The Gastrointestinal Tract Morphology And Function Of Pelteobagrus Fulvidraco And Eriocheir Sinensis As Well As Its Response To Feeding And Feed

The gastrointestinal tract is the vital organs for digestion and absorption as well asdefense. Normal structure and function of the gastrointestinal tract is very important tothe growth and development of economic aquatic animals. Pelteobagrus fulvidraco andEriocheir sinensis are farmed species developed rapidly in recent years. However, noliterature reporting on gastrointestinal tract morphology and its response to feeding andfeed of both aquatic animals was found. The experiment first observed gastrointestinalstructure under light microscope and characteristics of epithelial ultrastructure ofPelteobagrus fulvidraco and Eriocheir sinensis. On this basis, we studied on the effectsof starvation and refeeding on gastrointestinal tract morphology and function. Finally,we investigated the intestinal morphology response to different levels of soybean meal,peanut meal, rapeseed meal and cottonseed meal to provide a theoretical basis for theimprovement of two animal feeding and feed formulation.Test1: we selected Pelteobagrus fulvidraco whose average body weight was46gand Eriocheir sinensis whose average body weight was46g as experimental subjects,then quickly killed and dissected. Using light microscopy, scanning electron microscopyand transmission electron microscopy to study the histological structure of theirgastrointestinal tract, the results showed that gastrointestinal tract of Pelteobagrusfulvidraco can be divided into the mucosa, submucosa, muscularis and serosa all thisfour-storey structure from the inside out. Clusters of gastric mucosal folds were seenand gastric pits were intensive. No goblet cells were found and gastric glands arrangedcomplexly. Intestinal tract was divided into foregut, midgut and hindgut. Mucosalepithelium consists of absorptive cells and goblet cells, moreover, the submucosa wasunderdeveloped. The number of folds gradually reduced from foregut to hindgut while the thickness of muscular layer was gradually thinning and the number of goblet cellsgradually become more。There are secondary folds on the gastric mucosal folds in theelectron microscope, and abundant organelles were observed in the cytoplasm ofepithelial cells. The jagged folds structure gradually slowed down to a tiny wavy fromforegut to hindgut. Each segment of the gastrointestinal tract have microvilli covered.The organelle of foregut was the richest while midgut and hindgut was riched inlysosome. Goblet cells depressed as secretion hole. Secretion holes in foregut andmidgut were surrounded by a sheet-like secretions while in hindgut secretions appear asgranule.The surface of gastric epithelial cell in Eriocheir Sinensis covered with chitin layerand the connective tissue was loose. Moreover, gastric glands were found and themuscular layer was complex. Intestinal tract can be divided into midgut, intestinal balland hindgut. The folds of the midgut parallelled on both sides and the edges weresmooth. The free surface of cells have striated border without chitin coverage. Thelamina propria and submucosa were not obvious. Intestinal ball had the transitionalmorphological festures of midgut to hindgut and outer membrane formed like sphere.The hindgut folds were covered with chitin and no goblet cells were investigated. Underthe electron microscope, the organelles of gastric epithelial were few. The surface of cellhave microvilli and secretions covered, moreover, cilia gathered into bundles. Themidgut folds structured as stripe whose organelles were the most abundant. Intestinalball had not so many folds and the hindgut folds were like coarse strips which had ciliaon surface and a large number of secretory granules contained in cytoplasm.Test2: We analysed the effect of short-term starvation and refeeding ongastrointestinal morphology and physiological function of Pelteobagrus fulvidracowhose average body mass was42g and Eriocheir sinensis whose average body masswas48g.Under the control of experimental animals in satiation level, sample respectively at1,3,7d after starvation treatments and refeeding1,3,7d. The results showed that internalorgans and hepatopancreas index Pelteobagrus fulvidraco were significantly less thanthe control group and continued to decrease during starvation, while after refeeding, they can restore in a relatively short period of time. Starvation made the stomach ACPactivity significantly weakened and SOD activity was significantly higher than that ofthe control. The foregut SOD significantly reduced; the midgut ACP significantlyenhanced, T-AOC continues to decrease; the hindgut ACP activity significantlyenhanced.7days after feeding, immunity can restore to normal or beyond the controllevel. During starvation pepsin in stomach significantly reduced, lipase in the foregutincreased significantly after hunger7d, the intestinal lipase was significantly greaterthan that of the control group after3d of starvation. Activities of digestive enzymereturned to normal after refeeding. During starvation, gastric glands cells graduallydisappeared, the apical surface of epithelial cells were damaged, organizational structurewas shrinking and finally folds completely broken. The intestinal mucosa decreases inheight and the amount reduced, former midgut epithelial microvilli lack of a large area,epithelial cell organelles reduced, the sharp increase in the number of lymphocytes inthe lamina propria, submucosa and muscularis both thickening. After refeeding, themidgut and hindgut recovered the fastest while stomach and foregut relatively slow, butthe structure was basically returned to control levels.The stomach SOD activity of Eriocheir sinensis was significantly reduced instarvation situation, while the ACP, AKP, SOD activity was significantly enhanced ingut. After refeeding, part of the immune function in each tissues were still significantlylower than that in the normal state. During starvation, gastrointestinal amylase activitiesin Eriocheir sinensis were declining, which were still significantly lower than thenormal level after refeeding7days. In morphological structure, after starvation,epithelial cells in gastric mucous membrane gradually integrated, cytoplasmic wasdamaged, the nuclear was missing and mucosal folds fused finally, the intestinal plicacontinued integrating, microvilli slowly shrinked until large area of missed; epithelialcells in hindgut gradually become vacuolization and homogeneously with theconnective tissue, surface of cavity cilia become short. In addition, the organelles in theintestinal epithelial cells reduced and the mitochondria were swelled, cristae wereruptured, nucleus was apoptosis and still did not return to normal state after7daysfeeding. The expression of the chitin synthesis enzyme and the peritrophic factors in the liver was significantly down-regulated in starvation period, while the expression inmidgut had a significant increase. Refeeding caused expression of the two genes in liverand midgut higher than normal levels.Test3: We used fish meal as control making a research in the intestine morphologychanges of Pelteobagrus fulvidraco and Eriocheir sinensis whose feed were respectivelyappended25%and50%soybean meal, peanut meal, rapeseed meal and cottonseed mealthese four kinds of vegetable proteins. Fish and crab initial body weight was about23gand8g, keeping feeding eight weeks. Compared with control group, plant protein levelof25%, intestinal morphology of Pelteobagrus fulvidraco did not change significantlyin soybean meal group. In the peanut meal group, boundaries between intestinalepithelial cells were not clear and the submucosa had a bit of thickening, but noinfiltration of lymphocytes. Height of the intestinal mucosal were significantlydecreased in rapeseed meal group and cottonseed meal group, and in cottonseed mealgroup the submucosa thickened, intraepithelial lymphocyte infiltrated while muscularlayer significantly thinning. When the level of addition reached50%, the midgutstructure produced a significant change in each test group Pelteobagrus fulvidraco. Atthe point of protein efficiency, group of50%soybean meal and cottonseed meal had nosignificant difference with the control group, but group of50%peanut meal andrapeseed meal had significantly difference with the control group.Compare with the control group, after feeding the plant protein levels in25%3weeks, intestinal epithelial cells of Eriocheir sinensis was mistiness and nucleusappeared partially missing in soybean meal group. Nucleus of cottonseed meal groupand peanut meal group appeared slightly vacuolization and arranged slightly messywhile connective tissue had many voids. The entire mucosal epithelium was loose andserious injuried in rapeseed meal group. After8weeks, pathological situations ofvarious groups have worsened, chitin layer have some shrinkage in soybean meal group.Cottonseed meal group showed part of the incomplete epithelia, the existent epitheliumgradually form homogeneous; in peanut meal group, all epithelial cell were vacuolated,connective tissue was in homogenization. When the addition level reached50%,hindgut structure generated significant change in each group after fed at3weeks. The above results showed that gastrointestinal tract morphology of Pelteobagrusfulvidraco and Eriocheir sinensis showed suitable with the feeding habits. Pelteobagrusfulvidraco of42g and Eriocheir sinensis of48g can tolerate7d starvation andPelteobagrus fulvidraco can return to normal after feeding7d, but Eriocheir sinensisneeded a longer period of time. Intestine of Pelteobagrus fulvidraco and Eriocheirsinensis were very sensitive to the type of plant protein and quantity of addition infeedstuff. When selecting the four kinds of plant protein, security addition of peanutmeal, cottonseed meal, rapeseed meal should be below25%, soybean meal should beless than50%and suitable addition remained to be depth investigation.