Sex pheromone titre in the glands of Spodoptera litura females: circadian rhythm and the effects of age and mating

The present study investigates the effects of age and mating status on the circadian variations of gland sex pheromone titre in female Spodoptera litura Fabricius. Similar to other nocturnal moths, S. litura females exhibit circadian variations of gland sex pheromone contents, with higher levels during scotophase and lower levels during photophase. The sex pheromone titre in the glands peaks during the first scotophase after eclosion and sharply declines afterwards. Higher pheromone contents during scotophase may facilitate female reproductive activities, and the negative relationship between pheromone titre and female calling is likely the result of pheromone release during female calling. Interestingly, the present study demonstrates that mated S. litura females have significantly higher sex pheromone titre in their pheromone glands (PGs) than virgin females. This finding contrasts with all previous studies of other insect species, in which mating generally reduces the sex pheromone titre in female PGs. In S. litura, mating and male accessory gland fluids can suppress female calling behaviours and re‐matings. These results suggest that the suppression of female calling behaviours by mating and male accessory gland fluids may significantly reduce the release of sex pheromones and thus result in higher sex pheromone titre in the PGs of mated females.     

Peculiar salivary glands in a silk‐producing mite Bakericheyla chanayi (Cheyletidae)

This is the first ultrastructural investigation of salivary glands in the family Cheyletidae. In both sexes of Bakericheyla chanayi, paired acinous salivary glands and tubular coxal glands were shown to be united into the common podocephalic system. The secretory portion of the salivary gland includes medial and lateral lobes composed of the five and two cells, respectively, with clearly distinct ultrastructure. The cytoplasm of the cells is occupied by the secretory granules containing fine fibrous material. The fine structure of both cell types suggest a proteinaceous nature of their secretions. A single central process extending from the apical face of each secretory cell passes through the common acinar cavity to enter the conducting duct. A pair of intercalary cells at the base of the conducting duct links it with the secretory portion of the gland. Extending towards the acinar cavity, protrusions of intercalary cells alternate the apical regions of the secretory cells and form with them highly‐specialized contacts characterized by the apical network of microtubules and microfilaments. Two possible ways of secretion are suggested: 1) exocytosis into the acinar cavity and 2) direct passage via the central processes. The detection of axon profiles in the gland body suggests a neural control for the glandular cell function. In tritonymphs, neither secretion nor large lateral lobe cells were observed up to the pharate stage when the lateral lobe undergoes rapid differentiation. The arrangement of the acinous gland is compared to that of other arthropods. Its composition appears to be close to the class three of insect glands. The involvement of the lateral lobe cells in silk production is discussed. J. Morphol. 276:772–786, 2015. © 2015 Wiley Periodicals, Inc.     

Fine structure of the foveae dorsales and foveal glands in the female tick Amblyomma americanum (acari: Ixodoidea: Ixodidae)

The fine structure of the paired foveae dorsales and foveal glands in the unfed female Amblyomma americanum is described and compared with that in other tick species. Each fovea opens to the exterior via pores which lead internally into a single cuticular tube, the pore-tube. This is surrounded by 2–3 epithelial cells. The pore-tube enlarges basally forming a large cavity possessing a cup-shaped cytoplasmic protrusion. The pore-tube cuticular lining extends downward to form an electron-dense, flaplike protrusion bracketing narrow cytoplasmic extensions filled with microtubules. These extensions form a previously undescribed valvelike structure that seems to control the flow of pheromone secretion from the foveal gland to the pore-tube. The single foveal gland lying beneath each pore-tube is composed of 2–3 inner, large, storage cells surrounded by outer, spindle-shaped cells; both types of cells have a characteristic feature of epithelia involved in secretory activity and ion transport. The outer cells extend upward to join the base of the poretube cells by septate desmosomes. A nerve, the foveal nerve, containing axons with neurosecretory vesicles occurs in the vicinity of the foveal gland. The secretory activity of the pheromone glands seems to be partially, if not entirely, under a neural regulation.     

Fine structure of cells specialized for secretion of aggregation pheromone in a nitidulid beetle Carpophilus freemani (coleoptera: Nitidulidae)

The cells that secrete the aggregation pheromone of the male nitidulid beetle Carpophilus freemani are exceptionally large and lie within the body cavity. These secretory cells share many ultrastructural features with cells of other pheromone and defense glands, but they also have several unique features. A deep invagination of the surface of each of these cells acts as the secretory surface for the pheromone. The invaginated surface is highly convoluted and surrounds a narrow cuticular ductule that is connected to the tracheal system. This surface is not covered with microvilli as the comparable surfaces are in other insect secretory cells. Each secretory cell is filled with an abundance of lipid spheres that presumably contain precursors for the pheromone. Examining cells from beetles producing different levels of pheromone showed that sizes of secretory cells are positively correlated with rates of pheromone production. Whereas secretory and ductule cells of other insect glands are usually epidermal cells, these cells of nitidulid beetles represent the first pheromone glands in which oenocytes are believed to have been recruited for pheromone production and tracheal cells have been recruited as ductules for these cells.     

Effect of the pheromone biosynthesis activating neuropeptide on sex pheromone biosynthesis in Spodoptera littoralis isolated glands

The control of Spodoptera littoralis sex pheromone biosynthesis has been investigated with synthetic pheromone biosynthesis activating neuropeptide (PBAN) and different labeled tracers using an in vitro isolated gland system. Responsiveness of the glands to PBAN stimulation was impaired by careless tissue manipulation. The fact that PBAN is active in the isolated gland system suggests that this might be a target organ for this peptide in S. littoralis. As reported previously with Br-SOG extracts and intact females, label incorporation into the pheromone increased in glands treated with PBAN from all the precursors tested. However, the formation of labeled intermediates from d₅E11–14:Acid also occurred in glands incubated in the absence of the peptide, but the amounts of d₅Z9, E11–14:Acid were lower in PBAN treated glands than in controls. These results indicate that PBAN controls pheromone biosynthesis in S. littoralis by regulating the reduction of acyl moieties. © 1994 Wiley-Liss, Inc.     

Morphological characterization of female accessory sex glands of Eupolybothrus fasciatus (Newport) (Chilopoda Lithobiomorpha)

The female reproductive system of Eupolybothrus fasciatus (Newport) (Chilopoda Lithobiomorpha) includes three types of well-developed accessory glands, viz. large glands, small glands, and the periatrial gland. External morphology and the ultrastructural organization of these glands have been investigated by light and electron microscopy. The small and large glands are paired and have coiled ducts that open, respectively, into and externally to the genital atrium. By contrast, the periatrial gland is unpaired and is located on the ventral wall of the atrium into which it opens via several small canals. Ultrastructural features show that all three glands consist of two different types of cells: secretory cells and ductule cells. The secretary cells contain prominent secretory granules and are similar to a class of insect epidermal gland cells (class 3) organized as acini surrounding an extracellular lumen into which microvilli project. The granules, which have different morphological features in each gland, could be responsible for important differential functions such as producing a sexual attractant, providing a coating material that protects eggs laid on the ground, and contributing to a fluid that digests spermatophores. © 1996 Wiley-Liss, Inc.     

A blend of formic acid,benzoic acid,and aliphatic alkanes mediates alarm recruitment responses in western carpenter ants,Camponotus modoc

Formicine ants in distress spray alarm pheromone which typically recruits nestmates for help. Studying the western carpenter ant, Camponotus modoc Wheeler (Hymenoptera: Formicidae), our objectives were to (1) determine the exocrine glands that contain alarm recruitment pheromone, (2) identify the key alarm recruitment pheromone components, and (3) ascertain the pheromone components that are discharged by distressed ants. In Y-tube olfactometer experiments, extracts of poison glands, but not of Dufour’s glands, elicited anemotactic responses from worker ants. Gas chromatographic-mass spectrometric analyses of poison gland extracts revealed the presence of (1) aliphatic alkanes (undecane, tridecane, pentadecane, heptadecane), (2) aliphatic alkenes [(Z)-7-pentadecene, (Z)-7- and (Z)-8-heptadecene], (3) two acids (formic, benzoic), and (4) other oxygenated compounds (hexadecan-1-ol, hexadecyl formate, hexadecyl acetate). Testing the responses of worker ants in Y-tube olfactometers to complete and partial synthetic blends of these compounds revealed that the acids and the alkanes are essential alarm pheromone components. In two-choice arena bioassays, micro-locations treated with synthetic alarm pheromone recruited worker ants. Acids and alkanes were abundant in the poison gland and the Dufour’s gland, respectively, suggesting that the alarm pheromone components originate from both glands. Moreover, alarm pheromone sprays of ants differed in that all sprays contained formic acid but only some also contained alkanes, implying that ants can independently discharge the content of either one or both glands in accordance with the type of distress incident they experience.     

Female pheromone glands in arctiidae (lepidoptera). Evolution and phylogenetic significance

Few papers have been devoted to the female pheromone glands, phylogeny and high-level systematics of the Arctiidae. The diversity of these glands is here interpreted in the light of a revised classification. The presence, in the A8-A9 intersegmental membrane, of one or two, distinctly invaginated (‘saccular’), dorsal glands is a characteristic derived trait of the Arctiidae. Lithosiinae typically have an unpaired dorsal gland, anteriorly provided with a pair of short lobes. Non-lithosiine arctiids form a monophyletic group, in which the gland lobes are primarily very long. Several lineages can be characterized by the shape of their dorsal glands, notably the Ctenuchinae (inclusive of Euchromia), the Pericopinae and the Arctiini. Pheromone production is a well-established function of these dorsal glands, while the ventral, intersegmental ‘pouches’ observed in certain taxa may not be pheromone-producing structures. The Thyretini (here allocated to Syntominae) possess ventral saccular glands that bear a marked resemblance to the dorsal pair.     

Semiochemistry of aposematic seed bugs

(E)-2,7-Octadienyl acetate and (E)-2-octenyl acetate (1:10 by volume) were identified as a pheromone attractive to both sexes of the lygaeid bug, Tropidothorax cruciger. In a parallel investigation of Neacoryphus bicrucis (Lygaeidae), (E,E)-2,4-hexadienyl acetate and phenethyl acetate (≈9:1) were identified from males, and found attractive to both sexes of adults in the field plus a tachinid fly parasitoid of the bugs. In N. bicrucis, the pheromone was clearly shown to come from the tubular accessory glands of the metathoracic scent gland; this evidence, plus earlier literature reports for other species, indicate that male lygaeids are the pheromone emitters. In another lygaeid, Oncopeltus fasciatus, 2-isobutyl-3-methoxypyrazine was identified in the cardiac glycoside-laden fluid sequestered from milkweed hosts and expelled by these bugs when they are attacked. Alkyl methoxypyrazines are warning odorants associated with poisonous insect secretions, and their presence in O. fasciatus indicates that the plant-derived chemical defense of lygaeines is more elaborate than previously appreciated.     

Ultrastructural cytochemistry of the sex pheromone glands of Lutzomyia cruzi male sand flies (Diptera: Psychodidae: Phlebotominae)

The sex pheromone glands of Lutzomyia cruzi male sand flies (Diptera: Psychodidae) were analyzed by cytochemical techniques. In adult males, the epithelium at the fourth abdominal tergite is modified into a glandular epithelium, with large columnar gland cells located side by side. The gland cell cytoplasm contains a large number of mitochondria and peroxisomes, the latter with positive (electron-dense) reaction for catalase, a typical peroxisomal enzyme marker. The gland cell cytoplasm also contains a central vacuolated area, with a large number of electron-lucent vacuoles, not limited by a unit membrane. In well-preserved preparations such vacuoles present a homogenous and slightly electron-dense content, typical of lipid droplets. Indeed, incubation of the tergites with imidazole-buffered osmium tetroxide (to detect lipids) resulted in positive reaction in these vacuoles, as well as in between the microvilli of the gland cells. Use of the osmium–potassium iodide (Os–KI) technique allowed to demonstrate the presence of several endoplasmic reticulum (ER) profiles, as expected in secretory cells. Our data suggest that ER, lipid droplets and peroxisomes are involved in the sand fly pheromone biosynthesis.     

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

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

A sophisticated,modular communication contributes to ecological dominance in the invasive ant <Emphasis Type="Italic">Anoplolepis gracilipes</Emphasis>

The ecological success of ants is founded on cooperative behaviour and a well functioning communication. Particularly invasive ants are able to act highly cooperatively, out-compete other species, and become ecologically dominant. Since ant communication is to a large extent chemical, we investigated the pheromone functions involved in foraging and alarm behaviour of the invasive tropical formicine Anoplolepis gracilipes. Our results suggest that long-lasting orientation cues are located in hindguts, while Dufour glands contain short-term attractants that trigger an effective recruitment. Poison gland effects were intermediate between hindgut and Dufour gland in terms of orientation, attraction and longevity. In contrast to the other pheromone sources, mandibular glands have a repellent effect and are most likely involved in alarm behaviour. Taken together, the pheromone glands of A. gracilipes contain functionally distinct signals with considerable differences in persistence. In this respect, its communication is exceptional in formicine ants. A strikingly similar communication system was previously detected in Paratrechina longicornis, another opportunistic and invasive formicine ant. Based on these similarities and the differences compared to non-invasive formicine ants, we discuss the role of chemical signals for the coordination of efficient foraging. We conclude that a sophisticated communication system can contribute significantly to ecological dominance and invasive success, in concert with other well known traits.     

Development of functionally competent cabbage looper moth sex pheromone glands

Unlike some moths, pheromone production in Trichoplusia ni is not regulated by a pheromone activating neuropeptide. Rather, competency to produce pheromone apparently is linked with changes in the ecdysteroid titer that occur late in metamorphosis. In contrast to adult pheromone glands, glands from pharate adults 2 days before eclosion were non-competent, and (1) had undetectable levels of the pheromone, (Z)-7-dodecenyl acetate, and pheromone-specific intermediates, (2) showed little or no conversion of radiolabeled substrate to product in enzyme assays of fatty acid synthetase, Δ11 desaturase, and acetyltransferase, and (3) failed to incorporate radiolabeled acetate into pheromone in gland culture. Glands 1 day before adult eclosion exhibited low titers of pheromone and the intermediate, (Z)-11-hexadecenoate, and showed low levels of radiolabeled acetate incorporation into pheromone in gland culture. By the time of adult eclosion, the gland was fully competent. Precocious development of pheromone gland competency was induced by removing the head and thorax from pupae 2 days before adult eclosion. This effect appears to result from the reduction of ecdysteroid, since it was blocked by the administration of 20-hydroxyecdysone. This ability to manipulate the development of the pheromone gland was restricted to a critical period, since removal of head and thorax from younger pupae did not induce pheromone gland competency, and administration of 20-hydroxyecdysone to older pupae did not block its onset. In addition to differences in competency, early pharate and adult glands exhibited dissimilarities with respect to (1) the types of proteins synthesized in gland culture, and (2) the types of proteins translated from mRNA in vitro.     

The development, structure and function of the mandibular glands of Blaberus craniifer burm. (Dictyoptera Blaberidae)]

The mandibular glands of Blaberus craniifer are examined by histochemical, electrophoretic, thin-layer chromatography and electron microscopical techniques. These glands are known to secrete a volatile aggregative pheromone. The gregarious behaviour increases during insect development and is maximal in imagos. Each gland is composed of a bundle of secretory cells with efferent ductules which arise in a common duct. Secretory cells contain a myeloid secretion more abundant in imagos than in larval stages. Histochemical and electrophoretic criteria show that the myeloid product is made up of a mixture of glycoproteins. A lipidic component is also present in the secretion; its ultrastructural localization remains to be elucidated. Cytological features are in agreement with the gregarious behaviour of cockroaches. Detailed structure and functional interpretation are also discussed.     

Quantitative studies on the development of the bronchi and bronchial glands of the pig from birth to maturity

Cross-sectional areas of bronchi and bronchial glands of pigs aged from 1 day to 10 months were measured using image analysis. Growth of the bronchial glands was slow for the first month of life, reached a maximum between 1 and 3 months, and slowed again after 5 months. Mucous gland sizes fell into two groups, one included the apical, cardiac and accessory lobes, the other the diaphragmatic lobes. From birth to maturity the percentage increase in mucous gland area of all lobes was very similar. For the anterior lobes, mucous glands and bronchial lumina grew in direct proportion to each other. Up to 1 month of age the bronchial lumina of the diaphragmatic lobes grew but the glands did not. Later, glands and lumina grew in direct proportion. From birth to maturity the percentage increase in bronchial cross-sectional area was similar for all lobes.     

Morphology of the foveal glands and foveae dorsales in male Hyalomma truncatum and Rhipicephalus evertsi mimeticus ticks (Acari; Ixodidae) before and during feeding

The ultrastructure of the foveae dorsales and foveal glands in unfed and attached male Hyalomma truncatum and Rhipicephalus evertsi mimeticus ticks was studied. Both species are provided with a paired foveal gland system, which is similar in unfed as well as in attached ticks. This gland system consists of the fovea dorsalis with pores and pore tubes as the external part, the foveal neck zone as a link between the fovea dorsalis and the lobes of the gland and the bulbous lobes as the innermost part. The fovea dorsalis is located on either side of the dorsal midline in the midsection of the body and appears as a roundish plate containing 15±6.5 and 21±7 slit-like pores in R. evertsi mimeticus (n=210) and H. truncatum (n=210), respectively. Each pore leads into a cuticular lined channel containing a pore tube. Below each fovea, the foveal neck zone is located within a groove of the cuticle and consists of the termini of the pore tubes which enlarge basally to form a cup-shaped ampulla each. Furthermore, secretory lobes are located below the foveal neck zone. Each lobe consists of secretory cells and a central excretory duct which leads into the ampulla. The ducts are lined with microvilli. The secretory cells contain numerous vesicles of varying size with one or more granules. In male ticks of both species the secretory lobe cells remained unchanged in size, structure and granule content irrespective of whether they were unfed or attached for up to 30 days. Axons occur in the fascicles between the secretory lobe cells containing numerous neurosecretory vesicles. A possible role of the foveal glands in the production of pheromones is hypothesized.     

褛裳夜蛾的交配行为及雄蛾对性腺提取物的反应节律

详细观察了褛裳夜蛾成虫的交配行为,利用风洞、触角电位技术研究了雄蛾对性腺提取物的反应节律,通过林间诱蛾试验进行了验证,旨在为褛裳夜蛾性信息素的精确提取及性信息素组份分离、鉴定提供依据。研究结果表明:成虫的求偶、交配行为均发生在暗期,有一定的节律性:雌蛾在羽化3d以后开始求偶,1周左右表现最为强烈,3-4日龄雌蛾在暗期4-6h开始求偶,最大求偶率在暗期6-8h;5-9日龄在进入暗期就开始求偶,最大求偶率出现在暗期4-6h。风洞试验表明,3-7日龄的雄蛾对性腺提取物均有明显的性行为反应,5日龄雄蛾在暗期4-6h对性腺提取物的反应最为强烈。3-6日龄的成虫在暗期4-6h开始交配,而7-8日龄的成虫于暗期2-4h开始交配,6日龄的成虫交配率最高,交配高峰在暗期4-8h。雄蛾对性腺提取物的触角电位反应也有一定的节律性:雄蛾对4日龄雌蛾性腺提取物开始有电生理反应,对6-7日龄暗期5h性腺提取物反应最为强烈。林间诱蛾试验测定了性腺提取物的引诱活性,7日龄雌蛾性腺提取物林间诱蛾量最高,引诱高峰在暗期4-6h,该结果也验证了褛裳夜蛾雄蛾对性腺提取物的反应节律。     

Mandibular glands of male European beewolves, Philanthus triangulum (Hymenoptera, Crabronidae)

Males of a solitary digger wasp, the European beewolf, Philanthus triangulum, possess large mandibular glands that have been reported to produce a scent marking pheromone. We analysed the morphology and ultrastructure of these glands using light microscopy as well as scanning and transmission electron microscopy. The paired glands are located laterally in the head and each side consists of a larger and a smaller part. Both parts possess a collecting duct each with distinct openings at the mandible base. However, the collecting duct of the larger part is additionally connected to the pharynx through a lateral extension. The collecting ducts are bordered by a monolayered epithelium lined with cuticle that exhibits conspicuous ramified protuberances. About 1400 acini consisting of class 3 gland cells surround the ducts and are connected to them through conducting canals. The main components in the cytoplasm of these gland cells are mitochondria, well-developed smooth endoplasmatic reticulum, and electron lucent vesicles suggesting a high secretory activity. The connection between the large gland parts and the pharynx suggests that the secretion of the mandibular glands might not only be delivered directly onto the mandibles but might also be transported to and stored in the postpharyngeal gland.     

Morphology of female sex pheromone gland in the horse chestnut leafminer Cameraria ohridella (Lep., Gracillariidae)

Abstract: The internal and external morphology of the female sex pheromone gland in Cameraria ohridella Deschka & Dimic, an European pest on Aesculus hippocastanum L., has been investigated by histological and electron microscopic techniques. The gland consists of a single layer of modified epidermal cells in the dorsal part of the intersegmental membrane between the eighth and ninth abdominal segments and laterally extends to the posterior apophyses. The epithelium contains large columnar- and cone-shaped cells with basally situated nuclei. The cuticle, which covers the glandular region, has a wrapped appearance and is divided into a hyalin and thickened endocuticle and a thin outer epicuticle: it considerably expands when the gland is protruded and provides a sufficiently large surface for evaporation of the pheromone. The cuticle does not show any orifices of pore channels. In the retracted position, the gland is folded within the body cavity of the seventh and eighth abdominal segments but is exposed to the environment by extension of the abdominal tip along with female calling. In virgin females, pheromone glands are well developed at least within the first days after eclosion; if copulation occurs, glandular epithelia degenerate soon. According to the current classification, the glandular type of C. ohridella most easily is consistent with eversible dorsal scent folds that are widely distributed amongst diverse taxa of Lepidoptera. However, this is the first report on the morphology of pheromone glands in the Gracillariidae.