Thoracic Salivary Glands Research Articles

Nosema apis and Nosema ceranae Tissue Tropism in Worker Honey Bees (Apis mellifera).

The microsporidia Nosema apis and Nosema ceranae are major honey bee pathogens that possess different characteristics in terms of the signs they produce, as well as disease development and transmission. Although the ventricular epithelium is generally considered the target tissue, indirect observations led to speculation that N. ceranae may also target other structures, possibly explaining at least some of the differences between these 2 species. To investigate the tropism of Nosema for honey bee tissues, we performed controlled laboratory infections by orally administering doses of 50 000 or 100 000 fresh mature spores of either species. The fat body was isolated from the infected bees, as well as organs from the digestive (esophagus, ventriculus, ileum, rectum), excretory (Malpighian tubules), circulatory (aorta, heart), respiratory (thoracic tracheas), exocrine (hypopharyngeal, mandibular and labial, cephalic, thoracic salivary glands), and sensory/nervous (brain, eyes and associated nerve structures, thoracic nerve ganglia) systems. Tissues were examined by light and electron microscopy at 7, 10, and 15 days postinfection. Both Nosema species were found to infect epithelial cells and clusters of regenerative cells in the ventriculus, and while the ileum and rectum contained spores of the microsporidia in the lumen, these structures did not show overt lesions. No stages of the parasites or cellular lesions were detected in the other organs tested, confirming the high tropism of both species for the ventricular epithelium cells. Thus, these direct histopathological observations indicate that neither of these 2 Nosema species exhibit tropism for honey bee organs other than the ventriculus.

Activity of salivary glands in secreting honey‐elaborating enzymes in two subspecies of honeybee (Apis melliferaL)

AbstractThe activity of invertase, glucose oxidase and amylase in the cephalic (post‐cerebral) and thoracic salivary glands is determined in Egyptian and Carniolan honeybees (Apis mellifera L). For this purpose, three ages of worker bees are selected for enzyme assays. The results show that the three target enzymes are detected in the two glands during the three worker ages, except invertase, which cannot be detected in the cephalic gland of newly emerged bees of both subspecies. In both glands, the secretion of invertase is highest, followed by amylase and then glucose oxidase. In Carniolan bees, invertase secretion of the cephalic and thoracic glands increases gradually with age. In Egyptian bees, invertase increases with age only in the cephalic gland, whereas, in the thoracic gland, the highest secretion activity is detected in 10–15‐day‐old bees. The highest amounts of glucose oxidase and amylase in the cephalic gland are detected in newly emerged individuals of both Egyptian and Carniolan bees. In the thoracic gland, however, the highest activity of both enzymes is recorded only in newly emerged Egyptian bees. The results are discussed in the light of bee management and biological aspects of the two subspecies.

Digestive enzyme secretion by thoracic salivary glands in honey beeApis cerana indica(Hymenoptera: Apidae)

The thoracic salivary glands in the honey bee, Apis cerana indica are coiled tubular structures. The light and electron microscopic studies revealed well defined cytoplasmic organelles performing protein synthesis and presence of abundant quantity of secretory granules in the cytoplasm in the glandular cells in the nurse and foraging bees. In worker bees, this extract contains high concentration of amylase and invertase. These findings strongly suggest active involvement of thoracic salivary glands in the carbohydrate digestion in order to produce honey.

Novel aspects of understanding molecular working mechanisms of salivary glands of worker honeybees (Apis mellifera) investigated by proteomics and phosphoproteomics

Honeybee salivary glands (SGs) are important exocrine glands. However, the molecular basis of how SGs fulfill their biological duty is still elusive. Proteomics and phosphoproteomics of cephalic SG (HSG) and thoracic SG (TSG) were compared between normal and single-cohort honeybee colonies. Of 113 and 64 differentially regulated proteins and phosphoproteins, 86 and 33 were identified, respectively. The SGs require a wide spectrum of proteins to support their multifaceted functions and ensure normal social management of the colony. Changes of protein expression and phosphoproteins are key role players. The HSG triggers labor transition from in-hive work to foraging activities via the regulation of juvenile hormone and ethyl oleate levels. The stronger expression of proteins involved in carbohydrate and energy metabolism, protein folding, protein metabolism, cellular homeostasis and cytoskeleton in TSG, supports the gland to efficiently enhance honey processing by synthesis and secretion of saliva into nectar. The age structure of the colony is vital for increased production efficiency. This data reveals the molecular underpinning of SGs to accomplish their biological missions and provides new knowledge for the beekeeping industry for enhancing the management and production efficiency of the colony and honey quality through manipulation of potential target proteins. This study comprehensively analyses the characteristic of the proteome and phosphoproteome of honeybee salivary glands (SGs) between normal and single-cohort honeybee colonies. The SGs need a wide spectrum of proteins to support their multifaceted functions and ensure normal social management of the colony. The cephalic SG triggers labor transition from in-hive work to foraging behavior via the regulation of juvenile hormone and ethyl oleate titer. The thoracic SG stronger expressed of proteins related to carbohydrate and energy metabolism, protein folding, protein metabolism, cellular homeostasis and cytoskeleton to support the gland to efficiently enhance honey processing by synthesis and secretion of saliva into nectar. This data reveals the molecular underpinning of SGs to accomplish their biological missions and provides new knowledge for the beekeeping industry for enhancing the maintenance and production efficiency of the colony and honey quality through manipulation of potential target proteins.

Changes in the size of cephalic salivary glands of Apis mellifera and Scaptotrigona postica (Hymenoptera: Apidae) queens and workers in different life phases

The bee species of the Apinae, in addition to the thoracic salivary glands, possess a pair of cephalic glands originating as branches of the excretory duct that crosses the head. These glands are known as cephalic salivary or labial cephalic glands. The degree of development of these glands in newly emerged, nurse and forager workers and virgin and egg-laying queens of Apis mellifera Linnaeus, 1758 and Scaptotrigona postica Latreille, 1807 were evaluated by measuring the secretory alveolar units. The area of the secretory alveoli, measured in total gland preparations, was used to evaluate differences in size. In both species, gland size was found to increase progressively from newly emerged workers to foragers and from virgin to egg-laying queens. A statistical analysis revealed significant differences (p < 0.05) in the area of gland alveoli of workers in different life phases in both species, and between S. postica virgin and egg-laying queens, but not between A. mellifera queens. In the case of workers, this suggests cephalic salivary gland secretion has a function in forager activity and, in queens, a possible pheromonal function.

Salivary system in leaf-cutting ants ( Atta sexdens rubropilosa Forel, 1908) castes: A confocal study

The salivary system in ants is not only limited to digestory functions, but also has important role in the communication. The glands which compose the salivary complex are: the post-pharyngeal, hypopharyngeal, mandibular, and thoracic salivary gland, showing peculiar features which may vary according to the castes the individuals belong to and according to the functions they develop. The present study compared the morphological differences among the glands of Atta sexdens rubropilosa workers, males and queens focused on the organization of microfilaments and microtubules in these ants salivary system. Although the post-pharyngeal gland appeared to be more developed in queens, there were no significant gland differences among the analyzed castes. In what regards to the secretory units of the hypopharyngeal and mandibular glands, the association of F-actin with the collector duct seemed to be strong, being surrounded by a microtubules arrangement. The use of a laser scanning confocal microscopy with immunofluorescence whole mounting preparations revealed itself an efficient instrument for the understanding of the internal morphology of insects.

Two structurally different defensin genes, one of them encoding a novel defensin isoform, are expressed in honeybee Apis mellifera

Two defensins showing high mutual similarity have previously been characterized in honeybee Apis mellifera: royalisin, a peptide isolated from the royal jelly, and defensin, found in the hemolymph of bacterially infected bees. Here we show that both these peptides are encoded by the same polymorphic gene, which we termed defensin1. Besides this gene, we identified an additional defensin gene coding for a novel honeybee defensin designated defensin2. The pre-pro-peptide sequence of defensin 2 was inferred from its cDNA. Mature defensin 2 peptide shows 55.8% identity with defensin 1. Sequences of genomic loci of the two defensin genes revealed their different structure. Defensin1 possesses an exon–intron structure unique among arthropoda defensin genes. Its second intron splits exactly the common structural module of defensins from a short amidated C-terminal extension found only in hymenopteran defensins. Transcription of defensin genes in some nurse honeybees tissues was studied by RT–PCR. Both defensins are expressed in heads and thoraces. Defensin1 but not defensin2 mRNA was detected in hyphopharyngeal, mandibular and thoracic salivary glands. Immune response elements were identified by computer analysis of the promoter regions of defensin genes. Their different representation in these genes reflects presumably observed tissue-specific expression of defensins.

Ultramorphology and histology of the Polistes versicolor (Oliver) (Vespidae) thorax salivary gland compared with other Hymenoptera

The salivary system of the Hymenoptera consists of the mandible, hypopharynx and thoracic salivary glands. It is very important because it is related to various aspects of the life of the insects, such as pheromone production, feeding the young, food digestion and nest building. Adult Polistes versicolor (Olivier) individuals were dissected, the thoracic salivary glands removed and processed for scanning electronic microscopy and histological examination. The P. versicolor thoracic salivary gland presents alveolar secretory units, consists of pseudoacines and does not have a reservoir. Four types of cells are present in the gland. The T1 and T2 cells make up the pseudoacines and differ mainly by the many secretory vessels in T2. There is a cluster of T3 cells at the base of the gland duct collectors, also with secretory characteristics. The secretion produced in the pseudoacines is conducted by canals and ducts to the outside, and the latter are made of T4 cells. The comparison of these characteristics with those of different Hymenoptera species, already studied, showed that the thoracic salivary gland cannot be used as a single comparison factor in evolutionary studies.

Anatomy and ultrastructure of the salivary gland in the thorax of the honeybee worker, Apis mellifera (Insecta, Hymenoptera)

The thoracic salivary gland of the worker honeybee was investigated by dissection, light microscopy, scanning electron microscopy, and transmission electron microscopy. The glands are paired and each lateral half consists of two parts, a smaller external and a larger internal lobe. The lobes are composed of densely packed secretory tubes and ducts, the tubes of which often show ramifications. A reservoir is packed within the anterior medial part of the gland. The secretory tubes are composed of two types of cells, secretory cells, which are most frequent, and parietal cells. Secretory cells are characterized by a basal labyrinth, abundant rough endoplasmic reticulum, dark secretory vesicles, light vesicles of different sizes, and apical microvilli. Parietal cells are smaller and have a characteristically lobed nucleus and no secretory vesicles. Between the cells there are intercellular canaliculi. In the center of each tube there is an extracellular space with a central cuticular channel. The abundance of rough endoplasmic reticulum and the rare occurrence of smooth endoplasmic reticulum implies a saliva with proteins but rarely with pheromones. Between the secretory tubes there are frequently neuronal profiles which are partly in contact with the secretory cells. Thus a nervous control of this gland is, in contrast to previous investigations, clearly demonstrated. The axonal endings contain dark neurosecretory vesicles as well as light synaptic vesicles. Large parts of the glands are surrounded by a thin tissue sheath which has a smooth surface towards the secretory tubes and shows irregular protrusions towards the outer side. This sheath is considered to be a tracheal air sac, and due to its large extension is probably of importance for the hemolymph flow in the thorax.

Dufour's gland and its role in secretion of nest cell lining in bees of the genusColletes (Hymenoptera: Colletidae)

The liquid secretion of the Dufour's gland in mated females comprises a mixture of macrocyclic lactones, straight chain mono- and dicarboxylic acids, together with trace amounts of di- and trihydroxy monocarboxylic acids and a series ofn-alkanes. Polymerization of the liquid to form the membranous nest cell lining, which also contains alanine and glutamic acid as major constituents, may be mediated by an enzyme from the thoracic salivary gland and voided via the mouth. The composition and structure of the cell linings are similar to those of Wigglesworth's “cuticulin.”

Histoquímica e ultraestrutura das glândulas salivares das abelhas (Hymenoptera, Apoidea)

This is a study of the four types of salivary glands normally occurring in bees. Current histochemical techniques were used to study variation of protein, polysaccharides, nucleic acids and lipids, during the secretory cycle. Ultrastructural techniques were used to follow the cellular organelles through the elaboration and elimination of secretory products. Much quantitative variation was found in all substances studied, between glands and between stages of the same gland. The thoracic salivary gland of Melipona was found to secrete protein, and the head gland lipids. Glycogen was found only in the glands of very young bees, and is thought to be an embryonic remnant. Electron microscopy showed that the cellular organelles evolve during the secretory cycle according to what is generally known for cells with similar functions. The Golgi apparatus was not seen in Xylocopa and Colletes, probably because part of the secretion products are stored in vacuoles. The data permit to derive thoracic salivary gland types 1, 2 and 3 from type 4. Type 1 would result from the disappearance of the central (zymogenic) cells; type 2 by reduction only of the number of these cells; type 3 by disappearance of the peripheral (parietal) cells.

The post-embryonic changes in Melipona quadrifasciata anthidioides Lep. (Hym. Apoidea). II. Development of the salivary glands system.

AbstractThe paper deals with the development of the salivary gland system in Melipona quadrifasciata anthidioides, which begins in the prepupal stage. The silk glands degenerate by autolysis at the end of the larval stage. Degeneration is characterized by cytoplasmic vacuolization and pycnosis of the nuclei of the secretory cells. The glandular secretory portion of degenerated silk glands separates from the excretory ducts. The salivary glands develop from the duct of the larval silk glands. The thoracic salivary glands develop from the ducts of the secretory tubules and the head salivary glands from the terminal excretory duct. The mandibular glands appear in the prepupa as invaginations of mandibular segments, and their differentiation to attain the adult configuration occurs during pupation. The hypopharyngeal glands have their origin from evaginations of the ventral anterior portion of the pharynx. A long tubule first appears with walls formed by more than one cellular layer. Then some cells separate from the lumen of the duct, staying attached to it by a cuticular channel in part intracellular. The initial duct constitutes the axial duct, in which the channel of the secretory cells opens. During the development of salivary and mandibular glands, they recapitulate primitive stages of the phylogeny of the bees. During the development of salivary glands system, mitosis accounts for only part of the growth. Most of the growth occurs by increase in size of cells rather than by cell division. In brown‐eyed and pigmented pupae six days before emergence, the salivary gland system is completely developed, although not yet functioning.

THE RELATION OF HERPETOMONAS ELMASSIANI (MIGONE) TO ITS PLANT AND INSECT HOSTS

Histological studies of the milkweed host of the flagellate Herpetomonas elmassiani (Migone) showed that the organisms were confined to the latex system, in which they were intracellular but not intracytoplasmic. The latex is secreted into the general cell vacuole of the latex duct, and it is in this that the organisms were found. No other cells or parts of cells were found to be penetrated.During the early part of the summer one or a very few latex cells in a plant were sometimes infected, for in Asclepias the original latex cells of the embryo never fuse. Because of this condition occasional localized infections appeared, in which a few leaves of the infected plant were found to be free from organisms.The flagellates of Oncopeltus fasciatus (Dall.), a red and black hemipterous insect suspected of being the insect host of H. elmassiani (Migone), were found to inhabit the three-lobed thoracic salivary gland. In the gland these were definitely localized, colonizing only the dorsal and anterior lobes.