Soil-plant-gall relationships: from gall development to ecological patterns.

The adaptive nature of the galler habit has been tentatively explained by the nutrition, microenvironment, and enemy hypotheses. Soil attributes have direct relationships with these three hypotheses at the cellular and macroecological scales, but their influence has been restricted previously to effects on the nutritional status of the host plant on gall richness and abundance. Herein, we discuss the ionome patterns within gall tissues and their significance for gall development, physiology, structure, and for the nutrition of the gallers. Previous ecological and chemical quantification focused extensively on nitrogen and carbon contents, evoking the carbon-nutrient defence hypothesis as an explanation for establishing the plant-gall interaction. Different elements are involved in cell wall composition dynamics, antioxidant activity, and regulation of plant-gall water dynamics. An overview of the different soil-plant-gall relationships highlights the complexity of the nutritional requirements of gallers, which are strongly influenced by environmental soil traits. Soil and plant chemical profiles interact to determine the outcome of plant-herbivore interactions and need to be addressed by considering not only the soil features and galler nutrition but also the host plant's physiological traits. The quantitative and qualitative results for iron metabolism in gall tissues, as well as the roles of iron as an essential element in the physiology and reproduction of gallers suggest that it may represent a key nutritional resource, aligning with the nutrition hypothesis, and providing an integrative explanation for higher gall diversity in iron-rich soils.

Larval Rearing and Nutrition of the Polyphagous Tephritid Pest Anastrepha ludens on Artificial Diets with Calcium Alginate, Agar, or Carrageenan as Gelling Agents at Various Concentrations and across Extreme Larval Density Conditions.

Research on larval rearing and nutrition of tephritid flies on artificial diets is key for the sterile insect technique. Here, we examined the effects of the type of gel (calcium alginate, agar, or carrageenan), at varying percentages in artificial diets for the polyphagous pest Anastrepha ludens, on the physicochemical and nutritional traits of the diets, and the effects of the type of gel, the gel content and the larval density (larvae/g of diet) used in production, quality parameters for mass-reared tephritids, diet removal (an indirect estimation of diet consumption), and nutritional traits of flies. Regardless of the gel content, calcium alginate diets were firmer and more resistant to penetration than the agar and carrageenan diets. The larval recovery, pupation, pupal weight, and flight ability of A. ludens were lower in calcium alginate diets than in agar and carrageenan diets. Diet removal was higher in calcium alginate diets; however, low levels of ammonium and high levels of uric acid in excretions from larvae on these diets suggest an alteration in protein metabolism. The firmness and penetration resistance characteristics of calcium alginate diets may have limited movement and feeding of larvae, but this could be overcome by the collective feeding of large groups of larvae. Our findings provide insights into the mechanism governing gel-diet rearing systems for A. ludens.

A soybean trypsin inhibitor reduces the resistance to transgenic maize in a population of Spodoptera frugiperda (Lepidoptera: Noctuidae).

Lepidopteran pests have been successfully managed by the adoption of insect resistant transgenic plants expressing Cry and/or Vip insecticidal proteins derived from Bacillus thuringiensis (Bt plants). Among such pests, Spodoptera frugiperda (Smith, 1797) (Lepidoptera: Noctuidae) is highlighted for its destructive potential in maize crops and for cases of field-evolved resistance to Bt plants. Cry insecticidal proteins expressed in Bt plants are known for their interaction with insect midgut receptors and subsequent midgut cell disruption that leads to target pest death. In the midgut of lepidopteran larval pests such as S. frugiperda, serine proteases are important in dietary protein digestion and activation or degradation of insecticidal proteins. This work was conducted to evaluate if the use of a soybean trypsin inhibitor (SBTI) could disrupt the development of a Bt-susceptible and a Bt-resistant population of S. frugiperda ingesting Bt (expressing Cry1F, Cry1A.105, and Cry2Ab2 Cry proteins) and non-Bt maize plants. The SBTI was produced and purified using recombinant expression in E. coli followed by purification in Ni-Sepharose. Bioassays using non-Bt maize leaves indicated that the development of susceptible and resistant populations of S. frugiperda was not influenced by the ingestion of SBTI. However, when the resistant population consumed Bt maize plants amended with SBTI, high mortality along with a reduction in larval weight and reduced activity of digestive trypsins were observed. Although the mode of action was not elucidated, it is possible that the consumption of SBTI increased susceptibility to Bt maize in the resistant population of S. frugiperda.

The ecology of nutrient sensation and perception in insects.

Insects are equipped with neurological, physiological, and behavioral tools to locate potential food sources and assess their nutritional quality based on volatile and chemotactile cues. We summarize current knowledge on insect taste perception and the different modalities of reception and perception. We suggest that the neurophysiological mechanisms of reception and perception are closely linked to the species-specific ecology of different insects. Understanding these links consequently requires a multidisciplinary approach. We also highlight existing knowledge gaps, especially in terms of the exact ligands of receptors, and provide evidence for a perceptional hierarchy suggesting that insects have adapted their reception and perception to preferentially perceive nutrient stimuli that are important for their fitness.

Inter-Individual Nectar Chemistry Changes of Field Scabious, Knautia arvensis.

Nectar is crucial to maintain plant-pollinator mutualism. Nectar quality (nutritional composition) can vary strongly between individuals of the same plant species. The factors driving such inter-individual variation have however not been investigated closer. We investigated nectar quality of field scabious, Knautia arvensis in different grassland plant communities varying in species composition and richness to assess whether nectar quality can be affected by the surrounding plant community. We analyzed (with high performance liquid chromatography) the content of carbohydrates, overall amino acids, and essential amino acids. Amino acid and carbohydrate concentrations and proportions varied among plant individuals and with the surrounding plant community but were not related to the surrounding plant species richness. Total and individual carbohydrate concentrations were lowest, while proportions of the essential amino acids, valine, isoleucine, leucine (all phagostimulatory), and lysine were highest in plant species communities of the highest diversity. Our results show that K. arvensis nectar chemistry varies with the composition of the surrounding plant community, which may alter the taste and nutritional value and thus affect the plant's visitor spectrum and visitation rate. However, the strong inter-individual variation in nectar quality requires additional studies (e.g., in semi-field studies) to disentangle different biotic and abiotic factors contributing to inter-individual nectar chemistry in a plant-community context.

Microbiome-assisted carrion preservation aids larval development in a burying beetle.

The ability to feed on a wide range of diets has enabled insects to diversify and colonize specialized niches. Carrion, for example, is highly susceptible to microbial decomposers, but is kept palatable several days after an animal's death by carrion-feeding insects. Here we show that the burying beetle Nicrophorus vespilloides preserves carrion by preventing the microbial succession associated with carrion decomposition, thus ensuring a high-quality resource for their developing larvae. Beetle-tended carcasses showed no signs of degradation and hosted a microbial community containing the beetles' gut microbiota, including the yeast Yarrowia In contrast, untended carcasses showed visual and olfactory signs of putrefaction, and their microbial community consisted of endogenous and soil-originating microbial decomposers. This regulation of the carcass' bacterial and fungal community and transcriptomic profile was associated with lower concentrations of putrescine and cadaverine (toxic polyamines associated with carcass putrefaction) and altered levels of proteases, lipases, and free amino acids. Beetle-tended carcasses develop a biofilm-like matrix housing the yeast, which, when experimentally removed, leads to reduced larval growth. Thus, tended carcasses hosted a mutualistic microbial community that promotes optimal larval development, likely through symbiont-mediated extraintestinal digestion and detoxification of carrion nutrients. The adaptive preservation of carrion coordinated by the beetles and their symbionts demonstrates a specialized resource-management strategy through which insects modify their habitats to enhance fitness.

Modulation of nonessential amino acid biosynthetic pathways in virulent Hessian fly larvae (Mayetiola destructor), feeding on susceptible host wheat (Triticum aestivum).

Compatible interactions between wheat (Triticum aestivum), and its dipteran pest Hessian fly (Hf, Mayetiola destructor) result in successful establishment of larval feeding sites rendering the host plant susceptible. Virulent larvae employ an effector-based feeding strategy to reprogram the host physiology resulting in formation of a protein- and sugar-rich nutritive tissue beneficial to developing larvae. Previous studies documented increased levels of nonessential amino acids (NAA; that need not be received through insect diet) in the susceptible wheat in response to larval feeding, suggesting importance of plant-derived NAA in larval nutrition. Here, we investigated the modulation of genes from NAA biosynthetic pathways (NAABP) in virulent Hf larvae. Transcript profiling for 16 NAABP genes, annotated from the recently assembled Hf genome, was carried out in the feeding first-, and second-instars and compared with that of the first-instar neonate (newly hatched, migrating, assumed to be non-feeding) larvae. While Tyr, Gln, Glu, and Pro NAABP genes transcript abundance declined in the feeding instars as compared to the neonates, those for Ala, and Ser increased in the feeding larval instars, despite higher levels of these NAA in the susceptible host plant. Asp, Asn, Gly and Cys NAABP genes exhibited variable expression profiles in the feeding first- and second-instars. Our results indicate that while Hf larvae utilize the plant-derived NAA, de novo synthesis of several NAA may be necessary to: (i) provide larvae with the requisite amount for sustaining growth before nutritive tissue formation and, (ii) overcome any inadequate amounts in the host plant, post-nutritive tissue formation.

Optimization of Methodology for Rearing Spodoptera albula on Artificial Diet.

Advances in techniques for rearing insects on artificial diets are fundamental to solving issues of basic and applied entomology. In this study, we evaluated the development of Spodoptera albula (Walker) (Lepidoptera: Noctuidae) on three artificial diets used for other species of Lepidoptera, at three larval densities, and two densities of adult couples housed in oviposition cages of two sizes, with the aim of optimizing methodology for rearing S. albula in the laboratory. Biological parameters were recorded from S. albula, and a fitness index was calculated based on the larval survival and duration and weight of pupae. The total and daily oviposition was recorded using 5 or 10 adult couples of S. albula housed in two cage sizes. Concentrations of total nitrogen and protein in the tested diets were determined. Development of S. albula was completed in all artificial diets; however, the diet used for rearing Anticarsia gemmatalis (Hübner) larvae was the most suitable for S. albula, yielding intermediate development time and higher survival relative to the other diets. Individualization of larvae favored S. albula development by producing overall greater weights of larvae and pupae, higher survival rates, and longer adult longevity. Cage size and number of couples per cage did not influence S. albula fecundity in the experiment conditions. Spodoptera albula can be satisfactorily reared on the artificial diet used for A. gemmatalis, using one larva per tube, and either density of adults at any cage size. Additional amendments are needed in the rearing methodology to achieve optimal conditions for larval development to adulthood.

Yeast: An Overlooked Component of Bactrocera tryoni (Diptera: Tephritidae) Larval Gut Microbiota.

Yeasts, often in hydrolyzed form, are key ingredients in the larval and adult diets of tephritid fruit fly colonies. However, very little is known about the presence or role of yeasts in the diets of tephritid fruit flies in nature. Previous studies have identified bacteria but not detected yeasts in the gut of Queensland fruit fly, Bactrocera tryoni (Froggatt), one of Australia's most economically damaging insect pests of horticultural crops and of significant biosecurity concern domestically and internationally. Here we demonstrate that cultivable yeasts are commonly found in the gut of B. tryoni larvae from fruit hosts. Analysis of the ITS1, 5.8S rRNA gene, and ITS2 sequences of randomly selected isolates identified yeasts and yeast-like fungi of the genera Aureobasidium, Candida, Cryptococcus, Hanseniaspora, Pichia, and Starmerella. The prevalence of these yeasts in fruits suggests that larvae consume the yeasts as part of their diet. This work highlights that yeasts should be considered in future tephritid larval gut microbiota studies. Understanding tephritid-microbial symbiont interactions will lead to improvements in artificial diets and the quality of mass-reared tephritids for the sterile insect technique.

Manipulation of host plant cells and tissues by gall-inducing insects and adaptive strategies used by different feeding guilds.

Biologists who study insect-induced plant galls are faced with the overwhelming diversity of plant forms and insect species. A challenge is to find common themes amidst this diversity. We discuss common themes that have emerged from our cytological and histochemical studies of diverse neotropical insect-induced galls. Gall initiation begins with recognition of reactive plant tissues by gall inducers, with subsequent feeding and/or oviposition triggering a cascade of events. Besides, to induce the gall structure insects have to synchronize their life cycle with plant host phenology. We predict that reactive oxygen species (ROS) play a role in gall induction, development and histochemical gradient formation. Controlled levels of ROS mediate the accumulation of (poly)phenols, and phytohormones (such as auxin) at gall sites, which contributes to the new cell developmental pathways and biochemical alterations that lead to gall formation. The classical idea of an insect-induced gall is a chamber lined with a nutritive tissue that is occupied by an insect that directly harvests nutrients from nutritive cells via its mouthparts, which function mechanically and/or as a delivery system for salivary secretions. By studying diverse gall-inducing insects we have discovered that insects with needle-like sucking mouthparts may also induce a nutritive tissue, whose nutrients are indirectly harvested as the gall-inducing insects feeds on adjacent vascular tissues. Activity of carbohydrate-related enzymes across diverse galls corroborates this hypothesis. Our research points to the importance of cytological and histochemical studies for elucidating mechanisms of induced susceptibility and induced resistance.

Effects of New Dietary Ingredients Used in Artificial Diet for Screwworm Larvae (Diptera: Calliphoridae).

Spray-dried whole bovine blood, dry poultry egg, and a dry milk substitute are the constituents of the artificial diet currently used for mass rearing screwworm larvae, Cochliomyia hominivorax (Coquerel) (Diptera: Calliphoridae). Due to high cost and uncertainty of the commercial supply of spray-dried blood, research was conducted to identify alternative, locally available, inexpensive, dietary ingredients which could reduce cost of rearing and eliminate concerns of short supply. Experimental diets were prepared without blood component and with various ratios of bovine blood or blood cell product and defatted soy flour. Results indicate that spray-dried bovine blood can be replaced by a readily available and less expensive blood cell product. When the quantity of whole dried blood or blood cell component was reduced or removed completely from the diet, the larvae did not feed adequately, resulting in high mortality. Those larvae that survived produced pupae that were of unacceptable quality. When the milk product was replaced by soy flour, pupae were slightly smaller than those reared using the current diet; however, replacement of egg product with soy flour produced even smaller pupae. Longevity of adult flies that emerged from these small pupae was short and the females deposited few eggs. These results indicate that soy flour cannot replace the blood component from the diet, but can replace the milk product successfully. It is likely that some factor or a combination of factors in the blood act as feeding stimulants, without which larvae are unable to feed normally, resulting in high larval mortality.

Jasmonate-dependent depletion of soluble sugars compromises plant resistance to Manduca sexta.

Jasmonates regulate plant secondary metabolism and herbivore resistance. How they influence primary metabolites and how this may affect herbivore growth and performance are not well understood. We profiled sugars and starch of jasmonate biosynthesis-deficient and jasmonate-insensitive Nicotiana attenuata plants and manipulated leaf carbohydrates through genetic engineering and in vitro complementation to assess how jasmonate-dependent sugar accumulation affects the growth of Manduca sexta caterpillars. We found that jasmonates reduce the constitutive and herbivore-induced concentration of glucose and fructose in the leaves across different developmental stages. Diurnal, jasmonate-dependent inhibition of invertase activity was identified as a likely mechanism for this phenomenon. Contrary to our expectation, both in planta and in vitro approaches showed that the lower sugar concentrations led to increased M. sexta growth. As a consequence, jasmonate-dependent depletion of sugars rendered N. attenuata plants more susceptible to M. sexta attack. In conclusion, jasmonates are important regulators of leaf carbohydrate accumulation and this determines herbivore growth. Jasmonate-dependent resistance is reduced rather than enhanced through the suppression of glucose and fructose concentrations, which may contribute to the evolution of divergent resistance strategies of plants in nature.

Characterization of Adult Transcriptomes from the Omnivorous Lady Beetle Coleomegilla maculata Fed Pollen or Insect Egg Diet.

Diet, nutrition, and obesity are important topics of current research. While many insect genome and/or transcriptome models are based on dietary specialists, the lady beetle Coleomegilla maculata, a common New World species, is highly omnivorous. C. maculata feeds on plants, fungi, insects and other arthropods; its diet frequently includes conspecific cannibalism. This study reports and discusses the first nutritionally based C. maculata transcriptomes. These transcriptomes were prepared from highly inbred specimens provided limited diets, after adult eclosion, of either pollen only or eggs of a soft bodied hemipteran insect only. Selected sequences from the transcriptomes were compared to verify basic genetic similarity of the sampled individuals. Differentially expressed genes associated with these diets were identified to aid with studies of omnivore diet and nutrition. Selected transcriptome sequences described herein are filed with the National Center for Biotechnology Information (NCBI), GenBank Bioproject PRJNA236444.

Multiorganismal insects: diversity and function of resident microorganisms.

All insects are colonized by microorganisms on the insect exoskeleton, in the gut and hemocoel, and within insect cells. The insect microbiota is generally different from microorganisms in the external environment, including ingested food. Specifically, certain microbial taxa are favored by the conditions and resources in the insect habitat, by their tolerance of insect immunity, and by specific mechanisms for their transmission. The resident microorganisms can promote insect fitness by contributing to nutrition, especially by providing essential amino acids, B vitamins, and, for fungal partners, sterols. Some microorganisms protect their insect hosts against pathogens, parasitoids, and other parasites by synthesizing specific toxins or modifying the insect immune system. Priorities for future research include elucidation of microbial contributions to detoxification, especially of plant allelochemicals in phytophagous insects, and resistance to pathogens; as well as their role in among-insect communication; and the potential value of manipulation of the microbiota to control insect pests.

A dieta alimentar da presa Tenebrio molitor (Coleoptera: Tenebrionidae) pode afetar o desenvolvimento do predador Podisus nigrispinus (Heteroptera: Pentatomidae)? / Can the diet of the prey Tenebrio molitor (Coleoptera: Tenebrionidae) affect the development of the predator Podisus nigrispinus (Heteroptera: Pentatomidae)?

Inimigos naturais são importantes para o controle de pragas em culturas agrícolas e florestais. A criação de insetos predadores em biofábricas deve ser de baixo custo para serem utilizados em programas de Manejo Integrado de Pragas (MIP). O objetivo deste trabalho foi avaliar o desenvolvimento de Podisus nigrispinus Dallas, 1851 (Heteroptera: Pentatomidae), alimentado com larvas de Tenebrio molitor Linnaeus, 1758 (Coleoptera: Tenebrionidae), criadas com as seguintes dietas: farelo de trigo, ração triturada ou peletizada para aves poedeiras e fubá de milho. Foram obtidos os parâmetros de desenvolvimento e reprodução necessários para calcular a tabela de vida do predador. Os parâmetros da tabela de vida revelaram crescimento populacional em todos os tratamentos. No entanto, a taxa líquida de reprodução (Ro) de P. nigrispinus foi menor quando alimentados com larvas de T. molitor criadas com fubá de milho, mostrando ser a alimentação menos adequada para esse predador. Por proporcionar maior número total de ovos, o farelo de trigo constituiu a melhor dieta para P. nigrispinus. Estudos sobre dietas de presas alternativas são importantes, pois podem favorecer a nutrição de inimigos naturais e, consequentemente, melhorar o desempenho das criações massais em laboratório.(AU)

Natural enemies are important for controlling pests in agricultural and forestry culture. The reproductions of predatory insects in biofactories should have low cost to be used in Integrated Pest Management Program (IPM). The objective of this study was to evaluate the development of Podisus nigrispinus Dallas, 1851 (Heteroptera: Pentatomidae) fed with Tenebrio molitor Linnaeus, 1758 (Coleoptera: Tenebrionidae). The larvae of T. molitor were created with the following diets: wheat bran, shredded or pelleted poultry feed layers and corn meal. Parameters for the development and reproduction of the P. nigrispinus were obtained. Parameters of the life table show population growth in all treatments. However, the net rate of reproduction (Ro) of P. nigrispinus was lower when they were fed with larvae of T. molitor created with corn meal, which proved to be the least adequate food for this predator. By providing a larger total number of eggs, wheat bran was the best diet for P. nigrispinus. Studies on alternative prey diets are important as they may favor the nutrition of natural enemies and, consequently, improve the performance in laboratory rearing.(AU)

Expression of insulin/insulin-like signalling and TOR pathway genes in honey bee caste determination.

The development of queen and worker castes in honey bees is induced by differential nutrition, with future queens and workers receiving diets that are qualitatively and quantitatively different. We monitored the gene expression of 14 genes for components of the insulin/insulin-like signalling and TOR pathways in honey bee larvae from 40-88 h after hatching. We compared normally fed queen and normally fed worker larvae and found that three genes showed expression differences in 40-h-old larvae. Genes that show such early differences in expression may be part of the mechanism that transduces nutrition level into a hormone signal. We then compared changes in expression after shifts in diet with those in normally developing queens and workers. Following a shift to the worker diet, the expression of 9/14 genes was upregulated in comparison with queens. Following a shift to the queen diet, expression of only one gene changed. The honey bee responses may function together as a homeostatic mechanism buffering larvae from caste-disrupting variation in nutrition. The different responses would be part of the canalization of both the queen and worker developmental pathways, and as such, a signature of advanced sociality.

The impact of microbial symbionts on host plant utilization by herbivorous insects.

Herbivory, defined as feeding on live plant tissues, is characteristic of highly successful and diverse groups of insects and represents an evolutionarily derived mode of feeding. Plants present various nutritional and defensive barriers against herbivory; nevertheless, insects have evolved a diverse array of mechanisms that enable them to feed and develop on live plant tissues. For decades, it has been suggested that insect-associated microbes may facilitate host plant use, and new molecular methodologies offer the possibility to elucidate such roles. Based on genomic data, specialized feeding on phloem and xylem sap is highly dependent on nutrient provisioning by intracellular symbionts, as exemplified by Buchnera in aphids, although it is unclear whether such symbionts play a substantive role in host plant specificity of their hosts. Microorganisms present in the gut or outside the insect body could provide more functions including digestion of plant polymers and detoxification of plant-produced toxins. However, the extent of such contributions to insect herbivory remains unclear. We propose that the potential functions of microbial symbionts in facilitating or restricting the use of host plants are constrained by their location (intracellular, gut or environmental), and by the fidelity of their associations with insect host lineages. Studies in the next decade, using molecular methods from environmental microbiology and genomics, will provide a more comprehensive picture of the role of microbial symbionts in insect herbivory.

New protein sources in adults diet for mass-rearing of Anastrepha fraterculus (Diptera:Tephritidae)

The aim of this study was to find alternatives to reduce the cost of mass production of the South American fruit fly (A. fraterculus) by looking for locally available products as protein source in the diet of adults to replace the imported product without changing the quality parameters. Two yeast from a Brazilian company were evaluated. The quality parameters showed that the imported hydrolyzed yeast used in the adult diet could be perfectly replaced by the local products tested, with a reduction of over 80% of the cost of the diet. The quality of the produced insects remained the same and there were improvements in some quality parameters such as the volume of eggs produced, number of adults flying and longevity under the stress.

Sexually differentiated flight responses of the Mexican bean beetle to larval and adult nutrition.

Flight of male and female Mexican bean beetle adults was examined in laboratory tests. The experimental design made it possible to examine flight behavior not only with respect to different types of hosts (young vs senescent common bean foliage) but also with respect to effects due to their utilization during particular stages of beetle development. The median flight time of males was significantly affected by the adult host, but not by the juvenile host; whereas, the median flight time of females tended to be more affected by the juvenile than by the adult host. These different effects of hosts on the flight times of males and females resulted in sexual dimorphism in flight when the sexes were fed senescent foliage as adults. Although age significantly affected the flight time of both males and females, the reproductive status of females did not affect their flight times. The significance of these results are discussed with respect to the influence of the nutritional complexity of habitats on life history strategies and population dynamics.