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Appropriate preferences for light or dark conditions can be crucial for an animal's survival. Innate light preferences are not static in some animals, including the fruit fly Drosophila melanogaster, which prefers darkness in the feeding larval stage but prefers light in adulthood. To elucidate the neural circuit underlying light preference, we examined the neurons involved in larval phototactic behavior by regulating neuronal functions. Modulating activity of two pairs of isomorphic neurons in the central brain switched the larval light preference between photophobic and photophilic. These neurons were found to be immediately downstream of pdf-expressing lateral neurons, which are innervated by larval photoreceptors. Our results revealed a neural mechanism that could enable the adjustment of animals' response strategies to environmental stimuli according to biological needs. 10.1126/science.1195993

Genes and prior experience both influence the behavior of animals, but the relative contribution of each to fighting behavior in Drosophila remains unclear. To address this issue, we bred hyperaggressive flies by selecting winners of fights over 34-37 generations. Males of this strain initiate fights sooner, retaliate more often, and regularly defeat opponents from the nonselected parent Canton-S strain. After a defeat, however, these highly aggressive flies lose their second fights against socially naive counterparts. Defeated flies also lunge and retaliate less after experiencing a loss, suggesting that the subsequent losses result from flies becoming less aggressive. Remarkably, flies that were once capable of engaging in high-intensity boxing and tussling patterns of behavior for extended periods of time often do not even engage in mid-intensity lunging after a single defeat. Furthermore, these formerly highly aggressive flies lose all competitive advantage over nonselected Canton-S after experiencing a loss. Lastly, females were more likely to copulate with males from the nonselected parent line than with the hyperaggressive strain. behavior | fighting | flies | learning | memory doi/10.1073/pnas.1007016107

Olfactory responses of Drosophila undergo pronounced changes after eclosion. The flies develop attraction to odors to which they are exposed and aversion to other odors. Behavioral adaptation is correlated with changes in the firing pattern of olfactory receptor neurons (ORNs). In this article, we present an information-theoretic analysis of the firing pattern of ORNs. Flies reared in a synthetic odorless medium were transferred after edosion to three different media: (i) a synthetic medium relatively devoid of odor cues, (ii) synthetic medium infused with a single odorant, and (iii) complex cornmeal medium rich in odors. Recordings were made from an identified sensillum (type II), and the Jensen--Shannon divergence (Dis) was used to assess quantitatively the differences between ensemble spike responses to different odors. Analysis shows that prolonged exposure to ethyl acetate and several related esters increases sensitivity to these esters but does not improve the ability of the fly to distinguish between them. Flies exposed to cornmeal display varied sensitivity to these odorants and at the same time develop greater capacity to distinguish between odors. Deprivation of odor experience on an odorless synthetic medium leads to a loss of both sensitivity and acuity. Rich olfactory experience thus helps to shape the ORNs response and enhances its discriminative power. The experiments presented here demonstrate an experience-dependent adaptation at the level of the receptor neuron. imaginal conditioning | sensory adaptation | odor imprinting | Jensen-Shannon divergence | chemo receptor tuning www.pnas.org/cgi/doi/10.1073/pnas.1003856107

Selection of appropriate oviposition sites is essential for progeny survival and fitness in generalist insect species, such as Drosphila melanogaster, yet little is known about the mechanisms regulating how environmental conditions and innate adult preferences are evaluated and balanced to yield the final substrate choice for egg-deposition. Female D. melanogaster are attracted to food containing acetic acid (AA) as an oviposition substrate. However, our observations reveal that this egg-laying preference is a complex process, as it directly opposes an otherwise strong, default behavior of positional avoidance for the same food. We show that 2 distinct sensory modalities detect AA. Attraction to AA-containing food for the purpose of egg-laying relies on the gustatory system, while positional repulsion depends primarily on the olfactory system, Similarly, distinct central brain regions are involved in AA attraction and repulsion. Given this unique situation, in which a single environmental stimulus yields 2 opposing behavioral outputs, we propose that the interaction of egg-laying attraction and positional aversion for AA provides a powerful model for studying how organisms balance competing behavioral drives and integrate signals involved in choice-like processes. choice behavior | gustatory system | olfactory system | mushroom body | ellipsoid body

Aggressive behavior is observed across animal taxa and is likely to be evolutionarily conserved. Although potentially advantageous, aggression can have social and health consequences in humans, and is a component of a number of psychiatric disorders. As a complex genetic trait, it is modulated by numerous quantitative trait loci (QTL) with allelic effects that can vary in direction and magnitude and that are sensitive to environmental perturbations. Assays to quantify aggressive behavior in Drosophila melanogaster have been developed, making this an ideal model system in which to dissect the genomic architecture underlying manifestation of and variation in aggressive behavior. Here, we map QTL affecting variation in aggression between two wild-Lype Drosophila strains. We identified a minimum of five QTL in a genomewide scan: two on chromosome 2 and three on chromosome 3. At least three and possibly all five of these QTL interact epistatically. We used deficiency complementation mapping to subdivide two linked, epistatically interacting QTL of large effect on chromosome 3 into at least six QTL, and complementation tests to mutations identified four candidate quantitative trait genes. Extensive epistasis poses a serious challenge for understanding the genetic basis of complex traits. DOI: 10.1534/genetics.109.101691

In fewer than two decades after invading the Americas, the European fly Drosophila subobscura evolved latitudinal clines in several traits. Moreover, its chromosomal inversion frequencies at given localities have shifted with climate warming. Temperature may have driven the evolution of both geographic clines and within-site shifts. Nevertheless, whether body temperature ([T.sub.b]) of active flies actually varies geographically and temporally is unknown: if these flies are effective behavioral thermoregulators, they might maintain relatively constant [T.sub.b] when active, independent of season and latitude. To evaluate these possibilities, we monitored activity and estimated [T.sub.b] of active flies in all seasons and at five sites (3[gamma]-49[degrees] N) in western North America. Latitudinal and seasonal shifts in activity are conspicuous. Flies have longer activity seasons (and are much more active) at higher latitudes. Flies are generally active only at midday in cool seasons, and only early and late in the day (if active at all) in warm seasons. Despite these behavioral shifts active flies have much lower [T.sub.b] in cooler seasons and at higher latitudes. The observed pattern is consistent with the hypothesis that geographic shifts in [T.sub.b] may be an evolutionary driver of latitudinal clines in this invading species. Key words: body temperature; Drosophila subobscura; European fruit fly; invasive species; latitudinal clines; North America; thermoregulation.

Improved survival is likely linked to the ability to generate stable memories of significant experiences. Considerable evidence in humans and mammalian model animals shows that steroid hormones, which are released in response to emotionally arousing experiences, have an important role in the consolidation of memories of such events. In insects, ecdysone is the major steroid hormone, and it is well characterized with respect to its essential role in coordinating developmental transitions such as larval molting and metamorphosis. However, the functions of ecdysone in adult physiology remain largely elusive. Here, we show that 20-hydroxyecdysone (20E), the active metabolite of ecdysone that is induced by environmental stimuli in adult Drosophila, has an important role in the formation of long-term memory (LTM). in male flies, the levels of 20E were found to be significantly increased after courtship conditioning, and exogenous administration of 20E either enhanced or suppressed courtship LTM, depending on the timing of its administration. We also found that mutants in which ecdysone signaling is reduced were defective in LTM, and that an elevation of 20E levels was associated with activation of the cAMP response element binding protein (CREB), an essential regulator of LTM formation. Our results demonstrate that the molting steroid hormone ecdysone in adult Drosophila is critical to the evolutionarily conserved strategy that is used for the formation of stable memories. We propose that ecdysone is able to consolidate memories possibly by recapturing molecular and cellular processes that are used for normal neural development. courtship conditioning | CREB | ecdysone receptor | steroid hormone | 20-hydroxyecdysone

Diapause is the classic adaptation to seasonality in arthropods, and its expression can result in extreme lifespan extension as well as enhanced resistance to environmental challenges. Little is known about the underlying evolutionary genetic architecture of diapause in any organism. Drosophila melanogaster exhibits a reproductive diapause that is variable within and among populations; the incidence of diapause increases with more temperate climates and has significant pleiotropic effects on a number of life history traits. Using quantitative trait mapping, we identified the RNA-binding protein encoding gene couch potato (cpo) as a major genetic locus determining diapause phenotype in D. melanogaster and independently confirmed this ability to impact diapause expression through genetic complementation mapping. By sequencing this gene in samples from natural populations we demonstrated through linkage association that variation for the diapause phenotype is caused by a single Lys/lle substitution in one of the six cpo transcripts. Complementation analyses confirmed that the identified amino acid variants are functionally distinct with respect to diapause expression, and the polymorphism also shows geographic variation that closely mirrors the known latitudinal cline in diapause incidence. Our results suggest that a naturally occurring amino acid polymorphism results in the variable expression of a diapause syndrome that is associated with the seasonal persistence of this model organism in temperate habitats. cline | diapause | life history | mapping | tradeoff

In Drosophila melanogaster, the genetic and molecular bases of post-mating changes in the female's behavior and physiology are poorly understood. However, DNA microarray studies have demonstrated that, shortly after mating, transcript abundance of >1700 genes is altered in the female's reproductive tract as well as in other tissues. Many of these changes are elicited by sperm and seminal fluid proteins (Acps) that males transfer to females. To further dissect the transcript-level changes that occur following mating, we examined gene expression profiles of whole female flies at four time points following copulation. We found that, soon after copulation ends, a large number of small-magnitude transcriptional changes occurred in the mated female. At later time points, larger magnitude changes were seen, although these occurred in a smaller number of genes. We then explored how four individual Acps (ovulin, Acp36DE, Acp29AB, and Acp62F) with unique functions independently affected gene expression in females shortly after mating. Consistent with their early and possibly local action within the female, ovulin and Acp36DE caused relatively few gene expression changes in whole bodies of mated females. In contrast, Acp29AB and Acp62F modulated a large number of transcriptional changes shortly after mating.

In mammals and insects, pheromones strongly influence social behaviors such as aggression and mate recognition. In Drosophila melanogaster, pheromones in the form of cuticular hydrocarbons play prominent roles in courtship. GC/MS is the primary analytical tool currently used to study Drosophila cuticular hydrocarbons. Although GC/MS is highly reproducible and sensitive, it requires that the fly be placed in a lethal solution of organic solvent, thereby impeding further behavioral studies. We present a technique for the analysis of hydrocarbons and other surface molecules from live animals by using direct analysis in real-time (DART) MS. Cuticular hydrocarbons were sampled from the surface of a restrained, awake behaving fly by using several brief, carefully controlled depressions of the abdomen with a small steel probe. DART mass spectral analysis of the probe detected ions with mass-to-charge ratio (m/z) of the protonated molecule corresponding to many of the previously identified unsaturated hydrocarbons. Six additional cuticular hydrocarbons also were identified. Consistent with previous GC/MS studies, male and female differences in chemical composition were evident. Spatial differences in the expression profile also were observed on males. Sampling from an individual female first as a virgin and then 45 and 90 min after successful copulation showed that mass signals likely to correspond to cis-vaccenyl acetate, tricosene, and pentacosene increased in relative intensity after courtship. This method provides near-instantaneous analysis of an individual animal's chemical profile in parallel with behavioral studies and could be extended to other models of pheromone-mediated behavior. behavior | cis-vaccenyl acetate | courtship | pheromones | Drosophila

How the brain perceives volatile chemicals in the environment to evoke the appropriate behaviour is a fundamental question in sensory neuroscience. The olfactory system of the fruit fly, Drosophila melanogaster, has emerged as a powerful model system to address this problem. Recent analysis of the molecular, neuroanatomical and physiological properties of the olfactory circuits that detect the sex and social aggregation pheromone cis-vaccenyl acetate now provides one of the most comprehensive outlines for the neural basis of odour perception. This review describes these latest advances, discusses what they reveal about where stimulus sensitivity and specificity is encoded in olfactory circuits, and considers future questions.

The light preferences of fruit flies were tested by 2 different means. First, flies were allowed to choose between different illuminations, and their favorite resting, grooming, and feeding places were determined with an infrared-sensitive camera. Second, the activity levels of the animals during their main daily activity period were determined photoelectrically (via infrared light beams) under different light intensities. Both methods revealed that the flies prefer dim light. They rested, groomed, and fed preferentially in places with a light intensity between 5 and 10 lux, and they showed the highest activity level when the light intensity during the day was kept at 10 lux. Furthermore, when dawn and dusk were simulated by logarithmically increasing/decreasing the light intensity during a 1.5-h interval, the flies' activity maxima occurred at about 7.5 lux during early dawn and late dusk. The results suggest that fruit flies time their clocks by early dawn and late dusk and avoid bright light during the day. Key words diurnal rhythms, dawn and dusk, dim light, Drosophila melanogaster, activity, feeding., The fruit fly Drosophila melanogaster is one of the preferential model organisms to study diurnal and circadian rhythms. As with many animals (Aschoff, 1966), fruit flies show bimodal activity patterns [...]

Extensive neurogenetic analysis has shown that memory formation depends critically on cAMP-protein kinase A (PKA) signaling. Details of how this pathway is involved in memory formation, however, remain to be fully elucidated. From a large-scale behavioral screen in Drosophila, we identified the yu mutant to be defective in one-day memory after spaced training. The yu mutation disrupts a gene encoding an A-kinase anchoring protein (AKAP). AKAPs comprise a family of proteins, which determine the subcellular localization of PKAs and thereby critically restrict cAMP signaling within a cell. Further behavioral characterizations revealed that long-term memory (LTM) was disrupted specifically in the yu mutant, whereas learning, short-term memory and anesthesia-resistant memory all appeared normal. Another independently isolated mutation of the yu gene failed to complement the LTM defect associated with the yu mutation, and this phenotypic defect could be rescued by induced acute expression of a [yu.sup.+] transgene, suggesting that yu functions physiologically during memory formation. AKAP Yu is expressed preferentially in the mushroom body (MB) neuroanatomical structure, and expression of a [yu.sup.+] transgene to the MB, but not to other brain regions, is sufficient to rescue the LTM defect of the yu mutant. These observations lead us to conclude that proper localization of PKA by Yu AKAP in MB neurons is required for the formation of LTM. A-kinase anchoring protein | cAMP pathway | mushroom body | olfactory memory

Behaviors are complex traits influenced by multiple pleiotropic genes. Understanding the mechanisms that give rise to complex behaviors requires an understanding of how variation in transcriptional regulation shapes nervous system development and how variation in brain structure influences an organism's ability to respond to its environment. To begin to address this problem, we used olfactory behavior in Drosophila melanogaster as a model and showed that a hypomorphic transposon-mediated mutation of the early developmental gene Semaphorin-5c (Sema-5c) results in aberrant behavioral responses to the repellant odorant benzaldehyde. We fine mapped this effect to the Sema-5c locus using deficiency mapping, phenotypic reversion through P-element excision, and transgenic rescue. Morphometric analysis of this Sema5c allele reveals subtle neuroanatomical changes in the brain with a reduction in the size of the ellipsoid body. High-density oligonucleotide expression microarrays identified 50 probe sets with altered transcriptional regulation in the Sema-5c background and quantitative complementation tests identified epistatic interactions between nine of these coregulated genes and the transposon-disrupted Sema-5c gene. Our results demonstrate how hypomorphic mutation of an early developmental gene results in genomewide transcriptional consequences and alterations in brain structure accompanied by profound impairment of adult behavior.

Male Drosophila melanogaster (Canton-S strain) exhibit aggression in competition for resources, to defend territory, and for access to mates. In the study reported here, we asked: (i) how long flies fight; (ii) whether flies adopt distinct winning and losing strategies as hierarchical relationships are established; (iii) whether flies exhibit experience-dependent changes in fighting strategies in later fights; and (iv) whether flies fight differently in second fights against familiar or unfamiliar opponents. The results showed that flies fought for up to 5 h. As hierarchical relationships were established, behavioral strategies changed: winners progressively lunged more and retreated less, whereas losers progressively lunged less and retreated more. Encounters between flies were frequent during the first 10 min of pairing and then dropped significantly. To ask whether flies remembered previous fights, they were re-paired with familiar or unfamiliar opponents after 30 rain of separation. In familiar pairings, there were fewer encounters during the first 10 min of fighting than in unfamiliar pairings, and former losers fought differently against familiar winners than unfamiliar winners. Former losers lost or no decision was reached in all second fights in pairings with familiar or unfamiliar winners or with naive flies. Winner/winner, loser/loser, and naive/naive pairings revealed that losers used low-intensity strategies in later fights and were unlikely to form new hierarchical relationships, compared with winners or socially naive flies. These results strongly support the idea that learning and memory accompany the changes in social status that result from fruit fly fights. behavior | dominance | fruit fly | social status | fighting

Locomotion is an integral component of most animal behaviors and many human diseases and disorders are associated with locomotor deficits, but little is known about the genetic basis of natural variation in locomotor behavior. Locomotion is a complex trait, with variation attributable to the joint segregation of multiple interacting quantitative trait loci (QTL), with effects that are sensitive to the environment. We assessed variation in a component of locomotor behavior (locomotor reactivity) in a population of 98 recombinant inbred lines of Drosophila melanogaster and mapped four QTL affecting locomotor reactivity by linkage to polymorphic roo transposable element insertion sites. We used complementation tests of deficiencies to fine map these QTL to 12 chromosomal regions and complementation tests of mutations to identify 13 positional candidate genes affecting locomotor reactivity, including Dopa decarboxylase (Ddc), which catalyzes the final step in the synthesis of serotonin and dopamine. Linkage disequilibrium mapping in a population of 164 second chromosome substitution lines derived from a single natural population showed that polymorphisms at Ddc were associated with naturally occurring genetic variation in locomotor behavior. These data implicate variation in the synthesis of bioamines as a factor contributing to natural variation in locomotor reactivity.

An investigation on whether levels of ancestral inbreeding in experimental populations of Drosophila melanogaster influence the magnitude of inbreeding depression is presented. Results reveal that high levels of ancestral inbreeding are associated with greater purging effects that reduce the inbreeding depression, which occurs in isolated populations of small size.

Equalization of parental contributions is one of the most simple and widely recognized methods to maintain genetic diversity in conservation programs, as it halves the rate of increase in inbreeding and genetic drift. It has, however, the negative side effect of implying a reduced intensity of natural selection so that deleterious genes are less efficiently removed from the population with possible negative consequences on the reproductive capacity of the individuals. Theoretical results suggest that the lower fitness resulting from equalization of family sizes relative to that for free contribution schemes is expected to be substantial only for relatively large population sizes and after many generations. We present a long-term experiment with Drosophila melanogaster, comparing the fitness performance of lines maintained with equalization of contributions (EC) and others maintained with no management (NM), allowing for free matings and contributions from parents. Two (five) replicates of size N = 100 (20) individuals of each type of line were maintained for 38 generations. As expected, EC lines retained higher gene diversity and allelic richness for four microsatellite markers and a higher heritability for sternopleural bristle number. Measures of life-history traits, such as egg-to-adult viability, mating success, and global fitness declined with generations, but no significant differences were observed between EC and NM lines. Our results, therefore, provide no evidence to suggest that equalization of family sizes entails a disadvantage on the reproductive capacity of conserved populations in comparison with no management procedures, even after long periods of captivity.

The larval brain of Drosophila is a useful model to study olfactory processing because of its cellular simplicity. The early stages of central olfactory processing involve the detection of odor features, but the coding mechanisms that transform them into a representation in higher brain centers is not clear. Here we examine the pattern of connectivity of the main neurons that process olfactory information in the calyx (dendritic region) of the mushroom bodies, a higher brain center essential for associative olfactory learning. The larval calyx has a glomerular organization. We generated a map of calyx glomeruli, using both anatomical criteria and the pattern of innervation by subsets of its input neurons (projection neurons), molecularly identified by GAL4 markers. Thus, we show that projection neurons innervate calyx glomeruli in a stereotypic manner. By contrast, subsets of mushroom body neurons (Kenyon cells) that are labeled by GAL4 markers show no clear preference for specific glomeruli. Clonal subsets of Kenyon cells show some preference for subregions of the calyx, implying that they receive distinct input. However, at the level of individual glomeruli, dendritic terminals of larval-born Kenyon ceils innervate about six glomeruli, apparently randomly. These results are consistent with a model in which Kenyon ceils process olfactory information by integrating different inputs from several calyx glomeruli in a combinatorial manner. Kenyon cells | MARCM | olfactory learning | projection neurons | antennal lobe

The dorsal air sacs supply oxygen to the flight muscles of the Drosophila adult. This tracheal organ grows from an epithelial robe (the air sac primordium (ASP)) that arises during the third larval instar (L3) from a wing-disc-associated tracheal branch. Since the ASP is generated by a program of both morphogenesis and cell proliferation and since the larval tracheal branches are populated by cells that are terminally differentiated, the provenance of its progenitors has been uncertain. Here, we show that, although other larval tracheae are remodeled after L3, most tracheal branches in the tracheal metamere associated with the wing disc (Tr2) are precociously repopulated with imaginal tracheoblasts during L3. Concurrently, the larval cells in Tr2 undergo head involution defective (hid)-dependent programmed cell death. In BX-C mutant larvae, the tracheal branches of the Tr3 metamere are also repopulated during L3. Our results show that repopulation of the larval trachea is a prerequisite for FGF-dependent induction of cell proliferation and tubulogenesis in the ASP and that homeotic selector gene function is necessary for the temporal and spatial control of tracheal repopulation. Keywords: Drosophila air sacs: Tracheal remodeling: Programmed cell death: BX-C

The variance and covariance between female mating preferences and sexually selected male traits studied in natural populations are rare. Substantial variation in the level of responsiveness allows low-quality males to achieve some mating success and counteract the build up of a strong genetic covariance between preferences and traits.

Five Drosophila melangaster recurrent F1s were used to investigate genotypic differences in space use and movement patterns, focusing on the behavior of teneral females and individually marked young adults that were allowed free access to large, structurally complex environments. Teneral females from the five F1s differed in their propensity to hide after emergence and in the height at which they perched above the substrate.

The intraspecific (within species) variation in the mate recognition systems and their mating behavior was studied. It was seen that the courtships of the 'mute' males proceeded in the same way as those of normal males and the male's wing vibration was still an important part of the courtship.

Drosophila is used as a model to examine interspecific variability in reproductive behaviors in a broad and comprehensive evolutionary framework. The potential sources and organization of genetic variability in the signals and sensory systems that receive and process them are analyzed to describe their evolution.

Recently, the fruit fly Drosophila melanogaster has been introduced as a model system to study the molecular bases of a variety of ethanol-induced behaviors. It became immediately apparent that the behavioral changes elicited by acute ethanol exposure are remarkably similar in flies and mammals. Flies show signs of acute intoxication, which range from locomotor stimulation at low doses to complete sedation at higher doses and they develop tolerance upon intermittent ethanol exposure. Genetic screens for mutants with altered responsiveness to ethanol have been carried out and a few of the disrupted genes have been identified. This analysis, while still in its early stages, has already revealed some surprising molecular parallels with mammals. The availability of powerful tools for genetic manipulation in Drosophila, together with the high degree of conservation at the genomic level, make Drosophila a promising model organism to study the mechanism by which ethanol regulates behavior and the mechanisms underlying the organism's adaptation to long-term ethanol exposure.

Micellar electrokinetic chromatography coupled to amperometric electrochemical detection was used to investigate the chemical environment of the fruit fly, Drosophila melanogaster. Preliminary studies focused on the employment and optimization of the system to separate electroactive amine-containing molecules present in the head and body of male and female flies. Ultimately, biogenic amines significant to the fly including L-3,4-dihydroxyphenylalanine, dopamine, tyramine, and serotonin were identified and their relative abundance quantified. Transgenic Drosophila with functionally ablated dopamine and serotonin neurons were analyzed to demonstrate the sensitivity of the technique. The separation method developed in this study should offer an advantage in elucidating the critical role that electroactive biogenic amines play in complex physiological processes correlated with Drosophila behavior.

Byline: N. A. Sitnik (1), E. V. Tokmacheva (1), E. V. Savvateeva-Popova (1) Keywords: Drosophila; mutants; central complex; mushroom bodies; conditioned reflex suppression of courtship Abstract: One of the most important questions in the genetics of behavior is that of studies of the mechanisms of learning and memory. A convenient system for this is provided by Drosophila melanogaster, in which a whole series of mutations affecting the formation of different types of memory and learning have been obtained. The brain formations involved in these processes have been studied in parallel. Attention is currently focused on two main structures: the central complex and the mushroom bodies. These mediate the integration and storage of information accumulating during the process of learning. Mutants with defects in individual parts of the central complex and mushroom bodies have been obtained. Mutants simultaneously affecting the operation, development, or structure of the central part of the cerebral neural ganglion and the ability to learn and form memory traces are of particular interest. We have evaluated the learning ability of mutants with defects in the central complex (cex .sup.KS181 and ccb .sup.KS127) and mutants with defects in the mushroom bodies (mud .sup.1, mbm .sup.1, and cxb .sup.N71), using a method based on the conditioned reflex suppression of courtship. Memory defects were seen in cex .sup.KS181 and mud .sup.1 mutants. Author Affiliation: (1) I. P. Pavlov Institute of Physiology, Russian Academy of Sciences, 6 Makarov Bank, 199034, St. Petersburg, Russia Article History: Registration Date: 12/10/2004

A task was designed to teach individual flies to avoid a lighted area after they had displayed an initial preference for it. The flies walked in a T-maze and chose between a lighted and a darkened alley leading, respectively, to a lighted and a darkened vial. Flies that were photopositive on a first trial were subjected to an aversive stimulus (a filter paper inserted into the lighted vial and wetted with a quinine solution), and they performed 16 training trials; they learned to avoid the lighted vial. The flies trained with water instead of quinine in the lighted vial still displayed avoidance of the lighted vial, but to a lesser extent The flies trained with a dry filter paper in the lighted vial did not show any increase in avoidance during training. Like the flies trained with no quinine at all, those trained to avoid the lighted vial under a partial reinforcement condition (one half of the trials with quinine, the other half with a dry vial) did not master the task. Finally, removal of the quinine after an avoidance acquisition criterion was reached resulted in an extinction process.

Most animals depend on olfaction for survival and procreation. Odor-guided behavior is a quantitative trait, with phenotypic variation due to multiple segregating quantitative trait loci (QTL). Despite its profound biological importance, the genetic basis of naturally occurring variation in olfactory behavior remains unexplored. Here, we mapped a single Drosophila QTL affecting variation in avoidance response to benzaldehyde, using a population of recombinant inbred lines. Deficiency complementation mapping resolved this region into one female- and one male-specific QTL. Subsequent quantitative complementation tests to all available mutations of positional candidate genes showed that the female-specific QTL failed to complement a P-element insertional mutation, l(3)04276. The P-element insertion was in the intron of a novel gene, Vanaso, which contains a putative guanylate binding protein domain, is highly polymorphic, and is expressed in the third antennal segment, the major olfactory organ of Drosophila. No expression was detected in the fly brain, suggesting that Vanaso plays a role in peripheral chemosensory processes rather than in central integration of olfactory information. QTL mapping followed by quantitative complementation tests to deficiencies and mutations is an effective strategy for gene discovery that allows characterization of effects of recessive lethal genes on adult phenotypes and here enabled identification of a candidate gene that contributes to sex-specific quantitative variation in olfactory behavior.

Previously, we generated P-element insert lines in Drosophila melanogasterwith impaired olfactory behavior. One of these smell-impaired (smi) mutants, smi60E, contains a P[lArB] transposon in the second intron of the dsc1 gene near a nested gene encoding the L41 ribosomal protein. The dsc1 gene encodes an ion channel of unknown function homologous to the paralytic (para) sodium channel, which mediates neuronal excitability. Complementation tests between the smi60E mutant and several EP insert lines map the smell-impaired phenotype to the P[lArB] insertion site. Wild-type behavior is restored upon P-element excision. Evidence that reduction in DSC1 rather than in L41 expression is responsible for the smell-impaired phenotype comes from a phenotypic revertant in which imprecise P-element excision restores the DSC1 message while further reducing L41 expression. Behavioral assays show that a threefold decrease in DSC1 mRNA is accompanied by a threefold shift in the dose response for avoidance of the repellent odorant, benzaldehyde, toward higher odorant concentrations. In situ hybridization reveals widespread expression of the dsc1 gene in the major olfactory organs, the third antennal segment and the maxillary palps, and in the CNS. These results indicate that the DSC1 channel contributes to processing of olfactory information during the olfactory avoidance response.

Despite the importance of aggression in the behavioral repertoire of most animals, relatively little is known of its proximate causation and control. To take advantage of modern methods of genetic analysis for studying this complex behavior, we have developed a quantitative framework for studying aggression in common laboratory strains of the fruit fly, Drosophila melanogaster. In the present study we analyze 73 experiments in which socially naive male fruit flies interacted in more than 2,000 individual agonistic interactions. This allows us to (i) generate an ethogram of the behaviors that occur during agonistic interactions; (ii) calculate descriptive statistics for these behaviors; and (iii) identify their temporal patterns by using sequence analysis. Thirty-minute paired trials between flies contained an average of 27 individual agonistic interactions, lasting a mean of 11 seconds and featuring a variety of intensity levels. Only few fights progressed to the highest intensity levels (boxing and tussling). A sequential analysis demonstrated the existence of recurrent patterns in behaviors with some similarity to those seen during courtship. Based on the patterns characterized in the present report, a detailed examination of aggressive behavior by using mutant strains and other techniques of genetic analysis becomes possible.

Drosophila melanogaster were studied to determine the significance of courtship conditioning, in which the males develop an avoidance response to females after initially courting. It was found that courtship conditioning is probably a behavior used in high-density populations in order to maintain fitness.

Research on walking speed, a phenotypic trait, is presented for Drosophila melanogaster, along with environmental and physiological factors affecting that trait. Overall, speed increased significantly with temperature, and with age for flies raised and living in low temperatures, but decreased for flies raised and living in intermediate or high temperatures.

Female mating frequency as a correlated response has been studied by looking at selection on age at reproduction in Drosophila melanogaster and fertility in the female. Results show that response to selection on age at reproduction has involved changes in scheduling of female reproductive behavior.

A new study investigates the influence of courtship song on the mate choice of female Drosophila melanogaster and Drosophila sechellia.

Research points out that in Drosophila, some ion channel genes exhibit specific A-to-I RNA editing mediated by the adenosine deaminase acting on RNA gene (ADAR) enzyme. Adult flies lacking ADAR show behavioral changes accompanied by neurodegeneration suggesting that A-to-I RNA editing of pre-mRNAs affects nervous system function.

A combined phenotypic and quantitative genetic study was conducted to determine which trait is responsible for the reproductive success in the Drosophila silvestris. The traits considered are aggressive success, courtship behavior and body size and shape. Results show that male D. silvestris that are more persistent in courting were more successful. However, traits that predicted courtship success did not show significant additive genetic variation.

The Drosophila courtship song is believed to be involved in sexual selection and species recognition. Previous studies have been based on an experimental design and in Drosophila montana, evidence suggests that males producing short sound pulses of high sound cycles have increased mating success. A further study supports such studies of male mating success, and confirms female song preference as a likely determinant of male mating success.

Wavelet decomposition and discrete Fourier transform were used to analyze the pulse portion of the mating song of the Drosophila melanogaster. Using these two new techniques, the presence of cycles in the interpulse intervals (IPI) of the pulse song of some individuals was confirmed and a significant effect of the per gene on cycling in IPI was found. Results shed light on courtship and species recognition, as well as on the interpretation of the nature of the circadian clock and the role of the per gene in the clock's mechanism and function.