Morpho-functional comparison of the Dufour gland in the female castes of the Amazon ant <Emphasis Type="Italic">Polyergus rufescens</Emphasis> (Hymenoptera,Formicidae)

The Dufour gland is crucially involved in main aspects of the parasite habit of the slave-making ant Polyergus rufescens, i.e. slave-raids and host colony usurpation. Workers use chemicals from this gland as recruitment signals during raid organization, while newly-mated queens use its secretion to appease residents during host nest invasion. Here, we report a comparison of the general morphology and fine structure of the Dufour gland in the female castes of P. rufescens: queens, ergatogynes (intermediate forms), and workers. The analysis clearly shows the link between gland structure and its behavioural role in queens and workers. In particular, queens present a hypertrophied gland with an extended lumen and a thin epithelium no more active in secretory function. This is consistent with the fact that usurper queens use the Dufour gland contents only during the short phase of host nest penetration. Contrary to adult queens, the cytoplasmic organization of the Dufour gland epithelium of raiders is typical for a tissue with secretory activity (abundance of mitochondria, free ribosomes, strands of smooth endoplasmic reticulum and a Golgi apparatus). This is consistent with the continuous raiding activity performed by workers throughout their adult life. The biology of ergatogynes is still an enigmatic matter. Their Dufour gland is intermediate in shape and size between that of queens and workers. It presents a fairly thick epithelium with features that are typical of a quite active secretory tissue.     

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.     

Organization of unusual idiosomal glands in a water mite, <Emphasis Type="Italic">Teutonia cometes</Emphasis> (Teutoniidae)

The unusual idiosomal glands of a water mite Teutonia cometes (Koch 1837) were examined by means of transmission and scanning electron microscopy as well as on semi-thin sections. One pair of these glands is situated ventrally in the body cavity of the idiosoma. They run posteriorly from the terminal opening (distal end) on epimeres IV and gradually dilate to their proximal blind end. The terminal opening of each gland is armed with the two fine hair-like mechanoreceptive sensilla (‘pre-anal external’ setae). The proximal part of the glands is formed of columnar secretory epithelium with a voluminous central lumen containing a large single ‘globule’ of electron-dense secretory material. The secretory gland cells contain large nuclei and intensively developed rough endoplasmic reticulum. Secretory granules of Golgi origin are scattered throughout the cell volume in small groups and are discharged from the cells into the lumen between the scarce apical microvilli. The distal part of the glands is formed of another cell type that is not secretory. These cells are composed of narrow strips of the cytoplasm leaving the large intracellular vacuoles. A short excretory cuticular duct formed by special excretory duct cells connects the glands with the external medium. At the base of the terminal opening a cuticular funnel strengthens the gland termination. At the apex of this funnel a valve prevents back-flow of the extruded secretion. These glands, as other dermal glands of water mites, are thought to play a protective role and react to external stimuli with the help of the hair-like sensilla.     

Evidence for an exocrine function of theAplysia atrial gland

Summary The fact that the atrial gland ofAplysia californica contains peptides that will induce egg laying when injected into mature animals prompts consideration of the role played by the gland in the normal physiology of the animal. We have approached this consideration with a combination of morphologic and physiologic investigations. Morphologic study reveals the gland as a stratified epithelium comprised of three cell types. The only evidence for secretory activity was seen in the columnar epithelial cells containing large vesicular inclusions. These cells appear to discharge their secretory product into the lumen of the large hermaphroditic duct. While we cannot specify the contents of the secretion from the columnar cells, perfusate of the duct lumen contained bioassay active material only when the duct was exposed to depolarizing conditions. Though additional experiments in which exogenously administered atrial gland peptides were found to initiate egg laying in animals from which the source of the egg laying neurohormone had been extirpated, it appears likely that the atrial gland substances are not endocrine factors. Instead, their function must be sought among the exocrine products of the duct epithelium.Abbreviations FWS filtered artificial sea water - LHD large hermaphroditic duct Technical assistance for these studies was ably provided by Eugene Dannen and Gary Whitney. The surgical procedures were developed by Greg Thayer. Funding for the work was provided by NIH grant NS 11149 to S.A.     

Secretory and basal cells of the epithelium of the tubular glands in the male Mullerian gland of the caecilian Uraeotyphlus narayani (Amphibia: Gymnophiona)

Caecilians are exceptional among the vertebrates in that males retain the Mullerian duct as a functional glandular structure. The Mullerian gland on each side is formed from a large number of tubular glands connecting to a central duct, which either connects to the urogenital duct or opens directly into the cloaca. The Mullerian gland is believed to secrete a substance to be added to the sperm during ejaculation. Thus, the Mullerian gland could function as a male accessory reproductive gland. Recently, we described the male Mullerian gland of Uraeotyphlus narayani using light and transmission electron microscopy (TEM) and histochemistry. The present TEM study reports that the secretory cells of both the tubular and basal portions of the tubular glands of the male Mullerian gland of this caecilian produce secretion granules in the same manner as do other glandular epithelial cells. The secretion granules are released in the form of structured granules into the lumen of the tubular glands, and such granules are traceable to the lumen of the central duct of the Mullerian gland. This is comparable to the situation prevailing in the epididymal epithelium of several reptiles. In the secretory cells of the basal portion of the tubular glands, mitochondria are intimately associated with fabrication of the secretion granules. The structural and functional organization of the epithelium of the basal portion of the tubular glands is complicated by the presence of basal cells. This study suggests the origin of the basal cells from peritubular tissue leukocytes. The study also indicates a role for the basal cells in acquiring secretion granules from the neighboring secretory cells and processing them into lipofuscin material in the context of regression of the Mullerian gland during the period of reproductive quiescence. In these respects the basal cells match those in the epithelial lining of the epididymis of amniotes.     

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.     

Fine structural studies of rat seminal vesicle in castrated and intact animals following estrogen treatment.

The effect of estradiol and/or testosterone upon secretion by seminal vesicle in castrated and intact rats was assessed in young adult Sprague-Dawley rats, using light microscopy (LM), transmission (TEM) and scanning (SEM)electron microscopy. Hormones were injected daily for ten days beginning ten days after castrations were performed. The normal rat seminal vesicle, as revealed by SEM, was characterized by a large saccular lumen with highly folded walls. Cell surfaces were covered with microvilli, or occasionally displayed a protruding, ruffled surface, sparsely covered with short microvilli. Cytology was normal in testosterone-treated animals. Estradiol treatment of castrated animals stimulated secretion by seminal vesicle epithelial cells as evidenced by the presence of normal secretory bodies, the presence of RER, and moderately hypertrophied Golgi complexes. These glands were not heavier than were glands from castrated, untreated animals, although the epithelial cells were significantly taller. Secretion was maintained in intact animals treated with estradiol, although glands were smaller and epithelial height was reduced. Estradiol and testosterone treatment in combination did not appear to have an additive effect on secretion, weight of the gland, or epithelial height. The following results support the hypothesis that estrogen-induced prolactin synthesis and release may be involved in the mechanism by which estradiol effected stimulation of seminal vesicle epithelium. Prolactin-treated, castrated animals exhibited focal areas of stimulated epithelium. In hypophysectomized animals (untreated controls), the seminal vesicle epithelium retained some secretory bodies and secretory fluid in the glandular lumen; epithelial height was taller than that in castrated controls. Estrogen treatment reduced the epithelial height to that of castrated controls; there was no evidence of secretion. This suggests that in the absence of anterior pituitary hormones, including prolactin, the stimulatory effect of estradiol on seminal vesicle epithelium was nullified. In adrenalectomized/castrated animals, estradiol treatment stimulated secretion in seminal vesicle epithelium just as in non-adrenalectomized/castrated animals. This indicates that the adrenal gland plays a non-essential role in the action of estrogen on seminal vesicle epithelium.     

Early changes in the dog prostate after castration. An ultrastructural study

Using electron microscopic techniques the prostate glands of male Beagle dogs were studied 3 days after castration. At this time marked differences in the extent of alterations of the glandular epithelium were observed: Whereas several acini showed only minor changes with reduction of epithelial height and diminution of secretory granules, many acini were severely affected with pronounced alteration of cellular structure and accumulation of large lipid droplets. A constant feature was the stimulation of the basal cells of the grandular epithelium. Additionally, in some areas of the gland aggregations of stimulated basal cells forming an acinus-like structure with a slit-like lumen were found. Our study shows that castration leads to marked alterations of prostatic epithelium within a short time. Androgen deprivation causes regressive changes of secretory epithelial cells, but clearly stimulates the basal cell population.     

Fine structure of the spermatheca and of the accessory glands in Orchesella villosa (Collembola, Hexapoda)

The spermatheca and the accessory glands of the collembolan Orchesella villosa are described for the first time. Both organs exhibit ultrastructural differences, according to the time of the intermolt in which the specimens were observed. A thick cuticular layer lines the epithelial cells of the accessory glands. In the reproductive phase, they are involved in secretory activity; a moderately dense secretion found in the apical cell region opens into the gland lumen. Cells with an extracellular cistern are intermingled with the secretory cells. These cells could be involved in fluid secretion, with the secretory product opening into the cistern which is filled with an electron-transparent material. After the reproductive phase, the gland lumen becomes filled with a dense secretion. The accessory gland secretion may play a protective role towards the eggs. The spermatheca is located between the accessory glands; its epithelium is lined by a thin cuticle forming spine-like projections into the lumen and consists of cells provided with an extracellular cistern. Secretory cells, similar to those seen in the accessory glands, are missing. Cells with a cistern could be involved in the production of a fluid secretion determining sperm unrolling and sperm motility.     

The Ultrastructure of the Gastrodermal Gland Cells in the Freshwater Planarian Dugesia gonocephala s.l.

Light and transmission electron microscopy have been used to study the gastrodermal gland cells of the triclad Dugesia gonocephala s.l. The events involved in the ultrastructural transformation and the secretion process in these cells were followed at four different stages in both fasted and fed animals. During the feeding stage their secretory granules are directly discharged into the intestinal lumen by means of a secretion process of the holocrine type that is described in this paper. It is suggested that such secretions contribute to extracellular digestion and that disintegration of the gland cells is accompanied by a differentiation of neoblasts into new gland cells, reflecting a turnover of gland cells during the triclad digestive stages.     

Functional morphology of the mammiliform penial glands ofLittorina saxatilis (Gastropoda)

Summary The functional morphology of the mammiliform penial glands ofLittorina saxatilis has been investigated with both light and electron microscopy. These penial glands line the ventral edge of the penis and orient with the female mantle during copulation. Secretions are released from the penial glands to this interface where they probably function in adhesion. The penial gland secretions comprise heterogeneous granules as well as apocrine and mucous secretions. The heterogeneous granules are produced in separate multicellular glands arranged in a series of lobes that lie outside a thick smooth muscle layer enclosing the lumen. Each glandular lobe is surrounded by a thin layer of smooth muscle. Secretions are transported in individual cellular processes that pass through the thick smooth muscle layer and empty into the lumen. Surrounding the lumen is an epithelium containing apocrine secretory cells as well as occasional goblet-type, mucous cells. The combined action of the muscles forces secretions out of the lumen through the penial papilla, onto the external surface of the mammiliform penial gland. Longitudinal muscles extend into the penial papilla enabling its protrusion or retraction. Retraction of the penial papilla following secretion release is thought to create negative pressure beneath the penial gland producing suction adhesion. The visco-elastic properties of the penial gland secretion are qualitatively different from foot mucus and may represent specialization to an adhesive function.     

Structural simplicity of theZonula Occludens in the electrolyte secreting epithelium of the avian salt gland

Summary The structure of thezonula occludens in the secretory epithelium of the salt gland of the domestic duck was determined by thin section and freeze-fracture electron microscopy. These glands secrete an effluent with a NaCl concentration four times that of plasma, and thus maintain a steep ionic gradient across their secretory epithelium. Freezefracture replicas from salt stressed ducks demonstrate that thezonula occludens is surprisingly shallow in depth (20–25 nm) and generally consists of two parallel junctional strands which are juxaposed along their entire length. In addition to the simplicity of the junction separating mucosal and serosal compartments, the ratio of junctional length to apical surface area is large since luminal surfaces of secretory cells are narrow and intermesh with one another. Thezonula occludens in nonsecreting fresh water-adapted birds is similar to the salt stressed group except that two sets of double strand junctions are seen in addition to junctions consisting of a single set. Based on previous ultrastructural, cytochemical and physiological studies in salt glands and in other epithelia, a model for salt secretion was suggested in which intercellular space Na⁺, generated by basolateral ouabain-sensitive Na⁺ pumps, reaches the lumen via a paracellular route (Ernst & Mills, 1977,J. Cell Biol. 75:74). The simplicity of the morphological appearance of thezonula occludens in the salt gland, which resembles that described for several epithelia known to be leaky to ions, is consistent with this hypothesis.     

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.     

Morphology and histology of secretory setae in terrestrial larvae of biting midges of the genus Forcipomyia (Diptera: Ceratopogonidae)

Apneustic larvae of the genus Forcipomyia possess unique secretory setae located on the dorsal surface along the body in two rows, one pair on each thoracic and abdominal segment and two pairs on the head. Morphological and histological studies of secretory setae in fourth instar larvae of Forcipomyia nigra (Winnertz) and Forcipomyia nigrans Remm indicate they are modified mechanoreceptors (sensilla trichodea) in which the trichogen cell is a glandular cell producing a hygroscopic secretion. The cytoplasm of the glandular trichogen cell fills the lumen of a secretory seta, which shows one or more pores on the apex. The cytoplasm contains numerous microtubules responsible for transportation of proteinaceous vesicles, and an extremely large polyploid nucleus typical of gland cells. The main role of the hygroscopic secretion is to moist the body and thus facilitate cuticular respiration.     

Morphological changes in the male accessory glands and testes in Vespula vulgaris (Hymenoptera,Vespidae) during sexual maturation

Abstract. The present study documents the pace of accessory gland and testes degeneration in the wasp Vespula vulgaris by means of a histological and metric approach, that has not been carried out for social wasps so far. To a certain extent, comparison is made with the degenerative processes of the mucus glands of the honeybee drone. In V. vulgaris, no generative tissue is left by the end of 9 d of age, and so degeneration is a fast process. The three different parts of the accessory glands (muscle layer, gland epithelium, and lumen) change with respect to age. The secretory cells of the epithelium reach their maximum activity during the first days of adult life, which results in a maximally filled gland lumen by 9 d. We also provide, for the first time, a histological study of testes degeneration for this species. At eclosion, well‐defined cystic structures are still visible, whereas at 9 d, it is no longer possible to distinguish different cystic structures. The diameter of the testes decreases with respect to age.     

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.     

Dufour gland of the digger wasp<Emphasis Type="Italic"> Liris niger:</Emphasis> structure and developmental and biochemical aspects

The tubiform Dufour gland in the digger wasp species Liris niger is about 1.0 mm long ( 0.15 mm). An alternating arrangement of longitudinal and circumferential bundles of striated muscle fibers surrounds the gland. The Dufour gland, together with the venom gland, enters the sting base and terminates in the sting. The glandular epithelium is monolayered. Glands about 3 day after imaginal ecdysis have an empty lumen but a thick lining epithelium. The gland cells are characterized by a well-developed vesicular smooth endoplasmic reticulum, sparse rough ER and numerous free ribosomes. They also exhibit several electron-lucent vesicles and autophagic vacuoles. Secretion of electron-dense material via the gland cuticle into the gland lumen is apparent. Glands more than 20 days after imaginal ecdysis display a large lumen and a thin epithelium. The cells show signs of degeneration with numerous cytolytic inclusions. Dufour gland liquid contains numerous polypeptides of molecular weights ranging from 14 to about 200 kDa. In addition the secretion consists predominantly of straight-chain hydrocarbons, accompanied by small amounts of esters. The major hydrocarbons are pentadecane and (Z)-8-heptadecene. Dufour gland secretion may have several functions: (1) the polypeptides might be involved in the gluing process of the eggs, while (2) the hydrocarbon oils may function as lubricants for the lancets and (3) might soften the secretion, thus allowing easier application of the glue. The lipophilic volatile material (4) might also be involved in pheromonal signaling.     

Functional morphology and neuronal innervation of the prothoracic defence gland in Timema

Timema is the most basal genus of Phasmatodea and the sister group to the remaining stick and leaf-insects (Euphasmatodea). An autapomorphy of all phasmids is the paired prothoracic exocrine defence glands. In this study, the anatomy and innervation of the defence glands in Timema petita and Timema chumash are described and compared with the data on Euphasmatodea. In all phasmids, the glands consist of a cuticular epithelium, a secretory epithelium and muscular fibres that compress the lumen. In Timematodea, the muscular part of the gland is less developed than in Euphasmatodea and the ejection of the defence secretion depends on the dorsal longitudinal neck muscles. On the neuroanatomical level, Timema petita and Timema chumash lack neurons that are involved in the independent contraction of the gland in euphasmids. In both studied species of Timema, neck muscles play an active role in the gland function which is not observed in any other phasmid. Considering the basal position of this genus, this supports the hypothesis that in euphasmids, the muscular part of the gland evolved from the dorsal longitudinal neck muscles. Additionally, the same nerves that innervate the dorsal longitudinal neck muscles in all Polyneoptera also innervate the defence glands in phasmids.     

Ultrastructure and nature of secretory proteins in the male accessory gland of Drosophila funebris

The ultrastructural differentiation of the secretory cells and the nature of secretory proteins in the male accessory gland of Drosophila funebris have been studied by electron-microscopic and immunological methods. (1) In the pupae at $\text{1}\text{1}\text{2}$ days before eclosion, secretory products can be detected in the lumen, even though most glandular cells are at the initial phase of differentiation. At the time of eclosion both main and secondary cells are fully differentiated, but the whole set of five immunologically active proteins are detectable only on the second to third day of adult life. (2) The secondary cells contain giant protein granules, the so-called filamentous bodies, which become partially fused and the filaments assume a twisted form. Randomly dispersed filaments and closely packed filament bundles are also visible in the gland lumen. Antigenic labelling of ultrathin sections and immunoreplica electrophoresis yielded no evidence for the microtubular nature of these filaments. The secretion stored in the lumen contains in addition a large quantity of flocculent proteins which have their origin in the main cells. (3) During the period of high secretory activity in the 7-day-old male flies no vacuolization and disintegration of either the main or secondary cells have been observed. We conclude that both types of cells have the merocrine secretory mechanism. (4) Ultrastructural alterations in the glandular cells confirmed our previous observation that copulation stimulates RNA and protein synthesis.     

Functional morphology of the postpharyngeal gland of queens and workers of the ant Monomorium pharaonis (L.)

Eelen D., Børgesen L.W. and Billen J. 2006. Functional morphology of the postpharyngeal gland of queens and workers of the ant Monomorium pharaonis (L.). —Acta Zoologica (Stockholm) 87 : 101–111 The postpharyngeal gland (PPG) is unique to ants and is the largest exocrine gland in their head. In queens of the pharaoh's ant, Monomorium pharaonis, the gland contains approximately 15 finger‐like epithelial extensions on each side and opens dorsolaterally in the posterior pharynx. In these ants the PPG morphology varies considerably according to age and mating status. The epithelial thickness increases with age and reaches a maximum at 3 weeks in both virgin and mated queens. A considerable expansion of the lumen diameter occurs in both groups between 4 and 7 days. Virgin queens release their secretion into the gland lumen from an age of 7 days, whereas mated queens accumulate large amounts of secretion in their epithelium. The increasing epithelial thickness, together with the increasing lumen diameter, the presence of numerous inclusions in the epithelium and the release of secretion, are indicative for increasing gland activity. The gland ultrastructure indicates involvement in lipid metabolism and de novo synthesis of lipids. The PPG of workers consists of 12 finger‐like tubes at each side. There is a significant difference in epithelial thickness between nurses and repletes and between nurses and foragers. We suggest the PPG serves different purposes in pharaoh's ants: it is likely that the PPG of workers and virgin queens is used to feed larvae. In mated queens the gland probably plays a role in providing the queen with nutritious oils for egg production. The PPG may also function in signalling species nestmate and caste identity, as well as in the reproductive capacity of the queens.