External sensilla of the locust abdomen provide the central nervous system with an interganglionic network

External mechanoreceptors and contact chemoreceptors on the cuticle of the sixth abdominal segment of locusts have divergent primary projections of their sensory neurons that form arbours in the segmental and anterior abdominal ganglia. Homologous interganglionic projections from adjacent segments converge in the neuropile of each abdominal ganglion. Of the contributing types of sensilla, three were previously unknown for locust pregenital segments: tactile mechanosensory hairs with dual innervation, external proprioceptors of the hairplate type covered by intersegmental membranes and single campaniform sensilla that monitor cuticular strain in sternites and tergites. In general, interdependence of motor coordination in the abdominal segments is based on a neural network that relies heavily on intersegmental primary afferents that cooperate to identify the location, parameters and strength of external stimuli.     

Bursicon release and activity in haemolymph during metamorphosis of the cockroach,Leucophaea maderae

Bursicon activity first appears in the haemolymph of the cockroach, Leucophaea maderae, early in ecdysis as the old cuticle splits and separates over the thorax. Hormonal activity reaches high levels in the haemolymph before ecdysis is complete and remains so for about 1·5 hr, with a gradual decline and disappearance by 3 hr. The sensory mechanism controlling bursicon release is located in the thorax and appears to be stimulated as the ecdysial split widens for emergence of the thorax. If the abdomen is isolated before this time no tanning of abdominal cuticle occurs, while the isolated thorax proceeds to tan. Therefore the thoracic ganglia seem to be a site of release for bursicon. Release of the hormone from abdominal and head ganglia may also occur after neural stimulation from the thoracic system. Bursicon activity was found in all ganglia of the central nervous system and the corpora cardiaca-allata complex. Removal of the old cuticle prior to the start of ecdysial behaviour does not result in tanning of the new cuticle. However, if the old cuticle is removed after the insect begins to swallow air in preparation for ecdysis, then the new cuticle tans. Mechanical prevention of ecdysis and later removal of the old cuticle also does not result in tanning of the new cuticle. Therefore, shedding of the old cuticle only activates the release of bursicon in conjunction with other normal ecdysial events.     

棉铃虫性外激素分泌腺的研究

棉铃虫Helicoverpa armigera Hubner雌蛾的性外激素分泌腺是一个完整的上皮环,位于第八、九腹节之间。羽化2天雌蛾的腺体细胞方形,比未分化的上皮细胞大。腺体折皱,表面密布小毛,小毛无孔。表皮可分二层：上表皮和内表皮。上表皮致密,较薄,厚度均匀。内表皮厚度有变化,较厚,由12-14层呈螺旋状排列的几丁微丝组成,有上皮丝穿人,构成孔道。顶部细胞膜组成微绒毛,底部细胞膜有内折。细胞质内有粗面内质网,光面内质网,高尔基氏复合体、脂肪滴、糖原及线粒体等细胞器。大的细胞核位于中下部。     

Correlated changes in mechanical properties of the intersegmental membrane and bonding between proteins in the female adult locust

When the female locust ecdyses into the adult instar the intersegmental membranes which will extend when the female digs the oviposition hole are stiff and inextensible. Extensibility of the membranes develops later, and is under the control of the corpus allatum: allatectomy prevents the development of extensibility. The difference in extensibility and stiffness of the membranes before and after sexual maturation can be accounted for as a change in the bonding in the protein matrix of the cuticle. Electrophoretic analysis of the cuticular proteins dissociated by SDS shows that there are five major proteins in the cuticle, and that these do not change when the membrane becomes extensible. The differing responses of the two states of the cuticle to sequential extraction in water, 0·5 M KCl, 7 M urea, and 1·0 M NaOH at 60°C suggest that the change is one of reduction in hydrogen bonding. Simple calculations on mechanical data suggest that in the unstretchable state there is one interchain bond every 370 or so amino acid residues. This may allow sufficiently specific site definition for an enzyme to be involved in the breakdown of hydrogen bonding. An E.M. of a possible enzyme package in the cuticle is presented.     

Les variations de l''architecture dans la cuticule abdominale chezTenebrio molitor L. (Ins. Col.)

The ultrastructure of the adult abdominal cuticle of Tenebrio is described and special attention is given to the intersegmental zone in which the cuticle presents several architectural types, i.e. helicoidal, preferred and 'plywood' cuticle (Neville's terminology). This architectural polymorphism of the adult cuticle contrasts with the uniformity of larval and pupal cuticle architecture, which is entirely helicoidal.     

Regional differences in the developing foreleg of Drosophila melanogaster

We transplanted imaginal disks of Drosophila melanogaster from larvae of the second half of the third larval instar into prepupae. Disks from the youngest donors differentiated bristles of only the distal segments of the leg. These disks also produced unusually large areas of cuticle that had no bristles. Disks from older donors differentiated bristles of more proximal segments and the area of cuticle with no bristles was reduced. To account for the regional variation in these results, there must be regional differences among the prospective leg cells at some time during the period from the second half of the third larval instar to the end of adult bristle differentiation. We asked whether prospective distal cells were more advanced than prospective proximal cells during bristle differentiation. We estimated when bristle precursor cells undergo their final cell divisions by heavily irradiating prepupae and pupae. We assumed that cells that were insensitive to the radiation had completed their cell divisions. The distal segments were the first to have insensitive bristles. Most leg bristles became insensitive between 12 and 18 hr after pupariation. The tarsus had a larger proportion of its bristles insensitive than the femur at 15 hr after pupariation. We also investigated when bristle-forming cells begin elongating their bristle shafts. We used the length of bristle rudiments as an indicator of when elongation is initiated. At 35 hr after pupariation, bristle rudiments of distal segments were two to three times longer than bristle rudiments of proximal segments. We discuss how these intersegmental differences observed during bristle differentiation can account for the regional variation in response of discs transplanted into older hosts. However, we do not exclude the possibility that regional differences among cells of the leg tissue exist at stages earlier than the time of bristle differentiation.     

The identification of an age- and female-specific putative PBAN membrane-receptor protein in pheromone glands of Helicoverpa armigera: possible up-regulation by Juvenile Hormone

The present study was designed to determine the age and female specificity of a membrane protein that binds to a pheromone biosynthesis activating neuropeptide (PBAN) ligand and to elucidate the effect of Juvenile Hormone (JH) on binding as well as pheromone activation. The precise age at which developing adult females of Helicoverpa armigera begin to respond to PBAN was determined. PBAN activates in vitro pheromone biosynthesis as well as its intracellular second messenger, cAMP, only in intersegments of newly emerged adult female pheromone glands (i.e. 1-day-old females). An increase in response was observed in 2-day-old females. Intersegments of female pupae and the homologous tissues of adult males do not respond to PBAN. However, in the presence of Juvenile Hormone II (JH II) PBAN induced a response in females, 1 day before emergence (pharate females), but not in younger female pupae. This phenomenon was also observed after topical applications of the JH analog fenoxycarb (FX). In addition the response to PBAN by intersegments of FX-treated emerged adults increased significantly to the level of 2-day-old females. JH II also stimulated the level of incorporation of (35)S-labelled amino acids in female pupae into membrane proteins that are typical in adult intersegments. Using a photoaffinity-biotin labelled PBAN analog we demonstrate specific binding of a membrane protein (estimated MW: 50 kD) in adult females. This binding was not detected in female pupae 3 days before emergence. However, in such female pupae specific binding of the 50 kD protein by the photoaffinity-biotin labelled PBAN analog was induced after JH II or FX treatments thereby providing evidence that JH may up-regulate this putative receptor protein.     

Physiological Mechanisms of Pheromonostatic Responses: effects of Adrenergic Agonists and Antagonists on Moth (Helicoverpa armigera) Pheromone Biosynthesis

The adrenergic agonists octopamine, tyramine and clonidine inhibited the normal pheromonotropic action due to PBAN (pheromone biosynthesis activating neuropeptide) in incubations of intersegmental tissues that are situated between the 8th and 9th abdominal segments of the moth ovipositor tip. This inhibition was reversed in the presence of the adrenergic antagonists phentolamine, yohimbine and chlorpromazine. Incubations of 8th segments alone, which do not produce pheromone, resulted in elevated levels of intracellular cAMP in the presence of octopamine. The physiological significance of this phenomenon is unclear. However, clonidine (an alpha(2) selective agonist) did not duplicate octopamine stimulation of intracellular cAMP in 8th segment cultures. In intersegmental membrane cultures clonidine successfully duplicated the octopamine inhibition of both pheromone and intracellular cAMP production. The physiological significance of octopaminergic receptors mediating the inhibitory response of intersegments was investigated by experiments in vivo. When PBAN was injected into photophase females the normal pheromonotropic activity due to the injected PBAN dropped after 2h. In the presence of clonidine, normal peak stimulatory levels were never attained and a faster decline was observed. Clonidine also inhibited the pheromonotropic response of 24h-decapitated females to PBAN. Adrenergic antagonists successfully reversed the inhibitory effect of clonidine in decapitated females, but did not reverse the effect of clonidine in photophase females. In addition, when clonidine was injected into female moths during the scotophase normal peak pheromone titers were reduced although no effect on calling behavior was observed. Copyright 1997 Elsevier Science Ltd. All rights reserved     

Degeneration of insect intersegmental muscles: electrophysiological studies of populations of fibres

Several parameters were observed during the degeneration of the intersegmental muscles of moths. Within 5 hr after the emergence of the moth, capacitance of the fibres decreases 70 per cent, and resistance begins to climb, the latter reaching a maximum value approximately 300 per cent that at the time of emergence, at 20 hr. The loss in muscle mass is detectable approximately 3 hr after emergence, but the muscle remains fully contractile for at least 10 hr; and intracellular depolarization can elicit localized contractions for another 5 hr. Motor end plates remain potentially capable of function throughout this period. The changes in membrane properties represent the earliest known physiological manifestations of lysis.     

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.     

Sex pheromone gland of the female European corn borer moth,Ostrinia nubilalis (Lepidoptera,Pyralidae): ultrastructural and biochemical evidences

The sex pheromone gland of the female European corn borer moth, Ostrinia nubilalis was studied using light and electron microscopy. The pheromone gland is formed by hypertrophied epidermal cells at the mid-dorsal region of the intersegmental membrane between abdominal segments 8 and 9/10. Active glandular cells contain extensive apical membrane foldings, a single nucleus, many free ribosomes, numerous mitochondria, microtubules and lipid droplets. Smooth endoplasmic reticulum is scanty. In young moths, the glandular cells are smaller in size, the microvilli at the apical membrane are poorly developed and the cytoplasm contains fewer mitochondria, microtubules, and no lipid droplets. The surrounding unmodified epidermal cells are small cuboidal or squamous cells. These cells have ill-defined apical membrane foldings and do not contain lipid droplets in the cytoplasm and the overlying cuticle. Fatty acids analyses revealed the presence of the sex pheromone components, (E)-11-tetradecenyl acetate, and their immediate precursors, methyl (E)-11- and methyl (Z)-11-tetradecenoate, only in the dorsal portion of the cylindrical intersegmental membrane. Results of the present study show that the sex pheromone gland of O. nubilalis is restricted to the dorsal aspect of the intersegmental membrane between segments 8-9/10 and is not a ring-gland.     

Periodic abdominal pumping supports leg development during metamorphosis in tenebrionid beetle Zophobas atratus

Rhythmic abdominal pumping movements in a pupa of giant mealworm beetle Zophobas atratus caused large hemolymph pressure pulses of approximately 20 mmHg. The abdominal pumping movements were completely blocked by transecting the ventral nerve cord (VNC) between the first and second abdominal ganglia. Transection of the VNC until 2 days after pupation caused a developmental defect of adult legs: morphogenesis of the tibial and tarsal segments was severely retarded, and the segments remained covered with a thick pupal cuticle. The developmental defect was rescued by artificially inducing rhythmic abdominal bending for 3 days after transection of VNC. Blocking of the abdominal pump did not increase the amount of water loss during the pupal period. The transplanted tibial segments lacking active tracheal ventilation could form a thick adult cuticle. The results suggest that abdominal pumping movements during the pupal period support the development of adult legs by facilitating hemolymph circulation.     

The integument of the Queensland fruit fly,Ddacus tryoni (Frogg.)

Summary During the pupal stage of Dacus tryoni, the hypodermis of the larva is replaced by an imaginal generation of smaller cells. The hypodermal cells of the tergal glands on the fifth abdominal segment of the adult were examined with the electron microscope; they contain slender, membrane-limited bundles of hollow wax filaments that traverse the cuticle in branched pore canals. Outside the glandular areas, the pore canals are narrower. The cuticle of the adult undergoes its greatest increase in thickness soon after emergence; it becomes sclerotized gradually. No epicuticle was detected with either the light or electron microscopes.Early in adult development, bristles are formed over the general surface of the terga. Most of these are innervated by single, bipolar nerve cells, and have more or less enlarged trichogen cells that appear to secrete wax through pore-plates in the cuticle. The bristles in different regions of the abdomen range in function from pure sensory receptors to pure secretors. The sensory bristles on the tergal glands were examined with the electron microscope.For assistance with the electron microscopy, I thank Mr. Tony Webber and Miss Ann Miller of the Electron Microscopy Unit at Sydney University. — Supported by a C.S.I.R.O. Junior Post-Graduate Studentship.     

粘虫性信息素分泌腺的超微结构

对粘虫Ｍｙｔｈｉｍｎａ ｓｅｐａｒａｔａ雌蛾性信息素分泌腺的位置及结构进行了光学显微镜、扫描电镜。透射电镜的观察，结果表明：粘虫性信息素分泌腺位于腹部末端第８－９节节间膜腹面。求偶时，伸出节间膜，为一白色的囊泡。腺体表面分布着饱满的锥状体。羽化后５天未交尾雌蛾，腺体细胞呈单层排列，中央细胞为柱状，细胞核为椭圆形。细胞与细胞间有明显的胞连接，细胞基底膜基褶较高，质膜上，分布着微绒毛，并与内表皮连接，内表皮之上含有多层几丁质，外角质层染色较深。细胞质中含有空泡，线粒体、脂质粒、糖原及粗面内质网。了解粘虫性信息素分泌腺的位置形态结构，对了解性信息素合成和释放的时辰节律，改进性信息素的提取、分离、鉴定是有意义的。     

Determination of the pheromone-producing region that has epoxidation activity in the abdominal tip of the Japanese giant looper, Ascotis selenaria cretacea (Lepidoptera: Geometridae)

The epoxydienyl sex pheromone of Ascotis selenaria cretacea can be detected only within a rod-like abdominal tip (RAT) of the female. To clarify which part of the RAT is the sex pheromone-producing region, the RAT was morphologically divided into three sections, defined positionally from the abdomen as sections A, B, and C. GC-MS measurements clearly showed that the sex pheromone compound levels in section B were four times greater than those of the other sections. Microscopic dissection analysis revealed that section B consists of four tissues: rectum, oviduct, musculature, and intersegmental membrane. GC-MS analysis of the individual tissues revealed that approximately 90% of the sex pheromone in section B is localized in the intersegmental membrane. A cell layer was found in the intersegmental membrane after staining with propidium iodide. Furthermore, incubation of tissues dissected from section B with a deuterated trienyl pheromone precursor revealed that the labeled epoxy pheromonal component was detected exclusively in the intersegmental membrane. We have determined that the sex pheromone-producing region of A. s. cretacea is on the terminal side of the intersegmental membrane located between the 8th and 9th abdominal segments.     

Regional differences in degree of resilin cross-linking in the desert locust, Schistocerca gregaria

Various cuticular regions from the desert locust, Schistocerca gregaria, were quantitatively analyzed for two cross-linking amino acids, dityrosine and trityrosine, characteristic constituents of the rubberlike cuticular protein, resilin. These amino acids were found in all regions of cuticle investigated, but in widely varying amounts. In fully mature adult locusts the largest amounts of di- and trityrosine were obtained from the prealar arms and wing-hinges, structures possessing long-range elasticity and being involved in energy storage in the flight system. In structures where deformations tend to occur more slowly, such as the clypeo-labral springs and tracheae, di- and trityrosine are less abundant. In sclerotized cuticle from femur and tibia, as well as in cornea and in the highly stretchable intersegmental membranes of mature females, they are only found in trace amounts and are probably unrelated to elasticity. The trityrosine-to-dityrosine ratio in the various cuticular regions vary from nearly equal amounts of the two amino acids to about ten times more dityrosine than trityrosine, indicating that the regions differ in degree of cross-linking; the tracheal wall is the material with the highest trityrosine-to-dityrosine ratio. In some cuticular regions the ratio increases during maturation from newly moulted (teneral) adults to reproductively active locusts; the most pronounced increase was observed for the wing-hinges, and only a small increase was observed for the abdominal tergal plates. In most cuticular regions in fifth instar locust nymphs the contents of di- and trityrosine corresponded to the contents measured for the adult cuticular regions, but only trace amounts of the two amino acids were obtained from the region of the nymphal wing base which corresponds to the wing-hinge containing cuticular region in adult locusts.     

The imaginal ecdysis of the desert locust, Schistocerca gregaria.

ABSTRACT. The newly-emerged adult locust stretches its soft new cuticle into its adult shape and size, and at the same time caters for its ventilatory demands, by means of a pattern of behaviour, the 'expansional motor programme'. This programme begins after emergence and persists until about an hour after wing-folding, during which time its period changes in a predictable manner. In the post-expansional period, abdominal dorsoventral movements occur that may serve to deflate the gut and to fill the air-sacs, and the mandibles are periodically ad ducted.     

Pattern formation inDrosophila melanogaster: The effects of mutations on polarity in the developing leg

Summary The effects of the mutations eyeless dominant (ey ^D) and shibire (shi) on bristle pattern in the legs ofDrosophila melanogaster were examined. Both mutations cause gaps in the intersegmental membranes which separate leg segments and often alter the position of these membranes. It was observed that pattern disturbances including reversed bristle polarity and duplication of structures such as sex combs and transverse rows were associated with defects in the intersegmental membranes. The alterations in bristle polarity and most of the duplication of structures could be accounted for by a segmentally reiterated gradient in the legs which controls bristle polarity and which requires the integrity of the intersegmental membrane. A computer simulation of this gradient model was devised which accounted for the observed results. The possible role of cell death as a cause of the gaps in the intersegmental membrane and of some of the pattern disturbances was examined.     

Segment-specific retention of a larval neuromuscular system and its role in a new, rhythmic, pupal motor pattern in Manduca sexta

At pupation in Manduca sexta, accessory planta retractor muscles and their motoneurons degenerate in segment-specific patterns. Accessory planta retractor muscles in abdominal segments 2 and 3 survive in reduced form through the pupal stage and degenerate after adult emergence. Electromyographic and electrophysiological recordings show that these accessory planta retractor muscles participate in a new, rhythmic `pupal motor pattern' in which all four muscles contract synchronously at ∼4 s intervals for extended bouts. Accessory planta retractor muscle contractions are driven by synaptic activation of accessory planta retractor motoneurons and are often accompanied by rhythmic activity in intersegmental muscles and spiracular closer muscles. The pupal motor pattern is influenced by descending neural input although isolated abdominal ganglia can produce a pupal motor pattern-like rhythm. The robust pupal motor pattern first seen after pupal ecdysis weakens during the second half of pupal life. Anemometric recordings indicate that the intersegmental muscle and spiracular closer muscle component of the pupal motor pattern produces ventilation. Accessory planta retractor muscle contractions lift the flexible abdominal floor, to which the developing wings and legs adhere tightly. We hypothesize that, by a bellows-like action, the accessory planta retractor muscle contractions circulate hemolymph in the appendages. Morphometric analysis shows that dendritic regression is similar in accessory planta retractor motoneurons with different pupal fates, and that accessory planta retractor motoneurons begin to participate in the pupal motor pattern while their dendrites are regressed. Accepted: 29 March 1998     

Infrared spectroscopy of locust extensible intersegmental cuticle and its components

Infrared spectroscopy shows that the protein in the extensible intersegmental membrane of the adult female locust is mainly in random coil conformation, 35% is α-helical, almost none is in the β-sheet form. A slightly slower rate of deuteration of the NH groups in the immature cuticle is in agreement with biochemical data that the unstretchable immature cuticle is more tightly hydrogen bonded.