Peculiarities of ultrastructural organization of the metathoracic ganglion in the locustLocusta migratoria larva

In electron microscopic study of structural organization of the thoracic ganglion of the locust larva of the 1st age (1–2 days after hatching), the data on the structure of motoneurons of the 1st nerve, basal and motor neuropil of the larva were obtained. The effector elements of the larval locust CNS are formed rather early and have the structural plan similar to that in adult insects. However, in the larval motoneurons innervating the flight muscles (longitudinal dorsal muscles, wing depressors) the clearly seen features of immaturity of these nervous elements are revealed. Study of the larval ganglion neuropil has shown that the basal neuropil is morphologically formed sufficiently completely as early as in larvae of the first days after hatching. There are shown longitudinal contacts between axons of the ventral neuropil zone, the presence of axons forming theen-passant contacts as well as the synapses with a heterogeneous set of vesicles in the presynaptic area. The presence of the great number of granular vesicles in the basal neuropil of the locust larva may indicate an important role of catecholamines in the early development of the nervous system in the locust larva.     

Activity pattern of suboesophageal ganglion cells innervating the salivary glands of the locust Locusta migratoria

The salivary gland of the locust, Locusta migratoria, is innervated from the suboesophageal ganglion by two neurones, SN1 and SN2 which innervate the gland via the salivary gland nerve (nerve 7B of the suboesophageal ganglion). In addition, like most other peripheral nerves of the head, this nerve carries on its outer surface axons and neurohaemal terminal ramifications of the so called satellite nervous system, established by a group of neurosecretory cells also located in the suboesophageal ganglion. These superficial collaterals ramify over the nerve from its origin in the head to its terminals within the gland in the thoracic segments.Nerve 7B was recorded chronically in freely moving locusts. Both salivary neurones are active during and shortly before feeding, as defined by continuous rhythmic activity of the mandibular closer muscle (M9). The activity of the salivary neurones, particularly that of SN2, thus resembles that of the satellite neurones as described recently. While SN2 ceases firing at the end of a feeding bout, SN1 continues firing for a short period. Also, SN1 fires short bursts of impulses for a few minutes following the end of a feeding bout. Similar bursts also occur at random intervals during the long-lasting phases between feeding events.Abbreviations SN1 salivary neurone 1 - SN2 salivary neurone 2 - M9 mandibular closer muscle - DUM dorsal unpaired median - LMN labral median nerve     

Moulting of insect tracheae captured by light and electron-microscopy in the metathoracic femur of a third instar locust Locusta migratoria

The insect tracheal system is an air-filled branching network of internal tubing that functions to exchange respiratory gases between the tissues and the environment. The light and electron-micrographs presented in this study show tracheae in the process of moulting, captured from the metathoracic hopping femur of a juvenile third instar locust (Locusta migratoria). The images provide evidence for the detachment of the cuticular intima from the tracheal epithelial cells, the presence of moulting fluid between the new and old cuticle layers, and the withdrawal of the shed cuticular lining through larger upstream regions of the tracheal system during moulting. The micrographs also reveal that the cuticular intima of the fine terminal branches of the tracheal system is cast at ecdysis. Therefore, the hypothesis that tracheoles retain their cuticle lining at each moult may not apply to all insect species or developmental stages.     

Chemo-discriminatory neurones in the sub-oesophageal ganglion of Locusta migratoria

The sub-oesophageal ganglion of Locusta migratoria was searched for neurones responsive to stimulation of the maxillary palps using intracellular recording techniques. Two plant stimuli were used: wheat, a host plant and cabbage, an unacceptable non-host plant. The stimuli were presented to the palp as both intact leaf tissue and as droplets of aqueous solutions of plant extracts. All the sampled neurones that responded to stimulation of the palp also responded to simple mechanical stimulation. However, 25% of the neurones exhibited consistent differences in response to the two plants when presented as both leaf tissue and droplets, strongly suggesting that they also received a chemosensory input. These differential responses most commonly took the form of differences in the duration of cell activity and/or variation in the latency of the onset of response. The receptive fields of differentially responding neurones were confined to the maxillary palp, or at most to the maxillary and labial palps.     

Neuroendocrine control of blood lipids in the locust, Locusta migratoria

In order to determine the best conditions, the influence of various parameters on the haemolymph lipid concentration were studied. These parameters are the age, the sex and the feeding of the animals, the time and the number of the haemolymph sample-taking and the temperature of the locust culture. A large in vivo increase in haemolymph lipid concentration was obtained in locusts which received extracts of the whole CC and of their glandular or neurohemal lobes. Reversely, a decrease in this concentration was obtained in locusts operated 7 days before (cardiacectomy or glandular lobe removal). Moreover the pars intercerebralis extracts increased the level of haemolymph lipids. We conclude that adipokinetic factors are present, both in the glandular lobes of the CC and in their neurohemal lobes. It is likely that the latter partly originate from the pars intercerebralis. Results of allatectomy and injections of corpora allata extracts led to the conclusion that corpora allata contain an adipokinetic factor, the juvenile hormone. and factors that inhibit the haemolymph lipid concentration. Finally, from different injections of neurotransmitters and drugs it is argued that it is mainly octopamine which is involved in the mechanism governing the increase of the level of haemolymph lipids.     

Characterization of cuticular proteins from the migratory locust,Locusta migratoria

Proteins were extracted from the still unhardened (teneral) cuticle of the migratory locust, Locusta migratoria. The proteins are soluble only at extreme pH-values and at low ionic strength, the solubility increases with decreasing temperature. The unhardened cuticle contains approx. 100 different proteins according to two-dimensional polyacrylamide gel electrophoresis. The majority of the proteins are very basic. The basicity and solubility properties of the proteins have necessitated development of modified electrophoretic procedures. The amino acid composition of the bulk protein shows that alanine, proline, glycine, valine and tyrosine constitute two thirds of the total amino acid content and that cysteine, methionine and tryptophan are absent.The proteins have been extracted from various parts of the cuticle and analysed by two-dimensional electrophoresis. Characteristic protein compositions were found for cuticle from the different body parts. Amino acid analyses of these extracts are strikingly similar. The only significant difference is in the glycine-alanine ratio. Cuticles that are destined to become hard are extremely rich in alanine, whereas the flexible parts of the cuticle are enriched in glycine. The results indicate that the proteins of locust cuticle constitute a group of structural proteins different from other known structural proteins.     

The neural control of spermathecal contractions in the locust,Locusta migratoria

The innervation of the spermatheca and demonstration of neural control of spermathecal contractions in Locusta migratoria was illustrated using anterograde and retrograde fills, combined with electrophysiological stimulation and recording. The anterior portion of the spermatheca receives innervation via the receptaculum seminis nerve (N2B2) from two large ventral neurons and one dorsal neuron. All were bilaterally paired and situated in the VIIIth abdominal ganglion. Three ventral bilaterally paired neurons situated in the VIIIth abdominal ganglion also provide innervation to the posterior portion of the spermatheca via the ductus seminalis aperture nerve (N2B3). Six DUM neurons, located in the VIIIth abdominal ganglion, in addition to two centroposteriorly situated DUM neurons in the VIIth abdominal ganglion, are also associated with these two nerves. N2B4 also provides innervation to the posterior portion of the spermatheca. N2B6b is associated with sensory cells identified in the anterior lateral regions of the genital chamber. The spermatheca contracts spontaneously, with peristaltic contractions beginning at the spermathecal sac and continuing along the length of the spermathecal duct. However electrical stimulation of the ventral ovipositor nerve (VON or N2B), receptaculum seminis nerve (N2B2) and the ductus seminalis aperture nerve (N2B3) indicates that contractions are also under neural control. In particular contractions of the spermathecal sac, coil duct and anterior straight duct are initiated via motor projections from the receptaculum seminis nerve (N2B2) and posterior straight duct contractions are controlled by motor input from the ductus seminalis aperture nerve (N2B3). The results suggest that spermathecal contractions of the anterior and posterior portions of the spermatheca are under separate neural control.     

K homeostasis and central pattern generation in the metathoracic ganglion of the locust

Stress-induced arrest of ventilatory motor pattern generation is tightly correlated with an abrupt increase in extracellular potassium concentration ([K⁺]_o) within the metathoracic neuropil of the locust, Locusta migratoria. Na⁺/K⁺-ATPase inhibition with ouabain elicits repetitive surges of [K⁺]_o that coincide with arrest and recovery of motor activity. Here we show that ouabain induces repetitive [K⁺]_o events in a concentration-dependent manner. 10⁻⁵ M, 10⁻⁴ M, and 10⁻³ M ouabain was bath-applied in semi-intact locust preparations. 10⁻⁴ M and 10⁻³ M ouabain reliably induced repetitive [K⁺]_o events whereas 10⁻⁵ M ouabain had no significant effect. In comparison to 10⁻⁴ M ouabain, 10⁻³ M ouabain increased the number and hastened the time to onset of repetitive [K⁺]_o waves, prolonged [K⁺]_o event duration, increased resting [K⁺]_o, and diminished the absolute value of [K⁺]_o waves. Recovery of motor patterning following [K⁺]_o events was less likely in 10⁻³ M ouabain. In addition, we show that K⁺ channel inhibition using TEA suppressed the onset and decreased the amplitude of ouabain-induced repetitive [K⁺]_o waves. Our results demonstrate that ventilatory circuit function in the locust CNS is dependent on the balance between mechanisms of [K⁺] accumulation and [K⁺] clearance. We suggest that with an imbalance in favour of accumulation the system tends towards a bistable state with transitions mediated by positive feedback involving voltage-dependent K⁺ channels.     

沿海蝗区东亚飞蝗产卵选择的适应性

以沿海蝗区南大港水库为研究区域,通过2年野外调查旨在掌握东亚飞蝗Locustamigratoriamanilensis(Meyen)产卵场所的选择。结果表明,飞蝗产卵适宜的植被覆盖度、土壤含盐量和土壤5cm含水量分别为0~30%、0.09%~1.99%和10.0%~20.0%,当植被覆盖度>70%,土壤含水量>30%或含盐量>3%时,不再适合飞蝗产卵。土壤有机质和pH值不是影响飞蝗产卵选择的主要因素。与20世纪50年代的研究结果相比,飞蝗产卵时对土壤含水量和含盐量的耐受范围拓宽,对环境的适应能力增强。     

FMRFamide-like immunoreactivity in the metathoracic ganglion of the locust (Schistocerca gregaria)

Summary The distribution of FMRFamide-like immunoreactivity in the metathoracic ganglion of the locust, Schistocerca gregaria, has been investigated in serial semithin transverse sections with the use of the peroxidase-antiperoxidase (PAP) technique. The topographical distribution of approximately 120 immunopositive neurons was established. Antiserum against bovine pancreatic polypeptide (BPP) stains the same ganglionic cells as FMRFamide-antiserum, yet this staining is largely blocked after preabsorption to FMRFamide. A comparison of these results with those from other studies suggests that there may be more than one type of endogenous RFamide-like peptide.     

Chemical composition of the attachment pad secretion of the locust Locusta migratoria

This study is the first attempt to characterise the chemical composition of the secretion of the smooth pads of the locust Locusta migratoria and to relate this to the composition of the cuticle coverage of the pads and the wings. Gas-chromatography and mass-spectrometry (GC-MS) were the principal techniques used for the characterization of these materials. Secretion droplets were visualised and quantified with the aid of diverse microscopic techniques. The chemical composition of prints is shown to differ from the cuticle coverage, in particular, with respect to the fatty acid distribution: in the secretion, saturated and unsaturated fatty acids with chain lengths between C₁₆ and C₂₀ in both the free form and as glycerides predominate, whereas cuticle coverage contains waxes of long-chained fatty-acids bound to long-chain primary alcohols. The second important difference is the significant amount of glucose and other saccharides found in methanolyzates of the pad fluid. A considerable amount of the amino acids (up to 53%) was detected in the non-volatile portion of the fluid. Data obtained from the shock-freezing, carbon-platinum coating and replica preparation show that the secretory droplets contain nano-droplets on their surfaces. The results lead us to suggest that the pad secretion is an emulsion consisting of lipidic nano-droplets dispersed in an aqueous liquid. According to the chemical composition of the secretion, a high-viscosity of the fluid may be suggested. Presumably, the fluid is a kind of a coupling agent, promoting and strengthening adhesion between otherwise incompatible materials by providing the proximity of contact for intermolecular forces.     

Octopamine metabolism in the cephalic ganglion of Locusta migratoria L.

Octopamine contents in the cephalic ganglia of the locust Locusta migratoria have been determined in male and female late larval and in adult stages. The animals have been pretreated with intra-abdominal administration of p-tyrosine or p-tyramine alone or following the administration of reserpine.1. p-Octopamine levels were higher at the 7th day than at the 5th day in the fourth larval stage. At this stage a significant difference was observed in male and female cephalic ganglia.2. The administration of p-tyrosine and p-tyramine resulted in ganglia.3. The pretreatment with reserpine resulted in an almost complete depletion in p-octopamine.4. This depletion was partially abolished by p-tyrosine or more efficiently by p-tyramine administration.5. Eventually, the p-octopamine levels were considerably decreased by the administration of the decarboxylase inhibitor, R04-4602, of the dopamine β-hydroxylase inhibitor, fusaric acid, and of the false neurotransmitter 6-hydroxydopamine.