Food consumption of vendace Coregonus albula larvae in Lake Lentua, Finland

The daily ration of vendace larvae (mean TL 10·1–12·8 mm) was assessed after a time-intensive field survey in Lake Lentua. Ten larvae were sampled every 2 h throughout the 10-day sampling period and their alimentary tract contents analysed. The gut was cut into four quarters of equal length and each quarter was analysed separately. This procedure enabled the assessment of the proportions of different zooplankton taxa in the diet based on the least degraded first-quarter contents and to reconstruct the entire gut contents. Secondly, the gut passage time of ingested zooplankton was evaluated by comparing the degradation rate of zooplankton in the guts of experimentally fasted larvae to the degradation of zooplankton in the gradient from pharynx to anus among the larvae sampled from the lake. Finally, food consumption was calculated as zooplankton individuals and carbon biomass based on the two variables, gut passage time of constantly feeding larvae and reconstructed gut contents. The daily ration of vendace larvae varied between 14 and 450 zooplankters in the monitored period.     

Interaction between pectin and rat hindgut microflora.

The contents of the lower alimentary tract from rats fed a semisynthetic, pectin-supplemented diet showed increased nitrate reductase activity and an increase in the amount of luminal contents in the intestine and cecum. Nitrate reductase activity was associated with the insoluble fraction of the gut contents which was sedimented by centrifugation (5,100 X g,20 min) and was abolished after treating the animals with streptomycin, neomycin, and bacitracin for 7 days. The pectin-dependent increase in cecal size and microbial nitrate reduction were reversed when animals were transferred from a pectin-supplemented onto a control semisynthetic diet. Polygalacturonic acid (pectic acid) was without effect on either cecal size or cecal microbial nitrate reductase activity. The studies demonstrate that pectin influences microbial metabolism in the alimentary tract.     

Interaction between pectin and rat hindgut microflora

The contents of the lower alimentary tract from rats fed a semisynthetic, pectin-supplemented diet showed increased nitrate reductase activity and an increase in the amount of luminal contents in the intestine and cecum. Nitrate reductase activity was associated with the insoluble fraction of the gut contents which was sedimented by centrifugation (5,100 X g,20 min) and was abolished after treating the animals with streptomycin, neomycin, and bacitracin for 7 days. The pectin-dependent increase in cecal size and microbial nitrate reduction were reversed when animals were transferred from a pectin-supplemented onto a control semisynthetic diet. Polygalacturonic acid (pectic acid) was without effect on either cecal size or cecal microbial nitrate reductase activity. The studies demonstrate that pectin influences microbial metabolism in the alimentary tract.     

Seasonal variation in the diet of Tetrix tenuicornis (Orthoptera: Tetrigidae)

Many animals change their diet during the season according to food availability. The current field study determined whether the groundhopper Tetrix tenuicornis (Orthoptera: Tetrigidae), which specializes on moss and detritus, changes its diet during the season under conditions in which food components are constantly available. Dietary differences of T. tenuicornis were studied through the season, from May to October, by alimentary tract analyses. Detritus and moss (phylloids) dominated the alimentary tract contents, and other components were found in only minor amounts. The diversity of moss species in the alimentary tract varied during the season, and more moss species were consumed in spring and summer than in autumn. Diet was affected by developmental stage, sex (females consumed more food than males), population and abiotic factors. The rate at which detritus was consumed was significantly affected by the ambient temperature but the rate at which moss was consumed was mainly affected by relative humidity. Later instars consumed greater amounts of detritus than younger instars, and this difference corresponded to body size.     

Growth, morphogenesis, and virulence of Candida albicans after oral inoculation in the germ-free and conventional chick

Balish, Edward (Syracuse University, Syracuse, N.Y.), and A. W. Phillips. Growth, morphogenesis, and virulence of Candida albicans after oral inoculation in the germ-free and conventional chick. J. Bacteriol. 91:1736-1743. 1966.-The effects of intestinal bacteria on the multiplication, morphogenesis, and infectivity of Candida albicans in the alimentary tract were investigated by comparing results obtained in germ-free and conventional chicks after oral inoculation. This challenge resulted in the establishment of large numbers of the pathogen in the alimentary tract of each group of chicks; these numbers were increased in crop contents from challenged bacteria-free chicks wherein hyphae predominated over the yeast form. These animals also had lesions of the crop epithelium containing numerous hyphae and few yeast-like forms. In contrast, challenged conventional chicks receiving an adequate diet displayed no evidence of infection. Their alimentary tract contained the yeast form of C. albicans; no hyphae were seen. Although we found bacterial inhibition of C. albicans multiplication in the alimentary tract, this in itself did not seem to explain the resistance to intestinal candidiasis in our conventional chicks. We argued that this resistance to infection was due chiefly to the prevention of hyphal development in C. albicans by intestinal bacteria. C. albicans in the gut of our conventional chicks resulted in some increase in numbers of enterococci in contents from the crop. Increased pH values in contents from the gut of germ-free chicks were not clearly related to infection after challenge. The E(h) of the above crop contents were only slightly decreased in the germ-free crop. Thus the E(h) did not appear to be involved in susceptibility to infection. Invasion of the blood stream and kidneys of conventional chicks by the yeast form of C. albicans occurred in challenged animals receiving a purified diet which had been radiation-sterilized and stored for 6 months at room temperature (25 C). Their growth rate decreased and they became moribund; no hyphae were observed in tissues or intestine of these animals. Challenged bacteria-free chicks receiving the same diet were resistant to the above invasion, although they had crop lesions containing hyphae as described. The resistance of these chicks to systemic invasion was attributed to absence of intestinal bacteria competing for low levels of vitamins in the stored diet. Germ-free chicks had decreased levels of serum gamma-globulin which increased after challenge, whereas this value was unchanged in conventional birds after challenge.     

The adaptation of digestive enzymes to temperature, season and diet in roach Rutilus rutilus L. and rudd Scardinius erythrophthalmus L. Cellulase

The cellulolytic activity of the contents of the intestinal tract of populations of roach and rudd in four Tyrolean lakes was studied. Much of the activity was taken up with the diet. In fish feeding on plants and detritus a lower cellulolytic activity was found than in fish feeding on zooplankton or on arthropods. A seasonal pattern of cellulolytic activity was demonstrated with a peak in the autumn. It is assumed that the cellulolytic activity found in the intestinal contents of cyprinids is insufficient for the digestion of fibre, but that is suffices—particularly in omnivorous species—to support the breakdown of cell walls.     

Intestinal microbial flora of the of the American cockroach, Periplaneta americana L.

A morphological study employing scanning and transmission electron microscopy was made by the alimentary tract of the American cockroach, Periplaneta americana L. A. complex microbiota of diverse morphology, which could not be readily dislodged, was observed and found to be restricted to the hindgut, particularly the colon. Numerous filamentous forms were noted, and some are described, including the morphologically distinct Methanospirillum. Flora was noted attached to the cuticular lining and cuticular filaments of the colon, and several spiral forms were observed in the luminal contents from the colon.     

Why cattle feed much and humans think much - New approach to confirm the expensive tissue hypothesis by molecular data

The “expensive tissue hypothesis” states that large brains are active at high metabolic rates, which have to be financed by a significant trade-off with other organs such as the alimentary tract. Recent morphological findings on primate brains and guts support this idea also considering the importance of high-energy diets as a possible driving power of this process. However, the trade-off correlation between brain and alimentary tract, the essence of the “expensive tissue hypothesis”, has not yet been tested using molecular data to complement morpho-functional findings. We therefore hypothesize that the activity of marker proteins expressed both in brain and alimentary tract should parallel functional morphology in organs at the molecular level. Thus, in animals feeding on hard to digest diet, we would expect a high concentration per unit mass of that marker protein in the digestive tract and reversely a lower concentration in the brain. In contrast, in animals feeding on easily-digested, high-energy food we would expect the reverse pattern. Recent preliminary studies suggest that carbonic anhydrase II (CA-II) could act as a marker. The enzyme concentration was found to increase in the brain with higher cerebral activity from cattle to humans and to reversely decrease in salivary secretions. The reverse concentration of CA-II in saliva and brains of cattle and primates might be the first molecular evidence of the validity of the “expensive tissue hypothesis”.     

The organization of serotonin-, dopamine-, and FMRFamide- containing neuronal elements and their possible role in the regulation of spontaneous contraction of the gastrointestinal tract in the snail Helix pomatia

Summary The distribution of serotonin-, tyrosine hydroxylase-, and FMRFamide-immunoreactive neuronal elements, as well as the concentrations of serotonin and dopamine in the different parts of the gastrointestinal tract, were studied in the snail Helix pomatia. The sensitivity of the spontaneous contractions of the alimentary tract to serotonin, dopamine, and FMRFamide was also tested. Serotonin-, tyrosine hydroxylase-, and FMRFamide-immunoreactive elements could be demonstrated in each part of the gastrointestinal tract, but they showed different innervation patterns. Serotonin- and tyrosine hydroxylase-immunoreactive elements were dominant in the submucosal layer, whereas FMRFamide-immunoreactive elements were dominant in both the mucosal and submucosal layers. Tyrosine hydroxylase-immunoreactive elements were confined to the longitudinal muscle trabeculae of submucosa, whereas serotonin-immunoreactive elements were distributed throughout the submucosal layer. No serotonin-immunoreactive cell bodies, but only fibers, could be detected in the gastrointestinal tract, and therefore they represent extrinsic elements. Tyrosine hydroxylase- and FMRFamide-immunoreactive cell bodies represent intrinsic elements of the tract. The occurrence and density of the serotonin- and tyrosine hydroxylase-immunoreactive elements showed significant differences in the different parts of the alimentary tract, in accordance with HPLC assays, which revealed a significant frontocaudal decrease in both the serotonin (from 2.11 to 1.21 pM/mg) and dopamine (from 3.28 to 0.52 pM/mg) contents of the different parts of the alimentary tract. Dopamine at 10-5 M concentration proved to be effective only on the longitudinal muscles by increasing the tone and frequency of contractions, but was ineffective on the circular muscles. Serotonin affected both the longitudinal and circular muscles. Serotonin at 10-5 M concentration decreased the tone and increased the frequency of low-amplitude contractions of the longitudinal muscles of the esophagus and the gizzard but increased both the tone and frequency of the crop. Serotonin at 10-9 M concentration slightly decreased the tone and blocked the contractions of the circular muscles in the crop but at 10-5 M concentration induced contractions of the circular muscles in the gizzard. FMRFamide at 10-6 M concentration decreased the tone and was shown to block the contractions of both the longitudinal and circular muscles.     

Prey selectivities of threespine sticklebacks (Gasterosteus aculeatus) and phantom midge larvae (Chaoborus spp.) in Newfoundland lakes

SUMMARY. 1. Threespine stickleback ( Gasterosteus aculeatus ) and Chaoborus ( C. punctipennis and C. trivittatus ) planktivore populations were sampled from several oligotrophic lakes on the Avalon Peninsula of Newfoundland, Canada. Pelagic zooplankton communities in these lakes consist of Daphnia catawba, Holopedium gibberum, Eubosmina longispina, Leptodiaptorma minutus, Epischura nordenskioldi, Cyclops scutifer and rotifers ( Conochilus unicornis, Keratella and Kellicottia spp.).
2. Comparison of gut contents of G. aculeatus and crop contents of later instar Chaoborus larvae with lake zooplankton communities indicated that the vertebrate and invertebrate plank tivores show contrasting species and size selectivities in their choice of zooplankton prey. Prey selectivities were quantified by means of the selectivity index α.
3. G. aculeatus showed positive selectivity for larger zooplankton (greater than 0.76 mm in length), typically the cladoceran D. catawba , while Chaoborus larvae showed positive selectivity for smaller zooplankton (less than 0.50 mm in length), typically the cladoceran E. longispina . While rotifers never featured in the diet of the sticklebacks, these zooplankters were a common component of the chaoborid diet. H. gibberum , with its gelatinous sheath, was rarely found in the gut contents of G. aculeatus and was never found in the crop contents of Chaoborus larvae.
4. Selective predation by these planklivores in the relatively shallow and well-mixed oligotrophic Avalon lakes may influence species composition and size structure of the pelagic zooplankton communities.     

Diet composition of chub,Squalius cephalus (Teleostei: Cyprinidae), in Lake Tödürge,Sivas, Turkey

Digestive tract contents of 241 specimens captured between March 1998 and November 1999 were analysed using both qualitative and quantitative methods to determine diet composition and feeding habits of Squalius cephalus (L., 1758) inhabiting Lake Tödürge, Turkey. Ages ranged from I to VI years; 60.6% of the fish were females, 39.4% males. The chub population appeared to consume a wide range of food items such as phytoplankton, zooplankton, nematodes, insects, fish, macrophytes, plant and animal detritus, whereby zooplankton (69.2%) predominated. Although individuals in the age I group preferred plankton (phytoplankton frequently; zooplankton infrequently), the older specimens (age groups IV, V and VI) behaved mostly as carnivores but also consumed some macrophytes. While there were no significant differences between diet compositions of males and females, seasonal changes were observed in frequency of occurrence, quality and quantity of consumption, and feeding activity. The chub specimens fed most heavily during spring (the pre‐spawning period: March, April and May). Highest food volume (13.0 cm³) consumed was in May and the lowest in September (2.0 cm³) while also being correlated with temperature. All of the food items were found in the digestive tract (82.1% of the specimens examined over all seasons). Highest fullness (84.9%) was reached in autumn and the lowest during summer (79.8%).     

INTERACTIONS BETWEEN SOIL BACTERIA AND THE MOLLUSCAN ALIMENTARY TRACT

The alimentary tract is a major site of interaction betweenan animal's ecosystem and its physiology. It may be intermittentlyor permanently populated by microorganisms from its environmentthat could be beneficial or pathogenic in their influence. Thebacterial populations of the snail (H. aspersa) and the woodlouse(O. asellus) have therefore been estimated in terms of colonyforming units. gm body weight^–1. The bacteria in the snailappear to be similar to those found in soil and show wide resistanceto antibiotics. The main types are gram negative rods tentativelyidentified as belonging to Pseudomonas, Xanthomonas, Acinobacter,Vibrio and Enterobacteriaceae. Some gram positive and endosporeforming bacteria of Bacillus, Staphylococcus and Micrococcusspp were also present. The numbers of bacteria increase towardsthe posterior of the alimentary tract although the numbers inthe digestive gland are more constant. An artificial diet is described that can be used to feed snailsand study the effects of known amounts of additives. When starvedor kept under clean conditions the bacterial population of thesnail gut falls and the thickness of the alimentary tract decreases.All the indications are that the bacteria in the alimentarytract of the snail are indiscriminately accumulated from thenatural environment and are transient populations. (Received 7 June 1989; accepted 24 July 1989)     

Bdellovibrio and the intestinal flora of vertebrates.

Bdellovibrio strain MS7 force-fed to fish and frogs via an intragastric tube did not become an integral component of the intestinal microflora. Strain MS7 fed to mice in drinking water was not recovered from the intestinal tract of mice. However, in vitro, the organism multiplied in intestinal contents of frogs and mice. Bdellovibrio inoculated into rabbit ileal loops was greatly reduced in number within 24 h. It was concluded that strains MS7 could be considered nonpathogenic to animals, at least when introduced into the digestive tract, and that it is not feasible at the present time to lyse pathogenic, gram-negative bacteria in the alimentary tract with Bdellovibrio.     

Bdellovibrio and the intestinal flora of vertebrates.

Bdellovibrio strain MS7 force-fed to fish and frogs via an intragastric tube did not become an integral component of the intestinal microflora. Strain MS7 fed to mice in drinking water was not recovered from the intestinal tract of mice. However, in vitro, the organism multiplied in intestinal contents of frogs and mice. Bdellovibrio inoculated into rabbit ileal loops was greatly reduced in number within 24 h. It was concluded that strains MS7 could be considered nonpathogenic to animals, at least when introduced into the digestive tract, and that it is not feasible at the present time to lyse pathogenic, gram-negative bacteria in the alimentary tract with Bdellovibrio.     

The physiological role of liver alcohol dehydrogenase

1. Yeast alcohol dehydrogenase was used to determine ethanol in the portal and hepatic veins and in the contents of the alimentary canal of rats given a diet free from ethanol. Measurable amounts of a substance behaving like ethanol were found. Its rate of interaction with yeast alcohol dehydrogenase and its volatility indicate that the substance measured was in fact ethanol. 2. The mean alcohol concentration in the portal blood of normal rats was 0.045mm. In the hepatic vein, inferior vena cava and aorta it was about 15 times lower. 3. The contents of all sections of the alimentary canal contained measurable amounts of ethanol. The highest values (average 3.7mm) were found in the stomach. 4. Infusion of pyrazole (an inhibitor of alcohol dehydrogenase) raised the alcohol concentration in the portal vein 10-fold and almost removed the difference between portal and hepatic venous blood. 5. Addition of antibiotics to the food diminished the ethanol concentration of the portal blood to less than one-quarter and that of the stomach contents to less than one-fortieth. 6. The concentration of alcohol in the alimentary canal and in the portal blood of germ-free rats was much decreased, to less than one-tenth in the alimentary canal and to one-third in the portal blood, but detectable quantities remained. These are likely to arise from acetaldehyde formed by the normal pathways of degradation of threonine, deoxyribose phosphate and beta-alanine. 7. The results indicate that significant amounts of alcohol are normally formed in the gastro-intestinal tract. The alcohol is absorbed into the circulation and almost quantitatively removed by the liver. Thus the function, or a major function, of liver alcohol dehydrogenase is the detoxication of ethanol normally present. 8. The alcohol concentration in the stomach of alloxan-diabetic rats was increased about 8-fold. 9. The activity of liver alcohol dehydrogenase is generally lower in carnivores than in herbivores and omnivores, but there is no strict parallelism between the capacity of liver alcohol dehydrogenase and dietary habit. 10. The activity of alcohol dehydrogenase of gastric mucosa was much decreased in two out of the three germ-free rats tested. This is taken to indicate that the enzyme, like gastric urease, may be of microbial origin. 11. When the body was flooded with ethanol by the addition of 10% ethanol to the drinking water the alcohol concentration in the portal vein rose to 15mm and only a few percent of the incoming ethanol was cleared by the liver.     

Gastric digestion and nutrient absorption along the alimentary tract of whiting (Merlangius merlangus L.) fed on natural prey

Studies on the digestion process in fish can elucidate some aspects of nutritional physiology. The movements of food items in the alimentary tract are observed using X‐radiography techniques, and nutrient absorption along the alimentary tracts (expressed as relative percentage absorption gradient) is calculated based on the ash contents of adjacent samples. Apparent digestibility coefficient (ADC) values for protein (80–94%), lipid (90–97%), carbohydrate (80.5%) and energy (85–96%) calculated from laboratory‐fed whiting were comparable with those for other fish fed suitable diets. Considerable proportions of all nutrients were absorbed in the short region (anterior intestine/pyloric caeca) but active absorption continued for all nutrients in transit along the longer middle and posterior intestinal segments. In wild whiting samples, the estimated ADC values were protein (65%), lipid (81%) and energy (65%) in passage from the stomach to the rectal region. It was not possible to ascertain the prey in intestinal samples, which probably contained a mixture of species. Sprats and brown shrimps probably dominated the diet, based on biochemical analysis of stomach contents, but polychaetes and other crustaceans could have made a minor contribution.     

Size-dependent attack rate and handling capacity: inter-cohort competition in a zooplanktivorous fish

Two size‐dependent processes, metabolic requirements and foraging capacity, heavily influence the competitive ability of organisms. We studied the size‐dependent competitive ability of roach (Rutilus rutilus) in a laboratory experiment to determine the attack rate of roach as a function of roach and zooplankton sizes. The estimated size‐dependent attack rates, size‐dependent metabolic demands and handling capacities were subsequently used to interpret the outcome of a competition experiment between two size classes of roach. Furthermore, size‐dependent attack rates were implemented in an optimal foraging model to predict consumption rates and zooplankton selection to reveal the mechanisms behind competition.
The attack rate first increased with roach size to a maximum around 160 mm to thereafter decrease. Based on this result, we predicted that, small (150 mm) roach had a double advantage in competition for zooplankton in the pond experiment due to their higher attack rate and their lower metabolism compared to large (230 mm) roach. As expected, small roach depressed total zooplankton biomass to a higher extent than large roach, included more zooplankton in their diet and consumed smaller zooplankton. Predicted smallest size class of zooplankton in the diet was close to the observed. Also as expected, large roach fed more on the benthic resource and depressed the benthic resource to a larger extent than small roach. Large roach affected large zooplankton to a higher extent during the first part of the experiment, which could be related to their overall higher handling capacity. The higher impact of large roach on large zooplankton during the first part of the experiment, in turn, resulted in a lower estimated mass intake of zooplankton by small roach in the mixed treatment compared to small roach only treatments. Both small and large roach had a lower growth rate in the mixed treatment compared to single size class treatments. We relate the lower growth rate of small roach in the mixed treatment to large roach's higher efficiency on benthic resources and on large zooplankton during the first part of the experiment. In correspondence with diet data, large roach preferred the shore area of the pond with more benthic invertebrates and were also found more often close to the bottom. Although our results are explainable by exploitative interactions, the fact that the presence of large roach affected the feeding position of small roach points to that social interactions were also involved. Overall, our study implies that a mechanistic understanding is crucial for the interpretation of competition experiments, especially in systems with size‐structured interactions.     

美国白蛾幼虫消化道形态和超微结构观察

美国白蛾Hyphantria cunea Drury是我国重要的林业检疫性害虫之一,世界范围内寄主多达600余种,对我国林业生产和生态环境建设造成了巨大损失。明确美国白蛾幼虫消化道各部分的形态结构,可为进一步研究其幼虫的食性及消化机能奠定基础。利用光学显微镜、扫描电子显微镜与透射电子显微镜观察了美国白蛾6龄幼虫消化道形态及超微结构。美国白蛾幼虫的消化道由前肠、中肠、后肠组成。前肠是消化道最长的部分,占整个消化道的54.27%,包括咽、食道、嗉囊、前胃四部分;中肠较短,占整个消化道的21.28%,内部具围食膜;后肠由幽门、回肠、结肠和直肠组成,幽门由幽门锥和幽门瓣组成。马氏管共6条,丝腺2条。美国白蛾幼虫消化道总体结构大部分鳞翅目消化道结构相似,但是其前肠在长度上发生了较大的变异,本文进一步讨论了美国白蛾幼虫消化道结构与其食性及耐饥饿能力等的相关性。     

Feeding patterns of the dominant benthic and demersal fish community in a temperate estuary

The diet and feeding relationships of the 12 most abundant benthic and demersal fish species of the Mondego Estuary, Portugal, were studied between June 2003 and May 2006. Fishes were caught during the night using a 2 m beam trawl. The stomach contents were analysed for prey identification, counting and weighing. According to prey importance in diets, three main feeding guilds were identified: (1) invertebrate feeders, (2) invertebrate and fish feeders and (3) plankton and invertebrate feeders. Besides these main feeding guilds, some fishes also presented fractions of algae and zooplankton in their stomach contents. The most abundant prey items were macroinvertebrates, with several polychaetes ( Nephtys spp., Capitellidae, Spionidae and Eunicidae), Corophium spp. and Crangon crangon among the dominant prey. Pomatoschistus spp. were the most preyed on fishes. Several fish species showed a tendency for a specialized diet, but almost all also showed some degree of opportunistic feeding by preying on other food resources. High diet overlap was found between some fish species, yet exploitative competition could not be concluded.     

Feather eating in Great Crested Grebes Podiceps cristatus: a unique solution to the problems of debris and gastric parasites in fish-eating birds

The occurrence of feathers in stomachs of 407 Great Crested Grebes Podiceps cristatus from Lake IJsselmeer, The Netherlands, is described. Only four of the 8718 identified stomach feathers originated from a species other than Great Crested Grebes. In all, 68% were breast and belly feathers and 19% were flank feathers. Flank feathers were positively selected from those becoming available during moult, and also occurred more in the ejected feather pellets than expected from the intake. This suggests that flank feathers, which are long and curved and have a black tip, may be especially suited for the formation of pellets. Feather ingestion was more than balanced by feather production. Feathers were most abundant in stomachs in autumn and were least numerous in winter. Most of this variation can be explained by seasonal differences in the intensity of body moult. In addition, the type of prey was related to the number of ingested feathers. When the diet consisted of smelt, which leave little indigestible matter, more feathers were eaten than with a diet of perch and pikeperch, which leave more fish debris. We suggest the hypothesis that ingested feathers, in the absence of other indigestible matter, contribute substance to the stomach content, enabling the formation of pellets that can be ejected. The habit of regularly ejecting the stomach contents minimizes the chance that any serious population of gastric parasites will build up in the upper part of the alimentary tract.