Development of the accessory reproductive glands and genital ducts in female Schistocerca gregaria

The accessory reproductive glands of female S. gregaria are tubular extensions of the paired genital ducts, which in the mature female contain large amounts of a proteinaceous secretion used in the formation of the egg pod. In the 4th and 5th-instar female the glands are indistinguishable from the remainder of the mesodermally derived genital ducts. Towards the end of the 5th stadium, however, the accessory gland region only acquires characteristic convolutions which persist throughout the adult stages. At this time the epithelium of the entire ducts becomes reorganized into a unicellular epithelium. Only one cell type occurs throughout the length of the glands, and also in the egg calyces and lateral oviducts. The cells are inactive immediately after final ecdysis and remain in this state until the level of juvenile hormone in the haemolymph rises. The hormone acts directly on the cells triggering a rapid proliferation of organelles associated with protein secretion, and thereby increasing the volume of apical cytoplasm. Microvilli develop at the luminar plasma membrane, while irregular infoldings form at the base of the cells. As the gland matures the major organelle, the rough endoplasmic reticulum, changes from the lamellar to the vesicular form. Secretion is released into the lumen by the ‘microapocrine’ method.     

Histochemical analysis of accessory genital gland secretions in female Pimpla turionellae L. (Hymenoptera: Ichneumonidae)

The secretions produced by the 3 accessory glands of the female genital tract of Pimpla turionellae were investigated histochemically. The uterus gland secretion was identified as a mixture of hyaluronic acid and lipoprotein, that of the poison gland as a neutral mucoprotein. The product of the alkaline gland (Dufour's gland) consists of lecithin and a cholesterol ester. Pimpla females, as parasites of Lepidoptera pupae, inject these secretions into the host hemocoel during oviposition, thus preventing hemocytic encapsulation of their eggs. The physiological functions of the secretions are briefly discussed.     

Structure of the male reproductive accessory glands of Pterostichus nigrita (Coleoptera: Carabidae), their role in spermatophore formation

Accessory gland secretions of male insects have many important functions including the formation of spermatophores. We used light and electron microscopy to investigate the structure of the accessory glands and posterior vasa deferentia of the carabid beetle Pterostichus nigrita to try to determine where spermatophore material is produced. Each accessory gland and posterior vas deferens had an outer layer of longitudinal muscle, beneath which was a layer of connective tissue and a thin band of circular muscle, all of which surrounded a layer of epithelial cells lining the lumen of the ducts. Based on the ultrastructure of the epithelial cells, and their secretory products, we identified two epithelial cell types in each region (distal and proximal) of the accessory glands and four types in the posterior vas deferens. Most secretory products, which stained positively for proteins and some mucins, were released into the lumen of the ducts by apocrine secretion. The accessory glands produced one type of secretory product whereas in posterior vasa deferentia, four types of secretory products were found layered in the lumen. Our results suggest that most of the structural material used to construct a spermatophore is produced by the cells of the posterior vasa deferentia.     

Honey bee males and queens use glandular secretions to enhance sperm viability before and after storage

Internal fertilization requires live sperm to be transferred from male to female before egg fertilization. Both males and females assist the insemination process by providing sperm with glandular secretions, which have been inferred to contain subsets of proteins that maintain sperm viability. Here we show that in the honeybee (Apis mellifera) secretions of the male accessory glands, the major contributors towards seminal fluid, enhance sperm survival. We further demonstrate that the protein fraction of the male accessory gland secretion is indeed important for achieving the maximal effect on sperm survival. After sperm storage, the queens also provide sperm with secretions from spermathecal glands and we show that these secretions have a comparable positive effect on sperm viability. SDS gels show that the proteomic profiles of accessory gland secretion and spermathecal fluid secretion hardly overlap, which suggests that males and females use different proteins to enhance sperm viability during, respectively, ejaculation and final sperm storage.     

A histological and ultrastructural comparison of the male accessory reproductive glands of diapausing and non-diapausing adults in Bruchidius atrolineatus (Pic) (Coleoptera : Bruchidae)

Cytological variations of the median and the 2 lateral accessory glands of Bruchidius atrolineatus Pic (Coleoptera : Bruchidae) were examined as a function of age and the reproduction of the male. In sexually active virgin males, the secretory epithelium is columnar at emergence, but progressively flattens, and the secretions formed and stored by its cells are expelled by exocytosis into the glandular lumen. After 10 days, the male accessory glands exhibit a stage of repletion, characteristic of glands temporarily storing their secretions in their lumen. In diapausing males, the genital tract is relatively undeveloped and the accessory glands are reduced to tubules, whose lumen, surrounded by an epithelium composed of narrow cells, contains little secreted material. The presence of secretion aggregates in the secretory epithelial cells, the abundance of rough endoplasmic reticulum in them, and the release of a part of their secretions into the glandular lumen, indicate that reproductive diapause in B. atrolineatus is characterized by a decrease in the reproductive function. and not its total arrest.     

Ultrastructure of the tubular accessory gland in Haemaphysalis longicornis (Acari: Ixodidae)

The paired tubular accessory glands in Haemaphysalis longicornis open at the junction of the cervical and the vestibular parts of vagina via short and narrow ducts. The pseudostratified columnar glandular epithelium covered by the muscle layer consists of both secretory and supporting cells. As feeding proceeds, the secretory cells increase in volume. In ovipositing females, well-developed rough endoplasmic reticulum, the Golgi complex, and membranebound granules that are undergoing exocytosis suggest that the secretory cells are involved in protein synthesis. However, in virgin females that fed 10 days, only small dense granules and no secretion activity were observed. The secretions from the tubular accessory gland may be released into the genital tract during the egg passage through the vagina. However, the supporting cells located between the secretory cells become slender during feeding, cohere to each other at the luminal side, and have a very narrow attachment at the basement membrane. Supporting cells probably help maintain secretory cell shape especially during granular discharge into the lumen. © 1994 Wiley-Liss, Inc.     

Transglutaminase-Mediated Semen Coagulation Controls Sperm Storage in the Malaria Mosquito

Insect seminal fluid proteins are powerful modulators of many aspects of female physiology and behaviour including longevity, egg production, sperm storage, and remating. The crucial role of these proteins in reproduction makes them promising targets for developing tools aimed at reducing the population sizes of vectors of disease. In the malaria mosquito Anopheles gambiae, seminal secretions produced by the male accessory glands (MAGs) are transferred to females in the form of a coagulated mass called the mating plug. The potential of seminal fluid proteins as tools for mosquito control demands that we improve our limited understanding of the composition and function of the plug. Here, we show that the plug is a key determinant of An. gambiae reproductive success. We uncover the composition of the plug and demonstrate it is formed through the cross-linking of seminal proteins mediated by a MAG-specific transglutaminase (TGase), a mechanism remarkably similar to mammalian semen coagulation. Interfering with TGase expression in males inhibits plug formation and transfer, and prevents females from storing sperm with obvious consequences for fertility. Moreover, we show that the MAG-specific TGase is restricted to the anopheline lineage, where it functions to promote sperm storage rather than as a mechanical barrier to re-insemination. Taken together, these data represent a major advance in our understanding of the factors shaping Anopheles reproductive biology.     

Age-dependent changes in ultrastructure of the defensive glands of Neocapritermes taracua workers (Isoptera,Termitidae)

Protection against predators and competitors is one of the main concerns of termite colonies, which developed a specialised defensive caste, the soldiers. However, soldiers are rare or even missing in several lineages of termites, while workers often develop new defence strategies especially in soil-feeding species. Here, we describe the morphology and ultrastructure of the autothysis-associated glands of Neocapritermes taracua workers and report their age-related changes in structure. The defensive glands of N. taracua workers consist of a pair of labial and a pair of crystal glands, whose secretions mix together through autothysis. Autothysis always occurs at the line of weakness connecting the anterior parts of the crystal-bearing pouches. The crystal glands consist of groups of bicellular secretory units (secretory and corresponding canal cells) which secrete the blue crystal material into external pouches. Their secretory activity is maximal in the middle of worker life, and is considerably lower in very young and old workers. The labial glands are composed of two types of secretory cells: the central and the parietal cells. While the central cells are developed similarly to other termites and secrete proteinaceous secretion into labial gland ducts, the parietal cells develop proteinaceous granules which may eventually bud off the cells. The secretory function of parietal cells is so far unique to N. taracua and differs from other termite species in which they are only responsible of water uptake by acini. The defensive device of N. taracua is truly exceptional as it involves a new gland and a previously undescribed function for parietal cells, being a remarkable example of evolution of morphological innovation.     

Spermatophore formation in the pseudoscorpion Chthonius ischnocheles (Chthoniidae)

The reproduction of pseudoscorpions involves indirect sperm transfer by means of spermatophores. The spermatophores are the product of the male genital atrium. A functional interpretation of spermatophore formation in Chthonius ischnocheles is based on evidence from (a) a morphological study of the genital atrium, the associated accessory glands and the musculature (b) males sectioned during spermatophore production (c) histochemical tests on the glands and their secretions (d) biochemical analyses of one gland (posterior dorsal) and its secretion (e) the behaviour of males during this process and (f) the structure of the spermatophore.
The anterior region of the genital atrium is concerned with the production of the sperm packet. The encysted sperm and the seminal fluid from the prostatic reservoir are encapsulated in a sperm packet by a secretion from two pairs of anterior glands. The posterior region of the genital atrium is responsible for the formation of the spermatophore stalk and its distal elaboration, the two lateral collars. These parts of the spermatophore arise from the fibroin secretion of the posterior dorsal gland; the shape of the spermatophore collars is correlated with their mould, the medial diverticula. In addition the lateral glands secrete a light oil which accumulates on a thickening of the spermatophore stalk proximal to the collars. This suggested that this secretion acts as a pheromone to attract females to the spermatophore since in this species males produce their spermatophores in the absence of females.     

Accumulation of secretory proteins in the accessory reproductive glands of the male migratory grasshopper, Melanoplus sanguinipes: A developmental study

Production of secretion in the accessory reproductive glands of male Melanoplus sanguinipes has been examined by electrophoresis and radiolabelling. The secretion of each group of tubules (long hyaline glands, white glands, short hyaline glands, and seminal vesicles) can be resolved into more than 20 protein bands and includes several glycoproteins and, in the long hyaline and white glands only, lipoproteins. Each group of tubules has a characteristic pattern of synthesis and accumulation of proteins; that is, specific proteins appear in the secretion at particular times during sexual maturation. In allatectomized insects, the long hyaline glands accumulate very little secretion; the white glands and short hyaline glands accumulate about one-third the normal amount; and accumulation in the seminal vesicles is not affected by the operation. Allatectomy exerts its effect by inhibiting the synthesis of particular proteins. The observations are discussed in terms of juvenile hormone-specific protein synthesis in the accessory reproductive glands.     

Transfer and fate of male secretions deposited in the spermatophore of females of Acanthoscelides obtectus Say (Coleoptera Bruchidae)

During mating, males of Acanthoscelides obtectus deposit a spermatophore in the female genital tract. Spermatophore structure subsequently undergoes considerable modification, especially the central portion, which becomes vacuolated. Two methods were used to show that certain male secretions could thus pass into female haemolymph. When young males were injected with [¹⁴C]-arginine or [¹⁴C]-histidine, the accessory glands actively incorporated the isotope and the resulting spermatophores were radioactive. After mating, spermatophore radioactivity declined and then appeared in the haemolymph of females and in the oöcytes after a delay. Immunoelectrophoresis also showed that antigens appeared in the haemolymph of females after mating which reacted against male-gland antiserum. This technique, however, did not enable us to detect the presence of male antigens in the oöcytes formed after mating. The fate of some male secretions in the female and their physiological importance in the control of the female reproductive function were analysed in the present work.     

S-Adenosylmethionine:Juvenile hormone acid methyltransferase in male accessory reproductive glands of Hyalophora cecropia (L.)

The accessory reproductive glands of the adult male Hyalophora cecropia contain S-adenosylmethionine:juvenile hormone acid methyltransferase. The enzyme is soluble and can be found in the gland epithelium as well as in the glandular secretion, but not in any other part of the genital tract of the unmated male. The appearance of this enzyme activity in the pharate adult precedes the formation of a measurable pool of its substrate, juvenile hormone acid, and the onset of the juvenile hormone accumulation in the accessory reproductive glands. The accessory reproductive glands of Antherea pernyi and Manduca sexta, species which do not accumulate juvenile hormone, lack methyltransferase activity. It is concluded that the methyltransferase is an essential component of the juvenile hormone accumulation mechanism in H. cecropia.     

Fine structure of the integumental glands of a termite soldier

The ultrastructure of some integumental glands occurring in the head, thorax and abdomen of K. flavicollis soldiers is described. The secretory units consist of two cells, the canal cell and the secretory cell (this latter filled with secretion granules). A cylindrical and distorted extracellular space, or reservoir, with an irregular outline is lined by short microvilli. The end-apparatus is made up of small overlapping cuticular laminae which in section resemble small wavy rods. The ample distribution of the units has led the authors to consider them dermal glands. Scanning electron micrographs confirm that the glands' activity consists in the secretion of material which then spreads over the surface of the integument. The dissimilar appearance of the secretion granules present in glands of different soldiers suggests that the electron-lucid granules and the granules with fibrils are two completely different secretions at different ages of the animal. The authors do not therefore rule out the hypothesis that these integumental glands may later produce or release pheromones.     

Ultrastructure of the accessory glands of gene's organ in the cattle tick, Boophilus

The organization and ultrastructure of the accessory glands of the cattle tick, Boophilus microplus, are described. The glands consist of two groups of acinar cells situated on either side of Gene's organ. A single acinus consists of from eight to 12 cells and each cell is connected via an individual duct to pores on the dorsal surface of the mouthparts. The position of these pores is such that the secretion of the accessory glands is incorporated into the egg wax during oviposition. Each gland cell has striking quantities of smooth endoplasmic reticulum and numerous Golgi dictyosomes and appears to produce a secretion that is lipoidal in nature. Each cell secretes into its own individual lumen and is connected to a cuticular pore by a duct cell.     

Ultrastructure and function of the seminal vesicle of Bittacidae (Insecta: Mecoptera)

The fine structure of the seminal vesicle and reproductive accessory glands was investigated in Bittacidae of Mecoptera using light and transmission electron microscopy. The male reproductive system of Bittacidae mainly consists of a pair of testes, a pair of vasa deferentia, and an ejaculatory sac. The vas deferens is greatly expanded for its middle and medio-posterior parts to form a well-developed seminal vesicle. The seminal vesicle is composed of layers of developed muscles and a mono-layered epithelium surrounding the small central lumen. The epithelium is rich in rough endoplasmic reticulum and mitochondria, and secretes vesicles and granules into the central lumen by merocrine mechanisms. A pair of elongate mesodermal accessory glands opens into the lateral side of the seminal vesicles. The accessory glands are similar to the seminal vesicle in structure, also consisting of layers of muscle fibres and a mono-layered elongated epithelium, the cells of which contain numerous cisterns of rough endoplasmic reticulum and mitochondria, and a few Golgi complexes. The epithelial cells of accessory glands extrude secretions via apocrine and merocrine processes. The seminal vesicles mainly serve the function of secretion rather than temporarily storing spermatozoa. The sperm instead are temporarily stored in the epididymis, the greatly coiled distal portion of the vas deferens.     

Structure of male accessory glands of Bolivarius siculus (fischer) (Orthoptera,Tettigoniidae) and protein analysis of their secretions

In Tettigoniidae (Orthoptera), male reproductive accessory glands are involved in the construction of a two‐part spermatophore; one part, the spermatophylax, is devoid of sperm and considered a nuptial gift. The morphology, ultrastructure, and secretion protein content of the male reproductive accessory glands from Bolivarius siculus were investigated. Two main groups of gland tubules open into the ejaculatory duct: the “first‐order” glands, a number of large anterior tubules, and the “second‐order” glands, smaller and more numerous tubules positioned posteriorly. Along with a further subdivision of the gland tubules, we here describe for the first time an additional gland group, the intermediate tubules, which open between first and second‐order glands. The mesoderm‐derived epithelium of all glands is a single layer of microvillated cells, which can be either flattened or cylindric in the proximal or distal region of the same gland. Epithelial cells, very rich in RER and Golgi systems, produce secretions of both electron‐dense granules and globules or electron‐transparent material, discharged into the gland lumen by apocrine or merocrine mechanisms, respectively. With one exception, a unique electrophoresis protein profile was displayed by each of the gland types, paralleling their unique morphologies. To assess the contribution of different types of accessory glands to the construction of the spermatophore, the protein patterns of the gland secretions were compared with those of the extracts from the two parts of the spermatophore. All samples showed bands distributed in a wide range of molecular weight, including proteins of very low molecular mass. However, one major high molecular weight protein band (>180 kDa) is seen exclusively in extracts from the first‐order glands, and corresponds to an important protein component of the spermatophylax. J. Morphol., 2009. © 2009 Wiley‐Liss, Inc.     

Male insect accessory glands: Functions and control of secretory activity

Summary

Paralleling the diversity of the class Insecta, the male accessory glands (MAG) exhibit a wide range of form, and their secretion serves a variety of functions, including spermatophore and mating plug formation, sperm activation, provision of nutrients to females, and, through production of fecundity-enhancing and/or receptivity-inhibiting substances, modification of female reproductive behavior. In most insects, juvenile hormone (JH) is important in the regulation of MAG secretory activity; specifically, JH controls the production of particular proteins in the secretion. However, the production of some proteins appears not to be influenced by JH; rather, their synthesis is regulated by ecdysteroids. During sexual maturation, JH and ecdysteroids seem to interact to bring about a specified temporal sequence of protein synthesis in the MAG.     

The hormonal control of accessory reproductive gland development in female Schistocerca gregaria

Allatectomy of adult female Schistocerca gregaria prevents the normal development of the accessory reproductive glands and no secretion is produced. Development of the glands can be restored by the administration of synthetic juvenile hormone and the response is dose-dependent. A continuous supply of hormone is required for maintenance of secretory activity. In the normal developmental sequence the total protein content of the glands remains constant until the time at which vitellogenesis occurs in the terminal oöcytes. As maturation proceeds there is a linear increase in protein content of the glands. The initial increase occurs as a result of cellular changes in the glands and is then followed by an increase due to an accumulation of secretion in the lumina.     

A histochemical study of the secretions of reproductive glands and of the egg envelopes of Achatina fulica (Pulmonata: Stylommatophora)

Histochemical investigations of the secretions of reproductive glands—albumen gland, apical uterus, basal uterus and prostate gland—indicate the presence of galactogen in the albumen gland, acid mucopolysaccharide in the apical uterus, and lipoprotein in the basal uterus and prostate gland of A. fulica. The proteinaceous secretions produced by the glands do differ in their terminal reactive sites. Intense alkaline phosphatase reaction is found in albumen gland and apical uterus; carbonic anhydrase activity could be detected mainly in the uterine glands. The cyclical secretory activity of the reproductive glands has been studied preparatory to egg-laying and in the spent phase. Histochemical characteristics of the egg envelopes—albumen, shell membrane and egg-shell—suggest a possible sequential deposition of glandular products during the descent of eggs through the repv. ductive tract. The factors contributing to the stability and resistant nature of the egg envelopes, and the possible role of nutritive materials contained in reproductive gland secretions in the development of the embryo (even while the eggs are inside the uterus), are discussed.     

MUC16 in the lacrimal apparatus

The aim of the present study was to determine the possible expression of the mucin MUC16 in the lacrimal apparatus. Expression and distribution of MUC16 in lacrimal gland, accessory lacrimal glands, and nasolacrimal ducts was monitored by RT-PCR and immunohistochemistry. MUC16 was expressed and detected in all tissues investigated. Comparable to conjunctiva and cornea it was membrane-anchored in accessory lacrimal glands whereas in lacrimal gland acinar cells and columnar cells of the nasolacrimal ducts it was stored in intracytoplasmic vesicles without membrane-association. Subepithelial serous glands of the nasolacrimal ducts revealed staining of the secretion product. Intracelluar production of MUC16 is present in lacrimal gland and epithelial cells of the nasolacrimal ducts but it is not clear whether this MUC16 is secreted. MUC16 seems to be shedded or secreted from the epithelial surface of subepithelial serous glands of the nasolacrimal ducts. Our results show that MUC16 is present in the whole lacrimal apparatus. Its distribution pattern suggests different physiological functions with regard to tear film physiology and tear outflow. Moreover, the results demonstrate the existence of so far not recognized qualitative differences in the secretion product of main lacrimal gland and accessory lacrimal glands (glands of Krause).