Ultrastructure of the salivary glands of the planthopper,peregrinus maidis (ashmead) (Homoptera : Delphacidae)

The principal salivary gland of the planthopper, Peregrinus maidis (Ashmead) (Homoptera : Delphacidae), comprises 8 acini of only 6 ultrastructurally different acinar types. In these acini, secretory cells contain elongated vacuoles partly lined by microvilli and by microtubule bundles. These vacuoles are apparently connected with extracellular canaliculi deeply invaginated into secretory cells. Canaliculi of each acinus lead to a ductule lumen, which is lined with spiral cuticular intima, surrounded by duct cells. Striated muscle fibers, supplied with small nerve axons and tracheoles, are found in various acini of the principal gland, usually around secretory and duct cells.In the accessory salivary gland, the 2 large secretory cells contain no elongated vacuoles or canaliculi invaginations. However, in their central region, apically, these cells border a large microvilli-lined canal with its own canal cells. This canal is apparently connected with the cuticle-lined accessory duct, formed by duct cells. Nerve axons, but no muscle fibers, are found in the accessory gland and its duct. It is suggested that the system for transporting secretory material within acini of the principal gland, is basically different from that within the accessory gland.     

Ultrastructural and functional aspects of the spermatheca of the African Migratory Locust Locusta migratoria migratorioides (Reiche and Fairmaire) (Orthoptera: Acrididae)

The ultrastructure of the spermathecal epithelium of the African Migratory Locust Locusta migratoria migratorioides R. & F. (Orthoptera: Acrididae) was investigated with the aid of transmission and scanning electron microscopic methods. The unpaired spermatheca can be subdivided into a multiple coiled tube and a terminal bulb region with vestibule, small apical and extensive pre-apical diverticulum. The wall of the spermatheca consists of a chitin intima, a layer of epithelial cells with a distinct apical microvilli border and a layer of gland cells, whereby slender projections of the epithelial cells extend between the gland cells. Through extensive folding, the basal plasma membrane of the gland and epithelial cells form a huge labyrinth, which is bounded by a basal lamina. Extending into the above mentioned projections there are bundles of parallel-arrayed microtubules, which run perpendicular to the microvilli border of the epithelial cell. They end in the base region of the microvilli and in the basal labyrinth on hemidesmosomes and serve to provide a mechanically stressable anchorage for the epithelium. The gland cells show structures typical for the production of export proteins: ribosomes, rER, dictyosomes, as well as vesicles of different size and electron-density. Every gland cell contains an extracellular cavity, arising through invagination, which is coated with a microvilli border. Over an end-apparatus and a ductule joining onto it (also with chitin intima) the lumen of the extracellular cavity is connected with the spermathecal lumen. The release of secretions and other substances from the epithelium into the spermatheca lumen is as possible as the uptake of substances from the latter into the epithelium. Regional differences in the fine structure of the cuticular intima, epithelial and gland cells point to different functions of the epithelium in these regions.     

Ejaculatory duct of the migratory grasshopper,Melanoplus sanguinipes (fabr.) (Orthoptera : Acrididae): A histological and ultrastructural analysis

The ejaculatory duct of the migratory grasshopper (Melanoplus sanguinipes [Fabr.]) (Orthoptera : Acrididae) is divisible into 3 regions: upper ejaculatory duct (UED) into whose anterior end the accessory glands and vasa deferentia empty; the funnel characterized by its slit-like lumen; and the lower ejaculatory duct (LED). Anteriorly, the UED has a keyhole-shaped lumen surrounded by a thin intima and highly columnar epithelial cells whose most conspicuous feature is massive aggregations of microtubules. More posteriorly, the UED lumen differentiates into dorsal and ventral chambers, the former having a thick cuticular lining armed with spines. In the hindmost part of the UED, the ventral chamber expands to obliterate the dorsal chamber; its cuticular lining thickens, and conspicuous lateral evaginations develop. The thick cuticle includes 3 distinct layers and on its surface carries numerous spatulate processes. In this region, the epithelial cells develop numerous short microvilli beneath which are many mitochondria. As the funnel is reached, the intima becomes extremely thick, and the epithelial cells lack microvilli and most microtubules. Within the funnel, a new, very distinct form of cuticle appears, which is in “units”, each associated with an epithelial cell and having a rounded epicuticular cap. The new cuticle arises ventrally but rapidly spreads to encircle the entire lumen, at which point the LED is considered to begin. Beneath this new cuticle, the epithelial cells are columnar, have long microvilli, numerous mitochondria in the apical cytoplasm, and rough endoplasmic reticulum basally. Apically, adjacent cells are tightly apposed; however, prominent intercellular channels develop more basally. The ejaculatory duct's features are briefly discussed in terms of its role in spermatophore formation.     

Development of female accessory glands of Chrysomya putoria (Wiedemann) (Diptera: Calliphoridae) during oogenesis

Females of Chrysomya putoria (Diptera: Calliphoridae) have two sexual accessory glands, which are tubular and more dilated at the distal extremity. The glands open independently into the common oviduct. Two morpho-physiological regions were distinguished in the longitudinal semi-thin sections of the glands. The secretory region is constituted by three layers: a cuticular intima, lining the lumen, followed by a layer of small cells, and then a layer of very large secretory cells. The ductal region of the gland presents only two layers: the cuticular intima and a cellular layer. In both regions a basement membrane is present. Each secretory cell has in its apical region a reservoir, which enlarges throughout oogenesis; in its basal region there is a large nucleus. The ductal cells are cylindrical and smaller than the secretory cells. The glandular secretion is synthesized in the cytoplasm of the secretory cells, stored and/or modified in the reservoir, then drained to the lumen through an end apparatus seen in the apical region of the secretory cell. Histochemical tests indicate that this secretion is a glycoprotein. Measurements of the glands from females at different physiological conditions and fed on different diets correlate with the results obtained for changes in the ovary during oogenesis. Cell number averaged 561.2 ± 77.54 per gland. There was no increase in cell number during oogenesis.     

Gut morphology of Mastotermes darwiniensis Froggatt (Isoptera : Mastotermitidae)

The digestive system of Mastotermes darwiniensis (Isoptera : Mastotermitidae) is similar to that of other lower termites. The cuticle in the proventriculus of the foregut is sculptured into 6 large dentate plates. Large setae are dispersed over the 1st and 2nd order folds and small setae are on the 3rd order folds. Epithelial cells in the foregut are of one type. The midgut cells are of one functional type, with 3 stages of the developmental cycle clearly distinguishable at any one time. There is no close association of mitochondria with the apical plasmalemma or microvilli. The epithelium rests on a basal lamina and has regularly distributed regenerative crypts. The midgut cells contain a large number of mitochondria close to the basal plasmalemma. Invaginations of the basal plasmalemma are very extensive and small tracheoles are plentiful close to the basal lamina. The presence of rough endoplasmic reticulum, most of which exists in the supranuclear cytoplasm, indicates that protein synthesis occurs in these cells. An abundance of basal plasmalemma invaginations is indicative of some fluid transport occurring across the membranes. The malpighian tubules have accumulations of mineral concretion forms as well as glycogen. Tracheoles are fairly abundant and distributed around the tubules. Epithelial cells in the region where the malpighian tubules join the midgut contain granules which are presumed to be secretory. Dentate plates around the anterior colon entrance are oriented so as not to hinder the flow of the lumen contents towards the posterior colon. Invaginations of the apical plasmalemma of the normal paunch epithelial cell suggest that they are involved in fluid or solute uptake from the lumen. The cuticle of the hindgut consists of areas with adhering bacteria and areas showing an even distribution of pores free of bacteria. The epithelial cells of the anterior colon resemble those in the paunch. The epithelial cells of the posterior colon show 3 variations: a squamous-cuboidal cell with unconstricted lumen; a cuboidal-columnar cell type found at the constriction site close to the rectum; a second squamous-cuboidal cell type constituting the junction of the colon and the rectum. This last cell type shows an abundance of cytoplasmic microtubules and a thick subcuticular zone.     

Spermiolytic activity of the epithelium of the spermathecal duct of Rhacocleis annulata fieber (Orthoptera : Tettigoniidae)

This study reports, for the first time, lytic activity in the distal and median regions of the spermathecal duct of Rhacocleis annulata Fieber (Orthoptera: Tettigoniidae). Lysis is more pronounced in recently mated females, and appears to take place in a progressive sequence originating in the cells underlying the cuticular intima. These cells exhibit large heterogeneous vesicles resembling lysosomes, which would participate in the partial dismantling of the cuticular intima. Consequently, the sperm found in the lumen of the latter organ penetrate the cells, probably pushed by the pressure exerted on the luminal walls, and then, together with the cells themselves, undergo lysis. Degradation of spermatozoa seems to follow a strict sequence of events, which ends with the dismantling of the microtubules of the axoneme, as reported previously for Locusta (Cantacuzène, 1971) and for some pulmonate gastropods (Bayne, 1970). We propose that lysis is part of the mechanism dealing with capture and subsequent elimination of surplus sperm transferred to the female during copulation. Accordingly, fertilization activity would occur exclusively within the seminal receptacle. No evidence of a similar phenomenon in the latter organ has previously been reported for Rhacocleis annulata.     

The Electron Microscopy of the Left Colleterial Gland of the Cockroach

A study has been made of the cells of the left colleterial gland of the cockroach, Periplaneta americana (L.), using the electron microscope, and the results compared with previous histological and histochemical studies. The colleterial gland consists of an arborescent bunch of long tubules composed mainly of the cells which secrete the structural protein of the egg case ("type 4 cells"). Other types of cells: chitinogenic cells and "type 2 and 3 cells" each with a different cytology are described. The type 4 cells, which form the structural protein, reveal a cytological pattern very similar to that described for mammalian cells in a state of active protein synthesis. There is an elaborate development of particle-studded membranes in the cytoplasm. Smaller, rounded agranular vesicles also occur. The free secretory surface of the secreting cells forms the "end-apparatus" of the light microscopists. The invaginated surface is cast into numerous long narrow processes usually radially arranged and directed into a funnel-like formation derived from the thin intima lining the lumen of the gland (Text-fig. 2). The secretion in the form of small balls may be seen in the cavity of the end-apparatus and sometimes in the narrow processes. The small chitinogenic cells, lying between the protein-forming cells and the thin intima which they secrete, have a different cytology perhaps related to the fact that they form a polysaccharide rather than a protein. There is a very poor development of the particle-studded membranes of the type found in protein-forming cells. The type 2 cells, supposed to form an oxidase, have an end-apparatus that is similar to, but more complex than, those of the type 4 cells and their cytoplasm is almost completely filled with mitochondria. There is some evidence that mitochondria play a part in forming the oxidase and pass into the tubules of the end-apparatus. Type 3 cells resemble both types 2 and 4 and are probably a transient intermediate form.     

Ultrastructure of the digestive system of the Le fhopper Euscelidius variegatus Kirshbaum (Homoptera : Cicadellidae), with and without congenital bacterial infections

In the digestive system of Euscelidius variegatus Kirshbaum (Homoptera : (Cicadellidae), the close apposition of the anterior midgut with its posterior tabular midgut forms a filter chamber, which shunts excess water in the imbibed plant sap to the hindgut. Leafhoppers congenitally infected with a parasitic enteroform bacterium (designated BEV) had slightly atrophied digestive systems. There were numerous bacteria within the cells of the filter chamber, conical segment, and tubular midgut. Bacteria within the epithelium cells were usually enclosed within lysosomes. Epithelium cells swollen with large numbers of bacteria, had deteriorated cell membranes, and bacteria had erupted into the gut lumen. Leafhoppers not infected by BEV, harbored bacteria in the gut lumen, but not intracellularly within gut cells.     

Ultrastructure and development of the nephridia in Anaitides mucosa (Annelida,Polychaeta)

Different developmental stages (trochophores, nectochaetae, non-mature and mature adults) of Anaitides mucosa were investigated ultrastructurally. A. mucosa has protonephridia throughout its life; during maturity a ciliated funnel is attached to these organs. The protonephridial duct cells are multiciliated, while the terminal cells are monociliated. The single cilium is surrounded by 14 microvilli which extend into the duct lumen without coming into any contact with the duct cells. Corresponding ultrastructure and development indicate that larval and adult protonephridia are identical in A. mucosa. Differences between various developmental stages can be observed only in the number of cells per protonephridium. A comparison between the funnel cells, the cells of the coelothel and the duct cells reveals that the ciliated funnel is a derivative of the duct. Due to the identical nature of the larval and postlarval protonephridia, such a funnel cannot be a secondary structure. In comparison with the mesodermally derived metanephridial funnel in phoronids it seems likely that the metanephridia of annelids and phoronids evolved convergently.     

Fine structure of the rectal pads in Grylloblatta compodeiformis (walker) (Orthoptera : Grylloblattidae) with reference to fluid transport

The rectal pads of the primitive insect Grylloblatta compodeiformis (Orthoptera : Grylloblattidae) were studied using light and electron microscopy. In this species, the rectal epithelium is thickened to form 6 prominent rectal pads, each of which is composed of tall columnar epithelial cells and laterally placed slender junctional cells, but is devoid of secondary cells. The rectal pads are interconnected by simple rectal epithelium, and are lined by a thin cuticular intima. They are surrounded by an extensive connective tissue space, which contains bundles of delicate connective tissue fibers, neurosecretory axons, and tracheae and tracheoles, which do not penetrate into the pads. The epithelial cells exhibit extensive infoldings of the apical plasma membranes that are closely associated with mitochondria. The lateral membranes are also highly folded around large mitochondria that possess longitudinally oriented cristae. These membrane folds form mitochondrial-scalariform junctional complexes and enclose intercellular channels and spaces. The apical cytoplasm of the epithelial cells contains numerous coated vesicles, dense tubular elements, multivesicular bodies and lysosomes, which suggests receptor-mediated endocytosis of macromolecules. The presence of large whorls of rough endoplasmic reticulum and abundant free ribosomes in the cytoplasm and nuclei with multiple, well-developed nucleoli indicate that the epithelial cells are actively engaged in protein synthesis. The ultrastructural features were examined in relation to their role in fluid transport in a cold habitat.     

Evidence for a sugar receptor (lectin) in the peritrophic membrane of the blowfly larva, Calliphora erythrocephala Mg. (Diptera)

For the first time a sugar receptor (lectin) has been localized by electron microscopy in an invertebrate. The peritrophic membrane of the blowfly larva, Calliphora erythrocephala, is shown here to express lectins with high specificity for mannose. The lectin is restricted to the lumen side of the peritrophic membrane. The surface of the midgut epithelium is devoid of mannose-specific lectins. It is suggested that the midgut epithelium has lost these lectins during the course of evolution in favour of the peritrophic membrane which is secreted by specialized cells only at the beginning of the midgut.Peritrophic membranes and the midgut epithelium lack lectins specific for galactose. The lumen side of the peritrophic membrane of the larvae has mannose and/or glucose residues, and it is densely packed with two species of bacteria, Proteus vulgaris and P. morganii. These also have mannose-specific lectins as well as mannose residues on their pili. The existence of mannose-specific receptors and mannose residues on both, peritrophic membranes and bacteria, leads to the assumption of mutual adherence between the two surfaces.     

Biochemical activity and multiple locations of particulate guanylate cyclase in Rhyacophila dorsalis acutidens (Insecta: Trichoptera) provide insights into the cGMP signalling pathway in Malpighian tubules

In insect renal physiology, cGMP and cAMP have important regulatory roles. In Drosophila melanogaster, considered a good model for molecular physiology studies, and in other insects, cGMP and cAMP act as signalling molecules in the Malpighian tubules (MTs).However, many questions related to cyclic nucleotide functions are unsolved in principal cells (PC) and stellate cells (SC), the two cell types that compose the MT. In PC, despite the large body of information available on soluble guanylate cyclase (sGC) in the cGMP pathway, the functional circuit of particulate guanylate cyclase (pGC) remains obscure. In SC, on the other side, the synthesis and physiological role of the cGMP are still unknown. Our biochemical data regarding the presence of cyclic nucleotides in the MTs of Rhyacophila dorsalis acutidens revealed a cGMP level above the 50%, in comparison with the cAMP. The specific activity values for the membrane-bound guanylate cyclase were also recorded, implying that, besides the sGC, pGC is a physiologically relevant source of cGMP in MTs. Cytochemical studies showed ultrastructurally that there was a great deal of pGC on the basolateral membranes of both the principal and stellate cells. In addition, pGC was also detected in the contact zone between the two cell types and in the apical microvillar region of the stellate cells bordering the tubule lumen. The pGC signal is so well represented in PC and, unexpectedly in SC of MTs, that it is possible to hypothesize the existence of still uncharacterized physiological processes regulated by the pGC-cGMP system.     

Morphological and ultrastructural characterization of the alimentary canal in larvae of Streltzoviella insularis (Staudinger) (Lepidoptera: Cossidae)

Streltzoviella insularis (Staudinger) is an important tree‐boring pest, that primarily damages Sophora japonica (Linnaeus) and Ginkgo biloba (Linnaeus), as well as other common species, at great economic cost to the urban landscape construction industry in China. In the present study, the alimentary canal morphology of S. insularis was observed using light microscopy, and its ultrastructure was investigated by scanning and transmission electron microscopy. The foregut of S. insularis can be divided into the pharynx, esophagus, crop, proventriculus, and cardiac valve. The well‐developed crop forms the longest section of the foregut. It is able to store large amounts of food and is lined with a monolayer of epithelial cells. Many sclerotized microspines occur on the surface of the anterior intima and there are dense spines on the posterior intima of the proventriculus. Epithelial cells of the midgut include columnar cells, goblet cells, and regenerative cells, but endocrine cells are absent. The hindgut consists of the pyloric valve, ileum, and rectum. There is no clear distinction between the ileum and colon. The intima surface of the pyloric valve carries many microspines, whereas the intestinal wall of the rectum is thin with well‐developed rectal pads. The rectal epithelial cells form a squamous monolayer. A cryptonephric excretory system is located in the hindgut. There are six spiral Malpighian tubules, in which a cellular layer on a basement membrane encloses a lumen. These results will provide the basis for further studies of the structure and function in S. insularis larvae.     

Poly(3-Hydroxybutyrate) Granules at the Early Stages of Formation Are Localized Close to the Cytoplasmic Membrane in Caryophanon latum

Localization of newly synthesized poly(3hydroxybutyrate) (PHB) granules was determined by confocal laser scanning fluorescence microscopy of Nile red-stained cells and by transmission electron microscopy (TEM). PHB granules of Nile red-stained living cells of Caryophanon latum at the early stages of PHB accumulation were frequently found at or close to the cytoplasmic membrane. TEM analysis of the same culture revealed electron-translucent globular structures resembling PHB granules that were nonrandomly distributed in the cell lumen but were frequently found at or close to the cytoplasmic membrane. Immunogold labeling using PHB-specific antiserum confirmed that the electron-translucent structures represented PHB granules. Electron microscopy examination of PHB granules after cell lysis revealed that PHB granules were often associated with membrane vesicles. Nonrandom localization of PHB granules was also found in Beijerinckia indica. Cells of this species harbored one PHB granule at each cell pole. Our results show that newly synthesized PHB granules often are close to or even in physical contact with the cytoplasmic membrane. Possible explanations for this unexpected finding and a hypothetical model of PHB granule formation in C. latum are discussed.     

胡氏边白蚁消化系统的微细构造

胡氏边白蚁Marginitermes hubbardi(Banks)消化系统可分为前肠、中肠及后肠三大段.前肠包括葡萄状唾腺、口、咽喉、食道、前胃及贲门瓣;从贲门瓣开始到马氏管着生处为止这一段为中肠;后肠则分为葫芦形胃、结肠、直肠和肛门.其消化系统的特点:在前、后肠有几丁内膜、细胞层上还有一层微绒毛;上皮细胞底膜内陷很深,折叠中夹着许多线粒体;中肠围食膜表面有几丁层一直延伸到后肠;后肠前端膨大的葫芦胃中共生了很多种细菌及原生动物,共生的细菌、动物分泌纤维素酶帮助它消化木质纤维.     

THE ULTRASTRUCTURE OF THE SALT GLANDS OF CYNODON AND DISTICHLIS (POACEAE)

The epidermal salt glands of the grasses Cynodon and Distichlis consist of a small outer cap cell and a large, flask-shaped basal cell. The wall of the basal cell is contiguous with those of the adjacent epidermal cells and underlying mesophyll cells. The basal cell is connected symplastically with all adjoining cells via plasmodesmata. The outer, protruding portion of the glands is covered by a cuticle continuous with that of the adjoining epidermal cells. However, the lateral cell walls of the glands are not incrusted by this cuticle. The cap cell wall has a loose, mottled appearance quite different from the compact striated appearance of the basal cell wall. The cap cell is characterized by dense cytoplasm containing many organelles and a varying number of small vacuoles. The basal cell cytoplasm is distinguished by the presence of an intricate system of paired membranes that are closely associated with mitochondria and microtubules. These membranes are infoldings of the plasmalemma that originate adjacent to the wall separating the cap and basal cells. The space enclosed by the paired membranes, therefore, is an extracellular channel that is open only in the direction of secretory flow. The consistent orientation of this system of paired membranes suggests that it represents a structural specialization which is directly and functionally involved in the secretory process. The close association of mitochondria and microtubules with the paired membranes implies that these structures are also functionally related to the secretory process. Finally, the results of this study indicate that these glands are ultrastructurally similar to those of Spartina and that the glands of these three grasses are structurally distinct from those of dicotyledonous plants.     

CHANGES IN FINE STRUCTURE DURING SILK PROTEIN PRODUCTION IN THE AMPULLATE GLAND OF THE SPIDER ARANEUS SERICATUS

The ampullate silk gland of the spider, Araneus sericatus, produces the silk fiber for the scaffolding of the web. The fine structure of the various parts of the gland is described. The distal portion of the duct consist of a tube of epithelial cells which appear to secrete a substance which forms the tunica intima of the duct wall. At the proximal end of the duct there is a region of secretory cells. The epithelium of the sac portion contains five morphologically distinct types of granules. The bulk of the synthesis of silk occurs in the tail of the gland, and in this region only a single type of secretory droplet is seen in the epithelium. Protein synthesis can be stimulated by the injection of 1 mg/kg acetylcholine into the body fluids. 10 min after injection, much of the protein stored in the cytoplasm of the epithelial cells has been secreted into the lumen. 20 min after stimulation, the ergastoplasmic sacs form large whorls in the cytoplasm. Protein, similar in electron-opacity to protein found in the lumen, begins to form in that portion of the cytoplasm which is enclosed by the whorls. The limiting membrane of these droplets is formed by ergastoplasmic membranes which lose their ribosomes. No Golgi material has been found in these cells. Protein appears to be manufactured in the cytoplasm of the tail cells in a form which is ready for secretion.     

Dense granule-containing cells in arterial chemoreceptor areas of the tortoise (Testudo hermanni)

Light- and electron-microscopic observations of the chemosensory areas of the arteries of the tortoise (Testudo hermanni) reveal that clusters of nonmuscular cells are found in the adventitial layer of restricted regions of the carotid artery, aortic arch, and pulmonary artery. In these clusters, three types of cells are complexly interwoven: the G-cell closely resembles the glomus cell, which has been found in the arterial chemoreceptor area of several animal species; the LG-cell has very large electron-dense granules; the third type is a G- and LG-cell supporting cell. Membrane specializations are often observed at apposing membranes between G-cells. Two kinds of nerve endings synapse with G-cells, one with numerous clear synaptic vesicles, the other without vesicles. Some G-cells are in membrane-to-membrane contact with smooth-muscle cells (g-s connection), and here a membrane thickening is visible. Nerve terminals with numerous synaptic vesicles synapse with the LG-cells. The G-cell in the carotid artery, the aorta, and the pulmonary artery is a chemoreceptor element ultrastructurally the same as the glomus cell in the arterial chemoreceptor area of various vertebrate species.