Insect Behaviour

Level of sperm competition promotes evolution of male ejaculate allocation patterns in a moth

 

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Fiona C. Ingleby^a, Zenobia Lewis^a and Nina Wedell ^{, a,}

^a Centre for Ecology and Conservation, University of Exeter, Cornwall Campus, U.K.

 

The risk and intensity of sperm competition can influence male adaptations that ultimately affect male fertilization success, for example investment in sperm production and strategic sperm allocation patterns. Previous studies have examined male behavioural responses to variation in immediate levels of sperm competition. Here we quantified the evolutionary responses of male adaptations resulting from long-term manipulation of the level of sperm competition. By varying the adult sex ratio of populations of the Indian meal moth, Plodia interpunctella, we successfully altered the frequency of male and female copulations, and thus the level of sperm competition experienced by males. As predicted by theory, males evolving under higher levels of sperm competition increased investment in sperm production and differed in their sperm allocation patterns across matings, compared to males evolving under intermediate and low levels of sperm competition. However, we found no evidence for trade-offs between ejaculate components, or between total sperm production and male body size in this species.

Animal Behaviour Volume 80, Issue 1, July 2010, Pages 37-43

http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6W9W-4YYGPSP-2&_user=10&_coverDate=07%2F31%2F2010&_rdoc=7&_fmt=high&_orig=browse&_srch=doc-info(%23toc%236693%232010%23999199998%232181760%23FLA%23display%23Volume)&_cdi=6693&_sort=d&_docanchor=&_ct=23&_acct=C000050221&_version=1&_urlVersion=0&_userid=10&md5=4242146e3026fde13908fd7292e16858

 

Male mate choice: why sequential choice can make its evolution difficult

 

References and further reading may be available for this article. To view references and further reading you must purchase this articleKatherine L. Barry^{a, ,} and Hanna Kokko^{b, c, 1}

^a Department of Biological Sciences, Macquarie University, Australia

^b Laboratory of Ecological and Evolutionary Dynamics, Department of Biological and Environmental Science, University of Helsinki, Finland

^c Ecology, Evolution & Genetics, Research School of Biology, Australian National University, Australia

 

Male reproductive success is typically mate limited, which implies that males should rarely be choosy. On the other hand, females often vary greatly in their fecundity or other determinants of male reproductive success. There are two coexisting threads in the current literature on male mate choice: a number of studies emphasize that male mate choice has been underappreciated in the past, while another set reminds us that it nevertheless evolves less easily than female choice. Here we show that when mate choice is sequential rather than simultaneous (which is often the case for the mate-limited sex), male mate choice may fail to evolve even if there is large variation among fitness prospects offered by various females, and when mating is very costly. Our model is inspired by the mating system of the sexually cannibalistic praying mantid Pseudomantis albofimbriata. Males of this species do not stop approaching females that have turned to face them even though this female behaviour greatly increases the risk of being cannibalized. We show that low mate availability can override the effect of all other factors that select for male mate choice: rejecting a current mating opportunity in the hope of better future opportunities is then not easily selected for. We conclude that studies of mate choice should examine why individuals refuse to take advantage of every opportunity, instead of merely focusing on the fact that some opportunities are better than others. Our results also call for more rigorous empirical tests of mate choice.

Animal Behaviour Volume 80, Issue 1, July 2010, Pages 163-169

http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6W9W-50819TH-2&_user=10&_coverDate=07%2F31%2F2010&_rdoc=22&_fmt=high&_orig=browse&_srch=doc-info(%23toc%236693%232010%23999199998%232181760%23FLA%23display%23Volume)&_cdi=6693&_sort=d&_docanchor=&_ct=23&_acct=C000050221&_version=1&_urlVersion=0&_userid=10&md5=0b4b218052b617025a2f4d358aca41e9

 

Foraging grass-cutting ants (Atta vollenweideri) maintain stability by balancing their loads with controlled head movements

 

Karin Moll¹  , Flavio Roces² and Walter Federle¹ km498@cam.ac.uk

Department of Zoology, University of Cambridge, Downing Street, Cambridge, CB2

Department of Behavioural Physiology and Sociobiology, Biocenter, University of Würzburg, Am Hubland, 97074 Würzburg, Germany 3EJ, UK

  

Grass-cutting ants (Atta vollenweideri) carry leaf fragments several times heavier and longer than the workers themselves over considerable distances back to their nest. Workers transport fragments in an upright, slightly backwards-tilted position. To investigate how they maintain stability and control the carried fragment’s position, we measured head and fragment positions from video recordings. Load-transporting ants often fell over, demonstrating the biomechanical difficulty of this behavior. Long fragments were carried at a significantly steeper angle than short fragments of the same mass. Workers did not hold fragments differently between the mandibles, but performed controlled up and down head movements at the neck joint. By attaching additional mass at the fragment’s tip to load-carrying ants, we demonstrated that they are able to adjust the fragment angle. When we forced ants to transport loads across inclines, workers walking uphill carried fragments at a significantly steeper angle, and downhill at a shallower angle than ants walking horizontally. However, we observed similar head movements in unladen workers, indicating a generalized reaction to slopes that may have other functions in addition to maintaining stability. Our results underline the importance of proximate, biomechanical factors for the understanding of the foraging process in leaf-cutting ants.

Journal of Comparative Physiology A: Neuroethology, Sensory, Neural, and Behavioral Physiology Volume 196, Number 7 / July, 2010 471-480

http://www.springerlink.com/content/w2411763657223p9/

 

Jumping mechanisms and performance of pygmy mole crickets (Orthoptera, Tridactylidae)

 

M. Burrows^1,* and M. D. Picker² mb135@hermes.cam.ac.uk

¹ Department of Zoology, University of Cambridge, Cambridge CB2 3EJ, UK
² Zoology Department, University of Cape Town, Private Bag X3, Rondebosch, 7701, Cape Town, South Africa

 

Pygmy mole crickets live in burrows at the edge of water and jump powerfully to avoid predators such as the larvae and adults of tiger beetles that inhabit the same microhabitat. Adults are 5–6 mm long and weigh 8 mg. The hind legs are dominated by enormous femora containing the jumping muscles and are 131% longer than the body. The ratio of leg lengths is: 1:2.1:4.5 (front:middle:hind, respectively). The hind tarsi are reduced and their role is supplanted by two pairs of tibial spurs that can rotate through 180 deg. During horizontal walking the hind legs are normally held off the ground. Jumps are propelled by extension of the hind tibiae about the femora at angular velocities of 68,000 deg s^–1 in 2.2 ms, as revealed by images captured at rates of 5000 s^–1. The two hind legs usually move together but can move asynchronously, and many jumps are propelled by just one hind leg. The take-off angle is steep and once airborne the body rotates backwards about its transverse axis (pitch) at rates of 100 Hz or higher. The take-off velocity, used to define the best jumps, can reach 5.4 m s^–1, propelling the insect to heights of 700 mm and distances of 1420 mm with an acceleration of 306 g. The head and pronotum are jerked rapidly as the body is accelerated. Jumping on average uses 116 µJ of energy, requires a power output of 50 mW and exerts a force of 20 mN. In jumps powered by one hind leg the figures are about 40% less.

Journal of Experimental Biology 213, 2386-2398 (2010)
http://jeb.biologists.org/cgi/content/abstract/213/14/2386

 

A syntax of hoverfly flight prototypes

 

Bart R. H. Geurten^1,*, Roland Kern^1,2, Elke Braun^1,2 and Martin Egelhaaf^1,2 bart.geurten@uni-bielefeld.de

¹ Neurobiology, Bielefeld University, PO Box 10 01 31, D-33501 Bielefeld, Germany
² Center of Excellence ‘Cognitive Interaction Technology’, Bielefeld University, PO Box 10 01 31, D-33501 Bielefeld, Germany

 

Hoverflies such as Eristalis tenax Linnaeus are known for their distinctive flight style. They can hover on the same spot for several seconds and then burst into movement in apparently any possible direction. In order to determine a quantitative and structured description of complex flight manoeuvres, we searched for a set of repeatedly occurring prototypical movements (PMs) and a set of rules for their ordering. PMs were identified by applying clustering algorithms to the translational and rotational velocities of the body of Eristalis during free-flight sequences. This approach led to nine stable and reliable PMs, and thus provided a tremendous reduction in the complexity of behavioural description. This set of PMs together with the probabilities of transition between them constitute a syntactical description of flight behaviour. The PMs themselves can be roughly segregated into fast rotational turns (saccades) and a variety of distinct translational movements (intersaccadic intervals). We interpret this segregation as reflecting an active sensing strategy which facilitates the extraction of spatial information from retinal image displacements. Detailed analysis of saccades shows that they are performed around all rotational axes individually and in all possible combinations. We found the probability of occurrence of a given saccade type to depend on parameters such as the angle between the long body axis and the direction of flight.

Journal of Experimental Biology 213, 2461-2475 (2010)
http://jeb.biologists.org/cgi/content/abstract/213/14/2461

 

Object preference by walking fruit flies, Drosophila melanogaster, is mediated by vision and graviperception

 

Alice A. Robie^*, Andrew D. Straw and Michael H. Dickinson arobie@gmail.com

Department of Biology, California Institute of Technology, MC 138-78, 1200 E. California Blvd, Pasadena, CA 91125, USA

 

Walking fruit flies, Drosophila melanogaster, use visual information to orient towards salient objects in their environment, presumably as a search strategy for finding food, shelter or other resources. Less is known, however, about the role of vision or other sensory modalities such as mechanoreception in the evaluation of objects once they have been reached. To study the role of vision and mechanoreception in exploration behavior, we developed a large arena in which we could track individual fruit flies as they walked through either simple or more topologically complex landscapes. When exploring a simple, flat environment lacking three-dimensional objects, flies used visual cues from the distant background to stabilize their walking trajectories. When exploring an arena containing an array of cones, differing in geometry, flies actively oriented towards, climbed onto, and explored the objects, spending most of their time on the tallest, steepest object. A fly's behavioral response to the geometry of an object depended upon the intrinsic properties of each object and not a relative assessment to other nearby objects. Furthermore, the preference was not due to a greater attraction towards tall, steep objects, but rather a change in locomotor behavior once a fly reached and explored the surface. Specifically, flies are much more likely to stop walking for long periods when they are perched on tall, steep objects. Both the vision system and the antennal chordotonal organs (Johnston's organs) provide sufficient information about the geometry of an object to elicit the observed change in locomotor behavior. Only when both these sensory systems were impaired did flies not show the behavioral preference for the tall, steep objects.

Journal of Experimental Biology 213, 2494-2506 (2010)
http://jeb.biologists.org/cgi/content/abstract/213/14/2494

 

Form and nature of precopulatory sexual selection in both sexes of a moth

 

Jin Xu¹ and Qiao Wang¹  Q.Wang@massey.ac.nz

Institute of Natural Resources, Massey University, Private Bag 11222, Palmerston North, New Zealand

  

Sexual selection is a process that operates through intrasexual competition and intersexual choice for reproduction in both sexes. Here, we report our work on a polygamous moth, Ephestia kuehniella Zeller (Lepidoptera: Pyralidae), aiming to infer the form and nature of precopulatory sexual selection in males and females. We show that, although a number of traits measured in each sex are correlated with mating success, the primary selection trait in females appears to be abdominal thickness and that in males is aedeagus length. As the female’s abdominal thickness is a reliable signal about the number and developmental stage of eggs, males who select females with thicker abdomens for mating will gain reproductive benefit, i.e., fertilizing more mature eggs. For females, earlier maturation of their eggs makes the females more likely to achieve mating earlier in an uncertain world where there is no guarantee that they will find more males in the future. Sexual selection appears to be the important force behind the evolution of fast egg maturation in females. We show that, under a male-biased sex ratio, more than 20% of mating fails within a few minutes after the aedeagus has penetrated into the female’s genitalia, suggesting that females can assess the features of the male aedeagus before allowing insemination to occur. Dissection and examination of both sexes suggest that a longer aedeagus enhances mating and fertilization efficiency in this species, supporting the notion that sexual selection is a primary force in the evolution of genital variance.

Naturwissenschaften Volume 97, Number 7 / July, 2010 617-625

http://www.springerlink.com/content/h2562wg303505k83/

 

Aerial manoeuvrability in wingless gliding ants (Cephalotes atratus)

 

Stephen P. Yanoviak1,*, Yonatan Munk2, Mike Kaspari3,4 and Robert Dudley2,4 spyanoviak@ualr.edu

¹Department of Biology, University of Arkansas at Little Rock, 2801 S. University Avenue, Little Rock, AR 72204, USA

²Department of Integrative Biology, University of California, Berkeley, CA 94720, USA

³EEB Graduate Program, Department of Zoology, University of Oklahoma, Norman, OK 73019, USA

⁴Smithsonian Tropical Research Institute, PO Box 2072, Balboa, Republic of Panama

 

In contrast to the patagial membranes of gliding vertebrates, the aerodynamic surfaces used by falling wingless ants to direct their aerial descent are unknown. We conducted ablation experiments to assess the relative contributions of the hindlegs, midlegs and gaster to gliding success in workers of the Neotropical arboreal ant Cephalotes atratus (Hymenoptera: Formicidae). Removal of hindlegs significantly reduced the success rate of directed aerial descent as well as the glide index for successful flights. Removal of the gaster alone did not significantly alter performance relative to controls. Equilibrium glide angles during successful targeting to vertical columns were statistically equivalent between control ants and ants with either the gaster or the hindlegs removed. High-speed video recordings suggested possible use of bilaterally asymmetric motions of the hindlegs to effect body rotations about the vertical axis during targeting manoeuvre. Overall, the control of gliding flight was remarkably robust to dramatic anatomical perturbations, suggesting effective control mechanisms in the face of adverse initial conditions (e.g. falling upside down), variable targeting decisions and turbulent wind gusts during flight.

Proc. R. Soc. B 22 July 2010 vol. 277 no. 1691 2199-2204

http://rspb.royalsocietypublishing.org/content/277/1691/2199.abstract

 

Insect Biochemistry

Alternative Tasks of Drosophila Tan in Neurotransmitter Recycling Versus Cuticle Sclerotization Disclosed by Kinetic Properties^*

 

Silvia Aust,Florian Brüsselbach, Stefanie Pütz and Bernhard T. Hovemann¹ bernhard.hovemann@rub.de

From the Faculty of Chemistry and Biochemistry, AG Molekulare Zellbiochemie, Ruhr-Universität Bochum, D-44780 Bochum, Germany

 

Upon a stimulus of light, histamine is released from Drosophila photoreceptor axonal endings. It is taken up into glia where Ebony converts it into β-alanyl-histamine (carcinine). Carcinine moves into photoreceptor cells and is there cleaved into β-alanine and histamine by Tan activity. Tan thus provides a key function in the recycling pathway of the neurotransmitter histamine. It is also involved in the process of cuticle formation. There, it cleaves β-alanyl-dopamine, a major component in cuticle sclerotization. Active Tan enzyme is generated by a self-processing proteolytic cleavage from a pre-protein at a conserved Gly-Cys sequence motif. We confirmed the dependence on the Gly-Cys motif by in vitro mutagenesis. Processing time delays the rise to full Tan activity up to 3 h behind its putative circadian RNA expression in head. To investigate its pleiotropic functions, we have expressed Tan as a His₆ fusion protein in Escherichia coli and have purified it to homogeneity. We found wild type and mutant His₆-Tan protein co-migrating in size exclusion chromatography with a molecular weight compatible with homodimer formation. We conclude that dimer formation is preceding pre-protein processing. Drosophila tan¹ null mutant analysis revealed that amino acid Arg²¹⁷ is absolutely required for processing. Substitution of Met²⁵⁶ in tan⁵, on the contrary, does not affect processing extensively but renders it prone to degradation. This also leads to a strong tan phenotype although His₆-Tan⁵ retains activity. Kinetic parameters of Tan reveal characteristic differences in K_m and k_cat values of carcinine and β-alanyl-dopamine cleavage, which conclusively illustrate the divergent tasks met by Tan.

The Journal of Biological Chemistry, 285, 20740-20747. July 2, 2010

http://www.jbc.org/content/285/27/20740.abstract

 

Disruption of Lysosome Function Promotes Tumor Growth and Metastasis in Drosophila^*

 

Congwu Chi^‡,¹, Huanhu Zhu^‡,¹, Min Han^‡§,², Yuan Zhuang^‡¶, Xiaohui Wu^‡,³ and Tian Xu^‡‖,²,⁴ xiaohui_wu@fudan.edu.cn tian.xu@yale.edu

From the ^‡Institute of Developmental Biology and Molecular Medicine, Fudan-Yale Center for Biomedical Research, School of Life Science, Fudan University, Shanghai 200433, China,

the ^§Howard Hughes Medical Institute, Department of Molecular, Cellular, and Developmental Biology, University of Colorado, Boulder, Colorado 80309-0347,

the ^¶Department of Immunology, Duke University Medical Center, Durham, North Carolina 27701, and

the ^‖Howard Hughes Medical Institute, Department of Genetics, Yale University School of Medicine, New Haven, Connecticut 06536

 

Lysosome function is essential to many physiological processes. It has been suggested that deregulation of lysosome function could contribute to cancer. Through a genetic screen in Drosophila, we have discovered that mutations disrupting lysosomal degradation pathway components contribute to tumor development and progression. Loss-of-function mutations in the Class C vacuolar protein sorting (VPS) gene, deep orange (dor), dramatically promote tumor overgrowth and invasion of the Ras^V12 cells. Knocking down either of the two other components of the Class C VPS complex, carnation (car) and vps16A, also renders Ras^V12 cells capable for uncontrolled growth and metastatic behavior. Finally, chemical disruption of the lysosomal function by feeding animals with antimalarial drugs, chloroquine or monensin, leads to malignant tumor growth of the Ras^V12 cells. Taken together, our data provide evidence for a causative role of lysosome dysfunction in tumor growth and invasion and indicate that members of the Class C VPS complex behave as tumor suppressors.

The Journal of Biological Chemistry, 285, 21817-21823. July 9, 2010

http://www.jbc.org/content/285/28/21817.abstract

 

Insect Biophysics

Effects of wing deformation on aerodynamic forces in hovering hoverflies

 

Gang Du^* and Mao Sun dugang@buaa.edu.cn

Ministry-of-Education Key Laboratory of Fluid Mechanics, Beijing University of Aeronautics and Astronautics, Beijing, China

 

We studied the effects of wing deformation on the aerodynamic forces of wings of hovering hoverflies by solving the Navier–Stokes equations on a dynamically deforming grid, employing the recently measured wing deformation data of hoverflies in free-flight. Three hoverflies were considered. By taking out the camber deformation and the spanwise twist deformation one by one and by comparing the results of the deformable wing with those of the rigid flat-plate wing (the angle of attack of the rigid flat-plate wing was equal to the local angle of attack at the radius of the second moment of wing area of the deformable wing), effects of camber deformation and spanwise twist were identified. The main results are as follows. For the hovering hoverflies considered, the time courses of the lift, drag and aerodynamic power coefficients of the deformable wing are very similar to their counterparts of the rigid flat-plate wing, although lift of the deformable wing is about 10% larger, and its aerodynamic power required about 5% less than that of the rigid flat-plate wing. The difference in lift is mainly caused by the camber deformation, and the difference in power is mainly caused by the spanwise twist. The main reason that the deformation does not have a very large effect on the aerodynamic force is that, during hovering, the wing operates at a very high angle of attack (about 50 deg) and the flow is separated, and separated flow is not very sensitive to wing deformation. Thus, as a first approximation, the deformable wing in hover flight could be modeled by a rigid flat-plate wing with its angle of attack being equal to the local angle of attack at the radius of second moment of wing area of the deformable wing.

Journal of Experimental Biology 213, 2273-2283 (2010)
http://jeb.biologists.org/cgi/content/abstract/213/13/2273

 

Hysteresis in the production of force by larval Dipteran muscle

 

Bethany A. Paterson¹, Ilya Marko Anikin² and Jacob L. Krans^2,* kransjal@mail.ccsu.edu

¹ Department of Biological Science, Mount Holyoke College, South Hadley, MA 01075, USA
² Department of Biology, Central Connecticut State University, New Britain, CT 06050, USA

 

We describe neuromuscular hysteresis – the dependence of muscle force on recent motoneuron activity – in the body wall muscles of larval Sarcophaga bullata and Drosophila melanogaster. In semi-intact preparations, isometric force produced by a train of nerve impulses at a constant rate was significantly less than that produced by the same train of stimuli with a brief (200 ms) high-frequency burst of impulses interspersed. Elevated force did not decay back to predicted values after the burst but instead remained high throughout the duration of the stimulus train. The increased force was not due to a change in excitatory junction potentials (EJPs); EJP voltage and time course before and after the high-frequency burst were not statistically different. Single muscle and semi-intact preparations exhibited hysteresis similarly, suggesting that connective tissues of the origin or insertion are not crucial to the mechanism of hysteresis. Hysteresis was greatest at low motoneuron rates – yielding a ~100% increase over predicted values based on constant-rate stimulation alone – and decreased as impulse rate increased. We modulated motoneuron frequency rhythmically across rates and cycle periods similar to those observed during kinematic analysis of larval crawling. Positive force hysteresis was also evident within these more physiological activation parameters.

Journal of Experimental Biology 213, 2483-2493 (2010)
http://jeb.biologists.org/cgi/content/abstract/213/14/2483

 

Insect Biological Control

Monitoring long-term evolutionary changes following Wolbachia introduction into a novel host: the Wolbachia popcorn infection in Drosophila simulans

 

Lauren B. Carrington*†, Ary A. Hoffmann and Andrew R. Weeks lbcarrington@ucdavis.edu

Centre for Environmental Stress and Adaptation Research (CESAR), Department of Genetics, University of Melbourne, Victoria 3010, Australia

 

Wolbachia may act as a biological control agent for pest management; in particular, the Wolbachia variant wMelPop (popcorn) shortens host longevity and may be useful for dengue suppression. However, long-term changes in the host and Wolbachia genomes can alter Wolbachia spread and/or host effects that suppress disease. Here, we investigate the phenotypic effects of wMelPop in a non-native host, Drosophila simulans, following artificial transinfection approximately 200 generations ago. Long-term rearing and maintenance of the bacteria were at 19°C in the original I-102 genetic background that was transinfected with the popcorn strain. The bacteria were then introgressed into three massbred backgrounds, and tetracycline was used to create uninfected sublines. The effect of wMelPop on longevity in this species appears to have changed; longevity was no longer reduced at 25°C in some nuclear backgrounds, reflecting different geographical origin, selection or drift, although the reduction was still evident for flies held at 30°C. Wolbachia influenced productivity and viability, and development time in some host backgrounds. These findings suggest that long-term attenuation of Wolbachia effects may compromise the effectiveness of this bacterium in pest control. They also emphasize the importance of host nuclear background on Wolbachia phenotypic effects.

Proc. R. Soc. B 7 July 2010 vol. 277 no. 1690 2059-2068

http://rspb.royalsocietypublishing.org/content/277/1690/2059.abstract

 

Insect Development

Modeling bistable cell-fate choices in the Drosophila eye: qualitative and quantitative perspectives

 

Thomas G. W. Graham1, S. M. Ali Tabei2, Aaron R. Dinner2 and Ilaria Rebay1,* irebay@uchicago.edu

¹Ben May Department for Cancer Research, University of Chicago, 929 East 57th Street, Chicago, IL 60637, USA

²James Franck Institute, University of Chicago, 929 East 57th Street, Chicago, IL 60637, USA

 

A major goal of developmental biology is to understand the molecular mechanisms whereby genetic signaling networks establish and maintain distinct cell types within multicellular organisms. Here, we review cell-fate decisions in the developing eye of Drosophila melanogaster and the experimental results that have revealed the topology of the underlying signaling circuitries. We then propose that switch-like network motifs based on positive feedback play a central role in cell-fate choice, and discuss how mathematical modeling can be used to understand and predict the bistable or multistable behavior of such networks.

Development 137, 2265-2278. July 15, 2010

http://dev.biologists.org/content/137/14/2265.abstract

 

Influence of Fat-Hippo and Notch signaling on the proliferation and differentiation of Drosophila optic neuroepithelia

 

B. V. V. G. Reddy, Cordelia Rauskolb and Kenneth D. Irvine* irvine@waksman.rutgers.edu

Howard Hughes Medical Institute, Waksman Institute and Department of Molecular Biology and Biochemistry, Rutgers, The State University of New Jersey, Piscataway, NJ 08854, USA

 

The Drosophila optic lobe develops from neuroepithelial cells, which function as symmetrically dividing neural progenitors. We describe here a role for the Fat-Hippo pathway in controlling the growth and differentiation of Drosophila optic neuroepithelia. Mutation of tumor suppressor genes within the pathway, or expression of activated Yorkie, promotes overgrowth of neuroepithelial cells and delays or blocks their differentiation; mutation of yorkie inhibits growth and accelerates differentiation. Neuroblasts and other neural cells, by contrast, appear unaffected by Yorkie activation. Neuroepithelial cells undergo a cell cycle arrest before converting to neuroblasts; this cell cycle arrest is regulated by Fat-Hippo signaling. Combinations of cell cycle regulators, including E2f1 and CyclinD, delay neuroepithelial differentiation, and Fat-Hippo signaling delays differentiation in part through E2f1. We also characterize roles for Jak-Stat and Notch signaling. Our studies establish that the progression of neuroepithelial cells to neuroblasts is regulated by Notch signaling, and suggest a model in which Fat-Hippo and Jak-Stat signaling influence differentiation by their acceleration of cell cycle progression and consequent impairment of Delta accumulation, thereby modulating Notch signaling. This characterization of Fat-Hippo signaling in neuroepithelial growth and differentiation also provides insights into the potential roles of Yes-associated protein in vertebrate neural development and medullablastoma.

Development 137, 2397-2408. July 15, 2010

http://dev.biologists.org/content/137/14/2397.abstract

 

Insect Ecology

Dispersal capacity and diet breadth modify the response of wild bees to habitat loss

 

Riccardo Bommarco1,*, Jacobus C. Biesmeijer2,3, Birgit Meyer4, Simon G. Potts5, Juha Pöyry6, Stuart P. M. Roberts5, Ingolf Steffan-Dewenter4 and Erik Öckinger1 riccardo.bommarco@ekol.slu.se

¹Department of Ecology, Swedish University of Agricultural Sciences, 75007 Uppsala, Sweden

²Institute of Integrative and Comparative Biology, Leeds LS2 9JT, UK

³Earth and Biosphere Institute, University of Leeds, Leeds LS2 9JT, UK

⁴Population Ecology Group, Department of Animal Ecology I, University of Bayreuth, 95440 Bayreuth, Germany

⁵Centre for Agri-Environmental Research, School of Agriculture, Policy and Development, University of Reading, RG6 6AR, UK

⁶Finnish Environment Institute, Research Programme for Biodiversity, 00251 Helsinki, Finland

 

Habitat loss poses a major threat to biodiversity, and species-specific extinction risks are inextricably linked to life-history characteristics. This relationship is still poorly documented for many functionally important taxa, and at larger continental scales. With data from five replicated field studies from three countries, we examined how species richness of wild bees varies with habitat patch size. We hypothesized that the form of this relationship is affected by body size, degree of host plant specialization and sociality. Across all species, we found a positive species–area slope (z = 0.19), and species traits modified this relationship. Large-bodied generalists had a lower z value than small generalists. Contrary to predictions, small specialists had similar or slightly lower z value compared with large specialists, and small generalists also tended to be more strongly affected by habitat loss as compared with small specialists. Social bees were negatively affected by habitat loss (z = 0.11) irrespective of body size. We conclude that habitat loss leads to clear shifts in the species composition of wild bee communities.

Proc. R. Soc. B 7 July 2010 vol. 277 no. 1690 2075-2082

http://rspb.royalsocietypublishing.org/content/277/1690/2075.abstract

 

Insect Evolution

A developmental perspective on the evolution of sexual size dimorphism of a moth

 

R. Craig Stillwell* and Goggy Davidowitz rcstill@email.arizona.edu

Department of Entomology, University of Arizona, Tucson, AZ 85721-0036, USA

 

Males and females of almost all organisms exhibit sexual differences in body size, a phenomenon called sexual size dimorphism (SSD). How the sexes evolve to be different sizes, despite sharing the same genes that control growth and development, and hence a common genetic architecture, has remained elusive. Here, we show that the genetic architecture (heritabilities and genetic correlations) of the physiological mechanism that regulates size during the last stage of larval development of a moth, differs between the sexes, and thus probably facilitates, rather than hinders, the evolution of SSD. We further show that the endocrine system plays a critical role in generating SSD. Our results demonstrate that knowledge of the genetic architecture underlying the physiological process during development that ultimately produces SSD in adults can elucidate how males and females of organisms evolve to be of different sizes.

Proc. R. Soc. B 7 July 2010 vol. 277 no. 1690 2069-2074

http://rspb.royalsocietypublishing.org/content/277/1690/2069.abstract

 

Insect Genetics

Effect of laboratory acclimation on the variation of reproduction-related characters in Drosophila melanogaster

 

Benjamin Houot¹, Nicolas Svetec¹, Raùl Godoy-Herrera² and Jean-François Ferveur^1,* jean-francois.ferveur@u-bourgogne.fr

¹ Unité Mixte de Recherche 6265 Associée au Centre National de la Recherche Scientifique, Université de Bourgogne, Faculté des Sciences, 6, Bd Gabriel, 21 000 Dijon, France
² Instituto de Ciencias, Biomédicas, Facultad de Medicina, Universidad de Chile, Independencia 1027, Santiago-7, Casilla 70061, Chile

 

The natural variation of sex-specific characters between populations can favor their behavioral isolation, eventually leading to the formation of new species. Marked variations for male courtship, mating and the production of sex pheromones – three complex characters potentially inducing sexual isolation – were found between Drosophila melanogaster populations of various origins acclimated for many generations in research laboratories. However, the natural variation of these three characters between natural populations and their evolution after long-term acclimation in the laboratory remains unknown. We measured many traits involved in these characters in six stocks initiated with distinct populations sampled in a restricted geographic area. Several sex-specific traits varied between stocks freshly brought back to the laboratory. After 100 generations spent in the laboratory without any experimental selection, traits varied in a strain-dependent manner. This variation was not related to a reduction of their variance except for copulation duration. This indicates that reproduction-related characters can diverge between neighboring D. melanogaster populations, and differently adapt to stable laboratory conditions.

Journal of Experimental Biology 213, 2322-2331 (2010)
http://jeb.biologists.org/cgi/content/abstract/213/13/2322

 

Insect Learning

Olfactory learning in the stingless bee Tetragonisca angustula (Hymenoptera, Apidae, Meliponini)

 

S. I. Mc Cabe¹ and W. M. Farina¹  walter@fbmc.fcen.uba.ar

Grupo de Estudio de Insectos Sociales, Departamento de Biodiversidad y Biología Experimental, IFIBYNE-CONICET, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Pabellón II, Ciudad Universitaria, C1428EHA Buenos Aires, Argentina

  

Tetragonisca angustula stingless bees are considered as solitary foragers that lack specific communication strategies. In their orientation towards a food source, these social bees use chemical cues left by co-specifics and the information obtained in previous foraging trips by the association of visual stimuli with the food reward. Here, we investigated their ability to learn the association between odors and reward (sugar solution) and the effect on learning of previous encounters with scented food either inside the hive or during foraging. During food choice experiments, when the odor associated with the food was encountered at the feeding site, the bees’ choice is biased to the same odor afterwards. The same was not the case when scented food was placed inside the nest. We also performed a differential olfactory conditioning of proboscis extension response with this species for the first time. Inexperienced bees did not show significant discrimination levels. However, when they had had already interacted with scented food inside the hive, they were able to learn the association with a specific odor. Possible olfactory information circulation inside the hive and its use in their foraging strategies is discussed.

Journal of Comparative Physiology A: Neuroethology, Sensory, Neural, and Behavioral Physiology Volume 196, Number 7 / July, 2010 481-490

http://www.springerlink.com/content/d48v6wmr017086n5/

 

Insect metabolism

Controlling anoxic tolerance in adult Drosophila via the cGMP–PKG pathway

 

K. Dawson-Scully^1,*, D. Bukvic², M. Chakaborty-Chatterjee², R. Ferreira², S. L. Milton¹ and M. B. Sokolowski² ken.dawson-scully@fau.edu

¹ Department of Biological Sciences, Florida Atlantic University, Boca Raton, FL 33431, USA
² Department of Biology, University of Toronto, Mississauga, ON, Canada, L5L1C6

 

In this study we identify a cGMP-dependent protein kinase (PKG) cascade as a biochemical pathway critical for controlling low-oxygen tolerance in the adult fruit fly, Drosophila melanogaster. Even though adult Drosophila can survive in 0% oxygen (anoxia) environments for hours, air with less than 2% oxygen rapidly induces locomotory failure resulting in an anoxic coma. We use natural genetic variation and an induced mutation in the foraging (for) gene, which encodes a Drosophila PKG, to demonstrate that the onset of anoxic coma is correlated with PKG activity. Flies that have lower PKG activity demonstrate a significant increase in time to the onset of anoxic coma. Further, in vivo pharmacological manipulations reveal that reducing either PKG or protein phosphatase 2A (PP2A) activity increases tolerance of behavior to acute hypoxic conditions. Alternatively, PKG activation and phosphodiesterase (PDE5/6) inhibition significantly reduce the time to the onset of anoxic coma. By manipulating these targets in paired combinations, we characterized a specific PKG cascade, with upstream and downstream components. Further, using genetic variants of PKG expression/activity subjected to chronic anoxia over 6 h, ~50% of animals with higher PKG activity survive, while only ~25% of those with lower PKG activity survive after a 24 h recovery. Therefore, in this report we describe the PKG pathway and the differential protection of function vs survival in a critically low oxygen environment.

Journal of Experimental Biology 213, 2410-2416 (2010)
http://jeb.biologists.org/cgi/content/abstract/213/14/2410

 

Insect Molecular Ecology

Structured populations of the oriental fruit moth in an agricultural ecosystem

 

MARCO V. G. TORRIANI, DOMINIQUE MAZZI, SILKE HEIN and SILVIA DORN dominique.mazzi@ipw.agrl.ethz.ch

ETH Zurich, Institute of Plant, Animal and Agroecosystem Sciences, Applied Entomology, Schmelzbergstrasse 9, 8092 Zurich, Switzerland

 

Intercontinental trade has led to multiple introductions of invasive pest species at a global scale. Molecular analyses of the structure of populations support the understanding of ecological strategies and evolutionary patterns that promote successful biological invasions. The oriental fruit moth, Grapholita (=Cydia) molesta, is a cosmopolitan and economically destructive pest of stone and pome fruits, expanding its distribution range concomitantly with global climate warming. We used ten newly developed polymorphic microsatellite markers to examine the genetic structure of G. molesta populations in an agricultural ecosystem in the Emilia-Romagna region of northern Italy. Larvae collected in eight sampling sites were assigned to a mosaic of five populations with significant intra-regional structure. Inferred measures of gene flow within populations implicated both active dispersal, and passive dispersal associated with accidental anthropogenic displacements. Small effective population sizes, coupled with high inbreeding levels, highlighted the effect of orchard management practices on the observed patterns of genetic variation within the sampling sites. Isolation by distance did not appear to play a major role at the spatial scale considered. Our results provide new insights into the population genetics and dynamics of an invasive pest species at a regional scale.

Molecular Ecology 2010 Volume 19 Issue 13, Pages 2651 - 2660

http://www3.interscience.wiley.com/journal/123532805/abstract

 

Conservation genetics, foraging distance and nest density of the scarce Great Yellow Bumblebee (Bombus distinguendus)

 

THOMAS G. CHARMAN*¹, JANE SEARS†, RHYS E. GREEN*† and ANDREW F. G. BOURKE‡² a.bourke@uea.ac.uk

  *Department of Zoology, University of Cambridge, Downing Street, Cambridge CB2 3EJ, UK ,   †Royal Society for the Protection of Birds, The Lodge, Sandy, Bedfordshire SG19 2DL, UK ,   ‡Institute of Zoology, Zoological Society of London, Regent's Park, London NW1 4RY, UK

 

The conservation genetics of bees is of particular interest because many bee species are in decline, so jeopardizing the essential ecosystem service of plant pollination that they provide. In addition, as social haplodiploids, inbred bees may be vulnerable to the extra genetic load represented by the production of sterile diploid males. Using microsatellite markers, we investigated the genetic structure of populations of the Great Yellow Bumblebee (Bombus distinguendus Morawitz) in the UK, where this species has undergone a precipitous decline. By means of a mixture of analytical methods and simulation, we also extended—and then applied—genetic methods for estimating foraging distance and nest density in wild bees. B. distinguendus populations were characterized by low expected heterozygosity and allelic richness, inbreeding coefficients not significantly different from zero, absence of detected diploid males, absence of substantial demographic bottlenecking, and population substructuring at large (c. 100+ km) but not small (10s of km) spatial scales. The minimum average effective population size at our sampling sites was low (c. 25). In coastal grassland (machair), the estimated modal foraging distance of workers was 391 m, with 95% of foraging activity occurring within 955 m of the nest, and estimated nest density was 19.3 nests km^-2. These findings show that B. distinguendus exhibits some genetic features of scarce, declining or fragmented populations. Moreover, B. distinguendus workers appear to forage over above-average distances and nests remain thinly distributed even in current strongholds. These considerations should inform future conservation actions for this and similar species.

Molecular Ecology 2010 Volume 19 Issue 13, Pages 2661 - 2674

http://www3.interscience.wiley.com/journal/123532797/abstract

 

Ficus racemosa is pollinated by a single population of a single agaonid wasp species in continental South-East Asia

 

N. KOBMOO*, M. HOSSAERT-MCKEY*, J. Y. RASPLUS† and F. KJELLBERG* kobmoo@cefe.cnrs.fr, nkobmoo@gmail.com

  *Centre d'Ecologie Fonctionnelle et Evolutive (CEFE), UMR-CNRS 5175, 1919 route de Mende, 34293 Montpellier Cedex 5, France ,   †CBGP, Campus International de Baillarguet CS 30016, 34988 Montferrier-sur-Lez, France

 

High specificity in the Ficus-agaonid wasp mutualism has lead to the assumption of a mostly 'one-to-one' relationship, albeit with some exceptions. This view has been challenged by new molecular data in recent years, but surprisingly little is known about local and spatial genetic structuring of agaonid wasp populations. Using microsatellite markers, we analysed genetic structuring of Ceratosolen fusciceps, the fig wasp pollinating Ficus racemosa, a fig tree species widely distributed from India to Australia. In sampling stretching from the south of China to the south of Thailand we found evidence for only a single pollinating wasp species in continental South-East Asian mainland. We found no evidence for the co-occurrence of cryptic species within our subcontinent sampling zone. We observed no spatial genetic structure within sites and only limited structuring over the whole sampling zone, suggesting that F. racemosa is pollinated by a single population of a single agaonid wasp species all over continental South-East Asia. An additional sample of wasps collected on F. racemosa in Australia showed clear-cut genetic differentiation from the Asian continent, suggesting allopatric divergence into subspecies or species. We propose that the frequent local co-occurrence of sister species found in the literature mainly stems from contact zones between biogeographic regions, and that a single pollinator species over wide areas might be the more common situation everywhere else.

Molecular Ecology 2010 Volume 19 Issue 13, Pages 2700 - 2712

http://www3.interscience.wiley.com/journal/123538955/abstract

 

Macrogeographic population structuring in the cosmopolitan agricultural pest Bactrocera cucurbitae (Diptera: Tephritidae)

 

M. VIRGILIO*†, H. DELATTE‡, T. BACKELJAU†§ and M. DE MEYER* massimiliano.virgilio@africamuseum.be

  *Royal Museum for Central Africa, Leuvensesteenweg 13, B-3080 Tervuren, Belgium ,   †Royal Belgian Institute of Natural Sciences, Vautierstraat 29, B-1000 Brussels, Belgium ,   ‡UMR C53 PVBMT CIRAD-Université de la Réunion, CIRAD Pôle de Protection des Plantes ,   §Department of Biology, University of Antwerp, Groenenborgerlaan 171, B-2020 Antwerp, Belgium

 

The macrogeographic population structure of the agricultural pest Bactrocera cucurbitae (Diptera: Tephritidae) was investigated in order to identify the geographic origin of the species and reconstruct its range expansion. Individuals of B. cucurbitae were collected from 25 worldwide-distributed localities (n = 570) and genotyped at 13 microsatellite loci. The Bayesian clustering reveals that B. cucurbitae can be subdivided into five main groups corresponding to populations from (i) the African continent, (ii) La Réunion, (iii) Central Asia, (iv) East Asia and (v) Hawaii. The proportions of inter-regional assignments and the higher values of genetic diversity in populations from Pakistan, India and Bangladesh suggest that B. cucurbitae originated in Central Asia and expanded its range to East Asia and Hawaii on one hand and to Africa and the islands of the Indian Ocean on the other. A number of outliers (10–19 specimens according to different clustering algorithms) show high levels of admixture (Q > 0.70) with populations from different regions and reveal complex patterns of inter-regional gene flow. Anthropogenic transport is the most plausible promoter of this large-scale dispersal. The introduction of individuals from geographically distant sources did not have a relevant role in the most recent African invasions, which originated from the expansion of local populations. These results could provide a useful background to better evaluate invasion risks and establish priorities for the management of this cosmopolitan agricultural pest.

Molecular Ecology 2010 Volume 19 Issue 13, Pages 2713 - 2724

http://www3.interscience.wiley.com/journal/123538958/abstract

 

Maternity of emergency queens in the Cape honey bee, Apis mellifera capensis

 

MICHAEL J. HOLMES*, BENJAMIN P. OLDROYD*, MICHAEL H. ALLSOPP†, JULIANNE LIM*, THERESA C. WOSSLER‡ and MADELEINE BEEKMAN* madeleine.beekman@sydney.edu.au

  *Behaviour and Genetics of Social Insects Lab, School of Biological Sciences A12, University of Sydney, Sydney, NSW 2006, Australia ,   †Honey Bee Research Section, ARC-Plant Protection Research Institute, Private Bag X5017, Stellenbosch 7599, South Africa ,   ‡Centre for Invasion Biology, Department of Botany and Zoology, University of Stellenbosch, Private Bag X1, Matieland 7602, South Africa

 

During reproductive swarming, some workers of the Cape honey bee, Apis mellifera capensis, lay eggs in queen cells, many of which are reared to maturity. However, it is unknown if workers are able to lay in queen cells immediately after queen loss during an episode of emergency queen rearing. In this study we experimentally de-queened colonies and determined the maternity of larvae and pupae that were reared as queens. This allowed us to determine how soon after queen loss workers contribute to the production of new queens. We were further interested to see if workers would preferentially raise new queens from queen-laid brood if this was introduced later. We performed our manipulations in two different settings: an apiary setting where colonies were situated close together and a more natural situation in which the colonies were well separated. This allowed us to determine how the vicinity of other colonies affects the presence of parasites. We found that workers do indeed contribute to queen cell production immediately after the loss of their queen, thus demonstrating that some workers either have activated ovaries even when their colony has a queen or are able to activate their ovaries extremely rapidly. Queen-laid brood introduced days after queen loss was ignored, showing that workers do not prefer to raise new queens from queen brood when given a choice. We also detected non-natal parasitism of queen cells in both settings. We therefore conclude that some A. m. capensis genotypes specialize in parasitizing queen cells.

Molecular Ecology 2010 Volume 19 Issue 13, Pages 2792 - 2799

http://www3.interscience.wiley.com/journal/123511854/abstract

 

 

Insect Neuroethology

Neuropeptides in the Drosophila central complex in modulation of locomotor behavior

 

Lily Kahsai¹, Jean-René Martin² and Åsa M. E. Winther^1,* asa.winther@zoologi.su.se

¹ Department of Zoology, Stockholm University, Svante Arrhenius väg 18B, S-106 91 Stockholm, Sweden
² Imagerie Cérébrale Fonctionnelle et Comportements, CNRS, N&D, UPR-3294, Gif-sur-

 

The central complex is one of the most prominent neuropils in the insect brain. It has been implicated in the control of locomotor activity and is considered as a pre-motor center. Several neuropeptides are expressed in circuits of the central complex, and thus may be modulators of locomotor behavior. Here we have investigated the roles of two different neuropeptides, Drosophila tachykinin (DTK) and short neuropeptide F (sNPF), in aspects of locomotor behavior. In the Drosophila brain, DTK and sNPF are expressed in interneurons innervating the central complex. We have directed RNA interference (RNAi) towards DTK and sNPF specifically in different central complex neurons. We also expressed a temperature-sensitive dominant negative allele of the fly ortholog of dynamin called shibire^ts1, essential in membrane vesicle recycling and endocytosis, to disrupt synaptic transmission in central complex neurons. The spontaneous walking activity of the RNAi- or shibire^ts1-expressing flies was quantified by video tracking. DTK-deficient flies displayed drastically increased center zone avoidance, suggesting that DTK is involved in the regulation of spatial orientation. In addition, DTK deficiency in other central complex neurons resulted in flies with an increased number of activity–rest bouts. Perturbations in the sNPF circuit indicated that this peptide is involved in the fine regulation of locomotor activity levels. Our findings suggest that the contribution of DTK and sNPF to locomotor behavior is circuit dependent and associated with particular neuronal substrates. Thus, peptidergic pathways in the central complex have specific roles in the fine tuning of locomotor activity of adult Drosophila.

Journal of Experimental Biology 213, 2256-2265 (2010)
http://jeb.biologists.org/cgi/content/abstract/213/13/2256

 

 

Insect Neuroscience

Stratification and synaptogenesis in the mushroom body of the honeybee, Apis mellifera

 

Olga Ganeshina ^*olgaganesh@gmail.com

Institute for Neurobiology, Free University of Berlin, 14195 Berlin, Germany

 

Stratification is a basic anatomical feature of central brain in both vertebrates and many invertebrates. The aim of this study was to investigate the relationship between stratification and synaptogenesis in the developing mushroom bodies of the honeybee. During metamorphosis, the vertical lobe of mushroom body shows progressive stratification with three thick primary strata and more secondary strata and laminae. Three primary strata are formed at the metamorphic stage P1, before the youngest generation of the mushroom body intrinsic neurons, Kenyon cells, is produced. Thus, the primary strata within the lobe are unlikely to represent three major subpopulations of the Kenyon cells sequentially produced in the mushroom bodies. Formation of laminae starts at the stage P2 and culminates at the end of metamorphosis. The laminae appear within the lobe rather than being added sequentially from the ingrowth stratum. Alternating dark and light lamina (lamina doublets) are formed in the vertical lobe in late metamorphosis (stages P6-P9), but they are not visible in adults. The pattern of stratification is not continuous along the vertical lobe at the same developmental stage, and resorting of axons of the Kenyon cells is likely to occur within dark laminae. In the developing vertical lobe, dark laminae show lower synaptic density and exhibit an ultra structure that is indicative for a delay in synaptogenesis relative to the primary strata. A local transient block of synaptogenesis within the dark laminae may provide correct targeting of Kenyon cells by extrinsic mushroom body neurons.

Journal of Morphology 2010 Volume 271 Issue 7, Pages 826 - 844

http://www3.interscience.wiley.com/journal/123325763/abstract

 

Two-photon calcium imaging from head-fixed Drosophila during optomotor walking behavior

 

Johannes D Seelig^1,2, M Eugenia Chiappe^1,2, Gus K Lott^1,2, Anirban Dutta¹, Jason E Osborne¹, Michael B Reiser¹ & Vivek Jayaraman¹ vivek@janelia.hhmi.org

Janelia Farm Research Campus, Howard Hughes Medical Institute, Ashburn, Virginaia, USA

 

Drosophila melanogaster is a model organism rich in genetic tools to manipulate and identify neural circuits involved in specific behaviors. Here we present a technique for two-photon calcium imaging in the central brain of head-fixed Drosophila walking on an air-supported ball. The ball's motion is tracked at high resolution and can be treated as a proxy for the fly's own movements. We used the genetically encoded calcium sensor, GCaMP3.0, to record from important elements of the motion-processing pathway, the horizontal-system lobula plate tangential cells (LPTCs) in the fly optic lobe. We presented motion stimuli to the tethered fly and found that calcium transients in horizontal-system neurons correlated with robust optomotor behavior during walking. Our technique allows both behavior and physiology in identified neurons to be monitored in a genetic model organism with an extensive repertoire of walking behaviors.

Nature Methods 7, 535 - 540 (2010) 

http://www.nature.com/nmeth/journal/v7/n7/abs/nmeth.1468.html?lang=en

 

Insect Olfaction

Arrangement of Output Information from the 3 Macroglomerular Units in the Heliothine Moth Helicoverpa assulta: Morphological and Physiological Features of Male-Specific Projection Neurons

 

Xin-Cheng Zhao and Bente G. Berg bente.berg@ntnu.no

Department of Psychology and Neuroscience Unit, Medical Technical Research Center (MTFS), Norwegian University of Science and Technology, Olav Kyrres gate 9, N-7489 Trondheim, Norway

 

Helicoverpa assulta is exceptional among heliothine species studied so far as concerns composition of the pheromone blend. Previous reports have accordingly pointed out distinct characteristics in the male-specific olfactory pathway of this species, peripherally by an unusual distribution of 2 sensillum categories and centrally by a particular anatomical arrangement of the male-specific glomeruli constituting the macroglomerular complex (MGC). In order to determine the physiological tuning of the 3 MGC units in this species, we have characterized male-specific antennal-lobe projection neurons morphologically and physiologically by use of the intracellular recording and staining technique combined with confocal microscopy. The results show 2 projection neuron types of equal numbers, one that responds to the primary pheromone component, cis-9-hexadecenal, and arborizes in the cumulus and one that responds to the interspecific signal, cis-9-tetradecenal, and arborizes in the dorsomedial unit. A third type responded to the secondary pheromone component, cis-11-hexadecenal, and innervated the smaller ventral unit. The results complement previous findings from tracing of physiologically identified receptor neurons and determine for the first time the functional specificity of each glomerulus in the MGC of H. assulta. The results are particularly interesting because heliothine moths are attractive objects for comparative studies addressing questions concerning divergence of male-specific olfactory characteristics related to speciation.

Chemical Senses 2010 35(6):511-521

http://chemse.oxfordjournals.org/cgi/content/abstract/35/6/511

 

Insect Photoreception

An expanded set of photoreceptors in the Eastern Pale Clouded Yellow butterfly, Colias erate

 

Primo? Pirih^{1, 2}  , Kentaro Arikawa³ and Doekele G. Stavenga¹ p.pirih@rug.nl

Department of Neurobiophysics, University of Groningen, Groningen, The Netherlands

Department of Artificial Intelligence, University of Groningen, Groningen, The Netherlands

Laboratory of Neuroethology, Hayama Center for Advanced Studies, Sokendai (The Graduate University for Advanced Studies), Hayama, Kanagawa, Japan

 

We studied the spectral and polarisation sensitivities of photoreceptors of the butterfly Colias erate by using intracellular electrophysiological recordings and stimulation with light pulses. We developed a method of response waveform comparison (RWC) for evaluating the effective intensity of the light pulses. We identified one UV, four violet-blue, two green and two red photoreceptor classes. We estimated the peak wavelengths of four rhodopsins to be at about 360, 420, 460 and 560 nm. The four violet-blue classes are presumably based on combinations of two rhodopsins and a violet-absorbing screening pigment. The green classes have reduced sensitivity in the ultraviolet range. The two red classes have primary peaks at about 650 and 665 nm, respectively, and secondary peaks at about 480 nm. The shift of the main peak, so far the largest amongst insects, is presumably achieved by tuning the effective thickness of the red perirhabdomal screening pigment. Polarisation sensitivity of green and red photoreceptors is higher at the secondary than at the main peak. We found a 20-fold variation of sensitivity within the cells of one green class, implying possible photoreceptor subfunctionalisation. We propose an allocation scheme of the receptor classes into the three ventral ommatidial types.

Journal of Comparative Physiology A: Neuroethology, Sensory, Neural, and Behavioral Physiology Volume 196, Number 7 / July, 2010 501-517

http://www.springerlink.com/content/9275174338564466/

 

Insect Sensory Physiology

Auditory sensitivity and ecological relevance: the functional audiogram as modelled by the bat detecting moth ear

 

Matthew E. Jackson¹  , Navdeep S. Asi¹ and James H. Fullard¹ matt.e.jackson@gmail.com

Department of Biology, University of Toronto Mississauga, 3359 Mississauga Rd., Mississauga, ON, L5L 1C6, Canada

  

Auditory sensitivity has often been measured by identifying neural threshold in real-time (online) which can introduce bias in the audiograms that are produced. We tested this by recording auditory nerve activity of the notodontid moth Nadata gibbosa elicited by bat-like ultrasound and analysing the response offline. We compared this audiogram with a published online audiogram showing that the bias introduced can result in a difference in the audiogram shape. In the second part of our study we compared offline audiograms using spike number as threshold with others that used spike period and stimulus/spike latency, variables that have been suggested as providing behaviourally functional criteria. These comparisons reveal that functional audiograms are more flatly tuned than simple spike audiograms. The shapes of behavioural audiograms are discussed in the context of the selection pressure that maintains their shape, bat predation. Finally, we make predictions on the distance from bats at which notodontid moths use negative phonotaxis or the acoustic startle response.

Journal of Comparative Physiology A: Neuroethology, Sensory, Neural, and Behavioral Physiology Volume 196, Number 7 / July, 2010 453-462

http://www.springerlink.com/content/h83575u270142v21/

 

 

Insect Society

Ergatoid queen development in the ant Myrmecina nipponica: modular and heterochronic regulation of caste differentiation

 

Satoshi Miyazaki1,2,5, Takahiro Murakami3, Takuya Kubo1, Noriko Azuma4, Seigo Higashi1 and Toru Miura1,* miu@ees.hokudai.ac.jp

¹Graduate School of Environmental Science, Hokkaido University, Sapporo 060-0810, Japan

²Graduate School of Veterinary Medicine, Hokkaido University, Sapporo 060-0818, Japan

³Biological Laboratory, Hokkaido University of Education, Hakodate 040-8567, Japan

⁴Support Office for Female Researchers, Hokkaido University, Sapporo 060-0808, Japan

⁵Japan Society for the Promotion of Science Research Fellow, Tokyo 102-8471, Japan

 

Caste polyphenism in social insects provides us with excellent opportunities to examine the plasticity and robustness underlying developmental pathways. Several ant species have evolved unusual castes showing intermediate morphologies between alate queens and wingless workers. In some low-temperature habitats, the ant Myrmecina nipponica produces such intermediate reproductives (i.e. ergatoids), which can mate and store sperm but cannot fly. To gain insight into the developmental and evolutionary aspects associated with ergatoid production, we conducted morphological and histological examinations of the post-embryonic development of compound eyes, gonads and wings during the process of caste differentiation. In compound eyes, both the queen-worker and ergatoid-worker differences were already recognized at the third larval instar. In gonads, queen-worker differentiation began at the larval stage, and ergatoid-worker differentiation began between the prepupal and pupal stages. Wing development in ergatoids was generally similar to that in workers throughout post-embryonic development. Our results showed that the developmental rate and timing of differentiation in body parts differed among castes and among body parts. These differences suggest that the rearrangement of modular body parts by heterochronic developmental regulation is responsible for the origination of novel castes, which are considered to be adaptations to specific ecological niches.

Proc. R. Soc. B 7 July 2010 vol. 277 no. 1690 1953-1961

http://rspb.royalsocietypublishing.org/content/277/1690/1953.abstract

 

Selfish strategies and honest signalling: reproductive conflicts in ant queen associations

 

Luke Holman*†, Stephanie Dreier† and Patrizia d'Ettorre lholman@bio.ku.dk

Department of Biology, Centre for Social Evolution, University of Copenhagen, Universitetsparken 15, 2100 Copenhagen, Denmark

 

Social insects offer unique opportunities to test predictions regarding the evolution of cooperation, life histories and communication. Colony founding by groups of unrelated queens, some of which are later killed, may select for selfish reproductive strategies, honest signalling and punishment. Here, we use a brood transfer experiment to test whether cofounding queens of the ant Lasius niger ‘selfishly’ adjust their productivity when sharing the nest with future competitors. We simultaneously analysed queen cuticular hydrocarbon (CHC) profiles to investigate whether queens honestly signal their reproductive output or produce dishonest, manipulative signals, providing a novel test of the evolutionary significance of queen pheromones. Queens produced fewer workers when their colony contained ample brood, but only in the presence of competitors, suggesting selfish conservation of resources. Several CHCs correlated with reproductive maturation, and to a lesser extent with productivity; the same hydrocarbons were more abundant on queens that were not killed, suggesting that workers select productive queens using these chemical cues. Our results highlight the role of honest signalling in the evolution of cooperation: whenever cheaters can be reliably identified, they may incur sanctions that reduce the incentive to be selfish.

Proc. R. Soc. B 7 July 2010 vol. 277 no. 1690 2007-2015

http://rspb.royalsocietypublishing.org/content/277/1690/2007.abstract

 

 

Brain transcriptomic analysis in paper wasps identifies genes associated with behaviour across social insect lineages

 

Amy L. Toth1,2,7,*†, Kranthi Varala4, Michael T. Henshaw6, Sandra L. Rodriguez-Zas3, Matthew E. Hudson1,4 and Gene E. Robinson1,2,5 amytoth@iastate.edu

¹Institute for Genomic Biology, University of Illinois, Urbana-Champaign, IL, USA

²Department of Entomology, University of Illinois, Urbana-Champaign, IL, USA

3Department of Animal Biology, University of Illinois, Urbana-Champaign, IL, USA

4Department of Crop Sciences, University of Illinois, Urbana-Champaign, IL, USA

⁵Neuroscience Program, University of Illinois, Urbana-Champaign, IL, USA

⁶Department of Biology, Grand Valley State University, Allendale, MI, USA

⁷Department of Entomology, Pennsylvania State University, University Park, PA, USA

 

Comparative sociogenomics has the potential to provide important insights into how social behaviour evolved. We examined brain gene expression profiles of the primitively eusocial wasp Polistes metricus and compared the results with a growing base of brain gene expression information for the advanced eusocial honeybee, Apis mellifera. We studied four female wasp groups that show variation in foraging/provisioning behaviour and reproductive status, using our newly developed microarray representing approximately 3248 P. metricus genes based on sequences generated from high-throughput pyrosequencing. We found differences in the expression of approximately 389 genes across the four groups. Pathways known from Drosophila melanogaster to be related to lipid metabolism, heat and stress response, and various forms of solitary behaviour were associated with behavioural differences among wasps. Forty-five per cent of differentially expressed transcripts showed significant associations with foraging/provisioning status, and 14 per cent with reproductive status. By comparing these two gene lists with lists of genes previously shown to be differentially expressed in association with honeybee division of labour, we found a significant overlap of genes associated with foraging/provisioning, but not reproduction, across the two species. These results suggest common molecular roots for foraging division of labour in two independently evolved social insect species and the possibility of more lineage-specific roots of reproductive behaviour. We explore the implications of these findings for the idea that there is a conserved ‘genetic toolkit’ for division of labour across multiple lineages.

Proc. R. Soc. B 22 July 2010 vol. 277 no. 1691 2139-2148

http://rspb.royalsocietypublishing.org/content/277/1691/2139.abstract

 

 

Socially induced brain development in a facultatively eusocial sweat bee Megalopta genalis (Halictidae)

 

Adam R. Smith1,2,*, Marc A. Seid1,2, Lissette C. Jiménez1,2 and William T. Wcislo1,2,* arsmith2@gmail.com; wcislow@si.edu

¹Smithsonian Tropical Research Institute, Apartado 0843-03092, Balboa, Republic of Panama

²MRC 0580-12, Unit 9100, Box 0948, DPO AA 34002-9998, USA

 

Changes in the relative size of brain regions are often dependent on experience and environmental stimulation, which includes an animal's social environment. Some studies suggest that social interactions are cognitively demanding, and have examined predictions that the evolution of sociality led to the evolution of larger brains. Previous studies have compared species with different social organizations or different groups within obligately social species. Here, we report the first intraspecific study to examine how social experience shapes brain volume using a species with facultatively eusocial or solitary behaviour, the sweat bee Megalopta genalis. Serial histological sections were used to reconstruct and measure the volume of brain areas of bees behaving as social reproductives, social workers, solitary reproductives or 1-day-old bees that are undifferentiated with respect to the social phenotype. Social reproductives showed increased development of the mushroom body (an area of the insect brain associated with sensory integration and learning) relative to social workers and solitary reproductives. The gross neuroanatomy of young bees is developmentally similar to the advanced eusocial species previously studied, despite vast differences in colony size and social organization. Our results suggest that the transition from solitary to social behaviour is associated with modified brain development, and that maintaining dominance, rather than sociality per se, leads to increased mushroom body development, even in the smallest social groups possible (i.e. groups with two bees). Such results suggest that capabilities to navigate the complexities of social life may be a factor shaping brain evolution in some social insects, as for some vertebrates.

Proc. R. Soc. B 22 July 2010 vol. 277 no. 1691 2157-2163

http://rspb.royalsocietypublishing.org/content/277/1691/2157.abstract

 

 

Insect Review

Atmospheric oxygen level and the evolution of insect body size

 

Jon F. Harrison1,*, Alexander Kaiser2 and John M. VandenBrooks1 j.harrison@asu.edu

¹School of Life Sciences, Arizona State University, Tempe, AZ 85287-4501, USA

²Department of Biochemistry, Midwestern University, Glendale, AZ 85308, USA

 

Insects are small relative to vertebrates, possibly owing to limitations or costs associated with their blind-ended tracheal respiratory system. The giant insects of the late Palaeozoic occurred when atmospheric PO₂ (aPO₂) was hyperoxic, supporting a role for oxygen in the evolution of insect body size. The paucity of the insect fossil record and the complex interactions between atmospheric oxygen level, organisms and their communities makes it impossible to definitively accept or reject the historical oxygen-size link, and multiple alternative hypotheses exist. However, a variety of recent empirical findings support a link between oxygen and insect size, including: (i) most insects develop smaller body sizes in hypoxia, and some develop and evolve larger sizes in hyperoxia; (ii) insects developmentally and evolutionarily reduce their proportional investment in the tracheal system when living in higher aPO₂, suggesting that there are significant costs associated with tracheal system structure and function; and (iii) larger insects invest more of their body in the tracheal system, potentially leading to greater effects of aPO₂ on larger insects. Together, these provide a wealth of plausible mechanisms by which tracheal oxygen delivery may be centrally involved in setting the relatively small size of insects and for hyperoxia-enabled Palaeozoic gigantism.

Proc. R. Soc. B 7 July 2010 vol. 277 no. 1690 1937-1946

http://rspb.royalsocietypublishing.org/content/277/1690/1937.abstract

 

Evolving olfactory systems on the fly

 

Pavan Ramdya^1, 2 and Richard Benton^1,  

¹ Center for Integrative Genomics, Faculty of Biology and Medicine, University of Lausanne, CH-1015 Lausanne, Switzerland
² Laboratory of Intelligent Systems, School of Engineering, Ecole Polytechnique Fédérale de Lausanne, Station 11, CH-1015 Lausanne, Switzerland

 

The detection of odour stimuli in the environment is universally important for primal behaviours such as feeding, mating, kin interactions and escape responses. Given the ubiquity of many airborne chemical signals and the similar organisation of animal olfactory circuits, a fundamental question in our understanding of the sense of smell is how species-specific behavioural responses to odorants can evolve. Recent comparative genomic, developmental and physiological studies are shedding light on this problem by providing insights into the genetic mechanisms that underlie anatomical and functional evolution of the olfactory system. Here we synthesise these data, with a particular focus on insect olfaction, to address how new olfactory receptors and circuits might arise and diverge, offering glimpses into how odour-evoked behaviours could adapt to an ever-changing chemosensory world.

Trends in Genetics, Volume 26, Issue 7, 307-316, 27 May 2010

http://www.cell.com/trends/genetics/abstract/S0168-9525(10)00085-5

 

  

 

 

Edited by Xin-Cheng Zhao

2010-07-05

 

 

Insect Frontiers, June 2010 Volume 2 Number 6 （PDF final）http://www.sciencenet.cn/m/user_content.aspx?id=335254 2010年7月07日更新 （附PDF final）

Insect Frontiers 2010 Vol2No7 cover PDF

 

Insect Frontiers 2010 Vol2No7 DOC Final

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