extremity where they become parallel to this axis. The nucleus is an electron‐dense cord coiled in a spiral around the axoneme. The cytoplasm is slightly dense but contains many electron‐dense granules in regions III, IV, and V of the spermatozoon. The presence of centrioles linked together at their bases by electron‐dense material has never, to our knowledge, been reported in a Platyhelminth. Likewise, a nuclear migration, right from the beginning to the end of spermiogenesis, has never been described in a cestode. In addition, we observe for the first time the existence of six crested bodies in a cestode from a Mammal. Microsc. Res. Tech. 42:218–225, 1998.

Ultrastructural characters of the spermatozoa in Digeneans of the genus Lecithochirium Lühe, 1901 (Digenea, Hemiuridae), parasites of fishes: comparative study of L. microstomum and L. musculus

This study provides the first ultrastructural data of spermatozoa in the genus Lecithochirium. The spermatozoa of L. microstomum (from Trichiurus lepturus in Senegal) and L. musculus (from Anguilla anguilla in Corsica) exhibit the general pattern described in the great majority of the Digenea, namely two axonemes with the 9 + “1” pattern typical of the Trepaxonemata, one mitochondrion, a nucleus, parallel cortical microtubules and external ornamentation of the plasma membrane. Spermatozoa of L. microstomum and L. musculus have some specific features such as the presence of a reduced number of cortical microtubules arranged on only one side of the spermatozoon, the lack of spine-like bodies and expansion of the plasma membrane. The external ornamentation of the plasma membrane entirely covers the anterior extremity of the spermatozoa. The ultrastructure of the posterior extremity of the spermatozoa corresponds to the pattern previously described in the Hemiuridae, characterized by only singlets of the second axoneme. A particularity of these spermatozoa is the organization of the microtubule doublets of the second axoneme around the nucleus in the posterior part of the spermatozoon.