The effect of food deprivation on drinking and running in Mongolian gerbils

Three experiments are reported in which adult male Mongolian gerbils (Meriones unguiculatus) were subjected to various degrees of partial food deprivation, with or without simultaneous access to a running wheel. Experiment 1 showed that restricted feeding caused drinking to increase and running to decrease, and it offered no support for the idea that running might substitute for drinking. Experiment 2 showed that running declined, and then at least partly recovered, as a function of body weight loss, in gerbils that were not allowed to become hyperdipsic. Experiment 3 showed that drinking remained at a high level during prolonged exposure to restricted feeding, but reverted to baseline level more rapidly than did body weight when free feeding was reinstated. The results do not support the idea that drinking and running are interchangeable members of a set of activities facilitated by food deprivation, and they show that neither drinking nor running is related to degree of body weight loss in a simple manner.     

Feeding preferences and food searching strategies mediated by air- and water-borne cues in the mud whelk Terebralia palustris (Potamididae: Gastropoda)

The gastropod T. palustris is one of the major species responsible for leaf consumption and degration within the Indo-Pacific mangrove forests, and it strongly competes with herbivorous sesarmid crabs in consuming fallen leaves. This snail feeds at high and low tides and it is able to locate food items by means of chemical cues. The aim of this study was to assess the food preferences of T. palustris and to define its feeding strategies at low and high tides, by conducting field trials on water-borne mediated food location at high tide, grazing rate and the chemical attraction exerted by different mangrove leaves. The results showed that T. palustris was able to perceive underwater grazed leaves. In addition, we demonstrated that T. palustris consumes all the mangrove species (preferentially the Rhizophoraceae leaves) but Xilocarpus granatum. Moreover, this snail is differentially attracted to different mangrove species: the major attractive power is wielded by the rhizophoracean species and Pemphis acidula, while X. granatum does not attract this snail at all. The efficacy and adaptive value of a chemically mediated food searching strategies is unquestionable since by using this ability T. palustris can locate and reach the leaves it preferentially consumes. Moreover, T. palustris is the only macrobenthic species of East Africa mangroves able to search, detect and consume mangrove leaves at both high and low tides. Such an expanded feeding window permits T. palustris to occupy temporal niches left empty by the sesarmid crabs.     

Owl Monkeys (Aotus nigriceps and A. infulatus) Follow Routes Instead of Food-Related Cues during Foraging in Captivity

Foraging at night imposes different challenges from those faced during daylight, including the reliability of sensory cues. Owl monkeys (Aotus spp.) are ideal models among anthropoids to study the information used during foraging at low light levels because they are unique by having a nocturnal lifestyle. Six Aotus nigriceps and four A. infulatus individuals distributed into five enclosures were studied for testing their ability to rely on olfactory, visual, auditory, or spatial and quantitative information for locating food rewards and for evaluating the use of routes to navigate among five visually similar artificial feeding boxes mounted in each enclosure. During most experiments only a single box was baited with a food reward in each session. The baited box changed randomly throughout the experiment. In the spatial and quantitative information experiment there were two baited boxes varying in the amount of food provided. These baited boxes remained the same throughout the experiment. A total of 45 sessions (three sessions per night during 15 consecutive nights) per enclosure was conducted in each experiment. Only one female showed a performance suggestive of learning of the usefulness of sight to locate the food reward in the visual information experiment. Subjects showed a chance performance in the remaining experiments. All owl monkeys showed a preference for one box or a subset of boxes to inspect upon the beginning of each experimental session and consistently followed individual routes among feeding boxes.     

Evidence for search image in blackbirds Turdus merula L.: long-term learning

The feeding behaviour of free-flying and captive blackbirds Turdus merula L. was observed over a number of days to investigate their ability to see cryptic food. Sequences of eight tests which contained equal numbers of ‘cryptic’ and ‘conspicuous’ tests were presented to the birds of the first two experiments. The blackbirds in experiment 1 increased their feeding rate for both cryptic and conspicuous food, which suggests that search images were not acquired but that the physical acts of feeding were perfected (or that they altered their acceptance of green food). In contrast, the ‘residual search time’ (the bird's total search time minus handling and movement times) decreased over the series of four tests with cryptic green prey, but remained constant over the four tests with conspicuous prey (experiment 2). The blackbirds exploited the cryptic prey using their previous experience of searching for such food. This suggests that search images can be effective over eight feeding sessions, spanning 4–30 days. Similar results were obtained over a 9-day period with four juvenile blackbirds in captivity (experiment 3). With experience they also became expert in their assessment of backgrounds set up without prey.     

Food-attraction conditioning in the snail,Helix pomatia

Adult pulmonate snails (Helix pomatia) were released equidistant between two types of food, carrot and potato, respectively. Naive snails moved in different directions and did not locate either food above chance, although both foods were readily eaten upon direct contact. After a single carrot feeding episode, 75% of the carrot-fed snails moved directly towards the carrot and ate it. Conversely, potato-fed snails located the potato in 67% of the cases. Snails that were fed apple or lettuce behaved like naive animals, with the majority of animals (75% in both cases) locating neither the carrot nor the potato.The ability of snails to locate this particular food after a single feeding episode was maintained for at least 11 days, provided that the snails were not exposed to other foods in the interim. If the animals were fed a different food (but still tested for food-finding ability to the initially conditioned food) their orientation preference decreased gradually over a period of 5 days.Although the snails' orientation is based upon olfactory cues, exposure to food odor alone is not sufficient to enable food-finding; additional feeding related stimuli are necessary.These findings indicate that Helix do not possess a predisposition for the foods tested, and further suggest that processes underlying food-finding and food selection are strongly influenced by learning experiences. The conditioning phenomenon underlying food-finding behavior has been called Food-Attraction Conditioning, and appears to be a crucial link between the ecologies of learning and foraging behaviors. The accessibility of the snail's nervous system should permit neuronal analysis of the mechanisms underlying such a unique and complex learning phenomenon.     

Do female tamarins use visual cues to detect fruit rewards more successfully than do males?

Primates are unique among eutherian mammals for possessing trichromatic colour vision. It is generally proposed that trichromacy evolved to aid detection of ripe fruits against mature foliage. However, while trichromacy is routine in all Old World monkeys and apes (the catarrhines), a cone opsin polymorphism in New World monkeys (the platyrrhines) results in foraging groups with mixed capacities for chromatic distinction. Although 50-66% of female platyrrhines are trichromatic, all males are dichromatic. Here, we test the hypothesis that trichromatic platyrrhines use visual cues to detect fruit rewards more successfully than do males. Specifically, we ask whether female emperor tamarins, Saguinus imperator imperator, and saddleback tamarins, S. fuscicollis weddelli, are the first members of their foraging group to locate food patches; and, furthermore, whether they are more successful than males in using colour, shape and size cues to discriminate between sham and reward feeding sites. Our results show that females and males do not differ in their ability to locate or discriminate between feeding sites. We conclude that trichromatic vision in female tamarins does not confer an advantage for detecting yellow fruit rewards against mature foliage. Copyright 2003 The Association for the Study of Animal Behaviour. Published by Elsevier Ltd. All rights reserved.      

Behaviorally specific inhibition of sham feeding by amylin

To further characterize amylin’s inhibitory action on feeding, we examined the effects of intraperitoneal injections of amylin on sham feeding of sucrose in food-deprived male rats with chronic gastric cannulas. Thirty and 100 μg/kg amylin reduced sham feeding, but did not terminate it or elicit the behavioral sequence of satiety. Real feeding of sucrose, but not sham feeding, was reduced after injection of 10 μg/kg amylin. Amylin’s inhibitory effect on sham feeding appeared behaviorally specific because neither 30 nor 100 μg/kg amylin affected sham drinking of water in thirsty rats and because no abnormal behaviors occurred. We conclude that amylin has a behaviorally specific satiating effect on sucrose sham feeding that is insufficient to elicit satiety in absence of gastric or postgastric food stimulation.     

Opioid modulation of ingestive behaviors in the spiny mouse (Acomys cahirinus)

Feeding and drinking behavior were studied in deprived or sated spiny mice (Acomys cahirinus) at various time intervals following peripheral administration of naloxone hydrochloride and butorphanol tartrate. Naloxone attenuated both food and water intake, but not latency to respond, indicating existence of functional opioid-sensitive feeding and drinking systems in this species. Butorphanol tartrate, a mixed opioid agonist/antagonist produced a dose-related enhancement or suppression of feeding, the former naloxone reversible, but had no measureable effect on drinking.     

The evidence of apelin has the bidirectional effects on feeding regulation in Siberian sturgeon (Acipenser baerii)

Apelin is a peptide, mainly produced in the brain, which participates in several physiologic effects. However, knowledge about the mechanism of appetite regulation in teleosts, including the role of apelin is not well understood. The aim of this study is to explore the effect of feeding status on the expression of apelin mRNA in the whole brain and the effects of injection of apelin on food intake in Siberian sturgeon (Acipenser baerii). In this study, we first cloned the apelin cDNA sequence of the Siberian sturgeon. We obtained a 1046-bp cDNA fragment, including a 237-bp open reading frame (ORF) that encoded 78 amino acids. Apelin was widely distributed in 11 tissues related to feeding regulation, with the highest expression in thewhole brain, followed by the spleen and trunk kidney. In addition, we measured the effects of periprandial (preprandial and postprandial) change, fasting and re-feeding on apelin mRNA expression in whole brain. The level of apelin mRNA was significantly decreased 1 h after feeding. The results of the fasting experiment showed that the expression of apelin mRNA in the brain was significantly reduced after 1 day of fasting but consistently increased throughout the 15-day food deprivation period. When the 15-day fasted fish were re-fed, apelin mRNA expression in the brain was significantly increased as compared to that of the control. These results suggest that apelin may play a bidirectional role in the regulation of food intake in the Siberian sturgeon. In order to further examine the effect of apelin on feeding regulation in Siberian sturgeons, acute and chronic intraperitoneal (i.p.) injection experiments were performed and food intakes were recorded. Results showed that acute i.p. injection of apelin-13 reduced food intake, however, chronic i.p. injection apelin-13 increased the food intake for 7 days in Siberian sturgeons. In conclusion, our results show that apelin has a bidirectional effect on feeding regulation in Siberian sturgeons by acting as a satiety factor in short-term feeding regulation and a starvation factor in long-term feeding regulation.     

Variables Controlling Entry into and Exit from the Steady-State,One of Two Modes of Feeding in Aplysia

Background

Aplysia feeding is a model system for examining the neural mechanisms by which changes in motivational state control behavior. When food is intermittently present, Aplysia eat large meals controlled by a balance between food stimuli exciting feeding and gut stimuli inhibiting feeding. However, when food is continuously present animals are in a state in which feeding is relatively inhibited and animals eat little. We examined which stimuli provided by food and feeding initiate steady-state inhibition of feeding, and which stimuli maintain the inhibition.

Results

Multiple stimuli were found to control entry into the steady-state inhibition, and its maintenance. The major variable governing entry into the steady-state is fill of the gut with bulk provided by food, but this stimulus cannot alone cause entry into the steady-state. Food odor and nutritional stimuli such as increased hemolymph glucose and L-arginine concentrations also contribute to inhibition of feeding leading to entry into the steady-state. Although food odor can alone cause some inhibition of feeding, it does not amplify the effect of gut fill. By contrast, neither increased hemolymph glucose nor L-arginine alone inhibits feeding in hungry animals, but both amplify the inhibitory effects of food odor, and increased glucose also amplifies the effect of gut fill. The major variable maintaining the steady-state is the continued presence of food odor, which can alone maintain the steady-state for 48–72 hrs. Neither increased glucose nor L-arginine can alone preserve the steady-state, although they partially preserve it. Glucose and arginine partially extend the effect of food odor after 72 hrs.

Conclusions

These findings show that control of Aplysia feeding is more complex than was previously thought, in that multiple inhibitory factors interact in its control.     

Identification of stimuli and input pathways mediating food-attraction conditioning in the snail, Helix

Snails become conditioned by a single feeding episode to locate foods which they were unable to locate prior to feeding. To identify which of the different stimulus parameters of the food mediate learning, snails were presented with isolated stimulus components during feeding and re-tested the next day for their ability to locate the food. None of the individual components was sufficient to promote conditioning. Odor combined with a bulk stimulus conditioned the animals, as indicated by their subsequently locating the food. Elimination of the olfactory sensory inputs from the anterior and/or posterior tentacles prior to conditioning revealed that the acquisition of the olfactory memory requires olfactory stimulation of the sensory epithelia on the anterior tentacles. Recall of memory during olfactory orientation requires functional epithelia on the posterior tentacles, which suggests that the same odor is processed by different input pathways under different situations. Animals with the olfactory epithelia functional on the same side during conditioning and food searching were able to locate the conditioned food. Animals with different epithelia functional during conditioning and food searching failed, which suggests that olfactory memory is stored within one side of the nervous system and cannot be accessed from the contralateral side. Accepted: 28 November 1997     

The very hungry amphipod: the invasive <Emphasis Type="Italic">Dikerogammarus villosus</Emphasis> shows high consumption rates for two food sources and independent of predator cues

The invasion of the Ponto–Caspian amphipod Dikerogammarus villosus in European rivers is assumed to reduce macroinvertebrate diversity and to alter ecosystem functions. D. villosus shows an extraordinarily flexible feeding behavior including the ability to use various food sources. On the other hand, its response to predation risk seems to depend on environmental factors. To evaluate the ecological function of D. villosus, we estimated the daily food consumption for different food sources and analyzed potential effects of predator avoidance behavior on feeding. D. villosus consumption of willow leaves or chironomid larvae was quantified in 24-h laboratory experiments with and without kairomones of the European bullhead (Cottus gobio). Consumption rates were estimated based on gut content and gut evacuation rate under semi-natural laboratory conditions enabling the animals to feed over the whole time of the evacuation rate experiment. We observed very high evacuation rates and consequently high consumption rates up to 89% of body weight per day. Consumption rates differed significantly between food sources: D. villosus ingested more leaves than chironomid larvae. In contrast, predator cues did not affect the feeding of D. villosus. This might be explained by its strong refuge affinity and probably benefits its successful invasion. A comparison of the estimated consumption rates with results of an own consumption experiment (and other studies) under more artificial conditions indicated that more natural conditions result in higher consumption rates. Consequently, feeding rates from highly artificial experiments should be used with great caution to assess the ecosystem function of D. villosus.     

Factors affecting the drinking behavior of black howler monkeys (Alouatta pigra)

Water is essential for animals, and is particularly critical for thermoregulation. Animals obtain water from three main sources, free water, water contained in food, and water produced in the body during metabolism. Howler monkeys (Alouatta spp.) spend a small proportion of their time drinking water and some populations have not been observed drinking, suggesting they obtain most of their water requirements in food or by metabolism. However, when howler monkeys have been observed drinking there is evidence suggesting the drinking is associated with low precipitation, temperature, and fruit consumption, and high mature leaf consumption, although it remains unclear which factors determine drinking by this genus. In this study we tested the hypothesis that drinking by howler monkeys results from increased hydration requirements in drier climates and from lower consumption of foods rich in water (e.g., new leaves, fruit). We tested this hypothesis by comparative analysis of 14 groups of Yucatán black howler monkeys (A. pigra) living under different climatic conditions. From April 2005 to November 2008 we collected a total of 3,747.2 focal observation hours of the feeding and drinking behavior of 60 individuals, with data on ambient temperature and rainfall. Individuals spent more time drinking when they lived in habitats with higher maximum temperature and when they consumed more mature leaves. For this species, therefore, drinking seems to be linked to heat stress and a low availability of water in ingested food.     

Neuropeptide Y: stimulation of feeding and drinking by injection into the paraventricular nucleus

Neuropeptide Y (NPY), a peptide contained within numerous presynaptic terminals in the hypothalamic paraventricular nucleus (PVN), was injected directly into the PVN of satiated, brain-cannulated rats, and food and water intake were measured 0.5, 1, 2 and 4 hrs postinjection. Neuropeptide Y (24 and 78 pmoles/0.3 microliter isotonic saline) caused a dose-dependent increase in food intake, as well as a small, dose-dependent increase in water intake. This effect on feeding occurred even when food was not presented until 4 hrs postinjection. To determine the behavioral specificity of this effect, the impact of PVN injection of NPY (78 pmoles) on various behaviors was observed. With food available, only feeding and drinking behavior were affected. No change in other behaviors, including grooming, rearing, sleeping, resting or different levels of activity, was observed. With food absent, NPY still elicited drinking, suggesting that this is a primary effect, rather than secondary to the feeding. In addition to drinking, NPY reliably increased activity while decreasing sleep and grooming. These results suggest an important role for hypothalamic NPY, or a structurally-related peptide, in the regulation of feeding and drinking behavior.     

Drinking,but not feeding,is opiate-sensitive in hamsters

The long-lasting opiate antagonist, naltrexone (NTX), was examined for its effects on various types of consummatory behavior in male golden hamsters and rats. Rat, but not hamster, 24 hr food and water intakes were significantly decreased by four daily NTX (10.0 mg/kg) injections. Hamsters displayed a minimal night to day feeding ratio compared to rats. hamsters increased food intake following insulin (50 U/kg) administration, but not after 24 hr food deprivation (FD) or 2-deoxy-D-glucose (2-DG; 800 mg/kg) injections. NTX (1.0 and 10 mg/kg) had no effect on feeding, but markedly attenuated hamster drinking induced by 48 hr water deprivation or hypertonic saline injection. Dexamethasone (DEX), a glucocorticoid which depletes pituitary β-endorphin and produces anorexia in rats, had no effect on daily hamster intake. Since the normal feeding profile of the hamster is similar to that of naloxone and DEX-treated rats, hamsters appear to lack an opiate-sensitive feeding system. In contrast, stimulated drinking behavior of hamsters operates through an opiate-sensitive mechanism. Thus, there are marked species differences concerning the involvement of endogenous opioids is consummatory behavior.     

The Impact of Bacterial Diet on the Migration and Navigation of Caenorhabditis elegans

Can diet have a significant impact on the ability of organisms to sense and locate food? Focusing on the bacterial feeder Caenorhabditis elegans, we investigated what effect preconditioning on a range of bacterial substrates had on the subsequent chemotaxis process involved in the nematode locating other bacterial populations. Remarkably, we found that C. elegans, initially fed on a diet of Escherichia coli OP50, was significantly impaired in finding E. coli OP50 populations, compared to other available bacterial populations (P < 0.001). We found similar results for another bacterial feeding nematode species, suggesting that a general “substrate legacy” may operate across a wide range of organisms. We discuss this important finding with respect to the variation in response exhibited within a given nematode population, and the impact nematode migration has on bacterial dispersal in the environment.     

Short-term high-fat feeding induces a reversible net decrease in synaptic AMPA receptors in the hypothalamus

Dietary obesity compromises brain function, but the effects of high-fat food on synaptic transmission in hypothalamic networks, as well as their potential reversibility, are yet to be fully characterized. We investigated the impact of high-fat feeding on a hallmark of synaptic plasticity, i.e., the expression of glutamatergic α-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid receptors (AMPARs) that contain the subunits GluA1 and GluA2, in hypothalamic and cortical synaptoneurosomes of male rats. In the main experiment (experiment 1), three days, but not one day of high-fat diet (HFD) decreased the levels of AMPAR GluA1 and GluA2 subunits, as well as GluA1 phosphorylation at Ser845, in hypothalamus but not cortex. In experiment 2, we compared the effects of the three-day HFD with those a three-day HFD followed by four recovery days of normal chow. This experiment corroborated the suppressive effect of high-fat feeding on hypothalamic but not cortical AMPAR GluA1, GluA2, and GluA1 phosphorylation at Ser845, and indicated that the effects are reversed by normal-chow feeding. High-fat feeding generally increased energy intake, body weight, and serum concentrations of insulin, leptin, free fatty acids, and corticosterone; only the three-day HFD increased wakefulness assessed via video analysis. Results indicate a reversible down-regulation of hypothalamic glutamatergic synaptic strength in response to short-term high-fat feeding. Preceding the manifestation of obesity, this rapid change in glutamatergic neurotransmission may underlie counter-regulatory efforts to prevent excess body weight gain, and therefore, represent a new target of interventions to improve metabolic control.     

Reduced feeding during water deprivation depends on hydration of the gut

Removal of drinking water at the start of the dark period reduced food intake in freely feeding rats within 45 min. Both first and later meals were smaller during 7.5 h of water deprivation, but meal frequency did not change. Ingestion of a normal-sized meal (3 g) rapidly increased plasma tonicity when drinking water was withheld, but intravenous infusions of hypertonic NaCl causing similar increases in plasma tonicity did not reduce feeding. Feeding during 6 h of water deprivation was restored by slowly infusing the volume of water normally drunk into the stomach, jejunum, or cecum, but not in the vena cava or hepatic portal vein. The infusions did not alter water or electrolyte excretion or affect food intake in rats allowed to drink. We conclude that the inhibition of feeding seen during water deprivation is mediated by a sensor that is located in the gastrointestinal tract or perhaps in the mesenteric veins draining the gut, but not the hepatic portal vein or the liver. In the absence of drinking water, signals from this sensor provoke the early termination of a meal.     

An experimental study of the oxygen consumption,growth, and metabolism of the COD (Gadus Morhua L.)

The rate of oxygen consumption of cod in sea water at 12 °C containing MS222 (25 mg/l) can be expressed as: Q_o2 = 0.245 W^0,82(mg/h), where W is the lived weight of the fish (g). The maximum efficiency of conversion of assimilated food into growth was 24% during the feeding experiment. Digestion efficiencies were estimated at over 98% using fillets of plaice as food. The effect of increasing the rate of food intake was to increase liver weight and condition factor. The relative proportions of protein and lipid in the body did not change over the range of feeding levels used. The conversion efficiency had a maximum value at an intermediate feeding rate.     

Preferences and Food Quality of Fruit‐Feeding Butterflies in Kibale Forest,Uganda1

Many butterflies in tropical forests feed on fruits that have fallen to the forest floor. This substrate differs in many ways from floral nectar, and therefore fruit‐feeding butterflies are expected to possess adaptations for efficient foraging, choice, and ingestion of their food. Differences in food quality and in spatial and temporal availability are also likely to have led to life history evolution. Here we describe the sugar and nitrogen content of fruits that butterflies feed on in a tropical forest in Uganda, and measure the attractiveness of these fruits to the local butterfly fauna together with the role that decay plays in the attraction. These data are supplemented with feeding observations at fruit falls in the forest. Our results show that (1) fruits contain significant and variable concentrations of sugar and nitrogen, and constitute a nutritious food source for butterflies in tropical forests; (2) fruit‐feeding butterflies use cues from the fruits and fermentation products to locate their food; (3) different classes of fruit‐feeding butterflies may vary in their preferences for certain fruits, and differ in their ability to find preferred food; and (4) fruit choice is not strongly correlated with attractiveness or nutrient content. The results are discussed in the light of the evolution of food searching and life history strategies.