Effects of antibiotics on hydrogen production and gut symbionts in the Formosan subterranean termite Coptotermes formosanus (Isoptera: Rhinotermitidae)

Abstract Symbiotic microorganisms that inhabit the gut of Coptotermes formosanus enable this termite to degrade lignocelluloses and further produce hydrogen as an important intermediate to be recycled in its hindgut or as a byproduct to be emitted to the atmosphere. Both symbiotic protists and prokaryotes in the guts of termites demonstrated some different roles with respect to hydrogen production. In this study, the effects of two antibiotics, ampicillin and tetracycline, on hydrogen emission and the gut symbionts of C. formosanus were investigated. Hydrogen emission from termite guts was significantly enhanced when termites fed on wood diets treated with either ampicillin or tetracycline. The greatest H₂ emission rates, 2 519 ± 74 and 2 080 ± 377 nmol/h/g body weight, were recorded with the treatments of ampicillin and tetracycline, respectively, which showed 6–7 times more H₂ production than that of controls. Antibiotic‐treated diets negatively affected the prokaryotic communities and reduced their abundances, particularly on those ectosymbionts inhabiting the gut walls or in the gut fluid of C. formosanus, such as spirochetes. However, no significant reductions in the counts of gut cellulolytic protists, Pseudotrichonympha grassii and Holomastigotoids hartmanni, were recorded; and with a further observation by confocal laser scanning microscopy, the endosymbionts inhabiting P. grassii generally survived the antibiotic treatments. These results suggest that some prokaryotes may serve as the main hydrogen consumers, while P. grassii, together with its endosymbionts, may function as the main contributors for hydrogen production in the hindgut of C. formosanus.     

Effect of natural products on gut microbes in Formosan subterranean termite,Coptotermes formosanus

The ability of three natural products (neem extract, capsaicin, and gleditschia) to reduce the number of Formosan subterranean termite (FST) hindgut microbes was investigated. FSTs were placed in Petri dishes containing a food source soaked in one of these extracts/compounds. The numbers of three flagellated protozoan species that inhabit the FST hindgut (Pseudotrichonympha grassii, Spirotrichonympha leidyi and Holomastigotoides hartmanni) and spirochaetes were counted over a defined period and analysed for changes in abundance. The results indicated that the neem extract was capable of reducing the population of P. grassii and spirochaetes. Exposure to this extract resulted in significant FST mortality. However, gleditschia extract and capsaicin did not reduce the FST gut microbial population at the concentrations used in this study.     

Dietary‐driven variation effects on the symbiotic flagellate protist communities of the subterranean termite Reticulitermes grassei Clément

The ability of subterranean termites to digest lignocellulose relies not only on their digestive tract physiology, but also on the symbiotic relationships established with flagellate protists and bacteria. The objective of this work was to test the possible effect of different cellulose‐based diets on the community structure (species richness and other diversity metrics) of the flagellate protists of the subterranean termite Reticulitermes grassei. Termites belonging to the same colony were subjected to six different diets (natural diet, maritime pine wood, European beech, thermally modified European beech, cellulose powder and starvation), and their flagellate protist community was evaluated after the trials. All non‐treated sound woods produced similar flagellate protist communities that were more diverse and of high evenness (low dominance). On the contrary, flagellate protist communities from cellulose‐fed termites and starving termites were considered to be significantly different from all non‐treated woods; they were less diverse and some morphotypes became dominant as a consequence of flagellate protist communities having suffered major adaptations to these diets. The flagellate protist communities of untreated beech and thermally modified beech‐fed termites were considered to be significantly different in terms of abundance and morphotype diversity. This may be caused by a decrease in lignocellulose quality available for termites and from an interference of thermally treated wood with the chemical stability of the termite hindgut. Our study suggests that as a consequence of the strong division of labour among these protists to accomplish the intricate process of lignocellulose digestion, termite symbiotic flagellate protist communities are a dynamic assemblage able to adapt to different conditions and diets. This study is important for the community‐level alteration approach, and it is the first study to investigate the effects of thermally modified wood on the flagellate protist communities of subterranean termites.     

Influence of diet on the structure and function of the bacterial hindgut community of crickets

The effect of diets varying in carbohydrate and protein content on the structure and function of the hindgut microbiota of crickets was evaluated by determining bacterial densities, fermentation activity, and guanine plus cytosine (G + C) profiles of the DNA extracted from the microbial hindgut community. DNA isolated from the gut community was fractionated and quantified according to G + C content as a comprehensive, coarse-level measure of the composition and structure of the community. The bacterial densities measured by direct counts were not significantly different among the four diets. The crickets were initially reared in the laboratory on cricket chow, which resulted in a hindgut community dominated by bacteria with a G + C content between 32% and 57%. Crickets shifted to an alfalfa diet showed a similar hindgut community G + C profile, although microbial populations with DNA between 35% and 45% G + C were more abundant in alfalfa- than chow-fed crickets. The apparent complexity of the gut community was reduced in crickets fed beet-pulp and protein-based diets compared to those fed chow and alfalfa, and was dominated by populations with a low percentage G + C content. Hindgut communities in crickets fed pulp and protein diets also showed a decrease in hydrogen and carbon dioxide production, suggesting that these diets affected the biochemical activity of the hindgut community. The protein-based diet resulted in a decrease in the rate of evolution of volatile fatty acids, while the ratio of butyrate production to acetate and propionate production was significantly higher in these crickets. Our results show the emergence of a new microbial community structure concomitant with changes in microbial biochemical activity due to shifts in the cricket's dietary regime.     

Clay preference and particle transport behavior of Formosan subterranean termites （Isoptera： Rhinotermitidae）＂ A laboratory study

Although preference and utilization of clay have been studied in many higher termites, little attention has been paid to lower termites, especially subterranean termites. The Formosan subterranean termite, Coptotermes formosanus Shiraki, can modify its habitat by using clay to fill tree cavities. Here, the biological significance of clay on C. formosanus was investigated. Choice tests showed that significantly more termites aggre- gated in chambers where clay blocks were provided, regardless of colony group, observation period, or nutritional condition （fed or starved）. No-choice tests showed that clay had no observable effect on survivorship, live or dry biomass, water content, and tunneling activity after 33-35 d. However, clay appeared to significantly decrease filter paper consumption （dry weight loss）. Active particle （sand, paper, and clay） transport behavior was observed in both choice and no-choice tests. When present, clay was preferentially spread on the substrate, attached to the smooth surfaces of the containers, and used to line sand tunnels. Mechanisms and potential application of clay attraction are discussed.     

不同饲料饲养的近暗散白蚁工蚁肠道中差异蛋白分析

【目的】本研究旨在通过比较不同木质纤维素含量的饲料对近暗散白蚁Reticulitermesperilucifugus工蚁前中肠和后肠内容物蛋白的组成和表达差异,为揭示白蚁的营养消化吸收机理提供蛋白水平上的依据。【方法】用木质纤维素含量不同的3种饲料(松木、秸秆和滤纸)饲养近暗散白蚁工蚁,然后用双向电泳分析肠道不同部位的内容物蛋白,并对差异蛋白进行MALDI-TOF/MS测序及生物信息学分析。【结果】双向电泳结果发现,同一饲料饲养的近暗散白蚁工蚁前中肠可辨蛋白点数明显多于后肠;不同饲料饲喂的工蚁前中肠和后肠可辨蛋白点数依次是松木饲养的＞滤纸饲养的＞秸秆饲养的。通过对115个蛋白点的测序分析表明,不同饲料饲喂的工蚁前中肠和后肠中的主要差异蛋白为具有催化活性的蛋白质,包括与氨基酸代谢、丙酮酸代谢、碳代谢、氮代谢、TCA循环、糖酵解、糖异生和纤维素降解等相关的酶,以及参与细胞组成和信号传导的蛋白。【结论】木质纤维素含量不同的饲料饲养的近暗散白蚁工蚁肠道中的差异蛋白主要为具有催化活性的蛋白、细胞组成蛋白和信号传导蛋白,表明不同的饲料影响近暗散白蚁的肠道蛋白组成。这些结果为揭示白蚁对木质纤维素的降解机理提供了参考。     

Cloning and Heterologous Expression of Insecticidal-Protein-Encoding Genes from Photorhabdus luminescens TT01 in Enterobacter cloacae for Termite Control

Enterobacter cloacae, one of the indigenous gut bacteria of the Formosan subterranean termite (Coptotermes formosanus), was genetically modified with a transposon Tn5 vector containing genes (tcdA1 and tcdB1) encoding orally insecticidal proteins from the entomopathogenic bacterium Photorhabdus luminescens subsp. laumondii TT01, a symbiont of the entomopathogenic nematode Heterorhabditis bacteriophora, for termite control. In the laboratory, termites were fed filter paper inoculated with the recombinant bacteria. The chromosomal expression of the introduced genes showed that there were insecticidal activities against termite workers and soldiers challenged with the transformed bacteria. After termites were fed recombinant bacteria, the termite mortality was 3.3% at day 5, and it increased from 8.7% at day 9 to 93.3% at day 29. All the dead termites contained the recombinant bacteria in their guts. Transfer of the recombinant bacteria occurred between donor workers (initially fed recombinant bacteria) and recipient workers (not fed). More than 20% of the recipient termites ingested recombinant bacteria within 2 h, and 73.3% of them had ingested recombinant bacteria after 12 h. The method described here provides a useful alternative for sustainable control of the Formosan subterranean termite (C. formosanus) and other social insects, such as the imported red fire ant (Solenopsis invicta).     

Fire ant predation on native and introduced subterranean termites in the laboratory: effect of high soldier number in Coptotermes formosanus

Abstract.

• 1 Native Reticulitermes spp. Holmgren and the introduced Coptotermes formosanus Shiraki (Isoptera: Rhinotermitidae) were exposed to predation in the laboratory by Solenopsis invicta Buren (Hymenoptera: Formicidae), a known predator of Reticulitermes.
• 2 In one experiment, both taxa contained the 2.4% soldiers commonly found in Reticulitermes. In a second experiment, Reticulitermes contained 2.4% and C.formosanus a more normal 18.3% soldiers.
• 3 When soldier proportions were equal, C.formosanus soldiers suffered less of a decrease in survivorship due to predation compared with Reticulitermes soldiers. Little difference was found between taxa in the effect of predation on termite workers or in the effect of termites on predator survivorship.
• 4 When soldier proportions were unequal, both C.formosanus castes suffered less from predation than those of Reticulitermes. Again, little difference was found in the effect of termites on ants.
• 5 C.formosanus showed less movement into new containers when soldier number was abnormally low, compared with both taxa with normal caste proportions.

     

In-situ oxygen profiling and lignin modification in guts of wood-feeding termites

Abstract Reports on the capability of wood-feeding termites (WFTs) in degrading wood particles and on the existence of aerobic environment in the localized guts suggest that their high efficiency of cellulose utilization is not only caused by cellulase, but also by biochemical factors that pretreat lignin. We thus extend the hypothesis that for highly efficient accessibility of cellulose, there should be direct evidence of lignin modification before the hindgut. The lignin degradation/modification is facilitated by the oxygenated environment in intestinal microhabitats. To test our hypothesis, we conducted experiments using a dissolved oxygen microelectrode with a tip diameter < 10 μm to measure oxygen profiles in intestinal microhabitats of both Coptotermes formosanus (Shiraki) and Reticulitermes flavipes (Kollar). Lignin modification during passage through their three gut segments was also analyzed with pyrolysis gas chromatography/mass spectrometry. The data showed relatively high levels of oxygen in the midgut that could have promoted lignin oxidation. Consistent with the oxygen measurements, lignin modifications were also detected. In support of previously proposed hypotheses, these results demonstrate that lignin disruption, which pretreats wood for cellulose utilization, is initiated in the foregut, and continues in the midgut in both termites.     

Use of Genetically Engineered Escherichia coli to Monitor Ingestion, Loss, and Transfer of Bacteria in Termites

Escherichia coli was transformed with a recombinant plasmid (pEGFP) containing the genes for ampicillin resistance and Green Fluorescent Protein (GFP). Escherichia coli expressing GFP (E. coli/GFP+) was then fed to workers of the termite Coptotermes formosanus Shiraki (Isoptera: Rhinotermitidae). The transformed bacteria in the termite guts were detected by growing the gut flora under selective conditions and then checking the cultures for fluorescence. Recombinant plasmids in the termite gut were detected by plasmid extraction with subsequent restriction enzyme digest. The presence of the GFP gene in the gut of termites fed with E. coli/GFP+ was verified by PCR amplification. Transformed E. coli were ingested rapidly when workers fed on filter paper inoculated with E. coli/GFP+. After 1 day, 42% of termite guts harbored E. coli/GFP+. Transfer of E. coli/GFP+ from donor termites (fed with E. coli/GFP+) to recipients (fed with moist filter paper) occurred within 1 day. However, without continuous inoculation, termites lost the transformed bacteria within 1 week.     

Suppression of termite feeding and symbiotic protozoans by the dye, Sudan Red 7 B

Laboratory groups of the Formosan subterranean termite, Coptotermes formosanus Shiraki (Isoptera: Rhinotermitidae), were fed for 14 days on wood shavings soaked in acetone solutions of 0%, 0.5% or 1% concentrations of the dye, Sudan Red 7B or on shavings not soaked in acetone (0% non-acetone, NA). Termites feeding on dyed wood became visibly stained red. Groups of dyed or non-dyed termites were then placed in containers and allowed to feed on non-dyed wood for 21 days. Dyed termites had lower numbers of symbiotic protozoans, lower feeding rates, and lower survivorship than did non-dyed termites. Survivorship was significantly lower in the 1% concentration than in the 0.5% concentration. Covariate analyses suggested that Sudan Red acts both directly and indirectly (via suppression of gut fauna) to reduce vigor in termites. Because there is variable survival response to this dye by different populations of C. formosanus, we recommend preliminary tests of dye toxicity before using it extensively in experiments.

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Résumé Le colorant rouge Soudan 7B (BASF, Wyandotte Corp.) soluble dans l'huile, est un marqueur efficace des termites pour les études dans la nature. Quand les termites consomment des matériaux marqués par ce colorant, ils deviennent nettement colorés en rouge. Bien que certains travaux indiquent que le rouge Soudan n'augmente pas considérablement la mortalité, il n'y a aucune donnée concernant l'effet du colorant sur l'alimentation des termites.Un groupe de Coptotermes formosanus récolté au lac Charles en Louisiane, a été alimenté pendant 14 jours sur copeaux de Pinus sp. colorés avec des solutions 0, 0.5% et 1% (en poids) de rouge Soudan 7B dans l'acétone, ou sur copeaux non colorés et sans acétone (NA). Les groupes de termites colorés ou non sont alors placés dans des récipients pour s'alimenter sur bois non coloré pendant 21 jours. Des différences significatives ont été observées (t. 1): les termites colorés avaient moins de protozoaires symbiontes, consommaient moins de bois et vivaient moins long-temps que les termites sans colorant (t. 2). La survie a été plus faible avec la concentration 1% qu'avec 0.5%. Le nombre de protozoaires était plus faible avec une solution acétonique sans rouge Soudan qu'avec du bois sans acétone, ce qui suggère que l'effet négatif du rouge Soudan sur les protozoaires a pu être augmenté par l'extraction d'une substance favorisant les protozoaires contenue dans les copeaux de pin.La chute de la prise de nourriture a été accompagnée d'une chute parallèle de l'effectif de protozoaires. En réexaminant les résultats de Lai et al. (1983), nous constatons qu'eux aussi avaient observé une réduction de l'effectif de protozoaires de C. formosanus sous l'effet du rouge Soudan. Dans notre étude, nous trouvons que 49,6% de l'effet réducteur du colorant sur la nutrition est expliqué par l'effet simultané sur les protozoaires. Nos résultats sur la survie confirment dans l'ensemble ceux de Su et al. (1983 a) sur C. formosanus de Louisiane. Cependant, C. formosanus de Hawaï (Lai et al., 1983) et de Floride (Su et al., 1988) avaient des taux de survie bien plus élevés. C. formosanus présente nettement des réactions variables au rouge Soudan. Dans notre travail, 64,1% de l'effet du colorant sur la survie a été expliqué par des modifications chez les protozoaires. Ainsi, il semble que le rouge Soudan agisse directement sur l'alimentation et la survie de C. formosanus, et indirectement par la suppression de sa faune intestinale.Bien que nos résultats montrent les effets délétères du rouge Soudan 7B sur C. formosanus, il reste le meilleur colorant pour les termitologistes. par suite de la variabilité de son effet sur la survie, nous conseillons des tests de toxicité avant son utilisation intensive dans des expériences.

     

高效降解木质纤维素的白蚁肠道微生物组

木食性白蚁是自然界木质纤维素的高效降解者,在长期进化过程中白蚁与其肠道微生物组协同作用发展出不同的纤维素降解机制。木食性白蚁具有分别来源于白蚁和共生微生物的两套纤维素酶系统。在低等白蚁中,木质颗粒经过白蚁前、中肠分泌的内源性酶初步消化后,在后肠共生鞭毛虫中被降解为乙酸、二氧化碳和氢。高等木食性白蚁在进化中丢失了鞭毛虫,木质颗粒经白蚁自身分泌的酶初步消化后,在后肠大量共生细菌的帮助下被有效降解。培菌类白蚁利用其菌圃中的蚁巢伞菌和肠道微生物协同作用降解木质纤维素。共生微生物在白蚁的氮素固定与循环、中间产物代谢及纤维素降解等过程中发挥了重要作用。学习和模拟白蚁高效降解木质纤维素的体系,对生物质能源的产业化发展具有积极的意义。     

The nature of soil pernicious to Coptotermes formosanus

The Formosan subterranean termites, Coptotermes formosanus, were incubated in soils collected from various locations on the island of Hawaii. More than 70% of the termites died within 2 weeks in seven of nine soil samples collected from Kamuela. In control soil termites remained alive after 4 weeks. Entomophthora coronata, Metarrhizium anisopliae, Aspergillus flavus, and an unidentified bacterium were isolated from 60 to 100% of dead termites incubated in the pernicious soils. E. coronata and M. anisopliae were pathogenic to C. formosanus. The innocuous soil from Hilo became pernicious to C. formosanus after it was inoculated with E. coronata or M. anisopliae.     

松墨天牛成虫室内外种群肠道细菌的多样性及功能分析

[目的]为明确松墨天牛Monochamus alternatus成虫中、后肠细菌群落结构,探索肠道细菌的潜在功能.[方法]分别提取室外和室内饲养的松墨天牛成虫各15头(室内和室外各15个中肠、15个后肠)的肠道DNA,利用二代测序技术对松墨天牛成虫肠道细菌的16S rDNA V3-V4区序列进行测序,统计操作分类单元(...     

Influence of Feed Components on Symbiotic Bacterial Community Structure in the Gut of the Wood-Feeding Higher Termite Nasutitermes takasagoensis

The influence of carbon sources on bacterial community structure in the gut of the wood-feeding higher termite Nasutitermes takasagoensis was investigated. 16S rRNA gene sequencing and terminal-restriction fragment length polymorphism (T-RFLP) analyses revealed that the bacterial community structure changed markedly depending on feed components at the phylum level. Spirochaetes was predominant in the clone libraries from wood- and wood powder-fed termites, whereas Bacteroidetes was the largest group in the libraries from xylan-, cellobiose-, and glucose-fed termites, and Firmicutes was predominant in the library from xylose-fed termites. In addition, clones belonging to the phylum Termite Group I (TG1) were found in the library from xylose-fed termites. Our results indicate that the symbiotic relationship between termite and gut microorganisms is not very strong or stable over a short time, and that termite gut microbial community structures vary depending on components of the feeds.     

Testing the role of cuticular hydrocarbons on intercolonial agonism in two subterranean termite species (Coptotermes) and their hybrids

Recognition of nestmates is an important function in many social insects, as it maintains colony integrity by preventing outsiders from entering the colony. Agonism usually results from the interaction of con-specific non-nestmate individuals in termite colonies. Previous studies hypothesized that the cuticular hydrocarbon (CHC) profile of individuals had a role in nestmate recognition. However, contradictory results from previous studies in some subterranean termites raise questions on the validity of the cuticular hydrocarbon hypothesis. In the current study, Coptotermes gestroi (Wasmann), Coptotermes formosanus Shiraki and their hybrids were reared in identical conditions from colony foundation. This approach eliminates sources of variability in their cuticular hydrocarbon profiles aside from a genetic component. The parental species displayed dissimilar profiles of predominant alkanes and methyl alkanes, but both hybrid types displayed an overlapping, intermediate profile of these CHC. The mixture of the most abundant CHCs alone did not determine kin recognition; while the two hybrid types’ CHC profiles converged, the hybrids still showed strong agonism. One of the hybrid mating types easily merged with C. formosanus, despite only partial genetic similarity and dissimilar cuticular profiles for the common alkanes and methyl alkanes. This study suggests that in Coptotermes termites, the variable abundance of the major alkanes and methyl alkanes commonly found in most Coptotermes species does not explain agonistic patterns, and that other factors such as possibly more complex but less abundant CHC are likely to be involved in colonial recognition.

     

Effect of seed extracts of <Emphasis Type="Italic">Withania somnifera,Croton tiglium</Emphasis> and <Emphasis Type="Italic">Hygrophila auriculata</Emphasis> on behavior and physiology of <Emphasis Type="Italic">Odontotermes obesus</Emphasis> (Isoptera,Termitidae)

In addition to antibiotic properties, medicinal plants are important sources of chemicals with potential application as pesticides. The present study deals with antitermitic potential of seed extracts of Withania somnifera (Indian ginseng), Croton tiglium (jamalgoota) and Hygrophila auriculata (talimkhana). The seed extracts caused changes in tunneling behaviour, number of bacterial colonies in hindgut and activities of enzymes in midgut of Odontotermes obesus. C. tiglium showed the lowest LT₅₀ (12.85 and 2.65 h) among the three seed extracts at concentrations of 50% (half dilution of the extract) and 100% (extract without dilution), respectively. There was no tunneling in soil treated with 100% concentration of seed extracts of W. somnifera and C. tiglium. Numbers of bacterial colonies in the gut of termites from soils treated with 50% and 100% concentrations of the three plants did not differ significantly, but they differed from those in termites from untreated soil. At 50% concentrations of seed extracts of the tested plants, the difference in hindgut enzyme activities was not obvious, however, at 100% concentrations the enzyme activities in the termites from soils treated with seed extracts significantly differed from controls and differences were also recorded between the plants.     

Characterization of a laccase from a wood‐feeding termite,Coptotermes formosanus

Coptotermes formosanus Shiraki is a wood‐feeding termite which secretes a series of lignolytic and cellulolytic enzymes for woody biomass degradation. However, the lignin modification mechanism in the termite is largely elusive, and the characteristics of most lignolytic enzymes in termites remain unknown. In this study, a laccase gene lac1 from C. formosanus was heterogeneously expressed in insect Sf9 cells. The purified Lac1 showed strong activities toward hydroquinone (305 mU/mg) and 2,6‐dimethoxyphenol (2.9 mU/mg) with low K_m values, but not veratryl alcohol or 2,2’‐azino‐bis (3‐ethylbenzothiazoline‐6‐sulfonic acid). Lac1 could function well from pH 4.5 to 7.5, and its activity was significantly inhibited by H₂O₂ at above 4.85 mmol/L (P < 0.01). In addition, the lac1 gene was found to be mainly expressed in the salivary glands and foregut of C. formosanus, and seldom in the midgut or hindgut. These findings suggested that Lac1 is a phenol‐oxidizing laccase like RflacA and RflacB from termite Reticulitermes flavipes, except that Lac1 was found to be more efficient in phenol oxidation, and it did not require H₂O₂ for its function. It is suspected that this kind of termite laccase might only be able to directly oxidize low redox‐potential substrates, and the high redox‐potential groups in lignin might be oxidized by other enzymes in the termite or by using the Fenton reaction.     

Antitermitic effect of the Lantana camara plant on subterranean termites (Isoptera: Rhinotermitidae)

Abstract The insecticidal effects of Lantana camara L. (flowers, leaves, stems and roots) and the soil where lantana had been growing, on foraging activity and survival of the subterranean termites Coptotermes formosanus and Reticulitermes flavipes were examined in a 3-week experiment. The soil in which lantana had been growing had no effect on termite tunneling and survival. Incorporation of chipped fresh lantana leaves and stems into soil had no effect on mortality but caused significant reduction in tunneling. The 5-cm wide barrier of soil with lantana tissue incorporated effectively repelled groups of both species from penetrating the barrier and thus prevented infestation of a piece of wood on the other side of the barrier. C. formosanus was more sensitive in avoiding the barrier than R. flavipes. Leaves, stems and flowers were more repellent than roots. These results provide preliminary evidence that fresh-cut lantana leaves, stems and flowers may have use as additives to garden mulches against termites.     

Haemolymph amino acid and sugar levels in locusts fed nutritionally unbalanced diets

Aspects of pre- and post-ingestive compensation were investigated in locusts (Locusta migratoria) fed nutritionally unbalanced artificial diets containing 7% protein and 21% digestible carbohydrate (7:21) or 21% protein and 7% digestible carbohydrate (21:7). Feeding behaviour and haemolymph levels of amino acids and sugars were measured in locusts fed ad libitum on these diets. Locusts fed the high-protein diet had chronically elevated haemolymph levels of 15 out of 19 amino acids measured compared to locusts fed the low protein diet. However, haemolymph levels of lysine, alanine, aspartic acid and glutamic acid did not differ between diets, suggesting some specific regulatory mechanism for these amino acids. Haemolymph glucose and trehalose reflected levels of carbohydrate in the diets, being high in insects fed diet 7:21 relative to those given diet 21:7. These data are discussed in relation to the physiological and behavioural bases of nutritional homeostasis.Abbreviations AA amino acid(s) - PRO protein - CHO carbohydrate - PBS phosphate-buffered saline - MW molecular weight