Developmental plasticity of the locomotor activity rhythm of Drosophila melanogaster

We used four replicate outbred populations of Drosophila melanogaster to investigate whether the light regimes experienced during the pre-adult (larval and pupal) and early adult stages influence the free-running period (τ_DD) of the circadian locomotor activity rhythm of adult flies. In a series of two experiments four different populations of flies were raised from egg to eclosion in constant light (LL), in light/dark (LD) 12:12 h cycle, and in constant darkness (DD). In the first experiment the adult male and female flies were directly transferred into DD and their locomotor activity was monitored, while in the second experiment the locomotor activity of the emerging adult flies was first assayed in LD 12:12 h for 15 days and then in DD for another 15 days. The τ_DD of the locomotor activity rhythm of flies that were raised in all the three light regimes, LL, LD 12:12 h and in DD was significantly different from each other. The τ_DD of the locomotor activity rhythm of the flies, which were raised in DD during their pre-adult stages, was significantly shorter than that of flies that were raised as pre-adults in LL regime, which in turn was significantly shorter than that of flies raised in LD 12:12 h regime. This pattern was consistent across both the experiments. The results of our experiments serve to emphasise the fact that in order to draw meaningful inferences about circadian rhythm parameters in insects, adequate attention should be paid to control and specify the environment in which pre-adult rearing takes place. The pattern of pre-adult and early adult light regime effects that we see differs from that previously observed in studies of mutant strains of D. melanogaster, and therefore, also points to the potential importance of inter-strain differences in the response of circadian organisation to external influences.     

The effects of acclimation and rearing conditions on the response of tropical and temperate populations ofDrosophila melanogaster andD. simulans to a temperature gradient (Diptera: Drosophilidae)

The effects of rearing and acclimation on the response of adultDrosophila to temperature were investigated in a gradient.D. melanogaster flies preferred a higher mean temperature and were distributed over a wider range of temperatures thanD. simulans flies. Acclimating adults at different temperatures for a week did not influence the response of either species. Adults reared at 28°C as immatures had a lower mean preference than those reared at cooler temperatures, suggesting that flies compensated for the effects of rearing conditions. Adults from tropical and temperate populations ofD. melanogaster andD. simulans did not differ in the mean temperature they preferred in a gradient, suggesting little genetic divergence for this trait within species. The species differences and environmental responses may be related to changes in optimal physiological conditions for the flies.     

Activity patterns of Queensland fruit flies (Bactrocera tryoni) are affected by both mass‐rearing and sterilization

Mass‐reared sterile tephritid flies released in sterile insect technique (SIT) programmes exhibit behaviour, physiology and longevity that often differ from their wild counterparts. In the present study, video recordings of flies in laboratory cages are used to determine whether the sequential processes of mass‐rearing and sterilization (using gamma radiation) that are integral to SIT affect general activity patterns of male and female Queensland fruit flies Bactrocera tryoni (Froggatt) (Diptera: Tephritidae) (‘Q‐flies'). Compared with wild flies, mass‐reared flies exhibit a marked reduction in overall activity, and further reduction is found after sterilization. In terms of the frequency of activities, both fertile and sterile mass‐reared Q‐flies fly less often and exhibit more bouts of inactivity and grooming than wild Q‐flies. In addition, in terms of the duration of activities, fertile and sterile mass‐reared Q‐flies spend less time flying and more time walking, grooming and being inactive than wild Q‐flies. Although fertile and sterile mass‐reared flies are similar in other regards, sterile mass‐reared flies spend more time being inactive than fertile mass‐reared flies. These findings raise new questions about how changes in behaviour and activity levels may influence the performance of mass‐reared sterile Q‐flies in the field, as well as the physiological and metabolic processes that are involved. The frequency and duration of inactivity could provide a simple but powerful and biologically relevant test for quality in mass‐rearing and SIT programs.     

Biological and Behavioral Effects of Heavy Metals in Drosophila melanogaster Adults and Larvae

Heavy metals are essential components of biological systems but are extremely toxic at high doses. As a result, we hypothesized that perception of heavy metals through gustation may exist in Drosophila melanogaster. In this study, we investigated the behavioral effects of iron, copper, zinc, and cadmium on D. melanogaster gustation, oviposition, and pupation-site selection. In addition, we examined the biological effects of heavy metals on the fruit fly survival and reproductive success. Our results illustrate that D. melanogaster responds behaviorally to the presence of high concentrations of heavy metals in food. All metals acted as repellents to the fruit flies at high doses, with the egg-laying and feeding of the female flies significantly decreasing. Furthermore, supplementation of heavy metals in the culture medium reduced survival to the adult stage and shortened the life span of adult flies. From these observations, we speculate that D. melanogaster avoidance behavior towards high concentrations of heavy metals may have a positive effect on their survival and reproductive success in nature, particularly in the presence of metal-contaminated food sources.     

Wild bacterial probiotics fed to larvae of mass‐reared Queensland fruit fly [Bactrocera tryoni (Froggatt)] do not impact long‐term survival,mate selection,or locomotor activity

Queensland fruit fly [Bactrocera tryoni (Froggatt), Diptera, Tephritidae] is the most devastating insect pest impacting Australian horticulture. The Sterile Insect Technique (SIT) is an important component of tephritid pest management programs. However, mass‐rearing and irradiation (to render insects sterile) may reduce the fitness and performance of the insect, including the ability of sterile males to successfully compete for wild females. Manipulation of the gut microbiome, including the supplementation with bacterial probiotics shows promise for enhancing the quality of mass‐reared sterile flies, however there are fewer published studies targeting the larval stage. In this study, we supplemented the larval stage of mass‐reared B. tryoni with bacterial probiotics. We tested several individual bacteria that had been previously isolated and characterized from the gut of wild B. tryoni larvae including Asaia sp., Enterobacter sp., Lactobacillus sp., Leuconostoc sp. We also tested a consortium of all four of these bacterial isolates. The fitness parameters tested included adult survival in field cages, laboratory mate selection of bacteria supplemented males by bacteria nonsupplemented females, and laboratory locomotor activity of adult flies. None of the bacterial probiotic treatments in the current study was significantly different to the control for field survival, mate selection or locomotor activity of adult B. tryoni, which agree with some of the other studies regarding bacterial probiotics fed to the larval stage of tephritids. Future work is needed to determine if feeding the same, and/or other probiotics to adults, as opposed to larvae can positively impact survival, mating performance, mating competitiveness and locomotor activity of B. tryoni. The bacterial group(s) and function of bacterial species that increase fitness and competitiveness is also of interest to tephritid mass‐rearing programs.     

Pre-exposure affects the olfactory response of Drosophila melanogaster to menthol

A modification of the trap assay (Woodard et al., 1989) was used to evaluate the response of Drosophila melanogaster (Meigen) to food media containing menthol. Dose-response curves for flies to mentholic foods were produced for flies that had been pre-exposed to menthol, during development and adult life, and flies that had not been exposed to menthol before the assay. Mentholic food media were less attractive to Drosophila than plain food medium. Rearing flies on a medium containing menthol reduced their aversion to some concentrations of menthol. The rearing effect was not simply due to lowered general activity levels resulting from developing in a medium containing menthol. There was a threshold concentration of menthol in the rearing medium below which we found no induced behavioural change.     

Fitness components of Drosophila melanogaster developed on a standard laboratory diet or a typical natural food source

Drosophila melanogaster is often used as a model organism in evolutionary biology and ecophysiology to study evolutionary processes and their physiological mechanisms. Diets used to feed Drosophila cultures differ between laboratories and are often nutritious and distinct from food sources in the natural habitat. Here we rear D. melanogaster on a standard diet used in our laboratory and a field diet composed of decomposing apples collected in the field. Flies developed on these two diet compositions are tested for heat, cold, desiccation, and starvation resistance as well as developmental time, dry body mass and fat percentage. The nutritional compositions of the standard and field diets were analyzed, and discussed in relation to the phenotypic observations. Results showed marked differences in phenotype of flies from the two types of diets. Flies reared on the field diet are more starvation resistant and they are smaller, leaner, and have lower heat resistance compared to flies reared on the standard diet. Sex specific effects of diet type are observed for several of the investigated traits and the strong sexual dimorphism usually observed in desiccation resistance in D. melanogaster disappeared when rearing the flies on the field diet. Based on our results we conclude that care should be taken in extrapolating results from one type of diet to another and especially from laboratory to field diets.     

Aging alters properties of the circadian pacemaker controlling the locomotor activity rhythm in males of Drosophila nasuta

Effects of aging on the circadian rhythm of locomotor activity in males of Drosophila nasuta were investigated. The adult life of males was divided in 1-3 stages according to spontaneous changes in free-running period x in constant darkness (DD): stage 1, days 1-19; stage 2, days 20-36; stage 3, days 37-43. Stage 1 was characterized by a bimodal activity pattern with a short light-induced morning peak and a prolonged evening peak when the flies were entrained to light-dark cycles of 12 hours of light, 12 hours of darkness (LD 12:12). The morning peak had a phase angle difference Ψ_m (Ψ, the time from lights on in LD 12:12 cycles to the onset of morning peak) of about 0.1h, while Ψ_e (Ψ of evening peak) was about 9h at stage 1. The transient morning peak was curtailed at the end of stage 1. At stage 2, the Ψ_e was about 10h, and the activity end was delayed by an addition of about 3h of activity in the scotophase. The changes in W during DD free runs were determined in two groups of flies: flies reared in LD 12:12 and flies reared in DD. In both groups, W increased from about 23h at stage 1 to about 25h at stage 2. Stage 3 was characterized by arrhythmicity associated with highest mean activity level (total number of passes/fly/day) in the entrained and both free-running groups. The mean activity level increased significantly from stage 1 to stage 3 in all three groups of flies.     

Dietary consumption of monosodium L‐glutamate induces adaptive response and reduction in the life span of Drosophila melanogaster

Adaptive response is the ability of an organism to better counterattack stress‐induced damage in response to a number of different cytotoxic agents. Monosodium L‐glutamate (MSG), the sodium salt of amino acid glutamate, is commonly used as a food additive. We investigated the effects of MSG on the life span and antioxidant response in Drosophila melanogaster (D. melanogaster). Both genders (1 to 3 days old) of flies were fed with diet containing MSG (0.1, 0.5, and 2.5‐g/kg diet) for 5 days to assess selected antioxidant and oxidative stress markers, while flies for longevity were fed for lifetime. Thereafter, the longevity assay, hydrogen peroxide (H₂O₂), and reactive oxygen and nitrogen species levels were determined. Also, catalase, glutathione S‐transferase and acetylcholinesterase activities, and total thiol content were evaluated in the flies. We found that MSG reduced the life span of the flies by up to 23% after continuous exposure. Also, MSG increased reactive oxygen and nitrogen species and H₂O₂ generations and total thiol content as well as the activities of catalase and glutathione S‐transferase in D. melanogaster (P < .05). In conclusion, consumption of MSG for 5 days by D. melanogaster induced adaptive response, but long‐term exposure reduced life span of flies. This study may therefore have public health significance in humans, and thus, moderate consumption of MSG is advocated by the authors.     

Decline in photopositive tendencies with age inDrosophila melanogaster (Diptera: Drosophilidae)

Phototaxis was measured in young, middle-aged, and oldDrosophila melanogaster flies of both sexes. The apparatus allowed us to measure the tendency to go toward light, independently of the time needed to do so; under such conditions, phototaxis is dissociated from locomotor activity. The percentage of photopositive flies decreased slightly with age (93.96, 80.17, and 78.97%, respectively, in young, middle-aged, and old flies). Results are discussed in connection with previous data for which the tendency to go toward light and the time to do so were not dissociated.     

Ethanol extract of Cassia siamea L. increases life span in Drosophila melanogaster

The stem of Cassia siamea L. (Fabaceae) has been used in traditional Thai medicine as a longevity remedy. The objective of this study was to investigate the effect of ethanolic stem extract of C. siamea (CSE) on the life span of Drosophila melanogaster. The results showed that a diet containing 10 mg/mL CSE could significantly extend the mean life span of D. melanogaster by 14% compared with the control diet (P < 0.01). The maximum life span was 74, 78, and 84 days in control, CSE (5 mg/mL) and CSE (10 mg/mL) groups, respectively. Supplementation of CSE at 10 mg/mL also significantly increases the activity of superoxide dismutase (SOD) and catalase (CAT) at days 25 and 40 compared with the control diet. Treatment of CSE at 5 and 10 mg/mL significantly increased the climbing ability of D. melanogaster both on days 25 and 40 compared with the control flies. Paraquat and H₂O₂ challenge test showed that flies fed with CSE at 10 mg/mL had a longer survival time than the control flies (P < 0.01). This study provides supportive evidence that supplementation with CSE prolonged life span and reduced oxidative stress in D. melanogaster.     

Life Span and Locomotor Activity Modification by Glucose and Polyphenols in <Emphasis Type="Italic">Drosophila melanogaster</Emphasis> Chronically Exposed to Oxidative Stress-stimuli: Implications in Parkinson’s Disease

Previous studies have shown that polyphenols might be potent neuroprotective agents in Drosophila melanogaster, a valid model for PD, acutely treated with oxidative stress-stimulants. This study report for the first time that polyphenols exposure prolong life span (P < 0.05 by log-rang test) and restore locomotor activity (i.e., climbing capability, P < 0.05 by χ² test) of Drosophila melanogaster chronically exposed to paraquat compared to flies treated with paraquat alone in 1% glucose. We found that (10%) glucose partially prolongs life span and climbing in Drosophila exposed to iron, PQ or in combination, suggesting that both stimuli enhance a movement disorder in a concentration-dependent and temporal-related fashion. Moreover, chronic exposure of (1 mM) PQ/(0.5 mM) iron synergistically affect both survival and locomotor function independently of the temporal order of the exposure to the toxicants, but the survival is modulated in a concentration and temporal fashion by glucose. This investigation is the first to report that Ddc-GAL4 transgenic flies chronically fed with polyphenols increase life span (P < 0.05 by log-rang test) and enhance movement abilities (P < 0.05 by χ² test) compared to untreated Ddc-GAL4 or treated with paraquat in 1% glucose. Our present findings support the notion that Drosophila melanogaster might be a suitable model to study genetic, environmental and nutritional factors as causal and/or modulators in the development of PD. Most importantly, according to our model, we have demonstrated for the first time chronic polyphenols exposure as potential therapeutic compounds in the treatment of PD. These findings altogether open new avenues for the screening, testing and development of novel antioxidant drugs against oxidative stress stimuli.     

Diphenyl Diselenide Protects Against Mortality,Locomotor Deficits and Oxidative Stress in Drosophila melanogaster Model of Manganese-Induced Neurotoxicity

Several experimental and epidemiological reports have associated manganese exposure with induction of oxidative stress and locomotor dysfunctions. Diphenyl diselenide (DPDS) is widely reported to exhibit antioxidant, anti-inflammatory and neuroprotective effects in in vitro and in vivo studies via multiple biochemical mechanisms. The present study investigated the protective effect of DPDS on manganese-induced toxicity in Drosophila melanogaster. The flies were exposed, in a dietary regimen, to manganese alone (30 mmol per kg) or in combination with DPDS (10 and 20 µmol per kg) for 7 consecutive days. Exposure to manganese significantly (p < 0.05) increased flies mortality, whereas the survivors exhibited significant locomotor deficits with increased acetylcholinesterase (AChE) activity. However, dietary supplementation with DPDS caused a significant decrease in mortality, improvement in locomotor activity and restoration of AChE activity in manganese-exposed flies. Additionally, the significant decreases in the total thiol level, activities of catalase and glutathione-S-transferase were accompanied with significant increases in the generation of reactive oxygen and nitrogen species and thiobarbituric acid reactive substances in flies exposed to manganese alone. Dietary supplementation with DPDS significantly augmented the antioxidant status and prevented manganese-induced oxidative stress in the treated flies. Collectively, the present data highlight that DPDS may be a promising chemopreventive drug candidate against neurotoxicity resulting from acute manganese exposure.

     

N‐β‐alanyldopamine metabolism,locomotor activity and sleep in Drosophila melanogaster ebony and tan mutants

Drosophila melanogaster Meigen mutants for N‐β‐alanyldopamine (NBAD) metabolism have altered levels of NBAD, dopamine and other neurotransmitters. The ebony¹ mutant strain has very low levels of NBAD and higher levels of dopamine, whereas the opposite situation is observed in the tan¹ mutant. Dopamine is implicated in the control of movement, memory and arousal, as well as in the regulation of sleep and wakefulness in D. melanogaster. N‐β‐alanyldopamine, which is best known as a cuticle cross‐linking agent, is also present in nervous tissue and has been proposed to promote locomotor activity in this fly. The daily locomotor activity and the sleep patterns of ebony¹ and tan¹ mutants are analyzed, and are compared with wild‐type flies. The tan¹ mutant shows reduced locomotor activity, whereas ebony¹ shows higher levels of activity than wild‐type flies, suggesting that NBAD does not promote locomotor activity. Both mutants spend less time asleep than wild‐type flies during night‐time; ebony shows more consolidated activity during night‐time and increased sleep latency, whereas tan is unable to consolidate locomotor activity and sleep in either phase of the day. The daily level of NBAD‐synthase activity is measured in vitro using wild‐type and tan¹ protein extracts, and the lowest NBAD synthesis is observed at the time of higher locomotor activity. The abnormalities in several parameters of the waking/sleep cycle indicate some dysfunction in the processes that regulates these behaviours in both mutants.     

<Emphasis Type="Italic">Zingiber officinale</Emphasis> extends <Emphasis Type="Italic">Drosophila melanogaster</Emphasis> life span in xenobiotic-induced oxidative stress conditions

Background

The possibility of dietary ginger to enhance oxidative stress resistance and to extend life span was studied on Drosophila melanogaster.

Methods

Oxidative stress was induced by a reducing agent dithiothreitol. Experimental groups of male D. melanogaster were cultured on media containing: 1) no additive; 2) dithiothreitol, added into the nutritional mixture to the final concentration of 10 mM; 3) 25 mg of ginger powder g^–1 of the nutritional mixture; and 4) 10 mM of dithiothreitol and 25 mg of ginger powder g^–1 of the nutritional mixture. The number of alive fruit flies was inspected daily, and mean life span was determined for each experimental group.

Results

The addition of dithiothreitol to D. melanogaster nutritional mixture was established to result in an increase in concentration of two markers of oxidative stress conditions (thiobarbituric acid reactive substances as products of lipid peroxidation and carbonylated proteins as products of protein oxidation) in fly tissues. It was followed by significant reduction of mean life span and maximum life span of the last 10% of flies. Plant preparation, being added simultaneously with dithiothreitol, significantly diminished the negative effects of this xenobiotic. In conditions of additional stress load induced by hydrogen peroxide or high temperature, survival of insects treated with dithiothreitol on the background of ginger powder was the highest.

Conclusions

Thus, the presented data give the evidence that ginger preparations can reduce oxidative stress outcomes and significantly increase the life expectancy of fruit flies in stress conditions.

     

Pace‐of‐life: Relationships among locomotor activity,life history,and circadian rhythm in the assassin bug,Amphibolus venator

The pace‐of‐life syndrome (POLS) hypothesis means that animal behavior is correlated with life history strategies. Studies have reported that the free‐running period of the circadian rhythm (length of the period) is correlated with life history strategies in some animals. Although the length of the circadian rhythm may be associated with the POLS hypothesis, few studies have investigated the relationships among animal behavior, life history traits, and circadian rhythm. We tested the POLS hypothesis in the assassin bug, Amphibolus venator, which shows individual variation in locomotor activity. We found higher repeatability of differences in locomotor activity between individuals. Moreover, we found a trade‐off between locomotor activity and developmental period such that active individuals developed faster. However, locomotor activity was not correlated with the length of the circadian rhythm in A. venator. Therefore, this study suggests that the length of the circadian rhythm in A. venator does not support the POLS hypothesis.     

Correlated changes in circadian clocks in response to selection for faster pre-adult development in fruit flies Drosophila melanogaster

Although, circadian clocks are believed to be involved in the regulation of life-history traits such as pre-adult development time and lifespan in fruit flies Drosophila melanogaster, there is very little unequivocal evidence either to support or refute this. Here we report the results of a long-term study aimed at examining the role of circadian clocks in the temporal regulation of pre-adult development in D. melanogaster. We employed laboratory selection protocol for faster pre-adult development on four large, outbred, random mating populations of Drosophila. We assayed pre-adult development time and circadian period of locomotor activity rhythm of these flies at regular intervals of 5–10 generations. After 50 generations of selection, the overall egg-to-adult duration in the selected stocks was reduced by ~29 h (~12.5 %) relative to controls, with the selected populations showing a concurrent reduction in time taken to hatching, pupation and wing pigmentation, by ~2, ~16, and ~25.2 h, respectively. Furthermore, selected populations showed a concomitant reduction in the circadian period of locomotor activity rhythm, implying that circadian clocks and development time are correlated. Thus, our study provides the first ever unequivocal evidence for the evolution of circadian clocks as a correlated response to selection for faster pre-adult development, suggesting that circadian clocks and development are linked in fruit flies D. melanogaster.     

Robust circadian rhythmicity of Drosophila melanogaster requires the presence of lateral neurons: a brain-behavioral study of disconnected mutants

Mutations at the disconnected (disco) locus of Drosophila melanogaster disrupt neural cell patterning in the visual system, leading to the loss of many optic lobe neurons. Drosophila's presumptive circadian pacemaker neurons – the dorsal and ventral lateral neurons – are usually among the missing cells, and most disco flies are behaviorally arrhythmic. In this study, I show that ventral lateral neurons (LN_vs) are occasionally present and provoke robust circadian rhythmicity in disco mutants. Of 357 individual disco flies four animals with robust circadian rhythmicity were found. All four retained LN_vs together with terminals in the superior protocerebrum. Residual or bi-circadian rhythmicity was found in about 20% of all flies; the remaining flies were completely arrhythmic. One of the flies with residual rhythmicity and two of the arrhythmic flies also had some LN_vs stained. However, these flies lacked the LN_v fibers in the superior protocerebrum. The results suggest that the presence of single LN_vs is sufficient to provoke robust circadian rhythmicity in locomotor activity if the LN_v terminals reach the superior protocerebrum. The presence of residual or bi-circadian rhythmicity in 20% of the flies without LN_vs indicates that also other cells contribute to the rhythmic control of locomotor activity. Accepted: 17 September 1997     

Spermidine promotes stress resistance in Drosophila melanogaster through autophagy-dependent and -independent pathways

The naturally occurring polyamine spermidine (Spd) has recently been shown to promote longevity across species in an autophagy-dependent manner. Here, we demonstrate that Spd improves both survival and locomotor activity of the fruit fly Drosophila melanogaster upon exposure to the superoxide generator and neurotoxic agent paraquat. Although survival to a high paraquat concentration (20 mM) was specifically increased in female flies only, locomotor activity and survival could be rescued in both male and female animals when exposed to lower paraquat levels (5 mM). These effects are dependent on the autophagic machinery, as Spd failed to confer resistance to paraquat-induced toxicity and locomotor impairment in flies deleted for the essential autophagic regulator ATG7 (autophagy-related gene 7). Spd treatment did also protect against mild doses of another oxidative stressor, hydrogen peroxide, but in this case in an autophagy-independent manner. Altogether, this study establishes that the protective effects of Spd can be exerted through different pathways that depending on the oxidative stress scenario do or do not involve autophagy.