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 (original) (raw)
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Folia Parasitologica, 2012
the present study describes the ultrastructure of the mature spermatozoon of Lecithocladium excisum (rudolphi, 1819) (Digenea: Hemiuroidea: Hemiuridae) from the stomach of the marine teleost Scomber japonicus Houttuyn (scombridae) captured in the atlantic ocean, off Dakar (senegal). the ultrastructural organization of the spermatozoon of L. excisum follows the general model described in most digeneans. it presents two axonemes of the 9+'1' pattern of the trepaxonemata, nucleus, mitochondrion and parallel cortical microtubules, among other characters. However, some particularities of the spermatozoon of L. excisum are (i) the presence of a membranous ornamentation not associated with cortical microtubules in its anterior extremity, (ii) the presence of a very reduced number of cortical microtubules located only in the ventral side of the spermatozoon and (iii) the absence of several structures described in most digeneans such as spine-like bodies and cytoplasmic expansions.
2004
The ultrastructure of spermiogenesis and the spermatozoon of Poracanthium furcatum (Opecoelidae), parasite of the fish Mullus surmuletus, were studied by electron microscopy. Results were compared with those documented for other digeneans, in particular with Opecoeloides furcatus, another opecoelid. Spermiogenesis follows the general pattern found in the Digenea. Nevertheless, a novel ultrastructural element is described. The posterior part of the centriole is unusual in that it comprises a central element. The mature spermatozoon of P. furcatum presents some characteristics allowing distinction between it and O. furcatus, contrary to the external morphology. It contains a lateral expansion, two mitochondria and a nuclear biflagellar region. Other important ultrastructural features in the spermatozoon include: external ornamentations of the plasma membrane, spine-like bodies, anterior and posterior extremities. All these elements of the male gamete are interesting criteria for phylogenetic studies. Figs 7-12. Successive cross-sections of spermiogenesis of Poracanthium furcatum. 7. Cross-section of the differentiation zone showing the nucleus, the mitochondrion and the start of the striated rootlets. Scale bar = 0.4 µm. 8. Cross-section of the spermatid at the level of the intercentriolar body. Scale bar = 0.4 µm. 9. Cross-section of the differentiation zone at the level of the centriole. Scale bar = 0.4 µm. 10. Crosssection of the spermatid showing the hollow cylinder of the centriole. Scale bar = 0.4 µm. 11. Cross-section of the differentiation zone prior to the proximo-distal fusion. Scale bar = 0.4 µm. 12. Cross-section of the spermatid prior to fusion of the axoneme with the median cytoplasmic process. Note the presence of the fusion line (arrow). Scale bar = 0.4 µm
Tissue and Cell, 2019
The ultrastructure of the spermatozoon of Allopodocotyle tunisiensis (Digenea, Opecoelidae), an intestinal parasite of Solea aegyptiaca (Teleostei, Soleidae), is described by transmission electron microscopy (TEM). The mature spermatozoon is a filiform cell that exhibits two axonemes of different length with the 9+'1' pattern of trepaxonematan Platyhelminthes. In the anterior spermatozoon extremity, cortical microtubules are absent. They appear after the disappearance of an anterior electron-dense material, being initially in a continuous and submembranous layer. They surround only partially the sperm cell. Later, these cortical microtubules are distributed into two bundles. Additionally, the spermatozoon of A. tunisiensis shows two mitochondria, a nucleus, an external ornamentation of the plasma membrane, spine-like bodies, and a large amount of glycogen granules. According to the location of the external ornamentation, A. tunisiensis presents a Quilichini et al.'s type 2 spermatozoon. With respect to the posterior extremity, the sperm cell of A. tunisiensis corresponds to the Quilichini et al.'s opecoelid type. The morphology of the first mitochondrion with a U-shaped posterior extremity is described for the first time in a digenean spermatozoon.
Journal of Parasitology, 2006
Spermiogenesis and ultrastructure of spermatozoon of Nicolla wisniewskii (Digenea, Opecoelidae), an intestinal parasite of Salmo trutta, were studied by electron microscopy. Spermiogenesis follows the general pattern found in the Digenea. It begins with the formation of a differentiation zone, including striated rootlets associated with 2 centrioles and an intercentriolar body. The flagella undergo a rotation of greater than 90Њ. Then, their fusion with the median cytoplasmic process is proximodistal and asynchronous. A peculiarity was observed before the fusion of flagella, i.e., the attachment zones joined as 2 pairs by an electron-dense bridge. The mature spermatozoon is characterized by 2 axonemes, cortical microtubules, a nucleus, 2 mitochondria, external ornamentation, and spinelike bodies. At the posterior end of flagella, the spermatozoon is also characterized by the presence of a central element of the axoneme and without the 9 microtubule doublets. These results were compared with those of the other digeneans and, in particular, with other species of Opecoelidae. It appears that the number of cortical microtubules and their localization in the spermatozoon may be an interesting feature of their phylogeny.
Parasitology Research, 2007
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.
Research Square (Research Square), 2022
The present study provides the rst ultrastructural data on the digenean Gonocerca phycidis belonging to the family Gonocercidae. Live adults digenean were collected from the stomach of the marine sh Gephyroberyx darwinii (Teleostei: Trachichthyidae) caught in the Atlantic Ocean, off Dakar (Senegal). This is also the rst report of G. phycidis from Senegal and this host species. The mature spermatozoon exhibits (i) two axonemes with the 9 + ''1'' pattern of the Trepaxonemata, (ii) a lateral expansion associated with external ornamentations and without cortical microtubules, (iii) two types of external ornamentation of the plasma membrane located in the anterior extremity of the spermatozoon, (iv) two bundles of cortical microtubules in the mitochondrial and nuclear areas of the spermatozoon, (v) one mitochondrion and (vi) a nucleus. The maximum number of cortical microtubules is located in the median part of the spermatozoon. Moreover, the mature spermatozoon of G. phycidis presents some peculiarities. The presence of a lateral expansion without cortical microtubules associated with external ornamentations is described here, for the rst time, in digenean spermatozoa. The presence of two elongated bundles of cortical microtubules is also reported for the rst time in the superfamily of Hemiuroidea. However, the ultrastructure of the posterior spermatozoon extremity con rms that already described in other hemiuroidean species.
Invertebrate Reproduction and Development, 1995
Spermiogenesis in Neopolystoma spratti conforms to the basic pattern found in polyopisthocotylean monogeneans and in Trematoda Digenea and Trematoda Aspidogastrea. The zone of differentiation exhibits a complete ring of cortical microtubules, two initially free flagella with prominent striated rootlets and an intercentriolar body between them. Mitochondria and nucleus migrate into a median cytoplasmic process and flagella rotate and fuse with this process. Mitochondria fuse to form a single elongated mitochondrion and the nucleus moves to a distal location. Mature sperm have two incorporated axonemes for most of their length, a single elongate mitochondrion and a nucleus. Peripheral microtubules form an incomplete ring in the most proximal region and a complete ring in the adjacent region containing two axonemes and the mitochondrion. In the principal region (where the nucleus is present) they form an incomplete ring and are interpreted as originating from the dorsal and ventral faces of the median cytoplasmic process. Thus, although there are more microtubules in the principal region than at either end, the situation is essentially the same as that found in polyopisthocotylean monogeneans, digeneans and aspidogastreans, with no addition of extra lateral microtubules.
Journal of Parasitology, 2004
spermiogenesis and the ultrastructural organisation of the spermatozoon of the trypanorhynch cestode Aporhynchus menezesi Noever, caira, Kuchta et Desjardins, 2010 are described by means of transmission electron microscopy. type i spermiogenesis of A. menezesi starts with the formation of a differentiation zone containing two centrioles separated by an intercentriolar body constituted by five electron-dense plates. Each centriole gives rise to a free flagellum, which grows at an angle of 90° in relation to a median cytoplasmic process. The nucleus and cortical microtubules elongate along the spermatid body. Later, both flagella rotate and fuse with the median cytoplasmic process. At the final stage of spermiogenesis, the young spermatozoon is detached from the residual cytoplasm by a narrowing of the ring of arched membranes. The mature spermatozoon is a long and filiform cell, tapered at both ends, lacking mitochondria. it is characterized by the presence of two axonemes of the 9+'1' trepaxonematan pattern, the absence of crested bodies, the presence of parallel cortical microtubules and nucleus. this pattern corresponds to the type i spermatozoon of the eucestodes. the anterior extremity of the spermatozoon is characterized by the presence of an arc-like row of up to seven parallel cortical microtubules that partially surrounds the first axoneme. These anterior cortical microtubules are thicker than the posterior microtubules and, consequently, the sperm cell of A. menezesi exhibits two types of cortical microtubules. another interesting aspect is the presence of α-glycogen rosettes. This spermatological pattern is similar to that observed in the spathebothriidean and diphyllobothriidean cestodes.
Spermatozoon ultrastructure in two monorchiid digeneans
Spermatological characteristics of species from two monorchiid genera, Opisthomonorchis and Paramonorcheides, have been investigated, for the first time, by means of transmission electron microscopy. The ultrastructural study reveals that the mature spermatozoon of Opisthomonorchis dinema and Paramonorcheides selaris share several characters such as the presence of two axonemes of different lengths showing the 9+''1'' pattern of the Trepaxonemata, a nucleus, two mitochondria, two bundles of parallel cortical microtubules, external ornamentation of the plasma membrane, spine-like bodies, granules of glycogen and similar morphologies of the anterior and posterior extremities. The slight differences between the male gamete of O. dinema and P. selaris are the length of the first axoneme and the position of the second mitochondrion. This study also elucidates the general morphology of the spermatozoon in all monorchiid species described so far, which corresponds to a unique spermatozoon type. Other interesting finds concern the spermatological similarities between monorchiid spermatozoa and the mature spermatozoon reported in the apocreadiid Neoapocreadium chabaudi. These similarities allow us to suggest a close phylogenetical relationship between the Monorchiidae and the Apocreadiidae, although more studies are needed, especially in the unexplored taxa.
We examine for the first time spermatogenesis, spermiogenesis and spermatozoon ultrastructure in Dugesia sicula Lepori, 1948 a sexual and diploid planarian living in Tunisian springs. This TEM-study shows that early spermatids joined by cytophores have rounded nuclei. During spermiogenesis, a row of microtubules appears in the differentiation zone beneath the plasma membrane and close to the intercentriolar body, which consists of several dense bands connected by filaments. Two free flagella (9+1 configuration) grow outside the spermatid. An apical layer of dense nucleoplasm develops and the flagellum appear, facing in opposite directions before rotating to lie parallel to each other after the intercentriolar body splits into two halves. Mitochondria are closely packed around the spermatocyte nucleus before fusing during spermiogenesis, to form a long mitochondrion, which lies parallel to the elongated nucleus along the ripe spermatozoon. The latter is thread-shaped and consists of two regions: the proximal process and a distal part. The former contains the nucleus and a part of the mitochondrion. The latter contains the rest of the mitochondrion and a tapering tail of the nucleus. Separation between these two regions is marked externally by the insertion zone of the two free flagella. The flagella extend posteriorly along the distal part of the spermatozoon. The spermatozoon nucleus consists of a lucent and a dense component coiled in a screw-like pattern around each other. The single row of peripheral microtubules consists of a maximum 40 microtubules in the middle part with an internal layer of three supplementary microtubules.