Functional aspects of the intercentriolar body in the spermiogenesis of Nematoplana coelogynoporoides (Plathelminthes,Proseriata)

Summary The intercentriolar body in the biciliary spermatids of Nematoplana coelogynoporoides and its changes during spermiogenesis are described. Different functional aspects of the body, for example its presumed role as microtubule-organising centre and its influence on cell elongation, are discussed.Abbreviations bb basal body - ce cell elongation - ci cilium - icb intercentriolar body - mt microtubules - n nucleus - r ciliary rootlet     

Modified sperm ultrastructure and some data on spermiogenesis in Provortex tubiferus (Plathelminthes,Rhabdocoela): phylogenetic implications for the Dalyellioida

Summary Spermatozoa of Provortex tubiferus are thread-shaped, totally enclosed by peripheral microtubules and devoid of cilia or flagella. A peripheral layer of dense bodies underlies the cortical microtubules. Roundish mitochondria are arranged in a single row in the middle region of the sperm body. A special feature is documented in the appearance of a perinuclear condensation consisting of leaflet-like compartments. Such a perinuclear condensation is not known for any other species of the Plathelminthes. This characteristic may have functional roles in the locomotion and stabilization of the filiform aciliary spermatozoon. During spermiogenesis, two centrioles in a diplosome configuration differentiate near each nucleus of an early spermatid. With proceeding sperm maturation, a structure resembling an intercentriolar body is formed as typical for the taxon Trepaxonemata. However, axonemes are not differentiated and the intercentriolar body becomes disorganized. It is hypothesized that the Provorticinae (with Provortex) and the Graffillinae (with Paravortex) constitute a new monophylum with the autapomorphy special type of aciliary spermatozoon. The Provorticidae and the Graffillidae, respectively, are non-monophyletic groupings; the Kirgisellinae, Pseudograffillinae and Bresslauillinae do not belong to the monophylum Provorticinae + Graffillinae.Abbreviations ccp cone-shaped cell process - cm cortical microtubules - ct centriole - cy cytophore - db dense bodies - mi mitochondrion - n nucleus - pn perinuclear condensation     

Ultrastructural observations of the spermiogenesis in the Parotoplaninae (Plathelminthes,Proseriata) with special reference to a striated appendage of the intercentriolar body

Summary The spermiogenesis of three species of the Parotoplaninae (Otoplanidae, Proseriata) is described based on electron-microscopical observations. Special reference is given to organelles which do not persist in mature male gametes. One of these organelles is a striated appendage of the intercentriolar body. This differentiation has not been reported from any other plathelminth taxa up to now. The striated appendage, which may serve as a strengthening element, is hypothesized to be an autapomorphic feature of the Parotoplaninae.     

Spermiogenesis and sperm in Mesostoma viaregginum (Plathelminthes, Rhabdocoela): an ultrastructural study to infer sperm orientation

Spermiogenesis in Mesostoma viaregginum begins with the formation of a zone of differentiation containing striated rootlets, two centrioles, and an intercentriolar body in-between. These centrioles generate two parallel free-flagella with the 9+“1” pattern of the Trepaxonemata growing out in opposite directions. Spermatid differentiation is characterised by a 90° latero-ventral rotation of flagella and a subsequent disto-proximal centriolar rotation, with a distal cytoplasmic projection. The former rotation involves the compression of a row of cortical microtubules and allows recognising a flagellar side and an aflagellar side in the late spermatid and in the mature spermatozoon. At the end of the differentiation, centrioles and microtubules lie parallel to the spermatid axis. The disto-proximal centriolar rotation is proposed as a synapomorphy for the Rhabdocoela. The modifications of the intercentriolar body during spermiogenesis and the migration of the nucleus and the centrioles towards the cytoplasmic distal projection are also described. The mature spermatozoon of M. viaregginum is filiform and tapered at both ends and presents many features found in the Rhabdocoela gametes. The nucleus disappears before the flagellar insertion and a density gradient of mitochondria is observed along the sperm axis. The anterior end of the spermatozoon of M. viaregginum is characterised by a tapering capped by a membrane expansion. This study has enabled us to describe precisely the orientation of spermatozoa in the Rhabdocoela in general: the centriolar extremity is proposed as the anterior one for the Rhabdocoela.     

Juxtanuclear changes during the early spermatogenesis in Lebistes reticulatus (Guppy)

Summary The sperm cell of Lebistes reticulatus during Spermatogenesis is studied. The nuclear differentiation correlate to the flagellar outgrowth. Differential distribution in the chromatin condensation corresponds to a new membrane synthesis at the centriolar side of the nucleus. The fan-shaped microtubular bundle in Juxtanuclear position is described and its function as a stabilizing entity is discussed. At the centriolar complex satellites and an intercentriolar lamellated body are investigated. In submicroscopic details the sperm cell of Lebistes distinctively differs from other species previously described.The present investigation was supported by a grant from the Pehr Oscar Klingendahl Foundation.The authors wish to thank Mr. Mauri Nyholm, M. Sc., for his technical advices and Miss Maria Sjöstedt for preparing the specimens.     

Ultrastructure of the lycophora larva of Gyrocotyle urna (Cestoda,Gyrocotylidea)

Summary The fine structure of the ciliated epidermis, the body musculature and the neodermis anlage cells of the free-swimming lycophora larva of Gyrocotyle urna Grube and Wagener, 1852, is described. The epidermis is syncytial and covers the whole body including a caudal cavity into which the larval hooks protrude. It contains several types of vesicles, mitochondria and membrane whorls but lacks nuclei, dictyosomes and endoplasmic reticulum. The locomotory cilia exhibit single rostrally directed rootlets. The body musculature consists of about 25 longitudinal and 42 circular muscles. Their nuclei are located proximally to the contractile elements. The neodermis anlage cells show numerous dictyosomes, elaborated cisternae of endoplasmatic reticulum, typical coated vesicles and membranous bodies. Extrusions of these cells do not penetrate the epidermis but contact it by desmosoms.The evolution of epidermal and neodermal structures of Gyrocotyle and other parasitic Platyhelminthes is discussed. The probable consequences of the lack of some types of organelles in the epidermis of Neodermata are considered.Abbreviations bb basal body - bl basal lamina - ci locomotory cilia - Ce epidermis of the caudal cavity - cr ciliary rootlet - di dictyosome - Ep epidermis - er endoplasmic reticulum - Hm hook musculature - ld lipid droplet - Lh larval hook - Lm longitudinal musculature - mi mitochondria - mt microtubule - mv microvilli - mw membrane whorl - Ne neodermis anlage cell - nu nucleus - Re receptor - Rm circular musculature - ve vesicles     

Sperm cells in pollen tubes ofNicotians tabacum L.: three-dimensional reconstruction,cytoplasmic diminution,and quantitative cytology

Summary The organization of the sperm cells and vegetative nucleus (male germ unit) ofNicotiana tabacum was examined 18 h after semivivo pollination using transmission electron microscopy, computerassisted serial section reconstruction and quantitative cytology. Based on a measurement of 11 cellular parameters in nine reconstructed sperm cell pairs, there are no statistically significant differences between the two cells. The S_vn is characterized by a strapshaped cytoplasmic extension that is physically associated with the surface of the vegetative nucleus. The nucleus is located adjacent to the sperm crosswall, with sperm organelles being distributed between the nucleus and the extension. The S_ua is a tapered cell with cytoplasmic areas at both poles and deep axial invaginations near the crosswall. This cell has a centrally-located nucleus and a largely polar distribution of organelles. Three mechanisms for cytoplasmic diminution were observed that appear to contribute actively to the loss of cytoplasmic volume and organelles: (1) enucleated cytoplasmic body production in the S_ua; (2) vesiculation at the tip of the cytoplasmic projection of the S_vn; and (3) vesicle-containing body accumulation in the periplasm of both the S_vn and S_ua.Abbreviations 3-D three-dimensional - ECB enucleated cytoplasmic body - MGU male germ unit - S_vn leading sperm cell - S_ua trailing sperm cell - TEM transmission electron microscopy - VCB vesicle-containing body     

Ultrastructure of spermatogenesis and sperm ofMulticotyle purvisi (Plathelminthes,Aspidogastrea)

Summary The ultrastructure of spermatogenesis is described for the first time in an aspidogastrean. The zone of differentiation which is usually formed during digenean spermiogenesis was not observed inMulticotyle purvisi. Instead, spermatid components are assembled within the common cytoplasmic mass before the outgrowth of spermatids. Microtubules, mitochondrion, nucleus and axonemes including their basal body regions, migrate from the cytoplasm into the spermatid which is pinched off at the level of the arching membrane. An unusual, complex structure of the basal body region is described. Intercentriolar bodies and striated rootlets are left behind and quickly disappear from the residual cytoplasm. Despite these atypical aspects, spermiogenesis results in the formation of mature sperm with the classical structure common to Digenea and Monogenea Polyopisthocotylea with the addition of some extra, non-cortical microtubules and a dense rod along part of the length of the sperm.Abbreviations used in the figures A cell type A, primary spermatogonium - AM arching membrane - AX axoneme - AZ attachment zone - B cell type B — spermatogonium - BB basal body region - C cell type C — spermatogonium - CEL central element - CI cisternae - CY cytophore - D cell type D — primary spermatocyte - DO doublet of microtubules - DR dark rod - E cell type E — multinucleate condensed cytophore - ER endoplasmic reticulum - G glycogen - GO Golgi body - I intercentriolar body - LB lamellate body - M mitochondrion - ME remnants of arching membranes - MT microtubules - N nucleus - R rootlet - S spermatid     

Ultrastructural study of two rumen fungi:Piromonas communis andSphaeromonas communis

Two species of strictly anaerobic rumen fungi,Sphaeromonas communis andPiromonas communis, were examined by light and electron microscopy (scanning and transmission). Although morphologically different (vegetative body, number of flagella per zoospore), the ultrastructure of these two microorganisms was rather similar to that ofNeocallimastix frontalis andN. patriciarum. Two types of organelles were regularly found, i.e., isolated or associated ribosomes in the form of aggregates and hydrogenosome-like organelles with an amorphous content that may be involved in energy generation for these mitochondria-free strictly anaerobic fungi. UnlikeN. frontalis, the distribution of organelles was homogenous.     

Fine Structure of the Mastigont System in Tritrichomonas foetus (Riedmüller)*

SYNOPSIS. Tritrichomonas foetus shares many fine-structural features with the previously described genera of the subfamily Trichomonadinae. These include the arrangement and structure of the kinetosomes, of most rootlet filaments, including the sigmoid filaments of kinetosome #2, as well as those of the parabasal apparatus and of the pelta-axostyle complex. On the other hand, this species, and presumably all other Tritrichomonas augusta-type flagellates, differ from Trichomonadinae in certain important details. Among the features which T. foetus does not share with Trichomonadinae are the fine structure of the costa and of the undulating membrane, as well as several organelles not found in the latter subfamily. The costal base of Trichomonadinae is replaced in T. foetus and other Tritrichomonadinae by a comb-like structure, extending between the costa and the infrakinetosomal body. The suprakinetosomal body, connected to kinetosome #2 in the region of attachment of the sigmoid filaments, and the infrakinetosomal body, which appears to contribute to the proximal marginal lamella, are organelles evidently restricted to Tritrichomonadinae. The undulating membrane consists of 2 parts. The proximal part is a fold-like differentiation of the dorsal body surface, the dorsal part of which contains the proximal marginal lamella. The distal part of the undulating membrane, with no obvious physical connection to the fold, encloses the distal marginal lamella in its ventral, and the microtubules of the recurrent flagellum in its dorsal area. The organelle of T. foetus which by its size, certain structural characteristics, and relationship with the undulating membrane and some organelles, including the paracostal granules, is analogous to the costa of Trichomonadinae and of Trichomitopsis termopsidis (subfamily Tritrichomonadinae), conforms in the structure of its periodic cross-striations to that of the parabasal filaments of the latter organisms; its origin corresponds closely to that of parabasal filament 2 of Trichomonadinae.     

Is protein degradation correlated with either the charge or size of Lemna proteins?

Evidence is presented that the organelles of Lemna minor do not degrade as functional units. The proteins of Lemna show wide differences in their rates of degradation and ribulose bisphosphate carboxylase (EC 4.1.1.39) has a particularly slow rate of degradation. Contrary to some earlier evidence, we found no correlation between the rate of soluble-protein degradation and either charge or size of proteins. We could find no correlation between protein degradation and subunit size in any of the organelles of Lemna.Abbreviations FPLC fast protein liquid chromatography - PAGE polyacrylamide gel electrophoresis - RuBPCase ribulose-1,5-bisphosphate carboxylase - SDS sodium dodecylsulphate - Tris 2-amino-2-(hydroxymethyl)-1,3-propanediol     

The ultrastructure of the extrusomes in <Emphasis Type="Italic">Pseudourostyla cristata</Emphasis>, a hypotrichous ciliated protozoan

By using scanning and transmission electron microscopy, the present study demonstrates a great number of trichocyst-like extrusomes distributed in the cortical cytoplasm of the protozoan Pseudourostyla cristata, a hypotrichous ciliate. Of these, the mature organelles are rod-shaped with a cap consisting of tubular structures, a tip located at the apex of the cap, a body consisting of strateform structures of uneven electron density and an elongated shaft located along the longitudinal central axis of the body. The electron microscopic observations suggest that the extrusive organelles in P. cristata might undergo a morphogenetic process including the following sequential events: the occurrence of the vesicles in the cytoplasm, the condensation of the fibrous substances within the vesicles, the appearance of the electron-dense shaft, and the formation of the cap. In contrast with a large quantity of extrusomes in trophozoit P. cristata, there are no such extrusive organelles in the encysted cells of the ciliate. The phenomena that P. cristata ciliates can readily enter physiological reorganization or encysting phases and discharge a great number of their extrusomes when prepared for SEM and TEM observation suggest that the extrusive process of the extrusomes in P. cristata might have an important influence on the life activity of the ciliate and could be one of the causes leading to the physiological reorganization and the encysting of the ciliate. These reactions of P. cristata might be a protective or defensive response to the environmental changes.     

Kinetics of the assembly of gas vacuoles in the blue-green alga Microcystis aeruginosa Kuetz. emend. Elekin.

Summary In exponentially growing cultures of the blue-green alga Microcystis aeruginosa the number of gas vacuoles per cell decreases and reaches a value of 4.5×10³ at 1.2×10⁷ cells per ml. The assembly of gas vacuoles with respect to number and length was followed after the organelles were caused to collapse by a pulse of ultrasound. The change in the number N of gas vacuoles per cell is N=224.8×t ^0.757, 0<t<24 h. After 24 h 50% of the value of non-sonicated cultures is reached. The changes in the length L of the organelles is expressed by L=87.06 ×t ^0.4084, 0<t<24 h. After 24 h 85% of the control value is reached.Abbreviations used EDTA ethylene diamine tetraacetate - BSA bovine serum albumine - P probability - N number of gas vacuoles - L length of gas vacuoles in nm - t time in hours     

Development of woronin bodies from microbodies inFusarium oxysporum f. sp.lycopersici

Summary Woronin bodies are cytoplasmic organelles which commonly lie near the septa in ascomycetous fungi. Although these organelles were observed nearly 100 years ago, little is known about their origin and development. The present ultrastructural investigation describes the ontogeny of Woronin bodies inFusarium oxysporum f. sp.lycopersici [Sacc.] Snyd. and Hans. In this fungus, Woronin bodies are produced by microbodies. Development of the Woronin body begins with the appearance of electron dense material within the microbody. This material aggregates adjacent to the membrane of the microbody and condenses into a single paracrystalline inclusion. Following its formation, the inclusion is gradually extruded and is eventually separated from the parent organelle by an exocytotic mechanism. After the separation, the paracrystalline inclusion is found at the septal pore. Although many recent electron microscopic studies have used various terms to designate these membrane bound organelles, inFusarium these inclusions are believed to correspond to the Woronin bodies initially described by light microscopists.     

Spermiogenesis in the cestode Corallobothrium solidum Fritsch, 1886 (Proteocephalidea: Corallobothriinae)

Spermiogenesis of Corallobothrium solidum Fritsch 1886, has been investigated by transmission electron microscopy. The zone of differentiation contains the two centrioles, each with one thin root, being orientated in the same plane only when a single intercentriolar body (ICB) appears between them. A median cytoplasmic process (MCP) develops distally to the two flagella, which are of unequal length, get longer and rotate towards the MCP. The nucleus penetrates into the spermatid body after the fusion of both flagella with the MCP has started. Flagellar roots occur occasionally in some spermatids. New for the Eucestoda are the following findings: 1. cortical microtubules (CMs) are arranged in two short parallel rows in one‐axoneme region of some spermatids; 2. the crested body of spermatid consists either of electron‐dense tubular elements and interposes itself between CMs, or it is rather homogeneous and situated more peripherally above one continuous semicircle of CMs. The present results support previous data that the type of spermiogenesis in proteocephalideans resembles mostly that observed in tetraphyllideans (Onchobothriidae and Phyllobothriidae), thus supporting the view of a close phylogenetic relationship of tetraphyllidean and proteocephalidean cestodes.     

Selective endosomal microautophagy is starvation-inducible in Drosophila

Autophagy delivers cytosolic components to lysosomes for degradation and is thus essential for cellular homeostasis and to cope with different stressors. As such, autophagy counteracts various human diseases and its reduction leads to aging-like phenotypes. Macroautophagy (MA) can selectively degrade organelles or aggregated proteins, whereas selective degradation of single proteins has only been described for chaperone-mediated autophagy (CMA) and endosomal microautophagy (eMI). These 2 autophagic pathways are specific for proteins containing KFERQ-related targeting motifs. Using a KFERQ-tagged fluorescent biosensor, we have identified an eMI-like pathway in Drosophila melanogaster. We show that this biosensor localizes to late endosomes and lysosomes upon prolonged starvation in a KFERQ- and Hsc70-4- dependent manner. Furthermore, fly eMI requires endosomal multivesicular body formation mediated by ESCRT complex components. Importantly, induction of Drosophila eMI requires longer starvation than the induction of MA and is independent of the critical MA genes atg5, atg7, and atg12. Furthermore, inhibition of Tor signaling induces eMI in flies under nutrient rich conditions, and, as eMI in Drosophila also requires atg1 and atg13, our data suggest that these genes may have a novel, additional role in regulating eMI in flies. Overall, our data provide the first evidence for a novel, starvation-inducible, catabolic process resembling endosomal microautophagy in the Drosophila fat body.     

Ultrastructure of spermiogenesis and spermatozoa in Prorhynchus sp. (Platyhelminthes,Lecithoepitheliata, Prorhynchidae)

Summary

Mature sperm of Prorhynchus sp. have an elongated nucleus, multiple mitochondria and dense bodies, and two free axonemes which are located in grooves of the main shaft for much of their length. The axonemes are subterminally inserted and have the typical 9+ ‘1’ arrangement unique to Platyhelminthes and synapomorphic for taxa of Trepaxonemata. The testis follicles examined had small numbers of developing spermatids and very few mature sperm were present. During spermiogenesis, spermatids remain joined in clusters by distinctive bridges. In each spermatid two centrioles (with an intercentriolar body between them) give rise to free axonemes which grow out in opposite directions from each other. Indistinct ciliary rootlets are present. The axonemes are carried distally from the main spermatid mass on an elongating process and turn back towards the main spermatid mass. Nucleus, mitochondria and dense bodies move into the shaft, and the spermatid elongates before detaching from others in the cluster. This is the first detailed study of sperm and spermiogenesis in Lecithoepitheliata. Mature sperm are distinctly different from those of prolecithophorans, to which they are reputedly related, the latter having aflagellate sperm without dense bodies.     

All <Emphasis Type="Italic">Trypanosoma cruzi</Emphasis> developmental forms present lysosome-related organelles

Trypanosoma cruzi epimastigote forms concentrate their major protease, cruzipain, in the same compartment where these parasites store macromolecules obtained from medium and for this ability these organelles were named as reservosomes. Intracellular digestion occurs mainly inside reservosomes and seems to be modulated by cruzipain and its natural inhibitor chagasin that also concentrates in reservosomes. T. cruzi mammalian forms, trypomastigotes and amastigotes, are unable to capture macromolecules by endocytosis, but also express cruzipain and chagasin, whose role in infectivity has been described. In this paper, we demonstrate that trypomastigotes and amastigotes also concentrate cruzipain, chagasin as well as serine carboxypeptidase in hydrolase-rich compartments of acidic nature. The presence of P-type proton ATPase indicates that this compartment is acidified by the same enzyme as epimastigote endocytic compartments. Electron microscopy analyzes showed that these organelles are placed at the posterior region of the parasite body, are single membrane bound and possess an electron-dense matrix with electronlucent inclusions. Three-dimensional reconstruction showed that these compartments have different size and shape in trypomastigotes and amastigotes. Based on these evidences, we suggest that all T. cruzi developmental stages present lysosome-related organelles that in epimastigotes have the additional and unique ability of storing cargo.     

The meiospore ofAllomyces

Summary The arrangement of cellular organelles within the meiospore ofAllomyces macrogynus was found to be similar to the zoospore of this species, with the exception that the meiospore contains membrane enclosed electron dense reserve material which has the appearance of the gamma bodies observed in the zoospores ofBlastocladiella. The three dimensional structure of the side body complex is analyzed with serial sections and compared to homologous organelles in other members of theChytridiomycetes.     

Ultrastructure of Spermatogenesis in the Testis of Paragonimus heterotremus

Lung fluke, Paragonimus heterotremus, is a flatworm causing pulmonary paragonimiasis in cats, dogs, and humans in Southeast Asia. We examined the ultrastructure of the testis of adult P. heterotremus with special attention to spermatogenesis and spermiogenesis using scanning and transmission electron microscopy. The full sequence of spermatogenesis and spermiogenesis, from the capsular basal lamina to the luminal surface, was demonstrated. The sequence comprises spermatogonia, spermatocytes with obvious nuclear synaptonemal complexes, spermatids, and eventual spermatozoa. Moreover, full steps of spermatid differentiation were shown which consisted of 1) early stage, 2) differentiation stage representing the flagella, intercentriolar body, basal body, striated rootlets, and electron dense nucleus of thread-like lamellar configuration, and 3) growing spermatid flagella. Detailed ultrastructure of 2 different types of spermatozoa was also shown in this study.