Protein Uptake and Digestion in Bloodstream and Culture Forms of Trypanosoma brucei*

SYNOPSIS. The mechanisms of ferritin uptake and digestion differ in bloodstream and culture forms of Trypanosoma brucei. Ferritin enters bloodstream forms from the flagellar pocket by pinocytosis in large spiny-coated vesicles. These vesicles become continuous with straight tubular extensions of a complex, mostly tubular, collecting membrane system where ferritin is concentrated. From the collecting membrane system the tracer enters large digestive vacuoles. Small spiny-coated vesicles, which never contain ferritin, are found in the Golgi region, fusing with the collecting membrane system, and around the flagellar pocket. Acid phosphatase activity is present in some small spiny-coated vesicles which may represent primary lysosomes. This enzymic activity is also found in the flagellar pocket, pinocytotic vesicles, the collecting membrane system, the Golgi (mature face), and digestive vacuoles of bloodstream forms. About 50% of the acid phosphatase activity of blood forms is latent. The remaining nonlatent activity is firmly cell-associated and probably represents activity in the flagellar pocket. The structures involved in ferritin uptake and digestion are larger and more active in the short stumpy than in the long slender bloodstream forms. The short stumpy forms also have more autophagic vacuoles. No pinocytotic large, spiny-coated vesicles or Golgi-derived, small spiny-coated vesicles are seen in culture forms. Ferritin leaves the flagellar pocket of these forms and enters small smooth cisternae located just beneath bulges in the pocket membrane. The tracer then passes through a cisternal collecting membrane network, where it is concentrated, and then into multivesicular bodies. In the culture forms, acid phosphatase activity is localized in the cisternal system, multivesicular bodies, the Golgi (mature face), and small vesicles in the Golgi and cisternal regions. The flagellar pocket has no acid phosphatase activity, and almost all the activity is latent in these forms. The culture forms do not release acid phosphatase into culture medium during 4 days growth. Uptake of ferritin by all forms is almost completely inhibited by low temperature. These differences among the long slender and short stumpy bloodstream forms and culture forms are undoubtedly adaptive and reflect different needs of the parasite in different life cycle stages.     

The Form and Function of the Cytostome-Cytopharynx of the Culture Forms of the Elasmobranch Haemoflagellate Trypanosoma raiae Laveran & Mesnil

SYNOPSIS. In the culture forms of the elasmobranch trypanosome Trypanosoma raiae is found a prominent cytopharyngeal complex. This consists of a group of 5 or 6 microtubules associated with a deep invagination of the cell membrane which arises from a cytostome near the opening of the flagellar pocket. This structure is a constant feature of the various epimastigote and trypomastigote forms that this flagellate has in culture. Replication of the cytopharyngeal apparatus is completed before cytokinesis.
Experiments using ferritin as an electron dense tracer show that endocytosis occurs from the blind ending of the cytopharynx both in the exponential and stationary phases of growth in vitro. Ferritin is transported from the cytopharynx by endocytotic vesicles to large, membrane-bound vacuoles in the posterior region of the cell. Ultrastructural location of non-specific acid phosphatase within these digestive vacuoles and also within the Golgi apparatus is reported.
Coated vesicles found in association with the flagellar pocket are another route of uptake of ferritin by T. raiae.     

THE FINE STRUCTURE OF BLASTOCLADIELLA EMERSONII ZOOSPORES

The zoospore of Blastocladiella emersonii has been re-examined with the electron microscope. The following new findings were made. A double unit-membrane system surrounds all cell organelles except γ-bodies, vacuoles and a few fragments of membranes. Lipid granules on one side of the large mitochondrion alternate with vesicles. The kinetosome of the posterior flagellum does not have any central fibrils as previously reported; a small, cylindrical structure is found within its anterior end. An associated centriole is located next to the kinetosome. Three striated rootlets pass from the kinetosome by separate channels through the mitochondrion. There appears to be no connection between the striated rootlets and the mitochondrion. Microtubules originating at the anterior end of the kinetosome pass into the cytoplasm between the mitochondrion and the nuclear cap. Long, dense strands were observed in some nuclei. The axoneme is taken up into the spore during encystment and is found in the freshly encysted spore. No trace of the flagellar sheath has been found in the encysted spore.     

The Fine Structure of the Macrogametocytes of Adelina tribolii Bhatia, 1937 (Eucoccidia, Telosporea) from the Fat Body of the Beetle Tribolium castaneum Hbst.

SYNOPSIS. Macrogametocytes of the coccidium Adelina tribolii Bhatia, 1937 are described from the time when they settle in the fat body of the host and form periparasitic vacuoles around them to the stage of microgametocyte occurrence and the beginning of syzygy formation.
The macrogametocyte is surrounded by a 2-layered pellicle 50 mμ thick. Its continuity is interrupted by one or several micropores 40 mμ across and 86 mμ deep.
The cytoplasm of the parasite contains numerous vesicles and lamellae of rough and smooth endoplasmic reticulum. Mitochondria of various sizes have short tubules. The macrogametocyte contains a variable number of dark bodies 1.4-2.4 μ in diameter. It also contains several vacuoles up to 1.2 μ which are covered with a 3-layered membrane and enclose a granular material.
In old macrogametocytes in syzygy multivesicular bodies develop which measure up to 2.4 by 1.6 μ. Several smaller vacuoles containing granular material are also a constituent of the electrondense basic substance of these corpuscles.
Paraglycogen granules 1.4 by 0.9 A occur in old macrogametocytes and are situated inside the vacuoles which are not bordered by a membrane. The numbers and size of these granules increase with the age of the parasite. The Golgi complex lies close to the nucleus.
The nucleus, 6-8.5 μ in diameter, is in the center of the macrogametocyte and contains a large eccentric nucleolus. The nuclear membrane is 2-layered and has many pores.     

薏苡胚乳细胞化的超微结构观察

采用透射电镜对薏苡早期的胚乳细胞化进行了研究,在胚乳游离核时期,胚乳游离核及细胞质绕中央细胞分布,游离核间没有发现胚囊壁内突、成膜体等结构。胚乳细胞化过程中初始垂周壁形成过程如下：（１）胚乳细胞质中出现液泡,使细胞质和核向中央液泡推进：（２）一对相邻细胞核间液泡成对存在,且呈垂周分布,而且两液泡间的细胞质很狭窄;（３）在这狭窄的细胞质中出现成行排列的小泡;（４）小泡融合形成细胞板,细胞板悬于两液泡     

Do Protoplasmic Connections Function in the Phototactic Coordination of the Volvox Colony During Light Stimulation?*

SYNOPSIS. The flagellar behavior of the colonial flagellates Volvox carteri Stein and Volvox perglobator Powers was examined by placing 1.01 μm polystyrene particles in solution with swimming colonies, and photographing these particle movements. When directional light stimulation was administered to individual colonies, a cessation of flagellar activity occurred in the anterior cells of the stimulated side in both species. Since Volvox perglobator possesses prominent intercellular connections and Volvox carteri does not, the results of these experiments suggest that the connections linking colony members in some species do not function in the coordination of flagellar activity associated with light orientation behavior.     

The Fine Structure of Trypanosoma congolense in Its Bloodstream Phase

SYNOPSIS. The fine structure of 2 isolates of Trypanosoma congolense maintained in laboratory rodents has been studied from thin sections of osmium- and aldehyde-fixed flagellates. The pellicular complex, nucleus, and flagellar apparatus are all similar to those of other African trypanosomes. Aberrant intracellular differentiation of the flagellum is occasionally found. As in bloodstream forms of other salivarian trypanosomes the single mitochondrion forms an irregular canal running from one end of the body to the other, with a shallow bowl-shaped expansion forming a capsule for the fibrous kinetoplast (mitochondrial DNA). A connexion between the mitochondrial envelope of the kinetoplast and the basal body of the flagellum is not evident, and sometimes the flagellum base is not even apposed to the kinetoplast but lies behind it. Tubular cristae are present in the mitochondrial canal and, by light microscopy, this structure gives a positive reaction for NAD diaphorase suggesting at least some activity in electron transport, even tho at this stage in its life cycle respiration is doubtfully sensitive to cyanide and cytochrome pigments are in all probability absent. The region of the cytoplasm between the nucleus and the flagellar pocket has all the trappings associated with secretory cells in higher animals, or with the secretion of surface structures in phytoflagellates. just behind the nucleus a limb of granular reticulum subtends a Colgi stack of flattened saccules with attendant vesicles. Close to the distal pole of the Golgi complex is a network of smooth-membraned cisternae, termed here the agranular or secretory reticulum, which undergoes localized swelling with the accumulation of a secretory product to form large spherical sacs or vacuoles. These network-linked vacuoles probably correspond to the post nuclear vacuole complex visible by light microscopy. From its apparent secretory function this complex is regarded here as being possibly an extension or derivative of the Golgi complex, the smooth-membraned tubules lying alongside the 2 structures possibly representing a link between them. By analogy with phytoflagellates and the secretory cells of higher animals, it is suggested that the secretion is transported for discharge into the flagellar pocket by way of multivesicular bodies and smooth-walled tubules or vesicles. Spiny pits in the wall of the flagellar pocket, and similar-sized vesicles in the nearby cytoplasm, could be stages in either exocytosis of secretion or endocytosis (pinocytosis). It is tentatively suggested that the secretion may be the material from which the surface coat is formed. Neither a cytostome nor a contractile vacuole has been observed in T. congolense.     

ULTRASTRUCTURE OF THE FLAGELLA OF THE COLORLESS PHAGOTROPH PERANEMA TRICHOPHORUM (EUGLENOPHYCEAE).II. FLAGELLAR ROOTS1

Peranema trichophorum (Ehrenberg) Stein, a colorless phagotrophic euglenoid flagellate, has a typically euglenoid microtubular root complement. Striated root components, relatively uncommon in euglenoids, are connected to the basal bodies and to a microtubular root. The flagellar system of Peranema consists of three unequal microtubular roots which extend anteriorly beneath the reservoir membrane, and narrow-band striated roots (periodicity = 29–33 nm) which connect one of the four basal bodies to the movable rodorgan of the feeding apparatus. An inter basal body striated fiber forms a three-way connection between one particular microtubular root, a flagellar basal body, and the striated roots. A striated fibril (periodicity = 18–25 nm), which may be an extension of the striated root system, extends beneath the reservoir membrane. Associated with the striated fibril and the striated roots are cisternae of smooth endoplasmic reticulum.     

Vesicle transport and processing of the precursor to 2S albumin in pumpkin

Cell fractionation of pulse-chase-labeled developing pumpkin cotyledons demonstrated that proprotein precursor to 2S albumin is transported from the endoplasmic reticulum to dense vesicles and then to the vacuoles, in which pro2S albumin is processed to the mature 2S albumin. Immunocytochemical analysis showed that dense vesicles of about 300 nm in diameter mediate the transport of pro2S albumin to the vacuoles.
The primary structure of the precursor (16 578 Da) to pumpkin 2S albumin has been deduced from the nucleotide sequence of an isolated cDNA insert. The presence of a hydrophobic signal peptide at the N-terminus indicates that the precursor is a preproprotein that is converted into pro2S albumin after cleavage of the signal peptide. N-terminal sequencing of the pro2S albumin in the isolated vesicles revealed that the signal peptide is cleaved off co-translationally on the C-terminal side of alanine residue 22 of prepro2S albumin. By contrast, post-translational cleavages occur on the C-terminal sides of asparagine residues 35 and 74, which are conserved among precursors to 2S albumin from different plants. Hydropathy analysis revealed that the two asparagine residues are located in the hydrophilic regions of pro2S albumin. These findings suggest that a vacuolar processing enzyme can recognize exposed asparagine residues on the molecular surface of pro2S albumin and cleave the peptide bond on the C-terminal side of each asparagine residue to produce mature 2S albumin in the vacuoles.     

Ultrastructure of the scale-covered zoospores of the green alga Chaetosphaeridium, a possible ancestor of the higher plants and bryophytes

The zoospores of the green alga Chaetosphaeridium globosum are covered on all surfaces with tiny diamond-shaped scales similar to those of the prasinophycean flagellates and the Charales. The flagella also bear striated hairs (hair scales) so far considered to be a characteristic of the Prasinophyceae. The flagellar apparatus differs from that observed in the Prasinophyceae, shows many similarities to that of the Charales, and is identical with the "Vierergruppe" of the pteridophytes, cycads and bryophytes.
The zoospores are opisthokont, with two flagella inserted subapically. There is a lateral chloroplast containing typical grana and intergranal lamellae, but no eyespot. The very complicated Golgi body/contractile vacuole system comprises 10–20 contractile vacuoles. A microbody occupies a characteristic position in the cell, and in a young germling contains a crystalline inclusion.
The ultrastructure of the zoospore supports the old theory that the ancestors of the higher plants may well be found among Coleochaete and its relatives, past and present.     

Ultrastructure and Vacuolar Movements in the Free-Living Diplomonad Trepomonas agilis Klebs*

SYNOPSIS. The structure of Trepomonas agilis communis Klebs is described from light and electron microscope observations on 2 clone isolates of the organism. The surface membrane shows marked differentiation into an extremely thick (16 nm) symmetric membrane which covers the greater part of the body, and a thinner (∼ 10–12 nm) asymmetric membrane which lines the 2 lateral oral grooves and the posterior channel connecting them; a similar asymmetric membrane covers the flagella. Thorium dioxide staining suggests a denser distribution of acidic carbohydrate groups on the asymmetric membrane. The pathways of cytoplasmic streaming observed in the living flagellate coincide with those of microtubule bands arising close to the flagellar basal bodies and it is suggested that the bands play an orienting role in the streaming of food vacuoles. The contractile vacuole undergoes diastole in the anterior (postnuclear) cytoplasm, and is formed by coalescence of smaller vesicles. At systole the entire vacuole migrates to the posterior extremity to discharge into the posterior channel; the route of exit lacks guiding structural elements. Features of the flagellate's physiology and organization are discussed in relation to the observed lack of mitochondria, microbodies and Golgi apparatus in diplomonads.     

The neural gland in tunicates: fine structure and intracellular distribution of phosphatases

Summary The cells comprising the neural gland in the ascidians Ciona, Styela, and Botryllus have been examined for their fine structural features and enzyme cytochemistry. The gland cells are either cuboidal or irregular in outline. They are full of small vesicles, of which some are pinocytotic, as well as larger vacuoles; they become increasingly vacuolated as their shape decreases in regularity. At the same time, glycogen deposits accumulate and the cisternae of the endoplasmic reticulum become distended. Some of the vacuoles contain an electron dense material or a fibrillar substance, but the cells contain no obvious electron opaque secretory granules associated with an extensive Golgi complex such as occur in the vertebrate adenohypophysis.Acid phosphatase is localized in some of the vesicles and vacuoles, indicating that they are a kind of lysosome, the latter possibly representing autophagic vacuoles. Thiamine pyrophosphatase is also found in many vacuoles as well as in the saccules of the Golgi apparatus which in these cells is in the form of dictyosomes.The results suggest a developmental cycle of increasing cytoplasmic vacuolation, ultimately leading to a breakdown and release of the vacuolar products. The significance of these observations is considered, particularly with respect to the hypothesis that the gland represents the ascidian equivalent of the vertebrate pituitary.I am grateful to Miss Yvonne R. Carter for technical assistance with the photography and to Mr. John Rodford for producing the diagram.     

Golgi apparatus activity and membrane flow during scale biogenesis in the green flagellateScherffelia dubia (Prasinophyceae). I: Flagellar regeneration

Summary Cells ofScherffelia dubia regenerate flagella with a complete scale covering after experimental flagellar amputation. Flagellar regeneration was used to study Golgi apparatus (GA) activity during flagellar scale production. By comparing the number of scales present on mature flagella with the flagellar regeneration kinetics, it is calculated that each cell produces ca. 260 scales per minute during flagellar regeneration. Flagellar scales are assembled exclusively in the GA and abstricted from the rims of thetrans-most GA cisternae into vesicles. Exocytosis of scales occurs at the base of the anterior flagellar groove. The central portion of thetrans-most cisterna, containing no scales, detaches from the stack of cisternae and develops a coat to become a coated polygonal vesicle. Scale biogenesis involves continuous turnover of GA cisternae, and scale production rates indicate maturation of four cisternae per minute from each of the cells two dictyosomes. A possible model of membrane flow routes during flagellar regeneration, which involves a membrane recycling loop via the coated polygonal vesicles, is presented.     

A fine structure study of venom gland cells in globiferous pedicellariae from Stronglocentrotus purpuratus (Stimpson)

Cells in secretory glands of globiferous pedicellariae from Strongylocentrotus purpuratus (Stimpson) were studied with the electron microscope and subjected to preliminary light microscopic, histochemical analysis. Specimens for electron microscopic observation were fixed with chilled 2% glutaraldehyde in sea water postfixed in cold 1.33% osmic acid, and embedded in Araldite 502 epoxy resin Samples for histochemical analysis were fixed in the same manner, and then embedded in n-butylmethacrylate. Secretory cells line and fill partially bifurcated, muscular gland sacs located peripherally on each of three jaw elements comprising the pedicellarial head. Cells from venom glands are typically mucoid in appearance, possessing small volumes of basally displaced, vesiculated cytoplasm and an extensive system of vacuoles dominating the apical nine-tenths of each cell. These vacuoles enclose ground substances of various densities and staining affinities. Despite their extensive vacuolation, gland cells contain numerous cytomembrane complexes indicating metabolic activity just prior to fixation. Deciduous endoplasmic reticulum, Golgi complexes, large vacuoles, and various species of vesicles associated with these membrane systems are found in spatial proximity which indicates an apparent biosynthetic association. Preliminary histochemical tests on sections embedded in acrylic plastic indicate vacuolar products may consist of protein and nonsulfated acid mucosubstances. Gland cells are probably holocrine in function, releasing their vacuolar complement upon constriction of the muscular gland sac. There is no evidence indicating delivery of non-membrane bounded, granular secretion to an acellular lumen within the gland sac.     

Fine structure of the gastric epithelium of the ascidian botryllus schlosseri vacuolated and zymogenic cells

Summary Vacuolated and zymogenic cells, which are two of five cell types identified by electron microscopy in gastric epithelium of B. schlosseri, are described in detail. The vacuolated cells are characterized by one, or a few, supranuclear vacuoles containing myelin figures. A peculiar Golgi apparatus is consistently found at the base of the vacuoles; it consists of cisternae frequently containing small vesicles and tubules of constant diameter and/or a strong electron-opaque material. A variety of vesicles and multivesicular bodies are visible in the apical cytoplasm below long ribbon-like microvilli. The se findings suggest that the vacuolated cells are involved in absorptive and perhaps secretory activity. The zymogenic cells are characterized by a highly developed RER, numerous apical secretory granules and a well developed supranuclear Golgi apparatus. At the apical end, autophagosomes are frequently encountered, some of which contain also zymogen granules. Both cell types contain numerous lipid droplets, which are interpreted as an energy reserve available for the cells and for the entire colony during the change of generation. Correlation between structure and function in both cell types is discussed by taking into account the peculiar life cycle of B. schlosseri, as well as previously reported data on similar cells in other ascidians.We would like to dedicate this work to Prof. Giuseppe Reverberi on the occasion of his 70th birthday.The authors are indebted to Profs. A. Sabbadin and G. Mazzocchi for their most helpful suggestions and advice. We would also like to thank Mr. G. Tognon for technical assistance and the staff of the Stazione Idrobiologica di Chioggia for their assistance in collecting material. — This research was supported by a grant of C.N.R., contract from the Istituto di Biologia del Mare, Venezia, No. 7100396/04115542 and with the E.M. facilities of C. N. R. contract No. 70.01798.04.115.876.     

The Ultrastructure of Lankesterella hylae

SYNOPSIS. The ultrastructure of Lankesterella hylae was studied and numerous points of similarity to Plasmodium, Toxoplasma, Sarcocystis and Lankesterella garnhami were found. The protozoa were intracellular and lay within vacuoles containing vesicles, unusual membrane formations and dense granular material. The parasite was invested by a double membrane and had a micropyle, as well as membranous processes extending from the surface. At the anterior end were conoid and apical rings. The cell contained a nucleus, nucleolus, bipolar paranuclear vacuoles or bodies, a series of microtubules beneath the pellicle, endoplasmic reticulum, mitochondria, toxonemes and a variety of vacuoles. In addition, dense particles, similar to those related to the endoplasmic reticulum, were scattered throughout the cytoplasm.
The unusual membrane formations and vesicles in the periparasitic vacuoles were striking observations possibly related to the nutrition of the parasite.     

Food uptake and fine structure of Cryothecomonas longipes sp. nov., a marine nanoflagellate incertae sedis feeding phagotrophically on large diatoms

Cryothecomonas longipes Schnepf and Kühn sp. nov. is a colourless biflagellate organism, 9–14 μm long and 7–9 μm wide when not filled with food vacuoles. It was detected in the North Sea, feeding with pseudopodia on diatoms. It penetrates the host shell, while the main body of the flagellate remains outside the frustule. Cells are covered with a multilayered theca. The pseudopodium protrudes through a preformed slit in the theca. Each flagellum also emerges through a pit in which the theca forms a funnel of complex structure that girdles each flagellum. The anterior flagellum is 9–15 μm long and oriented forward; the ventral flagellum, posteriorly directed, is 20–24 μm long and bears fine hairs. The flagellar roots consist of microtubules that emerge at satellites around the basal bodies and run along the flagellar pits. In addition, the ventral flagellum is accompanied by a band of six microtubules. It is proximally attached to a small fibrillar band, which interconnects the basal bodies. Cryothecomonas longipes has two or three types of extrusomes which pierce the theca when discharged. Their mode of discharge is discussed. Microbody-like vesicles containing small tubules are closely associated with older digestion vacuoles. Cryothecomonas longipes is compared with other species of the genus and a diagnosis is given. Received: 4 March 1999 / Received in revised form: 28 July 1999 / Accepted: 30 August 1999     

The light organ and ink sac of Heteroteuthis dispar (Mollusca: Cephalopoda)

There has previously been some dispute over the source of the light of Heteroteuthis. Light and electron microscopy have shown that there are no bacteria in the cavity of the luminous gland, but rather a population of spherical vesicles of varying size and content, surrounded by dense interstitial material. The contents are secreted by the cells surrounding the gland via a microvillous brush border that contains cilia. The gland is surrounded by a reflector layer made up of iridophores, whose structure differs considerably in the proximal, lateral and cap regions.
The ink sac contains masses of spherical dense granules and its wall cells have many microvilli extending amongst these granules.     

The Fine Structure of the Colonial Kinetoplastid Flagellate Cephalothamnium cyclopum Stein

Cell structure, cell adhesion, and stalk formation have been examined by electron microscopy in the colonial flagellate, Cephalothamnium cyclopum. Each cell is obconical or spindle-shaped, pointed posteriorly and truncated anteriorly. The cell membrane is underlain by epiplasm 0.1 μm thick in the posterior region, but bands of microtubules support the anterior region which is differentiated into a flagellar pocket, oral apparatus and contractile vacuole. Each of 2 flagella, joined a short way above their bases by an interflagellar connective, has a paraxial rod and mastigonemes. One flagellum is free and is important in food gathering while the other is recurrent and lies in a shallow groove on the ventral cell surface but projects posteriorly into the stalk. The basal bodies of these flagella are bipartite structures connected by a pair of striated rootlets with accessory microtubular fibers. The oral apparatus consists of a funnel-shaped buccal cavity and cytostome. It is supported by helical and longitudinal microtubules and also has nearby striated and microtubular fibers. Possible roles of associated oral vesicles in relation to ingestion are discussed. A reticulate mitochondrion houses a massive kinetoplast which has a fibrillar substructure resembling that of dinoflagellate chromosomes. Adjacent flagellates adhere by laminate extensions of their posterior regions and attach by their recurrent flagella to a communally secreted stalk composed of finely fibrillar material. This study indicates that Cephalothamnium belongs in the order Kinetoplastida, and has many features in common with members of the family Bodonidae.     

ENTOSIPHON SULCATUM (EUGLENOPHYCEAE): FLAGELLAR ROOTS OF THE BASAL BODY COMPLEX AND RESERVOIR REGION1,2

The flagellar root system of Entosiphon sulcatum (Dujardin) Stein (Euglenophyceae) is described and compared with kinetoplastid and other euglenoid systems. An asymmetric pattern of three microtubular roots, one between the two flagellar basal bodies and one on either side (here called the intermediate, dorsal, and ventral roots), is consistent within the euglenoid flagellates studied thus far. The dorsal root is associated with the basal body of the anterior flagellum (F₁) and lies on the left dorsal side of the basal body complex. Originating between the two flagellar basal bodies, and associated with the basal body of the trailing flagellum (F₂), the intermediate root is morphologically distinguished by fibrils interconnecting the individual microtubules to one another and to the over lying reservoir membrane. The intermediate root is often borne on a ridge projecting into the reservoir. The ventral root originates near the F₂ basal body and lies on the right ventral side of the cell. Fibrillar connections link the membrane of F₂ with the reservoir membrane at the reservoircanal transition level. A large cross-banded fiber joins the two flagellar basal bodies, and a series of smaller striated fibers links the anterior accessory and flagellar basal bodies. Large nonstriated fibers extend from the basal body complex posteriorly into the cytoplasm.