宽体金线蛭消化道的组织学观察

运用解剖学和组织学方法对宽体金线蛭消化道的结构进行了组织学研究。结果表明,宽体金线蛭的嗉囊向两侧伸出11对侧盲囊,第6对侧盲囊狭长并延伸到直肠两侧;咽主要由黏膜层、肌层和外膜构成,外膜几乎不可见;食道、嗉囊、肠和直肠管壁由黏膜层、黏膜下层、肌层和浆膜构成;咽和直肠的上皮具纹状缘。除肠外,其他消化道的上皮细胞均无发达的纤毛,且黏膜上皮皆为单层柱状上皮;除肠和直肠外,腺体及导管较少;直肠的黏膜肌层为内环外纵两层,其他各部均为纵行肌一层;消化道各部黏膜下层较发达;外膜为浆膜,与黏膜下层分界不明显。     

A comparative analysis of the feeding apparatus in pomacanthids, with special emphasis of oesophageal papillae in Genicanthus personatus

Of the pomacanthids examined in the present study (22 species; seven genera), only Genicanthus (eight species) had unique oesophageal papillae. The papillae of the masked angelfish, Genicanthus personatus are arranged in a radial fashion, finger-like or polypoid in shape, very abundant, fill the lumen, and vary considerably in length (0·38–2.40 mm) and width (0·12–1·18 mm). The surface pores (2.8–45.2 μm in diameter) of each papilla are part of the gastric or mucus-secreting oesophageal glands as determined by histological examination. Preliminary stomach content analyses revealed that G personatus consumes a variety of animal and plant material, including algae, copepods, diatoms, and eggs, but dominated in volume by plant material. The oesophageal papillae may constitute a morphological specialization of the digestive tract at the genus level. This may enable Genicanthus spp. to utilize and process a food source not readily available to other pomacanthid species. Additional studies are necessary to determine other ecological, behavioural, social, and morphological variables that separate this large and diverse group of fishes ecologically.     

美洲黑石斑鱼消化道的形态结构

采用解剖和光镜技术观察了美洲黑石斑鱼消化道的形态及组织学结构。消化道由口咽腔、食道、胃、肠构成。口咽腔较大,具颌齿、腭齿及犁齿;舌由基舌骨突出部分覆盖粘膜构成。食道、胃及肠均由粘膜层、粘膜下层、肌层及外膜构成。食道粘膜层绒毛分柱状上皮区及扁平上皮区,扁平上皮区表面为杯状细胞层;食道粘膜下层中有食道腺。胃呈V形,由贲门部、胃体部及幽门部组成,胃壁粘膜层上皮为单层柱状上皮,胃腺位于贲门部与胃体部的固有层中。肠细长,呈S型,由前、中、后肠构成,粘膜层向肠腔突起形成肠绒毛,粘膜上皮为单层柱状上皮,上皮游离面有微绒毛密集排列而成的纹状缘,上皮中含有杯状细胞,且杯状细胞的数量从前向后呈递减趋势;肠长/体长约为1.6。胃与小肠相接处有3对指状幽门盲囊,幽门盲囊的组织学结构与肠相同。     

池养大口胭脂鱼鱼种的食性

池养大口胭脂鱼鱼种的食性研究表明 ,大口胭脂鱼鱼种为浮游动物尺寸选择性鱼类 ,其选食行为主要受鱼体及水体中浮游动物的个体大小影响 ,与浮游动物的种类、逃跑能力、运动方式等关系不明显。并初步探讨了 3种浮游生物食性鱼类 (大口胭脂鱼、鲢、鳙 )的食物关系。     

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。     

Influence of method of whole-wheat feeding on the performance,digestive tract development and carcass traits of broiler chickens

The present study was conducted to investigate the effects of feeding whole wheat either through a mixed feeding (MF) or free choice feeding (FCF) system on the performance, digestive tract development and carcass traits of broiler chickens. The following three treatments, based on wheat and soybean meal, were employed: GW, ground-wheat diet with 600–690 g wheat kg⁻¹; MF, GW diet with 490–500 g wheat kg⁻¹ and 100–200 g whole wheat kg⁻¹; and FCF, whole wheat and a protein concentrate offered in separate feeders. Each diet was fed to six pens of 36 birds each from day 7 to 35 post-hatch. Over the 7–35-day trial period, no differences (P>0.05) were observed between the weight gain, feed intake and feed per gain of broilers receiving the GW and MF treatments. Birds receiving the FCF treatment had the lowest (P<0.05) weight gain and feed intake, and the highest (P<0.05) feed per gain. During week 1 of the trial, the protein concentrate was consumed more than the whole wheat (0.69 vs. 0.31) in the FCF treatment, resulting in the amount of concentrate offered being restricted during subsequent weeks. Over the trial period, the average consumption of protein concentrate remained high (0.56 of the total intake). Both whole-wheat treatments increased (P<0.05) the relative gizzard weights. Factors that affect diet selection such as learning and previous experience, visual differences between the foods, texture and flavour of the food, and palatability may explain the lower whole-wheat intake in the FCF treatment. In this study, whole wheat was introduced only on day 7 and it is possible that the birds may have to be trained to experience choice feeding from the first week of life. However, the present results suggest that FCF may not be an appropriate feeding system for fast growing modern broilers.     

A multivariate approach to the feeding habits of small fishes in the Guadalquivir Estuary

In the analysis of the feeding habits of the 11 most abundant fish species in the Guadalquivir Estuary, collected monthly (February 1998 to January 1999) at two different sampling sites, a total of 46 prey taxa were identified. Classifications (based on Bray–Curtis similarities derived from occurrence, number and mass data) of the different fish categories (postlarvae and juvenile–adults of each species) revealed two main trophic guilds, whose preferential prey (SIMPER analysis) were mysids and copepods, respectively. The similarity matrices derived from occurrence, number and mass data were always significantly correlated (RELATE: r >0.636; P <0.01), indicating that a good agreement in feeding patterns emerged from these variables. The seasonal coincidence of maximal fish and key-prey species densities suggests that food availability may be a principal factor influencing the nursery function of the Guadalquivir Estuary.     

Activities of digestive enzymes in rats kept on standard or excessive breast feeding and on low-protein diet at once after weaning

Activities of digestive enzymes (maltase, alkaline phosphatase, aminopeptidase M, and glycyl-L-leucine dipeptidase) in small and large intestine, liver, and kidney were studied in rats of different ages kept at the period of lactation under conditions of the standard (8 individuals per litter) and low (3 individuals) number of pups per litter. The low-protein diet for 10 days at once after weaning was found to change the mass of organs and their digestive enzyme activities in all studied rat groups. The revealed changes were more prominent in rats kept under conditions of excessive breast feeding. In adult animals of this group, distribution of the alkaline phosphatase activity along the small intestine differed from that in control rats. The obtained results seem to confirm that any disturbance of the nutrition quality in early ontogenesis leads to disturbance of the «metabolic programming of enzyme systems» of digestive organs.     

Food and feeding habits of four species of juvenile mullet (Mugilidae) in a tidal lagoon in Ghana

Juvenile mugilid fishes, Liza falcipinnis, L. dumerilii, Mugil bananensis and M. curema , which enter the Elmina Lagoon in the Cape Coast District of Ghana, have a similar diet comprising mainly bacteria, diatoms, blue-green/green algae, protozoans, detritus and particulate organic matter. No seasonal changes in the diet and feeding activity were observed. The relative gut length (intestine to standard length ratio) and diet showed no significant changes with size of fish in all the species. All four species were diurnal feeders, but their peak feeding times differed. Interspecific competition for food was possibly limited by species preferences for substrate particles of particular size range and differences in feeding chronology.     

Distribution and localization of the digestive laminarinases in animals

The presence of laminarinases in the digestive system of a number of invertebrate and vertebrate species has been investigated. The enzymes were detected in coelenterates, annelids, sipunculids, bryozoans, molluscs, arthropods (crustaceans and insects), echinoderms, tunicates and fishes. Since it could be demonstrated that, in fishes, at least, laminarinases are secreted by the intestinal mucosa rather than by associated gut bacteria, an attempt was made to correlate the distribution of these digestive enzymes with the feeding habits of the animals. The correlation is particularly evident among fishes where in the genus Leuciscus carnivores lack laminarinases in contrast to omnivores. From an evolutionary point of view, we can postulate that the possession of laminarinases is ancient in Metazoa and has been either kept or lost by more evolved taxa depending on their feeding specialization, as has already been demonstrated for chitinases and cellulases.     

The digestive tract of the amberjack Seriola dumerili, Risso: a light and scanning electron microscope study

The histology of the digestive tract of the amberjack ( Seriola dumerili , Risso) was studied using light and scanning electron microscopy. The anterior oesophagus mucosa displays primary and secondary folds lined with a stratified squamous epithelium with fingerprint-like microridges which is substituted, on the top of the oesogaster folds, by a simple columnar epithelium with short microvilli. Only primary folds are present in the stomach. The anterior portion is rich in simple tubular glands, whereas the oesogaster and the pyloric region are devoid of them. Pyloric caeca and anterior and middle intestine mucosa display the same pattern of folding. The dominant cell type is the enterocyte, which exhibits larger and thinner microvilli in the caeca than in the intestine. The columnar epithelium of the rectum is replaced, in the anal sphincter, by a stratified flattened epithelium. Goblet cells are numerous throughout the whole length of the tract with the exception of the initial part of the oesophagus, the oesogaster, the stomach and the anal sphincter. Mucosubstances have been shown to vary in the different regions of the gut: acid mucines are found in the oesophagus, pyloric stomach, caeca, intestine and rectum, whereas neutral mucosubstances dominate in the anterior portion of the stomach. The muscularis is well developed throughout the length of the tract: two layers of striated muscle at the oesophageal level; two layers of smooth muscle in the stomach wall and three at the intestinal level.     

The feeding relationships of the larger fish species in a Scottish sea loch

Patterns within a fish assemblage have been examined from catches obtained over a period of 17 months using fixed nets and rod and line sampling. A total of 19 species were caught with summer samples dominated by dab and saithe and winter samples by whiting. Cod were caught regularly throughout the year. Catches at the study site of dab and whiting occurred mainly at night but for cod and saithe catches occurred throughout the day. There was no indication ofa crepuscular or tidal rhythm for any species. Differences between our own observations and those from other published studies lead us to conclude that no species-specific generalizations about feeding periodicities can be made. Feeding patterns are more likely to be determined by site-specific features of particular habitats and their associated prey and predator assemblages.
Examination of stomach contents data using a variety of methods indicates that conclusions are highly dependent on the form of the resource matrix used. However, our analyses indicate that during summer cod and dab feed on a much narrower range of prey than saithe and that there is significant overlap in their diets if a resource matrix based on percentage occurrence of prey species is used. Nevertheless, most diet overlap values for the species examined were low (between 0.1 and 0.2) suggesting that competition for food is unlikely. To date, no experiments have been performed to test the hypothesis that cod and dab compete for food.     

An ultrastructural approach to feeding behaviour in Philodina roseola and Brachionus calyciflorus (rotifers) II. The oesophagus

The cuticular oesophagus is a simple expansion of the dorsal pharyngeal wall of the mastax. The ciliary oesophagus is the cellular anterior wall of the stomach lumen, but seems to have the same embryological origin as the pharynx.In Brachionus calyciflorus, its cilia are surrounded by cuticular velums which have the same myelin-like structure and the same function as the buccal velum of Philodina roseola. In all cases, the oesophagus prevents the return of food particles from the stomach to the mastax lumen.     

Effect of fermented milk intake on plasmid transfer and on the persistence of transconjugants in the digestive tract of gnotobiotic mice

Plasmid transfer occurs in the digestive tract and the transconjugants may become durably established. The aim of the present work is to investigate the effect of probiotics on plasmid transfer and on establishment of transconjugants in the gut. Plasmid transfers were carried out in the digestive tract of germ free mice associated with an E. coli K12 donor strain harboring three plasmids (R388, self-transmissible, pCE325 and pUB2380, mobilisable,) and an E. coli recipient strain, PG1, of human origin (Duval-Iflah et al., 1994). Milks fermented with either Lactobacillus bulgaricus or Streptococcus thermophilus or symbiosis, S85, of both strains were given daily as 1/3 of food diet. Fermented milks have no effect on the transfer of R388 and pUB2380 except a slight increase of TC(R388) with milk fermented with S85. Long term ingestion of milk fermented with S85 inhibited the formation and the establishment of transconjugants TC(pCE325). Milk fermented with L. bulgaricus lowered the population density of TC(pCE325) in animals where they were already established. This phenomenon was reversible, since the density of TC(pCE325) increased in the same animals after cessation of supplementation. Bacterial cultures obtained in MRS broth and given in state of drinking water were compared with fermented milks. Bacterial cultures with L. bulgaricus and with S85 favoured the establishment of TC(pCE325). These results indicate for the first time that probiotics have various effects on the formation and/or establishment of transconjugants in the gut of axenic mice. The effects depend on whether the probiotics were cultivated in milk or in MRS, indicating that bacterial metabolites and viable bacteria can be involved.     

Diel changes in the particulate environment,feeding activity and digestive enzyme concentration in neritic zooplankton

Diel changes in the particulate environment and nutritional metabolism of neritic zooplankton were studied in the Bay of Villefranche-sur-mer (France) for 30 h during February. Although the survey was carried out over a period of negligible wind speed, the changes in the particle size spectra and species composition of the Zooplankton sampled suggested an abrupt and temporary oscillation in the water mass at the second sampling time. The rest of the 30-h period was characterized by gradual changes which usually returned to conditions close to, but different from, the starting ones. A clear diel rhythm was recorded for the biochemical composition of the phytoplankton, probably related to the periodicity of the photosynthetic metabolism.The feeding rate of Clausocalanus arcuicornis Giesbrecht, 1888, measured by gut fluorescence, also showed diel rhythmicity with maximum rate at night. Digestive enzyme activities were measured on the total Zooplankton population composed of five major species: Clausocalanus arcuicornis, Paracalanus sp., Calanus helgolandicus Claus, 1863, Acartia clausi Giesbrecht, 1889, and Oikopleura dioica Fol, 1859. The activities of the carbohydrases showed varying patterns of periodicity with one or two night maxima. The proteases showed a different pattern with acidic proteases peaking just before dawn and decreasing gradually during the day and no periodicity for trypsin-like activity. No association could be established between the enzyme changes and those of either the food supply or the species composition of the Zooplankton sampled, suggesting that both feeding and digestion diel rhythms are controlled by an internal clock. Influences of internal, external and experimental factors on the digestive enzyme activity rhythm are discussed. The resulting scheme of short term regulation was compared with that proposed earlier for medium term changes.     

Effects of whole wheat feeding on the development of the digestive tract of broiler chickens

The objective of the current study was to investigate the impact of including whole wheat in broiler diets on the development of the digestive tract. Chickens were fed a standard feed containing 400 g ground wheat/kg or the same diet with a part of the wheat given separately as whole grains that increased progressively from 200 g/kg at 8 d to 400 g/kg at 22 d. Every week, from 16 to 44 d, growth performance, modifications of the size of the digestive tract organs and intestinal enzyme activities were investigated. Morphology of villi and crypts in the small intestinal segments (duodenum, jejunum, ileum) were analyzed at 23 and 44 d. Microbacterial counts were performed in jejunal, ileal and caecal contents weekly from 16 to 44 d.During the adaptation period from 8 to 15 d, the birds fed the whole wheat diet had lower feed intake and lower weight gain. Thereafter, they showed improved growth performance so that by the end of the experiment, they had higher body weight compared to the standard-fed birds, 2430 ± 29 versus 2331 ± 36 g.Higher relative weights of gizzard (+26%) and pancreas (+12%) were observed from 16 to 44 d for whole wheat-fed birds compared to standard-fed birds. No differences in relative size of the different intestinal segments were observed, except that the jejunum was shorter. Increased villus to crypt length and surface ratios were observed at 23 d in the duodenum of whole wheat-fed birds, with no differences in morphometry between groups thereafter. Alkaline phosphatase activity was higher from 16 to 44 d in the duodenum and jejunum of whole wheat-fed birds. However, the activities of the digestive enzymes, leucine aminopeptidase and maltase, were similar between the two diets in the measured intestinal segments.A lower number of facultative anaerobic bacteria was found in the ileum of the whole wheat-fed birds, with no differences between treatments for Escherichia coli and for Lactobacillus counts. In the jejunum and the caeca, no differences in microflora counts were observed.The present results showed that feeding whole grains to broilers led mainly to modifications in the upper part of the digestive tract (gizzard, pancreas) and had little influence on the small and large intestine.