The ultrastructural investigation of the midgut in the quill mite Syringophilopsis fringilla (Acari,Trombidiformes: Syringophilidae)

The midgut of the females of Syringophilopsis fringilla (Fritsch) composed of anterior midgut and excretory organ (=posterior midgut) was investigated by means of light and transmission electron microscopy. The anterior midgut includes the ventriculus and two pairs of midgut caeca. These organs are lined by a similar epithelium except for the region adjacent to the coxal glands. Four cell subtypes were distinguished in the epithelium of the anterior midgut. All of them evidently represent physiological states of a single cell type. The digestive cells are most abundant. These cells are rich in rough endoplasmic reticulum and participate both in secretion and intracellular digestion. They form macropinocytotic vesicles in the apical region and a lot of secondary lysosomes in the central cytoplasm. After accumulating various residual bodies and spherites, the digestive cells transform into the excretory cells. The latter can be either extruded into the gut lumen or bud off their apical region and enter a new digestive cycle. The secretory cells were not found in all specimens examined. They are characterized by the presence of dense membrane-bounded granules, 2–4 μm in diameter, as well as by an extensive rough endoplasmic reticulum and Golgi bodies. The ventricular wall adjacent to the coxal glands demonstrates features of transporting epithelia. The cells are characterized by irregularly branched apical processes and a high concentration of mitochondria. The main function of the excretory organ (posterior midgut) is the elimination of nitrogenous waste. Formation of guanine-containing granules in the cytoplasm of the epithelial cells was shown to be associated with Golgi activity. The excretory granules are released into the gut lumen by means of eccrine or apocrine secretion. Evacuation of the fecal masses occurs periodically. Mitotic figures have been observed occasionally in the epithelial cells of the anterior midgut.     

Digestive cells in the midgut of Triatoma vitticeps (Stal, 1859) in different starvation periods

Triatoma vitticeps (Stal, 1859) is a hematophagous Hemiptera that, although being considered wild, can be found in households, being a potential Chagas’ disease vector. This work describes the histology and ultrastructure of the midgut of T. vitticeps under different starvation periods. Fifteen adults of both sexes starved for 3, 7, 20 and 25 days were studied. In general, digestive cells had apical microvilli, basal plasma membrane infoldings and central nucleus. The perimicrovillar membrane was found in all insects examined. Digestive cells of anterior midgut had lipid droplets, glycogen granules, developed basal labyrinth associated with mitochondria suggesting their role in nutrient storage and in fluid and ion transport. The cells of median and posterior regions of the midgut were rich in rough endoplasmic reticulum, lysosomes, vesicles and granules with different electron-densities. Moreover, cells of the posterior portion of the midgut had hemozoyn granules and mitochondria in the apical cytoplasm close to microvilli, suggesting their role in blood digestion and active nutrient absorption. The midgut of T. vitticeps showed differences in digestive cells associated with the time after feeding, and the increase of vesicles amount in long starvation periods, which suggests enzyme storage, which is readily used after a blood meal.     

The haemoxisome: a haem-iron containing structure in the Rhodnius prolixus midgut cells

Rhodnius prolixus midgut was analysed using transmission electron microscopy and electron spectroscopic imaging in order to localize the cellular structures involved in haem metabolism. In the posterior midgut, special cellular electron-dense structures were observed. These structures are here designated haemoxisomes. Haemoxisomes are present in the epithelial cells at various time points after a blood meal. Several days after the blood meal, some of them become less electron-dense. By electron spectroscopic imaging, large amounts of iron and oxygen were detected in these cellular structures. The iron is probably bound to the porphyrin ring as an iron-protoporphyrin IX complex, as detected using the diaminobenzidine technique. An interesting observation was the presence of endoplasmic reticulum surrounding the haemoxisomes during some special periods. Iron content was monitored in the posterior midgut epithelium and was found to be constant at the initial days after a blood meal, but slightly higher at the end of the digestive process (from 13th up to 20th day). These results are in agreement with the observation that the appearance of the haemoxisomes changes at the end of the digestive process. The ability to degrade haem seems to depend on the presence of endoplasmic reticulum as observed using a haem degradation assay in the presence of an endoplasmic reticulum-enriched fraction. Taken together these results suggest that haemoxisomes may play a role in intracellular haem detoxification.     

The fine structure of the midgut in the mite Anystis baccarum (L.) (Acari, Actinedida: Anystidae)

The ventriculus and the midgut caeca of the fed females of Anystis baccarum (L.) were investigated by using light and electron microscopy. In addition to the main type of polyfunctional digestive cells, special secretory cells were detected in the anterior region of the ventriculus. The shape and the ultrastructure of the digestive cells vary depending on their physiological state. Intracellular digestion, absorption or excretion processes prevail at different stages of the cell cycle. The secretory cells are characterized by the presence of extensive rough endoplasmic reticulum, filling whole space of the cell. These cells do not contain the apical network of pinocytotic canals, which are typical for the digestive cells. Three types of secretory granules were found in the cytoplasm of the secretory cells that probably correspond to three sequential stages of granulogenesis. The primary secretory granules are formed by the fusion of Golgi vesicles. The primary granules fuse to form complex vesicles with heterogeneous contents. These secondary granules aggregate to form very large inclusions of high electron density (tertiary secretory granules), which probably represent the storage of the secretory product. All types of secretory granules were observed close to the apical plasmalemma.     

Cellular details of the midgut of Cryptocellus boneti (Arachnida: Ricinulei)

The midgut of Cryptocellus boneti was studied by light and electron microscopy. The epithelia of the diverticula and of the anterior part of the midgut tube are composed of two cell types: digestive and secretory. In contrast, the epithelia of posterior part of the midgut tube and of the stercoral pocket consist of one type of cells only. In some places, parts of the midgut system are connected by an intermediate tissue. Digestive cells are characterized by an apical system of tubules, nutritional vacuoles, and spherites; characteristic features of secretory cells are secretory granules and a prominent rough endoplasmic reticulum. Cells of the midgut tube appear not to be involved in the absorption of food. © 1994 Wiley-Liss, Inc.     

Electron microscopic study of the anterior midgut in Cenocorixa bifida Hung. (Hemiptera: Corixidae) with reference to its secretory function

The epithelium of anterior midgut of adult Cenocorixa bifida was examined with light and electron microscopy. The folded epithelium is composed of tall columnar cells extending to the lumen, differentiating dark and light cells with interdigitating apices and regenerative basal cells in the nidi surrounded by villiform ridges that penetrate deeply into the epithelium. The columnar cells display microvilli at their luminal surface. Microvilli lined intercellular spaces and basal plasma membrane infoldings are associated with mitochondria. These ultrastructural features suggest their role in absorption of electrolytes and nutrients from the midgut lumen. The columnar cells contain large oval nuclei with prominent nucleoli. Their cytoplasm is rich in rough endoplasmic reticulum, Golgi complexes and electron-dense secretory granules indicating that they are also engaged in synthesis of digestive enzymes. The presence of secretory granules in close proximity of the apical plasma membrane suggests the release of secretion is by exocytosis. The presence of degenerating cells containing secretory granules at the luminal surface and the occurance of empty vesicles and cell fragments in the lumen are consistent with the holocrine secretion of digestive enzymes. Apical extrusions of columnar cells filled with fine granular material are most likely formed in response to the lack of food in the midgut. The presence of laminated concretions in the cytoplasm is indicative of storageexcretion of surplus minerals. The peritrophic membrane is absent from the midgut of C. bifida.     

Ultrastructural changes of the midgut epithelium in Isohypsibius granulifer granulifer Thulin, 1928 (Tardigrada: Eutardigrada) during oogenesis

The midgut epithelium of Isohypsibius granulifer granulifer (Eutardigrada) is composed of columnar digestive cells. At its anterior end, a group of cells with cytoplasm which differs from the cytoplasm of digestive cells is present. Probably, those cells respond to crescent-like cells (midgut regenerative cells) described for some tardigrade species. Their mitotic divisions have not been observed. We analyzed the ultrastructure of midgut digestive cells in relation to five different stages of oogenesis (previtellogenesis, beginning of the vitellogenesis, vitellogenesis—early choriogenesis, vitellogenesis—middle choriogenesis, late choriogenesis). In the midgut epithelium cells, the gradual accumulation of glycogen granules, lipid droplets and structures of varying electron density occurs. During vitellogenesis and choriogenesis, in the cytoplasm of midgut cells we observed the increasing number of organelles which are responsible for the intensive synthesis of lipids, proteins and saccharides such as cisterns of endoplasmic reticulum and Golgi complexes. At the end of oogenesis, autophagy also intensifies in midgut epithelial cells, which is probably caused by the great amount of reserve material. Midgut epithelium of analyzed species takes part in the yolk precursor synthesis.     

Autophagy as the cell survival in response to a microsporidian infection of the midgut epithelium of Isohypsibius granulifer granulifer (Eutardigrada: Hypsibiidae)

The midgut epithelial cells of many invertebrates may possess microorganisms which act as symbionts or pathogens (bacteria, microsporidia, viruses). During our previous studies on Isohypsibius granulifer granulifer Thulin, 1928 (Tardigrada, Eutardigrada), which examined alterations of the midgut epithelium during oogenesis, we found that some of the specimens were infected with microsporidia. All stages of pathogens occurred in the cytoplasm of the digestive cells in the midgut epithelium of I. g. granulifer that were infected with microsporidia: meronts, sporonts, sporoblasts, and spores. The cytoplasm of the digestive cells was rich in mitochondria, cisterns of rough endoplasmic reticulum (RER), and Golgi complexes. Autophagy in the digestive cells of the dorsal midgut was much more intensive in comparison with noninfected specimens. Membranes of phagophores surrounded the pathogens forming autophagosomes. These latter structures fused with lysosomes forming autolysosomes and residual bodies appeared. Neither glycogen granules nor droplets of varying electron density, which accumulated in digestive cells during vitellogenesis and choriogenesis, appeared in individuals with microsporidia. While the midgut epithelium in noninfected specimens takes part in vitellogenesis and choriogenesis, in infected specimens, midgut cells are involved in the process of autophagy as a survival strategy.     

Structure of the apical cells of the testis of the tenebrionid beetles: Tenebrio molitor and Zophobas rugipes

The developmental cytology of the apical tissue of the testis of Tenebrio molitor and Zophobas rugipes was studied with light and electron microscopy. In the early larvae of both species the tisue was found to be a thickened protrusion of nongerminal cells appearing at the apical end of each testis follicle following gonadal differentiation. The cells persist through pupal and adult stages in both species, becoming more prominent at these stages in Z. rugipes, despite tracheal invasion in both species. In older adults the apical tissue regresses and ultimately distintegrates. Ultrastructurally the apical cells are distinguished from adjacent germinal cells by their (1) small, rounded or oval nuclei, (2) highly convoluted plasma membrane, (3) electron-opaque cytoplasm, (4) profuse concentrically-stacked, granular endoplasmic reticulum, (5) large aggregates of glycogen-like granules, (6) numerous small, tubular mitochondria, (7) well-developed Golgi centers and (8) striking arrays of microtubules. These cells have many cytological features in common with the androgenic gland cells of crustaceans, but not with the steroidogenic cells of vertebrates. Evidence for the formation of protein granules is also lacking. As yet, experimental procedures have not indicated an endocrine function for these cells in tenebrionids. However, their cytology is consistent with secretory activity of some kind.     

取食转Bt基因抗虫玉米后亚洲玉米螟幼虫中肠的组织病理变化

利用透射显微镜（TEM）观察亚洲玉米螟Ostrinia furnacalis (Guenée)幼虫取食了表达Cry1Ab杀虫蛋白的转Bt基因玉米心叶组织后中肠的组织病理变化, 以探讨转Bt基因玉米对亚洲玉米螟的致病机理, 为其合理、安全和持续利用提供理论依据。结果表明：亚洲玉米螟取食Bt玉米后中肠细胞及其细胞器发生了明显的病变。取食Bt玉米12 h后中肠细胞开始病变, 首先微绒毛脱落、内质网开始肿胀, 24 h后内质网肿胀、增多, 杯状细胞杯腔增大, 48 h后微绒毛大量脱落, 细胞开始空泡化, 随着取食时间的增加, 细胞空泡化程度加剧, 在感染前期细胞间的病变程度差异较大。微绒毛脱落、内质网肿胀断裂是在多数取食Bt玉米的亚洲玉米螟中肠细胞发生的普遍病变。由此表明, 人工修饰的Cry1Ab基因导入到玉米染色体组中所表达的杀虫蛋白可使玉米螟幼虫中肠细胞发生病变, 最终导致其死亡。     

Functional morphology of adult female Culex quinquefasciatus midgut during blood digestion

The adult female Culex quinquefasciatus midgut comprises a narrow anterior and a dilated posterior region, with epithelia composed of a monolayer of adjacent epithelial cells joined at the apical portion by septate junctions. Densely packed apical microvilli and an intricate basal labyrinth characterise each cell pole. Our morphological studies suggest that, during blood digestion, the anterior midgut region also participates in an initial absorptive stage which is probably related to the intake of water, salts and other small molecules. This activity peaked by 6h after bloodmeal feeding (ABF) and ended approximately 18 h ABF, when the peritrophic membrane was already formed. After this time, absorption only occurred in the posterior region, with morphologic and biochemical evidence of high synthetic activity related to the secretion of proteases. Chymotrypsin, elastase, aminopeptidase, and trypsin reached their maximum activity at around 36 h ABF. Digestion products were apparently absorbed and transported to the basal labyrinth, from where they should be released to the hemolymph. At 72 h ABF, proteolysis had already ended and protein levels had returned to those observed before blood meal. The epithelium of the posterior region, however, did not return to its initial morphology, appearing quite disorganised. Additionally, from 48 h ABF onwards some epithelial cells showed morphological signals of apoptosis.     

A contribution to the functional morphology of the midgut gland in phalangiid harvestmen Gyas annulatus and Gyas titanus during their life cycle

The structure of the midgut gland and its changes in different seasons have been examined in the harvestmen Gyas annulatus and Gyas titanus (Arachnida: Opiliones: Phalangiidae). In both species, in the epithelium of the midgut gland two different types of cells are present: secretory and digestive ones. The secretory cells are characterized by plentiful rER and secretory granula. The digestive cells are characterized by an apical system of tubules. Both cells are connected by prominent specialized junctions. If a secretory cell is in contact with a digestive cell, rER cisterna are in close vicinity and parallel to these junctions. As found light- and electron microscopically and also histochemically, glycogen and lipids are stored in both cells. In both species, glycogen was seen to be used as energy compound during overwintering. At the end of their life, the digestive cells develop into excretory ones, containing metabolic wastes.     

中华硬蜱叮咬不同免疫力新西兰兔后中肠上皮组织的形态动态变化

通过光镜和电镜观察了中华硬蜱Ixodes sinensis叮咬初次和再次感染宿主新西兰兔后不同时间（叮咬后24 h、48 h、72 h以及第 5天、第8天）中肠上皮组织的形态学动态变化。结果显示： 中华硬蜱叮咬前中肠上皮主要由替代细胞和少量体积较大的消化细胞构成;替代细胞数量多、体积小、呈圆形、胞质染色浅 。中华硬蜱叮咬初次感染宿主后,消化细胞随叮咬时间延长而增多增大,微绒毛较密集,排列整齐,胞质内细胞器丰富,各单位膜结构清晰,并出现顶端小管、小泡、大量脂滴和高铁血红素颗粒;近基膜的细胞膜内褶形成发达的基底迷路系统。中华硬蜱叮咬再次感染宿主后,中肠可发生一系列明显的病理变化,中肠基膜出现变薄、松散和断裂现象,消化细胞破裂、空泡化,消化细胞数量减少;消化细胞微绒毛减少、变短、排列不整,线粒体肿大,体嵴减少、变短甚至髓样变,粗面内质网扩张,脂粒及高铁血红素颗粒减少,细胞膜吞饮、吞噬现象减弱,消化细胞内结构紊乱和破坏。该研究结果提示初次叮咬导致了宿主的免疫抗性,再次叮咬后蜱中肠是宿主免疫力的主要作用部位。     

Cellular organization and peritrophic membrane formation in the cardia (Proventriculus) of Drosophila melanogaster

The peritrophic membrane of Drosophila melanogaster consists of four layers, each associated with a specific region of the folded epithelial lining of the cardia. The epithelium is adapted to produce this multilaminar peritrophic membrane by bringing together several regions of foregut and midgut, each characterized by a distinctively differentiated cell type. The very thin, electron-dense inner layer of the peritrophic membrane originates adjacent to the cuticular surface of the stomadeal valve and so appears to require some contribution by the underlying foregut cells. These foregut cells are characterized by dense concentrations of glycogen, extensive arrays of smooth endoplasmic reticulum, and pleated apical plasma membranes. The second and thickest layer of the peritrophic membrane coalesces from amorphous, periodic acid-Schiff-positive material between the microvilli of midgut cells in the neck of the valve. The third layer of the peritrophic membrane is composed of fine electron-dense granules associated with the tall midgut cells of the outer cardia wall. These columnar cells are characterized by cytoplasm filled with extensive rough endoplasmic reticulum and numerous Golgi bodies and by an apical projection filled with secretory vesicles and covered by microvilli. The fourth, outer layer of the peritrophic membrane originates over the brush border of the cuboidal midgut cells, which connect the cardia with the ventriculus.     

Histological and ultrastructural characterization of the alimentary system of solifuges (Arachnida,Solifugae)

Solifuges are voracious and fast predators. Once having captured a prey item, mostly small arthropods or even small vertebrates, they start feeding on their prey by constant chewing movements with their huge chelicerae. At the same time, they squeeze out the soft tissue that passes the anterior lattice‐like part of the mouthparts. The digestion of the food takes place in the midgut, which is anatomically highly complex. It consists of the midgut tube from which numerous prosomal and opisthosomal diverticula and tubular lateral branches arise. The dimorphic epithelium of the midgut tube and the diverticula is constituted of digestive and secretory cells. The digestive cells are characterized by an apical tubulus system and contain nutritional vacuoles, lipids, spherites, and glycogen. Secretory cells contain a huge amount of rough endoplasmic reticulum and secretory vacuoles. The lateral branches are ultrastructurally similar to Malpighian tubules and are likely involved in excretion. In contrast to the midgut, the epithelium of the hindgut consists of only one type of cell overlain by a thin cuticle. Digested residuals are stored in the hindgut until defecation. J. Morphol., 2010. © 2009 Wiley‐Liss, Inc.     

Cytological and enzyme-histochemical investigations on the digestive organs of Nautilus pompilius (Cephalopoda, Tetrabranchiata)

The foregut, stomach, caecum, midgut, and rectum of the digestive tract of Nautilus pompilius L.were investigated with ultrastructural and enzyme-cytological methods. Three different cell types were identified within the lamina epithelialis mucosae: main cells, goblet cells, and cells with secretory granules. The main cell type is the epithelial cell with microvilli, a basal nucleus surrounded by dictyosomes, rough endoplasmic reticulum, mitochondria, and electron-dense granules identified as lysosomes in the apical part of the cell. In the caecum this cell type contains endosymbiotic bacteria. The presence of endocytotic vesicles and the storage of lipids in the caecum indicate that this organ is involved in the process of absorption. In the caecum and the longitudinal groove of the rectum the main cells are, in addition, ciliated, facilitating the transport of food particles and faeces. Two types of goblet cells are found in all organs except in the stomach, forming a gliding path for food particles and protecting the epithelium. In the foregut and rectum, cells with electron-dense granules were recognized as the third type. The conspicuous secretory cells of the rectum represent a delimited rectal gland; its possible biological function is discussed. The tunica muscularis in all organs of the digestive tract consists of obliquely striated muscle cells innervated by axons containing transparent, osmiophilic and dense-cored vesicles. Positive reactions for acid and alkaline phosphatase, monoamine oxidase, β-glucuronidase, and trypsin- and chymotrypsin-like enzymes are localized in the lamina epithelialis mucosae.     

合哑蝉成虫消化道形态、组织结构及超微结构（英文）

【目的】本研究通过合哑蝉Karenia caelatata成虫消化道的形态学、组织学和超微结构研究,进一步了解蝉科(Cicadidae)代表种类的消化道形态和功能分化。【方法】利用光学显微镜和透射电子显微镜技术,对合哑蝉雄成虫消化道的整体形态以及食道、滤室(中肠前端及后端、马氏管基部、后肠基部)、滤室外中肠(锥形体、中肠环)、后肠(回肠、直肠)的一般形态和超微结构进行了详细观察,同时对滤室的组织结构进行了研究。【结果】结果表明,合哑蝉消化道由食道、滤室、滤室外中肠及后肠组成。食道狭长,被有上表皮和内表皮。中肠前端、中肠后端、马氏管基部以及后肠基部被一肌肉鞘包围形成滤室构造。组成中肠前端和后端的细胞基膜高度内褶,顶端的微绒毛发达。中肠后端分布许多线粒体和高电子密度的分泌颗粒。滤室外的中肠包括膨大的锥形体、中肠环。其中,锥形体由两种细胞组成;中肠环分为前、中、后3个不同的区段。前中肠细胞包含大量的分泌颗粒、线粒体、粗面内质网和溶酶体;中中肠细胞含有分泌颗粒;后中肠细胞包括许多低电子密度的分泌颗粒和滑面内质网。类铁蛋白颗粒零星分布于中肠环的前、中区段。组成锥形体和中肠环前端的细胞顶端微绒毛被丝状物质覆盖。后肠被有一层表皮。食道、中肠环中段、直肠细胞中含有微生物。【结论】本研究获得的合哑蝉消化道形态、组织结构和超微结构方面的信息为其功能分化研究提供了重要信息。同时,相关微生物的发现为进一步探讨共生菌与蝉总科昆虫的协同进化提供了信息。     

Toxic impact of ingested Jatropherol-I on selected enzymatic activities and the ultrastructure of midgut cells in silkworm, Bombyx mori L.

Abstract:  Jatropherol-I, a phorbol-type diterpene from Jatropha curcas seeds was found highly toxic to third instars silkworm larvae after ingestion with LC₅₀ values 0.5793, 0.2197 and 0.1578 mg/ml at 48, 72 and 120 h respectively. The acute toxicity was associated with changes in activities of several midgut enzymes and pathological changes in midgut epithelial cells. Jatropherol-I caused various fluctuations in activities of different midgut enzymes in third instars larvae of silkworm. Compared with controls, both esterase and carboxyliesterase showed significantly depressed activities at 3 h ( t -test, P < 0.05) and increased activities at 24 h and rapidly decreased activities at 48 h after ingestion of 0.125 and 0.25 mg/ml of Jatropherol-I. Jatropherol-I induced two (E4 and E5) and depressed one (E2) of midgut esterase isozymes analysed 3 h after ingestion. There was no significantly different glutathione S-transferase activity between most of treated silkworm and control ( t -test, P > 0.05). Activities of acetylcholinesterase fluctuated weakly in treated silkworm in 48 h. Jatropherol-I induced a gradual decline in midgut protease activities in silkworm with an obvious dose- and time-dependent effect. Jatropherol-I also caused pathological changes in midgut cells, especially in their endoplasmic reticulum. They were noted slight dilatation on 12 h exposure, while extreme dilatation, vesiculations and shedding of ribosome from membrane were observed in endoplasmic reticulum after a longer time exposure. Other pathological changes in microvilli, lysosome, mitochondria and chromatin were also observed in midgut cell of treated silkworm.     

Fine structure of the midgut epithelium in the developing brown shrimp,Penaeus aztecus

The midgut epithelium of larval and early postlarval brown shrimp has been studied with light and electron microscopy. Ultrastructurally the features of the midgut do not change during these stages of development. On the basis of electron density, two epithelial cell types can be distinguished, and these are referred to as light and dark cells. The dark cells contain more rough endoplasmic reticulum and more free ribosomes than the light cells. Mitochondria in the dark cells have a matrix which is less electron dense than the mitochondrial matrix of the light cells. Both cell types have a microvillous border with a surface coat. The microvilli lack microfilaments within their core, and a terminal web is not differentiated in the stages examined. Tubular smooth endoplasmic reticulum is abundant in the basal portions of the cells. Electron dense, membrane bound vesicles are consistently seen in association with the Golgi apparatus, apical cell surface, and gut lumen and therefore are believed to be secretory granules. Cells in the anterior portion of the midgut often contain very large lipid droplets in the cytoplasm.     

Morphology and ultrastructure of the alimentary canal of the cicada Platypleura kaempferi (Hemiptera: Cicadidae)

The alimentary canal of cicada Platypleura kaempferi is described. It comprises the oesophagus, filter chamber, external midgut section and hindgut. The elongate oesophagus expands posteriorly, with its posterior end constricting to become a bulb. The filter chamber consists of two parts: a very thin sheath and a filter organ. The filter organ is composed of the anterior and posterior ends of the midgut (internal midgut section), and the internal proximal ends of the Malpighian tubules. The external midgut section differentiates into a collapsed sac and a midgut loop. The latter is divided into three distinct segments. The hindgut contains a dilated rectum and a long narrow ileum. The distal portions of the four Malpighian tubules are enclosed in a peritoneal sheath together with the distal ileum before reaching to the rectum. Ultrastructurally, the oesophagus and the hindgut are lined with a cuticle. The filter chamber sheath consists of cells with large irregular nuclei. Filamentous substances coat the microvilli of the cells of the internal midgut section. The posterior end of the midgut comprises two types of cells, with the first type of cells containing many vesicles and scattered elements of rough endoplasmic reticulum. The anterior and posterior segments of the midgut loop cells have ferritin‐like granules. The ileum cells have well‐developed apical leaflets associated with mitochondria. Accumulations of virus‐like particles enclosed in the membrane are observed in the esophagus, conical segment, mid‐ and posterior segments of the midgut loop.