Glands Of Insects Research Articles

Midgut of Lepidopteran pupae is a major depot of sequestered, mobilizable, ecdysteroids

Extirpation of endocrine organs - a classic maneuver in hormonal research - has been difficult or impossible in the case of the prothoracic glands (PG) of insects. In larval and pupal Lepidoptera the glands are virtually inaccessible unless one sacrifices the insect. Even then, the PG are not easy to remove in their entirety. Consequently, in order to obtain viable preparations lacking PG, one costomarily makes use of abdomens isolated by litigation or surgery.

ULTRASTRUCTURAL ANALYSIS OF THE PLEOPOD TEGUMENTAL GLANDS IN MALE AND FEMALE LOBSTERS, HOMARUS AMERICANUS

We have examined the ultrastructure of the glands in pleopods of mature male and of juvenile and sexually mature female lobsters. Glands are present in both sexes but are most abundant in sexually mature females with well-developed ovaries. The glands are comprised of three cell types (secretory cells, a central cell, and a canal cell) which are arranged in rosettes. There are two types of secretory cells: one produces homogeneous granules and the other honeycombed granules. The central cell has peripheral and central lobes; the central lobes interdigitate with narrow apical projections on the secretory cells. The canal cell possesses a thin ductule which opens into the lumen of the gland and appears to convey secretory material from the lumen to the surface of the cuticle. Scanning electron micrographs of the surface reveal that exudate is usually present in the ductule openings; this suggests that the glands secrete continually. Because of their ultrastructural features, we propose that these glands be referred to as pleopod tegumental glands. Our data suggest that the tegumental glands have functions beyond attachment of fertilized eggs to the ovigerous setae. The first description of the glands in the pleopods of American lobsters (Homarus americanus) was provided by Herrick (1893). Various terms, including cement glands, glands, abdominal glands, and tegumental glands, have since been used to describe these glands (Aiken and Waddy, 1982). For reasons given below in Results, we refer to these glands as pleopod tegumental glands. The glands in crustacean pleopods are organized in rosettes (Herrick, 1893, 1895, 1909; Yonge, 1932, 1937), and, at the light microscope level, resemble tegumental glands which are present ubiquitously beneath cuticular surfaces of arthropods. Tegumental glands in the eyestalk of Homarus americanus (Arsenault et al., 1979), in the gills of Palaemonetes pugio (Doughtie and Rao, 1982), and in the head and mouth parts of Porcellio scaber (Gorvett, 1946) are organized in rosettes consisting of a canal cell and a cluster of secretory cells which are radially arranged around a central cell (Herrick, 1895; Yonge, 1932; Gorvett, 1946; Arsenault et al., 1979; Aiken and Waddy, 1982; Doughtie and Rao, 1982). A small ductule passes through the center of the canal cell and conveys secretory product from the lumen of the gland to the exterior surface of the cuticle (Yonge, 1932; Doughtie and Rao, 1982). This arrangement of cells is quite similar to class IIItype epidermal exocrine glands of insects as defined by Noirot and Quennedy (1974). Pleopod tegumental glands in female H. americanus and other macrurans are generally considered to cycle in phase with the ovary and not with molting (Herrick, 1895; Yonge, 1932, 1937; Aiken and Waddy, 1982). It has been clearly established that as the ovary develops, the tegumental glands become engorged with an opaque white substance (Herrick, 1893, 1895, 1909; Yonge, 1937; Stephens, 1952; Lowe, 1961; Cheung, 1966; Waddy and Aiken, 1980). The function of the glands is unresolved, but because they cycle with the ovary, and because of their location near the ovigerous setae, they are thought to be involved in the attachment of fertilized eggs to the ovigerous setae (Braun, 1875, 1876; Herrick, 1893; Yonge, 1937; Silberbauer, 1971; Fisher and Clark,

The Y organ of the crab, [formula omitted]: Effects of ecdysterone on the ultrastructure

The cells of the Y organ have a large nucleus relative to the cytoplasm. The cytoplasm contains mitochondria and a conspicuous smooth endoplasmic reticulum (ER), but the rough ER and Golgi complexes are not well developed. During premolt the infoldings of the plasma membrane were more highly developed than during any other stage of the cycle. Free ribosomes are more numerous in crabs injected with the molting hormone, ecdysterone, and the smooth ER and Golgi complexes are more developed. Many investigators have studied the molting process of crustaceans. Gabe (1953) first described a glandular organ, which he named the Y organ, and suggested that it is the ecdysial gland of crustaceans, homologous to the prothoracic gland in insects. Echalier (1954, 1955, 1959) showed that the Y organ is indeed involved in the control of ecdysis, having performed did removal and implantation experiments with Y organs of the shore crab, Carcinus maenas . Molting in higher Crustacea is now generally agreed to be hormonally regulated, by the molt inhibiting hormone from the neuroendocrine complex of the eyestalks (the X organ-sinus gland system) and by ecdysteroids from the Y organ. A molting hormone, ecdysterone, also known as beta-ecdysone, crustecdysone, ecdysterone, and 20-hydroxyecdysone, has been isolated Horn, Fabbri, Hampshire and Lowe, 1968; Faux, Horn, Middleton, Fales and Lowe, 1968. The purpose of this study was to determine the effects of edcysterone on the ultrastructure of the Y organ of the crab, Portunus trituberculatus .

Ecdysterone acts in G 2 to accelerate cell cycling in an insect gland : [formula omitted], [formula omitted][formula omitted], [formula omitted][formula omitted][formula omitted]. Department of Zoology, University of Vermont, Burlington, VT 05405 USA

Ecdysterone acts in G 2 to accelerate cell cycling in an insect gland : [formula omitted], [formula omitted][formula omitted], [formula omitted][formula omitted][formula omitted]. Department of Zoology, University of Vermont, Burlington, VT 05405 USA

The functional morphology of the brood sac in two species of ovoviviparous cockroaches,Byrsotria fumigata(Guerin) andGromphadorhina portentosa(Schaum). 2. Transmission electron microscopy

Summary Ultrastructural examination of the brood sac papillae in the ovoviviparous cockroaches Byrsotria fumigata and Gromphadorhina portentosa has revealed the presence of glandular units typical of the integumentary glands of many insects. Each unit includes a duct which originates within a large columnar secretory cell and passes through a duct or canal cell before opening at a pore on the cuticularised apex of a papilla. The structure of the glandular units from virgin and pregnant animals is described. Comparison of the ultrastructure of these brood sacs with that of the viviparous Diploptera punctata enables the ovoviviparous status of B. fumigata and G. portentonsa to be questioned.

Relationship of polyphosphoinositide metabolism to the hormonal activation of the inset salivary gland by 5-hydroxytryptamine

Incubation of the insect gland with [ 3H]inositol results in the incorporation of label into both phosphatidylinositol (PI) and the two polyphosphoinositides (PIP and PIP 2). Upon stimulation with 5-HT the initial water-soluble metabolites released are inositol trisphosphate and inositol bisphosphate with no change in the level of inositol monophosphate, suggesting that the primary lipid substrate used by the receptor is one of the polyphosphoinositides (most likely PIP 2) rather than PI. This conclusion was substantiated by showing that 5-HT was not able to release inositol or inositol monophosphate when the levels of the two polyphosphoinositides were reduced by lowering the level of ATP. The rate of breakdown of the polyphosphoinositides, as measured by the appearance of inositol phosphates, occurred with no apparent lag whereas the onset of the calcium-dependent change in transepithelial potential had a latency of approximately 1 sec. It is concluded that the primary action of 5-HT is to stimulate the hydrolysis of PIP 2 into diacylglycerol and inositol trisphosphate. The latter may function as a second messenger to mobilize the calcium responsible for initiating some of the ionic events responsible for fluid secretion.

Isopropylesters as wetting agents from the defensive secretion of the rove beetle Coprophilus striatulus F. (Coleoptera, Staphylinidae)

The defensive gland secretion of the rove beetle Coprophilus striatulus F. (Staphylinidae), Oxytelinae) has been shown to contain p- toluquinone , p- toluhydroquinone and a series of long chained saturated and unsaturated iso propylesters which were demonstrated by gas chromatography and mass spectrometry. The co-occurrence of at least five free fatty acids was confirmed by gas chromatography. The defensive glands of C. striatulus represent the first reported source of iso propylesters from defensive glands of insects. By contact angle measurements synthetic quinoid iso propylester mixtures have been shown to possess excellent wetting properties on chitin surfaces. Moreover the quinoid iso propylester mixture was highly effective against immersed Calliphora erythrocephala larvae. As a primitive member of the Oxytelinae C. striatulus differs distinctly from derived species of the same subfamily both with respect to the defensive gland morphology and the chemistry of the secretion.

Detection of pheromone biosynthetic and degradative enzymes in vitro.

Highly sensitive, luminescent assays have been developed to measure enzyme activities involved in the metabolism of a major class of insect pheromones which includes fatty aldehydes, alcohols, and their acetate esters. These assays have been applied to measure the in vitro biosynthesis and degradation of the sex pheromone (trans:cis-11-tetradecenal, 96:4) of the eastern spruce budworm, Choristoneura fumiferana. Three activities were detected on analyses of extracts of the female moths: (a) an esterase that hydrolyzes both the cis and trans isomers of 11-tetradecenyl acetate, (b) an oxidase that converts fatty alcohols to aldehydes in the presence of O2, and (c) an NAD-dependent aldehyde dehydrogenase. The coupled luminescent response of bacterial luciferase to long chain aldehydes was used to measure rates of reaction as low as 0.1 pmol/min since only low amounts of material can be analyzed. Specific activities of these enzymes were higher in the pheromone producing gland than in other parts of the moth, implicating these enzymes, and the oxidase in particular, in the pathway of pheromone biosynthesis. The pathway was supported in vivo by demonstrating that topical application of 3H-labeled tetradecanyl acetate onto the insect gland resulted in the formation of [3H]tetradecanol and [3H]tetradecanoic acid, thus providing evidence that all three enzymes were functional in the living insects.

Immuno-electron-microscopic evidence of ecdysteroids in Y-organ of Orconectes limosus (Crustacea, Decapoda).

Ecdysone was demonstrated by ultrastructural immunocytochemistry to be present in the mitochondria of the Y-organs of the crayfish Orconectes limosus. This is in remarkable contrast to the prothoracic glands of insects and suggests substantial differences in the biosynthesis of the same hormone, ecdysone, in crustaceans and insects.

Morphology of the region of the ejaculatory duct producing the male accessory gland material in the stable fly, Stomoxys calcitrans L. (Diptera: Muscidae)

A study of the synthesis of male accessory gland material in the stable fly, Stomoxys calcitrans (Diptera: Muscidae), revealed that the structure of these cells and therefore the mode of release of their product is unlike that previously reported for male accessory glands of insects, including other calypterate flies. The product of these cells is released into urn-shaped, villar-lined canaliculi that extend the length of each cell, instead of being secreted directly into the intimal-lined lumen of the accessory duct.

The timing and role of DNA synthesis in insect gland development

Metamorphosis of the non-dividing labial gland cells of Manduca sexta involves their transformation from silk to salivary function. In an investigation of the role of DNA synthesis in this process, the timing of DNA synthesis was studied in vivo and in vitro by incorporation of [ 3H]-thymidine and quantitative estimates of DNA content were made at selected periods of development. While DNA synthesis both precedes and occurs during this process of transformation, the most prominent period of synthesis appears to be coupled to gland growth, but occurs too late to trigger adult differentiation. Blood levels of [ 3H]-thymidine were assayed to determine the efficacy of label in vivo. Following single injections, approximately 60% of the radioactivity remains in the blood during the first 4 hr, but is reduced by 21 hr. The rate of [ 3H]-thymidine catabolism varies among individual insects so that between 2 and 17% [ 3H]-thymidine is actually available after 4 hr in vivo. Continuous perfusion of [ 3H]-thymidine into the blood was used to investigate incorporation into gland cells, in addition to using single injection studies.

The development of the female accessory gland in the insect Rhodnius prolixus

The specialized cell types and two distinct regions of the adult Rhodnius prolixus cement gland develop from a simple pseudostratified epithelial tube during the 20–22 days of the fifth stadium. Feeding initiates the first phase, proliferation. Cells round up and divide tangentially to the lumen. Following the proliferation phase, differentiative mitoses occur and differentiation, resulting in secretory units (consisting of a ductule, gland cell and cuticular lining), ensues in the distal region. Ductule morphogenesis occurs without pseudocilia, thus differing from other insect glands. The complex changes in cell shape and interaction occur during development of the secretory unit. The secretory cell and end-apparatus develop from a double cell unit at the base of elongating ductules. The inner cell produces a complex end-apparatus of epicuticle that mirrors the microvillar pattern and then it degenerates. The ductules are lined by cuticulin and inner epicuticle while the central gland lumen has a layer of endocuticle as well. The epithelium of the proximal region remains simple producing the thick corrugated cuticle characteristic of the adult secretory duct. The mesodermal covering forms a thick longitudinal striated muscle layer that adheres to the epithelium via desmosomes.

The salivary and crop apyrase activity of Rhodnius prolixus

A calcium dependent apyrase activity (ATP→AMP + 2Pi) has been characterized in the salivary secretion of Rhodnius prolixus. High levels of this activity were found in the crop of all stages of larvae and the adults after a single blood or saline meal. The activity persisted for several days but was totally absent in the crop insects from which the salivary glands had been removed. The use of this activity as a saliva marker shows that the insect salivates during the whole meal and most of the saliva is ingested with the food. The physiological role of this activity is discussed. A simple method for saliva collection and a technique for the surgical ablation of the salivary glands in adult insects are described.

Biochemical Differentiation in Insect Glands. W. Beermann

<i>Biochemical Differentiation in Insect Glands</i>. W. Beermann

Book notices

IMM'S OUTLINES OF ENTOMOLOGY. 6th edn. Edited by O. W. Richards and R. G. DaviesBIOCHEMICAL DIFFERENTIATION IN INSECT GLANDS. Edited by W. BeermannTHE ECOLOGY OF PESTICIDES. By A. W. A. Brown

Biochemical Differentiation in Insect Glands

Biochemical Differentiation in Insect Glands

The clypeal glands of Mynoglenes and of some other linyphiid spiders

The clypeal glands of three New Zealand Linyphiidae currently placed in Mynoglenes are described, by light, scanning and transmission electron microscopy. Shallow sulci beneath the lateral eyes of both sexes trap secretions which are produced by greatly elongated cells packed radially with respect to a given sulcus, and each voiding its product to the exterior by an individual ductule. The function of the secretion is unknown, although the ultrastructure of the gland resembles that of the defensive glands of many insects, but there is no separate duct cell, and the basal region of each secretory cell exhibits a unique strategy of membrane amplification, which divides the cytoplasm longitudinally into compartments by folds of the plasma membrane, compartments being still further subdivided into “tails”. Patterns of vacuolation observed in various regions of the cytoplasm support the hypothesis that these unusual structures may be concerned with rapid water transport from the haemocoele, and that the cells discharge their contents by a “flush‐out” mechanism. It is shown that male Erigoninae with cephalic specializations have similar clypeal glands, but with cytological profiles (in alcohol‐fixed material) which suggest that special forms of membrane amplification are not present. Glands are absent in female Erigoninae, and in males with unmodified heads. It is suggested that in this latter subfamily the cephalic modifications may serve as presenting surfaces for sexual pheromones.

Cellular Differentiation in a Highly Specialized Insect Secretory Organ

The colleterial glands of insects are accessory reproductive structures which produce secretions that are applied to eggs after fertilization and which serve a number of protective functions. The colleterial glands of lepidoptera are of particular interest in the study of the events of cellular differentiation because they undergo rapid development, generally during the pupal adult transformation, and contain highly specialized cells which produce large amounts of a restricted variety of secretory products. The extreme specialization of these organs facilitates parallel studies of differentiation at the biochemical and morphological level. This communication describes the changes in the ultrastructure of cells which will form the protein-secreting segment of the colleterial gland of the moth Actias luna during the period of transition from the undifferentiated state to the acquisition of secretory ability. An initial stage of general cellular proliferation by mitosis in the presumptive colleterial tissue mass is followed by differentiation of the cells in the absence of further mitosis. Four distinctive cell types are recognized during the phase of differentiation. These types include a chitogenous cell which forms the chitin lining of the main duct, and three cells which cooperate in the formation of a secretory apparatus. Cell A forms two temporary flagella-like structures which assist in the formation of a ductule, which eventually leads from the secretory cell to the main duct. Near the end of the differentiative phase, Cell A degenerates and is phagocitized by Cell B. Cell B becomes the actual secretory element, and acquires cytoplasmic features such as extensive rough endoplasmic reticulum and Golgi apparatus which are associated with synthesis and secretion of protein. The final element, Cell C, remains associated with the ductule which it helps to construct and which traverses its cytoplasm.

Cytodifferentiation in the accessory glands of Tenebrio molitor I. Ultrastructure of the tubular gland in the post-ecdysial adult male.

The tubular accessory reproductive glands of the male mealworm beetle consist of a secretory epithelium surrounded by a thin muscular sheath. Each columnar secretory cell is divisible into three zones: basal which is adjacent to the muscle layer and contains rough endoplasmic reticulum and Golgi, intermediate, which contains endoplasmic reticulum and Golgi zones in the immature gland and is filled with secretory vesicles in the mature gland, and apical. Maturation also involves proliferation and organization of the rough endoplasmic reticulum in the basal and intermediate zone. The process appears to be complete at four days after ecdysis. Parallels with other insect glands and with the mammalian prostate are striking.

Cytodifferentiation in the accessory glands of Tenebrio molitor. III. Fine structure of the spermathecal accessory gland in the pupa

To establish indices for studying the hormonal control of differentiation of the accessory reproductive glands of insects, the ultrastructural development of the spermathecal accessory gland (SAG) of female mealworm beetles has been analyzed. Over the 9 days between adult and pupal ecdysis, the SAG transforms from a stubby sac of columnar epithelium into an elongate cylindrical gland, lined with cuticle, and containing several distinct types of differentiated cells. The first phase of pupal differentiation is one of cell division and overall gland morphogenesis which lasts 3–4 days ; at its close, two populations of cells can be distinguished. One of these populations will produce the cuticular ductules while the other will yield the three-cell secretory units or organules. In the second phase which lasts 2 days, the three cells of each organule become wrapped around one another and then the innermost puts out a pseudocilium and retracts within the next ensheathing cell. In the third phase which lasts 4 days, the cuticles of the axial duct, of the efferent ductule, of the vestibule upon which the ductules converge, and of the end apparatus, are deposited. The ciliary process degenerates, and after ecdysis, the secretory cells undergo peak differentiation.