Flight fuel related differences between solitary and gregarious locusts (Locusta migratoria migratorioides)

Abstract. Flight fuel relations of crowded and isolated Locusta migratoria migratorioides were investigated in younger (12–16 days after fledging) and older (27–30 or 27–32 days after fledging) adult males.No phase polymorphism dependent differences were found in resting haemolymph carbohydrate levels of the younger locusts.In the older age group, resting haemolymph carbohydrate levels were slightly though significantly higher in the isolated than in the crowded locusts.Injection of various doses of synthetic adipokinetic hormones (AKHs) did not induce marked changes in haemolymph carbohydrate levels and no differences were found between crowded and isolated locusts.A 30 min flight led to the same decrease in haemolymph carbohydrate levels of isolated and crowded locusts, 43.3% and 44.6% of the resting levels, respectively.We concluded, therefore, that the results do not seem to indicate that isolated locusts rely more heavily on carbohydrates as flight fuel than crowded locusts.Hyperlipaemic responses to flight were less intense in isolated than in crowded locusts, but phase polymorphism dependent differences in flight-induced increase of haemolymph lipid levels were not parallel in 12–16-day-old and 27–32-day-old males.In the younger age group the difference was mainly in the duration of flight needed to induce full response which appeared already after 20 min of flight in the crowded locusts, but only after 45 or 60 min of flight in the isolated ones.In contrast, the older isolated locusts showed markedly lower haemolymph lipid elevations than the crowded locusts even after 30, 45 or 60 min of flight.The hypothesis is forwarded that isolated locusts have a rather coarse adipokinetic strategy focused on a single long-distance migratory flight, whereas gregarious locusts possess a fine adipokinetic balance for reiterative migratory flights and saving fuel reserves for unpredictable long-distance migrations.     

Changes in the auditory system of locusts (Locusta migratoria and Schistocerca gregaria) after deafferentation

Deafferentation experiments during postembryonic development show morphological and/or physiological changes of receptor fibers and of identified auditory interneurons in the CNS of the locusts Locusta migratoria and Schistocerca gregaria after unilateral ablation of one tympanic organ either in the larva or the adult animal.

The effect of azadirachtin on the midgut histology of the locusts, Schistocerca gregaria and Locusta migratoria

The effects of azadirachtin on midgut cells of adult Schistocerca gregaria and Locusta migratoria were investigated by both light and electron microscopy. Pathological effects were seen in both species which could be related to dose and time after treatment. The midgut cells showed a slow necrosis, a rounding up of the cell and swelling of organelles; the nidi were reduced in size and number, the connective tissue beneath the epidermal layer became enlarged with many invading cells/nuclei and the circular and longitudinal muscles become rounded and swollen. The pathological effects were closely linked to a loss of feeding, with injections of 5, 10 and 15 mug/g azadirachtin causing an increasingly rapid onset of the effects associated with an increasingly reduced food intake. At the highest dose, full histopathological effects were seen at 8 hr and death occurred after 3 days. At 1 mug/g, however, the insects showed midgut disruption and reduced feeding by day 3 post-treatment but both feeding and gut pathology had recovered by day 7. At all times, histopathological effects were different from those in starved insects.     

Hypertrehalosaemic and hyperlipaemic responses to adipokinetic hormone in fifth larval instar locusts,Locusta migratoria

In fifth instar larvae of Locusta migratoria the haemolymph lipid concentration is elevated after injection of adipokinetic hormone (AKH). This hyperlipaemic response in larvae remains substantially lower than in adults; over 75% of the mobilized lipid consists of diacylglycerol. In addition, unlike adult locusts, fifth instar larvae also exhibit a consistent, though moderate, hypertrehalosaemic response to AKH. The increases of both lipid and carbohydrate concentrations in larvae are dose-dependent, showing a significant linear regression on log dose in the range 0.2–20 pmol AKH.Glycogen phosphorylase in the fat body of fifth instar larvae as well as young adults is activated on injection of AKH, the percentage active phosphorylase increasing linearly with log dose in the range 0.04–20 pmol AKH. For a given response, a somewhat higher dose of AKH is needed in larvae than in young adults.Fat body glycogen phosphorylase is strongly activated during the period of the larval-adult ecdysis, when active phosphorylase accounts for almost half of the total enzyme, which is approximately ten times more than it is two days before, and two days after the ecdysis.The corpora cardiaca of fifth larval instar locusts already possess the potencies to elevate carbohydrate and lipid concentrations in larval haemolymph, and to activate fat body glycogen phosphorylase.     

Disruption of aggregation behaviour of oriental migratory locusts (Locusta migratoria manilensis) infected with Nosema locustae

Abstract:  The effect of Nosema locustae infection on the aggregation behaviour of the oriental migratory locust, Locusta migratoria manilensis , was studied using a two-choice arena olfactometer and electroantennography (EAG). Infected locusts had low antennal sensitivity and aggregation responses to faecal extracts and to locust body volatiles. Infected fifth instar nymphs had significantly lower aggregation index than the uninfected nymphs, although with fourth instars the effect on aggregation behaviour only occurred in infected females. With regard to antennal receptor sensitivity, infected adult locusts had significantly lower EAG amplitudes in response to extracts from faeces of the adult males. The effect was most pronounced in female locusts. In contrast, there was no significant difference in the EAG responses between the fifth instar male and female nymphs. Further analysis revealed that EAG responses of fifth instar nymphs and adults infected with N. locustae to the faecal extract and volatiles from fifth instar solitary-reared nymphs were not significantly affected. In contrast, infected nymphs and adults had remarkably low EAG amplitudes for the remaining stimuli.     

Protein mediated cholesterol absorption in locusts Schistocerca gregaria (Forskal) and Locusta migratoria (Linn)

Absorption and transport of 3H cholesterol from the midgut to hemolymph and other tissues was studied in the locusts Schistocerca gregaria and Locusta migratoria. S. gregaria are able to absorb dietary cholesterol in the midgut and release into the hemolymph in vivo and into the incubation medium in virto. Certain proteins of midgut origin are involved in the absorption and release of cholesterol. The proteins designated as cholesterol binding proteins (CBP's) were fractionated by gel filtration chromatography using Sepharose CL-6B-200 column. Presence of a protein and its binding with cholesterol is confirmed by TCA precipitation after subsequent incubation of midgut in the incubation medium. Cholesterol binding with the proteins was also confirmed in native polyacrylamide gel electrophoresis. Biosynthesis of this protein takes place in the midgut which is inhibited by a protein synthesis inhibitor, cycloheximide. It also inhibits absorption and release of cholesterol from the midgut. The cholesterol binding activity was associated with a peak containing proteins ranging from molecular weights of 17-32 kDa in SDS-PAGE gels. Treatment of midgut with cycloheximide resulted in reduced cholesterol binding activity. Dilipidation of mucin and transport in presence of bile salts yielded a higher cholesterol binding activity. Although the absorption and release of cholesterol was observed in the hemolymph of both sexes, the ovary exhibited higher cholesterol binding as compared to testis.     

东北地区亚洲飞蝗染色体核型分析

采用常规压片法对吉林省亚洲飞蝗Locusta migratoria migratoria(L.)的染色体核型进行分析.研究结果表明:亚洲飞蝗性别决定机制为X0型,染色体数目为2n♂=23,染色体组式4L+4M+3S+X,全部为端部着丝粒染色体,NF=23.染色体中最长(L1)与最短(S11)染色体之比大于4:1,臂比大...     

Projection areas and branching patterns of the tympanal receptor cells in migratory locusts,Locusta migratoria and Schistocerca gregaria

Summary In Locusta migratoria and Schistocerca gregaria, the projection areas and branching patterns of the tympanal receptor cells in the thoracic ganglia were revealed. Four auditory neuropiles can be distinguished on each side of the ventral cord, always located in the anterior part of the ring tract in each neuromere (two in the meta-, one in the meso-, and one in the prothoracic ganglion). Some of the receptor fibres ascend to the suboesophageal ganglion. There are distinct subdivisions within the auditory, frontal metathoracic and mesothoracic neuropiles. The arrangement of the terminal arborisations of the four types of tympanal receptor cells according to their different frequency-intensity responses is somatotopic and similar in the two ganglia. Here the receptor cells of type-1 form a restricted lateroventral arborisation. Cells of type-4 occupy the caudal part with a dorsorostral extension. Cells of type-2 and -3 arborise in a subdivision between both. Most of the stained low-frequency receptors (type-1, -2, and -3) terminate either in the metathoracic or, predominantly, in the mesothoracic ganglion. In contrast, the high-frequency cells (type-4) ascend to the prothoracic ganglion. The receptor fibres of the different types of receptor cells differ in diameter.Abbreviations aRT anterior part of the ring tract - cf characteristic frequency - MVT median ventral tract - SEG suboesophageal ganglion - SMC supramedian commissure - VMT ventral median tract - VIT ventral intermediate tractSupported by the Deutsche Forschungsgemeinschaft; part of program A7 in Sonderforschungsbereich 305 (Ecophysiology)     

The association of proctolin with a ventral abdominal muscle of Locusta migratoria

The association of proctolin with the external ventral protractor muscle of the VIIth abdominal segment (M234) of Locusta migratoria was investigated using immunohistochemistry and RP-HPLC in conjunction with the sensitive locust oviduct bioassay. Immunohistochemistry of whole-mount tissues revealed two proctolin-like immunoreactive axons in N2B_2b1 (the nerve branch which innervates M234) as well as immunoreactive processes and varicosities on the surface of M234. Immunogold staining of M234 demonstrated that the proctolin-like immunoreactivity was present in electron-dense granules in its motor terminals. A material indistinguishable from proctolin and with proctolin-like bioactivity co-eluted with authentic proctolin on two different RP-HPLC systems. Bath application of proctolin at concentrations greater than 10^-11 M resulted in a dose-dependent increase in the neurally-evoked fast twitch amplitude and duration of M234. Concentrations greater than 10^-9 M resulted in a dose-dependent increase in basal tonus of M234. These results indicate that proctolin, or a peptide very similar to proctolin, is present in the motor innervation of M234 and acts as a cotransmitter and/or neuromodulator at this typical fast skeletal muscle.Abbreviations M234 external ventral protractor muscle of the Vllth abdominal segment - RP-HPLC reverse-phase high pressure liquid chromatography - TFA trifluoroacetic acid     

Inhibition of fungal growth in thermoregulating locusts,Locusta migratoria,infected by the fungus Metarhizium anisopliae var acridum

The locust, Locusta migratoria, has the capacity to develop a behavioural fever which reduces fungal infection by Metarhizium anisopliae var acridum. We investigated hemocyte and blastospore kinetics in infected insects under conditions that did or did not allow thermoregulation. Hemocyte concentrations were severely reduced in inoculated insects that did not thermoregulate but remained similar to those of controls in inoculated insects that were allowed to thermoregulate. Reductions in hemocyte counts were accompanied by an increase in the concentration of blastospores. In non-thermoregulating insects, circulating blastospores were first observed two days post-inoculation and had heavily colonized the hemolymph by day 5; in contrast, no blastospores were recovered from hemolymph of inoculated-thermoregulating insects. We used fluorescein isothiocyanate (FITC)-labelled silica beads to examine in vivo phagocytosis in thermoregulating and non-thermoregulating locusts. In the absence of fungus, a greater proportion of beads were engulfed by hemocytes in thermoregulating than in non-thermoregulating locusts early (4 and 24h) after bead injection, but the proportions were similar thereafter. In infected locusts, phagocytosis in non-thermoregulating insects was progressively impaired; such impairment, however, was not observed in challenged, thermoregulating insects. Our results suggest that thermoregulation helped keep fungal growth in check, apparently through the maintenance of hemocyte population levels and the direct inhibition of blastospore propagation by elevated temperatures.     

Ultrastructure of the colon of Locusta migratoria

The ultrastructure of the colon of Locusta migratoria is described. The colon is lined by a thick cuticle that, for the most part, adheres to the underlying epithelium. The cuboid epithelial cells are characterized by moderate invaginations of the apical and, to a lesser extent, basal plasma membranes; the lateral plasma membranes are relatively flat. The bulk of the mitochondria are located in the apical region of the cell and are not particularly associated with any of the plasma membranes. The basal region of the cells contains much rough endoplasmic reticulum, glycogenlike granules, and a predominance of spherical, electron-dense bodies of various sizes. Where muscle fibers make contact with the epithelium, the cells are much reduced; the cytoplasm is usually less electron-dense, and, typically, the nucleus has a thick layer of granular material associated with the inner nuclear membrane. The apical and basal plasma membranes of the reduced epithelial cells contain numerous hemidesmosomes. The apical hemidesmosomes occur in pairs around an extracellular space that contains electron-opaque material. The latter forms tonofibrillae that extend into the endocuticle. Bundles of microtubules are associated with the hemidesmosomes. The tubules traverse the cell from the apical to the basal region. The possible significance of these findings is discussed.     

Flight orientation of swarming Locusta migratoria

ABSTRACT. High-speed films of four swarms of Locusta migratoria in Australia and one swarm in New Guinea were analysed. Measurements were made of the locust's body orientation and flight track in the horizontal relative to wind direction, and of height and speed of flight. In all swarms mean course angle and mean track angle in relation to wind direction were significantly different from zero, although all indicated an upwind direction. No evidence was found for orientation to compass direction or sun. Considerable fluctuations in flight direction were measured in some individuals as they traversed the field of view. A modification of Kennedy's (1951) theory is adopted to explain the angled orientations to wind. It is suggested that this could be the result of an optical orientation mechanism.     

Muscle activity underlying sexual behaviour in male locusts (Locusta migratoria) after normal and hormonally disturbed development

Abstract. . The activities of three sets of muscles, representing the major components of the abdominal muscle system, were recorded in the pregenital abdominal segments of adult males of Locusta migratoria. The muscular activities were associated with three consecutive actions of the male's mating behaviour: abdominal lowering, S-bending and hooking-up. These three actions depend mainly on the relative coordination of the dorsal versus ventral longitudinal muscles; the activity of the dorsoventral muscles is rather unpredictable, except in the sixth and seventh abdominal segments where they are regularly involved in hooking-up. Studies on male sexual behaviour-linked muscle activity in precocene-induced fifth-instar adultiforms and azadirachtin-induced fifth-instar over-aged nymphs revealed no distinct differences between these creatures and normal mature males. Therefore the muscle activities associated with these adult-specific behavioural acts can be released precociously, i.e. their occurrence is not dependent on a distinct series of instars. Moreover, the results obtained with over-aged nymphs demonstrate that morphogenesis and ethogenesis (i.e. formation of neural circuits controlling adult-specific behaviour) are not closely dependent on each other.     

Miniature potentials in fast and slow muscle fibers in locusts

Excitatory miniature postsynaptic potentials were studied by an intracellular recording method in fast and slow muscle fibers ofLocusta migratorioides. Statistical analysis showed that liberation of mediator in both types of fibers can be predicted by the formula for a negative binomial distribution with a probability of 85%. This correlation is evidence of some degree of interaction between consecutive liberations of quanta of mediator by nerve endings. It is shown that the fraction of miniature potentials depending on the external calcium concentration is greater in fast muscle fibers. An increase in the magnesium ion concentration from 2 to 40 mM led to a decrease in the frequency of miniature potentials, and this decrease was greater in fast fibers; an increase in the magnesium ion concentration from 1 to 10 mM in calcium-free solutions, on the other hand, led to some increase in frequency, and this also was greater in fast muscle fibers. It is concluded that nerve endings in fast and slow muscle fibers differ in their sensitivity to changes in the ionic composition of the medium.I. M. Sechenov Institute of Evolutionary Physiology and Biochemistry, Academy of Sciences of the USSR, Leningrad. Translated from Neirofiziologiya, Vol. 13, No. 2, pp. 210–217, March–April, 1981.     

Purification and characterization of Locusta migratoria chymotrypsin

A chymotrypsin-like enzyme (CTLE) was isolated from the digestive tract of the African migratory locust Locusta migratoria migratorioides by ion-exchange chromatography on diethylaminoethyl (DEAE) cellulose followed by affinity chromatography on phenylbutylamine (PBA) Sepharose. The purity and homogeneity of CTLE have been shown by SDS-PAGE and on cellulose acetate strips. The enzyme has a molecular weight of 24,000, determined by SDS-PAGE and on a Sephadex G-75 calibrated column. It has an isoelectric point of 10.1 and contains 0-1 half cystine residues. Sequence analysis of the first 20 N-terminal amino acids has shown 25% homology with bovine chymotrypsin and 40% homology with Vespa crabo and Vespa orientalis chymotrypsins and with Hypoderma lineatum trypsin. The optimal pH for enzyme activity and stability was in the range of 8.5-9.0. The Km and kcat values, determined on substrates for proteolytic, esterolytic and amidolytic activity, similar to those for bovine chymotrypsin. CTLE was inactivated by PMSF and TPCK indicating the involvement of serine and histidine in its active site. The enzyme was fully inhibited by the proteinaceous, double-headed, chymotrypsin-trypsin inhibitors BBI from soybeans and CI from chickpeas, by chicken ovomucoid (COM) and turkey ovomucoid (TOM), as well as by the Kunitz soybean trypsin inhibitor (STI) which hardly inhibits bovine chymotrypsin. Inhibition studies of CTLE with amino acid and peptide-chloromethylketones point towards the existence of an extended binding site.     

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.