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.

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.

Ultrastructure of spermatogenesis in the free-living marine nematode Halichoanolaimus sonorus (Chromadorida: Selachinematidae)

Nematology ◽  
2004 ◽  
Vol 6 (6) ◽  
pp. 797-809 ◽  
Author(s):  
Vladimir Malakhov ◽  
Julia Zograf ◽  
Vladimir Yushin
Keyword(s):  
Electron Microscopy ◽  
Phylogenetic Analysis ◽  
Cell Body ◽  
Residual Body ◽  
Filamentous Structure ◽  
Marine Nematode ◽  
Free Living ◽  
Golgi Bodies ◽  
Main Cell ◽  
Mature Spermatozoa

AbstractSpermatogenesis of the free-living marine nematode Halichoanolaimus sonorus was studied with electron microscopy. The spermatocyte cytoplasm is filled with ribosomes, mitochondria, cisternae of the RER and Golgi bodies. The spermatids are subdivided into the residual body, which includes the entire synthetic apparatus of the cell, and the main cell body with a centrally located nucleus lacking a nuclear envelope. The mitochondria and the precursors of the fibrous bodies form a layer at the periphery of the main cell body. The main cell body surface bears numerous filopodia. The immature spermatozoa from the testes are unpolarised cells with a centrally located nucleus surrounded by spherical fibrous bodies, mitochondria and membranous stacks; the cell surface is covered by numerous short filopodia. Spermatozoa from the uterus do not show the dramatic changes common for activated spermatozoa of nematodes. Their nuclei, mitochondria, fibrous bodies and surface filopodia remain intact. Bundles of filaments appear between the fibrous bodies. Some of the ultrastructural characters of the spermatogenesis of H. sonorus (late appearance of fibrous bodies and their filamentous structure, absence of membranous organelles at all stages of spermatogenesis, occurrence of numerous surface filopodia in the immature and mature spermatozoa) may be utilised as distinctive cytological characters for phylogenetic analysis of the order Chromadorida.

Spermatozoon ultrastructure in the sphaerularioidid nematode Contortylenchus genitalicola (Tylenchomorpha: Sphaerularioidea)

Nematology ◽  
2006 ◽  
Vol 8 (2) ◽  
pp. 191-196 ◽  
Author(s):  
Hajime Kosaka ◽  
Vladimir Yushin ◽  
Manabu Kusunoki
Keyword(s):  
Bipolar Cells ◽  
Parasitic Nematodes ◽  
Free Living ◽  
Total Absence ◽  
Main Cell ◽  
Transmission Electron ◽  
Parallel Fibres ◽  
Sperm Development ◽  
Spherical Vesicles ◽  
Plant Parasitic

AbstractThe spermatozoa of the insect-parasitic tylenchomorph nematode Contortylenchus genitalicola (Tylenchomorpha: Sphaerularioidea) were studied with the transmission electron microscope. The immature spermatozoa from the testis are unpolarised cells with a centrally located nucleus lacking a nuclear envelope. The cytoplasm contains mitochondria and specific components, membranous organelles (MO) and fibrous bodies (FB). The MO are spherical vesicles with an internal system of finger-like invaginations of the membrane; the cylinder-like FB consist of tightly packed parallel fibres. The mature (activated) spermatozoa from the uterus are bipolar cells with the anterior pseudopod and posterior main cell body (MCB), which includes the nucleus, mitochondria and MO. The MO are attached to the spermatozoon plasmalemma and open to the exterior via pores. FB were not observed but their content may be transformed into the pseudopod cytoskeleton. In general, the spermatozoa of C. genitalicola well resemble those of free-living and parasitic nematodes from a variety of the taxa belonging to the order Rhabditida sensu De Ley & Blaxter (2002). The presence of the MO in C. genitalicola spermatozoa may be considered as an important cytological character that differentiates the superfamilies Sphaerularioidea and Tylenchoidea within the infraorder Tylenchomorpha. The plant-parasitic Tylenchoidea are characterised by a total absence of MO at all stages of sperm development.

Ultrastructure of sperm development in the genus Ditylenchus (Nematoda: Anguinidae)

Nematology ◽  
2015 ◽  
Vol 17 (3) ◽  
pp. 313-324 ◽  
Author(s):  
Dieter Slos ◽  
Pooria Ensafi ◽  
Myriam Claeys ◽  
Vladimir V. Yushin ◽  
Wilfrida Decraemer ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Outer Membrane ◽  
Higher Plants ◽  
Transmission Electron ◽  
Sperm Development ◽  
Ditylenchus Dipsaci ◽  
Mature Spermatozoa ◽  
Formation Of Complexes

Spermatogenesis in Ditylenchus arachis and D. dipsaci was studied using transmission electron microscopy. Spermatogenesis includes the formation of complexes of fibrous bodies (FB) and membranous organelles (MO) in the spermatocytes, which dissociate in separated MO and FB in the spermatids. Immature spermatozoa are unpolarised cells with separate FB and MO. Mature spermatozoa are arranged in chains. Ditylenchus dipsaci is unique in having MO that have already fused with the outer membrane in immature spermatozoa and have mature spermatozoa in the male testis, proving that not only insemination plays a role in spermiogenesis. Contrary to what has been described before, spermatogenesis in Ditylenchus, and other early diverging Tylenchomorpha, follow the typical ‘rhabditid’ pattern, while the absence of MO within Tylenchomorpha appears to be an apomorphic trait for the molecular defined clade of tylenchids that exclusively parasitise higher plants. This confirms the value of traits related to spermatogenesis in nematode phylogeny.

Ultrastructure of sperm development in the free-living marine nematodes of the family Chromadoridae (Chromadorida: Chromadorina)

Nematology ◽  
2000 ◽  
Vol 2 (3) ◽  
pp. 285-296 ◽  
Author(s):  
Vladimir Yushin ◽  
August Coomans
Keyword(s):  
Nuclear Envelope ◽  
Marine Nematodes ◽  
Large Nucleus ◽  
Free Living ◽  
Golgi Bodies ◽  
Microscopie Électronique ◽  
The Family ◽  
Sperm Development ◽  
Sperm Plasma Membrane ◽  
Filamentous Material

AbstractSpermatogenesis in two species of free-living marine nematodes from the family Chromadoridae (Panduripharynx pacifica and Euchromadora robusta) was studied electron-microscopically. The spermatogonia of both species are undifferentiated polygonal cells with a large nucleus surrounded by a small amount of cytoplasm. In P. pacifica the cytoplasm of spermatocytes contains many Golgi bodies, cisternae of RER, ribosomes, mitochondria and dense spherical bodies. Filamentous material is accumulated in spermatids, which contain only mitochondria and a fragmented (or lobed) nucleus devoid of the nuclear envelope. The immature sperm resembles the late spermatid: its central filamentous area is surrounded by chromatine particles and occasional mitochondria. The immature sperm plasma membrane forms deep infoldings. Mature spermatozoa from the uterus consist of a small main cell body (MCB) bearing a prominent pseudopod filled with cytoskeleton filaments. The MCB contains a nucleus and mitochondria. Spermatogenesis in E. robusta (studied only in testes) resembles that described for P. pacifica, but spermatocytes of E. robusta show much lower metabolic activity and, as a result, a smaller mass of filamentous material is stored in the spermatids and immature sperm. The spermatozoa of P. pacifica and the immature sperm of E. robusta have the main ultrastructural features characteristic for nematodes (amoeboid nature, absence of axoneme, acrosome and nuclear envelope). No aberrant organelles special for many nematode sperm (membranous organelles, paracrystalline fibrous bodies and their complexes) were found during sperm development of the chromadorids studied. In this respect their spermatogenesis differs significantly from that in secernents and monhysterids.La spermatogenèse a été étudiée en microscopie électronique à transmission chez deux espèces de nématodes libres marins (Panduripharynx pacifica et Euchromadora robusta) de la famille des Chromadoridae. Les spermatogonies, chez les deux espèces, sont des cellules indifférenciées avec un grand noyau entouré d'une petite quantité de cytoplasme. Chez P. pacifica, le cytoplasme des spermatocytes contient de nombreux corps de Golgi, des cisternae du RER, des ribosomes, des mitochondries et des corps sphériques denses. Le matériel filamenteux est accumulé dans les spermatides qui contiennent seulement des mitochondries et un noyau fragmenté (ou lobé) dépourvu d'enveloppe nucléaire. Le sperme immature resemble aux dernières spermatides: son aire centrale filamenteuse est entourée par des particules de chromatine et quelques mitochondries. La membrane plasmatique du sperme immature forme des invaginations profondes. Les spermatozoïdes matures, dans l'utérus, sont constitués par un petit corps cellulaire principal (MCB) portant un pseudopode proéminent rempli de filaments de cytosquelette. Le MCB contient un noyau et des mitochondries. La spermatogenèse chez E. robusta (étudiées seulement au niveau des testicules) ressemble à celle décrite chez P. pacifica, mais les spermatocytes d' E. robusta sont le siège d'une activité métabolique plus faible et, par conséquent, une masse plus faible de matériel filamenteux est stockée dans les spermatides et dans le sperme immature. Les spermatozoïdes de P. pacifica et le sperme immature d' E. robusta ont les mêmes caractéristiques ultrastructurales pour des nématodes (nature amiboïde, absence d'axonème, d'acrosome et d'enveloppe nucléaire) mais aucune des organelles aberrantes particuliéres à de nombreux spermes de nématodes (organelles membraneuses, corps fibreux paracrystallins et leurs complexes) n'ont été identifiées pendant le développement du sperme chez les Chromadorides étudiés. Par cet aspect, leur spermatogenèse diffère significativement de celle des Secernentes et des Monhysterides.

Ultrastructural Analysis Of The Aseptate Gregarine Pterospora, A Parasite of The Bamboo Worm Axiothella Mucosa.

1999 ◽  
Vol 5 (S2) ◽  
pp. 1274-1275
Author(s):  
Stephen C. Landers
Keyword(s):  
Fine Structure ◽  
Cell Body ◽  
Cytoplasmic Streaming ◽  
The Body ◽  
Ultrastructural Analysis ◽  
State University ◽  
University Campus ◽  
Sodium Cacodylate ◽  
Main Cell

The gregarine Pterospora is a parasite found in the body cavities of bamboo worms (Polychaeta: Maldanidae). The gamont stage of Pterospora has a bizarre structure with a main cell body and multiple posterior cytoplasmic extensions (Fig. 1). The cells are found in pairs within the coelom of the host and move by cytoplasmic streaming as they fill and empty their posterior extensions. Reports of this parasite in the literature are few (see references 1 & 2 for a review) and no ultrastructural details have been published regarding the genus. This study examines the fine structure of the gamont stage with particular emphasis on the structure of the pellicle.The maldanid worm Axiothella mucosa was collected by shovel in St. Andrew Bay, Florida and returned to the Troy State University campus. Pterospora spp. gamonts were pipetted from minced setigers of the worms and fixed in 3% glutaraldehyde buffered with 0.05M sodium cacodylate, pH 7.5, for 1-6 hours.

scholarly journals How a Cell Crawls and the Role of Cortical Myosin II

2009 ◽  
Vol 8 (9) ◽  
pp. 1381-1396 ◽  
Author(s):  
David R. Soll ◽  
Deborah Wessels ◽  
Spencer Kuhl ◽  
Daniel F. Lusche
Keyword(s):  
Cell Body ◽  
Morphometric Analysis ◽  
Myosin Ii ◽  
Four Dimensions ◽  
Main Cell ◽  
Contextual Framework ◽  
A Cell ◽  
Cortical Localization ◽  
Human Polymorphonuclear Leukocytes

ABSTRACT The movements of Dictyostelium discoideum amoebae translocating on a glass surface in the absence of chemoattractant have been reconstructed at 5-second intervals and motion analyzed by employing 3D-DIAS software. A morphometric analysis of pseudopods, the main cell body, and the uropod provides a comprehensive description of the basic motile behavior of a cell in four dimensions (4D), resulting in a list of 18 characteristics. A similar analysis of the myosin II phosphorylation mutant 3XASP reveals a role for the cortical localization of myosin II in the suppression of lateral pseudopods, formation of the uropod, cytoplasmic distribution of cytoplasm in the main cell body, and efficient motility. The results of the morphometric analysis suggest that pseudopods, the main cell body, and the uropod represent three motility compartments that are coordinated for efficient translocation. It provides a contextual framework for interpreting the effects of mutations, inhibitors, and chemoattractants on the basic motile behavior of D. discoideum. The generality of the characteristics of the basic motile behavior of D. discoideum must now be tested by similar 4D analyses of the motility of amoeboid cells of higher eukaryotic cells, in particular human polymorphonuclear leukocytes.

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.

AII amacrine cells quicken time course of rod signals in the cat retina

1982 ◽  
Vol 47 (5) ◽  
pp. 928-947 ◽  
Author(s):  
R. Nelson
Keyword(s):  
Receptive Field ◽  
Cell Body ◽  
Amacrine Cells ◽  
Bipolar Cells ◽  
Spectral Studies ◽  
Inner Plexiform Layer ◽  
Cat Retina ◽  
The Mean ◽  
Aii Amacrine Cells ◽  
Aii Amacrine

1. In a perfused eyecup preparation, AII amacrine cells of the cat retina were penetrated with glass microelectrodes and their electrical responses to photic stimuli recorded. 2. Intracellular injections of the stains Procion, lucifer, or horseradish peroxidase revealed dendritic tree diameters of 30-80 micrometers (48 +/- 16 micrometers, mean +/0 SD) and cell body diameters from 7 to 12 micrometers (9 +/- 3 micrometers) for these cells. The dendrites were broadly stratified throughout the inner plexiform layer (IPL) but possessed large, terminal varicosities in the IPL and inner nuclear lyer (INL) proximal to the cell body. 3. The waveform of these cells in response to photic stimulation suggested division into four components: a) an initial rapid depolarization of the cell membrane followed by a slower decay toward the dark level; b) suppression of the dark noise of the cell; c) with dim or moderately intense stimuli, an off-hyperpolarization; d) in some cases a hyperpolarizing surround response. 4. The receptive fields of AII cells have been characterized using spatial stimuli consisting of long narrow slits. Curves have been fitted to spatial data using two space constants, one for the center mechanism and an opposing one for the surround. For the central mechanism, space constants ranged from 20 to 80 micrometers (46 +/- 22 micrometers), while for the surround they ranged from 60 to 130 micrometers (85 +/- 28 micrometers). The mean half-width of the center mechanism, calculated from the mean space constant, was about 0.25 degrees of visual angle (64 micrometers). The receptive-field properties of AII amacrine cells resemble those of center-depolarizing bipolar cells of other species. 5. Spectral studies of AII amacrine cells reveal that they are rod driven at all criterion voltage levels. Furthermore, adaptation of the rods by rod-saturating backgrounds eliminates 95% of the response amplitude of the AII amacrine cells. Under these conditions the tiny response component remaining is driven by the cat's long wavelength (556-nm peak) cones. 6. AII amacrine cells depolarize to rod stimulation more rapidly than other rod-dominated cells, such as rod bipolar cells, which hyperpolarize. For stimuli corresponding to about 10% of rod saturation, the latency to half-maximum amplitude is about 65 ms for AII cells, 40 ms faster than rod-dominated hyperpolarizing units. The leading edge of the response waveform for AII cells is also much more restricted in time. With the above stimulus it requires about 20 ms to increase from 25 to 75% of its peak, a period almost 4 times shorter than required by rod-dominated S-potential responses. With saturating stimuli the AII response requires only 5 ms to increase from 25 ot 75% of its peak. 7. Although prominent in the rod system, AII amacrine cells do not appear to be able to detect single quantum events. Threshold signals require the bleaching of about 200 rhodopsin molecules within a receptive field containing some 1,300 rods...

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