Morphology and ultrastructure of a secretory region enclosed by the venom reservoir in social wasps (Insecta,Hymenoptera)

The morphology and ultrastructure of the convoluted gland inside the venom reservoir of four species of social Vespidae are described. The cells of the venom gland (including the convoluted gland) can be divided into six groups: (1) epithelial cells, (2) glandular cells with the end apparatus secreting into the tubule inside the convoluted gland (internal or embedded tubule), (3) a continuous arrangement of glandular cells with the end apparatus secreting directly into the venom reservoir, (4) glandular cells that are loosely dispersed along the tubule lumen between the free tubules and the embedded tubule of the convoluted gland, (5) secretory cells of the free tubules and (6) duct cells. One kind of secretory cell, hitherto unknown and described in this paper (group 3), is characterized by the presence of a well-developed end apparatus, usually with enlarged extracellular spaces, but lacking the normally associated duct cells. The secretory cells contain several stacks of granular endoplasmic reticulum, but these are mainly concentrated in the middle of the cell. The basal half of the cells contains many lipid droplets. Although the function of the convoluted gland is not yet understood, an hypothesis is related to what is known of the function of reservoir secretory cells in solitary wasps. All wasp species studied showed the same organization of the convoluted gland, which clearly distinguishes their venom gland from that of Sphecidae.     

Venom gland ontogeny in Formicinae, with special reference to the pulvinate convoluted gland (Hymenoptera, Formicidae)

 The primordia of the sclerites associated with the venom gland appear in third-stage larvae. The study aims to link the structure and function of this specialised venom structure in Formicinae, together with glandular ontogeny, and puts emphasis on the relevance of the distinguished glandular subunits contributing to the final secretion. The most conspicuous changes in glandular development occur in the pharate pupa. At this stage, all subunits of the venom gland (the tubule, the convoluted gland and reservoir) are visibly present. Formation of the glandular cuticle starts around day 4 of the pupal stage. Luminal cells in the convoluted gland are provided with abundant free ribosomes and apical microvilli that remain during adult life. Stacks of granular endoplasmic reticulum are also frequently found in these cells. The convoluted gland contains relatively few scattered secretory cells, belonging to type 3 according to Noirot and Quennedey (1974), which contain electron-dense material in their extracellular spaces during adult life. These cells strongly contrast with the apparently general non-glandular nature of the convoluted gland tubule. Histochemical investigation of the secretory cells in the pulvinate convoluted gland reveals that these cells contain lipoid material, most likely to correspond with lipoids demonstrated in earlier chemical analyses. This lipoidal material in minor quantities strongly contrasts with the bulk of acid constituting the secretion. The substances produced in the convoluted gland could act as insulators, thus protecting the insect against its corrosive venom. Accepted: 28 April 1998     

Venom gland of the digger wasp Liris niger: morphology, ultrastructure, age-related changes and biochemical aspects

Females of the parasitoid digger wasp species Liris niger hunt crickets as food for their future brood. The wasps paralyse the prey by injecting their venom directly into the CNS. The venom is produced in a gland consisting of two ramified glandular tubules terminating in a common reservoir. The reservoir contents enter the sting bulb via a ductus venatus. Secretory units of dermal gland type III line the two free gland tubules, the afferent ducts to the reservoir and the cap region within the reservoir. Secretion products of tubules reach the reservoir through the cuticle-lined central funnel. Secretory cells in the distal and middle parts of the tubules contain extensive rough endoplasmic reticulum and numerous electron-dense vesicles, whereas secretory cells of the afferent ducts and the cap region of the reservoir lack electron-dense vesicles and the endoplasmic reticulum is poorly developed. The secretory apparatus undergoes age-related changes. The secretory units in the venom gland tubules and inside the reservoir complete differentiation 1 day after imaginal ecdysis. After 30 days, massive autolytic processes occur in the secretory cells and in the epithelial cells of the reservoir. Analysis of the polypeptide composition demonstrates that the venom reservoir contains numerous proteins ranging from 3.4 to 200 kDa. A dominant component is a glycoprotein of about 90 kDa. In contrast the polypeptide composition of Dufour's gland is completely different and contains no glycoproteins. Comparison of the venom reservoir contents with the polypeptide pattern of venom droplets reveals that all of the major proteinaceous constituents become secreted. Thus the secreted venom contains exclusively proteins present in the soluble contents of the venom gland.     

Venom gland of the ichneumonid Diadromus collaris： morphology, ultrastructure and age-related changes

Females of the solitary parasitoid Diadromus collaris （Insecta： Hymenoptera： Ichneumonidae） lay eggs in the pupae of Plutella xylostella （Lepidoptera： Plutellidae）, and the venom is synchronously injected into hosts. The venom apparatus consists of two glandular tubules terminating in a common reservoir, A ductule connects the reservoir with the sting apparatus, by which the reservoir content enters the latter. Secretory units line the two glandular tubules. All secretory cells belong to dermal gland type Ⅲ. Dermal gland cells in glandular tubules are more abundant and developed than those in the reservoir. There are extensive rough endoplasmic reticulum and electrondense vesicles, and the microvilli are well developed. By the cuticle-lined central funnel secretion products of secretory units reach the reservoir. Moreover, the secretory apparatus undergoes age-related changes. The secretory units in the venom gland are better developed and more vigorous 7 days after eclosion than those 1 day after eclosion; autolytic processes occur 15 days after eclosion, and the tissue of the reservoir is more prostrate 15 day after eclosion than those 1 day after eclosion. The ovipostion peak of this parasitoid, about 3-7 days after eclosion, corresponds with the period when the venom gland is highly developed in the life span of the wasp.     

The venom apparatus in stenogastrine wasps: Subcellular features of the convoluted gland

In the wasp venom apparatus, the convoluted gland is the tract of the thin secretory unit, i.e. filament, contained in the muscular reservoir. Previous transmission electron microscope investigation on Stenogastrinae disclosed that the free filaments consist of distal and proximal tracts, from/to the venom reservoir, characterized by class 3 and 2 gland patterns, respectively. This study aims to extend the ultrastructural analysis to the convoluted tract, in order to provide a thorough, subcellular representation of the venom gland in these Asian wasps. Our findings showed that the convoluted gland is a continuation of the proximal tract, with secretory cells provided with a peculiar apical invagination, the extracellular cavity, collecting their products. This compartment holds a simple end-apparatus lined by large and ramified microvilli that contribute to the processing of the secretory product. A comparison between previous and present findings reveals a noticeable regionalization of the stenogastrine venom filaments and suggests that the secretory product acquires its ultimate composition in the convoluted tract.     

Venom and Dufour's glands of the emerald cockroach wasp Ampulex compressa (Insecta,Hymenoptera, Sphecidae): Structural and biochemical aspects

The digger wasp species Ampulex compressa produces its venom in two branched gland tubules. They terminate in a short common duct, which is bifurcated at its proximal end. One leg is linked with the venom reservoir, the other one extends to the ductus venatus. Each venom gland tubule possesses, over its entire length, a cuticle-lined central duct. Around this duct densely packed class 3 gland units each composed of a secretory cell and a canal cell are arranged. The position of their nuclei was demonstrated by DAPI staining. The brush border of the secretory cells surrounds the coiled end-apparatus. Venom is stored in a bladder like reservoir, which is surrounded by a thin reticulated layer of muscle fibres. The reservoir as a whole is lined with class 3 gland units. The tubiform Dufour's gland has a length of about 350 μm (∅ 125 μm) only and is surrounded by a network of pronounced striated muscle fibres. The glandular epithelium is mono-layered belonging to the class 1 type of insect epidermal glands. The gland cells are characterized by conspicuous lipid vesicles. Secretion of material via the gland cuticle into the gland lumen is apparent. Analysis of the polypeptide composition demonstrated that the free gland tubules and the venom reservoir contain numerous proteins ranging from 3.4 to 200 kDa. The polypeptide composition of the Dufour's gland is completely different and contains no lectin-binding glycoproteins, whereas a dominant component of the venom droplets is a glycoprotein of about 80 kDa. Comparison of the venom reservoir contents with the polypeptide pattern of venom droplets revealed that all of the major proteinaceous constituents are secreted. The secreted venom contains exclusively proteins present in the soluble contents of the venom gland. The most abundant compound class in the Dufour's gland consisted of n-alkanes followed by monomethyl-branched alkanes and alkadienes. Heptacosane was the most abundant n-alkane. Furthermore, a single volatile compound, 2-methylpentan-3-one, was identified in various concentrations in the lipid extract of the Dufour's gland.     

Morphology and ultrastructure of the dufour's and venom gland in the ant,Myrmica rubra (L.) (Hymenoptera : Formicidae)

The morphology and fine structure of the Dufour's and venom gland, as well as their entrance into the sting, are described in the myrmicine ant, Myrmica rubra (Hymenoptera : Formicidae). The epithelial cells that constitute the Dufour's gland wall, contain a well-developed smooth endoplasmic reticulum. Older workers, compared with younger ones, show an increasing number of multilamellar inclusions. The venom gland secretory cells are arranged in 2 free filaments that carry the secretion to the reservoir. Their cytoplasm shows an intracellular collecting ductule with surrounding microvillar sheath, and an abundance of free ribosomes. However, a well-organized granular endoplasmic reticulum, which is typical in species with a more powerful sting, does not occur. Both the Dufour's and venom gland ducts are characterized by the insertion of extensive muscle fibres, which act as a precise and mutually independent control mechanism for the discharging activities of the 2 glands.     

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。     

腰带长体茧蜂毒液器官和卵巢的形态学及其超微结构

应用超薄切片和电镜技术,观察内寄生蜂腰带长体茧蜂Macrocentrus cingulum Brischke毒液器官和卵巢的形态结构。腰带长体茧蜂毒液器官由1个毒囊和2条毒腺组成,毒腺接于毒囊的顶端。毒腺由单层分泌细胞、退化的外胚层细胞和环腔的内膜构成,分泌细胞主要由1个明显的细胞核和1个较大囊状细胞器构成,囊状细胞器的功能是分泌毒液。毒囊由肌肉鞘和扁平细胞层构成,但没有分泌细胞。腰带长体茧蜂卵巢1对,每个卵巢由10条左右卵巢小管组成,与侧输卵管相接处略微膨大形成卵巢萼区。2条侧输卵管在产卵管基部会合形成1条总输卵管与产卵管相接。毒液器官通过毒囊的毒液导管附着在总输卵管上。对寄生蜂毒液器官的生物学、细胞学及在分类进化上的意义进行研究。     

管氏肿腿蜂毒液器官超微结构观察

应用透射电镜技术,观察了管氏肿腿蜂Scleroderma guani毒液器官的超微结构.毒腺由基膜层、分泌细胞层、导管细胞层和内膜层构成,分泌细胞内含内质网、末端附器、分泌囊泡、分泌颗粒、液泡等细胞器,其内合成的毒液由末端附器输送至毒腺的腔体.毒囊由肌肉鞘层、上皮细胞层和内膜层组成,肌肉鞘内的肌纤丝规则排列不交错,上皮细胞层内细胞器稀少,内膜层呈波浪状均匀加厚.     

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.     

Fine Structure of Female Accessory Reproductive Gland in the Mealworm Beetle, Tenebrio molitor

ABSTRACT The fine structure of female accessory reproductive gland (FARG) of the adult mealworm beetle, Tenebrio molitor is studied with light and electron microscopes. The FARG is a simple tubular organ that composed of two kinds of cells-secretory epithelial cells and duct forming cells. The lumen of FARG is lined with a thin cuticle and filled with secretory materials. Each secretory epithelial cell has its peculiar end apparatus in addition to well-developed rough endoplasmic reticulum (rER), mitochondria, and secretory vesicles. They are forming basal infolding along the plasma membrane. Along the inner surface of the plasma membrane, numerous secretory vesicles are seen. The glandular secretions of the epithelial secretory cells are synthesized via rER to Golgi apparatus, and are stored in the extracellular cavity in the epithelial cell. These secretions are drained to the lumen through the end apparatus and this type of glandular secretion in the insects is type III. Histochemical reactions reveal the major component of these glandular secretions is an acid mucopolysaccharide.     

Venom gland and reservoir morphology in cynipoid wasps

The venom apparatus morphology was examined in 25 species of Cynipoidea, representing 11 parasitoid taxa; 12 gall inducers and two inquilines. Typically the venom apparatus consists of an oval or bilobed reservoir connected to the ovipositor apparatus by a very short venom duct at the anterior end and to a single elongate unbranched venom gland at or near its posterior end. The Dufour's gland was not found in any of the examined species. The elongate unbranched venom gland and the absence of the Dufour's gland are putative cynipoid synapomorphies. The shape and size of especially the venom reservoir were found to vary considerably within the Cynipoidea. It is typically less prominent in the parasitoid taxa than in the gall inducers. Exceptions include the poppy gallers Barbotinia and Aylax, in which the venom reservoirs were remarkably small and in the rose galler Diplolepis, where only a rudimentary venom apparatus was found. Possible functional and phylogenetic implications of cynipoid venom apparatus features are discussed.     

Biochemical and histocytochemical studies on response of ammonia-producing enzymes for nh4cl-induced acidosis.

NH4Cl-induced acidosis in rats resulted in renal enlargement and increase in activities of phosphate-dependent glutaminase and glutamic dehydrogenase. The renal enlargement was associated with protein synthesis but not deoxyribonucleic acid synthesis. In control rats histochemical activity of glutamic dehydrogenase was seen dominantly in the proximal straight tubule. In acidotic rats high activity was noted in the proximal convoluted tubule as well as in the proximal straight tubule. By electron microscopy reaction product was in mitochondria. The results suggest that urine ammonia is produced in mitochondria of epithelial cells in the proximal straight tubule in both normal and acidotic rats. Increased enzyme activity in acidotic rats is largely associated with epithelial cells of the proximal convoluted tubule.     

Ultrastructural modifications in the venom glands of workers of Apis mellifera L. (Hymenoptera: Apidae) promoted by topical application of juvenile hormone

The present study analyzed, the influence of the treatment with juvenile hormone on the ultrastructure of Apis mellifera L. workers' venom glands. Newly emerged workers received topical application of 1 microl of juvenile hormone diluted in hexane, in the concentration of 2 microg/pl. Two controls were used; one control received no treatment (group C1) and other received topical application of 1 microl of hexane (group C2). The aspect of the glandular cells, in not treated newly emerged workers, showed that they are not yet secreting actively. Cellular modifications happened according to the worker age and to the glandular area considered. The most active phase of the gland happened from the emergence to the 14th day. At the 25th day the cells had already lost their secretory characteristic, being the distal area the first to suffer degeneration. The treatment with juvenile hormone and hexane altered the temporal sequence of the glandular cycle, forwarding the secretory cycle and degeneration of the venom gland.     

Exocrine glands of the ant Myrmoteras iriodum

This paper describes the morphological characteristics of nine major exocrine glands in workers of the formicine ant Myrmoteras iriodum. The elongate mandibles reveal along their entire length a conspicuous intramandibular gland, which contains both class‐1 and class‐3 secretory cells. The secretory cells of the mandibular glands show a peculiar appearance, with a branched end apparatus, which is unusual for ants. The other major glands (pro‐ and postpharyngeal gland, infrabuccal cavity gland, labial gland, metapleural gland, venom gland and Dufour gland) show common features for formicine ants. The precise function of the glands could not yet be experimentally demonstrated, and to clarify this will depend on the availability of live material of these enigmatic ants in future.     

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.     

The fine structure of the maxillary gland of the brine shrimp,Artemia salina: The efferent duct

Summary The efferent duct of the maxillary gland of adult brine shrimp, Artemia salina, is specialized into two morphologically distinct regions: an efferent tubule and a terminal duct. The wall of the efferent tubule is composed of epithelial cells which possess an apical microvillous border and, more basally, membranous configurations with which large numbers of mitochondria are closely associated. These membranous configurations are of two types: 1) infoldings of the plasma membrane of a single cell, and 2) interdigitations of lateral processes from adjoining cells. In contrast to the efferent tubule, the cells of the terminal duct possess a secreted cuticle and lack modifications which markedly increase the area of the plasma membrane. Mitochondria of the terminal duct are smaller and less numerous than those of the efferent tubule and typically are not found in close association with the plasma membrane. The ultrastructure of the efferent tubule and terminal duct suggests that the former region plays an active role in modifying the luminal contents and the latter region functions primarily as a conduit for the final urine.     

Morphology of defense glands of the opilionids (daddy longlegs) Leiobunum vittatum and L. flavum (Arachnida: Opiliones: Palpatores: Phalangiidae)

Opilionid defense glands consist of 0.5 × 0.9-mm sacs attached to the underside of low tubercles located on the dorsal side of the cephalothorax, posterior to the first pair of legs. Each gland opens via an elongated slit, located in the posterior floor of a crater that is situated at the summit of the tubercle. The center of the sac, called the reservoir, is lined by a cuticle consisting of epicuticle and endocuticle which is continuous through the slit with the exoskeleton. The layers of cuticle vary in thickness with different locations in the gland. A hemocoelomic (basement) membrane, 0.5–1, μ thick, forms the boundary between glandular cells and hemocoel. The gland has a nonsecretory portion consisting only of cuticle-supporting cells and a secretory portion consisting of secretory and cuticle-supporting cells. The cuticle lining the reservoir in the secretory area is broached by many cuticle-lined ductules, each of which drains an isolated intercellular space called the intercalated cistern. This in turn drains microvilli-lined canaliculi located between and extending into secretory cells. The cisterns are devoid of microvilli. Secretory cell cytoplasm contains a Golgi apparatus, many free ribosomes, rough endoplasmic reticulum (RER), two types of granules (speckled and dense), and mitochondria. Speckled granules are partially filled with fairly large particles and are found in association with the Golgi apparatus. They also surround canaliculi into which they empty. Dense granules are packed with very small particles, have a gray homogeneous appearance, and are scattered throughout the cytoplasm. Mitochondria containing matrix granules tend to scatter throughout the cytoplasm but are concentrated around canaliculi.     

Pedestal hairs of the ant Echinopla melanarctos (Hymenoptera, Formicidae): morphology and functional aspects

The South East Asian arboreal Formicine Echinopla melanarctos, as well as some other members of this genus possess a cuticular structure unique in ants, the pedestal hairs. In E. melanarctos, about 700 pedestal hairs are situated on the dorsal and lateral surfaces of the head, the alitrunk, the petiole and the gaster. They are arranged in a polygon-like figuration. On the summit of each of the up to 200-μm high pedestals, a single central hair inserts. This hair (up to 500-μm long) is innervated by a single bipolar mechanosensitive sensory cell. The lumen of each tube-like pedestal contains (1) epithelial cells (2) the sensory cell and the auxiliary cells of the central hair and (3) the long efferent ductules of up to ten isolated bicellular glandular units. Each glandular unit is composed of a secretory glandular cell and a duct cell, all of which are located at the base of a pedestal. The cytoplasm of a glandular cell contains a well-developed end apparatus and is characterised by stacks of smooth and granular endoplasmic reticulum, numerous polyribosomes, a lot of mitochondria and some up to 5-μm large secretory vesicles. The secretion of the gland cells is released on the apex of the pedestal wall via small pores. Approximately 30 μm below their summit, some pedestals possess additionally (up to six) mechanosensitive hairs that are arranged ray-like. We suppose that the pedestal hairs are important in nest-space protection and find that only in ants with high pedestals on the head (Echinopla melanarctos and Echinopla pallipes), the compound eyes are stalked thus overtopping the pedestals.