Characterization of the alimentary canal of the aphidophagous ladybird,Adalia bipunctata (Coleoptera: Coccinellidae): anatomical and histological approaches

The alimentary canal of the two‐spot ladybird Adalia bipunctata (Linnaeus) (Coleoptera: Coccinellidae) presents the foregut (stomodeum), the midgut (mesenteron) and the hindgut (proctodeum). The shortest region is the foregut and the longest is the midgut. The relative proportions of the main regions were found to be similar for males and females. In the foregut it was possible to distinguish the pharynx, the esophagus and the proventriculus but no crop. The hindgut is composed of the ileum, rectum and rectal canal. Generally the organ width is similar for males and females, but females presented a wider proventriculus. The epithelium of the foregut varied from squamous to simple cuboidal and columnar. In the midgut the epithelium is simple columnar with goblet and regenerative cells. The epithelium of the hindgut varied from simple cuboidal to squamous. Females presented thicker midgut epithelium whereas males presented thicker epithelium in the esophagus. The anatomy of the alimentary canal of A. bipunctata seems to conform to its carnivorous and recent phylogenetic status within the family Coccinellidae.     

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.     

光唇鱼消化道的形态结构特征

采用解剖及石蜡切片显微技术,观察研究了光唇鱼消化道的形态结构特征。消化道由口咽腔、食道、肠构成。口下位、马蹄形,无颌齿,具咽齿,齿式为4/4。舌较小,前端游离,舌粘膜表层为复层鳞状上皮,有较多的杯状细胞和味蕾。食道及肠均由粘膜层、粘膜下层、肌层及外膜构成。食道内皱襞发达,粘膜层有大量杯状细胞。肠道盘曲,由前、中、后肠组成,肠长/体长为1.84±0.24;前肠管腔较大,中、后肠管腔渐变小;前、中肠皱襞及纹状缘比后肠发达;前肠及后肠杯状细胞较少,中肠杯状细胞较多。光唇鱼消化道的形态结构特征与其食性相适应。     

仿刺参消化系统的组织学和组织化学研究

用组织学和组织化学方法研究了仿刺参的消化系统。消化道管壁由粘膜层、粘膜下层、肌层和外膜组成。粘膜层为假复层或单层的柱状细胞或立方细胞与粘液细胞。粘液细胞分布于前肠的前段和排泄腔。前肠和中肠上皮具蛋白酶、脂酶和非特异性酯酶活性。中肠上皮细胞游离端有密集微绒毛,游离端质膜呈碱性磷酸酶活性,上皮下有丰富的血窦,表明具吸收作用。     

The alimentary canal of <Emphasis Type="Italic">Blomia tropicalis</Emphasis> (Acari: Astigmata: Echymopodidae): the application of three-dimensional reconstruction technology

The domestic mite species Blomia tropicalis is an important indoor allergen source related to asthma and other allergic diseases in tropical and subtropical regions. Here, we describe the alimentary canal of B. tropicalis with the particular application of three-dimensional reconstruction technology. The alimentary canal of B. tropicalis resembles the typical acarid form consisting of the cuticle-lined foregut and hindgut separated by a cuticle-free midgut. The foregut is divided into a muscular pharynx and an esophagus. The midgut is composed of a central ventriculus, two lateral caeca, a globular colon and a postcolon with two tubiform postcolonic diverticula. The most common cells forming the epithelium of ventriculus and caeca are squamous and cuboidal. The globular cells contain a big central vacuole in the posterior region of the caeca. The epithelium of the colon and postcolon has significantly longer microvilli. The anal atrium is a simple tube with flattened epithelial cells. The spatial measurements of the three-dimensional model suggest that the paired caeca and central ventriculus occupy 55.1 and 34.6%, respectively, of the total volume of the alimentary canal and may play the key role in food digestion. J. Wu and F. Yang contributed equally.     

Morphology and histology of the digestive tract of Nautilus pompilius and Nautilus macromphalus (Cephalopoda, Tetrabranchiata)

 This study presents histological and scanning electron microscopical findings on the structural differentiation, and the nervous and vascular supply of the digestive tracts of Nautilus pompilius and N. macromphalus, including the foregut, stomach, vestibulum, caecum, midgut and rectum. The stereoscopic reconstruction of the vestibulocaecal complex gives an idea how the digestive cycle between the stomach, vestibulum, caecum and proximal midgut could possibly proceed. All parts of the digestive tract are covered luminally by a columnar epithelium which contains numerous goblet cells. The epithelium is ciliated in the vestibulum, caecum, proximal midgut and the longitudinal groove of the rectum. On this lamina epithelialis mucosae borders the lamina propria mucosae, which consists of connective tissue and some muscle cells. In the stomach it is differentiated, forming a special bolster-like layer. The lamina propria mucosae is followed by the tunica muscularis, which consists of a stratum circulare and a stratum longitudinale in the foregut, vestibulum, caecum, midgut and rectum. In the stomach, midgut and rectum, the tunica adventitia, which consists of a thin layer of connective tissue, is located between the tunica muscularis and the cuboidal tunica serosa. Accepted: 4 August 1997     

The larval alimentary canal of the Antarctic insect, Belgica antarctica

On the Antarctica continent the wingless midge, Belgica antarctica (Diptera, Chironomidae) occurs further south than any other insect. The digestive tract of the larval stage of Belgica that inhabits this extreme environment and feeds in detritus of penguin rookeries has been described for the first time. Ingested food passes through a foregut lumen and into a stomodeal valve representing an intussusception of the foregut into the midgut. A sharp discontinuity in microvillar length occurs at an interface separating relatively long microvilli of the stomodeal midgut region, the site where peritrophic membrane originates, from the midgut epithelium lying posterior to this stomodeal region. Although shapes of cells along the length of this non-stomodeal midgut epithelium are similar, the lengths of their microvilli increase over two orders of magnitude from anterior midgut to posterior midgut. Infoldings of the basal membranes also account for a greatly expanded interface between midgut cells and the hemocoel. The epithelial cells of the hindgut seem to be specialized for exchange of water with their environment, with the anterior two-thirds of the hindgut showing highly convoluted luminal membranes and the posterior third having a highly convoluted basal surface. The lumen of the middle third of the hindgut has a dense population of resident bacteria. Regenerative cells are scattered throughout the larval midgut epithelium. These presumably represent stem cells for the adult midgut, while a ring of cells, marked by a discontinuity in nuclear size at the midgut-hindgut interface, presumably represents stem cells for the adult hindgut.     

Anatomy and fine structure of the alimentary canal of the spittlebug Lepyronia coleopterata (L.) (Hemiptera: Cercopoidea)

The alimentary canal of the spittlebug Lepyronia coleopterata (L.) differentiates into esophagus, filter chamber, midgut (conical segment, tubular midgut), and hindgut (ileum, rectum). The filter chamber is composed of the anterior extremity of the midgut, posterior extremity of the midgut, proximal Malpighian tubules, and proximal ileum; it is externally enveloped by a thin cellular sheath and thick muscle layers. The sac-like anterior extremity of the midgut is coiled around by the posterior extremity of the midgut and proximal Malpighian tubules. The tubular midgut is subdivided into an anterior tubular midgut, mid-midgut, posterior tubular midgut, and distal tubular midgut. Four Malpighian tubules run alongside the ileum, and each terminates in a rod closely attached to the rectum. Ultrastructurally, the esophagus is lined with a cuticle and enveloped by circular muscles; its cytoplasm contains virus-like fine granules of high electron-density. The anterior extremity of the midgut consists of two cellular types: (1) thin epithelia with well-developed and regularly arranged microvilli, and (2) large cuboidal cells with short and sparse microvilli. Cells of the posterior extremity of the midgut have regularly arranged microvilli and shallow basal infoldings devoid of mitochondria. Cells of the proximal Malpighian tubule possess concentric granules of different electron-density. The internal proximal ileum lined with a cuticle facing the lumen and contains secretory vesicles in its cytoplasm. Dense and long microvilli at the apical border of the conical segment cells are coated with abundant electron-dense fine granules. Cells of the anterior tubular midgut contain spherical secretory granules, oval secretory vesicles of different size, and autophagic vacuoles. Ferritin-like granules exist in the mid-midgut cells. The posterior tubular midgut consists of two cellular types: 1) cells with shallow and bulb-shaped basal infoldings containing numerous mitochondria, homocentric secretory granules, and fine electron-dense granules, and 2) cells with well-developed basal infoldings and regularly-arranged apical microvilli containing vesicles filled with fine granular materials. Cells of the distal tubular midgut are similar to those of the conical segment, but lack electron-dense fine granules coating the microvilli apex. Filamentous materials coat the microvilli of the conical segment, anterior and posterior extremities of the midgut, which are possibly the perimicrovillar membrane closely related to the nutrient absorption. The lumen of the hindgut is lined with a cuticle, beneath which are cells with poorly-developed infoldings possessing numerous mitochondria. Single-membraned or double-membraned microorganisms exist in the anterior and posterior extremities of the midgut, proximal Malpighian tubule and ileum; these are probably symbiotic.     

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.     

Ultrastructure of the digestive tract in Acarus siro (Acari: Acaridida)

The gut of the mite Acarus siro is characterized on the ultrastructural level. It consists of the foregut (pharynx, esophagus), midgut (ventriculus, caeca, colon, intercolon, postcolonic diverticula, postcolon), and hindgut (anal atrium). The gut wall is formed by a single-layered epithelium; only regenerative cells are located basally and these have no contact with the lumen. Eight cell types form the whole gut: (i) simple epithelial cells forming fore- and hindgut; (ii) cells that probably produce the peritrophic membrane; (iii) regenerative cells occurring in the ventriculus, caeca, colon, and intercolon; (iv) spherite cells and (v) digestive cells forming the ventriculus and caeca; (vi) colonic cells and (vii) intercolonic cells; and (viii) cells forming the walls of postcolonic diverticula and postcolon. Spherite and digestive cells change in structure during secretory cycles, which are described and discussed. The cycle of spherite, colonic, and intercolonic cells is terminated by apoptosis. Ingested food is packed into a food bolus surrounded by a single homogeneous peritrophic membrane formed by addition of lamellae that subsequently fuse together. The postcolonic diverticula serve as a shelter for filamentous bacteria, which also are abundant in the intercolon.     

香鱼消化道及肝脏的形态结构特征

采用解剖及石蜡切片显微技术观察了香鱼消化道及肝脏的组织学结构。香鱼消化道由口咽腔、食道、胃及肠构成。口咽腔大且狭长,其底壁前部有一对粘膜褶,两颌边缘着生宽扁梳状齿,腭骨及舌骨具齿,犁骨无齿;舌由基舌骨突出部分覆盖粘膜构成,舌粘膜上皮为复层扁平上皮,含有较多的杯状细胞和味蕾。食道、胃及肠均由粘膜层、粘膜下层、肌层及外膜构成。食道粘膜层上皮为复层扁平上皮,杯状细胞发达。胃呈V形,由贲门部、胃体部及幽门部组成,胃壁粘膜上皮为单层柱状上皮,贲门部与胃体部的固有层中有胃腺。肠较短,由前、中、后肠构成,肠壁粘膜上皮为单层柱状上皮,其游离面具微绒毛;上皮细胞间有杯状细胞。幽门盲囊有350～400条,其组织学结构与肠相同。肝脏单叶,外被浆膜;肝细胞形态不规则,肝小叶界限不明显。     

Peritrophic membrane structure and secretion in European corn borer larvae (Ostrinia nubilalis)

Peritrophic membrane (PM) secretion and formation occur primarily in the anterior region of the mesenteron in the European corn borer (Ostrinia nubilalis) as determined by light and electron microscopy. Nascent PM first became visible as fibrous linear chitin-containing structures stained with gold-labeled wheat germ agglutinin between and at the tips of the microvilli. No formed PM was visible at the foregut-midgut junction, but a thin single PM appeared first in the lumen between the stomodeal valves and the midgut epithelium. Just posterior to the stomodeal valves, multiple PMs were observed that became progressively thicker and more numerous in the mid and posterior regions of the mesenteron. The PM consists of an orthogonal chitin meshwork with openings slightly larger than the diameters of the microvilli. As it delaminates from the microvilli, the meshwork becomes embedded in proteinaceous matrix that greatly reduces the pore size of the PM.     

Peritrophic membrane structure and formation of larvalTrichoplusia niwith an investigation on the secretion patterns of a PM mucin

Peritrophic membrane or matrix (PM) secretion and formation patterns were examined in the cabbage looper larvae (Trichoplusia ni[Hubner]) by transmission and scanning electron microscopy (SEM). PM first became visible in the lumen between tips of the microvilli and the stomodeal valves as a single layered fibrous structure that became more compact in appearance in the middle and posterior mesenteron. In the anterior mesenteron, nascent PM was visible within the brush border as a fibrous linear structure that contained both the major PM matrix protein, invertebrate intestinal mucin (IIM) and chitin-containing structures. Even though delamination events were confined to the anterior mesenteron, IIM was secreted by columnar epithelial cells throughout the length of the mesenteron. SEM of the midgut epithelium revealed PM covering individual epithelial cells.     

The digestive system of the fish ectoparasite Dolops ranarum (Crustacea: Branchiura)

Reconstructions from serial sections reveal that the digestive system consists of a pharynx esophagus, crop, midgut, and rectum. Two main stems from the branched enteral diverticula are connected to the lateral regions of the crop by right rind left arms. Glandular tissue surrounds the enteral diverticula proximally. A strong sphincter separates the crop and midgut, whereas the midgut and rectum are separated by a weak sphincter. Cuboidal epithelium lines the pharynx, esophagus, crop, and rectum, whereas cuboidal and club-shaped epithelia line the midgut. The cuboidal cells possess elongated nuclei and numerous vacuoles, suggesting that absorption takes place in the midgut.     

Cytopathological effect of Bacillus thuringiensis israelensis endotoxins on the intestines of Aedes aegypti mosquito larvae

The dynamics of pathological changes in the intestine of Aedes aegypti larvae under the influence of toxins Cry11A and Cry4B produced by Bacillus thuringiensis israelensis was studied by means of electron microscope. Most significant ultrastructure changes in the intestine of the second instar larvae were observed in the midgut. The cytoplasm of cells disintegrated, and elongated lacunae appeared. The number of microvilli decreased, or they disappeared in the result of destruction. The peritrophic membrane displaced to the lumen of midgut. Any changes in epithelial cells and cuticle in time of foregut and hindgut were not observed in a comparison to control. The toxin Cry4B caused the most effective destruction of the midgut epithelium.     

The gut structure of Sinentomon erythanum yin (Protura : Sinentomidae)

The fine structure of the midgut, pyloric region, Malpighian papillae, and hindgut of Sinentomon erythranum (Protura : Sinentomidae) is described. Midgut cells are rich in mineral concretions and are presumably involved in excretory activity; the pyloric chamber, a cavity in the proturan intestine behind the midgut, is formed by cells with microvilli pointing anteriorly; the secretion from 6 Malpighian papillae flows into this cavity. The hindgut consists of 2 regions; the anterior of the 2 has a series of specializations typical of cells engaged in active water reabsorption. Long infoldings of the apical plasma membrane reach deep into the cells. The findings are compared with the gut organization of other genera of Protura examined to date.     

胡氏边白蚁消化系统的微细构造

胡氏边白蚁Marginitermes hubbardi(Banks)消化系统可分为前肠、中肠及后肠三大段.前肠包括葡萄状唾腺、口、咽喉、食道、前胃及贲门瓣;从贲门瓣开始到马氏管着生处为止这一段为中肠;后肠则分为葫芦形胃、结肠、直肠和肛门.其消化系统的特点:在前、后肠有几丁内膜、细胞层上还有一层微绒毛;上皮细胞底膜内陷很深,折叠中夹着许多线粒体;中肠围食膜表面有几丁层一直延伸到后肠;后肠前端膨大的葫芦胃中共生了很多种细菌及原生动物,共生的细菌、动物分泌纤维素酶帮助它消化木质纤维.     

Structural observations on the alimentary canal of Paranthessius anemoniae, a copepod associate of the snakelocks anemone Ammonia sulcata

Light and electron microscopy has shown the alimentary canal of Paranthessius to be composed of clearly defined foregut, midgut and hindgut regions. The spacious foregut is cuticle-lined and separated from the midgut by a valve. The midgut epithelium is composed of columnar cells with an apparent secretary/absorptive rôle, and amoeboid cells thought to engulf material from the lumen. The amoeboid cells have large electron-dense central vacuoles containing carbohydrate-and protein-staining material. These cells appear to be sloughed off into the lumen to form part of a faecal pellet. Apart from their digestive rôle the midgut cells store lipid and it is considered possible that they have an osmoregulatory function. The hindgut epithelium cell type, lacks a cuticular layer and is thought to be mainly concerned with absorption. The alimentary canal is surrounded by strands of longitudinal and circular muscle.     

黑水虻消化道形态及组织结构的观察

本文比较了不同发育阶段黑水虻Hermetia illucens消化道的形态学差异,掌握了幼虫消化系统的组织学特征。利用体视镜观察黑水虻5龄幼虫、预蛹及成虫的消化道形态,利用光学显微镜和扫描电镜观察幼虫消化道各段(前肠、中肠、后肠)的显微及超微结构。结果表明：黑水虻幼虫及预蛹的消化道均由前肠(食道和前胃)、中肠及后肠组成,从幼虫到成虫,消化道的长度不断缩短。与幼虫和预蛹相比,成虫消化道形态变化明显,前胃消失,出现了嗉囊及胃盲囊,中肠进一步缩短,后肠分化为回肠、结肠和直肠。组织学观察结果显示,幼虫的唾液腺开口于口腔,由膨大的管状腺体和腺管组成。食道由特化为角质刺突的内膜层及发达的肌层组成,其末端延伸至前胃。前胃膨大为球状,包括三层组织结构。根据上皮细胞形态的差异,中肠可分为四个区段。后肠薄,肠腔内褶丰富,肠壁可见数量较多的杆状细菌。马氏管开口于中、后肠交界处,包括4支盲管,管内壁密布微绒毛。黑水虻消化道形态随发育阶段的变化,反映了各阶段摄食及消化生理的差异。幼虫消化道各段具有各自典型的组织学特征,其前、中、后肠可能分别承担了食物接纳与初步消化、消化与吸收以及重吸收功能。本研究结果为进一步了...     

The intestinal musculature of Derocheilocaris typica (Crustacea,Mystacocarida) – A different and unique pattern

An ultrastructural study of the intestine of Derocheilocaris typica revealed an organization of the midgut musculature, which is unique in the Crustacea. This species unusual anal skeletomusculature has also not been seen before.The intestinal musculature of D. typica displays different patterns in the fore-, mid-, and hindgut. Around the foregut, eight pairs of dilator muscles complement a contiguous carpet of circular muscles around the foregut. Their coordinated action serves to suck in food and pass it to the midgut. A pair of large glands, each consisting of three cells, opens into the foregut above the mouth. The midgut musculature differs from any previously described. Circular muscles give rise to thin, longitudinal protrusions and short longitudinal muscles. The distribution of all of them is irregular. Thus the short longitudinal muscles, which have a length of approximately one segment, vary from none to five within a segment. The last abdominal segment is exceptional, by having 15–20 short longitudinal muscles. The hindgut has three longitudinal muscle groups each consisting of three muscles, one dorsally and one on each side. The posterior end of the midgut and the hindgut suggests that they act together to achieve defecation. The importance of the peri-intestinal cells as part of the nutritional process is emphasized.