Physiology of feeding-preference patterns of female black blowflies (Phormia regina Meigen): Modification in responsiveness to salts subsequent to salt feeding

Behavioural experimentation on Phormia regina shows that females previously fed only sucrose, and thus in a state of yeast preference, will ingest single-salt-sucrose mixtures in volumes similar to that of 10% yeast (Rachman et al., 1982). In particular, females will ingest NaCl 0.1 M in 0.2 M sucrose in volumes not statistically different from 10% yeast. In the experiments reported here, groups of females were given ad libitum access to both 0.2 M sucrose and NaCl 0.1 M in 0.2 M sucrose from days 0–4 after eclosion. Potassium and sodium salts were added to 0.2 M sucrose over a spectrum of concentrations and presented to the flies on day 6. The flies rejected all single-salt-sucrose mixtures offered. Even when the pre-test sodium salt was changed to a potassium salt during days 0–4, the flies still rejected the single-salt-sucrose mixtures offered subsequently. However, when sodium and potassium salts were mixed together in 0.2 M sucrose, females ingested the solutions in amounts similar to 10% yeast. Several different concentrations of the double-salt-sucrose solutions were ingested in volumes not statistically different from 10% yeast. Results support the underlying hypothesis that activity in the salt-sensitive chemosensory neurones is involved in protein preference.     

Physiology of feeding-preference patterns of female black blowflies (Phormia regina Meigen): Alterations in responsiveness to salts

Electrophysiological recordings of tarsal and labellar contact chemosensilla in Phormia regina females demonstrate activation of sugar-, cation-, and possibly anion-sensitive cells in response to 10% yeast extract. Yeast extract is a proteinaceous food source that supports full egg development. Though some protein is required for egg maturation in Phormia, a blowfly not normally autogenous, purified proteins alone neither activate the chemosensilla nor promote egg development. In experiments reported here, groups of females were given ad lib access to either 0.2 M sucrose or 0.2 M sucrose and 10% yeast for four days after eclosion. The sucrose diet induced a ‘protein’ preference but no egg development. Potassium and sodium salts were added to 0.2 M sucrose and presented to the flies on day six. The volumes of salt-sucrose mixtures taken were greater than those of 0.2 M sucrose for flies raised on 0.2 M sucrose, though yeast was preferred over all but one salt solution. For sucrose-and-yeast-fed flies, volumes of 0.05 and 0.1 M salt mixtures consumed did not differ from 0.2 M sucrose; however, sucrose alone was favoured over more concentrated salt mixtures. All salt-sucrose mixtures tested were significantly more effective stimuli for sucrose-and-yeast-fed flies than yeast. It is suggested that varying sensitivity in the salt-sensitive contact chemosensilla plays a role in reported food preference shifts associated with reproduction.     

The effects of a phagostimulant and a deterrent on the microstructure of feeding byManduca sexta caterpillars

Caterpillars of the hawkmothManduca sexta Johan. (Lepidoptera: Sphingidae) were offered discs of agar containing one of a range of concentrations of sucrose or of quinine, and the microstructure of the resulting feeding behaviour was quantified. As sucrose concentration increased caterpillars ate more by increasing the rate of biting and the lengths of meals. Bite frequency increased, after a latency of seconds to minutes, over the entire range tested (0.005 M to 0.5 M) whereas meal length reached a maximum at 0.1 M. Larvae spent less time feeding on agar containing 1 mM quinine than on quinine-free agar. This was accomplished by a reduction in the size of meals; numbers of chewing bouts in meals were lower. No other feeding behaviours were affected. In addition there was no orderly relationship between quinine concentration and changes in feeding behaviours. These observations suggested that postingestive effects were important in decreasing feeding. This paper is dedicated to the memory of Vincent G. Dethier     

Insect satiety: sulfakinin localization and the effect of drosulfakinin on protein and carbohydrate ingestion in the blow fly, Phormia regina (Diptera: Calliphoridae)

Sulfakinins, which are satiety factors in invertebrates, have previously been shown to inhibit feeding in the German cockroach and desert locust. This study examines the occurrence of sulfakinin immunoreactivity and the role of sulfakinin as a feeding satiety factor in the black blow fly, Phormia regina. Specifically, this study examines the effect of sulfakinin on two of the blow fly's nutrient requirements (i.e., carbohydrates and proteins). We observed sulfakinin immunoreactive cells in the brains of both male and female flies. We found that drosulfakinin I (DrmSKI, FDDY[SO(3)H]GHMRFa) significantly inhibited carbohydrate feeding by 44% at the most effective dose (10 nmol) in female flies. Statistically, there was no significant effect on males; however, injections of 10 nmol DrmSKI reduced carbohydrate feeding by 34% compared to the sham. Drosulfakinin had no effect on protein feeding and no significant inhibition was detected in females or males. The results of this study lend further support to the idea that carbohydrate and protein feeding are regulated by separate control mechanisms, especially in Calliphoridae.     

Feeding history effects on feeding responses of Rhagoletis indifferens (Dipt., Tephritidae) to GF-120 and Nulure

Abstract:  Effects of feeding history on feeding responses of western cherry fruit fly, Rhagoletis indifferens Curran, to the commercial protein baits GF-120 and Nulure were determined in the laboratory. Flies were kept on 5% sucrose alone or yeast extract and sucrose (Y + S) for 3–7 or 14–16 days and exposed to 24-h-old GF-120 or Nulure drops on artificial leaves. Numbers and durations of feeding events on leaves and durations of non-feeding events were recorded over 1-h periods. Experiments were also conducted to determine effects of Y + S feeding sequences on responses to Nulure, of starvation after sucrose or Y + S feeding on responses to Nulure, and of feeding history on mortality after exposure to GF-120 and Nulure. Protein-deprived flies consistently fed more times on GF-120 and Nulure than protein-fed flies and fed longer. One day of exposure to Y + S or 16 h of starvation after exposure to sucrose caused greater feeding on Nulure than 7 days of exposure to Y + S or 16 h of starvation after exposure to Y + S. Durations of non-feeding events on leaves with sucrose or bait were similar in protein-deprived and -fed flies. Responses of 4- to 6-day-old flies kept on sucrose to 0- and 24-h-old GF-120 or Nulure were similar. More flies kept on sucrose were paralysed or dead at 6–32 h after exposure to GF-120 or Nulure with spinosad than flies kept on Y + S. Results show that complete or long periods of protein deprivation and starvation after sucrose feeding increased feeding responses to GF-120 and Nulure. The general lack of differences in durations of non-feeding events on leaves with sucrose or GF-120 or Nulure in protein-deprived and -fed flies suggests that most protein-deprived flies found baits through chance encounters following normal movement.     

Effects of sucrose concentrations and fly age on feeding responses and survival of female and male western cherry fruit flies, Rhagoletis indifferens

Abstract. The effects of single meals of different sucrose concentrations on feeding responses and survival of 8–24-h-old, 1–2-, 10–12- and 31–36-day-old female and male western cherry fruit flies, Rhagoletis indifferens Curran, were determined. Feeding time and food consumption response patterns in both sexes within age groups were curvilinear. Feeding times increased as sucrose concentrations increased, and were longest when the sucrose concentration was 100% (dry). Consumption of dilute wet sucrose was low, whereas consumption of concentrated wet sucrose was high. However, consumption of dry, 100% sucrose was also low. One to 2-day-old flies of both sexes that had not previously fed consumed more sucrose foods than unfed 8–24-h-old flies and 10–12- and 31–36-day-old flies that had been starved for 16–24 h. Females consumed more than males, but they consumed the same amount as males per mg bodyweight. When fed single 20% and 60% sucrose meals, 1–2-day-old flies survived longer compared to flies in all other age groups, with 31–36-day-old flies surviving shortest. Despite age-related differences in survival, in general, no sex differences in survival were seen in flies fed sucrose within any age groups, or in flies fed sucrose-yeast, cherry juice and honeydew foods. The results suggest that sugar-feeding behaviours and the energy invested in sugar 'seeking' by both sexes of R. indifferens should be the same throughout life.     

Taste responses of Drosophila melanogaster

The amounts of sugar solution consumed by Drosophila melanogaster flies were determined. Starved and desiccated flies of a wild type strain (QA) consume 7?9 × 10^?2 λ of a 0.3 M sucrose solution per fly during the first hour and less later. They consume more of the 0.3 M sucrose solution than of the more diluted and the more concentrated solutions. In preference-aversion tests the flies discriminated between water and various sugar solutions, and between different sugar concentrations. Contrary to other fly species these flies did not prefer 0.05 M fructose over 0.05 M glucose. 0.3–0.5 M NaCl added to 0.1 M sucrose turned a preference over 0.01 sucrose into an aversion. A mutant, Lot-94, selected for its increased consumption of a 1 M NaCl solution was found to consume more of all test solutions. The amount of NaCl that had to be added to 0.1 M sucrose to turn the preference over 0.01 M sucrose by the mutant flies into aversion was not different from that found for the wild type flies.     

Comparing longevity of Pseudacteon species of different sizes: effect of sugar feeding

Sugar feeding is known to enhance lifespan in many parasitoid species. Several species of phorid flies in the genus Pseudacteon (Diptera: Phoridae) have been introduced in the Southern U.S.A. for the biological control of imported fire ants of Solenopsis species (Hymenoptera: Formicidae). Pseudacteon species are short‐lived flies and little is known about their nutritional ecology. Results from previous studies in our laboratory show that one of the introduced species, Pseudacteon tricuspis Borgmeier, is capable of feeding on sugar sources with a significant increase in lifespan. However, in Pseudacteon phorid flies, the degree to which sugar feeding can enhance the lifespan of other species is not clear, nor is it known whether there is a relationship between body size and longevity. In the present study, the effect of sugar feeding on the survival of three phorid fly species of different body sizes, Pseudacteon cultellatus Borgmeier, Pseudacteon curvatus Borgmeier and Pseudacteon obtusus Borgmeier, is investigated. For all three species, flies continuously provided with 40% or 20% sucrose solution live longer than individuals provided water only or 40% sucrose solution only on the first day of adult life. However, the degree to which sugar feeding enhanced longevity varies by species and is highest for P. obtusus. The data also indicate that longevity in Pseudacteon phorid flies is related to body size: the largest species (P. obtusus) lives significantly longer than the smaller species (P. cultellatus and P. curvatus). These results suggest that adults of all three Pseudacteon species are capable of feeding on sucrose solution and that sugar feeding can enhance their longevity. The significance of these results is discussed in relation to the field performance of Pseudacteon phorid flies as biological control agents of imported fire ants.     

Consumption of sugars by Anastrepha suspensa (Diptera: Tephritidae)

We were interested in determining the feeding response of the Caribbean fruit fly, Anastrepha suspensa Loew (Diptera: Tephritidae), to various sugar concentrations to develop an improved bait for adults. We compared the consumption of 0.01-1.00 M concentrations of glucose, fructose, raffinose, and sucrose in no-choice tests for 24-h- and 6-d-old male and female flies. Sucrose was the most consumed sugar or within the most consumed group of sugars at 0.02-0.20 M concentrations. There were no differences in consumption among sugars at 0.01, 0.40, and 1.00 M. Consumption generally increased with increasing sugar concentration except that sucrose consumption peaked at 0.20 M. Twenty-four-hour females consumed less fructose than other sugars; 24-h males consumed more sucrose than fructose or raffinose, with an intermediate response to glucose. Females in the 6-d group consumed more sucrose than the other three sugars, whereas 6-d males exhibited no difference in consumption among sugars. In choice tests, flies consumed more sugar solution than water, but the difference between 0.20 M fructose and water was not significant for 24-h males or 24-h females. In choice tests between 0.20 M fructose and 0.20 M sucrose, both 24-h and 6-d females showed a preference for fructose. Males of both age classes showed no preference. These results indicate that the responses of flies to different sugars can vary by sugar, gender, and age.     

Protein: carbohydrate ratios promoting sexual activity and longevity of male Queensland fruit flies

Nutrition is commonly a powerful determinant of sexual performance in insects, and recent studies have found this to be the case in Queensland fruit flies (Tephritidae: Bactrocera tryoni Froggatt; 'Q-flies'); male Q-flies allowed to self-regulate intake of yeast hydrolysate, a rich source of amino acids and vitamins used in most mass-rearing programmes (protein) and sucrose (carbohydrate), had greatly enhanced sexual performance compared with males provided only sucrose. While some yeast hydrolysate is clearly beneficial for the sexual performance of adult male Q-flies, the questions of what proportion of yeast hydrolysate in the diet is sufficient to yield full benefits, or is too much, have not yet been addressed. To address these questions, the present study assessed sexual performance and longevity of adult male Q-flies maintained on diets containing various proportions of yeast hydrolysate and sucrose. Male Q-flies maintained as adults on dry mixtures containing 9%, 17% or 25% yeast hydrolysate had mating probability, mating latency, copula duration and longevity similar to those provided yeast hydrolysate and sucrose in separate dishes and allowed to self-regulate intake. As in previous studies, while longevity was unaffected we found a marked reduction in sexual performance when the flies were completely denied access to yeast hydrolysate, and the few that did mate had relatively short copulations. At the other extreme, flies receiving diets with high levels of yeast hydrolysate (50%, 75%, 83% and 91%) suffered marked reductions both in longevity and in mating performance.     

Activity of female blowflies, (Phormia regina), in response to novel odours

Female blowflies (Phormia regina Meigen) which had been fed either sucrose (S flies) or sucrose and yeast (SY flies) were tested for their response to novel odours in an actograph. All responded with an increase in activity. S flies were consistently more responsive than SY flies both in their increase in activity and in the number of different odours to which they responded significantly. S flies found food rapidly over a short distance when they were made active either by a stimulating odour or by mechanical agitation. Olfaction, rather than vision, was demonstrated to be the sense mediating the increase in activity.

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Résumé Des effluves de banane, pomme, foie de buf et levure ont été testées en actographe contenant 20 femelles de Phormia regina de 2 à 9 jours. Ces mouches avaient été nourries antérieurement, soit sur sucrose seul à 0,1M (mouches S), soit sur sucrose (0,1M) et 10% de levure (mouches SY). L'activité des mouches croît quand les odeurs sont introduites, mais il en est de même quand le courant d'air pur est changé.L'augmentation de l'activité provoquée par la banane, la pomme, et la levure est significativement supérieure pour les mouches S, à celle provoquée par le changement du courant d'air (Fig. 1). Chez les mouches SY l'augmentation significative est observée avec la banane et la levure (Fig. 2). Les mouches S sont plus actives et répondent mieux que les mouches SY: Une goutte de levure dans un récipient avec des mouches S de 6 jours stimule leur activité et la goutte est trouvée rapidement (16 sec.). Des gouttes d'eau ou de sucrose ne stimulent pas l'activité, et les mouches mettent beaucoup plus long-temps pour les trouver (> 100 sec.). En secouant les récipients pour rendre les mouches actives on obtient une découverte des gouttes d'eau ou de sucrose aussi rapide que la découverte des gouttes de levures par les mouches non perturbées. Des mouches antennotectomisées, non perturbées, mettent 252 sec. pour trouver une goutte de levure, mais des mouches antennotectomisées et agitées artificiellement trouvent les gouttes presqu'aussi rapidement que les mouches normales non perturbées (Fig. 3).

     

Effect of different carbohydrate drinks on whole body carbohydrate storage after exhaustive exercise.

Seven untrained male subjects participated in a double-blind, crossover study conducted to determine the efficacy of different carbohydrate drinks in promoting carbohydrate storage in the whole body and skeletal muscle during recovery from exhaustive exercise. The postabsorptive subjects first completed an exercise protocol designed to deplete muscle fibers of glycogen, then consumed 330 ml of one of three carbohydrate drinks (18.5% glucose polymer, 18.5% sucrose, or 12% sucrose; wt/vol) and also received a primed constant infusion of [1-(13)C]glucose for 2 h. Nonoxidative glucose disposal (3.51 +/- 0.28, 18.5% glucose polymer; 2.96 +/- 0.32, 18.5% sucrose; 2.97 +/- 0.16, 12% sucrose; all mmol. kg(-1). h(-1)) and storage of muscle glycogen (5.31 +/- 1.11, 18.5% glucose polymer; 4.07 +/- 1.05, 18.5% sucrose; 3.45 +/- 0.85, 12% sucrose; all mmol. kg wet wt(-1). h(-1); P < 0.05) were greater after consumption of the glucose polymer drink than after either sucrose drink. The results suggest that the consumption of a glucose polymer drink (containing 61 g carbohydrate) promotes a more rapid storage of carbohydrate in the whole body, skeletal muscle in particular, than an isoenergetic sucrose drink.     

Food deprivation effects on carbohydrate levels and their relation to feeding responses of western cherry fruit fly Rhagoletis indifferens to spinosad bait

Abstract The nutritional state of tephritid fruit flies affects various behaviours. The present study aims to determine food deprivation effects on carbohydrate levels and their relation to feeding responses to spinosad bait (GF‐120^® Naturalyte^® Fruit Fly Bait; Dow AgroSciences, Indianapolis, Indiana), as measured indirectly by mortality, in western cherry fruit fly Rhagoletis indifferens Curran (Diptera: Tephritidae). Sugar levels in 1–2‐day‐old flies exposed to sugar for 1 h and then deprived of sugar for 10–24 h decrease but, in flies with access to continuous sugar and no sugar, they increase and do not change, respectively. Sugar levels in 14–15‐day‐old flies that have had free access to yeast extract and sugar and are then deprived of it for 0 and 10 h do not differ but they are lower at 24 and 30 h. Mortalities of 1–2‐day‐old flies exposed to sugar for 1 h and then deprived of it for 0–24 h progressively increase but they do not increase in flies given no sugar because the mortalities in this treatment are equally high at all times. By contrast, mortalities of 14–15‐day‐old flies deprived of food increase from 0 to 10–30 h but there are no differences from 10 to 30 h. Mortalities of 14–15‐day‐old flies deprived of food for 3 and 6 h also do not differ. Food deprivation effects on glycogen are similar, although glycogen occurs at lower levels than sugar. The results obtained suggest that R. indifferens flies need to feed multiple times on carbohydrate foods during the day to maintain their carbohydrate levels, that their responses to spinosad bait will increase if they do not, and that there may be age‐related effects on carbohydrate levels and responses to spinosad bait.     

OXIDIZED LIPIDS DID NOT REDUCE LIFESPAN IN THE FRUIT FLY,Drosophila melanogaster

Aging is often associated with accumulation of oxidative damage in proteins and lipids. However, some studies do not support this view, raising the question of whether high levels of oxidative damage are associated with lifespan. In the current investigation, Drosophila melanogaster flies were kept on diets with 2 or 10% of either glucose or fructose. The lifespan, fecundity, and feeding as well as amounts of protein carbonyls (PC) and lipid peroxides (LOOH), activities of superoxide dismutase (SOD), catalase, glutathione‐S‐transferase (GST), and glutathione reductase activity of thioredoxin reductase (TrxR) were measured in “young” (10‐day old) and “aged” (50‐day old) flies. Flies maintained on diets with 10% carbohydrate lived longer than those on the 2% diets. However, neither lifespan nor fecundity was affected by the type of carbohydrate. The amount of PC was unaffected by diet and age, whereas flies fed on diets with 10% carbohydrate had about fivefold higher amounts of LOOH compared to flies maintained on the 2% carbohydrate diets. Catalase activity was significantly lower in flies fed on diets with 10% carbohydrates compared to flies on 2% carbohydrate diets. The activities of SOD, GST, and TrxR were not affected by the diet or age of the flies. The higher levels of LOOH in flies maintained on 10% carbohydrate did not reduce their lifespan, from which we infer that oxidative damage to only one class of biomolecules, particularly lipids, is not sufficient to influence lifespan.     

Lifespan and patterns of accumulation and mobilization of nutrients in the sugar-fed phorid fly, Pseudacteon tricuspis

Abstract. The effect of sugar feeding on the survival of adult phorid fly Pseudacteon tricuspis is investigated. Flies fed 25% sucrose in aqueous solution continuously throughout their lifespan have greater longevity (mean ± SE longevity: female = 7.9 ± 0.8 days, male = 8.9 ± 0.9 days) than completely starved (provided no water and no sugar solution) flies, sugar-starved (provided water only) flies, or flies fed sugar solution only on their first day of adult life. Completely starved flies rarely lived beyond one day. Provision of water increases longevity by 2 days, and one full day of sugar feeding further increases longevity by an additional 1–2 days. Flies fed 50% sucrose have similar survivorship as those fed 25% sucrose. The temporal patterns of nutrient accumulation and utilization are also compared in P. tricuspis fed different diets: sugar-starved, sucrose-fed on the first day of adult life only, and sucrose-fed continuously. Adult P. tricuspis emerge with no gut sugars, and only minimal amounts of body sugars and glycogen. Although the levels of body sugars and glycogen decline gradually in sugar-starved flies, a single day of sugar feeding results in the accumulation of maximum amounts of gut sugars, body sugars and glycogen. High levels of these nutrients are maintained in female and male phorid flies fed on sucrose continuously over the observation period, whereas nutrient levels decline in flies fed only on the first day of life, beginning 1 day postfeeding. Female and male P. tricuspis emerge with an estimated 12.3 ± 2.3 and 7.2 ± 1 g of lipid reserves per fly, respectively. These teneral amounts represent the highest lipid levels detected in adult flies, irrespective of their diet, and are maintained over the life times of sucrose-fed female and male flies, but declined steadily in sugar-starved females. These data suggest that adult P. tricuspis are capable of converting dietary sucrose to body sugars and glycogen, but not lipids.     

Feeding behavior of Ceratitis capitata (Diptera,Tephritidae): influence of carbohydrate ingestion

Experiments were conducted on Ceratitis capitata larvae and adults to determine the influence of sugar (glucose and sucrose) ingestion on some aspects of the feeding behavior of this species. The results indicate that larval choice of a diet containing glucose or sucrose is not influenced by the rearing diet, by carbohydrate deprivation or by previous experience (induction). Carbohydrate deprivation did not alter the discrimination threshold of the larvae for sucrose. In adult females, the discrimination threshold for sucrose was unchanged when the flies were submitted to carbohydrate deprivation during the adult phase although ingestion by deprived females was 35% higher than ingestion by the control group. However, adults submitted to carbohydrate deprivation during the larval phase suffered a profound reduction in discrimination threshold for sucrose.     

Long Term Feeding Patterns Highlight Preference for Sucrose in the Fruit Fly <Emphasis Type="Italic">Anastrepha serpentina</Emphasis> When Given a Choice over Other More Nutritious Food Sources

Insects are known to be able to regulate food ingestion according to its nutrient composition rather than its energetic content. Several studies have found that individuals can feed selectively when given the opportunity, and balance the intake of different nutrients so as to optimize fitness. However, there are cases in which individuals do not strictly adopt this pattern of optimal nutrient balancing. This study examined the periodicity of feeding on different food substrates and also water by adult individuals of Anastrepha serpentina (Wiedemann) (Diptera: Tephritidae) over a 38-day observation period analyzing daily feeding patterns, feeding time, and sequences of feeding events. Two artificial food substrates, one rich in protein (hydrolyzed yeast) and one rich in carbohydrates (sucrose), and one natural diet (open sapodilla fruit) were offered alone or paired (sucrose vs. open fruit or sucrose vs. yeast) to newly emerged individuals during 38 days or until death. Water was also provided in all cases. Our results provide new and interesting insights on long-term individual dietary preferences and feeding periodicity in a tropical fruit fly, including water consumption. In general, flies exhibited different feeding patterns according to the diet, but preferred to feed on sucrose when offered a choice of sucrose and yeast. This preference was evident from the outset of the trial. When sucrose was offered together with an open fruit, the latter was preferred. However, there were conspicuous individual differences in temporal feeding patterns among flies fed the same diet, including variability in the number of consecutive days some individuals did not consume any food or water (up to five days in some cases). Individuals fed with sucrose only exhibited the lowest survival and those fed with sucrose-open fruit the highest. We discuss these feeding choices and their possible causes, including individual differences in the gut microbiota and nutritional reserves of newly emerged flies.     

Long-term regulation of sucrose intake by the adult Mediterranean fruit fly, Ceratitis capitata (Wiedemann)

Male and female medflies, Ceratitis capitata, were maintained for up to 8 days after emergence on 2% (58 mM), 8% (234 mM), or 16% (468 mM) sucrose solutions. Sucrose intake was recorded daily and whole-body analyses of lipid and glycogen were made at regular intervals.Greater volumes of fluid were imbibed by all flies on more dilute solutions. However, the amount of sucrose taken up over time was greatest for males on the 16% diet. Female intake was equal on the 8 and 16% diets.Males lost body triacylglycerol at a rate proportional to the dilution of the diet. Females on 8 and 16% sucrose lost no triacylglycerol throughout the 8-day period. Males and females, starved for 2 days after emergence lost 80% of their triacylglycerol and did not resume triacylglycerol synthesis when offered a diet rich in sucrose.     

Labellar lobe spreading in the blowfly: Regulation by taste and satiety

Summary Lobe spreading behavior was studied by recording electromyograms from the muscles which spread the labellar lobes, the retractors of the furca (RF) inPhormia regina. RF responses and lobe spreading could be elicited by stimulating labellar, but not tarsal, taste hairs with sucrose (Fig. 3). RF activity was important to spread the lobes at the beginning of a meal, but was not necessary for continued feeding (Fig. 4).Temporal summation between sugar receptor spikes was necessary to elicit RF responses. Central response decrement occurs independently for different labellar hairs and may participate in the termination of motor responses.RF responses were more probable and more intense when either the sucrose concentration of the stimulus or the number of hairs stimulated was increased (Fig. 7). Stimulation with NaCl had no effect on the response to simultaneous sucrose stimulation of other hairs (Table 1).Feeding caused decreases in the probability and intensity of motor responses, but did not alter chemosensory responses (Figs. 8 and 9). Section of either the recurrent or median abdominal nerves prevented this postingestional inhibition of lobe spreading (Fig. 9).These results are discussed with regard to the possible role that regulation of lobe spreading may play in the control of food intake.This work was supported by United States Public Health Service Training Grant 5T01 GM 00457-13S2 and by a grant from the National Science Foundation to Dr. Vincent G. Dethier. I wish to thank Dr. Dethier for his support and encouragement.     

Central control of feeding in the diapausing adult blowfly Phormia regina.

1. The tarsal acceptance threshold of non-diapausing adult blowflies rises with age. 2. Diapausing flies have a non-significantly elevated tarsal acceptance threshold, but drink significantly less sucrose solution than their non-diapausing counterparts. 3. Removal of diapausing flies to non-diapause inducing conditions resulted in a lowering of the threshold. 4. Failure to demonstrate a significant difference between the input signal from the peripheral receptors of non-diapausing and diapausing flies showed that the inhibition of feeding in diapausing flies was not due to peripheral inhibition but was controlled centrally.