Ultrastructure of spermatogenesis in the free-living marine nematode Pontonema vulgare (Enoplida, Oncholaimidae)

2002 ◽  
Vol 80 (8) ◽  
pp. 1371-1382 ◽  
Author(s):  
Vladimir V Yushin ◽  
August Coomans ◽  
Vladimir V Malakhov
Keyword(s):  
Electron Microscopy ◽  
Nuclear Envelope ◽  
Residual Body ◽  
Marine Nematode ◽  
Free Living ◽  
Golgi Bodies ◽  
Main Cell ◽  
Paracrystalline Structure ◽  
Peripheral Cytoplasm ◽  
Large Nucleolus

Spermatogenesis in testes of the free-living marine nematode Pontonema vulgare was studied with electron microscopy. The nucleus of spermatocytes has a large nucleolus; the cytoplasm is filled with numerous ribosomes, mitochondria, cisternae of the rough endoplasmic reticulum (RER), Golgi bodies, and flattened osmiophilic cisternae, which are interpreted as the modified membranous organelles (MO) of the spermatozoa of other nematodes studied. After completion of the second meiotic telophase, the nucleus is surrounded by a newly formed nuclear envelope. Further nucleus transformation includes condensation of the chromatin and shrinkage of the nuclear envelope. The deep infoldings of the nuclear envelope give a starlike shape to the nuclei. The cytoplasm of the early spermatids contains the same organelles as in the late spermatocytes, including MO. Many of the latter assume a cuplike or pocketlike shape. During spermatogenesis the peripheral cytoplasm containing the ribosomes, RER, Golgi bodies, and transparent vesicles moves to one pole of the cell forming the residual body. The main cell body of the late spermatid includes the nucleus, mitochondria, and MO embedded in a dense filamentous matrix. The fibrous bodies (FB) of a paracrystalline structure occur in spermatids throughout their developmental transformations. The central part of the spermatozoa contains a starlike nucleus with a nuclear envelope. The filamentous cytoplasm of the spermatozoa includes mitochondria and MO. The spermatozoa extracted from the testes form numerous long filopodia. The dense filamentous cytoplasm of the spermatozoa is continuous with the content of the filipodia. The reconstitution of the nuclear envelope and separate development of MO and FB described in P. vulgare spermatogenesis are the special characters of enoplid nematodes. The reduced character of FB development and simplified structure of MO differentiate P. vulgare from other nematodes studied.

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.

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.

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.

scholarly journals Electron Microscopy of the Ovary of Fasciola Hepatica

1964 ◽  
Vol s3-105 (70) ◽  
pp. 213-218
Author(s):  
R. A. R. GRESSON
Keyword(s):  
Electron Microscopy ◽  
Endoplasmic Reticulum ◽  
Plasma Membrane ◽  
Nuclear Envelope ◽  
Fasciola Hepatica ◽  
Amorphous Material ◽  
Primary Oocyte ◽  
Intercellular Region ◽  
Narrow Bridge ◽  
Peripheral Cytoplasm

The external wall of the ovary of Fasciola hepatica is a membrane-like structure in contact with a non-cellular material in the ovary. An intercellular region containing an amorphous material of moderate electron density is present in the ovary. The primary oocytes are provided with peripheral processes that extend into the intercellular region. The oocytes do not proceed beyond the prophase of the first meiotic division until after they leave the ovary. The nucleolus of the primary oocyte contains vacuole-like areas and emits granular material to the nucleoplasm; some of this material may move to the cytoplasm. Pores are present in the nuclear envelope. In older oocytes narrow bridge-like structures connect the nucleolus and the nuclear envelope. The nuclear envelope of the primary oocyte undergoes replication. It is continuous with the endoplasmic reticulum and the plasma membrane. The location of the mitochondria is correlated with the phases of growth of oogonia and oocytes. The mitochondria possess irregularly arranged cristae. Small, round or oval nutritive bodies are present in the peripheral cytoplasm of older oocytes. It is suggested that areas of relatively high density containing vacuole-like structures represent the Golgi complex.

Perspiria boucheri sp. nov. (Nematoda, Desmodorida) from the East China Sea

Zootaxa ◽  
2019 ◽  
Vol 4695 (2) ◽  
pp. 195-200
Author(s):  
JING SUN ◽  
HONGXIU ZHAI ◽  
YONG HUANG
Keyword(s):  
New Species ◽  
East China Sea ◽  
Buccal Cavity ◽  
Nematode Species ◽  
East China ◽  
Similar Species ◽  
Marine Nematode ◽  
The East China Sea ◽  
Free Living ◽  
China Sea

A new free-living marine nematode species from marine sediments in the East China Sea, is described here as Perspiria boucheri sp. nov. The new species is characterized by amphideal fovea surrounded partially by body annulations; four cephalic setae stout; conical buccal cavity with a minute dorsal tooth and two ventrosublateral teeth; pharynx with a pyriform terminal bulb; tail elongated, conical with 3/4 posterior cylindrical portion which having distinct coarse annulations; spicules strongly curved with narrow ventral velum, handle-shaped proximally; gubernaculum canoe-shaped, without apophysis. The new species differs from the most similar species Perspiria striaticaudata (Timm, 1962) by strongly curved spicules with handle-shaped proximal end, gubernaculum without dorsal apophysis and relatively shorter tail. Updated key to all species of Perspiria is provided. 

scholarly journals Free-Living Marine Nematode Communities in San Jorge Gulf, Argentina

Oceanography ◽  
2018 ◽  
Vol 31 (4) ◽  
pp. 113-121
Author(s):  
Catalina Pastor de Ward ◽  
Virginia Lo Russo ◽  
Martin Varisco
Keyword(s):  
Marine Nematode ◽  
Free Living ◽  
Nematode Communities

scholarly journals Correlation between structure and mass distribution of the nuclear pore complex and of distinct pore complex components.

1990 ◽  
Vol 110 (4) ◽  
pp. 883-894 ◽  
Author(s):  
R Reichelt ◽  
A Holzenburg ◽  
E L Buhle ◽  
M Jarnik ◽  
A Engel ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Nuclear Envelope ◽  
Three Dimensional ◽  
Structural Features ◽  
Nuclear Pore ◽  
Xenopus Laevis Oocyte ◽  
Three Dimensional Model ◽  
Transmission Electron ◽  
Freeze Dried

Nuclear pore complexes (NPCs) prepared from Xenopus laevis oocyte nuclear envelopes were studied in "intact" form (i.e., unexposed to detergent) and after detergent treatment by a combination of conventional transmission electron microscopy (CTEM) and quantitative scanning transmission electron microscopy (STEM). In correlation-averaged CTEM pictures of negatively stained intact NPCs and of distinct NPC components (i.e., "rings," "spoke" complexes, and "plug-spoke" complexes), several fine structural features arranged with octagonal symmetry about a central axis could reproducibly be identified. STEM micrographs of unstained/freeze-dried intact NPCs as well as of their components yielded comparable but less distinct features. Mass determination by STEM revealed the following molecular masses: intact NPC with plug, 124 +/- 11 MD; intact NPC without plug, 112 +/- 11 MD; heavy ring, 32 +/- 5 MD; light ring, 21 +/- 4 MD; plug-spoke complex, 66 +/- 8 MD; and spoke complex, 52 +/- 3 MD. Based on these combined CTEM and STEM data, a three-dimensional model of the NPC exhibiting eightfold centrosymmetry about an axis perpendicular to the plane of the nuclear envelope but asymmetric along this axis is proposed. This structural polarity of the NPC across the nuclear envelope is in accord with its well-documented functional polarity facilitating mediated nucleocytoplasmic exchange of molecules and particles.

The Structure of Sycamore Callus Cells During Division in a Partially Synchronized Suspension Culture

1970 ◽  
Vol 6 (2) ◽  
pp. 299-321
Author(s):  
K. ROBERTS ◽  
D. H. NORTHCOTE
Keyword(s):  
Cell Wall ◽  
Electron Microscope ◽  
Cell Plate ◽  
Optical Microscope ◽  
The Other ◽  
Active Movement ◽  
Developmental Sequence ◽  
Golgi Bodies ◽  
Dividing Cells ◽  
Peripheral Cytoplasm

Sycamore suspension callus cells have been partially synchronized to give a culture with a mitotic index of 15%. Living dividing cells of the culture have been examined with Nomarski differential interference optics and a comparable study made on fixed cells with the electron microscope. An organized band of reticulate cytoplasm partially encircles the nucleus at mitosis. The cell divides by the formation of a phragmosome which grows across the large vacuole; this allows the organization of the cytoplasm which forms the cell plate to be examined separately from the more general cytoplasm of the cell. The cell plate grows from one side of the cell to the other and down its length a complete developmental sequence can be seen. The Golgi bodies and the endoplasmic reticulum are probably involved in the formation of material for the construction of the cell plate and young cell wall. Microfibrils are formed within the plate in the more mature regions, while material contained within vesicles is incorporated at the young growing edge. At the edge of the plate microtubules are found and these correspond to the fibrillar appearance of the phragmoplast seen with the optical microscope. In the living cell an active movement of organelles along the peripheral cytoplasm can be seen and with fixed cells viewed with the electron microscope microtubules are often found adjacent to the plasmalemma and lying close to mitochondria, crystal-containing bodies and plastids. The appearance of crystal-containing bodies and plastids containing phytoferritin is described.

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