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Insect Frontiers, June 2010 Volume 2 Number 6 （PDF final）
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Insect Behaviour
Synergy in information use for mate finding: demonstration in a parasitoid wasp
Marie Metzgera, Deborah Fischbeinb, 1, Alexandra Augustec, 2, Xavier Fauverguec, 2, Carlos Bernsteina and Emmanuel Desouhanta,
a CNRS, UMR 5558, Laboratoire de Biométrie et Biologie Evolutive, Université Lyon 1,
b Laboratorio de Ecología de Insectos Forestales INTA EEA Bariloche,
c UMR INRA-UNSA-CNRS 1301 ‘Interactions Biotiques et Santé Végétale’,
In many animals, mating takes place after natal dispersal. Consequently, use of reliable information is required to increase the probability of encounters between the sexes. Most of the studies on mate finding in parasitoid insects have focused on the role of a single information source: a sex pheromone. Other sources have been mostly ignored. We studied the nature of olfactory information used for mate finding by the parasitoid Venturia canescens both at a distance and at host patch level, and investigated how this information is used. We tested which sex attracts the other and whether mate location is improved by combining different sources of information. We found that males simultaneously used two types of olfactory cues to find their mate: information directly related to females and an environmental cue provided by hosts. Male efficiency in locating virgin females was enhanced threefold by the association of females with hosts, whereas host patches, on their own, were unattractive to males. Our results also suggest that females emit a volatile pheromone. At the host patch level, males used chemical marks left by females foraging for hosts. These results led us to consider the distinction between signals and cues and we suggest that the volatile pheromone emitted by the females, always described as a signal, could rather be a cue. Although evidence for a volatile sex pheromone is pervasive in parasitoids, our study stresses the role of other cues in mate-finding strategies.
Animal Behaviour Volume 79, Issue 6, June 2010, Pages 1307-1315
Insects running on elastic surfaces
Andrew J. Spence*, Shai Revzen
Department of Integrative Biology,
In nature, cockroaches run rapidly over complex terrain such as leaf litter. These substrates are rarely rigid, and are frequently very compliant. Whether and how compliant surfaces change the dynamics of rapid insect locomotion has not been investigated to date largely due to experimental limitations. We tested the hypothesis that a running insect can maintain average forward speed over an extremely soft elastic surface (10 N m–1) equal to 2/3 of its virtual leg stiffness (15 N m–1). Cockroaches Blaberus discoidalis were able to maintain forward speed (mean ± s.e.m., 37.2±0.6 cm s–1 rigid surface versus 38.0±0.7 cm s–1 elastic surface; repeated-measures ANOVA, P=0.45). Step frequency was unchanged (24.5±0.6 steps s–1 rigid surface versus 24.7±0.4 steps s–1 elastic surface; P=0.54). To uncover the mechanism, we measured the animal's centre of mass (COM) dynamics using a novel accelerometer backpack, attached very near the COM. Vertical acceleration of the COM on the elastic surface had a smaller peak-to-peak amplitude (11.50±0.33 m s–2, rigid versus 7.7±0.14 m s–2, elastic; P=0.04). The observed change in COM acceleration over an elastic surface required no change in effective stiffness when duty factor and ground stiffness were taken into account. Lowering of the COM towards the elastic surface caused the swing legs to land earlier, increasing the period of double support. A feedforward control model was consistent with the experimental results and provided one plausible, simple explanation of the mechanism.
Journal of Experimental Biology 213, 1907-1920 (2010)
http://jeb.biologists.org/cgi/content/abstract/213/11/1907
Insect Biochemistry
Mutations of an Arylalkylamine-N-acetyltransferase, Bm-iAANAT, Are Responsible for Silkworm Melanism Mutant*
Fang-yin Dai‡,1, Liang Qiao‡,1, Xiao-ling Tong‡§,1, Cun Cao‡, Peng Chen‡, Jun Chen‡, Cheng Lu‡,2 and Zhong-huai Xiang‡lucheng@swu.edu.cn
the §
Coloration is one of the most variable characters in animals and provides rich material for studying the developmental genetic basis of pigment patterns. In the silkworm, more than 100 gene mutation systems are related to aberrant color patterns. The melanism (mln) is a rare body color mutant that exhibits an easily distinguishable phenotype in both larval and adult silkworms. By positional cloning, we identified the candidate gene of the mln locus, Bm-iAANAT, whose homologous gene (Dat) converts dopamine into N-acetyldopamine, a precursor for N-acetyldopamine sclerotin in Drosophila. In the mln mutant, two types of abnormal Bm-iAANAT transcripts were identified, whose expression levels are markedly lower than the wild type (WT). Moreover, dopamine content was approximately twice as high in the sclerified tissues (head, thoracic legs, and anal plate) of the mutant as in WT, resulting in phenotypic differences between the two. Quantitative reverse transcription PCR analyses showed that other genes involved in the melanin metabolism pathway were regulated by the aberrant Bm-iAANAT activity in mln mutant in different ways and degrees. We therefore propose that greater accumulation of dopamine results from the functional deficiency of Bm-iAANAT in the mutant, causing a darker pattern in the sclerified regions than in the WT. In summary, our results indicate that Bm-iAANAT is responsible for the color pattern of the silkworm mutant, mln. To our knowledge, this is the first report showing a role for arylalkylamine-N-acetyltransferases in color pattern mutation in Lepidoptera.
The Journal of Biological Chemistry, 285, 19553-19560. June 18, 2010
http://www.jbc.org/content/285/25/19553.abstract
Molecular Mechanism That Induces Activation of Spätzle, the Ligand for the Drosophila Toll Receptor
Christopher J. Arnot, Nicholas J. Gay1 and Monique Gangloff2 njg11@cam.ac.uk mg308@cam.ac.uk
From the Department of Biochemistry, University of
The Drosophila Toll receptor is activated by an endogenous cytokine ligand Spätzle. Active ligand is generated in response to positional cues in embryonic dorso-ventral patterning and microbial pathogens in the insect immune response. Spätzle is secreted as a pro-protein and is processed into an active form by the serine endoproteases Easter and Spätzle-processing enzyme during dorso-ventral patterning and infection, respectively. Here, we provide evidence for the molecular mechanism of this activation process. We show that the Spätzle prodomain masks a predominantly hydrophobic region of Spätzle and that proteolysis causes a conformational change that exposes determinants that are critical for binding to the Toll receptor. We also gather that a conserved sequence motif in the prodomain presents features of an amphipathic helix likely to bind a hydrophobic cleft in Spätzle thereby occluding the putative Toll binding region. This mechanism of activation has a striking similarity to that of coagulogen, a clotting factor of the horseshoe crab, an invertebrate that has changed little in 400 million years. Taken together, our findings demonstrate that an ancient passive defense system has been adapted during evolution and converted for use in a critical pathway of innate immune signaling and embryonic morphogenesis.
The Journal of Biological Chemistry, 285, 19502-19509. June 18, 2010
http://www.jbc.org/content/285/25/19502.abstract
Unique Bell-shaped Voltage-dependent Modulation of Na+ Channel Gating by Novel Insect-selective Toxins from the Spider Agelena orientalis*
Bert Billen‡,1, Alexander Vassilevski§,1, Anton Nikolsky§, Sarah Debaveye‡, Jan Tytgat‡,2 and Eugene Grishin§,3 jan.tytgat@pharm.kuleuven.be grev@ibch.ru
Spider venoms provide a highly valuable source of peptide toxins that act on a wide diversity of membrane-bound receptors and ion channels. In this work, we report isolation, biochemical analysis, and pharmacological characterization of a novel family of spider peptide toxins, designated β/δ-agatoxins. These toxins consist of 36–38 amino acid residues and originate from the venom of the agelenid funnel-web spider Agelena orientalis. The presented toxins show considerable amino acid sequence similarity to other known toxins such as μ-agatoxins, curtatoxins, and δ-palutoxins-IT from the related spiders Agelenopsis aperta, Hololena curta, and Paracoelotes luctuosus. β/δ-Agatoxins modulate the insect NaV channel (DmNaV1/tipE) in a unique manner, with both the activation and inactivation processes being affected. The voltage dependence of activation is shifted toward more hyperpolarized potentials (analogous to site 4 toxins) and a non-inactivating persistent Na+ current is induced (site 3-like action). Interestingly, both effects take place in a voltage-dependent manner, producing a bell-shaped curve between −80 and 0 mV, and they are absent in mammalian NaV channels. To the best of our knowledge, this is the first detailed report of peptide toxins with such a peculiar pharmacological behavior, clearly indicating that traditional classification of toxins according to their binding sites may not be as exclusive as previously assumed.
The Journal of Biological Chemistry, 285, 18545-18554. June 11, 2010
http://www.jbc.org/content/285/24/18545.abstract
Insect Chemoreception
Morpho-functional asymmetry of the olfactory receptors of the honeybee (Apis mellifera)
Elisa Frasnellia,
a CiMeC, Centre for Mind/Brain Sciences,
b IASMA Research and Innovation Center, Fondazione E. Mach, Via E. Mach 1, 38010, San Michele all’Adige, Italy
c Biophysics and Biosignals Lab., Dept. of Physics,
Lateralization, i.e., the different functional specialisation of the left and right side of the brain, has been documented in many vertebrate species and, recently, in invertebrate species as well. In the Honeybee, Apis mellifera L. (Hymenoptera Apidae), it has been shown that short-term (<1 h) recall of olfactory memories would be possible mainly from the right rather than from the left antenna. Here we confirmed this finding showing that recall of the olfactory memory 1 h after training to associate (−)-linalool, a floral volatile compound, with a sugar reward, as revealed by the bee extending its proboscis when presented with the trained odour, was better when the odour was presented to the right rather than to the left antenna. We then measured the number of sensilla present on the left and right antenna by scanning electron microscopy. Results showed that putative olfactory sensilla (placodea, trichodea, basiconica) were significantly more abundant on the right antenna surface than on the left antenna surface, whereas sensilla not involved in olfaction (campaniformia, coeloconica and chaetica) tended to be more abundant on the left than on the right antenna surface.
Behavioural Brain Research Volume 209, Issue 2, 19 June 2010, Pages 221-225
Molecular Characterization of a Phospholipase C β Potentially Involved in Moth Olfactory Transduction
Bastien Chouquet1,2, Philippe Lucas2, Françoise Bozzolan1, Marthe Solvar1, Martine Maïbèche-Coisné1,2, Nicolas Durand1 and Stéphane Debernard1 stephane.debernard@snv.jussieu.fr
1 Unité mixte de Recherche 1272, Université Pierre et Marie Curie-Institut Nationnal de la Recherche Agronomique, Physiologie de l'Insecte: Signalisation et Communication, Université Paris VI, Bâtiment A, 7 quai Saint Bernard, 75005 Paris, France 2 UMR 1272, Physiologie de l'Insecte: Signalisation et Communication, INRA, route de Saint-Cyr, F-78000 Versailles, France
To clarify the role of phospholipase C (PLC) in insect olfactory transduction, we have undertaken its molecular identification in the moth Spodoptera littoralis. From the analysis of a male antennal expressed sequence tag library, we succeeded in cloning a full-length cDNA encoding a PLC that belongs to the cluster of PLC-β subtypes. In adult males, the PLC-β transcript was located predominantly in brain and antennae where its presence was detected in the olfactory sensilla trichodea. Moreover, PLC-β was expressed in antennae at the beginning of the pupal stage, then reached a maximum at the end of this stage and was maintained at this level during the adult period. Taken together, these results provided molecular evidence for the putative participation of a PLC-β in signaling pathways responsible for the establishment and the functioning of insect olfactory system.
Chemical Senses 2010 35(5):363-373; doi:10.1093/chemse/bjq024
http://chemse.oxfordjournals.org/cgi/content/abstract/35/5/363
Insect Development
Multiscale modeling of diffusion in the early Drosophila embryo
Christine Sample and Stanislav Y. Shvartsman1 stas@princeton.edu.
We developed a multiscale approach for the computationally efficient modeling of morphogen gradients in the syncytial Drosophila embryo, a single cell with multiple dividing nuclei. By using a homogenization technique, we derived a coarse-grained model with parameters that are explicitly related to the geometry of the syncytium and kinetics of nucleocytoplasmic shuttling. One of our main results is an accurate analytical approximation for the effective diffusivity of a morphogen molecule as a function of the nuclear density. We used this expression to explore the dynamics of the Bicoid morphogen gradient, a signal that patterns the anterior-posterior axis of the embryo. A similar approach can be used to analyze the dynamics of all three maternal morphogen gradients in Drosophila.
PNAS June 1, 2010 vol. 107 no. 22 10092-10096
http://www.pnas.org/content/107/22/10092.abstract?etoc
Insect Evolution
The impact of clonal mixing on the evolution of social behaviour in aphids
John Bryden* and Vincent A. A. Jansen john.bryden@rhul.ac.uk
Reports of substantial clonal mixing measured in social aphid colonies seem, on the face of it, to rule out population structure as an explanation of this enigmatic insect's social behaviour. To clarify how selection operates in aphids, and to disentangle direct and indirect fitness components, we present a model of the life cycle of a typical colony-dwelling aphid. The model incorporates ecological factors and includes a trade-off between investing in social behaviour and investing in reproduction. Our focus on inclusive fitness contrasts with previous approaches that optimize colony output. Through deriving a variant of
Proc. R. Soc. B 7 June 2010 vol. 277 no. 1688 1651-1657
http://rspb.royalsocietypublishing.org/content/277/1688/1651.abstract
Dispersal and ejaculatory strategies associated with exaggeration of weapon in an armed beetle
Takashi Yamane, Kensuke Okada*,Satoshi Nakayama and Takahisa Miyatake okaken@cc.okayama-u.ac.jp
Weapons used in male fighting can be costly to males and are often reported to trade off with other characters such as wings or spermatogenic investment. This study investigated whether increased investment into weapons can generate evolutionary changes in mating strategy for armed males. Male flour beetles, Gnatocerus cornutus, have enlarged mandibles that are used in male–male competition. We subjected these weapons to 12 generations of bidirectional selection and found trade-offs between weapons and two other male characters: wing and testis size. In addition, probably as a consequence of the observed changes in investment, dispersal ability and ejaculatory volume differ significantly between the lines. This indicates that the exaggeration of a weapon can be associated with dispersal and ejaculatory strategies. Thus, altered investment into weapons can lead to correlated changes in life-history traits.
Proc. R. Soc. B 7 June 2010 vol. 277 no. 1688 1705-1710
http://rspb.royalsocietypublishing.org/content/277/1688/1705.abstract
Reproductive constraints, direct fitness and indirect fitness benefits explain helping behaviour in the primitively eusocial wasp, Polistes canadensis
Seirian Sumner1,*, Hans Kelstrup2 and Daniele Fanelli3 seirian.sumner@ioz.ac.uk
A key step in the evolution of sociality is the abandonment of independent breeding in favour of helping. In cooperatively breeding vertebrates and primitively eusocial insects, helpers are capable of leaving the group and reproducing independently, and yet many do not. A fundamental question therefore is why do helpers help? Helping behaviour may be explained by constraints on independent reproduction and/or benefits to individuals from helping. Here, we examine simultaneously the reproductive constraints and fitness benefits underlying helping behaviour in a primitively eusocial paper wasp. We gave 31 helpers the opportunity to become egg-layers on their natal nests by removing nestmates. This allowed us to determine whether helpers are reproductively constrained in any way. We found that age strongly influenced whether an ex-helper could become an egg-layer, such that young ex-helpers could become egg-layers while old ex-helpers were less able. These differential reproductive constraints enabled us to make predictions about the behaviours of ex-helpers, depending on the relative importance of direct and indirect fitness benefits. We found little evidence that indirect fitness benefits explain helping behaviour, as 71 per cent of ex-helpers left their nests before the end of the experiment. In the absence of reproductive constraints, however, young helpers value direct fitness opportunities over indirect fitness. We conclude that a combination of reproductive constraints and potential for future direct reproduction explain helping behaviour in this species. Testing several competing explanations for helping behaviour simultaneously promises to advance our understanding of social behaviour in animal groups.
Proc. R. Soc. B 7 June 2010 vol. 277 no. 1688 1721-1728
http://rspb.royalsocietypublishing.org/content/277/1688/1721.abstract
Natural and Sexual Selection in a Wild Insect Population
R. Rodríguez-Muñoz,1 A. Bretman,1,2 J. Slate,3 C. A. Walling,4 T. Tregenza1,* t.tregenza@exeter.ac.uk
1 Centre for Ecology and Conservation,
2
3 Department of Animal and Plant Sciences, University of Sheffield, Western Bank,
4 Institute of Evolutionary Biology,
The understanding of natural and sexual selection requires both field and laboratory studies to exploit the advantages and avoid the disadvantages of each approach. However, studies have tended to be polarized among the types of organisms studied, with vertebrates studied in the field and invertebrates in the lab. We used video monitoring combined with DNA profiling of all of the members of a wild population of field crickets across two generations to capture the factors predicting the reproductive success of males and females. The factors that predict a male’s success in gaining mates differ from those that predict how many offspring he has. We confirm the fundamental prediction that males vary more in their reproductive success than females, and we find that females as well as males leave more offspring when they mate with more partners.
Science 4 June 2010:Vol. 328. no. 5983, pp. 1269 - 1272
Insect Function Ecology
Male moths provide pollination benefits in the Silene latifolia–Hadena bicruris nursery pollination system
Anne-Marie Labouche 1,2 and Giorgina Bernasconi 1,2,* giorgina.bernasconi@unine.ch
1 Department of Ecology and Evolution, University of Lausanne, Biophore, CH-1015 Lausanne, Switzerland ; and 2 Institute of Biology, University of Neuchâtel, Rue Emile-Agrand II, CH-2009 Neuchâtel, Switzerland
1. Evolutionary conflicts of interest underlie mutualisms, including plant/pollinator interactions. This is particularly evident in 'nursery pollination', in which the pollinators lay eggs inside the flowers and the offspring of the pollinator consume the developing seeds. Low benefit (pollination service) to cost (seed predation) ratios could destabilize such associations towards parasitism.
2. Although in most of the well-known cases pollen transfer is associated with oviposition, in some systems the males of the seed predator may contribute to pollination, affecting the strength and outcome of the interaction between the plant and their ovipositing pollinators. In addition, in dioecious species male and female plants differ in the direct costs of seed predation and benefits of attracting pollinators, which may lead to sex-specific strategies.
3. We investigated whether pollinator and plant sex affect pollination in the interaction between dioecious plant Silene latifolia and its nursery pollinator, Hadena bicruris (Noctuidae).
4. Data on visitation behaviour and pollination efficiency in experimental plant patches demonstrate that (i) male moths are equally efficient pollinators as female moths, leading to fruit initiation in around 80% of visits and to fertilization of around 45% of the ovules in one visit; (ii) female and male moths do not preferentially visit flowers of one sex; and (iii) feeding behaviour is sufficient to ensure pollen transfer. However, female moths visited significantly more flowers than male moths.
5. Altogether this suggests that both moth sexes provide a pollination benefit to the plant with no differences in pollination efficiency but that female moths, before seed predation costs are accounted for, seem to provide greater benefits owing to their increased activity. That male moths contribute to seed production likely decreases the plant's dependency on ovipositing moths for pollination.
Functional Ecology 2010 Volume 24 Issue 3, Pages 534 - 544
http://www3.interscience.wiley.com/journal/122671162/abstract
Thermal ramping rate influences evolutionary potential and species differences for upper thermal limits in Drosophila
Katherine A. Mitchell*,1 and Ary A. Hoffmann 1,2 kamit@unimelb.edu.au
1 Centre for Environmental Stress and Adaptation Research & Department of Genetics, University of Melbourne, Parkville, Victoria 3010, Australia ; and 2 Department of Zoology, University of Melbourne, Parkville, Victoria 3010, Australia
1. Thermal tolerance is a key factor limiting insect distributions, but there is limited information on the ability of species to evolve different thermal limits. Recent studies indicate that the experimental protocol influences upper limits, with slower but ecologically relevant rates of warming lowering estimates of tolerance. These effects could also influence genetic and environmental variances that define evolutionary potential.
2. To determine the influence of experimental protocol on estimates of narrow sense heritability (h2n) and other measures of evolutionary potential in Drosophila melanogaster, we conducted family studies on knockdown time when flies were immediately exposed to a high temperature (static) or when temperature was increased to an upper limit (ramping).
3. Estimates of variance components in two populations were obtained using the animal model approach that incorporates information from all relationships among relatives. Coefficients of variation were higher when flies were exposed to a static stress, as were estimates of additive genetic variance and measures of evolvability where genetic variances were standardized by trait means. In contrast, levels of environmental variance were higher under ramping conditions. These effects mean that the narrow sense heritability of thermal resistance was low under slow ramping and did not differ significantly from zero.
4. Differences in thermal limits under both methods were detected among Drosophila species. There was a significant positive relationship between the fast and slow ramping estimates of thermal resistance across species after correction for phylogeny, suggesting similar underlying mechanisms or a history of correlated evolution. However, this result was caused by the strong influence of two taxa.
5. These results suggest that natural populations exhibit lower adaptive potential for upper thermal limits under ramping than estimated from traditional (static) estimates of heat resistance. Even the highly adaptable Drosophila melanogaster appears to have little evolutionary potential to extend its upper thermal range under ramping conditions although species have diverged for this measure.
Functional Ecology 2010 Volume 24 Issue 3, Pages 694 - 700
http://www3.interscience.wiley.com/journal/123206256/abstract
Insect Memory
Acute Disruption of the NMDA Receptor Subunit NR1 in the Honeybee Brain Selectively Impairs Memory Formation
Laurenz Müßig, Antje Richlitzki, Reinhard Rößler, Dorothea Eisenhardt, Randolf Menzel, and Gérard Leboulle gerleb@zedat.fu-berlin.de
Neurobiologie, Freie
Memory formation is a continuous process composed of multiple phases that can develop independently from each other. These phases depend on signaling pathways initiated after the activation of receptors in different brain regions. The NMDA receptor acts as a sensor of coincident activity between neural inputs, and, as such, its activation during learning is thought to be crucial for various forms of memory. In this study, we inhibited the expression of the NR1 subunit of the NMDA receptor in the honeybee brain using RNA interference. We show that the disruption of the subunit expression in the mushroom body region of the honeybee brain during and shortly after appetitive learning selectively impaired memory. Although the formation of mid-term memory and early long-term memory was impaired, late long-term memory was left intact. This indicates that late long-term memory formation differs in its dependence on NMDA receptor activity from earlier memory phases.
The Journal of Neuroscience, June 9, 2010, 30(23):7817-7825;
http://www.jneurosci.org/cgi/content/abstract/30/23/7817
Insect Molecular Biology
EGF Signaling and the Origin of Axial Polarity among the Insects
Jeremy A. Lynch
Institute of Developmental Biology, University of Cologne, Zülpicher Stra
Highlights Asymmetric positioning of the oocyte nucleus is broadly conserved in insects. EGF signaling is required for encapsulation of the oocyte by follicle cells. Late asymmetric germline-to-soma EGF signal correlated with oocyte nucleus position. Conserved role of EGF signal in establishing embryonic DV polarity across insects
Summary
The eggs of insects are unusual in that they often have bilateral symmetry when they are laid, indicating that both anterior-posterior (AP) and dorsal-ventral (DV) symmetries are broken during oogenesis [1]. The molecular basis of this process is well understood in Drosophila melanogaster, in which symmetry breaking events for both axes depend on the asymmetric position of the oocyte nucleus and on germline-soma signaling mediated by the Tgfα-like epidermal growth factor (EGF) ligand Gurken [2,3]. Germline-soma signaling interactions centered around the oocyte nucleus have been proposed in other insect species [4,5], but the molecular nature of these interactions has not been elucidated. We have examined the behavior of the oocyte nucleus and the function of EGF signaling components in the ovaries of the wasp Nasonia vitripennis, the beetle Tribolium castaneum, and the cricket Gryllus bimaculatus. We have found that EGF signaling has broadly conserved roles in mediating the encapsulation of oocytes by the somatic follicle cell layer, in establishing polarity of the egg chambers, and in setting up the DV axis of the embryo. These results provide insights into the evolutionary origins of the unique strategy employed by insects to establish embryonic axial polarity during oogenesis.
Current Biology, Volume 20, Issue 11, 1042-1047, 13 May 2010
http://www.cell.com/current-biology/abstract/S0960-9822%2810%2900500-2
Insect Molecular Ecology
Bayesian analysis of molecular variance in pyrosequences quantifies population genetic structure across the genome of Lycaeides butterflies
ZACHARIAH GOMPERT*, MATTHEW L. FORISTER†, JAMES A. FORDYCE‡, CHRIS C. NICE§, ROBERT J. WILLIAMSON¶ and C. ALEX BUERKLE* zgompert@uwyo.edu
*Department of Botany, Program in Ecology, University of Wyoming, Laramie, WY 82071, USA , †Department of Biology/MS 314, University of Nevada, Reno, NV 89557, USA , ‡Department of Ecology and Evolutionary Biology, University of Tennessee, Knoxville, TN 37996, USA , §Department of Biology, Population and Conservation Biology Program, Texas State University, San Marcos, TX 78666, USA , ¶Department of Applied Biology and Biomedical Engineering and Department of Computer Science and Software Engineering, Rose-Hulman Institute of Technology, Terre Haute, IN 47803, USA
The distribution of genetic variation within and among populations is commonly used to infer their demographic and evolutionary histories. This endeavour has the potential to benefit substantially from high-throughput next-generation sequencing technologies through a rapid increase in the amount of data available and a corresponding increase in the precision of parameter estimation. Here we report the results of a phylogeographic study of the North American butterfly genus Lycaeides using 454 sequence data. This study serves the dual purpose of demonstrating novel molecular and analytical methods for population genetic analyses with 454 sequence data and expanding our knowledge of the phylogeographic history of Lycaeides. We obtained 341 045 sequence reads from 12 populations that we were able to assemble into 15 262 contigs (most of which were variable), representing one of the largest population genetic data sets for a non-model organism to date. We examined patterns of genetic variation using a hierarchical Bayesian analysis of molecular variance model, which provides precise estimates of genome-level φST while appropriately modelling uncertainty in locus-specific φST. We found that approximately 36% of sequence variation was partitioned among populations, suggesting historical or current isolation among the sampled populations. Estimates of pairwise genome-level φST were largely consistent with a previous phylogeographic model for Lycaeides, suggesting fragmentation into two to three refugia during Pleistocene glacial cycles followed by post-Pleistocene range expansion and secondary contact leading to introgressive hybridization. This study demonstrates the potential of using genome-level data to better understand the phylogeographic history of populations.
Molecular Ecology 2010 Volume 19 Issue 12, Pages 2455 - 2473
http://www3.interscience.wiley.com/journal/123457122/abstract
Insect Morphology
Underwater attachment in current: the role of setose attachment structures on the gills of the mayfly larvae Epeorus assimilis (Ephemeroptera, Heptageniidae)
P. Ditsche-Kuru1,*, J. H. E. Koop2 and S. N. Gorb3,4 p.ditsche-kuru@uni-bonn.de
1 Biological Interfaces Working Group, Nees Institute for Biodiversity of Plants, University of Bonn, Meckenheimer Allee 170, 53115 Bonn, Germany
2 Department of Animal Ecology, Federal Institute of Hydrology, 56068 Koblenz, Germany
3 Evolutionary Biomaterials Group, Max Plank Institute for Metal Research, Heisenbergstrasse 3, 70569 Stuttgart, Germany
4 Department of Functional Morphology and Biomechanics, Zoological Institute of the University of Kiel, Am Botanischen Garten 1-9, 24098 Kiel, Germany
Setose pads of aquatic Epeorus assimilis larvae are specialised structures located ventrally on the part of the gill lamella contacting the substrate and were suggested to have an attachment function in strong currents. In order to test the role of these setose pads in underwater attachment for the first time, we measured friction (shear) forces generated by the gill lamellae on solid substrates. Moreover, the influence of a different kind of surface roughness on attachment was investigated. Scanning electron microscopy showed that four different seta types can be found on the pads. Our results revealed that the pads significantly contributed to friction force generated on smooth and on some rough substrates but not on certain surfaces of intermediate roughness. The contribution of pads to the friction coefficient in experiments was lower than expected under natural conditions, which may be caused by a smaller contact area between the pads and the substrate (changes in material properties, lack of the active control of body positioning of the larva). The friction coefficient of the gill lamellae with the substrate depended on the surface roughness of the substrate and on the pulling direction. These results suggest that interlocking between structures of the insect cuticle and substrate irregularities, as well as molecular adhesion, contribute to friction.
Journal of Experimental Biology 213, 1950-1959 (2010)
http://jeb.biologists.org/cgi/content/abstract/213/11/1950
Exoskeletal chitin scales isometrically with body size in terrestrial insects
Hilary M. Lease 1 2 *, Blair O. Wolf 1hlease@unm.edu
1Biology Department, University of New Mexico, Albuquerque, New Mexico 87131
2Biology Department, Whitman College, Walla Walla, Washington 99362
The skeletal system of animals provides the support for a variety of activities and functions. For animals such as mammals, which have endoskeletons, research has shown that skeletal investment (mass) scales with body mass to the 1.1 power. In this study, we ask how exoskeletal investment in insects scales with body mass. We measured the body mass and mass of exoskeletal chitin of 551 adult terrestrial insects of 245 species, with dry masses ranging from 0.0001 to 2.41 g (0.0002-6.13 g wet mass) to assess the allometry of exoskeletal investment. Our results showed that exoskeletal chitin mass scales isometrically with dry body mass across the Insecta as Mchitin = a M
Journal of Morphology 2010 Volume 271 Issue 6, Pages 759 - 768
http://www3.interscience.wiley.com/journal/123322350/abstract
The fine structure of honeybee head and body yaw movements in a homing task
Norbert Boeddeker*, Laura Dittmar, Wolfgang Stürzl and Martin Egelhaaf norbert.boeddeker@uni-bielefeld.de
Honeybees turn their thorax and thus their flight motor to change direction or to fly sideways. If the bee's head were fixed to its thorax, such movements would have great impact on vision. Head movements independent of thorax orientation can stabilize gaze and thus play an important and active role in shaping the structure of the visual input the animal receives. Here, we investigate how gaze and flight control interact in a homing task. We use high-speed video equipment to record the head and body movements of honeybees approaching and departing from a food source that was located between three landmarks in an indoor flight arena. During these flights, the bees' trajectories consist of straight flight segments combined with rapid turns. These short and fast yaw turns (‘saccades’) are in most cases accompanied by even faster head yaw turns that start about 8 ms earlier than the body saccades. Between saccades, gaze stabilization leads to a behavioural elimination of rotational components from the optical flow pattern, which facilitates depth perception from motion parallax.
Proc. R. Soc. B 22 June 2010 vol. 277 no. 1689 1899-1906
http://rspb.royalsocietypublishing.org/content/277/1689/1899.abstract?etoc
Sensory signals of contact and engagement with the substrate are important in the control and adaptation of posture and locomotion. We characterized responses of campaniform sensilla, receptors that encode forces as cuticular strains, in the tarsi (feet) of cockroaches using neurophysiological techniques and digital imaging. A campaniform sensillum on the fourth tarsal segment was readily identified by its large action potential in nerve recordings. The receptor discharged to contractions of the retractor unguis muscle, which engages the pretarsus (claws and arolium) with the substrate. We mimicked the effects of muscle contractions by applying displacements to the retractor apodeme (tendon). Sensillum firing did not occur to unopposed movements, but followed engagement of the claws with an object. Vector analysis of forces suggested that resisted muscle contractions produce counterforces that axially compress the tarsal segments. Close joint packing of tarsal segments was clearly observed following claw engagement. Physiological experiments showed that the sensillum responded vigorously to axial forces applied directly to the distal tarsus. Discharges of tarsal campaniform sensilla could effectively signal active substrate engagement when the pretarsal claws and arolium are used to grip the substrate in climbing, traversing irregular terrains or walking on inverted surfaces.
Journal of Comparative Physiology A: Neuroethology, Sensory, Neural, and Behavioral Physiology Volume 196, Number 6 / June, 2010 407-420
http://www.springerlink.com/content/y3683l0724171539/
A model of visual–olfactory integration for odour localisation in free-flying fruit flies
Finlay J. Stewart1, Dean A. Baker2 and Barbara Webb1,* bwebb@inf.ed.ac.uk
1 Institute of Perception, Action and Behaviour, School of Informatics, University of Edinburgh, 10 Crichton Street, Edinburgh EH8 9AB, UK
2 Department of Genetics, University of Cambridge, Downing Street, Cambridge CB1 3QA, UK
Flying fruit flies (Drosophila melanogaster) locate a concealed appetitive odour source most accurately in environments containing vertical visual contrasts. To investigate how visuomotor and olfactory responses may be integrated, we examine the free-flight behaviour of flies in three visual conditions, with and without food odour present. While odour localisation is facilitated by uniformly distributed vertical contrast as compared with purely horizontal contrast, localised vertical contrast also facilitates odour localisation, but only if the odour source is situated close to it. We implement a model of visuomotor control consisting of three parallel subsystems: an optomotor response stabilising the model fly's yaw orientation; a collision avoidance system to saccade away from looming obstacles; and a speed regulation system. This model reproduces many of the behaviours we observe in flies, including visually mediated ‘rebound’ turns following saccades. Using recordings of real odour plumes, we simulate the presence of an odorant in the arena, and investigate ways in which the olfactory input could modulate visuomotor control. We reproduce the experimental results by using the change in odour intensity to regulate the sensitivity of collision avoidance, resulting in visually mediated chemokinesis. Additionally, it is necessary to amplify the optomotor response whenever odour is present, increasing the model fly's tendency to steer towards features of the visual environment. We conclude that visual and olfactory responses of Drosophila are not independent, but that relatively simple interaction between these modalities can account for the observed visual dependence of odour source localisation.
Journal of Experimental Biology 213, 1886-1900 (2010)
http://jeb.biologists.org/cgi/content/abstract/213/11/1886
Insect Neuroscience
Effect of photoperiod on clock gene expression and subcellular distribution of PERIOD in the circadian clock neurons of the blow fly Protophormia terraenovae
Fumiaki Muguruma1, Shin G. Goto1, Hideharu Numata1, 2 and Sakiko Shiga1
Department of Biology and Geosciences, Graduate
We examined the effect of photoperiod on the expression of circadian clock genes period (per) and timeless (tim), using quantitative real-time polymerase chain reaction (PCR), and the effect of photoperiod on subcellular distribution of PERIOD (PER), using immunocytochemistry, in the blow fly, Protophormia terraenovae. Under both short-day and long-day conditions, the mRNA levels of per and tim in the brain oscillated, and their peaks and troughs occurred around lights-off and lights-on, respectively. The oscillations persisted even under constant darkness. In the large ventral lateral neurons (l-LNvs), small ventral lateral neurons (s-LNvs), dorsal lateral neurons (LNds), and medial dorsal neurons (DNms), the subcellular distribution of PER-immunoreactivity changed with time. The number of cells with PER-immunoreactivity in the nucleus was highest 12 h after lights-off and lowest 12 h after lights-on, regardless of photoperiod, suggesting that PER nuclear translocation entrains to photoperiod. When temporal changes in the nuclear localization of PER were compared, the neurons could be classified into 2 groups: the l-LNvs were similar to the s-LNvs, and the LNds were similar to DNms. In LNds and DNms, decreasing rates of the number of cells with PER immunoreactivity in the nucleus per brain from the maximum were large as compared with those in l-LNvs and s-LNvs under short-day conditions. These results suggest that photoperiodic information is reflected in the expression patterns of circadian clock genes per and tim and in the subcellular distribution of PER. This observation suggests that the 2 different groups of clock neurons respond to photoperiod in slightly different manners.
Cell and Tissue Research Volume 340, Number 3 / June, 2010 497-507
http://www.springerlink.com/content/24490p702727n304/
The Leucokinin Pathway and Its Neurons Regulate Meal Size in Drosophila
Bader Al-Anzi
Division of Biology, California Institute of Technology, Pasadena, CA 91125, USA Department of Molecular, Cellular and Developmental Biology, Yale University, KBT 610, PO Box 208103, New Haven, CT 06511, USA
Highlights Mutations in leucokinin or leucokinin receptor genes affect meal size in Drosophila. Mutant flies take fewer but larger meals, so their total food consumption is normal. Leucokinin and its receptor function in small groups of neurons to regulate meal size. Ablation of the neurons expressing the peptide or its receptor increases meal size
Summary Background Total food intake is a function of meal size and meal frequency, and adjustments to these parameters allow animals to maintain a stable energy balance in changing environmental conditions. The physiological mechanisms that regulate meal size have been studied in blowflies but have not been previously examined in Drosophila. Results Here we show that mutations in the leucokinin neuropeptide (leuc) and leucokinin receptor (lkr) genes cause phenotypes in which Drosophila adults have an increase in meal size and a compensatory reduction in meal frequency. Because mutant flies take larger but fewer meals, their caloric intake is the same as that of wild-type flies. The expression patterns of the leuc and lkr genes identify small groups of brain neurons that regulate this behavior. Leuc-containing presynaptic terminals are found close to Lkr neurons in the brain and ventral ganglia, suggesting that they deliver Leuc peptide to these neurons. Lkr neurons innervate the foregut. Flies in which Leuc or Lkr neurons are ablated have defects identical to those of leucokinin pathway mutants. Conclusions Our data suggest that the increase in meal size in leuc and lkr mutants is due to a meal termination defect, perhaps arising from impaired communication of gut distension signals to the brain. Leucokinin and the leucokinin receptor are homologous to vertebrate tachykinin and its receptor, and injection of tachykinins reduces food consumption. Our results suggest that the roles of the tachykinin system in regulating food intake might be evolutionarily conserved between insects and vertebrates.
Current Biology, Volume 20, Issue 11, 969-978, 20 May 2010
http://www.cell.com/current-biology/abstract/S0960-9822%2810%2900517-8
PDF receptor expression reveals direct interactions between circadian oscillators in drosophila
Seol Hee Im, Paul H. Taghert *taghertp@pcg.wustl.edu
Department of Anatomy and Neurobiology,
Daily rhythms of behavior are controlled by a circuit of circadian pacemaking neurons. In Drosophila, 150 pacemakers participate in this network, and recent observations suggest that the network is divisible into M and E oscillators, which normally interact and synchronize. Sixteen oscillator neurons (the small and large lateral neurons [LNvs]) express a neuropeptide called pigment-dispersing factor (PDF) whose signaling is often equated with M oscillator output. Given the significance of PDF signaling to numerous aspects of behavioral and molecular rhythms, determining precisely where and how signaling via the PDF receptor (PDFR) occurs is now a central question in the field. Here we show that GAL4-mediated rescue of pdfr phenotypes using a UAS-PDFR transgene is insufficient to provide complete behavioral rescue. In contrast, we describe a
J. Comp. Neurol. 518:1925-1945, 2010.
http://www3.interscience.wiley.com/journal/123215845/abstract
Tiling among stereotyped dendritic branches in an identified Drosophila motoneuron
F. Vonhoff, C. Duch carsten.duch@asu.edu
School of Life Sciences,
Different types of neurons can be distinguished by the specific targeting locations and branching patterns of their dendrites, which form the blueprint for wiring the brain. Unraveling which specific signals control different aspects of dendritic architecture, such as branching and elongation, pruning and cessation of growth, territory formation, tiling, and self-avoidance requires a quantitative comparison in control and genetically manipulated neurons. The highly conserved shapes of individually identified Drosophila neurons make them well suited for the analysis of dendritic architecture principles. However, to date it remains unclear how tightly dendritic architecture principles of identified central neurons are regulated. This study uses quantitative reconstructions of dendritic architecture of an identified Drosophila flight motoneuron (MN5) with a complex dendritic tree, comprising more than 4,000 dendritic branches and 6 mm total length. MN5 contains a fixed number of 23 dendritic subtrees, which tile into distinct, nonoverlapping volumes of the diffuse motor neuropil. Across-animal comparison and quantitative analysis suggest that tiling of the different dendritic subtrees of the same neuron is caused by competitive and repulsive interactions among subtrees, perhaps allowing different dendritic compartments to be connected to different circuit elements. We also show that dendritic architecture is similar among different wildtype and GAL4 driver fly lines. Metric and topological dendritic architecture features are sufficiently constant to allow for studies of the underlying control mechanisms by genetic manipulations. Dendritic territory and certain topological measures, such as tree compactness, are most constant, suggesting that these reflect the intrinsic molecular identity of the neuron.
J. Comp. Neurol. 518:2169-2185, 2010.
http://www3.interscience.wiley.com/journal/123328340/abstract?CRETRY=1&SRETRY=0
Sex-specific antennal sensory system in the ant Camponotus japonicus: Glomerular organizations of antennal lobes
Aki Nakanishi 1, Hiroshi Nishino 2, Hidehiro Watanabe 1, Fumio Yokohari 1, Michiko Nishikawa 1michiko@fukuoka-u.ac.jp
1Department of Earth System Science,
2Research Institute for Electronic Science,
Ants have well-developed chemosensory systems for social lives. The goal of our study is to understand the functional organization of the ant chemosensory system based on caste- and sex-specific differences. Here we describe the common and sex-specific glomerular organizations in the primary olfactory center, the antennal lobe of the carpenter ant Camponotus japonicus. Differential labeling of the two antennal nerves revealed distinct glomerular clusters innervated by seven sensory tracts (T1-T7 from ventral to dorsal) in the antennal lobe. T7 innervated 10 glomeruli, nine of which received thick axon terminals almost exclusively from the ventral antennal nerve. Coelocapitular (hygro-/thermoreceptive), coeloconic (thermoreceptive), and ampullaceal (CO2-receptive) sensilla, closely appositioned in the flagellum, housed one or three large sensory neurons supplying thick axons exclusively to the ventral antennal nerve. These axons, therefore, were thought to project into T7 glomeruli in all three castes. Workers and virgin females had about 140 T6 glomeruli, whereas males completely lacked these glomeruli. Female-specific basiconic sensilla (cuticular hydrocarbon-receptive) contained over 130 sensory neurons and were completely lacking in males' antennae. These sensory neurons may project into T6 glomeruli in the antennal lobe of workers and virgin females. Serotonin-immunopositive neurons innervated T1-T5 and T7 glomeruli but not T6 glomeruli in workers and virgin females. Because males had no equivalents to T6 glomeruli, serotonin-immunopositive neurons appeared to innervate all glomeruli in the male's antennal lobe. T6 glomeruli in workers and virgin females are therefore female-specific and may have functions related to female-specific tasks in the colony rather than sexual behaviors.
J. Comp. Neurol. 518:2186-2201, 2010.
http://www3.interscience.wiley.com/journal/123248480/abstract
Cellular configuration of single octopamine neurons in Drosophila
Sebastian Busch, Hiromu Tanimotohiromut@neuro.mpg.de
Max-Planck-Institut für Neurobiologie, D-82152 Martinsried, Germany, and Lehrstuhl für Genetik und Neurobiologie, Universität Würzburg, D-97074 Würzburg, Germany
Individual median octopamine neurons in the insect central nervous system serve as an excellent model system for comparative neuroanatomy of single identified cells. The median octopamine cluster of the subesophageal ganglion consists of defined sets of paired and unpaired interneurons, which supply the brain and subesophageal ganglion with extensive ramifications. The developmental program underlying the complex cellular network is unknown. Here we map the segmental location and developmental origins of individual octopamine neurons in the Drosophila subesophageal ganglion. We demonstrate that two sets of unpaired median neurons, located in the mandibular and maxillary segments, exhibit the same projection patterns in the brain. Furthermore, we show that the paired and unpaired neurons belong to distinct lineages. Interspecies comparison of median neurons revealed that many individual octopamine neurons in different species project to equivalent target regions. Such identified neurons with similar morphology can derive from distinct lineages in different species (i.e., paired and unpaired neurons).
J. Comp. Neurol. 518:2355-2364, 2010.
http://www3.interscience.wiley.com/journal/123248513/abstract
Identifying Neuronal Lineages of Drosophila by Sequence Analysis of Axon Tracts
Albert Cardona,1 Stephan Saalfeld,2 Ignacio Arganda,1
1Institute of Neuroinformatics, University of Zurich and Swiss Federal Institute of Technology, CH-8057 Zurich, Switzerland, 2Max Planck Institute of Molecular Cell Biology and Genetics, 01307 Dresden, Germany, 3Howard Hughes Medical Institute Janelia Farm, Ashburn, Virginia 20147, and 4Department of Molecular, Cell, and Developmental Biology, University of California, Los Angeles, Los Angeles, California 90095
The Drosophila brain is formed by an invariant set of lineages, each of which is derived from a unique neural stem cell (neuroblast) and forms a genetic and structural unit of the brain. The task of reconstructing brain circuitry at the level of individual neurons can be made significantly easier by assigning neurons to their respective lineages. In this article we address the automation of neuron and lineage identification. We focused on the Drosophila brain lineages at the larval stage when they form easily recognizable secondary axon tracts (SATs) that were previously partially characterized. We now generated an annotated digital database containing all lineage tracts reconstructed from five registered wild-type brains, at higher resolution and including some that were previously not characterized. We developed a method for SAT structural comparisons based on a dynamic programming approach akin to nucleotide sequence alignment and a machine learning classifier trained on the annotated database of reference SATs. We quantified the stereotypy of SATs by measuring the residual variability of aligned wild-type SATs. Next, we used our method for the identification of SATs within wild-type larval brains, and found it highly accurate (93–99%). The method proved highly robust for the identification of lineages in mutant brains and in brains that differed in developmental time or labeling. We describe for the first time an algorithm that quantifies neuronal projection stereotypy in the Drosophila brain and use the algorithm for automatic neuron and lineage recognition.
The Journal of Neuroscience, June 2, 2010, 30(22):7538-7553; http://www.jneurosci.org/cgi/content/abstract/30/22/7538
TDP-43 Mediates Degeneration in a Novel Drosophila Model of Disease Caused by Mutations in VCP/p97
Gillian P. Ritson,1,3 Sara K. Custer,3 Brian D. Freibaum,3 Jake B. Guinto,1 Dyanna Geffel,1 Jennifer Moore,3 Waixing Tang,1 Matthew J. Winton,2 Manuela Neumann,4 John Q. Trojanowski,2 Virginia M.-Y. Lee,2 Mark S. Forman,5 and J. Paul Taylor3 jpaul.taylor@stjude.org
1Department of Neurology and 2Department of Pathology and Laboratory Medicine, University of Pennsylvania School of Medicine, Philadelphia, Pennsylvania 19104, 3Department of Developmental Neurobiology, St. Jude Children's Research Hospital, Memphis, Tennessee 38105, 4Institute of Neuropathology, University Hospital of Zurich, Zurich, Switzerland, and 5Merck Research Labs, North Wales, Pennsylvania 19454
Inclusion body myopathy associated with Paget's disease of bone and frontotemporal dementia (IBMPFD) is a dominantly inherited degenerative disorder caused by mutations in the valosin-containing protein (VCP7) gene. VCP (p97 in mouse, TER94 in Drosophila melanogaster, and CDC48 in Saccharomyces cerevisiae) is a highly conserved AAA+ (ATPases associated with multiple cellular activities) ATPase that regulates a wide array of cellular processes. The mechanism of IBMPFD pathogenesis is unknown. To elucidate the pathogenic mechanism, we developed and characterized a Drosophila model of IBMPFD (mutant-VCP-related degeneration). Based on genetic screening of this model, we identified three RNA-binding proteins that dominantly suppressed degeneration; one of these was TBPH, the Drosophila homolog of TAR (trans-activating response region) DNA-binding protein 43 (TDP-43). Here we demonstrate that VCP and TDP-43 interact genetically and that disease-causing mutations in VCP lead to redistribution of TDP-43 to the cytoplasm in vitro and in vivo, replicating the major pathology observed in IBMPFD and other TDP-43 proteinopathies. We also demonstrate that TDP-43 redistribution from the nucleus to the cytoplasm is sufficient to induce cytotoxicity. Furthermore, we determined that a pathogenic mutation in TDP-43 promotes redistribution to the cytoplasm and enhances the genetic interaction with VCP. Together, our results show that degeneration associated with VCP mutations is mediated in part by toxic gain of function of TDP-43 in the cytoplasm. We suggest that these findings are likely relevant to the pathogenic mechanism of a broad array of TDP-43 proteinopathies, including frontotemporal lobar degeneration and amyotrophic lateral sclerosis.
The Journal of Neuroscience, June 2, 2010, 30(22):7729-7739
http://www.jneurosci.org/cgi/content/abstract/30/22/7729
Drosophila Neuroligin 1 Promotes Growth and Postsynaptic Differentiation at Glutamatergic Neuromuscular Junctions
Daniel Banovic, Omid Khorramshahi, David Owald, Carolin Wichmann, Tamara Riedt, Wernher Fouquet, Rui Tian, Stephan J. Sigrist
University of Münster, Institute for Neurobiology, Badestrasse 9, 48149 Münster, Germany Freie Universität Berlin, Institute for Biology/Genetics, Takustrasse 6, 14195 Berlin, Germany European Neuroscience Institute Göttingen, Grisebachstrasse 5, 37077 Göttingen, Germany Cluster of Excellence NeuroCure, Charite, Chariteplatz 1, 10117 Berlin, Germany Corresponding author Present address: University of Bonn, Department of Hematology/Oncology, Medical Center III, Wilhelmstrasse 35-37, 53111 Bonn, Germany
Highlights Unbiased screening uncovers Drosophila Neuroligin 1 as essential for NMJ morphology. DNlg1 promotes synaptic growth and postsynaptic differentiation in vivo. Precise apposition of the pre- and postsynaptic domain is lost in dnlg1 mutants. DNlg1 forms a distinct compartment adjacent to glutamate receptor fields
Summary Precise apposition of presynaptic and postsynaptic domains is a fundamental property of all neuronal circuits. Experiments in vitro suggest that Neuroligins and Neurexins function as key regulatory proteins in this process. In a genetic screen, we recovered several mutant alleles of Drosophila neuroligin 1 (dnlg1) that cause a severe reduction in bouton numbers at neuromuscular junctions (NMJs). In accord with reduced synapse numbers, these NMJs show reduced synaptic transmission. Moreover, lack of postsynaptic DNlg1 leads to deficits in the accumulation of postsynaptic glutamate receptors, scaffold proteins, and subsynaptic membranes, while increased DNlg1 triggers ectopic postsynaptic differentiation via its cytoplasmic domain. DNlg1 forms discrete clusters adjacent to postsynaptic densities. Formation of these clusters depends on presynaptic Drosophila Neurexin (DNrx). However, DNrx binding is not an absolute requirement for DNlg1 function. Instead, other signaling components are likely involved in DNlg1 transsynaptic functions, with essential interactions organized by the DNlg1 extracellular domain but also by the cytoplasmic domain.
Neuron, Volume 66, Issue 5, 724-738, 10 June 2010
http://www.cell.com/neuron/abstract/S0896-6273%2810%2900416-2
Ventral lateral and DN1 clock neurons mediate distinct properties of male sex drive rhythm in Drosophila
Shinsuke Fujii1 and Hubert Amrein1,2
Department of Molecular Genetics and Microbiology,
Male sex drive rhythm (MSDR) in Drosophila is a circadian behavior only observed in the social context of male-female pairs. In the presence of a female, males exhibit long periods of courtship activity with a pronounced rest phase at dusk, although isolated males exhibit an activity peak at dusk. The molecular mechanisms regulating the switch between these activity patterns are unknown. Here, we genetically manipulate the molecular clock in different subsets of neurons and find that proper oscillation of the molecular clock in ventral lateral neurons is essential for MSDR. These neurons express pigment-dispersing factor, the lack of which disrupts MSDR. Furthermore, we show that a cluster of dorsal neurons (DN1s) requires the molecular clock to synchronize the trough phase at dusk in MSDR and to establish the evening peak in single fly locomotor rhythm (SLR). Finally, we provide evidence that DN1s exert their roles in MSDR and SLR via distinct signaling pathways.
PNAS June 8, 2010 vol. 107 no. 23 10590-10595
http://www.pnas.org/content/107/23/10590.abstract?etoc
Insect Nutrition
Sex Peptide Receptor and Neuronal TOR/S6K Signaling Modulate Nutrient Balancing in Drosophila
Carlos Ribeiro
Research Institute of Molecular Pathology, Dr. Bohr-Gasse 7, A-1030 Vienna, Austria Corresponding author Present address: Champalimaud Neuroscience Programme, Instituto Gulbenkian de Ciência, Rua da Quinta Grande 6, P-2781-901 Oeiras, Portugal
Highlights Drosophila adapt foraging behavior to compensate for the lack of a macronutrient. In females, mating status modulates food choices. Mating status affects food choices through the sex peptide receptor in ppk+ neurons. Neuronal TOR/S6K signaling modulates food choices
Summary Animals often decide between alternative actions according to their current needs, and hence the value they assign to each of the competing options [1,2,3,4]. This process is of special relevance during nutrient balancing, in which animals choose between different food sources according to their current nutritional state [5,6,7]. How such value-based decision making is implemented at the molecular and neuronal level in the brain is not well understood. Here we describe Drosophila melanogaster food choice as a genetically tractable model to study value-based decision making in the context of nutrient balancing. When faced with a choice between yeast and an alternative food source, flies deprived of protein prefer the yeast. We show here that mating status is a critical modulator of this decision-making process in females and that it relies on the action of the sex peptide receptor in internal ppk+ sensory neurons. Neuronal TOR/S6K function is another critical input to this decision, possibly signaling the fly's current nutritional status. We propose that the brain uses these internal states to assign value to external sensory information from potential food sources, thereby guiding food choice and ensuring nutrient homeostasis.
Current Biology, Volume 20, Issue 11, 1000-1005, 13 May 2010
http://www.cell.com/current-biology/abstract/S0960-9822%2810%2900387-8
A Role for S6 Kinase and Serotonin in Postmating Dietary Switch and Balance of Nutrients in D. melanogaster
Misha A. Vargas, Ningguang Luo, Atsushi Yamaguchi, Pankaj Kapahi
Buck Institute for Age Research, 8001 Redwood Boulevard, Novato, CA 94945, USA Department of Neurobiology, Graduate School of Medicine, Chiba University, Chiba-shi, Chiba 260-8670, Japan
Highlights Mated female D. melanogaster show an increased preference for yeast in the diet. Neuronal expression of activated dS6K enhances preference for yeast. Neuronal expression of activated dS6K enhances serotonin production. dS6K activation and serotonin enhance preference for yeast by similar mechanisms
Summary
Balancing intake of diverse nutrients is important for organismal growth, reproduction, and survival. A shift in an organism's optimal diet due to changes in nutritional requirements after developmental or environmental changes is referred to as dietary switch and has been observed in several species [1]. Here we demonstrate that female Drosophila melanogaster also undergo a dietary switch following mating that leads to an increased preference for yeast, the major source of protein in their diet. We also demonstrate that S6 kinase (S6K) and serotonin production are involved in the postmating dietary switch. To further investigate the ability of D. melanogaster to balance nutrient intake, we examined the dietary preferences of adult flies following deprivation of yeast or sucrose. We observe that following conditioning on a diet deficient in either carbohydrates or yeast, D. melanogaster show a strong preference for the deficient nutrient. Furthermore, flies with activated dS6K or flies fed a serotonin precursor exhibit enhanced preference for yeast in this assay. Our results suggest that TOR signaling and serotonin may play an important role in maintaining nutrient balance in D. melanogaster. These studies may contribute to our understanding of metabolic disorders such as obesity and diabetes [2].
Current Biology, Volume 20, Issue 11, 1006-1011, 13 May 2010
http://www.cell.com/current-biology/abstract/S0960-9822%2810%2900443-4
Insect Olfaction
Functional feedback from mushroom bodies to antennal lobes in the Drosophila olfactory pathway
Aiqun Hua,1, Wei Zhanga,b,1, and Zuoren Wanga,2zuorenwang@ion.ac.cn
Feedback plays important roles in sensory processing. Mushroom bodies are believed to be involved in olfactory learning/memory and multisensory integration in insects. Previous cobalt-labeling studies have suggested the existence of feedback from the mushroom bodies to the antennal lobes in the honey bee. In this study, the existence of functional feedback from Drosophila mushroom bodies to the antennal lobes was investigated through ectopic expression of the ATP receptor P2X2 in the Kenyon cells of mushroom bodies. Activation of Kenyon cells induced depolarization in projection neurons and local interneurons in the antennal lobes in a nicotinic receptor-dependent manner. Activation of Kenyon cell axons in the βγ-lobes in the mushroom body induced more potent responses in the antennal lobe neurons than activation of Kenyon cell somata. Our results indicate that functional feedback from Kenyon cells to projection neurons and local interneurons is present in Drosophila and is likely mediated by the βγ-lobes. The presence of this functional feedback from the mushroom bodies to the antennal lobes suggests top-down modulation of olfactory information processing in Drosophila.
PNAS June 1, 2010 vol. 107 no. 22 10262-10267
http://www.pnas.org/content/107/22/10262.abstract?etoc
Generating sparse and selective third-order responses in the olfactory system of the fly
Sean X. Luoa, Richard Axela,b,c,1, and L. F. Abbotta,d,1
In the antennal lobe of Drosophila, information about odors is transferred from olfactory receptor neurons (ORNs) to projection neurons (PNs), which then send axons to neurons in the lateral horn of the protocerebrum (LHNs) and to Kenyon cells (KCs) in the mushroom body. The transformation from ORN to PN responses can be described by a normalization model similar to what has been used in modeling visually responsive neurons. We study the implications of this transformation for the generation of LHN and KC responses under the hypothesis that LHN responses are highly selective and therefore suitable for driving innate behaviors, whereas KCs provide a more general sparse representation of odors suitable for forming learned behavioral associations. Our results indicate that the transformation from ORN to PN firing rates in the antennal lobe equalizes the magnitudes of and decorrelates responses to different odors through feedforward nonlinearities and lateral suppression within the circuitry of the antennal lobe, and we study how these two components affect LHN and KC responses.
PNAS June 8, 2010 vol. 107 no. 23 10713-10718
http://www.pnas.org/content/107/23/10713.abstract?etoc
Insect Sensation
Unraveling the auditory system of Drosophila
References and further reading may be available for this article. To view references and further reading you must purchase this article.
Mala Murthya,
a Department of Molecular Biology and Princeton Neuroscience Institute,
Princeton University,
Acoustic communication in flies is based on the production and perception of courtship song. Drosophila males sing to females during the courtship ritual, while females listen for the correct species-specific song parameters before deciding to mate. While we know that song is important for mating, the neural mechanisms involved in song recognition remain mysterious. However, the last few years have seen major advances in our understanding of the auditory system of Drosophila, including delineation of the neurons involved in song production, detailed characterization of the auditory receptor organ, and mapping of auditory projections into the brain. The stage is being set to tackle the auditory system of Drosophila in much the same way as has been done for its olfactory system. This review covers recent work and discusses prospects for future research on Drosophila audition.
Current Opinion in Neurobiology Volume 20, Issue 3, June 2010, Pages 281-287
Multisensory systems integration for high-performance motor control in flies
References and further reading may be available for this article. To view references and further reading you must purchase this article.
Mark A Fryea,
a Howard Hughes Medical Institute, Department of Physiological Science,
Engineered tracking systems ‘fuse’ data from disparate sensor platforms, such as radar and video, to synthesize information that is more reliable than any single input. The mammalian brain registers visual and auditory inputs to directionally localize an interesting environmental feature. For a fly, sensory perception is challenged by the extreme performance demands of high speed flight. Yet even a fruit fly can robustly track a fragmented odor plume through varying visual environments, outperforming any human engineered robot. Flies integrate disparate modalities, such as vision and olfaction, which are neither related by spatiotemporal spectra nor processed by registered neural tissue maps. Thus, the fly is motivating new conceptual frameworks for how low-level multisensory circuits and functional algorithms produce high-performance motor control.
Current Opinion in Neurobiology Volume 20, Issue 3, June 2010, Pages 347-352
The dynein–tubulin motor powers active oscillations and amplification in the hearing organ of the mosquito
Ben Warren, Andrei N. Lukashkin and Ian J. Russell*i.j.russell@sussex.ac.uk
The design principles and specific proteins of the dynein–tubulin motor, which powers the flagella and cilia of eukaryotes, have been conserved throughout the evolution of life from algae to humans. Cilia and flagella can support both motile and sensory functions independently, or sometimes in parallel to each other. In this paper we show that this dual sensory–motile role of eukaryotic cilia is preserved in the most sensitive of all invertebrate hearing organs, the
Proc. R. Soc. B 7 June 2010 vol. 277 no. 1688 1761-1769
http://rspb.royalsocietypublishing.org/content/277/1688/1761.abstract
Insect Review
Exploiting predators for pest management: the need for sound ecological assessment
Michael J. Furlong* & Myron P. Zalucki m.furlong@uq.edu.au
School of Biological Sciences,
Most people agree that arthropod natural enemies are good for insect pest management in agriculture. However, the population suppressive effects of predators, which consume their prey and often leave no direct evidence of their activity, are more difficult to study than the effects of parasitoids, which can be sampled from host populations relatively easily. We critically reviewed field studies which investigated the relationship between lepidopteran pests and their associated predatory fauna, published in 11 leading entomology and applied ecology journals between 2003 and 2008. Each study was appraised to determine whether or not it demonstrated that predators had an impact on prey (pest) populations and, if so, whether it was conducted at an ecological scale relevant to pest management. Less than half (43%) of the 54 field studies adopted methodologies that allowed the impact of predators on target pest populations to be measured. Furthermore, 76% of the studies were conducted at the scale of experimental plots rather than at the ecological scale which determines pest and predator population dynamics or at which pest-management decisions are made. In almost one-third of the studies, predator abundance and/or diversity was measured, but this metric was not linked with pest suppression or mortality. We conclude that much current research does not provide evidence that predatory arthropods suppress target lepidopteran pest populations and, consequently, that it has little relevance to pest management. Well-designed ecological experiments combined with recent advances in molecular techniques to identify predator diets and the emergence of organic agriculture provide both the mechanisms and a platform upon which many predator–prey interactions can be investigated at a scale relevant to pest management. However, benefits will only be reaped from this opportunity if current approaches to research are changed and relevant ecological data are collected at appropriate ecological scales.
Entomologia Experimentalis et Applicata 2010 Volume 135 Issue 3, Pages 225 - 236
http://www3.interscience.wiley.com/journal/123356500/abstract
Insect Frontiers 2010 Vol2No6 Cover PDF
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