The interaction of external and internal receptors on the feeding behaviour of the blowfly, Phormia regina

The interaction of sensory activity from internal gut stretch receptors and from external labellar chemosensory hairs has been studied both behaviourally and electrophysiologically in the control of proboscis extension of the blowfly, Phormia regina. Labellar thresholds for proboscis extension, tested behaviourally, do not change significantly up to an hour after feeding in contrast to tarsal thresholds which rise quickly after feeding. Motor activity of the extensor muscle of the haustellum was recorded simultaneously with sensory activity from labellar sensilla. The mean number of muscle spikes per response and the sensory input necessary to trigger a response do not vary with starvation, feeding, or sectioning of the recurrent nerve. Activity of internal stretch receptors seem to interact with tarsal sensory input but apparently do not modulate motor responses triggered by labellar sensory input.     

Effects of substituted phenylethylamines on blowfly feeding behavior

The pharmacology of adult Phormia regina (Meigen) feeding behavior was explored by injecting candidate drugs into starved blowflies and then determining their responsiveness to aqueous sucrose, via the proboscis extension reflex. d-Amphetamine caused responsiveness to fall dramatically, while related drugs and biogenic amines had varying effects. When d-amphetamine-treated flies were fed 1 M sucrose, they consumed significantly more than control flies. Electrophysiological studies demonstrated that the responses of tarsal sugar receptor neurons to aqueous sucrose were not significantly altered by d-amphetamine. These observations are compatible with our hypothesis that octopamine positively modulates blowfly feeding behavior and suggest that other aromatic biogenic amines affect feeding behavior in this insect.     

Circadian rhythm of proboscis extension responsiveness in the blowfly: central control of threshold changes

ABSTRACT. The proboscis extension response of the blowfly, Protophormia terraenovae (R.-D.), elicited by stimulation of the tarsi with sucrose, was studied behaviourally under LD 12:12. A diel rhythm in responsiveness was found that occurred at successively higher daily mean levels as the test flies became increasingly starved. This rhythm persisted for at least one cycle in constant light, demonstrating it to be truly endogenous and circadian. The tarsal chemo-receptors concerned in initiating the response were examined electrophysiologically in whole fly preparations. No daily change occurred in the response of these receptors to sucrose. Hence central control of the behavioural rhythm of response to sucrose is inferred, and a model is proposed which incorporates a circadian oscillator into the currently accepted model for the control of proboscis extension thresholds.     

Behavioral studies on tarsal gustation in honeybees: sucrose responsiveness and sucrose-mediated olfactory conditioning

Although the forelegs of honeybees are one of their main gustatory appendages, tarsal gustation in bees has never been systematically studied. To provide a more extensive account on honeybee tarsal gustation, we performed a series of behavioral experiments aimed at characterizing (1) tarsal sucrose sensitivity under different experimental conditions and (2) the capacity of tarsal sucrose stimulation to support olfactory conditioning. We quantified the proboscis extension reflex to tarsal sucrose stimulation and to odors paired with tarsal sucrose stimulation, respectively. Our experiments show that tarsal sucrose sensitivity is lower than antennal sucrose sensitivity and can be increased by starvation time. In contrast, antennae amputation decreases tarsal sucrose sensitivity. Furthermore, we show that tarsal sucrose stimulation can support olfactory learning and memory even if the acquisition level reached is relatively low (40%).     

The sensitivity of the labellar sugar receptors of Phormia regina in relation to feeding

The hypothesis that behavioural feeding threshold of P. regina modulates and is modulated by the sensitivity of the labellar contact chemoreceptors is not supported by the examination of individual flies.Sensitivity (number of impulses fired in the first second of stimulation) of the sugar receptors in selected labellar hairs of flies of known age was recorded periodically on a fixed schedule for up to 72 hr. Experimental flies were hand fed 2.0 M fructose once every 24 hr. No correlations between feeding or age and receptor sensitivity were found. Statistically significant changes in firing frequency did occur but were unrelated to feeding and age.The proboscis extension response, on which behavioural threshold measures are based, is known to be triggered by the first few sugar receptor spikes of sufficient frequency. Neither age nor feeding significantly affected the number or frequency of impulses during the first 50 msec of stimulation.     

Effects of age and blood sugar levels on the proboscis extension of the blow fly Phormia regina

In some insects the proboscis is extended to imbibe a sugar solution if the concentration of sugar applied to the chemosensilla exceeds the behavioural threshold value. Recently, I found a reversal of the threshold values of this "proboscis extension reflex" (PER) in the blow fly (Phormia regina M.) for glucose and fructose. It depended on maturation and physiological conditions, both of which are explicable in terms of changing concentration of haemolymph trehalose. The direct injection of trehalose into the fly haemocoele brought about a dramatic shift of the threshold values of PER measured on tarsi or labellar sensilla, suggesting a strong dependence of PER on the blood sugar level. Using the tip-recording method, the dose-response (impulse frequency) curves for glucose and fructose were obtained on individual largest labellar chemosensilla. The curves for glucose and fructose crossed at one point because the former had a steeper gradient and higher maximum response than the latter. Injection experiments with trehalose were also carried out to test for changes in gustatory response. The shifting of the behavioural dose-response curves for glucose and fructose two hours after injection of 1 M trehalose (2 μl) into the haemocoele of the fly was associated with significant reduction in responsiveness of labellar chemosensilla to glucose, but less so to fructose. No change in responsiveness was found following injection of mannose. A hypothesis to explain the reversal relation of the PER thresholds, based on a shift in the firing rate in gustatory sensilla and possibly also interneurons, is discussed.     

Responsiveness to sucrose and habituation of the proboscis extension response in honey bees

In honey bees, complex behaviours such as associative learning correlate with responsiveness to sucrose. In these behaviours, the subjective evaluation of a sucrose stimulus influences the behavioural performance. Habituation is a well-known form of non-associative learning. In bees, the proboscis extension response can be habituated by repeatedly stimulating the antennae with a low sucrose concentration. A high sucrose concentration can dishabituate the response. This study tests whether habituation correlates with responsiveness to sucrose in bees of different behavioural states and in bees which are habituated with different sucrose concentrations. Habituation and dishabituation in newly emerged bees, 5-day-old bees and foragers strongly correlated with responsiveness to sucrose. Bees with high responsiveness to sucrose displayed a lower degree of habituation and showed greater dishabituation than bees with low responsiveness. The degree of habituation and dishabituation also depended on the concentration of the habituation stimulus. These experiments demonstrate for the first time in a non-associative learning paradigm that the subjective strength of a sucrose stimulus determines the behavioural performance. Non-associative learning shares this property with associative learning, which suggests that the two processes might rely on similar neural mechanisms.Abbreviations: GRS Gustatory response score - PER Proboscis extension response     

Effect of pheromones,hormones, and handling on sucrose response thresholds of honey bees (Apis mellifera L.)

The responsiveness of bees to sucrose is an important indicator of honey bee foraging decisions. Correlated with sucrose responsiveness is forage choice behavior, age of first foraging, and conditioned learning response. Pheromones and hormones are significant components in social insect systems associated with the regulation of colony-level and individual foraging behavior. Bees were treated to different exposure regimes of queen and brood pheromones and their sucrose responsiveness measured. Bees reared with queen or brood pheromone were less responsive than controls. Our results suggest responsiveness to sucrose is a physiologically, neuronally mediated response. Orally administered octopamine significantly reduced sucrose response thresholds. Change in response to octopamine was on a time scale of minutes. The greatest separation between octopamine treated and control bees occurred 30 min after feeding. There was no significant sucrose response difference to doses ranging from 0.2 g to 20 g of octopamine. Topically applied methoprene significantly increased sucrose responsiveness. Handling method significantly affected sucrose responsiveness. Bees that were anesthetized by chilling or CO₂ treatment were significantly more responsive than control bees 30 min after handling. Sixty minutes after handling there were no significant treatment differences. We concluded that putative stress effects of handling were blocked by anesthetic.Abbreviations BP brood pheromone - JH juvenile hormone - OA octopamine - PER proboscis extension response - PER-RT proboscis extension response threshold - QMP queen mandibular pheromone     

Effects of alkaloids on feeding by Phormia reginaconfirm the critical role of sensory inhibition

Abstract. Inhibition of peripheral chemoreceptors by micromolar concentrations of alkaloids may account for feeding deterrence. Earlier work showed a reduction in both the proboscis extension response and sensory activity recorded from sugar-sensitive cells in tarsal D and labellar 'largest' hairs when the stimulating solution was sucrose mixed with alkaloids. In the present work a similar behavioural effect was also seen when alkaloids were mixed with pyranose and furanose sugars as well as with water and deuterium oxide. Behavioural deterrence continued after the stimulus was removed. Complete recovery occurred after 120 s. To check against the possibility of a central inhibitory state (CIS) having been established two sets of experiments were run in which quinine was applied to a single tarsus followed by a sucrose post-test to the contralateral tarsus. In one half of the tests sugar was applied first (S₁Q₂), and in the other half quinine first (Q₁S₂). Comparable tests were run with contralateral labellar hairs. No CIS was set up by Q₁; however, a central excitatory state (CES) was set up by S₁. In order to test (a) whether quinine had different effects on other known or unknown receptors and (b) post-ingestive effects, volumes imbibed in single drinks of sucrose with and without quinine were compared. Volumes of the mixture imbibed were not significantly different from what was predicted based on the known reduction in sensory acitivty.     

Divergent behavioral and electrophysiological taste responses in the mid-legs of adult butterflies, Vanessa indica and Argyreus hyperbius

Adult nymphalid butterflies possess sensilla trichodea (ST) that perceive taste in their walking legs. We examined whether the gustatory responses to mid-leg tarsal stimulation were different between Vanessa indica (rotting-food feeder) and Argyreus hyperbius (flower-nectar feeder). Sucrose, fructose, and glucose elicited behavioral responses (proboscis extension reflex: PER) and electrophysiological responses (spikes) from ST. Sugar responsiveness was similar in both species, where sucrose was the most stimulatory. Two fermentation products, ethanol and acetic acid, never induced PERs but elicited large-amplitude spikes at a concentration of >1% (w/v). The two species significantly differed in responsiveness to the binary mixtures of sucrose and the fermentation products. Ethanol enhanced the sugar responses of V. indica but slightly inhibited those of A. hyperbius. Although acetic acid suppressed the sugar responses of both species, V. indica was less susceptible than A. hyperbius. When concentration of the fermentation products increased, binary mixtures evoked large spikes together with small ones regarded as the sucrose responses. Unlike the proboscal sensilla in our previous study, the tarsal ST of both species unambiguously responded to fermentation products. These results demonstrate that the tarsal gustatory sense of V. indica is adaptive to the use of rotting foods.     

Major components in the hairpencil secretion of a butterfly, Euploea mulciber (Lepidoptera, Danaidae): their origins and male behavioral responses to pyrrolizidine alkaloids

Two compounds, 9,10-epoxytetrahydroedulan (ET) and viridiflorine beta-lactone (VL), were identified as major components from the hairpencils of field-caught males of a danaid butterfly, Euploea mulciber. By contrast, laboratory-reared males entirely lacked VL, but possessed a significant quantity of ET. Various feeding experiments with larvae and indoor adult males strongly suggested that ET is biosynthesized de novo only after eclosion from nutrients ingested during the larval development. Since VL was suspected to be derived from pyrrolizidine alkaloids (PAs) acquired as an adult, tests for feeding response to and oral administration of four PAs (a 4:1 mixture of intermedine/lycopsamine, heliotrine, monocrotaline, and retronecine) were conducted. When the tarsi or proboscis were stimulated with PA solutions, males showed positive feeding responses (proboscis extension and sucking movements) to intermedine/lycopsamine, heliotrine, and retronecine in decreasing order of responsiveness, thereby providing evidence that male adults are endowed with taste receptor(s) specific to PAs on the legs as well as on the proboscis. Differently from gustatory responsiveness, only males fed with intermedine/lycopsamine produced a significant quantity of VL (ca. 35 microg/male), whereas those that ingested heliotrine or monocrotaline hydrochloride produced traces of VL (<0.18 microg/male). Uptake of retronecine did not lead to VL formation at all. In behavioral bioassays to test the attractivity of PAs to males, all individuals tested were attracted exclusively to intermedine/lycopsamine. This shows that certain PA(s) per se serve as attractant(s) for males in locating PA sources, and further suggests that in the field, males will seek particular PA(s) that are indispensable as precursors for the efficient biosynthesis of VL.     

Optical releasers of the innate proboscis extension in the hoverfly Eristalis tenax L. (Syrphidae,Diptera)

Freshly emerged, inexperienced imagos of the hoverfly Eristalis tenax L. extend their proboscis towards small, yellow colour stimuli, such as anther parts and artificial floral guides. The releasing of this behaviour, which is adapted to pollen feeding, was investigated in behavioural tests using white, UV-reflecting artificial flowers with four small screens illuminated with test stimuli serving as artificial floral guides. The releasing of the innate proboscis extension was tested using monochromatic test lights. Within an intensity range from approx. 5·10¹¹ to approx. 10¹⁴ quanta · cm^-2· s^-1, the flies extended their proboscis only towards green and yellow test lights (approx. 520–600 nm). The inhibition of the innate proboscis extension was tested using mixed light stimuli composed of a yellow monochromatic reference light (560 nm, 10¹³ quanta·cm^{-2 -1}) and of a monochromatic test light. When the reference light was mixed with ultraviolet or blue test lights, the releasing of the innate proboscis extension was strongly inhibited, whereas admixing green/yellow light slightly promoted it; admixing red light had no effect. The results indicate that the releasing of the innate proboscis extension is mediated by the photoreceptor type R8y. Other receptor types which could cause the inhibition of the proboscis reaction are discussed.     

Clonidine effects on protein and carbohydrate electrophysiological responses of labellar and tarsal sensilla in Phormia regina

The electrophysiological response of labellar and tarsal chemosensilla in the blowfly Phormia regina was studied in response to a complex stimulus naturally encountered by flies such as sheep faeces, and to beef liver, a proteinaceous feeding source. Responses were investigated both before or after injection of clonidine, an octopamine agonist previously shown to enhance sucrose ingestion, while decreasing that of proteins. As assessed by single sensillum recordings, the four different chemosensory - "salt", "sugar", "deterrent" and "water" - cells were all activated by both stimuli, regardless of sex and sensillum type, the "sugar" one being in all cases the most sensitive to beef liver before clonidine injection. Clonidine treatment affected neither labellar nor tarsal sensitivity to sucrose. Conversely, clonidine-injected flies showed a significant increase in the activity of the "deterrent" cell to beef liver, thus accounting for a decrease in protein ingestion. This study for the first time provides evidence of a key role of a clonidine-sensitive peripheral taste sensitivity in down-regulation of protein ingestion in blowflies. Correlation between peripheral sensitivity and behavioural output is discussed.     

Amphetamine and Reserpine Deplete Brain Biogenic Amines and Alter Blow Fly Feeding Behavior

HPLC with electrochemical detection was used to determine the levels of p-hydroxyphenylethanolamine (octopamine), 3,4-dihydroxyphenylethylamine (dopamine), and 5-hydroxytryptamine (5-HT) in the brains of control, reserpine, and d-amphetamine-treated blow flies, Phormia regina Meigen. Parallel studies were carried out to assess the effects of the two drugs on fly feeding behavior, measured as mean acceptance threshold: the minimum sucrose concentration to which the average fly in a population will respond by proboscis extension when its tarsi contact the solution. In saline-injected control flies, all three amines were found at levels of approximately 2 pmol/brain. Thirty minutes after injection with d-amphetamine (12 micrograms/fly), brain octopamine was depleted by 85%, whereas dopamine and 5-HT were depleted by 70%. Reserpine (5 micrograms/fly) caused 70% depletion of dopamine and greater than 90% depletion of both octopamine and 5-HT 24 h after injection. However, the effect of reserpine was much slower in onset (hours versus minutes) and more persistent (days versus hours) than was the effect of d-amphetamine. With either drug, the time course of amine depletion closely matched the time course of the increase in feeding threshold observed in drug-treated flies. These results suggest that CNS pools of the biogenic amines, octopamine, dopamine, and 5-HT are important in governing blow fly responsiveness to food stimuli.     

Conditional suppression of a reflex in Drosophila melanogaster: acquisition and extinction]

In Drosophila it was possible to carry out a negative instrumental conditioning of the tarsal reflex (extension of the proboscis in response to a sucrose stimulation of the forelegs) : the insects could be trained to inhibit this reaction through a repetitive association of its releasing with a consecutive nociceptive stimulation. An experimental extinction procedure allowed the reflex to be resoted.     

亚致死剂量杀虫剂对意蜂工蜂嗅觉敏感性的影响

喙伸反应(PER)试验适用于评价杀虫剂对蜜蜂行为的影响。本实验利用喙伸反应研究了亚致死剂量(LD50/100～LD50/10)溴氰菊酯和吡虫啉对意蜂Apis mellifera ligustica L.工蜂嗅觉敏感性的影响。结果发现,经口饲喂溴氰菊酯5ng和10ng后,工蜂对0.1%的蔗糖溶液的敏感性显著下降(P<0.05),水应激指数降低,但对0.3%,1%,3%,10%和30%的蔗糖溶液的敏感性没有显著变化;而经口饲喂吡虫啉0.3ng和0.6ng后,工蜂对上述各浓度蔗糖溶液的敏感性变化不明显,但其水应激指数升高。     

草甘膦与微塑料对西方蜜蜂生存和糖反应行为的影响

为分析草甘膦与微塑料对西方蜜蜂Apis mellifera存活和行为的影响。本研究利用50%蔗糖溶液配置的400 mg/L草甘膦、50 mg/L微塑料以及两者混合物,分别饲喂1日龄的工蜂;每日记录西方蜜蜂的存活率,20 d后通过伸吻反应测定它们对蜜蜂嗅觉学习行为的影响。结果发现400 mg/L草甘膦处理蜜蜂20 d后,与对照组相比,蜜蜂存活率下降了22%,伸吻比率下降了30%;50 mg/L微塑料处理,与对照组相比,蜜蜂存活率下降了9%,伸吻比率下降了10%;用400 mg/L草甘膦与50 mg/L微塑料协同处理20 d后,与对照组相比,蜜蜂死亡率为50%、伸吻比率下降了45%左右。结果表明草甘膦和微塑料均会导致西方蜜蜂存活率降低,影响其糖反应行为,而两者协同处理对西方蜜蜂的影响更显著。     

Sublethal insecticide effects on the probing responsiveness of tsetse flies and blowflies

ABSTRACT. Tethered Glossina austeni Newst. males and females were tested for daily and starvation-related changes in their probing responsiveness to a warmed sponge surface presented to their tarsi. The change in responsiveness of the two sexes was indistinguishable, both following a marked V-shape pattern across the photophase of LD 12:12 and an increase from a mean of c. 5% responding on day 3 after a blood-meal to over 60% doing so on day 6. Sublethal doses ( c. LD₁₅) of endosulfan had no detectable effect on this pattern, but of DDT caused a temporary doubling of responsiveness, and of permethrin caused a marked and long-lasting reduction in responsiveness. Tethered Protophormia terraenovae (R.-D.) tested similarly for changes in threshold to tarsal stimulation with sucrose solutions (assessed by whether or not they extended the proboscis), showed a marked threshold decrease following LD₁₅ diazinon treatment and, like the tsetse, no effect of LD₁₅ endosulfan treatment, though unlike tsetse they showed no increase in threshold following permethrin treatment. The results are discussed in relation to what is known of the mode of action of these four insecticides, and in relation to circadian rhythm physiology in insects.     

Coordination of a dual inhibitory system regulating feeding behaviour in the blowfly

Summary The interactions of excitatory and inhibitory neural input controlling feeding behaviours of fliesPhormia regina Meigen, at three different levels of deprivation were assessed by studying the proboscis extension reflex, volume of sucrose imbibed and the responsiveness of the contact chemosensory neurons. The responsiveness of the sensory cells tested did not change with respect to length of deprivation. The two known inhibitory systems consist of stretch receptors associated with a) the foregut, and b) the abdomen. These two systems were demonstrated to act at different times. The effect of the foregut stretch receptors was shown to be delayed, cumulative and slowly decaying. The abdominal stretch receptors were demonstrated to act immediately and to be important in ending a drink.     

Feeding responses by female Pieris brassicae butterflies to carbohydrates and amino acids

Most Lepidoptera feed during the adult stage on carbohydrate‐rich food sources, primarily floral nectar. However, little is known about the factors leading to the acceptance of a possible food source. It is reported that butterflies select for nectar rich in sucrose and amino acids. This suggests that the insects have developed a sensitivity to these nectar compounds. We tested females of the large cabbage white, Pieris brassicae L. (Lepidoptera: Pieridae) for their responses to 10 different nectar‐ or honeydew‐sugars after either tarsal or proboscis stimulation. In no‐choice experiments, food‐deprived P. brassicae showed the strongest response to sucrose, followed by fructose. Other sugars, including galactose, glucose, maltose, mannose, melezitose, melibiose, raffinose and trehalose, did not elicit a feeding response. Mixtures of essential or common non‐essential amino acids did not stimulate feeding. In a choice situation, P. brassicae preferred sucrose over fructose, whereas they accepted a sucrose and amino acid solution equally to a plain sucrose solution. The results indicate that for P. brassicae, feeding is mainly elicited by sucrose and fructose.