Apoptosis and Autophagy in the Midgut Epithelium ofAcheta domesticus(Insecta, Orthoptera, Gryllidae)

Research Progress on the Regulation of Autophagy and Apoptosis in Insects by Sterol Hormone 20-Hydroxyecdysone

20E (20-Hydroxyecdysone) is a central steroid hormone that orchestrates developmental changes and metamorphosis in arthropods. While its molecular mechanisms have been recognized for some time, detailed elucidation has primarily emerged in the past decade. PCD (Programmed cell death), including apoptosis, necrosis, efferocytosis, pyroptosis, ferroptosis, and autophagy, plays a crucial role in regulated cell elimination, which is vital for cells' development and tissue homeostasis. This review summarizes recent findings on 20E signaling regulated autophagy and apoptosis in insects, including Drosophila melanogaster, Bombyx mori, Helicoverpa armigera, and other species. Firstly, we comprehensively explore the biosynthesis of the sterol hormone 20E and its subsequent signal transduction in various species. Then, we focus on the involvement of 20E in regulating autophagy and apoptosis, elucidating its roles in both developmental contexts and bacterial infection scenarios. Furthermore, our discussion unfolds as a panoramic exposition, where we delve into the fundamental questions with our findings, anchoring them within the grander scheme of our study in insects. Deepening the understanding of 20E-autophagy/apoptosis axis not only underscores the intricate tapestry of endocrine networks, but also offers fresh perspectives on the adaptive mechanisms that have evolved in the face of environmental challenges.

Hazards related to the presence of cadmium in food - Studies on the European soil centipede, Lithobius forficatus

The soil is an environment rich in numerous potentially toxic substances/elements when present at elevated concentrations. They can be transported through the successive levels of the trophic chain. Animals living in a contaminated environment or eating contaminated food can accumulate potentially toxic elements in their bodies. One of the potentially toxic metals is cadmium, which accumulates significantly in soils. The aim of our research was to evaluate the changes caused by cadmium supplied with the food administered to invertebrates living in uncontaminated soil. The results were compared with those obtained for animals raised in contaminated soil, where cadmium entered the body via the epidermis. As the material for studies, we chose a common European soil centipede, Lithobius forficatus. Adult specimens were divided into the following experimental groups: C - control animals, Cd12 and Cd45 - animals fed with Chironomus larvae maintained in water containing 80 mg/l CdCl₂, for 12 and 45 days, respectively. The material was analyzed using qualitative and quantitative analysis (transmission electron microscopy, confocal microscopy, flow cytometry, atomic absorption spectrometry). Eventually, we can conclude that the digestive system is an effective barrier against the effects of toxic metals on the entire organism, but among the gonads, ovaries are more protected than testes, however, this protection is not sufficient. Accumulation of spherites and mitochondrial alterations are probably involved in survival mechanisms of tissues after Cd intoxication.

Impact of copper sulfate on survival, behavior, midgut morphology, and antioxidant activity of Partamona helleri (Apidae: Meliponini)

Copper sulfate (CuSO₄) is widely used in agriculture as a pesticide and foliar fertilizer. However, the possible environmental risks associated with CuSO₄ use, particularly related to pollinating insects, have been poorly studied. In this study, we evaluated both lethal and sublethal effects of CuSO₄ on the stingless bee Partamona helleri. Foragers were orally exposed to five concentrations of CuSO₄ (5000, 1666.7, 554.2, 183.4, 58.4 μg mL^-1), and the concentration killing 50% (LC₅₀) was estimated. This concentration (142.95 μg mL^-1) was subsequently used in behavioral, midgut morphology, and antioxidant activity analyses. Bee mortality increased with the ingestion of increasing concentrations of CuSO₄. Ingestion at the estimated LC₅₀ resulted in altered walking behavior and damage to the midgut epithelium and peritrophic matrix of bees. Furthermore, the LC₅₀ increased the catalase or superoxide dismutase activities and levels of the lipid peroxidation biomarker malondialdehyde. Furthermore, the in situ detection of caspase-3 and LC3, proteins related to apoptosis and autophagy, respectively, revealed that these processes are intensified in the midgut of treated bees. These data show that the ingestion of CuSO₄ can have considerable sublethal effects on the walking behavior and midgut of stingless bees, and therefore could pose potential risks to pollinators including native bees. Graphical abstract.

A collective analysis of lifespan-extending compounds in diverse model organisms, and of species whose lifespan can be extended the most by the application of compounds

Research on aging and lifespan-extending compounds has been carried out using diverse model organisms, including yeast, worms, flies and mice. Many studies reported the identification of novel lifespan-extending compounds in different species, some of which may have the potential to translate to the clinic. However, studies collectively and comparatively analyzing all the data available in these studies are highly limited. Here, by using data from the DrugAge database, we first identified top compounds in terms of their effects on percent change in average lifespan of diverse organisms, collectively (n = 1728). We found that, when data from all organisms studied were combined for each compound, aspirin resulted in the highest percent increase in average lifespan (52.01%), followed by minocycline (27.30%), N-acetyl cysteine (17.93%), nordihydroguaiaretic acid (17.65%) and rapamycin (15.66%), in average. We showed that minocycline led to the highest percent increase in average lifespan among other compounds, in both Drosophila melanogaster (28.09%) and Caenorhabditis elegans (26.67%), followed by curcumin (11.29%) and gluconic acid (5.51%) for D. melanogaster and by metformin (26.56%), resveratrol (15.82%) and quercetin (9.58%) for C. elegans. Moreover, we found that top 5 species whose lifespan can be extended the most by compounds with lifespan-extending properties are Philodina acuticornis, Acheta domesticus, Aeolosoma viride, Mytilina brevispina and Saccharomyces cerevisiae (211.80%, 76%, 70.26%, 55.18% and 45.71% in average, respectively). This study provides novel insights on lifespan extension in model organisms, and highlights the importance of databases with high quality content curated by researchers from multiple resources, in aging research.

Toxicity and cytopathology mediated by Bacillus thuringiensis in the midgut of Anticarsia gemmatalis (Lepidoptera: Noctuidae)

Bioinsecticides and transgenic plants, based on Bacillus thuringiensis (Bt) toxins are important when managing Anticarsia gemmatalis Hübner (Lepidoptera: Noctuidae), a soybean defoliator pest. The interaction of these toxins with the caterpillar’s midgut cells determines their efficacy as an insecticide. The objective was to evaluate the toxicity of B. thuringiensis, subsp. kurstaki strain HD-1 and cytopathological changes mediated by these bacterial toxins in the midgut of A. gemmatalis caterpillars. Insecticidal efficacy was determined by calculating lethal concentration values (LC₂₅, LC₅₀, LC₇₅, LC₉₀ and LC₉₉) in the laboratory. Midgut fragments from A. gemmatalis were extracted after bacterial ingestion and evaluated by light, transmission electron and confocal microscopy. The Bt median lethal concentrations showed toxicity [LC₅₀ = 0.46 (0.43–0.49) mg mL⁻¹] to fourth instar A. gemmatalis caterpillars after 108 hours. Bt induces severe cytotoxicity to A. gemmatalis midgut epithelial cells with increasing exposure over time, causing cellular disorganization, microvillus degeneration, cell fragmentation and protrusion, peritrophic membrane rupture, and cell vacuolization. The cell nuclei presented condensed chromatin and an increase in lysosome numbers. Apoptosis occurred in the midgut cells of caterpillars exposed to Bt. A regenerative response in A. gemmatalis caterpillars was observed 8 hours after exposure to Bt, however this response was not continuous. Toxins produced by Bt are harmful to A. gemmatalis at median concentration with structural damage and death of the midgut epithelial cells of this insect.

Novel budding mode in Polyandrocarpa zorritensis: a model for comparative studies on asexual development and whole body regeneration

Background

In tunicates, the capacity to build an adult body via non-embryonic development (NED), i.e., asexual budding and whole body regeneration, has been gained or lost several times across the whole subphylum. A recent phylogeny of the family Styelidae revealed an independent acquisition of NED in the colonial species Polyandrocarpa zorritensis and highlighted a novel budding mode. In this paper, we provide the first detailed characterization of the asexual life cycle of P. zorritensis.

Results

Bud formation occurs along a tubular protrusion of the adult epidermis, the stolon, in a vascularized area defined as budding nest. The bud arises through a folding of the epithelia of the stolon with the contribution of undifferentiated mesenchymal cells. This previously unreported mode of bud onset leads to the formation of a double vesicle, which starts to develop into a zooid through morphogenetic mechanisms common to other Styelidae. The budding nest can also continue to accumulate nutrients and develop into a round-shaped structure, designated as spherule, which represents a dormant form able to survive low temperatures.

Conclusions

To understand the mechanisms of NED and their evolution, it is fundamental to start from a robust phylogenetic framework in order to select relevant species to compare. The anatomical description of P. zorritensis NED provides the foundation for future comparative studies on plasticity of budding and regeneration in tunicates.

Electronic supplementary material

The online version of this article (10.1186/s13227-019-0121-x) contains supplementary material, which is available to authorized users.

Autophagy and apoptosis in starved and refed Neocaridina davidi (Crustacea, Malacostraca) midgut

Adult specimens of the freshwater shrimp Neocaridina davidi Bouvier, 1904 (Crustacea) were starved for 7, 14, and 21 days. Specimens from the first and second experimental group were collected for the studies. The majority of animals starved for 21 days died. Additionally, some specimens from each group were refed for 4, 7, and 14 days. The epithelium of the midgut, which is composed of the intestine and hepatopancreas, was analyzed. While the epithelium of the intestine is formed by D- and R-cells, the epithelium of the hepatopancreas has R-, B-, and F-cells. Autophagy and apoptosis in the midgut epithelium were analyzed using transmission electron microscopy and immunohistochemical methods. These processes were only observed in the D-cells of the intestine and the F- and B-cells of the hepatopancreas. Starvation led to a reduction in the amount of reserve material in the B-cells. Although this process activated autophagy in both regions of the midgut, the intestine and hepatopancreas, after refeeding, the level of autophagy decreased. Starvation caused an increase in the apoptotic cells in both organs, while the refeeding caused a decrease in the number of apoptotic cells in both organs analyzed. Refeeding after periods of starvation caused an accumulation of reserve material in the hepatopancreas.

Autophagy-Associated Shrinkage of the Hepatopancreas in Fasting Male Macrobrachium rosenbergii Is Rescued by Neuropeptide F

Invertebrate neuropeptide F-I (NPF-I), much alike its mammalian homolog neuropeptide Y, influences several physiological processes, including circadian rhythms, cortical excitability, stress response, and food intake behavior. Given the role of autophagy in the metabolic stress response, we investigated the effect of NPF-1 on autophagy during fasting and feeding conditions in the hepatopancreas and muscle tissues of the male giant freshwater prawn Macrobrachium rosenbergii. Starvation up-regulated the expression of the autophagy marker LC3 in both tissues. Yet, based on the relative levels of the autophagosome-associated LC3-II isoform and of its precursor LC3-I, the hepatopancreas was more responsive than the muscle to starvation-induced autophagy. Injection of NPF-I inhibited the autophagosome formation in the hepatopancreas of fasting prawns. Relative to the body weight, the muscle weight was not affected, while that of the hepatopancreas decreased upon starvation and NPF-1 treatment could largely prevent such weight loss. Thus, the hepatopancreas is the reserve organ for the nutrient homeostasis during starvation and NPF-I plays a crucial role in the balancing of energy expenditure and energy intake during starvation by modulating autophagy.

A new TK model approach to assess the effect of migration on copper toxicokinetics in inbred populations of the flour beetle, Tribolium castaneum

The aim of the study was to determine the influence of migration on copper (Cu) kinetics of male Tribolium castaneum after 25 generations of exposure for Cu-adapted and non-Cu-adapted inbred lines. Adapted lines were kept on a flour medium contaminated with 1000 mg Cu kg^-1. A medium contaminated with 2000 mg Cu kg^-1 of copper was used during the intoxication phase. Based on our data and literature reports, we introduced a new two-phase four-stage toxicokinetics (TK) model. The intoxication phase was successfully divided into three stages with separate assimilation rate constant (k_a) and elimination rate constant (k_e) values. The influence of migration was examined by comparing k_a and k_e parameters confidence intervals. In non-contaminated environments, migrants significantly increased k_a and k_e values in the second stage. Migrants decreased the maximum Cu accumulation observed in the experiment. The results indicated that the TK model must show high goodness-of-fit to be a useful tool for comparing treatments.

Short-term in vivo exposure to graphene oxide can cause damage to the gut and testis

Graphene oxide (GO) has unique physicochemical properties and also has a potentially widespread use in every field of daily life (industry, science, medicine). Demand for nanotechnology is growing every year, and therefore many aspects of its toxicity and biocompatibility still require further clarification. This research assesses the in vivo toxicity of pure and manganese ion-contaminated GO that were administrated to Acheta domesticus with food (at 200mgkg^-1 of food) throughout their ten-day adult life. Our results showed that short-term exposure to graphene oxide in food causes an increase in the parameters of oxidative stress of the tested insects (catalase - CAT, total antioxidant capacity - TAC), induces damage to the DNA at a level of approximately 35% and contributes to a disturbance in the stages of the cell cycle and causes an increase of apoptosis. Moreover, upon analyzing histological specimens, we found numerous degenerative changes in the cells of the gut and testis of Acheta domesticus as early as ten days after applying GO. A more complete picture of the GO risk can help to define its future applications and methods for working with the material, which may help us to avoid any adverse effects and damage to the animal.

Ultrastructure of the gut epithelium in Acheta domesticus after long-term exposure to nanodiamonds supplied with food

The biosafety of nanoparticles and the potential toxicity of nanopollutants and/or nanowastes are all currently burning issues. The increased use of nanoparticles, including nanodiamonds (ND), entails the real risk of their penetration into food chains, which may result in the contamination of animal and, as a result, human food. Knowledge about changes in the ultrastructure of tissues in organisms that have been exposed to ND is still very limited. The aim of the study was to describe the ultrastructure of the gut epithelium in Acheta domesticus after exposure to different concentrations of ND (0, 20 or 200 μg g(-1) - control, ND20 and ND200 groups, respectively) administered with food over a five-week period. The ultrastructure of the foregut, midgut and hindgut was assessed using Transmission Electron Microscopy (TEM). A number of changes in the structure of the gut in crickets that had consumed nanodiamond-contaminated food were observed. The epithelium of the midgut and hindgut were clearly damaged by ND, although the foregut was not affected. A positive relationship between the ND concentration in food and the degree of damage to the structure of epithelial cells was observed. Autophagy, especially mitophagy and reticulophagy, was activated in relation to the appearance of ND particles. A putative ND toxicity mechanizm is proposed. Extreme caution should be maintained when using nanodiamonds on a large scale.

How toxic is the depleted uranium to crayfish Procambarus clarkii compared with cadmium?

Due to a lack of information on the assessment of uranium's (U) toxicity, our work aimed to compare the effects of U on the crayfish Procambarus clarkii with those of the well documented metal: cadmium (Cd). Accumulation and impacts at different levels of biological organization were assessed after acute (40 µM Cd or U; 4-10 days) and chronic (0.1 µM Cd or U; 30-60 days) exposures. The survival rates demonstrated the high tolerance of this species toward both metals and showed that Cd had a greater effect on the sustainability of crayfish. The concentration levels of Cd and U accumulated in gills and hepatopancreas were compared between both conditions. Distinctions in the adsorption capacities and the mobility of the contaminants were suspected. Differences in the detoxification mechanisms of both metals using transmission electron microscopy equiped with an energy dispersive X-ray were also pointed out. In contrast, comparison between the histological structures of contaminated hepatopancreas showed similar symptoms. Principal component analyses revealed different impacts of each metal on the oxidative balance and mitochondria using enzymatic activities and gene expression levels as endpoints. The observation that U seemed to generate more oxidative stress than Cd in our conditions of exposure is discussed.

Metamorphic changes in abdominal spines of Forcipomyia nigra pupae (Diptera: Ceratopogonidae)

Pupae of Forcipomyia nigra biting midges bear double rows of dorsal and lateral spines. Their arrangement corresponds to the distribution of larval mechanosensory setae. They are serrated simple cuticular structures with tubercles but, in contrast to larval secretory mechanoreceptors, they are not innervated and do not exhibit any pores. The ultrastructure of abdominal spines varies among different pupal stages. They are produced by epidermal cells which fill the interior of the spine. In the youngest pupae epidermal cells are tightly packed and adhere to the cuticle. Then, the cells withdraw from the spinal cavity and the beginning of autophagy is observed. The last stage represents abdominal spines without any cellular material and then apoptosis probably proceeds in the withdrawn epidermal cells. Since the pupal spines occupied the same region of the segment as the larval setae, we consider that the same genes are responsible for their formation as for the formation of epidermal cells but that their mechanosensory and secretory function is no longer needed.

Ultrastructural analysis of apoptosis and autophagy in the midgut epithelium of Piscicola geometra (Annelida, Hirudinida) after blood feeding

Cell death in the endodermal region of the digestive tract of the blood-feeding leech Piscicola geometra was analyzed using light and transmission electron microscopes and the fluorescence method. Sexually mature specimens of P. geometra were bred under laboratory conditions and fed on Danio rerio. After copulation, the specimens laid cocoons. The material for our studies were non-feeding juveniles collected just after hatching, non-feeding adult specimens, and leeches that had been fed with fish blood (D. rerio) only once ad libitum. The fed leeches were prepared for our studies during feeding and after 1, 3, 7, and 14 days (not sexually mature specimens) and some weeks after feeding (the sexually mature). Autophagy in all regions of the endodermal part of the digestive system, including the esophagus, the crop, the posterior crop caecum (PCC), and the intestine was observed in the adult non-feeding and feeding specimens. In fed specimens, autophagy occurred at very high levels--in 80 to 90 % of epithelial cells in all four regions. In contrast, in adult specimens that did not feed, this process occurred at much lower levels--about 10 % (esophagus and intestine) and about 30 % (crop and PCC) of the midgut epithelial cells. Apoptosis occurred in the feeding adult specimens but only in the crop and PCC. However, it was absent in the non-feeding adult specimens and the specimens that were collected during feeding. Moreover, neither autophagy nor apoptosis were observed in the juvenile, non-feeding specimens. The appearance of autophagy and apoptosis was connected with feeding on toxic blood. We concluded that autophagy played the role of a survival factor and was involved in the protection of the epithelium against the products of blood digestion. Quantitative analysis was prepared to determine the number of autophagic and apoptotic cells.

Autophagic activity in the midgut gland of the overwintering harvestmen Gyas annulatus (Phalangiidae, Opiliones)

Juvenile harvestmen Gyas annulatus overwinter in dormancy in hypogean habitats for 4-5 months. The ultrastructure of the autophagic structures in their midgut epithelium cells was studied by light microscopy, transmission electron microscopy (TEM) and immunofluorescence microscopy (IFM) during this non-feeding period. Before overwintering (November), autophagic structures were scarce. In the middle (January) and at the end of overwintering (March), phagophores, autophagosomes and autolysosomes were present in the cytoplasm of both the secretory and the digestive midgut epithelium cells, gradually increasing their abundance during overwintering. In addition, vacuolization of the cytoplasm intensified. Both processes are induced by starvation. Autophagic structures and cytoplasm vacuolization enable the reuse of the cell's own components required for the maintenance of vital processes during dormancy. While TEM is a much more convenient method for recognition of the autophagic structure types and their ultrastructure, IFM enables exact counting of these structures.

Mitochondrial gene expression, antioxidant responses, and histopathology after cadmium exposure

The present study investigates cadmium effects on the transcription of mitochondrial genes of Procambarus clarkii after acute (0.05, 0.5, and 5 mg Cd/L; 4-10 days) and chronic exposures (10 μg Cd/L; 30-60 days). Transcriptional responses of cox1, atp6, and 12S using quantitative real-time RT-PCR were assessed in gills and hepatopancreas. Additionally, the expression levels of genes involved in detoxification and/or oxidative stress responses [mt, sod(Mn)] and enzymatic activities of antioxidants (SOD, CAT, GPX, and GST) were analyzed. The histopathological effects in hepatopancreas of crayfish were evaluated by light microscopy. Relationships between endpoints at different levels of biological organization and Cd bioaccumulation were also examined. Cd induced high levels of bioaccumulation, which was followed by mitochondrial dysfunction and histological alterations in both experiments. Moreover, perturbations in the defence mechanisms against oxidative stress tended to increase with time. Results also showed that molecular responses can vary depending on the intensity and duration of the chemical stress applied to the organisms and that the study of mt gene expression levels seemed to be the best tool to assess Cd intoxication.

Effects of neem oil (Azadirachta indica A. Juss) on the replacement of the midgut epithelium in the lacewing Ceraeochrysa claveri during larval-pupal metamorphosis

Larvae of the lacewing Ceraeochrysa claveri were fed on eggs of Diatraeasaccharalis treated with neem oil at concentrations of 0.5%, 1% and 2% throughout the larval period. Pupae obtained from treated larvae were used in the study at five days after the completion of cocoon spinning to investigate the effects of neem oil on the replacement of the midgut epithelium during the larval-pupal transition. We observed that the old larval epithelium was shed into the midgut lumen and transformed into the yellow body. Old cells from the yellow body were destroyed by apoptosis and autophagy and were not affected by neem oil. However, neem oil did affect the new pupal epithelium. Cells from treated pupae showed cellular injuries such as a loss of microvilli, cytoplasmic vacuolization, an increase of glycogen stores, deformation of the rough endoplasmic reticulum and dilation of the perinuclear space. Additionally, the neem oil treatment resulted in the release of cytoplasmic protrusions, rupture of the plasma membrane and leakage of cellular debris into the midgut lumen, characteristics of cell death by necrosis. The results indicate that neem oil ingestion affects the replacement of midgut epithelium, causing cytotoxic effects that can alter the organism's physiology due to extensive cellular injuries.

The fine structure of the midgut epithelium in a centipede, Scolopendra cingulata (Chilopoda, Scolopendridae), with the special emphasis on epithelial regeneration

Scolopendra cingulata has a tube-shaped digestive system that is divided into three distinct regions: fore-, mid- and hindgut. The midgut is lined with a pseudostratified columnar epithelium which is composed of digestive, secretory and regenerative cells. Hemocytes also appear between the digestive cells of the midgut epithelium. The ultrastructure of three types of epithelial cells and hemocytes of the midgut has been described with the special emphasis on the role of regenerative cells in the protection of midgut epithelium. The process of midgut epithelium regeneration proceeds due to the ability of regenerative cells to proliferate and differentiate according to a circadian rhythm. The regenerative cells serve as unipotent stem cells that divide in an asymmetric manner. Additionally, two types of hemocytes have been distinguished among midgut epithelial cells. They enter the midgut epithelium from the body cavity. Because of the fact that numerous microorganisms occur in the cytoplasm of midgut epithelial cells, we discuss the role of hemocytes in elimination of pathogens from the midgut epithelium. The studies were conducted with the use of transmission electron microscope and immunofluorescent methods.

The toxicokinetics cell demography model to explain metal kinetics in terrestrial invertebrates

Metal toxicokinetics in invertebrates are usually described by one-compartment first-order kinetic model. Although the model gives an adequate description of the toxicokinetics in certain cases, it has been shown to fail in some situations. It also does not seem acceptable on purely theoretical grounds as accumulation and excretion rates may change depending on instantaneous toxicant concentration in the gut. We postulate that the mechanism behind such changes is connected with the toxic effect of metals on gut epithelial cells. Based on published data, we have constructed a mechanistic model assuming a dynamic rate of replacement of epithelial cells with increasing contamination. We use a population-type modeling, with a population of gut epithelial cells characterized by specific death and birth rates, which may change depending on the metal concentration in food. The model shows that the equilibrium concentration of a toxicant in an organism is the net result of gut cell death and replacement rates. At low constant toxicant concentrations in food, the model predicts that toxicant-driven cell mortality is moderate and the total amount of toxicant in the intestine increases slowly up to the level resulting from the gradual increase of the cell replacement rate. At high constant concentration, total toxicant amount in the gut increases very fast, what is accompanied by massive cell death. The increased cell death rate results in reduced toxicant absorption, which in turn brings its body load down. The resulting pattern of toxicokinetic trajectory for high metal concentration closely resemble that found in empirical studies, indicating that the model probably describes the actual phenomenon.

The role of autophagy in the midgut epithelium of Eubranchipus grubii (Crustacea, Branchiopoda, Anostraca)

Eubranchipus grubii (Crustacea, Branchiopoda, Anostraca) is an omnivorous filter feeder whose life span lasts no more than 12 weeks. Adult males and females of E. grubii were used for ultrastructural studies of the midgut epithelium and an analysis of autophagy. The midgut epithelium is formed by columnar digestive cells and no regenerative cells were observed. A distinct regionalization in the distribution of organelles appears - basal, perinuclear and apical regions were distinguished. No differences in the ultrastructure of digestive cells were observed between males and females. Autophagic disintegration of organelles occurs throughout the midgut epithelium. Degenerated organelles accumulate in the neighborhood of Golgi complexes, and these complexes presumably take part in phagophore and autophagosome formation. In some cases, the phagophore also surrounds small autophagosomes, which had appeared earlier. Fusion of autophagosomes and lysosomes was not observed, but lysosomes are enclosed during autophagosome formation. Autophagosomes and autolysosomes are discharged into the midgut lumen due to apocrine secretion. Autophagy plays a role in cell survival by protecting the cell from cell death.