Dehydration-induced cross tolerance of Belgica antarctica larvae to cold and heat is facilitated by trehalose accumulation

Larvae of the Antarctic midge, Belgica antarctica (Diptera: Chironomidae), are frequently exposed to dehydrating conditions on the Antarctic Peninsula. In this study, we examined how rates and levels of dehydration alter heat and cold tolerance and how these relate to levels of trehalose within the insect. When dehydrated, larvae tolerated cold and heat stress more effectively, although resistance to cold was more pronounced than heat resistance. Slow dehydration was more effective than rapid dehydration in increasing temperature tolerance. Severe dehydration (50% reduction in water content) caused a much greater increase in temperature tolerance than did mild dehydration (e.g. 10% water loss). Larvae severely dehydrated at a slow rate (98% RH) were more temperature tolerant than those dehydrated quickly (0 or 75% RH). These results indicate that the slower dehydration rate allows the larvae to more effectively respond to reduced water levels and that physiological adjustments to desiccation provide cross tolerance to cold and heat. Levels of trehalose increased during dehydration and are likely a major factor increasing subsequent cold and heat resistance. This hypothesis was also supported by experimental results showing that injection of trehalose enhanced resistance to temperature stress and dehydration. We conclude that changes in temperature tolerance in B. antarctica are linked to the rate and severity of dehydration and that trehalose elevation is a probable mechanism enhancing this form of cross tolerance.     

The association of serotonin with the alimentary canal of the African migratory locust, Locusta migratoria: distribution, physiology and pharmacological profile

The association of serotonin with the alimentary canal of Locusta migratoria was investigated using immunohistochemistry and high performance liquid chromatography (HPLC) coupled to electrochemical detection. Serotonin-like immunoreactive processes were differentially distributed between and within three regions of the alimentary canal; the foregut, midgut and hindgut. The midgut possessed the most serotonin-like immunoreactive processes, while the hindgut contained only a few immunoreactive processes. Using HPLC coupled to electrochemical detection the serotonin content was highest in the midgut followed by the foregut and hindgut. The physiological response of the midgut to serotonin as well as to the combination of serotonin and proctolin was also examined. It was found that the application of serotonin to the midgut leads to a dose-dependent reduction in tonus of the circular muscles. Serotonin was also able to inhibit a proctolin-induced contraction of the midgut in a dose-dependent manner. The physiological and pharmacological properties of serotonin agonists and antagonists on the midgut were also investigated. The results indicate that alpha-methyl 5-HT was the most effective agonist leading to a 108% relaxation at 10(-9) M compared to that caused by the same serotonin concentration. Among several serotonin receptor antagonists tested, mianserin was the most potent. The application of mianserin at 10(-5) M in combination with 5x10(-6) M serotonin resulted in a 66% reduction of the serotonin-induced relaxation of midgut muscle. The serotonin antagonist cyproheptadine was less effective leading to a 39% reduction of the 5x10(-6) M serotonin-induced relaxation. Ketanserin was a weak antagonist.     

Observations on the relationship between the Antarctic coastal diatoms Thalassiosira antarctica Comber and Porosira glacialis (Grunow) Jørgensen and sea ice concentrations during the late Quaternary

The available ecological and palaeoecological information for two sea ice-related marine diatoms (Bacillariophyceae), Thalassiosira antarctica Comber and Porosira glacialis (Grunow) Jørgensen, suggests that these two species have similar sea surface temperature (SST), sea surface salinity (SSS) and sea ice proximity preferences. From phytoplankton observations, both are described as summer or autumn bloom species, commonly found in low SST waters associated with sea ice, although rarely within the ice. Both species form resting spores (RS) as irradiance decreases, SST falls and SSS increases in response to freezing ice in autumn. Recent work analysing late Quaternary seasonally laminated diatom ooze from coastal Antarctic sites has revealed that sub-laminae dominated either by T. antarctica RS, or by P. glacialis RS, are nearly always deposited as the last sediment increment of the year, interpreted as representing autumn flux. In this study, we focus on sites from the East Antarctic margin and show that there is a spatial and temporal separation in whether T. antarctica RS or P. glacialis RS form the autumnal sub-laminae. For instance, in deglacial sediments from the Mertz Ninnis Trough (George V Coast) P. glacialis RS form the sub-laminae whereas in similar age sediments from Iceberg Alley (Mac.Robertson Shelf) T. antarctica RS dominate the autumn sub-lamina. In the Dumont d'Urville Trough (Adélie Land), mid-Holocene (Hypsithermal warm period) autumnal sub-laminae are dominated by T. antarctica RS whereas late Holocene (Neoglacial cool period) sub-laminae are dominated by P. glacialis RS. These observations from late Quaternary seasonally laminated sediments would appear to indicate that P. glacialis prefers slightly cooler ocean–climate conditions than T. antarctica. We test this relationship against two down-core Holocene quantitative diatom abundance records from Dumont d'Urville Trough and Svenner Channel (Princess Elizabeth Land) and compare the results with SST and sea ice concentration results of an Antarctic and Southern Ocean Holocene climate simulation that used a coupled atmosphere–sea ice–vegation model forced with orbital parameters and greenhouse gas concentrations. We find that abundance of P. glacialis RS is favoured by higher winter and spring sea ice concentrations and that a climatically-sensitive threshold exists between the abundance of P. glacialis RS and T. antarctica RS in the sediments. An increase to > 0.1 for the ratio of P. glacialis RS:T. antarctica RS indicates a change to increased winter sea ice concentration (to >80% concentration), cooler spring seasons with increased sea ice, slightly warmer autumn seasons with less sea ice and a change from ~ 7.5 months annual sea ice cover at a site to much greater than 7.5 months. In the East Antarctic sediment record, an increase in the ratio from <0.1 to above 0.1 occurs at the transition from the warmer Hypsithermal climate into the cooler Neoglacial climate (~ 4 cal kyr) indicating that the ratio between these two diatoms has the potential to be used as a semi-quantitative climate proxy.     

紫胫长夹蝗消化道的形态学观察

本文通过扫描仪对紫胫长夹蝗Choroedocus violaceipes Miller消化道内外壁进行了扫描.观察到消化道各部位的形态特征:食道直管状,由多列纵行脊组成;嗉囊由V形区、V形脊、柳叶脊、扇形脊和不规则脊组成;前胃杯形,由多列纵行脊组成;贲门是由6个凸出于肠壁的Y形结构环围而成;中肠膜质,约占消化道长度的2...     

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.     

光滑足距小蠹消化道的解剖结构

采用体视显微和扫描电镜技术研究光滑足距小蠹Xylosandrus germanus(Blandford)消化道的解剖结构。结果表明,光滑足距小蠹消化道由前肠、中肠和后肠三部分组成。成虫前胃由8个骨化的前胃板组成,呈灯笼状结构。前胃板由板状部和片状部组成,板状部短而简单,片状部甚长,由斜面、咀嚼刷和关闭刚毛组成。胃盲囊着生在中肠近后端,有细管状和囊状2种,成虫分别有1对,幼虫有1对细管状和3~5对囊状。6根马氏管分成2组,1组4根,另一组2根。6根马氏管与后肠肠壁形成隐肾系统。消化道具有1对囊状和1对细管状的胃盲囊可作为光滑足距小蠹成虫的识别特征。     

黄脸油葫芦消化道和马氏管的组织学观察

应用石蜡切片技术对黄脸油葫芦Teleogryllus emma(Ohmachi and Matsumura)成虫消化道和马氏管的显微结构进行观察。消化道由前肠、中肠和后肠3部分组成:前肠由内向外可分为6层:内膜、肠壁细胞层、底膜、纵肌、环肌和围膜;中肠组织结构也分为6层,即由内向外依次为围食膜、肠壁细胞层、底膜、环肌、纵肌和围膜;后肠的组织结构与前肠基本相似,但内膜比前肠的薄,且肌肉的排列较前肠不规则,与中肠的肌肉排列相似,即环肌在内,纵肌在外。消化道各部位的结构差异与功能有密切关系。马氏管管壁由8个左右形状多变并具有显著细胞核的大形的单层上皮细胞组成。     

Anatomy and histology of the alimentary canal of the black beetle,Heteronychus arator

Abstract

The gut anatomy of adult and third- instar larval black beetle is described, illustrated, and discussed in relation to the condition reported for other scarabs.     

Ultrastructure of the larval midgut of Bittacus planus (Mecoptera: Bittacidae) and Neopanorpa longiprocessa (Mecoptera: Panorpidae)

Bittacidae and Panorpidae are the two largest families in Mecoptera. The larvae of Bittacidae are different from those of Panorpidae in external morphology and habits, and have an interesting habit of spraying the body surface with soil through the anus. However, it remains unknown to date whether the larval midguts are different in structure between the two families. Here the ultrastructure of the larval midguts of the hangingfly Bittacus planus Cheng and the scorpionfly Neopanorpa longiprocessa Hua & Chou were compared using light, scanning, and transmission electron microscopy. The midguts of both species are simple tubes of single layered epithelia with digestive and regenerative cells but without diverticula. The basal plasma membrane of epithelial cells exhibits infolding in B. planus, but is closely apposed to its basal lamina in N. longiprocessa. Lymph spaces are present between adjacent epithelial cells in B. planus, but are absent in N. longiprocessa. The regenerative cells are scattered among the digestive cells in B. planus, but are aggregated in N. longiprocessa. The longitudinal muscle bands are compact in B. planus, but are sparse in N. longiprocessa. The compact longitudinal muscle bands are likely associated with their soil-spraying habit in Bittacidae.     

Calcitonin-like immunochemical staining in the alimentary tract of Ciona intestinalis L.

Summary Calcitonin-like immunoreactivity has been found with the peroxidase-anti-peroxidase (PAP) method in cells of the epithelium of the alimentary tract as well as in nerve cells and nerve fibers in the connective tissue underlying the epithelium of the alimentary tract of Ciona intestinalis L. The nature of these cells is discussed with reference to endocrine-like cells found in the alimentary tract of other protochordates and to the possible dual role of calcitonin occurring in the gastroenteropancreatic system, on the one hand, and in the nervous system, on the other.     

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.     

Immnunohistochemical detection of phthalate esters in the alimentary canal of Tilapia spp.

An examination of the occurrence and distribution of phthalate esters in the alimentary canal of a polyhybrid of Tilapia gave evidence of different and selective patterns of distribution in the organ tissues: the phthalate esters were shown to be concentrated in the stomach and anterior intestine. The restricted distribution of phthalate esters can have implications for the physiology of the digestive system. The phthalates, stored in the oxyntic cells of the gastric tubular glands, probably interfere with the digestive process. The strategic location of the enterocytes in the anterior intestine implies that they can hamper the reabsorption of digestion products. The endocrine disrupting effects known for these chemicals are probably related to the absorption of them via the alimentary canal.     

The functional morphology of the alimentary canal of larval stages of the parasitic copepod Lepeophtheirus salmonis

The functional morphology of the alimentary canal of copepodite and chalimus stages of Lepeophtheirus salmonis (Krøyer, 1837) is described and compared with that found in other copepods studied to date.
The buccal cavity passes into a gut comprising three major regions: foregut (oesophagus), midgut and hindgut. The foregut and hindgut both posscss a cuticular lining whereas the midgut is lined with specialized epithelial cells. The midgut is divided into three recognizable zones, namely anterior midgut caecum, anterior midgut and posterior midgut. Three main types of epithelial cell are recognizable in the midgut: vesicular cells, microvillous cells and basal cells which correspond to the cell types normally described in other parasitic and free-living copepod species.
Digestion is thought to occur in the midgut and be mediated by the epithelial cells that line it. Although several glands appear to discharge into the area of the buccal cavity, none was seen to interface to any other area of the gut. There was no evidence for the involvement of commensal gut bacteria in food digestion.     

Histology and carbohydrate histochemistry of the alimentary canal in the rainbow trout Oncorhynchus mykiss

A histological and histochemical analyses were carried out on the entire alimentary canal of the rainbow trout Oncorhynchus mykiss . In particular the oesophageal region showed presence of terminal β‐D‐galactose(1–3)‐N‐acetylgalactosamine and α‐N‐acetylgalactosamine. In the anterior and posterior regions of the stomach, lining epithelium and gastric pits exhibited the presence of β‐gal and α‐GalNAc. In addition sialoglycoconjugates having sialic acid–β–galactose(1–3)‐N‐acetylgalactosamine and sialic acid‐N‐acetylgalactosamine as terminal tri‐ and di‐saccharides, were demonstrated. In proximal and distal intestine goblet cells showed the presence of sialoglyconjugates, having sialic acid‐β‐gal(1–3)‐GalNAc and sialic acid‐GalNAc as terminal sequences, belonging to N‐linked chains. In the enterocytes of the entire intestine, terminal GlcNAc, α‐Gal, α‐fucose were found.     

A histochemical study of pollen digestion in the alimentary canal of honeybees (Apis mellifera L.)

Histochemical staining of embedded sections of the alimentary canal of honeybees indicated that carboxylated polysaccharides could be efficiently digested and absorbed, except when sequestered within unswollen and unbroken pollen grains that appeared to be impervious to enzymes of the gut. Hemicelluloses and pectic acids of the pollen wall structure underwent partial digestion, but pollen wall cellulose and sporopollenin were not digested. A separation of pollen walls from colloidal semisolids of the pollenkitt and disgorged protoplasm was apparent. The layers of slurry created by this separation remained into the rectum, and consisted primarily of saturated organic compounds which do not stain with weakly basophilic or acidophilic dyes.     

中华稻蝗全消化道内壁显微结构观察

本文采用扫描仪和扫描电镜对中华稻蝗消化道内壁的细微结构进行了系统观察和研究。结果表明,中华稻蝗食道内壁由纵行脊组成,前端有齿。嗉囊包括两段,前段的一个小的膨大部分,由V-形区和两侧的V-形脊组成,只在前端内壁有齿;后段为一个大的膨大部分,由柳叶脊、扇形脊和不规则脊组成,脊的上缘有齿。前肠内壁的齿主要为单生齿,除贲门瓣上齿的齿尖指向前方外,全部齿的齿尖指向后方。后肠的前端为12个幽门瓣,内壁有齿。回肠和结肠由6条纵行脊组成,结肠内壁有齿。直肠的齿在除直肠垫外的直肠内壁上。后肠的齿主要为丛生齿,后肠除直肠内壁齿的齿尖指向附着环外,全部齿的齿尖指向后方。根据我们的观察,对前肠提出了新的分区。     

Purification and characterization of thermo-labile alkaline phosphatase from an Antarctic psychrotolerant Bacillus sp. P9

A psychrotolerant Bacillus sp. from Antarctica produced an alkaline phosphatase in the culture supernatant. The strain showed 98.4% 16s rDNA sequence identity with Bacillus sphaericus. The 76 kDa protein was purified 11.1-fold showing alkaline phosphomonoesterase activity. Enzyme was optimally produced at 25 °C and pH 7.0. This cold active alkaline phosphatase is heat labile and gets completely inactivated at 60 °C in 50 min and is active in broad pH range.     

太白蝎蛉消化道形态学与组织学研究

利用光学显微镜和扫描电子显微镜, 在形态学和组织学水平上研究了太白蝎蛉Panorpa obtusa Cheng成虫消化道的结构。结果表明： 蝎蛉消化道由前肠、中肠、和后肠组成。前肠包括咽喉、食道、和前胃, 但没有嗉囊,其中咽喉可分为骨化的前咽和附着扩肌的后咽（咽喉唧筒）; 前胃壁很厚,内膜上长有许多排列整齐、紧密的棕色胃刺,司过滤、暂时储存和磨碎食物的功能; 前肠末端有6个贲门瓣伸入中肠。中肠较长且膨大,其肠壁细胞由柱状细胞和再生细胞组成; 肠壁细胞外分别为环肌和纵肌,无胃盲囊,也未观察到围食膜。6根棕红色的马氏管位于中、 后肠分界处。后肠分为不对称的“V”字型回肠、环状结肠、以及膨大透明的直肠, 直肠内壁上有6个交替排列的直肠垫。最后简要讨论了蝎蛉消化道的结构与功能,及其在蝎蛉科昆虫分类中的意义。