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Simple Summary Efficient and proper functioning of processes within living organisms play key roles in times of climate change and strong human pressure. In insects, the most abundant group of organisms, many important changes occur within their tissues, including the fat body, which plays a key role in the development of insects. Fat body cells undergo numerous metabolic changes in basic energy compounds (i.e., lipids, carbohydrates, and proteins), enabling them to move and nourish themselves. In addition to metabolism, the fat body is involved in the development of insects by determining the time an individual becomes an adult, and creates humoral immunity via the synthesis of bactericidal proteins and polypeptides. As an important tissue that integrates all signals from the body, the processes taking place in the fat body have an impact on the functioning of the entire body. Abstract The biodiversity of useful organisms, e.g., insects, decreases due to many environmental factors and increasing anthropopressure. Multifunctional tissues, such as the fat body, are key elements in the proper functioning of invertebrate organisms and resistance factors. The fat body is the center of metabolism, integrating signals, controlling molting and metamorphosis, and synthesizing hormones that control the functioning of the whole body and the synthesis of immune system proteins. In fat body cells, lipids, carbohydrates and proteins are the substrates and products of many pathways that can be used for energy production, accumulate as reserves, and mobilize at the appropriate stage of life (diapause, metamorphosis, flight), determining the survival of an individual. The fat body is the main tissue responsible for innate and acquired humoral immunity. The tissue produces bactericidal proteins and polypeptides, i.e., lysozyme. The fat body is also important in the early stages of an insect’s life due to the production of vitellogenin, the yolk protein needed for the development of oocytes. Although a lot of information is available on its structure and biochemistry, the fat body is an interesting research topic on which much is still to be discovered.

International audience; An efficient antioxidant system is of particular importance for insects whose high metabolic rates promote increased formation of reactive oxygen species (ROS). The amount of ROS can be additionally increased by environmental factors. This study investigates the ability of red mason bees (Osmia bicornis L.) to inactivate free radicals during insect development. Both male and female bees were studied, from the larval to the active imago stage. The activity of four antioxidant enzymes, superoxide dismutase, catalase, peroxidase and glutathione S-transferase, was measured; and glutathione content and total antioxidant status were determined. The highest values of the examined parameters were found in feeding stages-in larvae and in active imagines of both genders. Significant differences between genders were noted mainly in catalase activity, which was lower in overwintering imagines and active females than in males. Most differences were observed between females and males after emergence.

Bees of the genus Osmia are being used in crop pollination at an increasing rate. However, a short life expectancy of adult individuals limits the feasibility of their use. Cocoons of the red mason bee, Osmia rufa L. (Hymenoptera: Megachilidae), can be stored at 4° C in a postdiapause state, and adult bees can be used for pollination outside their natural flight period. The period of storage in this form has an unfavorable influence on the survival rate, life expectancy, and fertility of the bee. It was suggested that the negative results are connected with exhaustion of energy reserves. To test this hypothesis, the present study examined the contents of protein, carbohydrates, lipids, and the activities of some enzymes, and their degradation in red mason bees that emerged in spring according to their biological clock and in summer after elongated diapause. It was found that postdiapause artificially elongated by 3 months caused significant decreases in body weight, total sugar, glycogen, lipids, and protein content in O. rufa. Glucose level was highest in bees that emerged in the summer, which was coincident with increased activities of maltase and trehalase. The activities of sucrase and cellobiase were not changed, while amylase activity was considerably decreased. The activities of triacylglycerols lipase and C2, C4, C10 carboxylesterases were highest in bees that emerged in July. Low temperatures restrict O. rufa emergence, and during prolonged postdiapause, metabolic processes lead to significant reductions of structural and energetic compounds.

The effect of hexane, dichloromethane, ethyl acetate and hydroalcoholic fractions obtained from ethanolic extract of Trichilia pallida, T. pallens and Toona ciliata on growth and nutritional physiology of Spodoptera frugiperda was evaluated. First instar larvae were fed on a diet treated with fractions for ten days. The most active fractions were applied on the diet and offered to larvae until the pupal stage to verify effects on growth and survival. To calcúlate the nutritional indices, fractions were incorporated into the diet offered to fourth instar larvae for four days. The dichloromethane fraction of T. pallens stems affected growth and survival of S. frugiperda larvae, and fractions of T. pallida leaves and stems, and of To. ciliata leaves and fruits affected larval growth. Nutritional analysis indicated that the fraction of To. ciliata leaves acts mainly as a phagodeterrent, while dichlorometane fractions of T. pallida stems and leaves, To. ciliata fruits and T. pallens stems cause toxic effects after ingestion, reducing the efficiency of food conversion and increasing the metabolic cost to the larvae. e evaluó el efecto de fracciones de hexano, diclorometano, acetato de etilo e hidroalcohólica, obtenidas a partir del extracto de etanol de Trichilia pallida, Trichilia pallens y Toona ciliata sobre el crecimiento y fisiología nutricional de Spodoptera frugiperda. Larvas de primer estadio se alimentaron con dieta tratada con dichas fracciones durante diez días. Las fracciones más activas fueron aplicadas sobre la dieta y se ofrecieron a las larvas hasta pupa para verificar efectos sobre el crecimiento y sobrevivencia. Para calcular los índices nutricionales, la dieta con las fracciones fueron ofrecidas a las larvas de cuarto estadio durante cuatro días. La fracción de diclorometano de ramas de T. pallens afectó el crecimiento y la sobrevivencia de las larvas. Por otra parte, las fracciones de diclorometano de ramas y hojas de T. pallida y hojas y frutos de To. ciliata afectaron el crecimiento larval. El análisis nutricional indicó que la fracción de hojas de To. ciliata actúa principalmente como disuasor de alimentación mientras que las fracciones de diclorometano de ramas y hojas de T. pallens, frutas de To. ciliata y ramas de T. pallens causan efectos tóxicos después de la ingestión, reduciendo la eficiencia de conversión de alimento y aumentando el costo metabólico para las larvas.

Regulatorische Peptide, zu denen Neuropeptide und Peptidhormone zählen, sind Signalmoleküle, die der Zell-Zell-Kommunikation dienen und an der Kontrolle vielfältiger biologischer Prozesse in Insekten und anderen vielzelligen Tieren beteiligt sind. Wie der Verdauungstrakt von Säugetieren enthält auch der Mitteldarm der Insekten zahlreiche peptidbildende endokrine Zellen, wobei die Diversität der enteroendokrinen Insekten-Peptide deren Bedeutung für den Stoffwechsel, die Energiebalance und die Nahrungsaufnahme erahnen lässt. In der ersten Studie haben wir das Mitteldarm-Peptidom von adulten und larvalen Drosophila melanogaster charakterisiert. Dafür wurden die Peptide aus dem Mitteldarmgewebe extrahiert und anschließend ihre Strukturen mittels LC-MS/MS analysiert. Auf diese Weise konnten wir 24 Peptide identifizieren, die von 9 verschiedenen Peptid-Vorläufermolekülen abstammen. Alle Darmpeptide konnten in identischer Form im ZNS nachgewiesen werden und stellen somit „brain-gut“-Peptide dar. Es wurde bereits gezeigt, dass für die Prozessierung von Neuropeptidhormonen in Drosophila die Subtilisin-ähnliche Proprotein-Konvertase 2 (dPC2, AMON) erforderlich ist. Unsere Ergebnisse legen nahe, dass AMON generell auch für die Bildung von Darmpeptiden benötigt wird. Mit der zweiten Studie konnten wir die Kenntnis von Peptidstrukturen in wichtigen Insekten weiter ausbauen. Wir haben das Peptidom der Kohlmade (d.h. der Larve der Kleinen Kohlfliege Delia radicum) untersucht, welche durch Wurzelfraß bedeutenden landwirtschaftlichen Schaden verursacht. Durch die massenspektrometrische Analyse von ZNS, Neurohämalorganen und Därmen konnten wir 38 Peptide aus diversen Insektenpeptidfamilien charakterisieren. Zudem konnten wir ein neues Peptid identifizieren, das Sequenzähnlichkeit zum Eclosionshormon-Vorläufermolekül bei einigen Drosophila-Arten aufweist. Die immuncytochemische Untersuchung von peptidbildenden Neuronen und enteroendokrinen Zellen zeigte, dass die Verteilung der Peptide in larvalen Drosophila und Delia sehr ähnlich ist. Die gefundenen Übereinstimmungen bei beiden Arten sprechen dafür, dass Drosophila im Hinblick auf die peptiderge Regulation z. B. des Stoffwechsels als genetisch zugängliches Modell für Schadinsekten dienen kann. In Zukunft könnten unsere Ergebnisse für die Entwicklung einer peptidbasierten Strategie zum zielgerichteten Management der Kohlfliege genutzt werden. In der dritten Studie haben wir die Rolle von Allatostatin A (AstA) untersucht – einer Peptidfamilie, die typischerweise in Insekten (und anderen Arthropoden) vorkommt. In vorangegangenen Studien konnte bereits demonstriert werden, dass AstA eine Rolle für die Regulation des Stoffwechsels und der Nährstoffhomöostase in Drosophila spielt. Wir haben uns der Frage gewidmet, ob sich spezifische Effekte auf die Aktivität bestimmter Subsets der zahlreichen bei adulten Taufliegen vorkommenden AstA-produzierenden Zellen zurückführen lassen. AstA-Neurone finden sich in verschiedenen Regionen des ZNS, außerdem enthält der Thorax mehrere periphere AstA-Neurone. Der Enddarm sowie der posteriore Mitteldarm werden von zentralen AstA-Neuronen innerviert. Zusätzlich existieren zahlreiche AstA-produzierende enteroendokrine Zellen, die im Epithel des posterioren Mitteldarms verstreut liegen. Die thermogenetische Aktivierung bestimmter AstA-Zellen führte dazu, dass die Nahrungsaufnahme der Fliegen signifikant reduziert und die lokomotorische Aktivität beträchtlich vermindert war. Die Kombination unserer Daten mit den Ergebnissen einer vorangegangenen Studie legte nahe, dass zwei Paar AstA-bildende Neurone des posterioren lateralen Protocerebrums das Sättigungsgefühl stimulieren, wohingegen die enteroendokrinen AstA-Zellen die Lokomotion regulieren. Weiterhin deuteten unsere Ergebnisse darauf hin, dass AstA-Zellen die Defäkation direkt und indirekt zu beeinflussen scheinen, wohingegen kein Effekt auf Wasser- und Ionenhomöostase festgestellt werden konnte. Außerdem haben wir mittels in vitro-Versuch die Wirkung von synthetischen AstA-Peptiden auf isolierte Mitteldärme getestet und konnten eine dosisabhängige Inhibition der Mitteldarmmotilität feststellen. Eine Verminderung der AstA-Rezeptor-mRNA in der Darmmuskulatur mittels RNAi zeigte, dass der Rezeptor DAR-2 den myoinhibitorischen Effekt der AstA-Peptide vermittelt. Alles in allem scheinen AstA-Zellen, indem sie das Sättigungsempfinden, die Lokomotion, die Darmperistaltik und möglicherweise auch die Defäkation steuern, verschiedene Ebenen des Stoffwechsels und unterschiedliche Gewebe zu beeinflussen, und dabei mehrere mit der Nahrungsaufnahme sowie auch untereinander in Verbindung stehende Prozesse zu fördern., Regulatory peptides, which comprise neuropeptides and peptide hormones, are cell-cell signaling molecules that control a variety of biological processes in insects and other metazoans. The insect midgut, like the mammalian digestive system, contains numerous peptide-producing endocrine cells, and the diversity of insect enteroendocrine peptides gives a hint at their relevance for metabolism, energy balance and feeding behavior. In the first study, we characterized the midgut peptidome of adult and larval Drosophila melanogaster by extraction of peptides from midgut tissue and subsequent LC-MS/MS analysis of peptide structures. By this means we identified 24 peptides originating from 9 different peptide precursors. All gut peptides were found in identical form within the CNS and thus represent brain-gut peptides. Processing of Drosophila neuropeptide hormones was previously shown to require the subtilisin-like proprotein convertase 2 (dPC2, AMON). Our results suggest a general need of AMON for gut peptide production as well. In the second study, we could expand the knowledge on peptide structures of relevant insects. We investigated the peptidome of the cabbage maggot (i.e., the larva of the cabbage root fly Delia radicum), which causes substantial agricultural damage by feeding on plant roots. By mass spectrometric analysis of CNS, neurohemal organ and gut tissue, we could characterize 38 peptides belonging to diverse insect peptide families. Moreover, we identified a new peptide with sequence similarity to the eclosion hormone precursor of several Drosophila species. Immunocytochemical characterization of peptide-producing neurons and enteroendocrine cells in cabbage maggots showed that peptide distribution was largely similar to Drosophila larvae. The observed similarities in the peptidergic systems of both species suggest that Drosophila can serve as a genetically accessible pest species model in terms of peptidergic regulation of, e.g., metabolism. In the future, our results could be of use for the development of a targeted, peptide-based management of cabbage root flies. In the third study, we analyzed the role of allatostatin A (AstA), a peptide family commonly occurring in insects (and other arthropods). Previous studies had already demonstrated a role for AstA in metabolic regulation and nutritional homeostasis of Drosophila. We addressed the question whether specific effects were connected to the activity of certain subsets of the numerous AstA-producing cells found in adult fruit flies. AstA neurons are located in different regions of the CNS. The thorax also contains a few peripheral AstA neurons. The hindgut and the posteriormost portion of the midgut are innervated by central AstA neurons. In addition, a large number of enteroendocrine AstA cells are scattered across the epithelium of the posterior midgut. Thermogenetic activation of certain AstA cells significantly reduced food intake of flies, and also considerably diminished their locomotor activity. The combination of our results with findings of a previous study suggested that two pairs of AstA-producing posterior lateral protocerebrum neurons function to promote satiety, while enteroendocrine AstA cells seem to regulate locomotor activity. In addition, our findings indicated that AstA cells might directly and indirectly influence defecation behavior, while no effect on water and ion homeostasis could be observed. Furthermore, we tested the effect of synthetic AstA peptides on isolated midguts in vitro and observed a dose-dependent inhibition of midgut motility. Downregulation of AstA receptor mRNA in the gut musculature via RNAi showed that the DAR-2 receptor mediates the myoinhibitory effect of AstA peptides. Altogether, by influencing satiety, locomotion, gut peristalsis and possibly also defecation, AstA cells appear to affect different levels of metabolism and different tissues, seemingly promoting several interrelated processes connected to food intake.