Spermiogenesis in the proteocephalidean cestode Proteocephalus torulosus (Batsch, 1786) (original) (raw)
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2005
Gallegoides arfaai is similar to that described for other cestode species. Six incomplete synchronic cytokineses occur: four mitotic and two meiotic cell divisions. The primary spermatogonium divides forming two secondary spermatogonia. All further divisions occur simultaneously, resulting in a rosette of four tertiary, then eight quaternary spermatogonia and sixteen primary spermatocytes. The first meiotic division forms thirty-two secondary spermatocytes and after the second meiotic division sixty-four spermatids are formed. Spermiogenesis begins with the formation of a differentiation zone in the form of a conical projection of cytoplasm delimited by a ring of arching membranes. Within this area there are two centrioles, a centriolar adjunct and vestigial striated rootlets. During spermiogenesis, only one of the centrioles develops an axoneme that grows directly into the cytoplasmic extension. The other centriole remains oriented in a cytoplasmic bud and posteriorly aborts. The nucleus elongates and moves into the cytoplasmic extension. Granular material present in each sperm originates from electron-dense material present in the periphery of the spermatid. In the final stage of spermiogenesis two crest-like bodies appear at the base of the spermatid. Finally, the ring of arching membranes constricts and the young spermatozoon detaches from the residual cytoplasm. In order to increase homogeneity in the designation of the non-typical striated rootlets previously described, in this study we propose to group them under the common designation of "vestigial striated rootlets" and its importance is discussed according to previous findings of related structures in other cyclophyllideans.
Parasitology Research, 2005
Spermiogenesis and ultrastructure of the spermatozoon of the pseudophyllidean cestode Triaenophorus nodulosus (Pallas, 1781), a parasite of pike Esox lucius, has been studied by transmission electron microscopy. Spermiogenesis involves firstly the formation of a zone of differentiation with two centrioles associated with striated roots, and an intercentriolar body between them, subsequent growth of the two flagella of unequal length, and a formation of a median cytoplasmic process exhibiting patches of dense material. The nucleus penetrates into spermatid body after flagellar rotation and proximo-distal fusion has started. The mature spermatozoon of T. nodulosus is filiform and contains two axonemes of 9+"1" pattern of the Trepaxonemata, nucleus, cortical microtubules parallel to the spermatozoon axis, and electron-dense granules. The anterior extremity of the gamete contains a single centriole surrounded by numerous electron-dense tubular structures exhibiting spiral arrangement and giving rise to lateral projections, which correspond to the crested body. When the crested body disappears, the spiral pattern of electron-dense tubular structures is changed into a ring, persisting until the centriole of the second axonemes appears. This structure of the crested body of T. nodulosus is unique among the Eucestoda.
Acta Parasitologica, 2008
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 cytoplasmi...
Parasitology Research, 2019
Spermiogenesis in progenetic and adult stages of Archigetes sieboldi Leuckart, 1878, a tapeworm parasitic in oligochaetes and fish respectively, has been examined using transmission electron microscopy and cytochemical staining for glycogen. General pattern of spermiogenesis is essentially like that of other caryophyllideans, i.e., apical dense material in the zone of differentiation in the early stages of spermiogenesis, rotation of free flagellum and a flagellar bud, and proximo-distal fusion. Interestingly, rotation of a free flagellum and flagellar bud to the median cytoplasmic process (MCP) has been observed unconventionally at > 90°only in progenetic stages. Typical striated roots associated with the centrioles occur rarely in A. sieboldi, and only in form of faint structures in advanced stages of spermiogenesis. In contrast to most caryophyllideans studied to date, penetration of the nucleus into the spermatid body has started before the fusion of the free flagellum with the MCP. This feature has been reported rarely but exclusively in the family Caryophyllaeidae. The unipartite mature spermatozoon of A. sieboldi is composed of one axoneme of the 9 + '1' trepaxonematan pattern with its centriole, parallel nucleus, and parallel cortical microtubules which are situated in a moderately electron-dense cytoplasm with glycogen particles. An unusual arrangement of cortical microtubules in the two parallel rows in region I of the spermatozoon is described here for the first time in the Caryophyllidea. Ultrastructural data on spermiogenesis and the spermatozoon in A. sieboldi from tubuficids and carp are compared and discussed with those in other caryophyllideans and/or Neodermata.
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, 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.
Sexual plant reproduction, 1997
The male gamete of Equisetum is the largest and structurally most complex of those so far known in living pteridophytes. The ultrastructure of the mature gametes, is described with particular reference to the influence of the multilayered structure (MLS) on its form. In Equisetum this organ elle comprises a band of over 300 microtubules, underlain along its anterior edge by a lamellar strip, 15-20 pm in length, and forming a sinistral spiral of 2 \ gyres. The tubules extend from the strip, at an angle of about 40°, to form a broad sheath around the twisted pyriform nucleus located in the posterior half of the cell. From the an terior tip of the lamellar strip to the posterior end of the nucleus the gamete completes a helix of 3 | gyres, traversed throughout by the microtubular band. As a result of growth of this band during spermatid metamorphosis, and the 40° angle between the plates of the lamellar strip and the microtubules, the strip is displaced anteriorly and laterally relative to the nucleus. In the mature gamete, although the strip and the nucleus remain interconnected by the microtubular band, only the posterior half of the strip lies directly above the anterior third of the nucleus. The precise interrela tionship between nucleus and MLS is illustrated by reconstructions which display the spermatozoids as they would appear if uncoiled. The 80-120 flagella are inserted outside that part of the microtubular band lying anterior to the nucleus. Their basal bodies retain the proximal cartwheel and stellate transition regions found already in spermatids, but in the mature gametes they are invested with collars of osmiophilic material. The axonemes depart at 10° tangentially from the helix and extend backwards parallel with the tubules of the microtubular band. In consequence of the overlapping gyres of the helix the flagella lie in a spiral groove, similar to that found in cycad spermatozoids. From this groove the plasma membrane closely follows the external surface of the microtubular band. Contrasting with other archegoniates, maximal structural differentiation of the MLS is found in the mature spermatozoid. Flat-bottomed keels are present on the microtubules overlying the lamellar strip in which three distinct strata can be recog nized. The two outer, consisting of alternating plates of electron-opaque and electrontransparent material, are separated by a continuous electron-opaque sheet. The innermost stratum comprises a continuous layer of finely granular material. Overlying the external anterior rim of the microtubular band is an osmiophilic crest. This retains the regularly banded substructure found in spermatids, but in mature spermatozoids is far more prominent than at any other time during spermatogenesis. It contains an electron-transparent lumen and is continuous with both the anterior ends of the microtubules and the anteriormost lamellar plates. Between the inner gyres of the MLS the crest is confluent with extensive sheets of smooth endoplasmic reticulum. Underlying the lamellar strip is a spiral mitochondrion with prominent dilated cristae. The central cytoplasm contains at least 100 pleomorphic mitochondria, to gether with from 15 to 25 amyloplasts and a few microbodies. In the nucleus, in addition to condensed chromatin, are several spherical electron-opaque bodies and aggregations of membrane-bound vesicles. Structures identical in appearance with the former also occur in the cytoplasm, and it is suggested that they may be nuclear in origin, as are similar bodies in animal spermatogenesis. The vesicles may represent portions of redundant nuclear envelope whose extrusion into the cytoplasm was prevented by the ensheathing microtubular band. Pores are still present in the nuclear envelope, where this is not invested by the band. The mature spermatozoids are liberated from antheridia within mucilaginous sacs bounded by fibrillar cell wall material, thought to contain lipid droplets promoting their dispersal when in contact with water. On escaping from the sacs the spermato zoids elongate slightly, and profiles of disrupted flagella are frequently encountered. Occasionally the microtubular band ensheathing the posterior part of the nucleus also becomes disorganized. There is no evidence of the utilization of amyloplast starch as an energy source during motility, and, in contrast to ferns and bryophytes, there is no sequestration of the central cytoplasm by the swimming spermatozoids.
Parasitology Research, 2008
Spermatogenesis and spermiogenesis of the monozoic caryophyllidean cestode Wenyonia virilis (Woodland, 1923), an intestinal parasite of Synodontis schall (Pisces: Siluridae), have been investigated by means of transmission electron microscopy for the first time in Egypt. Spermatogenesis is of a rosette type; each spermatogonium undergoes four mitotic and two meiotic divisions resulting in the formation of sixty four spermatids. These spermatids undergo spermiogenesis and transform into mature spermatozoa. The process of spermiogenesis begins by the formation of the zone of differentiation, at one end of the spermatid cell, with one pair of centriole but without an intercentriolar body. The left-handed centriole, firstly, forms a basal body but aborts forming a flagellar bud. The right-handed one develops externally into an axoneme growing parallel to a cytoplasmic extension protruding from the differentiating zone. The nucleus penetrates this extension followed by the proximodistal fusion of the axoneme in the sperm shaft. The spermatozoon of W. virilis lacks mitochondria and consists of five regions showing gradual increase in the nucleus width and the presence of glycogen granules. Some important differences between the present study and others done on monozoic and polyzoic worms are recorded and discussed.
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.