Post-teneral protein feeding enhances sexual performance of Queensland fruit flies

Abstract.  Adult diet is an important determinant of sexual activity in many tephritid fruit flies. Whether availability of protein (hydrolysed yeast) in addition to sucrose influences sexual activity or longevity of male and female Queensland fruit flies ( Bactrocera tryoni Froggatt, 'Q-flies'), and whether irradiation of flies as pupae modifies their dietary needs, is investigated. Previous studies on groups of flies suggest that protein is required for sexual maturation of females but not males. By contrast, this study of individual flies demonstrates that protein in the adult diet provides a massive boost to sexual activity of both males and females. Mating probability increases with age from 4-14 days as the flies began to mature. However, mating probability reaches much higher levels when the flies are provided with protein. Although males and females mate at similar rates when provided with protein, females suffer a greater reduction in mating probability than males when deprived of protein. In addition to increased mating probability, access to dietary protein is also associated with reduced latency from onset of dusk until copulation. Furthermore, young male flies with access to dietary protein have longer copula duration than males fed only sucrose. Irradiation of flies as pupae has no apparent effect on mating probability, the latency to copulate or copula duration. However, when deprived of protein, sterile flies (especially males) suffer a greater reduction in longevity compared with fertile flies. Overall, access to dietary protein increases longevity for both males and females, although females live longer than males on both diets. These findings suggest that prerelease provision of dietary protein has the potential to greatly enhance the efficacy of Q-flies used in the sterile insect technique.     

Effects of diet and activity on lipid levels of adult Mediterranean fruit flies

Abstract. The objectives of this study were to determine whether adult Mediterranean fruit flies, Ceratitis capitata Wiedeman (Diptera: Tephritidae), are capable of synthesizing lipids, and whether adult diet affects this ability.Lipid levels in females fed protein and carbohydrate or carbohydrate alone declined significantly from emergence to the fourth day of life and then rose back to teneral levels on the fifth day, before oviposition took place on the sixth day.In males fed protein and carbohydrate, lipid levels initially declined as males aged and then stabilized.In carbohydrate-fed males lipid levels declined following emergence and recovered somewhat by the sixth day.Lipid levels declined significantly when flies underwent post-emergence starvation, but after substantial feeding on the above-mentioned diets they eventually (within 6–7 days) reached teneral levels in all experimental groups.Multivariate analysis of variance revealed that differences in lipid contents are primarily related to the flies' age, which corresponds to the various sex-specific activities these flies exhibit.Average lipid investment in eggs was found to equal teneral lipid levels in females.Without lipogenic abilities, oviposition would completely deplete female lipid reserves.We conclude that adult medflies are capaple of lipid synthesis, and that this capability is modulated by individual and sex-specific activity patterns.     

Effects of sugar feeding on carbohydrate and lipid metabolism in a parasitoid wasp

Lifetime patterns of carbohydrate and lipid metabolism were compared in starved and sucrose‐fed adults of the parasitoid Macrocentrus grandii (Goidanich) (Hymenoptera: Braconidae). As expected, sucrose‐fed individuals lived longer than did starved individuals. Macrocentrus grandii males and females eclosed with levels of simple storage sugars (presumably primarily trehalose) and glycogen that were below maximum levels recorded from sucrose‐fed parasitoids. Both of these nutrients dropped to very low levels in starved individuals within 4 days post‐emergence and were maintained at high levels in sucrose‐fed individuals throughout their lives. Lipid reserves at emergence represented the highest lipid levels for both sexes in the two diet treatments, with levels declining over the lifetimes of males and females from both diet treatments. Our results therefore suggest that dietary sucrose is used to synthesize trehalose and glycogen, but not lipids in M. grandii. Also, in contrast to the patterns observed for the simple sugars and glycogen, lipid levels in starved individuals did not drop below levels observed in sugar‐fed individuals. The average number of mature eggs carried by females at emergence was 33 and increased to approximately 85 in sucrose‐fed and 130 in starved females by the age of 5 d in the absence of hosts. The egg maturation rate was therefore higher in starved than in sugar‐fed females. Potential explanations for this unexpected result are discussed.     

Effect of bacteria on nutritional status and reproductive success of the Mediterranean fruit fly Ceratitis capitata

Abstract.  Mediterranean fruit flies ( Ceratitis capitata Wiedemann, Diptera: Tephritidae) harbor a community of diazotrophic bacteria in their digestive system. The present study aims to test the hypothesis that bacteria contribute to fly fitness by enhancing copulatory success and egg production in males and females, respectively. After eclosion, flies were fed a full diet containing peptides, sugar and minerals, or a sugar diet, lacking peptides. Subgroups from each diet were fed a mixture of the antibiotics ciprofloxacin and piperacillin. The presence of bacteria, food consumption, weight gain, lipid and protein levels, oviposition in females and copulatory success of males were quantified in the four groups. The antibiotic treatment effectively cleared the gut of bacteria. The relative amounts of food consumed (with or without antibiotics) are similar in all groups. The antibiotics do not inhibit feeding, and their ingestion does not affect dry weight or the amount of protein stored, yet females feeding on the full diet without antibiotics have increased lipid levels. Females fed the full diet produce significantly more eggs than females on the sugar diet, but the presence of bacteria does not affect numbers of eggs produced. However, in the absence of bacteria, the oviposition rate of nutritionally stressed females is significantly accelerated. The presence of bacteria in sugar fed males does not provide them with a mating advantage. Conversely, in males fed a full diet, the presence of bacteria is associated significantly with a shorter latency to mate. It is concluded that, because the bacterial community is present at all stages of the fly's life cycle, at least some species are effectively transmitted from parents to offspring, and removal of bacteria affects measurable physiological and behavioural parameters related to fitness, the association between bacteria and the medfly is mutualistic.     

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.     

Social interactions regulate resource utilization in a Tephritidae fruit fly

Previous studies have suggested that social interactions (e.g., the actions and reactions elicited by the interaction of co-specific individuals) induce individual fruit flies (Tephritidae) to ingest more food, especially protein-rich food. Changes in feeding behavior related to social interactions have been associated with reproduction (e.g., when different sexes are present), reproductive facilitation (e.g., when two females interact) and stress and aggression (e.g., flies of the same sex, or crowdedness). The present study investigated the effect of social interaction on the feeding, longevity and resource management of the Ethiopian fruit fly, Dacus ciliatus. Single flies and pairs of flies (of the same or different sexes) were confined to a small arena (the PUB system), in which we measured the amount of liquid food ingested daily by each fly. In addition, we sampled flies of different ages, extracted and quantified their lipid and protein contents, and related individual metabolic contents to the ingestion of a fructose and protein hydrolysate solution. Results showed that individual ingestion was significantly higher in flies maintained in pairs than in flies kept as solitary individuals. The highest intake rates were observed for the female–female pairs. In general, females ingested significantly greater volumes than males. Lipid contents tended to decrease progressively with age in flies kept as solitary individuals, especially in female flies, while lipid levels decreased and then increased in flies maintained in pairs. Protein trends were similar, although less pronounced than the patterns observed for the lipids. The flies kept as solitary individuals lived significantly longer than those kept in pairs. A resource-management analysis points to a decreased metabolic rate in flies kept as solitary individuals, as compared to paired flies. Results are discussed in view of theories of resource management and survival strategies.     

Effects of different protein concentrations on longevity and feeding behavior of two adult populations of Ceratitis capitata Wiedemann (Diptera: Tephritidae)

The effects of protein intake on two adult male and female populations of Ceratitis capitata Wiedemann were assessed. One population consisted of flies reared for twenty years in the laboratory (Lab-pop); the other population consisted both of flies reared in the laboratory for approximately fifteen years and of the periodically introduced wild flies (Hybrid-pop). Three diets were tested: a no-yeast diet and two diets containing yeast (protein source) at the concentrations 6.5 g or 1.5 g per 100 ml diet. The parameters analyzed were: adult longevity, diet intake with and without yeast, and discrimination threshold for yeast. Protein intake increased Lab-pop adult longevity and did not affect longevity of the Hybrid-pop. Longevity in each population was similar for males and females fed on the same diet. Food behavior were similar for male and female adults of both populations; all preferred diets containing protein (yeast). Males and females in both populations ingested similar amounts of each diet. The discrimination threshold for yeast was similar for all males (0.5 g yeast/100 ml diet); Lab-pop females were able to detect the presence of smaller quantities of yeast in their diet, thus having a higher discrimination capacity (0.4 g/100 ml diet) as compared to the Hybrid-pop females (0.6 g/ 100 ml diet).     

Nutrient balance in medfly, Ceratitis capitata, larval diets affects the ability of the developing insect to incorporate lipid and protein reserves

The Mediterranean fruit fly [Ceratitis capitata Wiedemann (Diptera: Tephritidae)], or medfly, is mass produced in many facilities throughout the world to supply sterile flies for sterile insect technique programs. Production of sterile males requires large amounts of larval and adult diets. Larval diets comprise the largest economic burdens in the mass production of sterile flies, and are one of the main areas where production costs could be reduced without affecting quality and efficacy. The present study investigated the effect of manipulating diet constituents on larval development and performance. Medfly larvae were reared on diets differing in the proportions of brewer's yeast and sucrose. We studied the effect of such diets on the ability of pupating larvae to accumulate protein and lipids, and on other developmental indicators. Except for diets with a very low proportion of brewer's yeast (e.g., 4%), pupation and adult emergence rates were in general high and satisfactory. The ability of pupating larvae to accumulate lipid reserves and proteins was significantly affected by the sucrose and yeast in the diet, and by the proportion of protein to carbohydrates (P/C). In contrast to previous nutritional studies conducted with other insects, low P/C in medfly larval diets (with excess dietary carbohydrates) resulted in pupating medfly larvae having a relatively reduced load of lipids; medfly larvae protein contents in these diets were, as expected, relatively low. Similarly, high P/C ratios in the diet produced larvae with high protein and lipid contents. Differences with other insects may be due to differential post‐ingestion regulation where a high dietary carbohydrate diet reduces the lipogenic activity of the larvae, and induces a shift from lipid to glucose oxidation. Larvae reared on low P/C diets spent more time foraging in the diet than larvae maintained on a high P/C diet, suggesting a compensatory mechanism to complement nutrient intake. The results suggest that the content of brewer's yeast, the most expensive diet component, could be fine‐tuned without apparently affecting fly quality.     

Adult diet and male-female contact effects on female reproductive potential in Mexican fruit fly (Anastrepha ludens Loew) (Diptera tephritidae)

Wild strains of fruit flies (Diptera: Tephritidae) placed into laboratory rearing conditions are subjected to selection pressures caused by the diet, cages, density of flies, and other factors. Selection that changes mating behavior of the strain may result in less effective males released in sterile insect programs. Tests were performed to examine the effects of protein in diet and adult interactions on egg production and mating during sexual maturation of the Mexican fruit fly (Anastrepha ludens Loew) in laboratory cages. Flies were offspring of wild flies collected from Chiapas or Nuevo Leon, Mexico, and reared on Valencia oranges. Experiments demonstrated effects of yeast hydrolysate protein in adult diet and pairing with males on production of mature and immature eggs, numbers of females producing eggs, and mating with females aged 15 d. Addition of protein to 4% fructose in the adult diet approximately tripled mature egg production in females maintained for the total maturation period with an equal number of males. Females that matured without males produced approximately 33% more-mature eggs when fed protein than those fed no protein. Total egg production of females matured without males and fed sugar only or sugar with protein was more than twice that of females matured with males. Tests to examine the effects of male and female diet separately on female egg production showed slightly higher egg production in females fed protein, or females paired with males fed protein, but these differences were not significant. The most definitive effects were that combining wild strain females and males in cages during maturation reduced egg production. This effect was greatest when flies were not fed protein.     

Influence of diet on synthesis and utilisation of lipids for reproduction by the tsetse fly Glossina morsitans

Fatty acid composition of lipids from adult Glossina morsitans was unaffected by an in vitro fed diet of cow blood which induces production of under-sized offspring compared to that of flies fed on a superior diet of pig blood. The commonest fatty acids were C_16:0, C_16:1 and C_18:1 and only small differences in proportions were detected between virgin and pregnant females. Rate of lipid accumulation by males and females was the same and was unaffected by diet, but males achieved a maximum of 2.5 mg on day 9 while both virgin and fertilised females reached a maximum of 5,0 mg on day 14 of adult life. Lipid content of pregnant flies then fell to 3.0 mg on the day of larviposition and accumulation began again. A cow blood diet reduced the extent to which the lipids were utilised for larval growth and this was reflected in an altered secretory activity cycle in the female uterine gland. However, no effect on the growth of adult fat body was detectable in such flies. Mating and fertilisation, which influence reproductive events through activity of the endrocine system do not seem to affect the acquisition of lipid reserves by female Glossina. However, they clearly exert considerable influence over distribution of such reserves between fat body and uterine gland, which distribution is also affected by diet.     

High sucrose consumption promotes obesity whereas its low consumption induces oxidative stress in Drosophila melanogaster

The effects of sucrose in varied concentrations (0.25–20%) with constant amount of yeasts in larval diet on development and metabolic parameters of adult fruit fly Drosophila melanogaster were studied. Larvae consumed more food at low sucrose diet, overeating with yeast. On high sucrose diet, larvae ingested more carbohydrates, despite consuming less food and obtaining less protein derived from yeast. High sucrose diet slowed down pupation and increased pupa mortality, enhanced levels of lipids and glycogen, increased dry body mass, decreased water content, i.e. resulted in obese phenotype. Furthermore, it suppressed reactive oxygen species-induced oxidation of lipids and proteins as well as the activity of superoxide dismutase. The activity of catalase was gender-related. In males, at all sucrose concentrations used catalase activity was higher than at its concentration of 0.25%, whereas in females sucrose concentration virtually did not influence the activity. High sucrose diet increased content of protein thiols and the activity of glucose-6-phosphate dehydrogenase. The increase in sucrose concentration also enhanced uric acid level in females, but caused opposite effects in males. Development on high sucrose diets was accompanied by elevated steady-state insulin-like peptide 3 mRNA level. Finally, carbohydrate starvation at yeast overfeeding on low sucrose diets resulted in oxidative stress reflected by higher levels of oxidized lipids and proteins accompanied by increased superoxide dismutase activity. Potential mechanisms involved in regulation of redox processes by carbohydrates are discussed.     

Sexual dimorphism in the nutritional requirement for adult lifespan in Drosophila melanogaster

The nutritional requirements of Drosophila have mostly been studied for development and reproduction, but the minimal requirements for adult male and female flies for lifespan have not been established. Following development on a complete diet, we find substantial sex difference in the basic nutritional requirement of adult flies for full length of life. Relative to females, males require less of each nutrient, and for some nutrients that are essential for development, adult males have no requirement at all for lifespan. The most extreme (and surprising) sex differences were that chronic cholesterol and vitamin deficiencies had no effect on the lifespan of adult males, but they greatly decreased lifespan in females. Female oogenesis rather than chromosomal karyotype and mating status is the key cause of this gender difference in life‐sustaining nutritional requirements. These data are important to the way we understand the mechanisms by which diet modifies lifespan.     

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.     

Development of probiotic diets for the olive fly: evaluation of their effects on fly longevity and fecundity

One possible control strategy against the olive fly, Bactrocera oleae, the most serious olive crop pest, is the Sterile Insect Technique (SIT) application. However, a number of problems associated with this method remain that decrease the effectiveness of SIT, including the quality of reared insects. Taking the importance of the relationship between the olive fly and bacteria into consideration, the effects of probiotic diets enriched with Pseudomonas putida on B. oleae longevity and fecundity were evaluated. First, we found that the probiotic bacterium, P. putida, is conveyed from diets to the oesophageal bulb as well as to the fly midgut after feeding on the probiotic diet. Subsequently, B. oleae adults fed on either: (a) a standard full protein and sugar diet; (b) a sugar only diet; (c) a probiotic standard full protein and sugar diet; or (d) a probiotic sugar diet. Flies fed on probiotic diets were supplied with an inoculated gel containing P. putida; non‐inoculated gel was provided to the flies fed on non‐probiotic diets. B. oleae males and females that fed on sugar diets did not survive as long as those that fed on protein diets. A comparison of the longevity of adults fed on full diet and sugar with their respective probiotic diets revealed no significant difference. Males fed on the sugar only diet survived longer than males fed on probiotic sugar diet, and females fed on the full protein and sugar diet survived much longer than females fed on the full probiotic diet. As regarding fecundity, both full diets resulted in a higher number of eggs laid per female. Females fed on the probiotic sugar diet laid a higher number of eggs than females that fed on sugar only. The inoculated gel of the probiotic sugar diet contained a significantly higher quantity of leucine, isoleucine and proline than the non‐inoculated gel of the sugar only diet. The possible role of dietary bacteria in relation to functional aspects of olive fly physiology is discussed.     

Potential for pre-release diet supplements to increase the sexual performance and longevity of male Queensland fruit flies

1 Recent studies have shown that continuous access to a protein source (yeast hydrolysate) can greatly enhance the sexual performance of male Queensland fruit flies ( Bactrocera tryoni ; 'Q-flies'). However, in Sterile Insect Technique programmes used to eradicate or suppress wild populations, mass-reared Q-flies are typically fed only sucrose and water for up to 2 days before release.
2 We investigated whether adding a protein source to the diet of male Q-flies for a 24- or 48-h window after emergence and then removing it is sufficient to enhance mating probability, latency to mate, copula duration, probability of sperm storage, number of sperm stored, female remating tendency and longevity of male Q-flies.
3 Protein-fed males were more likely to mate than males fed only sucrose, especially when young. Protein-fed males also had shorter mating latencies and longer copulations than protein-deprived males.
4 Females mated by protein-fed males were more likely to store sperm, stored more sperm and were less likely to remate than were females mated by protein-deprived males. Females were also less likely to remate if their first mate had been large.
5 Overall, providing male Q-flies access to a protein source for a 24- or 48-h window early on in their adult life was sufficient to greatly enhance all assessed measures of performance. Although 24-h access was sufficient for a notable enhancement, further benefits were evident in males provided 48-h access.
6 The results are discussed in terms of the practical implications for Sterile Insect Technique programs used to eradicate or suppress wild Q-fly populations.     

The effect of diet on activity in male Calliphora vicina blowflies

ABSTRACT. The effect of diet on the activity of male Calliphora vicina R.D. (Diptera, Calliphoridae) was studied. Protein–fed males (PF) were significantly more active than males fed only on sugar and water (NPF); as a consequence they ingested more sugar. The phenomenon was probably due to PF insects spending more time in flight than NPF, as no significant differences were found between the wingbeat frequencies and flight speeds of tethered flies of the two treatments. Protein ingestion also had a physiological effect, as PF flies had heavier thoraces than NPF flies with increased titres of protein.     

Additive and interactive effects of nutrient classes on longevity, reproduction, and diet consumption in the Queensland fruit fly (Bactrocera tryoni)

Insect lifespan is often closely linked to diet, and diet manipulations have been central to studies of ageing. Recent research has found that lifespan for some flies is maximised on a very low yeast diet, but once all yeast is removed, lifespan drops precipitously. Although effects of yeast availability on lifespan are commonly interpreted in terms of protein, yeast is a complex mix of nutrients and provides a rich source of vitamins, minerals and sterols. Elucidating which components of yeast are involved in this lifespan drop provides insights into more specific nutritional requirements and also provides a test for the commonplace interpretation of yeast in terms of protein. To this end, we fed Queensland fruit flies (Bactrocera tryoni) one of eight experimental diets that differed in the nutrient group(s) found in yeast that were added to sucrose: none, vitamins, minerals, amino acids, cholesterol, vitamin+mineral+cholesterol (VMC), vitamin+mineral+cholesterol+amino acids (VMCA), and yeast. We measured survival rates and egg production in single sex and mixed sex cages, as well as nutrient intake of individual flies. We found that the addition of minerals increased lifespan of both male and female flies housed in single sex cages by decreasing baseline mortality. The addition of just amino acids decreased lifespan in female flies; however, when combined with other nutrient groups found in yeast, amino acids increased lifespan by decreasing both baseline mortality and age-specific mortality. Flies on the yeast and VMCA diets were the only ones to show significant egg production. We conclude that the drop in lifespan observed when all yeast is removed is explained by missing micronutrients (vitamins, minerals and cholesterol) as well as the absence of protein in females, whereas minerals alone can explain the pattern for males. These results indicate a need for caution when interpreting effects of dietary yeast as effects of protein.     

Male and female condition influence mating performance and sexual receptivity in two tropical fruit flies (Diptera: Tephritidae) with contrasting life histories

Recent recognition of widespread polyandry in insects has generated considerable interest in understanding why females mate multiple times and in identifying factors that affect mating rate and inhibit female remating. However, little attention has been paid to understanding the question from both a female and male perspective, particularly with respect to factors that may simultaneously influence female remating rates. Here, we report on a study aimed at ascertaining the possible interactive effects that male and female size and diet, and female access to a host could have on mating latency, probability, and duration and female refractory period using two tropical fruit fly species with contrasting life histories. Of all factors tested, adult diet played the most significant role. Both Anastrepha ludens and Anastrepha obliqua males which had constant access to protein and sucrose mated more often, had shorter copulations and induced longer refractory periods in females than males fed a low quality diet (sucrose offered every third day). Female size and the interaction with male diet determined how quickly female A. ludens mated for the first time. Smaller females mated sooner with low quality fed males than with high quality fed males while there was no difference for large females, suggesting that male choice may be at play if high quality fed males discriminate against smaller females. Copulation duration also depended on both male and female nutritional condition, and the interaction between male diet and female size and diet. Large and high quality fed females had shorter copulations regardless of male condition. Importantly, for A. ludens, female refractory period depended on male size and the nutritional condition of both males and females, which could indicate that for this species, female receptivity does not depend only on the condition of the male ejaculate. For A. obliqua refractory period was associated with the interaction between male size and diet and male diet and host presence. We discuss our results in terms of male ability to inhibit female remating and the relative contribution of female condition to this behavior. We also address the importance of studying effects simultaneously on species with contrasting life histories.     

Dietary Modulation of Drosophila Sleep-Wake Behaviour

Background

A complex relationship exists between diet and sleep but despite its impact on human health, this relationship remains uncharacterized and poorly understood. Drosophila melanogaster is an important model for the study of metabolism and behaviour, however the effect of diet upon Drosophila sleep remains largely unaddressed.

Methodology/Principal Findings

Using automated behavioural monitoring, a capillary feeding assay and pharmacological treatments, we examined the effect of dietary yeast and sucrose upon Drosophila sleep-wake behaviour for three consecutive days. We found that dietary yeast deconsolidated the sleep-wake behaviour of flies by promoting arousal from sleep in males and shortening periods of locomotor activity in females. We also demonstrate that arousal from nocturnal sleep exhibits a significant ultradian rhythmicity with a periodicity of 85 minutes. Increasing the dietary sucrose concentration from 5% to 35% had no effect on total sucrose ingestion per day nor any affect on arousal, however it did lengthen the time that males and females remained active. Higher dietary sucrose led to reduced total sleep by male but not female flies. Locomotor activity was reduced by feeding flies Metformin, a drug that inhibits oxidative phosphorylation, however Metformin did not affect any aspects of sleep.

Conclusions

We conclude that arousal from sleep is under ultradian control and regulated in a sex-dependent manner by dietary yeast and that dietary sucrose regulates the length of time that flies sustain periods of wakefulness. These findings highlight Drosophila as an important model with which to understand how diet impacts upon sleep and wakefulness in mammals and humans.     

Total body nitrogen and total body carbon as indicators of body protein and body lipids in the melon fly Bactrocera cucurbitae: Effects of methoprene, a juvenile hormone analogue, and of diet supplementation with hydrolyzed yeast

The application of methoprene, and providing access to diet including hydrolyzed yeast, are treatments known to enhance mating success in the male melon fly Bactrocera cucurbitae Coquillett (Diptera: Tephritidae), supporting their use in mass rearing protocols for sterile males in the context of sterile insect technique (SIT) programmes. The objective of the present laboratory study was to investigate the effect of methoprene application and diet supplementation with hydrolyzed yeast (protein) on the turnover of body lipids and protein to confirm the feasibility of their application in melon fly SIT mass-rearing programmes. While females had access to a diet that included hydrolyzed yeast (protein), males were exposed to one of the following treatments: (1) topical application of methoprene and access to diet including protein (M+P+); (2) only diet including protein (M−P+); (3) only methoprene (M+P−) and (4) untreated, only sugar-fed, control males (M−P−). Total body carbon (TBC) and total body nitrogen (TBN) of flies were measured at regular intervals from emergence to 35 days of age for each of the different treatments. Nitrogen assimilation and turnover in the flies were measured using stable isotope (¹⁵N) dilution techniques. Hydrolyzed yeast incorporation into the diet significantly increased male body weight, TBC and TBN as compared to sugar-fed males. Females had significantly higher body weight, TBC and TBN as compared to all males. TBC and TBN showed age-dependent changes, increasing until the age of sexual maturity and decreasing afterwards in both sexes. Methoprene treatment did not significantly affect TBC or TBN. The progressive increase with age of TBC suggests that lipogenesis occurs in adult male B. cucurbitae, as is the case in other tephritids. Stable isotope dilution was shown to be an effective method for determining N uptake in B. cucurbitae. This technique was used to show that sugar-fed males rely solely on larval N reserves and that the N uptake rate in males with access to diet including hydrolyzed yeast was higher shortly after emergence and then stabilized. The implications of the results for SIT applications are discussed.