Mechanisms regulating salt intake in fifth-instar nymphs of Locusta migratoria

Abstract. Investigations were undertaken into the mechanisms controlling regulation of salt intake in fifth-instar nymphs of Locusta migratoria L. Initially, the pattern of feeding was recorded for 24 h in locusts fed a chemically-defined food either with or without salt. Differences were apparent from the first meal, with smaller meals being eaten more frequently on the salt-free food over the next 8h. As a result, total food intake over the first 8h was similar on the two foods. By 24 h, however, intake of the salt-free food was considerably reduced and the rate of prefeeding rejections was high. Next, following a period of pretreatment (24 or 48 h) on one of these two foods, responses were recorded to glass-fibre discs impregnated with salts, artificial foods differing in salt content, and wheat germ. Haemolymph amino acid titres were also recorded in locusts feeding ad libitum on salt-free or salt-containing food to test the 'metabolic bottleneck' hypothesis for explaining rejection of a salt-free food after a period of feeding on it. Finally, the role of learning was investigated in experiments in which distinctive plant odours and flavours were paired with foods lacking or containing salt. Results across all the experiments indicate that regulation of mineral intake in locust nymphs involves a number of mechanisms, including modulation of locomotory behaviour, innate taste responses and learning. Additionally, there was evidence of a sex difference in salt appetite.     

Patterns of respiration in Locusta migratoria nymphs when feeding

Flow‐through respirometry was used to investigate patterns of respiration of fifth‐instar Locusta migratoria L. nymphs fed a chemically defined, synthetic food. Each animal was recorded for up to 2.7 h, during which they had access to food and water ad libitum, and at least one meal was taken. The start of feeding was coincident with a sudden and rapid rise in respiration. Both carbon dioxide (CO₂) production and oxygen (O₂) consumption rose, the traces for the two gasses showing a high degree of alignment. The end of a meal correlated with a sudden and rapid decrease in respiratory rate towards resting levels. When feeding was interrupted by an intra‐meal pause, respiratory rate tended to drop marginally and then stabilize, before rising rapidly upon the resumption of feeding within the meal. Maximal rates of respiration during feeding represented a 3–4‐fold increase over those at rest. Walking and climbing within the chamber were not associated with any noticeable change in respiratory rate above baseline. When locusts were quiescent between feeding episodes, respiration was steady and continuous, rather than discontinuous. Possible causes for large changes in respiration during feeding are discussed.     

Vitellogenesis and oocyte development in azadirachtin-induced fifth-instar overage nymphs of Locusta migratoria (L.)

Injection of azadirachtin into females of Locusta migratoria at the beginning of the last nymphal instar prevented molting to the adult stage, and many of these locusts survived for long periods as overage fifth-instar nymphs. Overage female nymphs synthesized vitellogenin; maximum vitellogenin content in their hemolymph was 6–7 times higher than that found in normal adult females. The overage female nymphs developed vitellogenic oocytes, but development was retarded to some extent: although vitellogenin did accumulate in the proximal oocytes, their maximum average length was only about 2.8 mm (compared to 6.2 mm in normal adult females) and extensive oocyte resorption was observed. Thus, attainment of adult competence of the organs and processes involved in female reproduction is independent to a considerable extent from the process of overt adult morphogenesis.     

Patterns in feeding: a behavioural analysis using Locusta migratoria nymphs

ABSTRACT. Feeding patterns of Locusta migratoria L. nymphs, kept under LD 12:12 at 30°C with ample food, were analysed over the first 6 days of the fifth instar. A number of differences were found between the light and dark phases. (1) More was eaten during the light than the dark, with the differences becoming progressively larger over the 6 days. (2) During light phases most insects showed an increasing tendency to feed with time since the last meal, while in the dark the probability of starting to feed remained constant. (3) There was little variation in feeding patterns within the light phase, but marked changes occurred within the dark phase, feeding declining to a low level in the last 4h. The amount eaten during a meal was regulated similarly in the light and dark, with time rather than amount eaten being of paramount importance in terminating a meal. The time when feeding started was somewhat influenced by the size of the preceding meal, but once feeding began meal size was largely independent of the preceding meal. The importance of food quality in determining the pattern of feeding is discussed.     

The role of volumetric feedback from the hindgut in the regulation of meal size in fifth-instar Locusta migratoria nymphs

ABSTRACT. Behavioural studies show that fullness of the hindgut influences the size of meals taken by fifth-instar Locusta migratoria L. nymphs, with the relevant information coming from the ileum and passing via the terminal abdominal ganglion. Morphological and electrophysiological studies suggest that stretch receptors on the posterior ileum, associated with branches of the rectal nerves, register extension of the ileal fold and probably also an increase in ileal volume. A system in which the volumetric feedbacks from both the crop and hindgut interact in the regulation of meal size is postulated.     

The physiological control of drinking behaviour in nymphs of Locusta migratoria

ABSTRACT. The changes in behaviour of nymphs of Locusta migratoria in relation to free water, during the course of two different deprivation regimes are described. With no access to food or water for 24 h at 30°C, the insects responded positively to free water when it was provided. If dry food was provided during water deprivation, positive responses occurred in 8 h. The physiological changes associated with the behavioural change indicate that positive responses were correlated with a reduction in abdominal volume; experimentally induced changes confirmed this. Increased osmotic pressure did not influence the onset of drinking, but the amount of water ingested was directly correlated with the size of osmotic pressure increases.     

Precocene-induced necrosis and haemocyte-mediated breakdown of corpora allata in nymphs of the locust Locusta migratoria

Light and electron microscopic studies, including the use of the vital dyes trypan blue and acridine orange, indicate that the topical application of precocene II rapidly triggers degenerative processes in the corpora allata (CA) leading within a few days to the virtual disappearance of the parenchymal cells of these glands. The following sequence of events was observed: 1) Within 2 h, many of the cells in fixed nymphal specimens showed increased electron density. During the next few hours, they decreased considerably in volume (shrinkage necrosis). Intercellular spaces increased simultaneously. Although a variable number of cells remained electron lucent, they showed nuclear and cytoplasmic degeneration later on (coagulative necrosis). 2) Haemocytes arrived at the CA sheath and invaded the CA in large numbers after 12 h. 3) CA cells became increasingly necrotic, and cell fragments were budded off and were phagocytosed most noticeably after 1 to 3 days. Thereafter no CA parenchyma remained. 4) Haemocytes dispersed.     

Influence of age on chiasma number in male Locusta migratoria

The influence of age on chiasma formation in Locusta migratoria has been studied both in wild-type and irradiated males. Samples were obtained on the one hand from different individuals and on the other hand from the same individuals at different ages through repeated biopsies. It was observed that mean chiasmata per cell decreased in ageing animals. Chi-squared tests and correlation coefficients showed that the decrease of chiasmata with age is progressive but not continuous. Intermediate values coincide with the first mating. It seems that older individuals tend to transmit their genetic combinations unaltered, increasing the probability of transmitting gene combinations of adaptive value.     

The regulation of feeding in Locusta migratoria: Internal inhibitory mechanisms

During the course of a meal by insects with an empty gut, food is held in the foregut and the midgut remains empty. The last part of the foregut to fill is the extreme anterior end of the crop, and stretch receptors in this region control the amount eaten. Cutting the posterior pharyngeal nerves isolates these receptors from the frontal garglion and results in hyperphagia pharyngeal nerves isolates these receptors from the frontal garglion and results in hyperphagia during one meal. On unfavourable food, when smaller amounts are eaten, distension of the foregut is not involved in regulating meal size.Feedback from receptors in the body wall is not important in regulating meal size; most of the increase in gut volume resulting from feeding is taken up by the collapse of the air sacs so that there is little or no change in the body volume.

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Zusammenfassung Alle Hauptnerven des Mund- und Rachennervensystems wurden kontrolliert reseziert. Erst wenn die rückwärtigen Rachennerven zerschnitten werden, nehmen die Insekten wesentlich mehr Nahrung zu sich. Solche Insekten versuchen längere Zeit zu fressen.Wenn sich während des Fressens der Vorderdarm füllt, wird keine Nahrung an den Mitteldarm weitergegeben und sein Vorderende ist der letzte Teil, der sich vollständig ausdehnt. Nach Durchtrennung der rückwärtigen Rachennerven sind alle Teile des Vorderdarms offen-sichtlich mehr gedehnt. Eine solche erhöhte Nahrungsaufnahme tritt aber nicht ein, wenn die Nahrung relativ ungünstig ist. Das Abbinden des Kropfes verursacht beim nachträglichen Fressen keine übermäßige Ausdehnung des Vorderteiles.Die Nahrungsaufnahme hat keinen Unterschied im Körpervolumen zur Folge und das Durchtrennen des ventralen Nervenstranges bleibt ohne Einfluß auf die nachträglich aufgenommenen Nahrungsmengen. Das vergrößerte Darmvolumen wird durch Kollaps des Luftsackes kompensiert.

     

Surface chemistry of Sorghum bicolor and its importance in feeding by Locusta migratoria

ABSTRACT. Seedling Sorghum bicolor cv.65D was rejected at palpation by nymphs of Locusta migratoria L. unless the surface wax was removed. The wax by itself was unpalatable, and when fractionated chromatographically into constituent chemicals its deterrent effects were attributable to the p -hydroxybenzal-dehyde, n -alkane, and ester fractions. Analysis of these last two fractions showed that they were unusual in that the carbon chain lengths of the molecules were shorter than expected from previous literature, and it was these smaller molecules (tested as pure chemicals) that were repellent to L.migratoria. The short-chain esters are more volatile than the ineffective longer-chain ones, and it is proposed that the insect may detect these chemicals by short-range olfaction and hence reject the plant before biting, thus imparting a more effective defence to the plant.     

饥饿对东亚飞蝗生长和取食的影响

研究了不同龄期东亚飞蝗Locusta migratoria manilensis(Meyen)的耐饥饿能力和3龄后的东亚飞蝗在不同饥饿程度下的取食量和取食速度。结果表明,东亚飞蝗的耐饥饿能力基本随龄期的增加而增强,平均耐饥饿时间为46～116h;同一龄期的东亚飞蝗,饥饿12h后的取食量和取食速度均大于正常情况,饥饿24h后的取食量和取食速度与正常情况下差异不显著,饥饿36、48h后的取食量和取食速度均明显小于正常情况;饥饿程度越大,取食量就越小,取食速度越慢。     

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...     

X-linkage of a vitellogenin gene in Locusta migratoria

Hybridization of a cloned DNA probe to blots of restriction digests of Locusta migratoria genomic DNA showed that a vitellogenin gene is present at one copy per haploid genome in females, and at only one-half that number in males. The genomic region encompassing the 3′-coding end of the gene is polymorphic, as revealed by blots of DNA from individual locusts. DNA from some female locusts yielded two variants in this region, whereas a series of male locusts showed one variant or the other, but never both. The results demonstrate that the vitellogenin gene, which is normally expressed only in females, is X-linked in L. migratoria.     

Changes in haemolymph osmotic pressure in Locusta migratoria larvae in relation to feeding

An account is given of the effect of feeding on haemolymph osmotic pressure in larvae of Locusta migratoria. Changes in concentration of solutes and haemolymph volume are investigated and discussed.     

不同食料植物对东亚飞蝗肠道细菌状况的影响

目的比较在相同的环境条件下不同食料植物对东亚飞蝗肠道细菌状况的影响。方法以墨西哥玉米、野生马唐为食料植物饲喂东亚飞蝗,在其成虫肠道内和粪沙中分离纯化细菌,获得22株菌株,分别对其培养性状、菌体形态、染色反应和生理生化性状进行系统研究。结果上述22个菌株分别属于稀有杆菌属（Rarobact-er）、短状杆菌属（Brachybacterium）、棒杆菌属（Corynebacterium）、棍状菌属（Clavibacter）、葡萄球菌属（Staphylococ-cus）、丙酸杆菌属（Propionibacterium）、埃希菌属（Eschrichia）、气微杆菌属（Aercmicrobium）、沙雷菌属（Serratia）、克雷伯菌属（Klebsiella）、沙门菌属（Salmonella）、志贺菌属（Shigella）、口腔球菌属（Stomatococcus）、短杆菌属（Brevibacteri-um）、地杆菌属（Terrbacter）、微小杆菌属（Exiguobacterium）、皮杆菌属（Dermabacter）、短小杆菌属（Curtobacterium）、纤维单胞菌属（Cellulomonas）、微杆菌属（Microbacterium）、乳杆菌属（Lactobacillus）和凝结芽胞杆菌属（Bacilluscoag-ulans）。结论不同食料植物对东亚飞蝗肠道细菌种类和数量有很大的影响。     

The effect of combinations of deterrents on the feeding behaviour of Locusta migratoria

Combinations of feeding deterrents are additive in their effects on the feeding behaviour of Locusta migratoria. The effect has been shown within and across different chemical classes. A mixture of fourteen different phenolic compounds from Sorghum bicolor tested in naturally occurring concentrations is deterrent although the individual levels of deterrence are not measurable. The significance of the findings in relation to plant resistance is discussed.

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Résumé Dix substances provoquant l'inappétence, appartenant à sept classes chimiques différentes, ont été examinées isolément et en diverses combinaisons quant à leur effet sur Locusta migratoria. L'inappétence obtenue avec différentes combinaisons a indiqué que les effects des substances chimiques individuelles s'additionnaient.Un groupe de quatorze composés phénoliques dérivés des feuilles de sorgho a été éprouvé à des concentrations existant dans la nature. Bien que ces composés n'aient pas causé individuellement une inappétence mesurable, le mélange de tous les composés, aux mêmes concentrations, a réduit considérablement l'ingestion d'aliments.

     

五龄飞蝗不同发育时间实时定量PCR内参基因的筛选

【目的】筛选5龄飞蝗不同发育时间的最适内参基因,为相关研究提供基础数据。【方法】本文选取β-肌动蛋白(β-actin)、延长因子(EF-1α)、3-磷酸甘油醛脱氢酶(GAPDH)、核糖体蛋白49(RP49)、α-微管蛋白(α-Tubulin)和18S核糖体RNA(18S rRNA)基因作为候选内参基因,运用实时定量PCR(qPCR)方法研究各基因在5龄飞蝗不同发育时间的相对表达量,用geNorm与Normfmder软件分析这6个基因表达稳定性。【结果】geNorm分析结果显示6个内参基因表达稳定度M值顺序为:β-actin(0.3720)>RP49(0.3750)>α-Tubulin(0.4030)>18S rRNA(0.4270)>EF-1α(0.4970)>GAPDH(0.6040)。M值越小表示基因表达稳定度越高,同时geNorm软件以标准化因子配对差异值(Pairwise variations)0.15默认为取舍值,由于V2/3=0.098<0.15,所以最适内参基因数目为2个。运用NormFinder软件也得出相似的结果。【结论】β-actin与RP49为5龄飞蝗不同发育时间的最适内参基因。     

Isolation and characterization of a larval hemolymph protein in Locusta migratoria

A high-molecular-weight protein, M_r 500,000, has been isolated and characterized from the hemolymph of the migratory locust, Locusta migratoria. It is composed of six seemingly identical subunits of apparent M_r 78,000. It contains low concentrations of carbohydrate and lipid, but high percentages of aspartate and glutamate as well as high proportions of hydrophobic amino acid residues. An antiserum, developed against this purified hemolymph protein, does not react in the double-diffusion test or after immunoblotting with purified lipophorin or cyanoprotein, two other major proteins in locust hemolymph. The concentration of this larval specific protein in the hemolymph of Locusta was examined during the last larval instar and in adult males by quantitative rocket immunoelectrophoresis. Its concentration increases in the second half of the fifth instar, concommitant with an increase in total protein. The protein is detectable by immunological techniques in adults, although its concentration is very low at this stage.     

Identification of a diuretic hormone of Locusta migratoria.

We have isolated a peptide from brains and corpora cardiaca of Locusta migratoria which is immunologically related to the diuretic hormone of Manduca sexta. We determined its structure as a 46 amino acid linear peptide with 43-50% identity to the M. sexta hormone. Moreover, we showed that the new peptide functions as a diuretic hormone in L. migratoria, stimulating urine production by Malpighian tubules and elevating levels of cAMP in tubules.