Riders on the sperm: sperm dimorphism and spermatozeugmata in nematodes from the genus Steinernema (Rhabditida: Steinernematidae)

Nematology ◽  
2007 ◽  
Vol 9 (1) ◽  
pp. 61-75 ◽  
Author(s):  
Sergei Spiridonov ◽  
Mutsuhiro Yoshida ◽  
Vladimir Yushin
Keyword(s):  
Gap Junctions ◽  
Nuclear Envelope ◽  
Ultrastructural Study ◽  
Entomopathogenic Nematodes ◽  
Size Difference ◽  
Male Gametes ◽  
Motile Cells ◽  
Basic Set ◽  
Sperm Dimorphism ◽  
Mature Spermatozoa

AbstractA comparative ultrastructural study of the male gametes in entomopathogenic nematodes of the genus Steinernema (Rhabditida: Steinernematidae) is based on two species producing monomorphic (S. feltiae) and dimorphic (S. tami) spermatozoa. The spermatozoa of both species are basically the same as in many other Rhabditida. Immature spermatozoa from the testis are unpolarised cells containing a nucleus without a nuclear envelope, mitochondria and membranous organelles (MO), a unique component of the nematode spermatozoa. Mature spermatozoa have a nucleus, mitochondria and emptied MO, each attached to a sperm plasmalemma and opening to the exterior via a pore. Monomorphic mature spermatozoa of S. feltiae are 5 μm in diam., bear pseudopods, and form chains of several cells joined by gap junctions. The dimorphic immature spermatozoa of S. tami form spermatozeugmata where the single giant megaspermatozoon (30-35 μm diam.) bears numerous tiny, 3 μm microspermatozoa, intimately attached to the megaspermatozoon surface by gap junctions. Mature megaspermatozoa from the uterus are motile cells 35-50 μm diam.; they have prominent pseudopods and convey immotile, 2 μm microspermatozoa towards the oviduct. Unlike many other invertebrates, sperm dimorphism in S. tami does not change the basic set and structure of organelles, only their number. The genus Steinernema has two strategies for sperm agglomeration: i) chains of monomorphic spermatozoa of normal size, as in S. feltiae; and ii) spermatozeugmata based on a dramatic size difference between spermatozoa formed in the testis, as exemplified by S. tami. According to the types of sperm agglomeration, the genus Steinernema is divided into two main clades.

An ultrastructural study of the spermatozoid of the fern, Marsilea vestita

1975 ◽  
Vol 17 (3) ◽  
pp. 633-645
Author(s):  
D.G. Myles
Keyword(s):  
Nuclear Envelope ◽  
Ultrastructural Study ◽  
Spiral Structure ◽  
Multilayered Structure ◽  
Condensed Chromatin ◽  
Posterior Region ◽  
Cytoplasmic Vesicle ◽  
Marsilea Vestita ◽  
Shaped Cell ◽  
Dense Band

The ultrastructure of the mature spermatozoid of Marsilea vestita was studied after its release from the microspore and prior to its penetration of the egg. The psermatozoid is a pear-shaped cell with a complex spiral structure coiled around the edge in the narrow anterior end. This coil is composed of a large mitochondrion, elongated nucleus with highly condensed chromatin, a ribbon of microtubules, and a dense band of material (flagellated band) into which the flagella are inserted. There are over a hundred flagella protruding from each spermatozoid along the length of the coil. At the anterior tip of the coil is a short multilayered structure. It is not known what maintains the helical shape of the coil. The microtubular ribbon could be involved, but it is also possible that either the flagellated band, the condensed chromatin, or both, are sufficiently rigid to retain their shpaes unaided. When the spermatozoid is first released from the microspore it includes a cytoplasmic vesicle in the posterior region containing plastids, mitochondria, and other organelles. This vesicle is shed, taking the nuclear envelope with it, before the spermatozoid reaches the egg.

Ultrastructure of somatic mitosis in a diploid strain of the plant pathogenic fungus Cochliobolus sativus

1975 ◽  
Vol 53 (4) ◽  
pp. 403-414 ◽  
Author(s):  
H. C. Huang ◽  
R. D. Tinline ◽  
L. C. Fowke
Keyword(s):  
Nuclear Envelope ◽  
Ultrastructural Study ◽  
Pathogenic Fungus ◽  
Spindle Pole Body ◽  
Spindle Pole ◽  
Cochliobolus Sativus ◽  
Diploid Strain ◽  
Interphase Nuclei ◽  
Pole Body ◽  
Spindle Microtubules

An ultrastructural study of mitosis in a diploid strain of Cochliobolus sativus showed the event to be intranuclear. Two nucleoli occasionally were present in interphase nuclei. During division the spindle pole body peripheral to the nuclear envelope divided; spindle microtubules radiated into the nucleoplasm from the amorphous granular region abutting the nuclear envelope beneath the bodies; chromosomes condensed at prophase, approached the equatorial plane at metaphase, and moved asynchronously at anaphase; single microtubules appeared attached to kinetochore-like structures. At telophase, nuclei exhibited maximal elongation; fissures of the nuclear envelope appeared in the interzonal region; the nucleolus dispersed. The polar nuclear areas became new daughter nuclei with nucleoli.

Sperm development and structure in Bursaphelenchus mucronatus (Nematoda: Aphelenchoidea: Aphelenchoididae)

Nematology ◽  
2011 ◽  
Vol 13 (4) ◽  
pp. 395-407 ◽  
Author(s):  
Vladimir Yushin ◽  
Alexander Ryss
Keyword(s):  
Nuclear Envelope ◽  
Cell Body ◽  
Bipolar Cells ◽  
Unusual Feature ◽  
Phylogenetic Relations ◽  
Bursaphelenchus Mucronatus ◽  
Main Cell ◽  
Sperm Development ◽  
Mature Spermatozoa ◽  
Formation Of Complexes

AbstractSpermatogenesis in Bursaphelenchus mucronatus, described using TEM, is similar to that of the 'rhabditid' nematodes. The development includes formation of complexes of fibrous bodies (FB) and membranous organelles (MO) which appear in spermatocytes; the complexes dissociate in the spermatids; the immature sperm contains separate FB and MO and transformation continues only after activation in the female gonoduct. The spermatheca contains mature spermatozoa as bipolar cells subdivided into one large pseudopod and a main cell body containing a nucleus without a nuclear envelope, numerous mitochondria and peripheral membranous organelles opening to the exterior via pores. Pale reticulate bodies appearing in the B. mucronatus spermatids have no analogies in other nematode spermatogeneous cells. An unusual feature of B. mucronatus spermatozoa is the presence of a very large knob-like projection on each MO marking the pole which joins to the sperm plasmalemma to form a specific pore during in utero spermatozoon activation. The spermatogenesis of B. mucronatus resembles that of Aphelenchoides blastophthorus, although transparent vesicles in spermatids and spermatozoa, filopodia with microtubule-like fibres of immature spermatozoa, eccentric nucleus and multiple pseudopods of the mature spermatozoa distinguish spermatogenesis of the latter from the former. Spermatogenesis includes distinct cytomorphological features that may possibly be used to separate the Bursaphelenchus species and trace their phylogenetic relations.

Etude par cytochimie ultrastructurale des corpuscules périnucléaires présents dans les jeunes oocytes de Ilyanassa obsoleta Say (Mollusca gastéropode)

Development ◽  
1971 ◽  
Vol 25 (3) ◽  
pp. 423-438
Author(s):  
Yves Gerin
Keyword(s):  
Nuclear Envelope ◽  
Variable Thickness ◽  
Ultrastructural Study ◽  
Main Part ◽  
The Other ◽  
Perinuclear Region ◽  
Ilyanassa Obsoleta ◽  
Cytochemical Study ◽  
Ultrathin Sections

An ultrastructural cytochemical study of the perinuclear corpuscles found in young oocytes of Ilyanassa obsoleta Say (molluscan gastropod) Ultrastructural study of the perinuclear region of young oocytes of Ilyanassa obsoleta shows the existence of numerous corpuscles which we have called ‘perinuclear corpuscles’. These are composed of filaments, of variable thickness (15–45 nm) and frequently show contacts with the nuclear envelope. With the development of the oocyte, they scatter in the cytoplasm and then disappear. Treatment of ultrathin sections by pronase or by pepsin provokes the disappearance of the main part of the perinuclear corpuscle. The residual structures of these corpuscles are not digested either by RNase or by DNase. However, if a digestion is carried out with DNase and pronase together, it increases the contrast of the residual structures. On the other hand, the contrast of the perinuclear corpuscles is not altered by specific techniques for polysaccharides. The constitution and the role of the perinuclear corpuscles is discussed.

Cell Junctions in the Hepatopancreas of the Isopod, Armadillidium Vulgare

1976 ◽  
Vol 34 ◽  
pp. 198-199
Author(s):  
Marcia Vega Gonzalez
Keyword(s):  
Gap Junctions ◽  
Morphological Change ◽  
Ultrastructural Study ◽  
Plasma Membranes ◽  
Cell Junctions ◽  
Terrestrial Isopod ◽  
Armadillidium Vulgare ◽  
Junctional Complexes ◽  
Region Plasma ◽  
Cellular Organelles

An ultrastructural study of the hepatopancreas of the terrestrial isopod, Armadillidium vulgare, indicates that morphological change in intercellular membrane apposition parallels functional differention of cells. In the isopod the midgut is structurally and functionally represented by the hepatopancreas. Each of the four lobes of this structure is histologically differentiated into regenerative, transitional and glandular regions, which progress from the distal to the proximal end respectively, and then connect through ducts to the hindgut.The distribution of cellular organelles is similar in all cells of the regenerative region. Plasma membranes of adjacent cells are separated by a distance of 160 A, (fig. 1). There is no indication of specialized membrane apposition such as junctional complexes or gap junctions. The cell membranes do not exhibit infoldings or extensive convolutions.

Ultrastructural observations of spermatogenesis in the fungivorous nematode Paraphelenchus myceliophthorus Goodey, 1958 (Rhabditida: Aphelenchoidea, Aphelenchidae)

Nematology ◽  
2020 ◽  
pp. 1-10
Author(s):  
Vladimir V. Yushin ◽  
Alexander Ryss
Keyword(s):  
Comparative Analysis ◽  
Nuclear Envelope ◽  
Cell Body ◽  
Bipolar Cells ◽  
Main Cell ◽  
Sperm Development ◽  
Mature Spermatozoa ◽  
Formation Of Complexes

Summary Spermatogenesis in Paraphelenchus myceliophthorus is similar to that of the ‘rhabditid’ nematodes. The sperm development includes formation of complexes of fibrous bodies (FB) and membranous organelles (MO), which appear in spermatocytes; the complexes dissociate in the spermatids and the immature sperm contains separate FB and MO. Mature spermatozoa from the uterus are bipolar cells subdivided into anterior pseudopod and posterior main cell body containing a nucleus without a nuclear envelope, numerous mitochondria and peripheral MO opening to the exterior via pores. The mature spermatozoa in the uterus form chains of more than ten flattened cells. Spermatogenesis characters, such as nuclear satellites, presence of FB in immature spermatozoa, small knobbles of MO, specific dense inclusions, absence of filopodia and sperm conjugation, make spermatozoa of P. myceliophthorus morphologically specific for comparative analysis with representatives of Aphelenchoidea and other rhabditids.

scholarly journals Cell Cycle-Dependent Dynamics of the Golgi-Centrosome Association in Motile Cells

Cells ◽  
2020 ◽  
Vol 9 (5) ◽  
pp. 1069 ◽  
Author(s):  
Keyada Frye ◽  
Fioranna Renda ◽  
Maria Fomicheva ◽  
Xiaodong Zhu ◽  
Lisa Gong ◽  
...  
Keyword(s):  
Cell Cycle ◽  
Nuclear Envelope ◽  
Golgi Complex ◽  
Cell Polarization ◽  
Dependent Manner ◽  
Nuclear Envelope Breakdown ◽  
Motile Cells ◽  
A Cell ◽  
Cycle Dependent ◽  
Prevailing View

Here, we characterize spatial distribution of the Golgi complex in human cells. In contrast to the prevailing view that the Golgi compactly surrounds the centrosome throughout interphase, we observe characteristic differences in the morphology of Golgi ribbons and their association with the centrosome during various periods of the cell cycle. The compact Golgi complex is typical in G1; during S-phase, Golgi ribbons lose their association with the centrosome and extend along the nuclear envelope to largely encircle the nucleus in G2. Interestingly, pre-mitotic separation of duplicated centrosomes always occurs after dissociation from the Golgi. Shortly before the nuclear envelope breakdown, scattered Golgi ribbons reassociate with the separated centrosomes restoring two compact Golgi complexes. Transitions between the compact and distributed Golgi morphologies are microtubule-dependent. However, they occur even in the absence of centrosomes, which implies that Golgi reorganization is not driven by the centrosomal microtubule asters. Cells with different Golgi morphology exhibit distinct differences in the directional persistence and velocity of migration. These data suggest that changes in the radial distribution of the Golgi around the nucleus define the extent of cell polarization and regulate cell motility in a cell cycle-dependent manner.

Ultrastructure of spermatogenesis in the free-living marine nematode Anticoma possjetica (Enoplida: Anticomidae)

Nematology ◽  
2003 ◽  
Vol 5 (5) ◽  
pp. 777-788 ◽  
Author(s):  
Vladimir Yushin
Keyword(s):  
Electron Microscopy ◽  
Nuclear Envelope ◽  
The Other ◽  
Residual Body ◽  
Marine Nematode ◽  
Free Living ◽  
Golgi Bodies ◽  
Late Spermatid ◽  
Mature Spermatozoa

Abstract- Spermatogenesis of the free-living marine nematode Anticoma possjetica was studied with electron microscopy. The spermatocyte cytoplasm is filled with numerous ribosomes, mitochondria, cisternae of RER and Golgi bodies. After completion of meiosis the nucleus of the spermatids is surrounded by a newly formed nuclear envelope. The first membranous organelles (MO) appear in the early spermatids, in the late spermatid they, together with mitochondria, surround the nucleus. The ribosomes, RER and Golgi bodies are concentrated inside the residual body. The nuclei of immature spermatozoa assume a bullet-like shape and are surrounded by mitochondria and a mass of MO. The mature spermatozoa possess a small anterior pseudopod anchoring them to the spermatheca wall. The spermatozoon cytoplasm is filled with densely packed MO interspersed with mitochondria. During spermatogenesis of A. possjetica, no organelles resembling the fibrous bodies (FB) found in the spermatozoa of other nematodes were observed. The ultrastructural peculiarities of spermatogenesis in A. possjetica differentiate it from many of the other nematodes studied, although important similarities with other enoplids (reconstitution of nuclear envelope) and other Enoplia (late MO formation) are present.

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