The ingestion in wolf spiders I. Capacity of gut ofLycosa pseudoannulata

An wolf spider, Lycosa pseudoannulata, collected from the field were reared in test tubes supplied with fruit flies as the food, and the number and weight of fruit flies killed per unit time and the weight of residuum of killed flies were recorded. When the cumulative number of flies killed by a spider was plotted against time after the beginning of food supply, the angle of the curve obtained decreased gradually until a constant value. In this time, it seems that the gut of spider had saturated with food and the increase rate of number of flies killed reflects the rate of food disappeared from gut by assimilation and egestion. The amount of ingestion was obtained by subtracting the weight of residuum and the gain of live weight of the spider from the weight of killed flies. After the gut has saturated, the amount of food remained in the gut is considered to be equal to the capacity of gut, which is an essential factor in the study of predation. The amount of food disappearance from gut was also estimated. There was a linear relationship between the log body weight of spiders and the log capacity of gut. The linear relationship was also seen between the log total amount of ingestion and the log total amount of food disappeared from gut.     

The effects of food deprivation, prey density and volume on clearance rates and ingestion rates of Diacyclops thomasi

The ingestion rates of the copepod, Diacyclops thomasi, on thesoft-bodied rotifer, Synchaeta pectinata, increased 10-fold(0.07–0.77 Synchaeta h^–1) over the range 50–250prey l^–1. The saturating functional response curve appearedsigmoid but was statistically indistinguishable from a parabola.The response curve was more linear and 10 times lower over thesame range of density when Diacyclops was offered Kerarellacochleans, a species having a stiffened lorica. Diacyclops maximizedits ingestion rate on Synchaeta as a function of the availablegut space. Predation effort, measured as clearance rates, waslinked tentatively to changes in swimming speed of Diacyclopsand was a function of hunger level. Diacyclops, which were starvedfor varying periods of time, increased their ingestion rateson Synchaeta up to a maximum (-3.0 h^–1) after 7–10h of food deprivation. The gut passage time of Diacyclops wasestimated to be 7–8 h. Therefore, ingestion rates (andclearance rates) appeared to be strongly correlated to the volumeof food in the gut.     

Effects of temperature on food ingestion rate and absorption,retention, and equilibrium burden of phosphorus in an aquatic snail,Goniobasis clavaeformis Lea *

The effects of sublethal temperatures on feeding rates and phosphorus dynamics of a freshwater snail, Goniobasis clavaeformis Lea, were determined and feeding rates were measured at four temperatures. The food source was aufwuchs labelled with radioactive phosphorus. A model was developed to elucidate the results of this type of study. Food ingestion rate increased with increasing temperature up to 14°C and then decreased at temperatures above 14°C. The elimination rate of absorbed phosphorus increased with increasing temperature throughout the entire range of experimental temperatures, 10-19.3°C. Mean retention times of absorbed phosphorus i n Goniobasis were estimated to be 34, 24, 10, and 6 days at 10, 13.8, 15, and 193°C, respectively. Mean retention time of unabsorbed ³²P in the gut of this species as a function of temperature followed the same temperature relationship as that of ingestion rate. The absorption efficiency of phosphorus was estimated to be constant at about 39% for ail experimental temperatures, although the data suggest that the absorption ePRciency may have been related inversely to the rate of gut clearance or directly to the residence time of food in the gut. The equilibrium body load of phosphorus at each experimental temperature was estimated based on concentrations of stable phosphorus in the food source and the kinetics of ³²P in Goniobasis. The equilibrium body burden of phosphorus in Goniobasis increased with increasing temperatures up to a maximum at 11–12°C and then decreased at temperatures above 12°C.     

Determinants of ingestion rates in filter-feeding larval blackflies (Diptera: Simuliidae)

SUMMARY 1. The functional response of the filter-feeding blackfly larva Frosimulium mixtum/fuscum was examined in laboratory experiments. We focused on the relationship between a component of the particle handling process (the cephalic fan flick rate) and ingestion rate, to determine whether ingestion rate is limited by handling-time. The influence of food deprivation on ingestion rate and feeding efficiency also was assessed. 2. Ingestion rate rose asymptotically with increasing food availability, leveling off at a concentration of about 100 mg1^?1. Satiation did not account for this plateau. Flick rate (the frequency with which larvae open and close their cephalic fans) increased in a similar fashion, though flick rate only accounted for about two-thirds of the variation in ingestion rate. 3. A simple equation describing the components of the feeding process in blackfly larvae was developed to investigate alternate flick rate ‘decision rules’ capable of predicting relationships between food concentration, flick rate and ingestion rate. The flick rate did not follow a fixed time rule, in which larvae allow particles to accumulate in the fan for a fixed amount of time prior to retraction. For most food densities, flick rate patterns more closely approximated a fixed number rule, in which fans are retracted after a fixed number of particles accumulate. 4. Flick rate rose with increasing food concentration even after the ingestion rate had levelled off, whereas several optimal filter-feeding models predict that filtering rate should decline as food concentration increases above this level. This predicted behavior was not observed because the number of particles ingested per flick failed to increase with increasing food concentration. 5. The efficiency of particle ingestion (number ingested × number available^?1× 100) was very low (<0.1%), and declined with increasing food concentration. 6. An increase in food deprivation time prior to a feeding trial produced a significant increase in flick rate, ingestion rate and feeding efficiency. This adjustment of feeding behaviour allowed animals to replace their gut contents more quickly following longer periods of food deprivation, which agrees with the qualitative predictions of optimal digestion-time models.     

Optimal foraging: The responses of Peromyscus leucopus to experimental changes in processing time and hunger

Summary Food density, degree of hunger prior to foraging, and food processing difficulty were varied in order to determine their effects on the diet diversity of captive Peromyscus leucopus foraging for buried seeds. No relationship was found between diet diversity and food density. However, diet diversity exhibited a significantly positive relationship with hunger, and a significantly negative relationship with seed processing time. These results strongly support optimal foraging theory.     

Brain activity in hunger and satiety: an exploratory visually stimulated FMRI study

Objective: To explore neuroanatomical sites of eating behavior, we have developed a simple functional magnetic resonance imaging (fMRI) paradigm to image hunger vs. satiety using visual stimulation. Methods and Procedures: Twelve healthy, lean, nonsmoking male subjects participated in this study. Pairs of food‐neutral and food‐related pictures were presented in a block design, after a 14‐h fast and 1 h after ad libitum ingestion of a mixed meal. Statistically, a general linear model for serially autocorrelated observations with a P level <0.001 was used. Results: During the hunger condition, significantly enhanced brain activity was found in the left striate and extrastriate cortex, the inferior parietal lobe, and the orbitofrontal cortices. Stimulation with food images was associated with increased activity in both insulae, the left striate and extrastriate cortex, and the anterior midprefrontal cortex. Nonfood images were associated with enhanced activity in the right parietal lobe and the left and right middle temporal gyrus. A significant interaction in activation pattern between the states of hunger and satiety and stimulation with food and nonfood images was found for the left anterior cingulate cortex, the superior occipital sulcus, and in the vicinity of the right amygdala. Discussion: These preliminary data from a homogenous healthy male cohort suggest that central nervous system (CNS) activation is not only altered with hunger and satiety but that food and nonfood images have also specific effects on regional brain activity if exposure takes place in different states of satiety. Wider use of our or a similar approach would help to establish a uniform paradigm to map hunger and satiety to be used for further experiments.     

An experimental analysis of ingestion rates in an omnivorous species

Food intake is difficult to estimate under natural conditions. We investigated ingestion rates of 14 different food types in 26 captive capuchin monkeys (Cebus apella). The procedure consisted in weighing a piece of food and using a two alternative choice tests to present food to the subject, alone in its cage. We recorded the food chosen and the time it took the subject to consume the food entirely. Consumption time was converted into ingestion rates (g/s) for each food type. Ingestion rates of food types significantly differed, and the difference was significantly higher among foods than among subjects. In particular, ingestion rates of the fruits were higher than those of human-processed food. Interestingly, food preferences were significantly related to energy intake rate, i.e., to the amount of energy ingested per unit of time, but not with ingestion rates or energy content alone. The energy acquired by eating different types of food cannot be calculated on the basis of the time spent eating unless a correction factor for each given food (or similar ones) is applied. Future controlled studies should provide field researchers with such corrections factors, possibly using foods collected in the wild.     

The importance of ingestion rates for estimating food quality and energy intake

Testing ecological or socioecological models in primatology often requires estimates of individual energy intake. It is a well established fact that the nutrient content (and hence the energy content) of primate food items is highly variable. The second variable in determining primate energy intake, i.e., the ingestion rate, has often been ignored, and few studies have attempted to estimate the relative importance of the two predictors. In the present study individual ingestion rates were measured in two ecologically very different populations of Hanuman langurs (Semnopithecus entellus) at Jodhpur, India, and Ramnagar, Nepal. Protein and soluble sugar concentrations in 50 and 100 food items. respectively, were measured using standardized methods. Variation in ingestion rates (gram of dry matter per minute) was markedly greater among food items than among langur individuals in both populations, but did not differ systematically among food item categories defined according to plant part and age. General linear models (GLMs) with ingestion rate, protein, and soluble sugar content explained 40-80% of the variation in energy intake rates (kJ/min). The relative importance of ingestion rates was either similar (Ramnagar) or much greater (Jodhpur) than the role of sugar and/or protein content in determining the energy intake rates of different items. These results may impact socioecological studies of variation in individual energy budgets, investigations of food choice in relation to chemical composition or sensory characteristics, and research into habitat preferences that measures habitat quality in terms of abundance of important food sources. We suggest a definition of food quality that includes not only the amount of valuable food contents (energy, vitamins, and minerals) and the digestibility of different foods, but also the rate at which the food can be harvested and processed. Such an extended definition seems necessary because time may constrain primates when feeding competition is intense and foraging is risk-prone.     

Copepod feeding behavior and the measurement of grazing rates in vivo and in vitro

In this paper some aspects of the use of the gut fluorescence method for estimating ingestion rates have been, examined. One assumption is that gut turnover time in feeding copepods is equal to the gut clearance time in filtered seawater. When arctic Pseudocalanus were pre-fed on Thalassiosira weisflogii, and then given a trace addition of the same C¹⁴-labelled culture, or were transferred to filtered seawater, results suggested that this assumption was probably justified. In another experiment in which Pseudocalanus were fed at the same concentration of either melted ice algae, or pelagic under ice algae, there were significant differences in both gut clearance times and gut pigment levels in the two cases.Pigment: biogenic silica ratios in epontic algae were higher than those in faecal pellets produced by Pseudocalanus feeding on the algae, suggesting that pigment destruction was occurring during grazing. In a 28 hr time course experiment ingestion rates determined by rate of disappearance of particulate chlorophyll were higher than those simultaneously determined by the gut fluorescence method, which also supports the idea of pigment destruction in copepods guts.     

Signalling of hunger when offspring forage by both begging and self-feeding

Studies on vertebrate species in which the offspring obtain food only from their parents have shown that offspring begging conveys information on offspring hunger. It is unclear whether begging can also convey information on hunger in partially begging species, in which the offspring, from hatching, obtain food partly through begging for food from the parents and partly through self-feeding. In partially begging species, offspring hunger state could reflect the amount of food obtained by self-feeding in addition to the amount obtained from the parent, and the offspring could respond to hunger by self-feeding instead of begging. To test whether begging reflected the current hunger state of offspring in the partially begging beetle Nicrophorus vespilloides, we subjected larvae to two deprivation treatments: no access to any food for 2 h (i.e. food-deprived larvae) and no food provided by the parent (i.e. self-feeding larvae). Larvae of both treatments spent more time begging than did control larvae, which had access to food both from the parents and by self-feeding. Furthermore, the amount of begging differed between the treatments, with food-deprived larvae spending more time begging than the self-feeding ones. We conclude that, in partially begging species, food obtained through both foraging strategies, i.e. begging for food from parents and self-feeding, contribute to the offspring's current hunger state, and that begging can convey information about it.     

饥饿和食物单宁酸对东方田鼠(Microtus fortis)食物摄入量和觅食行为的影响

实验室条件下,测定饥饿和食物单宁酸对东方田鼠食物摄入量和觅食行为的影响。结果表明,饥饿使实验个体的食物总摄入量增加,食物摄入率及口量大小随饥饿强度的增大而增加,而觅食频次则无显著改变,实验个体每取食回合的觅食时间呈缓慢增加的趋势,与对照组比较,觅食时间差异不显著。东方田鼠优先选择0%单宁酸食物,次为3%单宁酸食物,而对6%单宁酸食物的摄入量最少。在饥饿条件下,东方田鼠食物摄入率的增加主要源于其口量大小,觅食频次和觅摄食时间对食物摄入量增加的贡献不显著。在饥饿条件下,植食性小哺乳动物并未通过延长觅食时间,降低用于防卫、繁殖活动时间来增加食物摄入量,而是通过增加口量大小,提高其食物摄入率来满足其营养需要。验证了饥饿与植物次生化合物共同作用引起田鼠类动物生理的改变,能影响其食物摄入量及觅食行为的假设。     

Mechanisms of the inhibitory effect of the cyanobacterium Microcystis aeruginosa on Daphnia galeata's ingestion rate

The possible effects of five Microcystis aeruginosa strains (two unicellular and three colony forming) on the filtering and feeding behavior of Daphnia galeata were investigated to clarify the mechanisms of the inhibitory effect on the ingestion rate of the animals. Of the tested cyanobacterial strains, three inhibited Daphnia's food ingestion. This was primarily caused by affecting the frequency and food transport efficiency of the maxillary contractions. As a result, Daphnia's swallowing rate, and in one case the amount of food contained in the swallowed boluses, were lower than in suspensions of well-ingestible food sources. In contrast, there is no indication that Microcystis can influence thoracic appendage beat or rejection rate. It is likely that colony-forming and unicellular strains can affect the ingestion process due to different factors. The mucilage of the colony-forming Microcystis strains HUB-275 and HUB-2334 possibly produced a mechanical hindrance of the maxillules which resulted in an abnormal movement and consequently in the inhibitory effects described above. This was related to the sugar composition of the mucilage polysaccharides, but not to the cellular microcystin content or occurrence of accompanying bacteria. The mucilage-lacking strain HUB 5-2-4, however, must contain another factor which interfered with the maxillules' movement in an unknown way.      

Short-term adaptation of digestive processes in the cockle Cerastoderma edule exposed to different food quantity and quality

Feeding and digestive parameters were analysed in cockles Cerastoderma edule fed for 3 days on two foods of different qualities, both foods given in two different concentrations. With low quality food, gut content was found to increase with ingestion rate. Such increased capacity of the gut to allocate food precludes negative effects upon throughput time, and so absorption efficiency remained nearly constant at the two food concentrations. With high quality food, gut content remained at high constant values and consequently enhancement of food ingestion rate with a high food ration leads to a significant reduction in throughput time, resulting in lower absorption efficiencies. Significantly higher levels of amylases and cellulases have been found within the digestive gland of cockles fed high quality diets. Coincidentally, absorption of carbohydrates is increased and absorption of lipids decreased in such diets as compared to low quality diets. Implications of the positive correlation between digestive enzyme activity and food quality are discussed in relation to the role that both digestive investments and endogenous faecal losses play in digestive processes. Results obtained in this study indicate that investments in the form of digestive enzymes are a key factor in the functional response of cockles to short-term variations in the food regime. Accepted: 13 September 1997     

Functional asymmetry of electric processes in the rabbit brain cortex at formation of the hunger dominant

The motivational condition of hunger and formation of the hunger dominant after daily food deprivation was studied in the conditions of chronic experiments on rabbits. It was shown, that the hunger condition was accompanied by left sided interhemispher asymmetry on indicators of spectral capacity of EEG frontal and right-hand asymmetry sensorimotor areas of the cortex. A hunger dominant was accompanied by falling of spectral capacity of EEG of areas of both hemispheres. The condition of hunger and a hunger dominant were characterized by right-hand asymmetry on average level of EEG coherence of frontal and sensorimotor areas. At transition of a condition of hunger in a hunger dominant there was an average level of EEG coherence decrease in areas of the right hemisphere. Electric processes of the cortex of the brain at a motivational condition of hunger and a hunger dominant were different.     

The control of meal termination in the locust

The relationship between the amount eaten during a meal, meal duration and ingestion rate was investigated in the locust, Locusta migratoria (L.). The results suggested a relatively simple model for the control of meal termination whereby a variety of exogenous and endogenous factors, including chemosensory stimuli provided by the food, the presence of other locusts nearby, age and deprivation-related factors, are integrated within the central nervous system and together contribute to the level of excitation present at the start of a meal. The amount of excitation determines both the mean rate of ingestion during the meal and the amount of inhibition needed to end the meal. Since much of the inhibitory feedback comes from gut stretch, meal size and mean ingestion rate are positively correlated, in fact increasing proportionally, and, hence, meal duration remains constant. At high levels of excitation, however, ingestion becomes rate limited and meal duration subsequently increases proportionally with meal size. Changes in the rate of ingestion throughout a meal were also investigated. The rate declined exponentially but, unlike in the rat, the initial ingestion rate remained constant with changes in excitation and the decay function varied such that small meals began at the same ingestion rate as large meals but the rate of decline was subsequently faster.     

The effects of a low-carbohydrate ketogenic diet and a low-fat diet on mood, hunger, and other self-reported symptoms

Objective: To investigate the effects of weight loss diets on mood, food cravings, and other self‐reported symptoms. Research Methods and Procedures: Mood and other symptoms were evaluated by participant self‐report using the Atkins Health Indicator Test (AHIT) in individuals undergoing weight loss following either a low‐carbohydrate, ketogenic diet (LCKD) or a low‐fat diet (LFD). Participants were 119 overweight community volunteers randomized to an LCKD or an LFD. An additional 51 participants who had completed an earlier trial contributed data for the psychometric analyses but were not included in the prospective analyses. Self‐reported symptom levels on seven scales factor‐analytically derived from the AHIT (negative affect, fatigue, somatic symptoms, physical effects of hunger, insomnia, hunger, and stomach problems) were acquired during 12 visits. Results: After adjusting for the change in BMI over the course of the trial, participants experienced significant improvements in most symptoms regardless of diet. Diet group × visit interactions were observed for negative affect [F(9,803) = 2.30, p = 0.015] and hunger [F(9,803) = 3.62, p < 0.0002]. Examination of means indicated that the LCKD group reported less negative affect and hunger, compared with the LFD group. Discussion: Regardless of diet, participants experienced significant improvement in a broad range of symptoms. Symptoms of negative affect and hunger improved to a greater degree in patients following an LCKD compared with those following an LFD. Whether these symptom changes explain the greater short‐term weight loss generally experienced by LCKD followers deserves further research.     

Microplastic ingestion affects hydrogen production and microbiomes in the gut of the terrestrial isopod Porcellio scaber

Microplastic (MP) is an environmental burden and enters food webs via ingestion by macrofauna, including isopods (Porcellio scaber) in terrestrial ecosystems. Isopods represent ubiquitously abundant, ecologically important detritivores. However, MP-polymer specific effects on the host and its gut microbiota are unknown. We tested the hypothesis that biodegradable (polylactic acid [PLA]) and non-biodegradable (polyethylene terephthalate [PET]; polystyrene [PS]) MPs have contrasting effects on P. scaber mediated by changes of the gut microbiota. The isopod fitness after an 8-week MP-exposure was generally unaffected, although the isopods showed avoidance behaviour to PS-food. MP-polymer specific effects on gut microbes were detected, including a stimulation of microbial activity by PLA compared with MP-free controls. PLA stimulated hydrogen emission from isopod guts, while PET and PS were inhibitory. We roughly estimated 10⁷ kg year⁻¹ hydrogen emitted from the isopods globally and identified their guts as anoxic, significant mobile sources of reductant for soil microbes despite the absence of classical obligate anaerobes, likely due to Enterobacteriaceae-related fermentation activities that were stimulated by lactate generated during PLA-degradation. The findings suggest negative effects of PET and PS on gut fermentation, modulation of important isopod hydrogen emissions by MP pollution and the potential of MP to affect terrestrial food webs.     

The significance of some methodological effects on filtration and ingestion rates of the rotiferBrachionus plicatilis

Filtration rate(F) and ingestion rate(I) were measured in the rotiferBrachionus plicatilis feeding on the flagellateDunaliella spec. and on yeast cells(Saccharomyces cerevisiae). 60-min experiments in rotating bottles served as a standard for testing methodological effects on levels ofF andI. A lack of rotation reducedF values by 40 %, and a rise in temperature from 18° to 23.5 °C increased them by 42 %. Ingestion rates increased significantly up to a particle (yeast) concentration of ca. 600–800 cells · l^–1; then they remained constant, whereas filtration rates decreased beyond this threshold. Rotifer density (up to 1000 ind · ml^–1) and previous starvation (up to 40 h) did not significantly influence food uptake rates. The duration of the experiment proved to have the most significant effect onF andI values: in 240-min experiments, these values were on the average more than 90 % lower than in 15-min experiments. From this finding it is concluded that ingestion rates obtained from short-term experiments (60 min or less) cannot be used in energy budgets, because they severely overestimate the actual long-term feeding capacity of the rotifers. At the lower end of the particle size spectrum (2 to 3 µm) there are not only food cells, but apparently also contaminating faecal particles. Their number increased with increasing duration of experiments and lead to an underestimation ofF andI. Elemental analyses of rotifers and their food suggest thatB. plicatilis can ingest up to 0.6 mJ or ca. 14 % of its own body carbon within 15 min. The long term average was estimated as 3.4 mJ · ind^–1 · d^–1 or ca. 75 % of body carbon · d^–1.Contribution to research project "Experimentelle Marine Ökosystemanalyse" sponsored by the Bundesministerium für Forschung und Technologie, Bonn (Grant No. MFU - 0328/1)     

The influence of social hunger on food distribution and its implications for disease transmission in a honeybee colony

Social insect colonies are characterized by extensive interactions among individuals, exchanges that can also potentially transmit pathogens. The large majority of these social interactions in a honeybee colony result from food transfer among individuals. Since colony hunger is likely to have a significant influence on these interactions, we investigated its effect on the distribution of food within the colony. By pulsing two colonies having different amounts of stored food with a radioactive label, we found that a starved colony sent out a larger number of foragers, brought in more food, and stored more of it than the satiated colony. We also found that the food brought into a starved colony was distributed more uniformly within each age class than that in the satiated colony. The queen and the young individuals received the lowest exposure to the label even though the label entered different regions of the colony at the same rate. The satiation level of the colony did not influence the relative exposures of different age groups to the label but a higher amount of it was stored in the hungry colony. We discuss the significance of these results in terms of the role played by the organizational structure of the honeybee colony on the transmission dynamics of an infectious disease.     

Hunger, partial consumption of prey and prey size preference in a carabid beetle

ABSTRACT.

• 1 Partial consumption of prey and prey size preference were studied in females of the carabid Notiophilus biguttatus F., using different size-classes of the springtail Orchesella cincta (L.) as prey.
• 2 Time to ingest a prey increases disproportionately with prey size, mainly as a consequence of satiation.
• 3 During consumption of a prey the predator's rate of ingestion decreases, partly because of diminishing returns from the prey over feeding time.
• 4 The hypothesis that the diminishing returns from the prey induce partial consumption was refuted.
• 5 Partial consumption in the beetle is due to gut limitation; its occurrence depends on prey size.
• 6 Average weight of prey remains in four prey size classes were close to weights expected from average intercatch intervals and estimates of hunger.
• 7 Prey choice depends on level of food deprivation.
• 8 Partial consumption of prey, prey size preference and profitability of prey in relation to hunger of the beetle are discussed.