The ultrastructure of the female accessory gland,the cement gland,in the insect Rhodnius prolixus

The cement gland of Rhodnius prolixus is an epidermally derived tubular gland consisting of a distal synthetic region and a proximal muscular duct region. The synthetic region consists of numerous secretory units joined to a central chitinous duct via cuticular ductules. Proteinaceous secretion, synthesized by the goblet-shaped secretory cell, passes through the delicate cuticular lattice of a ductule-end apparatus and out through fine ductules to the central duct. Secretory cells are rich in rough endoplasmic reticulum and mitochondria. Light microscopy, SEM and TEM reveal the delicate lattice-like end apparatus structure, its formation and relationship to the secretory cell. The secretory cell associates via septate junctions with a tubular ductule cell that encloses a cuticle-lined ductule by forming an elaborate septate junction with itself. The ductules are continuous with the cuticle lining of the large central duct that conveys secretion to the proximal area. The proximal muscular duct has a corrugated cuticular lining, a thin epithelium rich in microtubules and thick longitudinal, striated muscles which contract during oviposition, forcing the secretion out. Histochemistry and electrophoresis reveal the secretion as proteinaceous.     

Morphological evidence for a probable secretory site of the male sex pheromones of Nauphoeta cinerea (blattaria,blaberidae). 2. electron microscope studies

Light and electron microscopy of the glandular epithelium of intersegmental membranes between sternites three and seven and tergites two and eight of various age groups of Nauphoeta cinerea male adults and one age group of female adults discloses differences in the epithelia of the intersternite and intertergite. The intersternal epithelium appears thicker, more glandular, and stratified. Altogether, seven cell types are recognizable, six in the male and two in the female. They are designated as types 1, 2a, 2b, 2c, 3, 4, and 5. Of these, types 1, 2a, 3, and 4 are recognizable on the sternum; types 1, 2b, and 5 on the tergum of the mature male integuments. Types 1 and 2c are found on the sternum of mature female. The cell types undergo morphological differentiation after adult emergence and show different stages of secretory activity. Type 1 are squamous cuticle-secreting cells; type 2a, 2b, and 2c are columnar-glandular and contain electron-transparent secretory vesicles of various sizes, which increase greatly in number and size in the 5-day-old adult males when the glands are most active. The vesicular size and number also differ between types 2a, 2b, and 2c cells of the same age group. The vesicles are assumed to be derived from smooth endoplasmic reticulum. The type 2 gland cells are also provided with a secretory end apparatus lined by cuticle and bordered by microvilli through which the secretion is believed to be released by exocytosis. The end apparatus leads into a cuticular ductule that opens to the surface of the cuticle as a cup-shaped receptacle, which is more conspicuous in the male intersternite. In the active gland cells, the mitochondria near the end apparatus are swollen and vacuolated. Type 3 cells are seen only on the intersternum and are believed to secrete the cuticular ductule that proceeds from the end apparatus. Type 4 cells are also recognizable only on the male intersternum and contain closely packed, electron-dense bodies, which are most numerous in mature (5-day-old) males. Type 5 cells with their dense cytoplasm are located basally in the intertergal epithelium. The functional significance of type 4 and 5 cells in the males and type 2c cells in the female is not clear. On the basis of differences in morphology, pheromone activity, and sexual behavior, it is suggested that the pheromones secreted by the intersternal and intertergal glands in the male are different, the former secreting a seducin that attracts the female to the male and the latter an “aphrodisiac” acting as a contact pheromone important in accomplishing mating.     

Fine structure and metamorphosis of the wax gland cells in a psyllid insect,Anomoneura mori schwartz (Homoptera)

The fine structure of the wax gland of Anomoneura nymph and its metamorphic change were investigated. In the nymph, this organ encircles the anus, and consists of two kinds of cells, derived from epidermal cells: (1) very tall, slim wax cells, which produce and secrete the wax, and (2) flat interstitial cells found among the wax cells. The whole gland is covered by a wax-secreting cuticle with a delicate surface sculpture. Each wax cell has a long, wide duct which opens at the cuticle and penetrates the entire cell. Its cytoplasm is rich in mitochondria and smooth endoplasmic reticulum while that of interstitial cells contains rough endoplasmic reticulum. During each nymphal molt, the cluster of primordial wax gland cells — derived from the epidermis — proliferates rapidly and forms the gland of the next instar. The gland of the preceding instar meanwhile degenerates. Interstitial cells play an important role in cuticle formation and shedding at each molt. These cells alone produce and deposit the new cuticle of the next instar; the wax cells, specialized for wax production, cannot produce cuticle. The apical portion of the wax cell is cut off from the main cell body by growth of the surrounding interstitial cells. Thereafter, the wax cells degenerate, resulting in the rapid disappearance of the previous instar's wax gland. Adults lack this gland entirely.     

Morphology and ultrastructure of the Dufour gland in workers of social wasps (Hymenoptera, Vespidae)

The Dufour gland in workers of vespine wasps appears as an unpaired tubiform gland that opens in close proximity to the sting base. The epithelial cells that line the central reservoir are characterized by apical microvillus-like projections and deep basal invaginations. Their cytoplasm contains a well-developed Golgi apparatus, numerous mitochondria, as well as strands of smooth endoplasmic reticulum. The Dufour gland duct occurs ventrally to the venom gland duct, and bends downward near the sting base to open in the dorsal vaginal wall. In this region, the duct is dorsoventrally flattened, and shows conspicuous bundles of parallel microtubules in the epithelial cells, that transmit the pulling forces of the myofilaments of the underlying muscular supply to the cuticle. This results in an active opening mechanism regulated by muscular contraction, while passive closure probably results from the return of the cuticular intima to a rest position.     

Ultrastructural investigation of a salivary gland in a centipede: structure and origin of the maxilla I-gland of Scutigera coleoptrata (Chilopoda, Notostigmophora)

The maxilla I-gland of Scutigera coleoptrata was investigated using light and electron microscopy methods. This is the first ultrastructural investigation of a salivary gland in Chilopoda. The paired gland opens via the hypopharynx into the foregut and extends up to the third trunk segment. The gland is of irregular shape and consists of numerous acini consisting of several gland units. The secretion is released into an arborescent duct system. Each acinus consists of multiple of glandular units. The units are composed of three cell types: secretory cells, a single intermediary cell, and canal cells. The pear-shaped secretory cell is invaginated distally, forming an extracellular reservoir lined with microvilli, into which the secretion is released. The intermediary cell forms a conducting canal and connects the secretory cell with the canal cell. Proximally, the intermediary cell bears microvilli, whereas the distal part is covered with a distinct cuticle. The cuticle is a continuation of the cuticle of the canal cells. This investigation shows that the structure of the glandular units of the salivary maxilla I-gland is comparable to that of the glandular units of epidermal glands. Thus, it is likely that in Chilopoda salivary glands and epidermal glands share the same ground pattern. It is likely that in compound acinar glands a multiplication of secretory and duct cells has taken place, whereas the number of intermediary cells remains constant. The increase in the number of salivary acini leads to a shifting of the secretory elements away from the epidermis, deep into the head. Comparative investigations of the different head glands provide important characters for the reconstruction of myriapod phylogeny and the relationships of Myriapoda and Hexapoda.     

Fine structure of the Nassonow's gland in the neotenic endoparasitic of female Xenos vesparum (Rossi) (Strepsiptera, Insecta)

Nassonow's gland consists of a number of cells with ducts that open on to the ventral surface of the brood canal in the cephalothoracic region of a neotenic female strepsipteran. The structural organization of the gland is reminiscent of the class 3 of the epidermal gland cells as defined by Noirot and Quennedey [Ann. Rev. Entomol. 19 (1974) 61], which consists of secretory and duct forming cells. The ultrastructure of the Nassonow's gland is described in female Xenos vesparum (Rossi) parasitic in the social wasp Polistes dominulus Christ. The large secretory cells are clustered in groups of three to four, rich in smooth endoplasmic reticulum and produce a secretion made up of lipids. In young females, just before mating, the ultrastructure of the cells and their inclusions indicate that they are active. In old-mated females the Nassonow's gland degenerates. Microvilli line an extracellular cavity and there are pores present in the irregularly thick cuticle of the efferent duct. The small duct forming cells, intermingle with epidermal cells, overlap secretory cells and produce a long efferent duct, the cuticle of which becomes thick close to its opening in the brood canal. Nassonow's gland could be the source of a sex pheromone, which might be capable of attracting the free-living male to a permanently endoparasitic female.     

Ultrastructure of the epidermal maxilla II-gland of Scutigera coleoptrata (Chilopoda, Notostigmophora) and the ground pattern of epidermal gland organs in Myriapoda

The epidermal maxilla II-gland of Scutigera coleoptrata was investigated using light and electron microscopy. The glandular epithelium surrounds a spacious integumental cavity at the base of the maxilla II. The gland is formed as a compound gland organ that is composed of thousands of epidermal gland units. Each of them consists of four different cell types: a secretory cell, an accessory or intermediary cell, and a proximal and distal canal cell. The intermediary and the two canal cells form a conducting canal. Only in the most distal part of the intermediary cell is the canal lined by a cuticle. In the area of the two canal cells, the conducting canal is completely covered by a cuticle. The canal passes through the cuticle and opens into the spacious integumental cavity, which serves as a secretion reservoir. The structural organization of the epidermal maxilla II-gland was compared to that of other compound epidermal gland organs in Chilopoda and Diplopoda. All these glandular organs in Myriapoda share the same ground pattern.     

The Eltringham Organ and a New Thoracic Gland: Ultrastructure and Presumed Pheromone Function (Insecta, Myrmeleontidae)

Elofsson, R. and Löfqvist, J. (Zoological Institute, University of Lund, S-223 62 Lund, Sweden.) The Eltringham organ and a new thoracic gland: ultrastructure and presumed pheromone function . Zool. Scr. 3 (1): 31–40, 1974.—Eltringham's organ is a club-like projection from the posterior margin of hind-wings of some myrmeleontid insects. It bears laterally directed setae, each having a specialized epidermal cell beneath, which gives off secretion into a sub-setal lumen. The lumen continues into the wall of the moat-like socket of the setae. Eltringham's organ fits into an excavation of the lateral body wall connected with the opening of a thoracic gland. The thoracic gland in these animals has not previously been described. It consists of a hollow tube, feebly developed in females. The tube wall houses two cell types: gland cells and cuticular cells. The latter form the cuticle of the general duct lumen and a specialized duct leading from each gland cell. The gland cells have a microvilli-filled cavity which collects the secretion. The thoracic gland produces a pheromone secretion whose distribution is aided by Eltringham's organ where present.     

Ultrastructure of the male reproductive accessory glands in the medfly Ceratitis capitata (Diptera: Tephritidae) and preliminary characterization of their secretions

The morphology and the ultrastructure of the male accessory glands and ejaculatory duct of Ceratitis capitata were investigated. There are two types of glands in the reproductive apparatus. The first is a pair of long, mesoderm-derived tubules with binucleate, microvillate secretory cells, which contain smooth endoplasmic reticulum and, in the sexually mature males, enlarged polymorphic mitochondria. The narrow lumen of the gland is filled with dense or sometimes granulated secretion, containing lipids. The second type consists of short ectoderm-derived glands, finger-like or claviform shaped. Despite the different shape of these glands, after a cycle of maturation, their epithelial cells share a large subcuticular cavity filled with electron-transparent secretion. The ejaculatory duct, lined by cuticle, has epithelial cells with a limited involvement in secretory activity. Electrophoretic analysis of accessory gland secretion reveals different protein profiles for long tubular and short glands with bands of 16 and 10 kDa in both types of glands. We demonstrate that a large amount of accessory gland secretion is depleted from the glands after 30 min of copulation.     

白蜡虫雄性幼虫蜡腺的超微结构

在光镜结构研究的基础上,用电子显微镜观察了白蜡虫Ericerus pela Chavannes二龄雄幼虫蜡腺的超微结构和虫体表面的蜡孔及蜡丝形态。重点研究了蜡腺各组成部分的形态特点。     

Ultrastructure of the accessory gland in the parthenogenetic thrips heliothrips haemorrhoidalis (Bouché) (Thysanoptera : Thripidae)

The fine structure of the reproductive accessory gland of the parthenogenetic thrips Heliothrips haemorrhoidalis (Thysanoptera : Thripidae) is reported. It consists of an apical bulb and a fine gland duct. The former consists of an epithelium with secretory and duct-forming cells surrounding a large gland lumen lined with a thin cuticle and filled with dense secretion. Spent secretory cells degenerate and are eliminated from the epithelium. The gland duct is characterized by an irregular, branched lumen surrounded by a very flat epithelium. A valve controls the opening of the duct lumen. The proximal gland duct runs through a cuticular papilla that opens between the dorsal ovipositor valves. The secretions may serve for ovipositor valve lubrication and possibly to protect laid eggs. Observations of serial sections through the vagina exclude the presence of a spermatheca in this species.     

The subepithelial gland in ants: a novel exocrine gland closely associated with the cuticle surface

Two glandular systems were discovered that secrete their products onto the cuticular surface in ants. The first, the subepithelial gland, was previously undescribed in ants, and is found throughout the body just beneath the epithelium. This gland consists of independent secretory units, each made up of a single gland cell and an associated duct cell that penetrates the cuticle. Its ultrastructural appearance is consistent with possible hydrocarbon production. Examining 84 ant species, the subepithelial gland was found in eight subfamilies (out of 13), although not necessarily in all species. In a single ant species, Harpegnathos saltator, it was the epithelium itself that was enlarged and functioned as a gland. The enlarged epithelial cells secrete their products directly onto the cuticle through distinct cuticular crevasses.     

Ducts of the labral glands of Leptestheria dahalacensis (Crustacea: Branchiopoda: Spinicaudata)

Inside the labrum of Leptestheria dahalacensis are situated three types of large epidermal gland cells, whose ducts open onto the outer dorsal surface of the labrum. SEM revealed that the thin ducts of the A-type gland cells open out behind the epipharynx at the end of small, conically shaped protuberances, the two paired ducts of the B-type gland cells lead into the distal portion of the labrum, and the external opening of the single duct of the C-type gland cells lies on the dorsal lobe of the labrum. The ducts of the three different gland cell types have the same fundamental constitution, but vary in diameter. Each secretory unit consists of a pair of gland cells (A, B, or C) and a secretory duct. The duct is formed by ring-shaped folding of one anteroposteriorly elongated epidermal cell (duct cell), whose ends adhere closely to one another. A further ring-folded epidermal cell (accessory cell), but flattened in shape, is interposed, like a sleeve-connection, between the gland cells and the duct cell. The reservoirs of gland cells open into the lumen of the duct. Discontinuous deposits of highly electron-dense matter are present on the plasma membrane of the accessory cell delimiting the initial part of the duct lumen, while the plasma membrane of the duct cell facing the lumen is cuticularized. The cytoplasm of the accessory cell, on examination by TEM, appears quite similar to that of the duct cell, except for the different distribution and greater abundance of microtubules. Similarly organized tricellular tegumental glands also commonly occur in other Crustacea, both Malacostraca and non-Malacostraca. Possible functions of secretions from the three different types of gland cells present in the labrum of L. dahalacensis are discussed.     

Structure and function of the spermathecal complex in the phlebotomine sandflyPhlebotomus papatasi Scopoli (Diptera: Psychodidae): I. Ultrastructure and histology

Females of phlebotomine sandflies (Diptera: Psychodidae) possess highly variable spermathecae that present several important taxonomic characters. The cause of this diversity remains a neglected field of sandfly biology, but may possibly be due to female post-mating sexual selection. To understand this diversity, a detailed study of the structure and function of the spermathecal complex in at least one of the species was a prerequisite. Using scanning and transmission electron microscopy, described here is ultrastructure of the spermathecal complex in the sand fly,Phlebotomus papatasi Scopoli. The spermathecal complexes are paired; each consists of a long spermathecal duct, a cylindrical spermathecal body, and a spherical spermathecal gland. Muscle fibres, nerves, tracheoles, and vascular sinuses connect the spermathecal body and duct through the epithelial layers. Spermathecal gland is formed by a typical insect epidermis and consisting of an epithelial layer of class-1 epidermal cells and elaborate glandular cells of class-3 epidermal cells, each having both receiving and conducting ductules (i.e. “end apparatus”) and a “cytological apodeme”, which is a newly described cell structure. The spermathecal body and duct are lined by class-1 epidermal cells and a cuticle, and are enveloped by a super-contracting visceral muscular system. The cuticle consists of rubber-like resilin, and its fibrillar arrangement and chemical nature are described. A well-developed neuromuscular junction exists between the spermathecal gland and the spermathecal body, which are connected to each other by a nerve and a muscle. The spermathecal complexes of the sandfly are compared with those of other insect species. The physiological role and possible evolutionary significance of the different parts of spermathecal complex in the sandfly are inferred from the morphology and behaviour. Post-mating sexual selection may be responsible for the structural uniqueness of the spermathecal complex in phlebotomine sandflies.     

Morphological basis of cardiac glycoside sequestration by Oncopeltus fasciatus (Dallas) (Hemiptera: Lygaeidae)

Summary The integument of Oncopeltus fasciatus is made up of a vacuolated and a pigmented epidermal cell layer. This double layered integument is present from late embryo to adult in male and female animals reared on milkweed or sunflower seeds. Experiments with a labelled glycoside as well as retrograde ink injections suggest that O. fasciatus concentrates cardiac glycosides, normally derived from the host plants, within the vacuolated epidermal cell layer throughout its life cycle. In the adult, droplets of glycoside-rich fluid appear at precise points along the dorsolateral margins when external pressure is applied to the thorax and abdomen. This pressure causes separation of cuticular flanges in the metathoracic epimeral lobe and rupture of the cuticle in restricted areas in the mesothorax and abdomen. In addition the pigmented epidermal cell layer and the distal membranes of the vacuolated epidermal cell layer rupture with the result that the contents of the vacuolated cell layer are eliminated onto the surface of the animal where they are retained as discrete droplets by the cuticular morphology. Release of cardiac glycosides into the haemolymph is prevented by a thick basal lamina on the haemolymph side of the vacuolated epidermal cells. No specialized muscles involved with fluid release were observed. The vacuolated epidermal cells do not show ultrastructural features characteristic of actively transporting tissues, i.e., abundant mitochondria and elaborate membrane infoldings. This suggests that glycoside sequestration is essentially a passive process and should not be associated with any physiological cost. Large concentration gradients of cardiac glycosides are maintained across the basal lamina, basal plasma and vacuolar membranes of the vacuolated epidermal cell layer. Possible mechanisms by which O. fasciatus is able to concentrate cardiac glycosides as well as the possible function of this phenomenon are discussed.Abbreviations A abdominal trabeculum - Ap mesofurcal apodeme - C metathoracic supracoxal lobe - D metathoracic stink gland duct - E metathoracic epimeral lobe - Ep pigmented epidermal cell layer - Ev vacuolated epidermal cell layer - G last thoracic ganglion - H haemocoel - M midgut - N nerve cord - P second phragma - R reproductive organ - T trachea - V dorsal vessel - W wing - bl basal lamina - c cuticle - cf cytoplasmic fragments - cv coated vesicle - d hemidesmosome - ep epidermal cell - en endocuticle - ex exocuticle - f flange - fp foot processes - gc glycoside compartment - h hair - is intersegmental region - id ink deposits - l lumen of metathoracic stink gland - m mitochondria - mb mushroom bodies - mt microtrichia - n nucleus - p pigment granule - s slit - sp spine - tsm tergosternal muscle - v vacuole     

Ultrastructure of Gonionchus australis (Xyalidae,Nematoda)

Observations are reported on the ultrastructure of the buccal cavity, body cuticle, spermatids, spermatozoa, male genitalia, and caudal glands of Gonionchus australis. The buccal cuticle is a continuation of the pharyngeal cuticle. Anteriorly it is secreted by arcade tissue and overlaps the mouth rim; laterally it forms longitudinal tooth ridges. The non-annulated cephalic cuticle differs sharply from the remainder of the body wall cuticle. The cortical and basal zones become much thinner, while a largely structureless, lucent median zone expands to fill the bulk of the lips and lip flaps. Spermatids possess fibrous bodies, multimembrane organelles, mitochondria, and compact chromatin. The spermatozoa of G. australis resemble those of most other nematodes by the absence of the nuclear envelope and presence of fibrous bodies, mitochondria, and compact chromafin. The ejaculatory duct possesses microvilli. Two ejaculatory glands lie beside the duct. Two neurons are located within each spicule and each part of the paired gubernaculum. Caudal gland nuclei are large, with dispersed chromatin. The ducts of all three caudal glands are filled with secretory vesicles.     

An electron microscopic study of the spermathecal complex of virgin Aedes aegypti mosquitoes

Virgin mosquitoes were studied with the electron microscope. Spermathecal duct walls contain cuticle, epithelium, and a richly innervated spiral muscle; myocytes are linked by desmosome-like attachment plaques to the underlying epithelium. Periductal cells along upper portions of the ducts have a large secretory droplet within a highly irregular extracellular lacuna and are attached to a long secretory ductule through which finely granular material is delivered to the duct lumen and this enters the spermathecae. Basal gland cells of spermathecae have short ductules containing secretion in virgins. Secretory material in spermathecae of virgins does not form a complete internal membrane.     

Ultrastructural investigation of the vesicular glands in Scutigera coleoptrata (Chilopoda,Notostigmophora)

In the notostigmophoran centipedes, two pairs of vesicular glands have evolved. These paired glands are situated in the first and second trunk segment and open via cuticular ducts in the upper part of the particular pleura. The vesicular glands of Scutigera coleoptrata were investigated using light and, for the first time, electron microscopical methods. The glands consist of wide sac‐like cavities that often appear vesicular. The epithelia of both glands are identically structured and consist of numerous glandular units. Each of these units consists of four different cells: a single secretory cell, a small intermediary cell, and one proximal and one distal canal cell. The intermediary cell forms a conducting canal and connects the secretory cell with the canal cells. Proximally, the intermediary cell bears microvilli, whereas the distal part is covered with a distinct cuticle. The cuticle is a continuation of the cuticle of the canal cells. This investigation shows that the ultrastructure of glandular units of the vesicular glands is comparable to that of the glandular units of other epidermal glands in Chilopoda and Diplopoda, although the glands look completely different in the light microscope. Thus, it is likely that the vesicular glands and epidermal glands share the same ground pattern. With regard to specific differences in the cuticular lining of the intermediary cells, a common origin of epidermal glands in Myriapoda and Hexapoda is not supported. J. Morphol. 2009. © 2008 Wiley‐Liss, Inc.     

Anatomy and ultrastructure of the reproductive systems ofAcarus siro (Acari: Acaridae)

Anatomy and ultrastructure of the female and male reproductive system inAcarus siro L. were investigated by light and electron microscopy. The female system consists of paired ovaries of nutrimentary type in which oogonia and oocytes are connected by bridges with a large central cell. The oviducts empty into the uterus, which passes into preoviporal duct lined bycuticle, and opening as a longitudinal slit (oviporus). An elongated accessory gland composed of one type of secretory cell is located along each oviduct. The copulatory opening occurs at the posterior margin of the body and leads, via the inseminatory canal, to the receptaculum seminis, consisting of the basal and saccular part. Both inseminatory canal and basal part of receptaculum seminis are lined by cuticle, whereas the wall of the sac is formed by cells covered only by long, numerous microvilli. The basal part of the receptaculum seminis joins the ovaries via two lumenless transitory cones.The male reproductive system contains paired testes, in which spermatogonia tightly surround the central cell. The proximal part of the paired vasa deferentia serves as a sperm reservoir, while the distal one has a glandular character. An unpaired, cuticle-lined ejaculatory duct opens into the apex of the aedeagus. The single accessory gland is located asymmetrically at the level of, or slightly posterior to, coxae IV.The structure of the genital papillae, which are topographically related to the genital opening in both sexes, is also briefly described.     

The exocrine glands of the male of Eldana saccharina walker (Lepidoptera,galleriinae): Intervention in precopulatory behavior

The scent apparatus of male Eldana saccharina is a glandular complex on the costal area of the forewing. It consists of two parts; glandular complex 1 is composed of five kinds of cells (epidermal cells, scale cells, glandular cells, supporting cells, duct cells); glandular complex 2 also shows five types of cells (epidermal cells, scale cells, glandular cells, duct cells, trichogen cells). The secretory products of the two parts are discharged into separate ducts which converge before opening onto the lower side of the wing. The male also has two prominent hair-pencils borne on the coremata and large secretory trichogen cells on the genital valves. Each of these exocrine gland components plays an important part in formation of the chemically complex pheromones utilized in the precopulatory behavior of the male.