00653nas a2200169   4500008004100000245022000041210006900261300001000330490000700340100001200347700001900359700001300378700001500391700001800406700001300424856004600437       2015                        eng d00aHigh-pressure freezing and freeze-substitution fixation reveal the ultrastructure of immature and mature spermatozoa of the plant-parasitic nematode <i>Trichodorus similis</i> (Nematoda; Triplonchida; Trichodoridae)0 aHighpressure freezing and freezesubstitution fixation reveal the  a25-310 v771 aLak, B.1 aYushin, V., V.1 aSlos, D.1 aClaeys, M.1 aDecraemer, W.1 aBert, W.  uhttps://nematodes.myspecies.info/node/41102516nas a2200169   4500008004100000020001400041245011700055210006900172260000800241300001400249490000700263520197400270100001902244700001602263700002102279856004602300       2002                        eng d  a0008-430100aUltrastructure of spermatogenesis in the free-living marine nematode Pontonema vulgare (Enoplida, Oncholaimidae)0 aUltrastructure of spermatogenesis in the freeliving marine nemat  cAug  a1371-13820 v803 aSpermatogenesis 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 R vulgare from other nematodes studied.1 aYushin, V., V.1 aCoomans, A.1 aMalakhov, V., V.  uhttps://nematodes.myspecies.info/node/19102483nas a2200181   4500008004100000020001400041245012900055210006900184260000800253300001200261490000700273520190200280100001902182700001602201700001702217700002102234856004602255       2002                        eng d  a0168-817000aUltrastructural study of cuticle formation during embryogenesis of the free-living marine nematode Enoplus demani (Enoplida)0 aUltrastructural study of cuticle formation during embryogenesis   cDec  a189-2030 v423 aCuticle formation during embryogenesis in the free-living marine nematode Enoplus demani (Enoplida) was studied electron microscopically. Cuticle formation begins in the three-fold loop embryo where epidermal microvilli with rounded tips are associated with the filamentous primordial cuticle. This coincides with proliferation of the cisternae of RER, Golgi bodies, multivesicular bodies and numerous transparent vesicles in the epidermal cells. In the four-fold loop embryo the epidermal microvilli are associated with the primordial cuticle, which is represented by a dense filamentous layer of uniform thickness. These microvilli are arranged into regular rows; their apical tips are flattened and filled with dense material. At pretzel I stage the space between epidermal microvilli becomes transparent and the first stratification occurs in the primordial cuticle. At pretzel 2 stage the cuticle is clearly stratified. The transparent space with longitudinally orientated fibres separates the filamentous basal layer from the dense striated cortex. A thin osmiophilic layer (epicuticle) covering the cortex appears. The number of Golgi bodies, cisternae of RER and multivesicular bodies in the epidermal cells peaks at pretzel 3 stage, the cuticle becomes much thicker and its filamentous basal layer is now distinctly stratified. The epidermal microvilli are slightly shorter than at previous stages. At pretzel 4 stage (1-2 days before hatching), the epidermal microvilli disappear at the interchordal regions. The cuticle of newly hatched first stage juveniles includes an external amorphous layer, an osmiophilic epicuticle, a striated cortex, a layer of thick longitudinal fibres and a basal layer consisting from several sublayers of different structure. Cuticle formation in nematodes is discussed in the light of the hypothesis of monophyly of the moulting invertebrates (Ecdysozoa).1 aYushin, V., V.1 aCoomans, A.1 aBorgonie, G.1 aMalakhov, V., V.  uhttps://nematodes.myspecies.info/node/19202238nas a2200169   4500008004100000020001400041245011600055210006900171300001000240490000700250520169200257100001901949700001601968700001701984700002102001856004602022       2002                        eng d  a0869-691800aUltrastructural study of the tadpole stage of the primitive marine nematode Enoplus demani (Enoplia : Enoplida)0 aUltrastructural study of the tadpole stage of the primitive mari  a43-530 v103 aThe ultrastructure of the tadpole (11/2 fold) embryo of the free-living marine nematode Enoplus demani was studied. The cells of the tadpole embryo show no distinct cyto-differentiation. Cytoplasm contains mitochondria and is filled with yolk granules and lipid droplets; nuclei contain clumps of condensed chromatin. The cells at the different stages of the mitotic cycle occur frequently in all the primordial embryonic layers. The centrosomes of the mitotic spindles include centrioles. The cells of the epidermis and the intestine form distinct layers of polarized cells underlain by basal lamina and connected at the apical ends by adherent junctions. The apical membranes of epidermal cells are slightly undulated, occasional cisternae of RER and Golgi bodies occur in the apical cytoplasm. The epidermis of the head-end forms many small funnel-shaped invaginations, interpreted here as the result of morphogenetic cell movement associated with cephalic sensilla formation. There is no distinct lumen in the tadpole intestine, rare microvilli occur squeezed between the apical membranes of intestinal cells. Presumptive muscle cells have no myofilaments, but mitochondria are abundant at the future basal (contractile) part of the cells. The pair of primordial germ cells (PGC) are positioned in the blastocoel latero-ventrally to the mid-part of the intestine. These cells are about twice the diameter of other cells of the embryo. The cytoplasm of PGC does not differ from the cytoplasm of somatic cells of the embryo, and specific P-granules are absent. Data on cell structure of E. demani tadpole embryo are compared with data on cell differentiation in Caenorhabditis elegans.1 aYushin, V., V.1 aCoomans, A.1 aBorgonie, G.1 aMalakhov, V., V.  uhttps://nematodes.myspecies.info/node/19302280nas a2200145   4500008004100000020001400041245013400055210006900189300001200258490000600270520177700276100001902053700001602072856004602088       2000                        eng d  a1388-554500aUltrastructure of sperm development in the free-living marine nematodes of the family Chromadoridae (Chromadorida : Chromadorina)0 aUltrastructure of sperm development in the freeliving marine nem  a285-2960 v23 aSpermatogenesis 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, cistemae 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 Fl 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 Fl 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.1 aYushin, V., V.1 aCoomans, A.  uhttps://nematodes.myspecies.info/node/20802063nas a2200157   4500008004100000020001400041245012200055210006900177260000800246300001200254490000700266520155100273100001901824700001601843856004601859       2005                        eng d  a0001-727200aUltrastructure of sperm development in the free-living marine nematode Metachromadora itoi (Chromadoria, Desmodorida)0 aUltrastructure of sperm development in the freeliving marine nem  cOct  a255-2650 v863 aThe spermatogenesis of the free-living marine nematode Metachromadora itoi was studied with electron microscopy. Spermatocytes and early spermatids have no cytoplasmic components specific for nematodes, i.e. membranous organelles (MO) and fibrous bodies (FB). The late spermatids are subdivided into the residual body and the main cell body with a centrally located nucleus devoid of a nuclear envelope. A pair of 9 x 2 centrioles is associated with the nuclei of spermatids and spermatozoa. The nucleus of the mature spermatid is surrounded by a thick mass of radially arranged FB delimited externally by a discontinuous layer of mitochondria, which underlie a thin ectoplasm. Sperm development is accompanied by transfer of FB matter through the mitochondrion layer into the ectoplasm. The immature spermatozoa from the testis have the centrally located nucleus surrounded by a transparent halo with remnants of FB. The halo is delimited by a sphere of mitochondria that underlie the thick fibrous ectoplasm, a derivative of the FB. In the mature spermatozoa the ectoplasm is transformed into the prominent unpolarized pseudopod. The central nucleus is surrounded by a transparent halo and a sphere of mitochondria, which underlie the pseudopod. MO were not found throughout spermatogenesis. In general, spermatogenesis in M. itoi differs from that observed in many nematodes but resembles in some details the sperm development in some chromadorid and tylenchomorph nematodes. The phylogenetic importance of this sperm development is discussed.1 aYushin, V., V.1 aCoomans, A.  uhttps://nematodes.myspecies.info/node/16202699nas a2200349   4500008004500000020001400045245008500059210006900144300001200213490000700225520169900232653002701931653001501958653002001973653001901993653001602012653002602028653001702054653003102071653001402102653001402116653002202130653002002152653002102172653002102193653001902214653001902233100001902252700001502271700001802286856004502304       2011                        Engldsh    a0869-691800aMature spermatozoa of <i>Brevibucca</i> sp (Nematoda: Rhabditida: Brevibuccidae)0 aMature spermatozoa of iBrevibuccai sp Nematoda Rhabditida Brevib  a131-1380 v193 aMature spermatozoa found in the female gonoduct of the nematode Brevibucca sp. (Brevibuccidae, Rhabditida) were studied with transmission electron microscopy. As in other nematodes, the spermatozoa in Brevibucca sp. represent an aberrant type of male gametes characterised by the absence of an axoneme and an acrosome. Mature spermatozoa of Brevibucca sp. are amoeboid bipolar cells Ca 4-4.5 mu m diam.; each cell is subdivided into a main cell body and a pseudopod devoid of organelles. The main cell body includes a condensed nucleus, many mitochondria and so-called 'membranous organelles' (MO). These unique organelles are characteristic of developing, as well as of mature, spermatozoa of many nematodes. The MO in Brevibucca sp. sperm resemble large (ca 0.5 diam.) vesicles with transparent content and a system of internal finger-like projections of the outer membrane. Each MO is joined to the plasmalemma of the main cell body and is open to the intercellular exterior via a pore. Each spermatozoon has a prominent pseudopod filled with the filamentous components of the cytoskeleton. The structure and development of the rhabditid (order Rhabditida apud De Ley & Blaxter, 2002) sperm is somewhat conserved throughout the order. That is, the general pattern of spermatozoon recognized as "rhabditid" in Brevibucca sp. is similarly expressed in Spiruromorpha, Ascaridomorpha, Panagrolaimomorpha, Tylenchomorpha and Rhabditomorpha. Thus, such conservation lacks phylogenetic pointers at the scale of order. The spermatozoa of the rhabditid pattern observed also in Brevibucca sp. may be considered as an ancestral or symplesiomorphic character for several clades of the order Rhabditida.10acaenorhabditis-elegans10adimorphism10afemale gonoduct10afibrous bodies10afilarioidea10amembranous organelles10amitochondria10aphylogenetic-relationships10aphylogeny10apseudopod10asperm development10aspermatogenesis10asphaerularioidea10asteinernematidae10atylenchomorpha10aultrastructure1 aYushin, V., V.1 aClaeys, M.1 aHouthoofd, W.  uhttps://nematodes.myspecies.info/node/72