Ant cues affect the oviposition behaviour of fruit flies (Diptera: Tephritidae) in Africa

Abstract. Although most studies on fruit fly oviposition behaviour focus on horizontal interactions with competitors and cues from host plants, vertical interactions with predators are poorly documented. The present study provides direct evidence indicating that the oviposition behaviour of the two main mango fruit fly species, Ceratitis cosyra (Walker) and Bactrocera invadens Drew‐Tsurata & White, is affected by secretions of the dominant arboreal ant Oecophylla longinoda (Latreille). When offered ant‐exposed and unexposed mangoes in the absence of the ants, both fly species are reluctant to land on ant‐exposed fruits and, when having landed, often take off quickly and fail to oviposit. The number of puparia collected from unexposed mangoes is approximately eight‐fold higher than from ant‐exposed ones. The results obtained from laboratory experiments and field observations confirm that adult fruit flies are more affected through repellence by ant cues than by direct predation. The use of cues by fruit flies in predator avoidance has implications for evolutionary ecology, behavioural ecology and chemical ecology.     

Extending the Functionality of Behavioural Change-Point Analysis with k-Means Clustering: A Case Study with the Little Penguin (Eudyptula minor)

We present a simple framework for classifying mutually exclusive behavioural states within the geospatial lifelines of animals. This method involves use of three sequentially applied statistical procedures: (1) behavioural change point analysis to partition movement trajectories into discrete bouts of same-state behaviours, based on abrupt changes in the spatio-temporal autocorrelation structure of movement parameters; (2) hierarchical multivariate cluster analysis to determine the number of different behavioural states; and (3) k-means clustering to classify inferred bouts of same-state location observations into behavioural modes. We demonstrate application of the method by analysing synthetic trajectories of known ‘artificial behaviours’ comprised of different correlated random walks, as well as real foraging trajectories of little penguins (Eudyptula minor) obtained by global-positioning-system telemetry. Our results show that the modelling procedure correctly classified 92.5% of all individual location observations in the synthetic trajectories, demonstrating reasonable ability to successfully discriminate behavioural modes. Most individual little penguins were found to exhibit three unique behavioural states (resting, commuting/active searching, area-restricted foraging), with variation in the timing and locations of observations apparently related to ambient light, bathymetry, and proximity to coastlines and river mouths. Addition of k-means clustering extends the utility of behavioural change point analysis, by providing a simple means through which the behaviours inferred for the location observations comprising individual movement trajectories can be objectively classified.     

Biotic Interactions in the Face of Climate Change: A Comparison of Three Modelling Approaches

Climate change is expected to alter biotic interactions, and may lead to temporal and spatial mismatches of interacting species. Although the importance of interactions for climate change risk assessments is increasingly acknowledged in observational and experimental studies, biotic interactions are still rarely incorporated in species distribution models. We assessed the potential impacts of climate change on the obligate interaction between Aeshna viridis and its egg-laying plant Stratiotes aloides in Europe, based on an ensemble modelling technique. We compared three different approaches for incorporating biotic interactions in distribution models: (1) We separately modelled each species based on climatic information, and intersected the future range overlap (‘overlap approach’). (2) We modelled the potential future distribution of A. viridis with the projected occurrence probability of S. aloides as further predictor in addition to climate (‘explanatory variable approach’). (3) We calibrated the model of A. viridis in the current range of S. aloides and multiplied the future occurrence probabilities of both species (‘reference area approach’). Subsequently, all approaches were compared to a single species model of A. viridis without interactions. All approaches projected a range expansion for A. viridis. Model performance on test data and amount of range gain differed depending on the biotic interaction approach. All interaction approaches yielded lower range gains (up to 667% lower) than the model without interaction. Regarding the contribution of algorithm and approach to the overall uncertainty, the main part of explained variation stems from the modelling algorithm, and only a small part is attributed to the modelling approach. The comparison of the no-interaction model with the three interaction approaches emphasizes the importance of including obligate biotic interactions in projective species distribution modelling. We recommend the use of the ‘reference area approach’ as this method allows a separation of the effect of climate and occurrence of host plant.     

A Locus in Drosophila sechellia Affecting Tolerance of a Host Plant Toxin

Many insects feed on only one or a few types of host. These host specialists often evolve a preference for chemical cues emanating from their host and develop mechanisms for circumventing their host’s defenses. Adaptations like these are central to evolutionary biology, yet our understanding of their genetics remains incomplete. Drosophila sechellia, an emerging model for the genetics of host specialization, is an island endemic that has adapted to chemical toxins present in the fruit of its host plant, Morinda citrifolia. Its sibling species, D. simulans, and many other Drosophila species do not tolerate these toxins and avoid the fruit. Earlier work found a region with a strong effect on tolerance to the major toxin, octanoic acid, on chromosome arm 3R. Using a novel assay, we narrowed this region to a small span near the centromere containing 18 genes, including three odorant binding proteins. It has been hypothesized that the evolution of host specialization is facilitated by genetic linkage between alleles contributing to host preference and alleles contributing to host usage, such as tolerance to secondary compounds. We tested this hypothesis by measuring the effect of this tolerance locus on host preference behavior. Our data were inconsistent with the linkage hypothesis, as flies bearing this tolerance region showed no increase in preference for media containing M. citrifolia toxins, which D. sechellia prefers. Thus, in contrast to some models for host preference, preference and tolerance are not tightly linked at this locus nor is increased tolerance per se sufficient to change preference. Our data are consistent with the previously proposed model that the evolution of D. sechellia as a M. citrifolia specialist occurred through a stepwise loss of aversion and gain of tolerance to M. citrifolia’s toxins.     

Microbial mediation of fruit fly–host plant interactions: is the host plant the “centre of activity”?

Insects utilize resources in their environment with the aid of mutualistic or symbiotic mediation by microorganisms. Some insect species such as ants and termites often have complex ecological and evolutionary associations with their symbionts, while the nature and functional significance of such associations in non-social insects is often unclear. In the Dacinae (Diptera: Tephritidae), specific Enterobacteriaceae ( Erwinia herbicola , Enterobacter cloacae , Klebsiella oxytoca ) are believed to mediate interactions between the adult fruit flies and the larval host plant. This bacterial mediation is hypothesized as being integral to the larval host plant being the "centre of activity" of the fly. Using a non-pest, monophagous fruit fly ( Bactrocera cacuminata [Hering]), we tested this hypothesis by manipulating the fruiting state of its larval host plant ( Solanum mauritianum Scopoli) and subsequently assessing insect behaviour and phylloplane microflora on those hosts. On host plants that had never fruited, few flies or bacterial colonies were recorded, consistent with hypothesis expectations. On fruiting host plants or plants that had had their fruit removed, bacterial colonies were present; again consistent with expectation. However, few flies were recorded on fruit-removed plants and all fly behaviours, other than resting or oviposition, were rare or absent on any hosts; inconsistent with expectation. The general pattern of results suggested that female flies coming to oviposit on fruiting hosts were spreading Enterobacteriaceae, but such spread was incidental and not part of some mutualistic interaction between fruit flies and bacteria.     

A tentative evaluation for population establishment of Bactrocera dorsalis (Diptera: Tephritidae) by its population modeling: Considering the temporal distribution of host plants in a selected area in Jeju,Korea

The Oriental fruit fly, Bactrocera dorsalis (Hendel) (Diptera: Tephritidae) is a destructive fruit pest in a wide range of cultivated fruit crops and wild plants. This species is a potentially highly invasive fruit fly to Jeju area of Korea. This study was conducted to evaluate the effect of host plants distributed temporally on the population development of B. dorsalis. The temperature-dependent bionomic data for a synonymous group of B. dorsalis, including B. philippinensis, B. papayae, and B. invadens were collected from previous publications and combined to construct a population model of this pest and its thermal constant. We developed a stage-transition model of eggs, larvae and pupae, and an oviposition model for basic population modeling of the four common strains. We investigated the abundance of the host plants of B. dorsalis in a selected site in Jeju and parameterized them in terms of temporal availability to incorporate into the population model. The contribution of host plants for the population growth of B. dorsalis in the selected site was different according to the group of host plants. For example, B. dorsalis populations largely decreased by 93%, when host plants belong to Moraceae (mainly Ficus sp.) were removed in the simulation. Also, we found that the host plants of Prunus persica, Ficus carica, P. mume, Eriobotrya japonica in this order contributed greatly to population abundance of B. dorsalis in the selected area, which was important in terms of mid-season host plants connecting the early adult population of B. dorsalis to citrus plants in the late season. Finally, we discussed a seasonal management strategy against B. dorsalis while considering the availability of host plants and the biology of this fruit fly in an invaded area.     

How plant allometry influences bud phenology and fruit yield in two Vaccinium species

Background and AimsUnderstanding how plant allometry, plant architecture and phenology contribute to fruit production can identify those plant traits that maximize fruit yield. In this study, we compared these variables and fruit yield for two shrub species, Vaccinium angustifolium and Vaccinium myrtilloides, to test the hypothesis that phenology is linked to the plants’ allometric traits, which are predictors of fruit production.MethodsWe measured leaf and flower phenology and the above-ground biomass of both Vaccinium species in a commercial wild lowbush blueberry field (Quebec, Canada) over a 2-year crop cycle; 1 year of pruning followed by 1 year of harvest. Leaf and flower phenology were measured, and the allometric traits of shoots and buds were monitored over the crop cycle. We hand-collected the fruits of each plant to determine fruit attributes and biomass.Key ResultsDuring the harvesting year, the leafing and flowering of V. angustifolium occurred earlier than that of V. myrtilloides. This difference was related to the allometric characteristics of the buds due to differences in carbon partitioning by the plants during the pruning year. Through structural equation modelling, we identified that the earlier leafing in V. angustifolium was related to a lower leaf bud number, while earlier flowering was linked to a lower number of flowers per bud. Despite differences in reproductive allometric traits, vegetative biomass still determined reproductive biomass in a log–log scale model.ConclusionsGrowing buds are competing sinks for non-structural carbohydrates. Their differences in both number and characteristics (e.g. number of flowers per bud) influence levels of fruit production and explain some of the phenological differences observed between the two Vaccinium species. For similar above-ground biomass, both Vaccinium species had similar reproductive outputs in terms of fruit biomass, despite differences in reproductive traits such as fruit size and number.     

Integrative modelling of animal movement: incorporating in situ habitat and behavioural information for a migratory marine predator

A fundamental goal in animal ecology is to quantify how environmental (and other) factors influence individual movement, as this is key to understanding responsiveness of populations to future change. However, quantitative interpretation of individual-based telemetry data is hampered by the complexity of, and error within, these multi-dimensional data. Here, we present an integrative hierarchical Bayesian state-space modelling approach where, for the first time, the mechanistic process model for the movement state of animals directly incorporates both environmental and other behavioural information, and observation and process model parameters are estimated within a single model. When applied to a migratory marine predator, the southern elephant seal (Mirounga leonina), we find the switch from directed to resident movement state was associated with colder water temperatures, relatively short dive bottom time and rapid descent rates. The approach presented here can have widespread utility for quantifying movement–behaviour (diving or other)–environment relationships across species and systems.     

Influence of Host Plant Structure and Microclimate on the Abundance and Behavior of a Tephritid Fly

Microclimate and host plant architecture significantly influence the abundance and behavior of insects. However, most research in this field has focused at the invertebrate assemblage level, with few studies at the single-species level. Using wild Solanum mauritianum plants, we evaluated the influence of plant structure (number of leaves and branches and height of plant) and microclimate (temperature, relative humidity, and light intensity) on the abundance and behavior of a single insect species, the monophagous tephritid fly Bactrocera cacuminata (Hering). Abundance and oviposition behavior were signficantly influenced by the host structure (density of foliage) and associated microclimate. Resting behavior of both sexes was influenced positively by foliage density, while temperature positively influenced the numbers of resting females. The number of ovipositing females was positively influenced by temperature and negatively by relative humidity. Feeding behavior was rare on the host plant, as was mating. The relatively low explanatory power of the measured variables suggests that, in addition to host plant architecture and associated microclimate, other cues (e.g., olfactory or visual) could affect visitation and use of the larval host plant by adult fruit flies. For 12 plants observed at dusk (the time of fly mating), mating pairs were observed on only one tree. Principal component analyses of the plant and microclimate factors associated with these plants revealed that the plant on which mating was observed had specific characteristics (intermediate light intensity, greater height, and greater quantity of fruit) that may have influenced its selection as a mating site.     

Presence of the endosymbiont Wolbachia among some fruit flies (Diptera: Tephritidae) from Iran: A multilocus sequence typing approach

Wolbachia is a widespread endosymbiont of insects with a diverse range of biological effects on its hosts. We studied the prevalence of Wolbachia in some important species of tephritids in Iran. Among different populations of five fruit fly species, Dacus ciliatus (cucurbit fly), Rhagoletis cerasi (cherry fruit fly), Ceratitis capitata (Mediterranean fruit fly), Myiopardalis pardalina (melon fly) and Carypomya vesuviana (jujube fly), two species, R. cerasi and C. vesuviana, showed infection with separate Wolbachia strains, namely wCer6 and wVes1, respectively. C. vesuviana is introduced here as a novel host for Wolbachia. Genotyping of Wolbachia strains in 12 populations of five fruit fly species, using multilocus sequence typing (MLST) and the wsp gene sequence showed the occurrence of two new strains as well as a new strain type (ST) belonging to the A supergroup. On the basis of the results of this study, 12 barcodes under five species of Iranian tephritids have been added to the database of DNA barcodes. Inter- and intra-specific differences among COI sequences showed a clear gap in barcoding among most fruit flies.     

Movement ecology and sex are linked to barn owl microbial community composition

The behavioural ecology of host species is likely to affect their microbial communities, because host sex, diet, physiology, and movement behaviour could all potentially influence their microbiota. We studied a wild population of barn owls (Tyto alba) and collected data on their microbiota, movement, diet, size, coloration, and reproduction. The composition of bacterial species differed by the sex of the host and female owls had more diverse bacterial communities than their male counterparts. The abundance of two families of bacteria, Actinomycetaceae and Lactobacillaceae, also varied between the sexes, potentially as a result of sex differences in hormones and immunological function, as has previously been found with Lactobacillaceae in the microbiota of mice. Male and female owls did not differ in the prey they brought to the nest, which suggests that dietary differences are unlikely to underlie the differences in their microbiota. The movement behaviour of the owls was associated with the host microbiota in both males and females because owls that moved further from their nest each day had more diverse bacterial communities than owls that stayed closer to their nests. This novel result suggests that the movement ecology of hosts can impact their microbiota, potentially on the basis of their differential encounters with new bacterial species as the hosts move and forage across the landscape. Overall, we found that many aspects of the microbial community are correlated with the behavioural ecology of the host and that data on the microbiota can aid in generating new hypotheses about host behaviour.     

Host genetics and pathogen species modulate infection-induced changes in social aggregation behaviour

Identifying how infection modifies host behaviours that determine social contact networks is important for understanding heterogeneity in infectious disease dynamics. Here, we investigate whether group social behaviour is modified during bacterial infection in fruit flies (Drosophila melanogaster) according to pathogen species, infectious dose, host genetic background and sex. In one experiment, we find that systemic infection with four different bacterial species results in a reduction in the mean pairwise distance within infected female flies, and that the extent of this change depends on pathogen species. However, susceptible flies did not show any evidence of avoidance in the presence of infected flies. In a separate experiment, we observed genetic- and sex-based variation in social aggregation within infected, same-sex groups, with infected female flies aggregating more closely than infected males. In general, our results confirm that bacterial infection induces changes in fruit fly behaviour across a range of pathogen species, but also highlight that these effects vary between fly genetic backgrounds and can be sex-specific. We discuss possible explanations for sex differences in social aggregation and their consequences for individual variation in pathogen transmission.     

Impact of individual movement and changing resource availability on male–female encounter rates in an herbivorous insect

Species often confront changing resource distributions that result from natural and anthropogenic processes. For species that reproduce on or in close association with particular resources (e.g. host plants), changing resource distributions could affect the success of mate finding. We examine how mate-finding behaviours in an herbivorous insect mediate the impact of changing host plant spatial distribution. We tracked movements of 84 Melissa blue butterflies (Lycaeides melissa) in the Great Basin of western North America. Track data revealed sex differences in movement: males spent more time moving fast and females more time moving slowly; males moved more ballistically and females moved more diffusely. These differences vary quantitatively, but not qualitatively, between environments with contrasting resource distributions.From these data we created and parameterised a computer model of male–female encounters and used it to examine implications of changes to the patchiness and abundance of host plants. We use the cumulative encounter time between each simulated male–female pair as a proxy for mating success, thus allowing for the consideration of different female behaviours. The simulations suggest observed movement parameters exist in a trade-off between individuals maximising the number of potential mates they encounter and the probability that each encounter leads to mating success. Increasing host plant abundance decreases encounter rates thus encouraging males to be more diffuse to compensate. Changing the local resource density, i.e. increasing host plant patchiness, accentuated these trade-offs: by decreasing cumulative encounter time in resource rich environments and increasing it in resource sparse ones. Thus we see that both spatial resource geometry at multiple scales and plasticity in male movement strategies are important factors to consider when seeking to understand population reproductive behaviour, for example when assessing ecological impact of development, determining range boundaries and slowing invasions or outbreaks.     

Comparative demography of a specialist and generalist fruit fly: Implications for host use and pest management

Host plants used by phytophagous insects can have significant consequences on demography parameters, overall lifetime fitness and their subsequent population dynamics. Here, we conduct a comparative demographic study between the specialist Zeugodacus cucumis (French) and generalist Bactrocera tryoni (Froggatt) (Diptera: Tephritidae) to determine whether the host plants used by these fly species play any role in their overall lifetime fitness and explains current host use patterns. These two fly species are pests within the north-eastern region of Australia and we further aimed to use complete life-history data to determine the population parameters and models that would help identify the sensitive life-history stage that could be targeted for effective field management. Eggs collected from laboratory-reared flies were inoculated into organically grown fruits of both the primary and alternate host plant cultivars of both fly species. The proportion surviving each life stage from egg through to adult and fecundity were monitored for all cohorts from the different plant cultivars. Complete stage-base life-tables for cohorts of each fly species developing from each fruit cultivar were constructed, and the key demographic parameters and population models were analysed using PopTools matrix model programme. Our results showed that the host used by each fly species had significant consequences on fly demographic parameters and hence their overall lifetime fitness. The generalist B. tryoni was able to compensate for the fitness loss experienced at the pre-adult stage by having adults with higher fecundity, but this was not the case for the specialist Z. cucumis. Stage-base population models revealed that the population growth rate of both species was highly sensitive at the adult reproductive stage, indicating that manipulating probability of survival at this life stage would effectively manage populations of these pest species. This study provides the empirical evidence of undertaking complete life history demography studies of phytophagous insects to accurately understand their lifetime fitness consequences of using a certain host, their observed host use patterns, and overall population dynamics. We suggest that any efforts to manage dacine fruit fly pest population should consider life-history consequences of host use.     

A canopy architectural model to study the competitive ability of chickpea with sowthistle

Background and Aims

Improving the competitive ability of crops is a sustainable method of weed management. This paper shows how a virtual plant model of competition between chickpea (Cicer arietinum) and sowthistle (Sonchus oleraceus) can be used as a framework for discovering and/or developing more competitive chickpea cultivars.

Methods

The virtual plant models were developed using the L-systems formalism, parameterized according to measurements taken on plants at intervals during their development. A quasi-Monte Carlo light-environment model was used to model the effect of chickpea canopy on the development of sowthistle. The chickpea–light environment–sowthistle model (CLES model) captured the hypothesis that the architecture of chickpea plants modifies the light environment inside the canopy and determines sowthistle growth and development pattern. The resulting CLES model was parameterized for different chickpea cultivars (viz. ‘Macarena’, ‘Bumper’, ‘Jimbour’ and ‘99071-1001’) to compare their competitive ability with sowthistle. To validate the CLES model, an experiment was conducted using the same four chickpea cultivars as different treatments with a sowthistle growing under their canopy.

Results and Conclusions

The growth of sowthistle, both in silico and in glasshouse experiments, was reduced most by ‘99071-1001’, a cultivar with a short phyllochron. The second rank of competitive ability belonged to ‘Macarena’ and ‘Bumper’, while ‘Jimbour’ was the least competitive cultivar. The architecture of virtual chickpea plants modified the light inside the canopy, which influenced the growth and development of the sowthistle plants in response to different cultivars. This is the first time that a virtual plant model of a crop–weed interaction has been developed. This virtual plant model can serve as a platform for a broad range of applications in the study of chickpea–weed interactions and their environment.Key words: Plant architecture, virtual plant modelling, L-systems formalism, crop/weed competition, integrated weed management, chickpea, Cicer arietinum, sowthistle, Sonchus oleraceus     

Host shifts in economically significant fruit flies (Diptera: Tephritidae) with high degree of polyphagy

Insects tend to feed on related hosts. Coevolution tends to be dominated by interactions resulting from plant chemistry in defense strategies, and evolution of secondary metabolisms being in response to insect herbivory remains a classic explanation of coevolution. The present study examines whether evolutionary constraints existing in host associations of economically important fruit flies in the species‐rich tribe Dacini (Diptera: Tephritidae) and to what extent these species have evolved specialized dietary patterns. We found a strong effect of host phylogeny on associations on the 37 fruit flies tested, although the fruit fly species feeding on ripe commercially grown fruits that lost the toxic compounds after long‐term domestication are mostly polyphagous. We assessed the phylogenetic signal of host breadth across the fruit fly species, showing that the results were substantially different depending on partition levels. Further, we mapped main host family associations onto the fruit fly phylogeny and Cucurbitaceae has been inferred as the most likely ancestral host family for Dacini based on ancestral state reconstruction.     

A novel satiety sensor detects circulating glucose and suppresses food consumption via insulin-producing cells in Drosophila

Sensing satiety is a crucial survival skill for all animal species including human. Despite the discovery of numerous neuromodulators that regulate food intake in Drosophila, the mechanism of satiety sensing remains largely elusive. Here, we investigated how neuropeptidergic circuitry conveyed satiety state to influence flies’ food consumption. Drosophila tackykinin (DTK) and its receptor TAKR99D were identified in an RNAi screening as feeding suppressors. Two pairs of DTK⁺ neurons in the fly brain could be activated by elevated D-glucose in the hemolymph and imposed a suppressive effect on feeding. These DTK⁺ neurons formed a two-synapse circuitry targeting insulin-producing cells, a well-known feeding suppressor, via TAKR99D⁺ neurons, and this circuitry could be rapidly activated during food ingestion and cease feeding. Taken together, we identified a novel satiety sensor in the fly brain that could detect specific circulating nutrients and in turn modulate feeding, shedding light on the neural regulation of energy homeostasis.Subject terms: Calcium signalling, Nutrient signalling     

Globalization and fruitfly invasion and expansion: the medfly paradigm

The phytophagous insects of the Tephritidae family commonly referred to as “true fruit flies” offer different case histories of successful invasions. Mankind has played an important role in altering the distributions of some of the more polyphagous and oligophagous species. However, the question arises why only a few species have become major invaders. The understanding of traits underlying adaptation in different environments is a major topic in invasion biology. Being generalists or specialists, along the K–r gradient of the growth curve, make a difference in term of food resources exploitation and interspecies competition and displacement. The species of the genus Ceratitis are good examples of r-strategists. The genetic and biological data of the most notorious Ceratitis species, the Mediterranean fruit fly Ceratitis capitata (medfly), are reviewed to investigate the traits and behaviours that make the medfly an important invader. It can be learnt from medfly, that invasions in a modern global trade network tend to be due to multiple introductions. This fact allows a maintenance or enhancement of genetic variability in the adventive populations, which in turn increases their potential invasiveness. Our current knowledge of the medfly genome opens the way for future studies on functional genomics.     

Physiological state influences the antennal response of Anastrepha obliqua to male and host volatiles

The sexual and host‐related behaviours of the fruit fly Anastrepha obliqua Macquart (Diptera: Tephritidae) are mediated by volatile compounds. However, whether the physiological state of this species affects its antennal and behavioural responses to semiochemicals is unknown. The effects of age, mating status, diet and the topical application of methoprene, a Juvenile hormone analogue (JHA), on the antennal sensitivity of this tephritid fruit fly species to selected male [(Z)‐3‐nonenol] and host fruit volatiles (ethyl benzoate, ethyl hexanoate, ethyl butyrate and trans‐β‐ocimene) are investigated using electroantennography (EAG). Overall, (Z)‐3‐nonenol and ethyl benzoate elicit the highest EAG responses in both sexes. Flies of both sexes aged 1, 5 and 10 days old show higher EAG responses to the tested compounds compared with flies aged 20 days old. Virgin females and males show higher EAG responses to volatile compounds than mated flies. Females and males fed with sugar plus protein show higher antennal responses to volatiles compared with flies fed sugar or protein alone. Flies of both sexes treated with methoprene show higher antennal responses than flies treated with acetone (control). These results suggest that the peripheral olfactory system in A. obliqua is modulated by the physiological state of the flies.     

Commentary: Spermidine-triggered autophagy ameliorates memory during aging

The aging process drives the progressive deterioration of an organism and is thus subject to a complex interplay of regulatory and executing mechanisms. Our understanding of this process eventually aims at the delay and/or prevention of age-related pathologies, among them the age-dependent decrease in cognitive performance (e.g., learning and memory). Using the fruit fly Drosophila melanogaster, which combines a generally high mechanistic conservation with an efficient experimental access regarding aging and memory studies, we have recently unveiled a protective function of polyamines (including spermidine) against age-induced memory impairment (AMI). The flies’ age-dependent decline of aversive olfactory memory, an established model for AMI, can be rescued by both pharmacological treatment with spermidine and genetic modulation that increases endogenous polyamine levels. Notably, we find that this effect strictly depends on autophagy, which is remarkable in light of the fact that autophagy is considered a key regulator of aging in other contexts. Given that polyamines in general and spermidine in particular are endogenous metabolites, our findings place them as candidate target substances for AMI treatment.