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Insect Frontiers, April 2010 Volume 2 Number 4
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Insect Behaviour
Elaborate courtship enhances sperm transfer in the Hawaiian swordtail cricket, Laupala cerasina
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References and further reading may be available for this article. To view references and further reading you must purchase this article.
a Department of Biology, University of Maryland, U.S.A.
Males of many insect species engage in ritualized behaviours during courtship that include the donation of a food gift to their partner. Although there is extensive diversity in nuptial gift form, a gift provided before mating typically serves to facilitate copulation, thereby increasing a male's mating success. Unlike other insects, the Hawaiian swordtail cricket Laupala shows protracted courtship that includes the serial donation of nuptial gifts prior to mating. Males transfer multiple spermless ‘micro’ spermatophores over several hours before the transfer of a single sperm containing a ‘macro’ spermatophore. By experimental manipulation of male courtship, we tested several hypotheses pertaining to the adaptive significance of protracted courtship involving nuptial gift donation in this system. We found that extensive courtship interactions improve insemination by causing the female reproductive tract to take in more sperm. This suggests that the enhancement of sperm transfer is due to the serial donation of microspermatophores, which would represent a relatively novel function for nuptial gifts provided before mating and highlights the importance of examining cryptic processes of sexual selection.
Displacement activities during the honeybee transition from waggle dance to foraging
References and further reading may be available for this article. To view references and further reading you must purchase this article.
References and further reading may be available for this article. To view references and further reading you must purchase this article.
a Department of Ecology and Evolutionary Biology, Princeton University, Princeton, NJ, U.S.A.
Displacement activities, which are typically locomotory, grooming and object-manipulation behaviours, have been shown to reduce stress. However, their function within the motivational system remains unclear. I tested the hypothesis that displacement activities have a functional role during transitions between motivational states, using the honeybee model system. I observed a number of locomotory and grooming behaviours performed when foraging honeybees returned to the hive to dance. These focal behaviours occurred significantly more frequently during the period of transition from waggle dancing to exiting the hive to forage than during the periods before the waggle dance or during the waggle dance. By contrast, the control behaviour, trophallaxis, was distributed across time periods significantly differently, occurring with equal frequency in all periods. These results are consistent with the hypothesis that displacement activities have a functional role during motivational transitions. Evidence from other species suggests that the most likely function is facilitation, rather than inhibition, of the transition. The wide range of species in which displacement activities have been identified suggests that they are a universal feature of motivational control.
Dynamics of optomotor responses in Drosophila to perturbations in optic flow
Jamie C. Theobald1,*, Dario L. Ringach2,3 and Mark A. Frye1,2 jamiet@ucla.edu
1 Howard Hughes Medical Institute, The Department of Integrative Biology and Physiology, University of California, Los Angeles, 621 Charles Young Dr. South, Los Angeles, CA 90095-1606, USA
2 Department of Neurobiology, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA 90095-1563, USA
3 Department of Psychology, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA 90095-1563, USA
2 Department of Neurobiology, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA 90095-1563, USA
3 Department of Psychology, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA 90095-1563, USA
For a small flying insect, correcting unplanned course perturbationsis essential for navigating through the world. Visual coursecontrol relies on estimating optic flow patterns which, in flies,are encoded by interneurons of the third optic ganglion. However,the rules that translate optic flow into flight motor commandsremain poorly understood. Here, we measured the temporal dynamicsof optomotor responses in tethered flies to optic flow fieldsabout three cardinal axes. For each condition, we used whitenoise analysis to determine the optimal linear filters linkingoptic flow to the sum and difference of left and right wingbeat amplitudes. The estimated filters indicate that flies reactvery quickly to perturbations of the motion field, with puredelays in the order of ~20 ms and time-to-peak of ~100 ms. Byconvolution the filters also predict responses to arbitrarystimulus sequences, accounting for over half the variance in5 of our 6 stimulus types, demonstrating the approximate linearityof the system with respect to optic flow variables. In the remainingcase of yaw optic flow we improved predictability by measuringindividual flies, which also allowed us to analyze the variabilityof optomotor responses within a population. Finally, the linearfilters at least partly explain the optomotor responses to superimposedand decomposed compound flow fields.
Journal of Experimental Biology 213, 1366-1375 (2010)
http://jeb.biologists.org/cgi/content/abstract/213/8/1366
http://jeb.biologists.org/cgi/content/abstract/213/8/1366
Visual gaze control during peering flight manoeuvres in honeybees
As animals travel through the environment, powerful reflexes help stabilize their gaze by actively maintaining head and eyes in a level orientation. Gaze stabilization reduces motion blur and prevents image rotations. It also assists in depth perception based on translational optic flow. Here we describe side-to-side flight manoeuvres in honeybees and investigate how the bees’ gaze is stabilized against rotations during these movements. We used high-speed video equipment to record flight paths and head movements in honeybees visiting a feeder. We show that during their approach, bees generate lateral movements with a median amplitude of about 20 mm. These movements occur with a frequency of up to 7 Hz and are generated by periodic roll movements of the thorax with amplitudes of up to ±60°. During such thorax roll oscillations, the head is held close to horizontal, thereby minimizing rotational optic flow. By having bees fly through an oscillating, patterned drum, we show that head stabilization is based mainly on visual motion cues. Bees exposed to a continuously rotating drum, however, hold their head fixed at an oblique angle. This result shows that although gaze stabilization is driven by visual motion cues, it is limited by other mechanisms, such as the dorsal light response or gravity reception.
Proc. R. Soc. B 22 April 2010 vol. 277 no. 1685 1209-1217
Optic flow informs distance but not profitability for honeybees
How do flying insects monitor foraging efficiency? Honeybees (Apis mellifera) use optic flow information as an odometer to estimate distance travelled, but here we tested whether optic flow informs estimation of foraging costs also. Bees were trained to feeders in flight tunnels such that bees experienced the greatest optic flow en route to the feeder closest to the hive. Analyses of dance communication showed that, as expected, bees indicated the close feeder as being further, but they also indicated this feeder as the more profitable, and preferentially visited this feeder when given a choice. We show that honeybee estimates of foraging cost are not reliant on optic flow information. Rather, bees can assess distance and profitability independently and signal these aspects as separate elements of their dances. The optic flow signal is sensitive to the nature of the environment travelled by the bee, and is therefore not a good index of flight energetic costs, but it provides a good indication of distance travelled for purpose of navigation and communication, as long as the dancer and recruit travel similar routes. This study suggests an adaptive dual processing system in honeybees for communicating and navigating distance flown and for evaluating its energetic costs.
Proc. R. Soc. B 22 April 2010 vol. 277 no. 1685 1241-1245
Distributed leadership and adaptive decision-making in the ant Tetramorium caespitum
In the ant species Tetramorium caespitum, communication and foraging patterns rely on group-mass recruitment. Scouts having discovered food recruit nestmates and behave as leaders by guiding groups of recruits to the food location. After a while, a mass recruitment takes place in which foragers follow a chemical trail. Since group recruitment is crucial to the whole foraging process, we investigated whether food characteristics induce a tuning of recruiting stimuli by leaders that act upon the dynamics and size of recruited groups. High sucrose concentration triggers the exit of a higher number of groups that contain twice as many ants and reach the food source twice as fast than towards a weakly concentrated one. Similar trends were found depending on food accessibility: for a cut mealworm, accessibility to haemolymph results in a faster formation of larger groups than for an entire mealworm. These data provide the background for developing a stochastic model accounting for exploitation patterns by group-mass recruiting species. This model demonstrates how the modulations performed by leaders drive the colony to select the most profitable food source among several ones. Our results highlight how a minority of individuals can influence collective decisions in societies based on a distributed leadership.
Proc. R. Soc. B 22 April 2010 vol. 277 no. 1685 1267-1273
Insect Behavioral Ecology
Does water velocity influence optimal escape behaviors in stream insects?
Trent M. Hoovera,b and John S. Richardsona trent.hoover@gmail.com
a Department of Forest Sciences, 3041-2424 Main Mall, University of British Columbia, Vancouver, British Columbia, Canada V6T 1Z4 b Department of Civil Engineering, 2324 Main Mall, University of British Columbia, Vancouver, British Columbia, Canada V6T 1Z4
Optimal escape theory can successfully explain variation inthe distance to an approaching predator at which prey initiateflight (the flight initiation distance, FID). However, for animalswithout access to refuges, optimal escape theory may also explainvariation in the distance that prey flee (the retreat distance,RD). In benthic stream habitats, both the risk of predationand the costs of escape may be mediated by water velocity; optimalescape theory then predicts that FID and RD of slow-currentinsects should vary little with increasing current velocity,whereas the FID and RD of fast-current insects should decrease.To test this prediction, a simulated predator (SP) was usedto initiate escape responses in 3 mayflies found in differenthabitats—Ameletus (slow pools), Baetis (fast riffles),and Epeorus (very fast cascades)—across a range of watervelocities. Unexpectedly, the FID of all 3 prey did not varywith water velocity. In contrast, the RD of Epeorus decreasedwith velocity (RD at the lowest velocity about 4.5x greaterthan the highest velocity), whereas the RD of Ameletus did notvary significantly with velocity. Escape behaviors of Baetisdid not vary strongly with velocity. Variation in the proportionof larvae that escaped by drifting or swimming rather than crawling(Ameletus > Baetis, Epeorus) suggests that for fast-currentprey, the costs associated with leaving the streambed exceedthe risks of benthic predation. Water velocity may thus influenceecological processes such as predator–prey interactionsand emigration from patches in substantial, but previously unexplored,ways.
Behavioral Ecology 2010 21(2):242-249;
Dear enemy phenomenon in the leaf-cutting ant Acromyrmex lobicornis: behavioral and genetic evidence
Romina D. Dimarcoa,b, Alejandro G. Farji-Brenera and Andrea C. Premolia rdimarco@utk.edu
a Universidad Nacional del Comahue, Laboratorio Ecotono-Centro Regional Universitario Bariloche, Quintral 1250, 8400, Bariloche, Argentina b Department of Ecology and Evolutionary Biology, University of Tennessee, 569 Dabney Hall, Knoxville, TN 37996, USA
The defense of territory through aggressive behavior is wellknown in animals. However, some territorial animal species respondless aggressively to intrusions by their neighbors than to intrusionsby nonneighbors to minimize the costs of continuous fights,a phenomenon termed the dear enemy phenomenon (DEP). Althoughseveral studies show the existence of this phenomenon, littleis known about the mechanism behind it. One possible explanationis the lower degree of genetic divergence between neighborscompared with nonneighbors. We tested the DEP hypothesis andwhether genetic divergence among nests might drive the DEP inthe leaf-cutting ant Acromyrmex lobicornis in Patagonia, Argentina,through behavioral and genetic studies. Individuals from nearbycolonies interacted less aggressively than individuals fromdistant colonies. However, levels of genetic divergence betweenfocal–close and between focal–nonneighbor nestsattained similar values. Our results support the dear enemyhypothesis but suggest that the differential aggressivenesstoward neighbors relative to nonneighbors is unrelated to geneticdivergence among nests. Other possible causes of this behavior,such as habituation, are discussed.
Behavioral Ecology 2010 21(2):304-310
The structure of foraging activity in colonies of the harvester ant, Pogonomyrmex occidentalis
Blaine J. Colea, Adrian A. Smithb, Zachary J. Huberc and Diane C. Wiernasza bcole@uh.edu
a Department of Biology and Biochemistry, University of Houston, Houston, TX 77204-5001, USA b School of Life Sciences, Arizona State University, Tempe, AZ 85287, USA c Department of Entomology, University of Minnesota, Minneapolis, MN 55108, USA
The timing of activity by desert dwelling poikilotherms canbe critical to survival. In the western harvester ant, coloniesthat have higher levels of genetic diversity forage for longertime periods in the morning than colonies with less diversity.We determined whether the advantage of early foraging colonieswas consistent by examining foraging behavior at other timesof day and year. We used a combination of activity monitoringand temperature measurement at the nest entrance to quantifyforaging activity during the morning and evening summer foragingperiods in both June and August. The duration of morning andevening foraging was significantly positively correlated bothwithin and across seasons—some colonies have a consistentadvantage in foraging. The temperature range over which coloniesforaged was also consistent across time, suggesting that intercolonydifferences are a consequence of variation in the thermal ranges/preferencesof the colony's workers. The duration of foraging during thisstudy was correlated with the duration of foraging measured6 years earlier, suggesting that it is an aspect of colony phenotype.
Behavioral Ecology 2010 21(2):337-342;
Desert ants use foraging distance to adapt the nest search to the uncertainty of the path integrator
Tobias Merklea,b and Rüdiger Wehnerc,d tobias.merkle@anu.edu.au
a Centre for Visual Sciences, Research School of Biology, The Australian National University, Canberra, ACT 0200, Australia b Theoretical Biology, University of Bonn, 53115 Bonn, Germany c Brain Research Institute, University of Zurich, 8057 Zurich, Switzerland d Biocenter (Zoology II), University of Würzburg, 97074 Würzburg, Germany
Path integration enables desert ants to return to their neston a direct path. However, the mechanism of path integrationis error prone and the ants often miss the exact position ofthe nest entrance in which case they engage in systematic searchbehavior. The pattern produced by this search behavior is veryflexible and enables the ants to take the errors into accountthat have been accumulated during foraging and homing. Here,we assess which parameter the desert ant Cataglyphis fortisuses to adapt its systematic search behavior to the uncertaintyof its path integrator when deprived of additional externalcues. We compared groups of ants that had covered the same distancebetween their nest and a food source but differed in the overalllength of their foraging excursions. Our results show that thewidth of the ants’ search density profile depends on thedistance the ants have ventured out from the nest, that is,the length of the home vector, but not on the tortuousness oftheir outbound path, that is, the number of steps made duringforaging. This distance value is readily available through thepath integrator and obviously sufficient to calibrate the ants’systematic search patterns.
Behavioral Ecology 2010 21(2):349-355
Know thine enemy: why some weaver ants do but others do not
Philip S. Neweya, Simon K.A. Robsonb and Ross H. Crozierb philip.newey@unil.ch
a School of Marine and Tropical Biology, James Cook University, Cairns 4878, Australia b School of Marine and Tropical Biology, James Cook University, Townsville 4811, Australia
Recognition systems involve 3 components: an expression component,a perception component, and an action or response component.Disentangling the perception component from the action componentcan be difficult, as the absence of a discriminatory responsemay result from either a difference in perception or action.Social insects generally defend their colony against intrudingconspecifics and provide a useful model for exploring recognitionsystems. However, whether differences in behavior at the colonyor individual level result from the perception or action componentof the recognition system is largely unknown. Furthermore, variationat the individual level has remained largely unexplored becauseresearch on social insects often focuses on the colony ratherthan on the individual. Using some novel behavioral bioassays,we here show that variation in the aggressive behavior of individualweaver ants (Oecophylla smaragdina L.) arises more from theidentity of the recipient than of the intruder and, contraryto previous findings, that this often results from perceptualdifferences. We suggest that recognition in weaver ants mayinvolve a template based on the individual’s odor priorto intermingling with other odors rather than on a common odor.We also argue that a common odor might be more important forthe survival of the colony than a shared template. Conversely,possessing a range of templates may provide a colony with additionalfitness benefits. By focusing on the differences among individualworkers within colonies, this study reveals complexities innest mate recognition that might otherwise have gone unnoticed.
Behavioral Ecology 2010 21(2):381-386
Mate choice in the dung beetle Onthophagus sagittarius: are female horns ornaments?
Nicola L. Watson and Leigh W. Simmons nicola.watson@grs.uwa.edu.au
Centre for Evolutionary Biology, School of Animal Biology (M092), The University of Western Australia, 35 Stirling Highway, Crawley 6009, WA, Australia
Sexual selection typically operates via male contest competitionand female choice, favoring the evolution of secondary sexualtraits in males. However, there are numerous taxa in which femalespossess secondary sexual traits and the selective pressuresoperating on female ornamentation are not well understood. Weexamined sexual selection operating via mate choice in the dungbeetle Onthophagus sagittarius, a species exhibiting sex-specificornamentation. Precopulatory mate preferences and their subsequenteffects on breeding success were examined. Female preferencesfavored large males and when paired with small males, maleswith high courtship rates. Large females were choosier thansmall females. No overt male preferences for female size orornamentation were found; thus, we conclude that female hornsin this species are unlikely to have evolved as ornaments viaprecopulatory male mate choice. Relative horn length in femalesdetermined brood ball productivity, whereas female body sizeand an interaction between male courtship rate and male bodysize determined brood ball weight. Our results provide evidencefor female but not male mate choice. They suggest that attractivemales increase reproductive performance, but it is unclear whetherthe effect of male phenotype is mediated via differences inpaternal investment or female differential allocation towardattractive males.
Behavioral Ecology 2010 21(2):424-430
Insect Behavioural Physiology
Age-dependent cyclic locomotor activity in the cricket, Gryllus bimaculatus, and the effect of adipokinetic hormone on locomotion and excitability
Katharina Faßold1, 3, Hassan I. H. El-Damanhouri1 and Matthias W. Lorenz1, 2 matthias.lorenz@uni-bayreuth.de
(1) Department of Animal Ecology I, University of Bayreuth, 95440 Bayreuth, Germany
(2) Present address: Department of Animal Physiology, University of Bayreuth, 95440 Bayreuth, Germany
(3) Present address: Jean-Paul-Gymnasium Hof, Gymnasiumsplatz 4-6, 95028 Hof, Germany
Excitability and locomotor activity of male and female last instar larvae and adults of the two-spotted cricket are measured under crowded conditions, allowing the animals to interact with conspecifics during observations. Male and female last instar larvae display age-dependent cyclic patterns of activity with maxima during early to mid scotophase and minima during early photophase. A period of low locomotor activity without time of day-dependent cyclic changes starts 1 day before the final moult and lasts until 1 day after the moult. Then, both excitability and locomotor activity increase and become cyclic again within 2 or 3 days. The cyclic changes gradually dampen in adult females older than 6 days and finally cease. When injected into photophase larvae and adults, adipokinetic hormone (AKH) increases excitability and locomotor activity in a dose-dependent manner, whereas it has no such effect when injected into scotophase animals. Other behaviours (jumping, hind wing trembling) that mostly occur in scotophase crickets are also increased by injecting AKH into photophase crickets. We argue that AKH could be responsible for linking the endogenous clock output with the cyclic changes in locomotor activity. Furthermore, AKH may serve to synchronise metabolism and behaviour to optimise larval development and reproduction.
Journal of Comparative Physiology A: Neuroethology, Sensory, Neural, and Behavioral PhysiologyVolume 196, Number 4 / April, 2010 271-283
Honeybees change their height to restore their optic flow
Geoffrey Portelli1 , Franck Ruffier1 and Nicolas Franceschini1
Biorobotics Department, Institute of Movement Sciences, CNRS-University of Aix-Marseille II, CP938, 163 Avenue de Luminy, 13288 Marseille, Cedex 9, France
To further elucidate the mechanisms underlying insects’ height and speed control, we trained outdoor honeybees to fly along a high-roofed tunnel, part of which was equipped with a moving floor. Honeybees followed the stationary part of the floor at a given height. On encountering the moving part of the floor, which moved in the same direction as their flight, honeybees descended and flew at a lower height, thus gradually restoring their ventral optic flow (OF) to a similar value to that they had percieved when flying over the stationary part of the floor. This was therefore achieved not by increasing their airspeed, but by lowering their height of flight. These results can be accounted for by a control system called an optic flow regulator, as proposed in previous studies. This visuo-motor control scheme explains how honeybees can navigate safely along tunnels on the sole basis of OF measurements, without any need to measure either their speed or the clearance from the surrounding walls.
Journal of Comparative Physiology A: Neuroethology, Sensory, Neural, and Behavioral PhysiologyVolume 196, Number 4 / April, 2010307-313
The scaling of myofibrillar actomyosin ATPase activity in apid bee flight muscle in relation to hovering flight energetics
Graham N. Askew1,*, Richard T. Tregear2 and Charles P. Ellington3g.n.askew@leeds.ac.uk
1 Institute of Integrative and Comparative Biology, University of Leeds, Leeds, UK
2 MRC Laboratory of Molecular Biology, Hills Road, Cambridge, UK
3 Department of Zoology, Downing Street, University of Cambridge, Cambridge, UK
2 MRC Laboratory of Molecular Biology, Hills Road, Cambridge, UK
3 Department of Zoology, Downing Street, University of Cambridge, Cambridge, UK
For all types of locomotion, the overall efficiency with whichchemical energy is converted into mechanical work increaseswith increasing body size. In order to gain insight into thedeterminants of the scaling of overall efficiency, we measuredthe scaling of the rate of ATP utilisation during cyclical contractionsusing glycerinated fibres from the dorsolongitudinal flightmuscle of several species of apid bees, covering a ninefoldrange in body mass. The efficiency of ATP utilisation by thecrossbridges is one of the stages that determines the overallefficiency of locomotion. The mechanochemical coefficient wascalculated from the ratio of the net power output to the rateof ATP hydrolysis and ranged from 6.5 to 9.7 kJ mol–1 ATP. The corresponding gross myofibrillar efficiency was 15–23%,increasing concomitantly with body mass (Mb) and decreasingwith increasing wingbeat frequency (n) and scaling as Mb0.184 and n–1.168 in bumblebees and as Mb0.153 and n–0.482 in euglossine bees. Overall efficiency of hovering in bumblebeesand euglossine bees was calculated using previously publishedmetabolic power data and revised estimates of the mechanicalpower output to take into account the drag due to the leadingedge vortex that has not been included in previous models. Thescaling of overall efficiency of hovering flight in apid beeswas not as pronounced as the scaling of myofibrillar efficiency.Therefore the scaling of myofibrillar efficiency with body mass(or frequency) only explained part of the scaling of overallefficiency, and it is likely that the efficiency of other stepsin the transduction of chemical energy into mechanical work(e.g. the efficiency of mitochondrial oxidative recovery) mayalso scale with body mass.
Journal of Experimental Biology 213, 1195-1206 (2010)
http://jeb.biologists.org/cgi/content/abstract/213/7/1195
http://jeb.biologists.org/cgi/content/abstract/213/7/1195
Insect Biochemistry
Apolipophorin-III expression and low density lipophorin formation during embryonic development of the silkworm, Bombyx mori
Kozo Tsuchidaa, , , Takeru Yokoyamaa, Takashi Sakudoha, Chihiro Katagirib, Shuichiro Tsurumaruc, Naoko Takadaa, Hirofumi Fujimotoa, Rolf Zieglerd, Hidetoshi Iwanoe, Kunikatsu Hamanof and Toshinobu Yaginumac
a Division of Radiological Protection and Biology, National Institute of Infectious Diseases, Tokyo, Japan
b Institute of Low Temperature Science, Hokkaido University, Sapporo, Japan
c Graduate School of Bioagricultural Sciences, Nagoya University, Nagoya, Japan
d Department of Entomology, University of Arizona, Tucson, AZ85721, USA
e College of Bioresource Sciences, Nihon University, Fujisawa, Japan
f Department of International Environmental and Agricultural Science, Tokyo University of Agriculture and Technology, Fuchu, Japan
We examined the expression of apolipophorin-III (apoLp-III) during embryonic development of the silkworm Bombyx mori. ApoLp-III mRNA was first expressed 24 h after oviposition, which corresponds to the time of germ band formation. The amount of apoLp-III in the eggs increased from day 2, peaked on day 4, and then gradually decreased until hatching (on day 9.5). ApoLp-III was apparently synthesized during early embryogenesis, as radioactive amino acids were incorporated into newly synthesized apoLp-III in three-day-old eggs. Moreover, radioactive apoLp-III was found only in the embryo and not in the extraembryonic tissue. KBr density gradient ultracentrifugation of egg homogenates showed that apoLp-III was associated with low-density lipophorin (LDLp). These results suggest that LDLp is required for the delivery of lipids for organogenesis during embryogenesis.
Comparative Biochemistry and Physiology Part B: Biochemistry and Molecular BiologyVolume 155, Issue 4, April 2010, Pages 363-370
Role of the triad N46, S106 and T107 and the surface charges in the determination of the acidic pH optimum of digestive lysozymes from Musca domestica
a Departamento de Bioquímica, Instituto de Química, Universidade de São Paulo, CP 26077, São Paulo, 05513-970, São Paulo, Brazil
b Center for Structural Biology (CeBiME), Brazilian Synchrotron Light Laboratory (LNLS), CP 6192, Campinas, SP 13084-971, Brazil
c Departamento de Bioquímica, Universidade Estadual de Campinas, Brazil
Structures of digestive lysozymes 1 and 2 from housefly (MdL1 and MdL2) show that S106–T107 delimit a polar pocket around E32 (catalytic acid/base) and N46 contributes to the positioning of D50 (catalytic nucleophile), whereas those residues are replaced by V109–A110 and D48 in the non-digestive lysozyme from hen egg-white (HEWL). Further analyses revealed that MdL1 and MdL2 surfaces are less positively charged than HEWL surface. To verify the relevance of these differences to the acidic pH optimum of digestive lysozymes it was determined that pKas of the catalytic residues of the triple mutant MdL2 (N46D–S106V–T107A) are similar to HEWL pKas and higher than those for MdL2. In agreement, triple mutant MdL2 and HEWL exhibits the same pH optimum upon methylumbelliferylchitotrioside. In addition to that, the introduction of six basic residues on MdL1 surface increased by 1 unit the pH optimum for the activity upon bacterial walls. Thus, the acidic pH optimum for MdL2 and MdL1 activities upon methylumbelliferylchitotrioside is determined by the presence of N46, S106 and T107 in the environment of their catalytic residues, which favors pKas reduction. Conversely, acidic pH optimum upon bacterial walls is determined by a low concentration of positive charges on the MdL2 and MdL1 surfaces.
Comparative Biochemistry and Physiology Part B: Biochemistry and Molecular Biology
Volume 155, Issue 4, April 2010, Pages 387-395
Volume 155, Issue 4, April 2010, Pages 387-395
Insect Cell Biology
A Role of Receptor Notch in Ligand cis-Inhibition in Drosophila
Institute for Research in Biomedicine (IRB Barcelona), Parc Científic de Barcelona, Baldiri Reixac 10-12, 08028 Barcelona, Spain Institució Catalana de Recerca i Estudis Avançats, Parc Científic de Barcelona, Baldiri Reixac 10-12, 08028 Barcelona, Spain Department of Genetics, University of Cambridge, Cambridge CB2 3EH, UK Corresponding author
Highlights Notch reduces the level of Serrate at the membrane independently of transcription. Notch exerts an inhibitory effect on Serrate expressed in the same cell. The extracellular domain of Notch is sufficient to cis-inactivate Serrate. Mutual interactions in cis between ligand and receptor restrict Notch activation.
SummaryNotch and its ligands mediate short-range cell interactions that play a conserved role in inducing cell fate specification [1]. Several regulatory mechanisms have been described to ensure robust polarized signaling from signal-sending to signal-receiving cells. High levels of ligand expression activate Notch in nearby cells and exert a cell-autonomous dominant-negative effect on Notch activity. This regulatory process is called cis-inhibition and helps to restrict Notch activation to signal-receiving cells [2,3,4,5,6]. By combining genetic mosaics in the Drosophila wing primordium with cell culture assays, we present evidence here that Notch promotes the clearance of Serrate ligand from the cell surface and exerts an inhibitory effect on the activity of Serrate expressed in the same cell. These regulatory mechanisms are independent of Notch-mediated transcription and are executed by the extracellular domain of Notch. We show that this process is required to block Serrate-mediated activation of Notch in the signal-sending cell population and helps to restrict Notch activation to the signal-receiving cells. Altogether, our results, in concert with previous results on ligand-mediated Notch cis-inhibition, indicate that mutual inhibition between ligand and receptor in signal-sending cells helps to block Notch activity in these cells and to restrict receptor activation in signal-receiving cells.
Insect Chemoreception
Mating-induced transient inhibition of responses to sex pheromone in a male moth is not mediated by octopamine or serotonin
Romina B. Barrozo, David Jarriault, Xenia Simeone, Cyril Gaertner, Christophe Gadenne and Sylvia Anton*santon@versailles.inra.fr
UMR 1272 INRA-UPMC Physiologie de l'Insecte: Signalisation et Communication, F-78000 Versailles, France
In the male moth, Agrotis ipsilon, mating induces a transientinhibition of behavioural and central nervous responses to sexpheromone. Newly mated males are not attracted to sex pheromone,and the sensitivity of their antennal lobe (AL) neurons is lowerthan in virgin males. This rapid transient olfactory inhibitionprevents them from re-mating unsuccessfully until they haverefilled their sex glands. We hypothesized that this olfactory‘switch off’ might be controlled by neuromodulatorssuch as biogenic amines. To test our hypothesis, we studiedthe effects of octopamine (OA) and serotonin (5-hydroxytryptamine,5-HT) on the coding properties of pheromone-sensitive AL neuronsin virgin and newly mated males. We show that AL neuron sensitivityincreased in newly mated males after injection of OA or 5-HT,but only OA treatment affected certain response characteristicsof AL neurons in virgin males. Whereas all measured AL neuronresponse characteristics were different between virgin and newlymated males, amine treatment in newly mated males restored onlythe latency and spike frequency, but not the duration of excitatoryand inhibitory phases, which were initially found in virginmales. Additionally, we investigated the behavioural effectsof OA and 5-HT treatments in virgin and mated males. AlthoughOA and 5-HT enhanced the general flight activity of newly matedmales, amine treatments did not restore the behavioural pheromoneresponse of mated moths. Altogether, these results show that,although biogenic amines modulate the olfactory system in moths,OA and 5-HT are probably not involved in the post-mating inhibitionof responses to sex pheromone in A. ipsilon males
Journal of Experimental Biology 213, 1100-1106 (2010)
Insect Ecology
Climatic warming increases voltinism in European butterflies and moths
Climate change is altering geographical ranges, population dynamics and phenologies of many organisms. For ectotherms, increased ambient temperatures frequently have direct consequences for metabolic rates, activity patterns and developmental rates. Consequently, in many insect species both an earlier beginning and prolongation of seasonal duration occurred in parallel with recent global warming. However, from an ecological and evolutionary perspective, the number of generations (voltinism) and investment into each generation may be even more important than seasonality, since an additional generation per unit time may accelerate population growth or adaptation. Using a dataset extending back to the mid-nineteenth century, I report changes in the voltinism of butterfly and moth species of Central Europe. A significant proportion of 263 multi-voltine species showed augmented frequency of second and subsequent generations relative to the first generation in a warm period since 1980, and 44 species even increased the number of generations after 1980. Expected ecological consequences are diverse. Since multi-voltinism has been linked to insect outbreaks they include an increase in the abundance of herbivorous pests of agriculture and forestry. However, disruption of the developmental synchrony associated with multi-voltinism and host plant phenology may also reduce fitness, potentially having unexpected consequences for species of conservation concern. The ability of species to adapt evolutionarily to a changing environment may be facilitated by increased voltinism.
Proc. R. Soc. B 22 April 2010 vol. 277 no. 1685 1281-1287
Insect Evolution
COMPONENTS OF REPRODUCTIVE ISOLATION BETWEEN NORTH AMERICAN PHEROMONE STRAINS OF THE EUROPEAN CORN BORER
Erik B.Dopman 1,2 , Paul S. Robbins 3,4 , and Abby Seaman 5,6
1Department of Biology, Tufts University, 163 Packard Avenue, Medford, Massachusetts 02155 2E-mail: erik.dopman@tufts.edu 3Department of Entomology, Cornell University, Geneva, New York 14456 4E-mail: psr1@nysaes.cornell.edu 5Integrated Pest Management Program, Cornell University, Geneva, New York 14456 6E-mail: ajs32@cornell.edu
Of 12 potential reproductive isolating barriers between closely related Z- and E-pheromone strains of the European corn borer moth (Ostrinia nubilalis), seven significantly reduced gene flow but none were complete, suggesting that speciation in this lineage is a gradual process in which multiple barriers of intermediate strength accumulate. Estimation of the cumulative effect of all barriers resulted in nearly complete isolation (>99%), but geographic variation in seasonal isolation allowed as much as ∼10% gene flow. With the strongest barriers arising from mate-selection behavior or ecologically relevant traits, sexual and natural selection are the most likely evolutionary processes driving population divergence. A recent multilocus genealogical study corroborates the roles of selection and gene flow (Dopman et al. 2005), because introgression is supported at all loci besides Tpi, a sex-linked gene. Tpi reveals strains as exclusive groups, possesses signatures of selection, and is tightly linked to a QTL that contributes to seasonal isolation. With more than 98% of total cumulative isolation consisting of prezygotic barriers, Z and E strains of ECB join a growing list of taxa in which species boundaries are primarily maintained by the prevention of hybridization, possibly because premating barriers evolve during early stages of population divergence.
INTRINSIC REPRODUCTIVE ISOLATION BETWEEN TWO SISTER SPECIES OF DROSOPHILA
Daniel R.Matute 1,2 and Jerry A. Coyne 1,3
1Department of Ecology and Evolution, The University of Chicago, 1101 E. 57 Street, Chicago, Illinois 60637 2E-mail: dmatute@uchicago.edu 3E-mail: j-coyne@uchicago.edu
Drosophila santomea and D. yakuba are sister species that live on the volcanic African island of São Tomé. Previous work has revealed several barriers to gene flow, including sexual isolation, hybrid sterility, and "extrinsic" ecological isolation based on differential adaptation to and preference for temperature. Here, we describe several new "intrinsic" barriers to gene flow—barriers that do not depend on the species' ecology. These include reduced egg number, reduced egg hatchability, and faster depletion of sperm in interspecific compared to intraspecific matings. Further, hatching interval and egg-to-adult development time are significantly longer in interspecific than intraspecific crosses. If a female of either species is initially mated to a heterospecific male, she lays fewer and less-fertile eggs than if she is first mated to a conspecific male, so that heterospecific matings permanently reduce female fertility. Finally, D. santomea females mated to D. yakuba males do not live as long as virgin or conspecifically mated females. The "poisoning" effects of heterospecific ejaculates may be byproducts of antagonistic sexual selection. Although these species diverged relatively recently, they are clearly separated by many isolating barriers that act both before and after mating.
MULTITRAIT, HOST-ASSOCIATED DIVERGENCE AMONG SETS OF BUTTERFLY POPULATIONS: IMPLICATIONS FOR REPRODUCTIVE ISOLATION AND ECOLOGICAL SPECIATION
Michael C.Singer 1,2 and Carolyn S. McBride 3,4,5
1Integrative Biology, Patterson Laboratories, University of Texas at Austin, Austin, Texas 78712 2E-mail: sing@mail.utexas.edu 3Center for Population Biology, University of California at Davis, Davis, California 95616 5E-mail: lmcbride@rockefeller.edu
When populations use different resources, they tend to diverge in traits that affect performance on those resources. The extent and complexity of divergence that is achieved will depend on gene flow, genetic constraints, and the character of divergent selection. We describe divergent host adaptation among Californian populations of the Melitaeine butterfly, Euphydryas editha. Divergence in seven traits created parallel phenotypic suites, each suite associated with the use of a different host species, either Collinsia torreyi or Pedicularis semibarbata. The suites involved alighting responses of adults (probably to visual stimuli), chemosensory responses to leaf surfaces, vertical positioning of adults and larvae (probably due to geotaxis), partitioning of reproductive effort among clutches, and larval performance. Remarkably, the divergent suites did not occur sympatrically, despite ubiquitous co-occurrence of the hosts, and we know of only one site where any Collinsia species is used sympatrically with another host. In contrast, E. editha often uses two host genera sympatrically when neither of them is Collinsia. We suggest that adaptation to Collinsia is incompatible with adaptation to other hosts and may generate extrinsic postzygotic reproductive isolation among populations. Despite the apparent rarity of host-shift-associated speciation in Melitaeine butterflies, adoption of Collinsia as a host may lead to allopatric ecological speciation.
POPULATIONS OF MONARCH BUTTERFLIES WITH DIFFERENT MIGRATORY BEHAVIORS SHOW DIVERGENCE IN WING MORPHOLOGY
SoniaAltizer 1,2 and Andrew K. Davis 3
1Odum School of Ecology, The University of Georgia, Athens, Georgia 30602 2E-mail: saltizer@uga.edu 3D.B. Warnell School of Forestry and Natural Resources, The University of Georgia, Athens, Georgia 30602
The demands of long-distance flight represent an important evolutionary force operating on the traits of migratory species. Monarchs are widespread butterflies known for their annual migrations in North America. We examined divergence in wing morphology among migratory monarchs from eastern and western N. America, and nonmigratory monarchs in S. Florida, Puerto Rico, Costa Rica, and Hawaii. For the three N. American populations, we also examined monarchs reared in four common environment experiments. We used image analysis to measure multiple traits including forewing area and aspect ratio; for laboratory-reared monarchs we also quantified body area and wing loading. Results showed wild monarchs from all nonmigratory populations were smaller than those from migratory populations. Wild and captive-reared eastern monarchs had the largest and most elongated forewings, whereas monarchs from Puerto Rico and Costa Rica had the smallest and roundest forewings. Eastern monarchs also had the largest bodies and high measures of wing loading, whereas western and S. Florida monarchs had less elongated forewings and smaller bodies. Among captive-reared butterflies, family-level effects provided evidence that genetic factors contributed to variation in wing traits. Collectively, these results support evolutionary responses to long-distance flight in monarchs, with implications for the conservation of phenotypically distinct wild populations.
LARGE-SCALE EVOLUTIONARY PATTERNS OF HOST PLANT ASSOCIATIONS IN THE LEPIDOPTERA
Steph B. J.Menken 1,2 , Jacobus J. Boomsma 3,4 , and Erik J. van Nieukerken 5,6
1Institute for Biodiversity and Ecosystem Dynamics, Section Evolutionary Biology, University of Amsterdam, Kruislaan 318, 1098 SM Amsterdam, The Netherlands 2E-mail: S.B.J.Menken@uva.nl 3Department of Biology, University of Copenhagen, Universitetsparken 15, 2100 Copenhagen, Denmark 4E-mail: JJBoomsma@bio.ku.dk 5National Museum of Natural History Naturalis, P.O. Box 9517, 2300 RA Leiden, The Netherlands 6E-mail: Nieukerken@naturalis.nl
We characterized evolutionary patterns of host plant use across about 2500 species of British Lepidoptera, using character optimization and independent phylogenetic contrasts among 95 operational taxa, and evaluated the extent to which caterpillars are monophagous, use woody host plants, and feed concealed. We also analyzed the use of different Angiosperm superorders and related these associations to other key variables. The Nepticulidae, Pterophoridae, and Gracillariidae allowed explicit comparisons between the British fauna and the Lepidoptera worldwide, which indicated that our broad categorizations for Britain are accurate predictors for the global fauna. The first (lower glossatan) radiation of the Lepidoptera started with monophagous, internal feeding on woody Eurosids I. Polyphagy on nonwoody Eurosids I evolved together with the ability to feed externally, but did initially not produce significant radiations. Exposed feeding became associated with radiations in the lower Ditrysia and Apoditrysia and remained correlated with more polyphagy, fewer woody host plants, and increasing use of other Angiosperm superorders. The macrolepidopteran radiation has frequent reversals to monophagy on woody Eurosids I, particularly in taxa that lost concealed feeding. We discuss the general implications of these results and address several key adaptations and constraints that have characterized the major transitions in lepidopteran life histories.
Insect Hearing
Intensity invariance properties of auditory neurons compared to the statistics of relevant natural signals in grasshoppers
Jan Clemens1, 2 , Gerroth Weschke1, Astrid Vogel1 and Bernhard Ronacher1, 2
(1) Abteilung Verhaltensphysiologie, Institut für Biologie der Humboldt-Universität zu Berlin, Invalidenstr. 43, 10999 Berlin, Germany
(2) Bernstein Center for Computational Neuroscience Berlin, Philippstrasse 13, 10115 Berlin, Germany
The temporal pattern of amplitude modulations (AM) is often used to recognize acoustic objects. To identify objects reliably, intensity invariant representations have to be formed. We approached this problem within the auditory pathway of grasshoppers. We presented AM patterns modulated at different time scales and intensities. Metric space analysis of neuronal responses allowed us to determine how well, how invariantly, and at which time scales AM frequency is encoded. We find that in some neurons spike-count cues contribute substantially (20–60%) to the decoding of AM frequency at a single intensity. However, such cues are not robust when intensity varies. The general intensity invariance of the system is poor. However, there exists a range of AM frequencies around 83 Hz where intensity invariance of local interneurons is relatively high. In this range, natural communication signals exhibit much variation between species, suggesting an important behavioral role for this frequency band. We hypothesize, just as has been proposed for human speech, that the communication signals might have evolved to match the processing properties of the receivers. This contrasts with optimal coding theory, which postulates that neuronal systems are adapted to the statistics of the relevant signals.
Journal of Comparative Physiology A: Neuroethology, Sensory, Neural, and Behavioral PhysiologyVolume 196, Number 4 / April, 2010 285-297
Neural responses to one- and two-tone stimuli in the hearing organ of the dengue vector mosquito
Ben J. Arthur1,*, Robert A. Wyttenbach1, Laura C. Harrington2 and Ronald R. Hoy1 bja28@cornell.edu
1 Department of Neurobiology and Behavior, Cornell University, Ithaca, NY, 14853, USA
2 Department of Entomology, Cornell University, Ithaca, NY, 14853, USA
2 Department of Entomology, Cornell University, Ithaca, NY, 14853, USA
Recent studies demonstrate that mosquitoes listen to each other'swing beats just prior to mating in flight. Field potentialsfrom sound-transducing neurons in the antennae contain bothsustained and oscillatory components to pure and paired tonestimuli. Described here is a direct comparison of these twotypes of response in the dengue vector mosquito, Aedes aegypti.Across a wide range of frequencies and intensities, sustainedresponses to one- and two-tone stimuli are about equal in magnitudeto oscillatory responses to the beats produced by two-tone stimuli.All of these responses are much larger than the oscillatoryresponses to one-tone stimuli. Similarly, the frequency rangeextends up to at least the fifth harmonic of the male flighttone for sustained responses to one- and two-tone stimuli andoscillatory responses at the beat frequency of two-tone stimuli,whereas the range of oscillatory response to a one-tone stimulusis limited to, at most, the third harmonic. Thresholds nearthe fundamental of the flight tone are lower for oscillatoryresponses than for sustained deflections, lower for males thanfor females, and within the behaviorally relevant range. A simplemodel of the transduction process can qualitatively accountfor both oscillatory and sustained responses to pure and pairedtones. These data leave open the question as to which of severalalternative strategies underlie flight tone matching behaviorin mosquitoes.
Journal of Experimental Biology 213, 1376-1385 (2010)
http://jeb.biologists.org/cgi/content/abstract/213/8/1376
http://jeb.biologists.org/cgi/content/abstract/213/8/1376
Insect Heredity
The clock gene cryptochrome of Bactrocera cucurbitae (Diptera: Tephritidae) in strains with different mating times
T Fuchikawa1, S Sanada2, R Nishio1, A Matsumoto3, T Matsuyama4, M Yamagishi5, K Tomioka6, T Tanimura7 and T Miyatake1miyatake@cc.okayama-u.ac.jp
1Laboratory of Evolutionary Ecology, Graduate School of Environmental Science, Okayama University, Okayama, Japan
2National Agricultural Research Center for Kyushu Okinawa Region, Kumamoto, Japan
3Department of Biology, Juntendo University School of Medicine, Chiba, Japan
4Okinawa Prefectural Agricultural Experiment Station, Naha, Okinawa, Japan
5Okinawa Prefectural Plant Protection Center, Naha, Okinawa, Japan
6Graduate School of Natural Science and Technology, Okayama University, Okayama, Japan
7Department of Biology, Graduate school of Science, Kyushu University, Hakozaki, Fukuoka, Japan
Differences in mating time between populations can give rise to premating reproductive isolation. Tephritid fruit flies exhibit large variation in mating time among intra- or inter-specific populations. We previously cloned the clock gene period from two strains of melon fly, Bactrocera cucurbitae; in one the individuals mate early during the day, whereas in the other the individuals mate later. These strains were originally established by divergent artificial selection for developmental time, ‘short’ and ‘long’, with early and late mating times, respectively. The deduced amino acid sequences of PERIOD proteins for these two strains were reported to be identical. Here we cloned another clock gene cryptochrome (cry) from the two strains, and found two stable amino acid substitutions in the strains. In addition, the allele frequency at the two polymorphic sites of cry gene correlated with the circadian locomotor period (τ) across strains, whereas the expression pattern of cry mRNA in the heads of flies taken from the short strain significantly differed from that from the long strain. These findings suggest that variation in the cry gene is related to differences in the circadian behaviour in the two strains, thus implying that the cry gene may have an important role in reproductive isolation.
Heredity (2010) 104, 387–392
Chromosomal mapping of repetitive DNAs in the beetle Dichotomius geminatus provides the first evidence for an association of 5S rRNA and histone H3 genes in insects, and repetitive DNA similarity between the B chromosome and A complement
D C Cabral-de-Mello1, R C Moura2 and C Martins1cmartins@ibb.unesp.br
1Departamento de Morfologia, Instituto de Biociências, UNESP-Universidade Estadual Paulista, Botucatu, São Paulo, Brazil
2Departamento de Biologia, Instituto de Ciências Biológicas, UPE-Universidade de Pernambuco, Recife, Pernambuco, Brazil
Chromosomal banding techniques and repetitive DNA mapping are useful tools in comparative analysis and in the elucidation of genome organization of several groups of eukaryotes. In this study, we contributed to the knowledge of Coleoptera genomes by reporting the chromosomal organization of repetitive DNA sequences, as well as the presence and characteristics of a B chromosome in two natural populations of Dichotomius geminatus (Coleoptera; Scarabaeidae) using classical, chromosomal banding and molecular cytogenetic techniques. As in other coleopteran species, the heterochromatin was mainly concentrated in pericentromeric regions and the B chromosome was composed almost entirely of heterochromatin. Physical mapping using double fluorescent in situ hybridization was performed for the first time in Coleoptera; using DNA probes for 5S and 18S ribosomal RNA (rRNA) and histone H3 genes, we showed that ribosomal 18S rDNAs are located in chromosomes 3 and 4, whereas 5S rRNA and histone H3 genes are colocalized in chromosomal pair 2 and show an apparently interspersed organization. Moreover, these genes are not present in the B chromosome, suggesting that the B chromosome did not originate from chromosomal pairs 2, 3 or 4. On the other hand, mapping of the C0t-1 DNA fraction showed that the B chromosome is enriched in repetitive DNA elements, also present in the standard complement, indicating an intraspecific origin of this element in D. geminatus. These results will contribute to our understanding of genome organization and evolution of repetitive elements in Coleoptera and other insects regarding both A and B chromosomes.
Heredity (2010) 104, 393–400
Insect Learning
Place memory formation in Drosophila is independent of proper octopamine signaling
Divya Sitaraman1, Melissa Zars1 and Troy Zars1 zarst@missouri.edu
Division of Biological Sciences, University of Missouri, 114 Lefevre Hall, Columbia, MO 65211, USA
The biogenic amines play a critical role in establishing memories. In the insects, octopamine, dopamine, and serotonin have key functions in memory formation. For Drosophila, octopamine is necessary and sufficient for appetitive olfactory memory formation. Whether octopamine plays a general role in reinforcing memories in the fly is not known. Place learning in the heat-box associates high temperatures with one part of a narrow chamber, and a cool, strongly preferred temperature with the other half of the chamber. The cool-temperature-associated chamber half could provide a rewarding stimulus to a fly, and thus a place memory is composed of an aversive and rewarded memory component. The role of octopamine in place memory was thus tested. Using a mutation in the tyramine beta hydroxylase (TβH[M18]) and blocking of evoked synaptic transmission in the octopamine (and tyramine) neurons labeled with a tyramine decarboxylase-2 (TDC2) gene regulatory elements we found that reinforcement of place memories is independent of normal octopamine signaling. Thus, reinforcing mechanisms in Drosophila have specialized systems in the formation of specific memory types.
Journal of Comparative Physiology A: Neuroethology, Sensory, Neural, and Behavioral PhysiologyVolume 196, Number 4 / April, 2010 299-305
Insect Molecular Ecology
Six quantitative trait loci influence task thresholds for hygienic behaviour in honeybees (Apis mellifera)
PETER R. OXLEY*, MARLA SPIVAK† and BENJAMIN P. OLDROYD* peter.oxley@usyd.edu.au
*Behaviour and Genetics of Social Insects Laboratory, School of Biological Sciences, University of Sydney, Sydney, NSW 2006, Australia , †Department of Entomology, University of Minnesota, Minneapolis, MN 55108, USA
Honeybee hygienic behaviour provides colonies with protection from many pathogens and is an important model system of the genetics of a complex behaviour. It is a textbook example of complex behaviour under simple genetic control: hygienic behaviour consists of two components – uncapping a diseased brood cell, followed by removal of the contents – each of which are thought to be modulated independently by a few loci of medium to large effect. A worker's genetic propensity to engage in hygienic tasks affects the intensity of the stimulus required before she initiates the behaviour. Genetic diversity within colonies leads to task specialization among workers, with a minority of workers performing the majority of nest-cleaning tasks. We identify three quantitative trait loci that influence the likelihood that workers will engage in hygienic behaviour and account for up to 30% of the phenotypic variability in hygienic behaviour in our population. Furthermore, we identify two loci that influence the likelihood that a worker will perform uncapping behaviour only, and one locus that influences removal behaviour. We report the first candidate genes associated with engaging in hygienic behaviour, including four genes involved in olfaction, learning and social behaviour, and one gene involved in circadian locomotion. These candidates will allow molecular characterization of this distinctive behavioural mode of disease resistance, as well as providing the opportunity for marker-assisted selection for this commercially significant trait.
Fine-scale spatial and temporal population genetics of Aedes japonicus, a new US mosquito, reveal multiple introductions
D. M.FONSECA*, A. K. WIDDEL†, M. HUTCHINSON‡, S.-E. SPICHIGER‡ and L. D. KRAMER§ fonseca@aesop.rutgers.edu
*Center for Vector Biology, Rutgers University, 180 Jones Av., New Brunswick, NJ 08901, USA , †Laboratory of Molecular Systematics and Ecology, Academy of Natural Sciences, 1900 Benjamin Franklin Parkway, Philadelphia, PA 19103, USA , ‡Division of Vector Management, Pennsylvania Department of Environmental Protection, Box 1467 Harrisburg, PA 17105-1467, USA , §Wadsworth Center, NY State Dept. of Health, 5668 State Farm Road, Guilderland, NY 12084, USA
The newly introduced mosquito Aedes japonicus has expanded from its original range in Northeastern Asia to 29 US states (including Hawaii) plus Canada and northern Europe. Our objectives were to test an earlier hypothesis of multiple introductions of this species to the Northeastern US and evaluate putative temporal changes in genetic makeup. Using a panel of seven microsatellite loci, we confirmed the existence of two abundant genetic forms in specimens originally collected in 1999–2000 (FST value based on microsatellite data = 0.26) that matches the disjunctive distribution of mitochondrial haplotypes. To examine the distribution of the two genetic 'types' across Pennsylvania we created a fine-scale genetic map of Ae. japonicus using 439 specimens collected from 54 Pennsylvania counties in 2002–2003. We also made direct comparisons between collections in 1999–2000 and new collections made in 2004–2005 obtained from the same areas in the northeastern US. We observed that the strong association between mtDNA haplotype and microsatellite signature seen in 1999–2000 had weakened significantly by 2002 across Pennsylvania, a trend continued to some extent in 2004–2005 in PA, NJ, and NY, indicating that once easily distinguishable separate introductions are merging. The two expanding genetic forms create a complex correlation between spatial and genetic distances. The existence of multiple introductions would be obscured without sampling early and across time with highly polymorphic molecular markers. Our results provide a high-resolution analysis of the spatial and temporal dynamics of a newly introduced disease vector and argue that successive introductions may be a common pattern for invasive mosquitoes.
Population genetic data suggest a role for mosquito-mediated dispersal of West Nile virus across the western United States
*The W. Harry Feinstone Department of Molecular Microbiology and Immunology, Bloomberg School of Public Health, Johns Hopkins University, Baltimore, MD 21205, USA , †Center for Vaccine Development and Howard Hughes Medical Institute, University of Maryland School of Medicine, 685 West Baltimore Street, HSF1-480, Baltimore, MD 21201, USA , ‡The Johns Hopkins Malaria Research Institute, Baltimore, MD 21205, USA
After introduction, West Nile virus (WNV) spread rapidly across the western United States between the years 2001 and 2004. This westward movement is thought to have been mediated by random dispersive movements of resident birds. Little attention has been placed on the role of mosquito vectors in virus dispersal across North America. The mosquito vector largely responsible for WNV amplification and transmission of WNV in the western USA is Culex tarsalis. Here we present population genetic data that suggest a potential role for C. tarsalis in the dispersal of WNV across the western USA. Population genetic structure across the species range of C. tarsalis in the USA was characterized in 16 states using 12 microsatellite loci. structure and geneland analyses indicated the presence of three broad population clusters. Barriers to gene flow were resolved near the Sonoran desert in southern Arizona and between the eastern Rocky Mountains and High Plains plateau. Small genetic distances among populations within clusters indicated that gene flow was not obstructed over large portions of the West Coast and within the Great Plains region. Overall, gene flow in C. tarsalis appears to be extensive, potentially mediated by movement of mosquitoes among neighbouring populations and hindered in geographically limited parts of its range. The pattern of genetic clustering in C. tarsalis is congruent with the pattern of invasion of WNV across the western United States, raising the possibility that movement of this important vector may be involved in viral dispersal.
Ecology, Wolbachia infection frequency and mode of reproduction in the parasitoid wasp Tetrastichus coeruleus (Hymenoptera: Eulophidae)
*Section Animal Ecology, Institute of Biology Leiden, Sylvius Laboratory, University of Leiden, P.O. Box 9505, 2300 RA Leiden, The Netherlands , †UMR 6553 ECOBIO, Université de Rennes I, Campus de Beaulieu, Avenue du Général Leclerc, 35 042 Rennes cedex, France
Whereas sexual reproduction may facilitate adaptation to complex environments with many biotic interactions, simplified environments are expected to favour asexual reproduction. In agreement with this, recent studies on invertebrates have shown a prevalence of asexual species in agricultural (simplified) but not in natural (complex) environments. We investigated whether the same correlation between reproductive mode and habitat can be found in different populations within one species. The parasitoid wasp Tetrastichus coeruleus forms an ideal model to test this question, since it occurs both in natural and agricultural environments. Further, we investigated whether Wolbachia infection caused parthenogenesis in female-biased populations. In contrast to the general pattern, in Dutch and French natural areas, we found Wolbachia-infected, highly female-biased populations that reproduce parthenogenetically. In contrast, populations on Dutch agricultural fields were not infected with Wolbachia, showed higher frequencies of males and reproduced sexually. However, we also found a female-only, Wolbachia-infected population on agricultural fields in north-eastern United States. All Wolbachia-infected populations were infected with the same Wolbachia strain. At this moment, we do not have a convincing explanation for this deviation from the general pattern of ecology and reproductive mode. It may be that asparagus agricultural fields differ from other crop fields in ways that favour sexual reproduction. Alternatively, Wolbachia may manipulate life history traits in its host, resulting in different fitness pay-offs in different habitats. The fixation of Wolbachia in the United States populations (where the species was introduced) may be due to founder effect and lack of uninfected, sexual source populations.
Insect Morphology
Functional morphology of the female reproductive apparatus of Stephanitis pyrioides (Heteroptera, Tingidae): A novel role for the pseudospermathecae
Daniela Marchini 1 *, Giovanna Del Bene 2, Romano Dallai 1marchinid@unisi.it
1Dipartimento di Biologia Evolutiva, Università degli Studi di Siena, Via A. Moro, 2, I-53100 Siena, Italy
2CRA, Centro di ricerca per l'agrobiologia e la pedologia, Via Lanciola 12A, I-50125 Firenze, Italy
2CRA, Centro di ricerca per l'agrobiologia e la pedologia, Via Lanciola 12A, I-50125 Firenze, Italy
At mating, female insects generally receive and store sperm in specific organs of their reproductive tract called spermathecae. Some Heteroptera, such as Cimicomorpha, lack a true spermatheca; some have receptacles of novel formation where sperm cells can transit or be stored. In Tingidae, there are two sac-like diverticula, the pseudospermathecae,each at the base of a lateral oviduct, which previously were considered to function as spermathecae. However, this role has never been documented, either by ultrastructural studies or by observations of sperm transit in the female reproductive tract. In this article, we investigate the morphology and the ultrastructure of the female reproductive apparatus in the economically important tingid species Stephanitis pyrioides, focusing our attention on the functional role of the pseudospermathecae in an evolutionary perspective. Each ovary consists of seven telotrophic meroistic ovarioles, the long pedicels of which enlarge into a bulb-like structure near the terminal oocyte. The ovarioles flow into two long lateral oviducts, which join to form a very short common oviduct. Basally, each lateral oviduct is connected through a short duct to one of two pseudospermathecae. The ultrastructure of the ectodermal epithelium of the pseudospermathecae is dramatically different in sexually immature or mated females. In virgin females, cells delimit a very irregular lumen, filled with a moderately electron-dense granular material. The large nucleus adapts to their irregular shape, which can have long projections in some regions and be flattened in others. After mating, epithelial cells generally elongate and display an apical layer of microvilli extending beneath the cuticle, often containing mitochondria. In the lumen of the pseudospermathecae there is a dense brownish secretion. No sperm cells were ever found inside this organ. After mating, sperm move upward along the lateral oviducts and the ovarioles, accumulating in the bulb-like structure of the pedicels, and proceeding into the distal region between the follicle cells surrounding the oocyte and the ovariole wall. The egg, most likely fertilized in the bulb-like region of the ovariole, moves through the lateral oviduct, entirely enters the pseudospermatheca and is smeared with its secretion just before oviposition. We exclude a function of sperm storage for the pseudospermathecae, and instead suggest a novel role for these organs as reproductive accessory glands. J. Morphol., 2010. © 2009 Wiley-Liss, Inc.
Insect Neuroscience
Immunocytochemical localization of synaptic proteins to photoreceptor synapses of Drosophila melanogaster
Yoshitaka Hamanaka 1 3, Ian A. Meinertzhagen 1 2 3 *iam@dal.ca
1Department of Psychology, Life Sciences Centre, Dalhousie University, Halifax, Nova Scotia, Canada B3H 4J1
2Department of Biology, Life Sciences Centre, Dalhousie University, Halifax, Nova Scotia, Canada B3H 4J1
3Neuroscience Institute, Life Sciences Centre, Dalhousie University, Halifax, Nova Scotia, Canada B3H 4J1
2Department of Biology, Life Sciences Centre, Dalhousie University, Halifax, Nova Scotia, Canada B3H 4J1
3Neuroscience Institute, Life Sciences Centre, Dalhousie University, Halifax, Nova Scotia, Canada B3H 4J1
The location of proteins that contribute to synaptic function has been widely studied in vertebrate synapses, far more than at model synapses of the genetically manipulable fruit fly, Drosophila melanogaster. Drosophila photoreceptor terminals have been extensively exploited to characterize the actions of synaptic genes, and their distinct and repetitive synaptic ultrastructure is anatomically well suited for such studies. Synaptic release sites include a bipartite T-bar ribbon, comprising a platform surmounting a pedestal. So far, little is known about the composition and precise location of proteins at either the T-bar ribbon or its associated synaptic organelles, knowledge of which is required to understand many details of synaptic function. We studied the localization of candidate proteins to pre- or postsynaptic organelles, by using immuno-electron microscopy with the pre-embedding method, after first validating immunolabeling by confocal microscopy. We used monoclonal antibodies against Bruchpilot, epidermal growth factor receptor pathway substrate clone 15 (EPS-15), and cysteine string protein (CSP), all raised against a fly head homogenate, as well as sea urchin kinesin (antibody SUK4) and Discs large (DLG). All these antibodies labeled distinct synaptic structures in photoreceptor terminals in the first optic neuropil, the lamina, as did rabbit anti-DPAK (Drosophila p21 activated kinase) and anti-Dynamin. Validating reports from light microscopy, immunoreactivity to Bruchpilot localized to the edge of the platform, and immunoreactivity to SUK4 localized to the pedestal of the T-bar ribbon. Anti-DLG recognized the photoreceptor head of capitate projections, invaginating organelles from surrounding glia. For synaptic vesicles, immunoreactivity to EPS-15 localized to sites of endocytosis, and anti-CSP labeled vesicles lying close to the T-bar ribbon. These results provide markers for synaptic sites, and a basis for further functional studies.
J. Comp. Neurol. 518:1133-1155, 2010.
Development of nitrergic neurons in the nervous system of the locust embryo
Michael Stern 1 *, Nicole Böger 1, René Eickhoff 1, Christina Lorbeer 1, Ulrike Kerssen 1, Maren Ziegler 1, Giorgio P. Martinelli 2, Gay R. Holstein 2, Gerd Bicker 1Michael.stern@tiho-hannover.de
1Cell Biology, Institute of Physiology, University of Veterinary Medicine Hannover, D-30173 Hannover, Germany
2Department of Neurology, Mount Sinai School of Medicine, New York, New York 10029
2Department of Neurology, Mount Sinai School of Medicine, New York, New York 10029
We followed the development of the nitric oxide-cyclic guanosine monophosphate (NO-cGMP) system during locust embryogenesis in whole mount nervous systems and brain sections by using various cytochemical techniques. We visualized NO-sensitive neurons by cGMP immunofluorescence after incubation with an NO donor in the presence of the soluble guanylyl cyclase (sGC) activator YC-1 and the phosphodiesterase-inhibitor isobutyl-methyl-xanthine (IBMX). Central nervous system (CNS) cells respond to NO as early as 38% embryogenesis. By using the NADPH-diaphorase technique, we identified somata and neurites of possible NO-synthesizing cells in the CNS. The first NADPH-diaphorase-positive cell bodies appear around 40% embryogenesis in the brain and at 47% in the ventral nerve cord. The number of positive cells reaches the full complement of adult cells at 80%. In the brain, some structures, e.g., the mushroom bodies acquire NADPH-diaphorase staining only postembryonically. Immunolocalization of L-citrulline confirmed the presence of NOS in NADPH-diaphorase-stained neurons and, in addition, indicated enzymatic activity in vivo. In whole mount ventral nerve cords, citrulline immunolabeling was present in varying subsets of NADPH-diaphorase-positive cells, but staining was very variable and often weak. However, in a regeneration paradigm in which one of the two connectives between ganglia had been crushed, strong, reliable staining was observed as early as 60% embryogenesis. Thus, citrulline immunolabeling appears to reflect specific activity of NOS. However, in younger embryos, NOS may not always be constitutively active or may be so at a very low level, below the citrulline antibody detection threshold. For the CNS, histochemical markers for NOS do not provide conclusive evidence for a developmental role of this enzyme.
J. Comp. Neurol. 518:1157-1175, 2010.
The circadian timing system in the brain of the fifth larval instar of Rhodnius prolixus (hemiptera)
Xanthe Vafopoulou, Katherine L. Terry, Colin G.H. Steel *csteel@yorku.ca
Department of Biology, York University, Toronto, Ontario M3J 1P3, Canada
The brain of larval Rhodnius prolixus releases neurohormones with a circadian rhythm, indicating that a clock system exists in the larval brain. Larvae also possess a circadian locomotor rhythm. The present paper is a detailed analysis of the distribution and axonal projections of circadian clock cells in the brain of the fifth larval instar. Clock cells are identified as neurons that exhibit circadian cycling of both PER and TIM proteins. A group of eight lateral clock neurons (LNs) in the proximal optic lobe also contain pigment-dispersing factor (PDF) throughout their axons, enabling their detailed projections to be traced. LNs project to the accessory medulla and thence laterally toward the compound eye and medially into a massive area of arborizations in the anterior protocerebrum. Fine branches radiate from this area to most of the protocerebrum. A second group of clock cells (dorsal neurons [DNs]), situated in the posterior dorsal protocerebrum, are devoid of PDF. The DNs receive two fine axons from the LNs, indicating that clock cells throughout the brain are integrated into a timing network. Two axons of the LNs cross the midline, presumably coordinating the clock networks of left and right sides. The neuroarchitecture of this timing system is much more elaborate than any previously described for a larval insect and is very similar to those described in adult insects. This is the first report that an insect timing system regulates rhythmicity in both the endocrine system and behavior, implying extensive functional parallels with the mammalian suprachiasmatic nucleus.
J. Comp. Neurol. 518:1264-1282, 2010.
Actions of motor neurons and leg muscles in jumping by planthopper insects (hemiptera, issidae)
Malcolm Burrows 1 *, Peter Bräunig 2mb135@hermes.cam.ac.uk
1Department of Zoology, University of Cambridge, Cambridge CB2 3EJ, England
2Institut fur Biologie II (Zoologie), RWTH Aachen, University, D-52056 Aachen, Germany
2Institut fur Biologie II (Zoologie), RWTH Aachen, University, D-52056 Aachen, Germany
To understand the catapult mechanism that propels jumping in a planthopper insect, the innervation and action of key muscles were analyzed. The large trochanteral depressor muscle, M133b,c, is innervated by two motor neurons and by two dorsal unpaired median (DUM) neurons, all with axons in N3C. A smaller depressor muscle, M133a, is innervated by two neurons, one with a large-diameter cell body, a large, blind-ending dendrite, and a giant ovoid, axon measuring 50 m by 30 m in nerve N5A. The trochanteral levator muscles (M132) and (M131) are innervated by N4 and N3B, respectively. The actions of these muscles in a restrained jump were divisible into a three-phase pattern. First, both hind legs were moved into a cocked position by high-frequency bursts of spikes in the levator muscles lasting about 0.5 seconds. Second, and once both legs were cocked, M133b,c received a long continuous sequence of motor spikes, but the two levators spiked only sporadically. The spikes in the two motor neurons to M133b,c on one side were closely coupled to each other and to the spikes on the other side. If one hind leg was cocked then the spikes only occurred in motor neurons to that side. The final phase was the jump movement itself, which occurred when the depressor spikes ceased and which lasted 1 ms. Muscles 133b,c activated synchronously on both sides, are responsible for generating the power, and M133a and its giant neuron may play a role in triggering the release of a jump.
J. Comp. Neurol. 518:1349-1369, 2010.
Both synthesis and reuptake are critical for replenishing the releasable serotonin pool in Drosophila
Xenia Borue*,†, Barry Condron‡ and B. Jill Venton jventon@virginia.edu
*Medical Scientist Training Program, University of Virginia, Charlottesville, VA, USA
†Neuroscience Graduate Program, University of Virginia, Charlottesville, VA, USA
‡Department of Biology, University of Virginia, Charlottesville, VA, USA
§Department of Chemistry, University of Virginia, Charlottesville, VA, USA
†Neuroscience Graduate Program, University of Virginia, Charlottesville, VA, USA
‡Department of Biology, University of Virginia, Charlottesville, VA, USA
§Department of Chemistry, University of Virginia, Charlottesville, VA, USA
The two main sources of serotonin available for release are expected to be newly synthesized serotonin and serotonin recycled after reuptake by the serotonin transporter. However, their relative importance for maintaining release and the time course of regulation are unknown. We studied serotonin signaling in the ventral nerve cord of the larval Drosophila CNS. Fast-scan cyclic voltammetry at implanted microelectrodes was used to detect serotonin elicited by channelrhodopsin2-mediated depolarization. The effects of reuptake were probed by incubating in cocaine, which is selective for the serotonin transporter in Drosophila. p-chlorophenylalanine, an inhibitor of tryptophan hydroxylase2, was used to investigate the effects of synthesis. Stimulations were repeated at various intervals to assess the time course of recovery of the releasable pool. Reuptake is important for the rapid replenishment of the releasable pool, on the 1 min time scale. Synthesis is critical to the longer-term replenishment (10 min) of the releasable pool, especially when reuptake is also inhibited. Concurrent synthesis and reuptake inhibition decreased both serotonin tissue content measured by immunohistochemistry (by 50%) and the initial amount of evoked serotonin (by 65%). Decreases in evoked serotonin are rescued by inhibiting action potential propagation with tetrodotoxin, implicating endogenous activity in the depletion. These results show synthesis is necessary to replenish part of the releasable serotonin pool that is depleted after reuptake inhibition, suggesting that regulation of synthesis may modulate the effects of serotonin reuptake inhibitors.
Insect Neuronscience
Diversity and wiring variability of olfactory local interneurons in the Drosophila antennal lobe
Ya-Hui Chou,Maria L Spletter,Emre Yaksi,Jonathan C S Leong,Rachel I Wilson& Liqun Luo lluo@stanford.edu
Howard Hughes Medical Institute, Department of Biology, Stanford University, Stanford, California, USA.
Department of Neurobiology, Harvard Medical School, Boston, Massachusetts, USA.
Local interneurons are essential in information processing by neural circuits. Here we present a comprehensive genetic, anatomical and electrophysiological analysis of local interneurons (LNs) in the Drosophila melanogaster antennal lobe, the first olfactory processing center in the brain. We found LNs to be diverse in their neurotransmitter profiles, connectivity and physiological properties. Analysis of >1,500 individual LNs revealed principal morphological classes characterized by coarsely stereotyped glomerular innervation patterns. Some of these morphological classes showed distinct physiological properties. However, the finer-scale connectivity of an individual LN varied considerably across brains, and there was notable physiological variability within each morphological or genetic class. Finally, LN innervation required interaction with olfactory receptor neurons during development, and some individual variability also likely reflected LN–LN interactions. Our results reveal an unexpected degree of complexity and individual variation in an invertebrate neural circuit, a result that creates challenges for solving the Drosophila connectome.
Nature Neuroscience http://www.nature.com/neuro/journal/v13/n4/abs/nn.2489.html?lang=en
Control of sexual differentiation and behavior by the doublesex gene in Drosophila melanogaster
Faculty of Biomedical and Life Sciences, Integrative and Systems Biology, University of Glasgow, Glasgow, UK.
Department of Physiology, Anatomy and Genetics, University of Oxford, Oxford, UK.
Doublesex proteins, which are part of the structurally and functionally conserved Dmrt gene family, are important for sex determination throughout the animal kingdom. We inserted Gal4 into the doublesex (dsx) locus of Drosophila melanogaster, allowing us to visualize and manipulate cells expressing dsx in various tissues. In the nervous system, we detected differences between the sexes in dsx-positive neuronal numbers, axonal projections and synaptic density. We found that dsx was required for the development of male-specific neurons that coexpressed fruitless (fru), a regulator of male sexual behavior. We propose that dsx and fru act together to form the neuronal framework necessary for male sexual behavior. We found that disrupting dsx neuronal function had profound effects on male sexual behavior. Furthermore, our results suggest that dsx-positive neurons are involved in pre- to post-copulatory female reproductive behaviors.
Nature Neuroscience http://www.nature.com/neuro/journal/v13/n4/abs/nn.2515.html?lang=en
Insect Neuroethology
Neuromechanical simulation of the locust jump
D. Cofer1, G. Cymbalyuk2, W. J. Heitler4 and D. H. Edwards3,*dedwards@gsu.edu
1 Departments of Biology, Georgia State University, Atlanta, GA 30303, USA
2 Physics and Astronomy, Georgia State University, Atlanta, GA 30303, USA
3 Neuroscience Institute, Georgia State University, Atlanta, GA 30303, USA
4 School of Biology, University of St Andrews, St Andrews, Fife, KY16 9TS, UK
2 Physics and Astronomy, Georgia State University, Atlanta, GA 30303, USA
3 Neuroscience Institute, Georgia State University, Atlanta, GA 30303, USA
4 School of Biology, University of St Andrews, St Andrews, Fife, KY16 9TS, UK
The neural circuitry and biomechanics of kicking in locustshave been studied to understand their roles in the control ofboth kicking and jumping. It has been hypothesized that thesame neural circuit and biomechanics governed both behaviorsbut this hypothesis was not testable with current technology.We built a neuromechanical model to test this and to gain abetter understanding of the role of the semi-lunar process (SLP)in jump dynamics. The jumping and kicking behaviors of the modelwere tested by comparing them with a variety of published data,and were found to reproduce the results from live animals. Thisconfirmed that the kick neural circuitry can produce the jumpbehavior. The SLP is a set of highly sclerotized bands of cuticlethat can be bent to store energy for use during kicking andjumping. It has not been possible to directly test the effectsof the SLP on jump performance because it is an integral partof the joint, and attempts to remove its influence prevent thelocust from being able to jump. Simulations demonstrated thatthe SLP can significantly increase jump distance, power, totalenergy and duration of the jump impulse. In addition, the geometryof the joint enables the SLP force to assist leg flexion whenthe leg is flexed, and to assist extension once the leg hasbegun to extend.
Journal of Experimental Biology 213, 1060-1068 (2010)
http://jeb.biologists.org/cgi/content/abstract/213/7/1060
http://jeb.biologists.org/cgi/content/abstract/213/7/1060
Insect Olfaction
Male moths bearing transplanted female antennae express characteristically female behaviour and central neural activity
N. M. Kalberer*, C. E. Reisenman and J. G. Hildebrandnicole.kalberer@unibas.ch
Department of Neuroscience, University of Arizona, 1040 E. Fourth Street, Gould Simpson 611, Tucson, AZ 85721, USA
The primary olfactory centres of the sphinx moth Manduca sexta,the antennal lobes, contain a small number of sexually dimorphicglomeruli: the male-specific macroglomerular complex and thelarge female glomeruli. These glomeruli play important rolesin sex-specific behaviours, such as the location of conspecificfemales and the selection of appropriate host plants for oviposition.The development of sexually dimorphic glomeruli depends strictlyon the ingrowth of sex-specific olfactory receptor cell afferents.In the present study we tested the role of female-specific olfactoryreceptor cells (ORCs) in mediating female-specific host plantapproach behaviour and in determining the response of downstreamantennal lobe neurons. We generated male gynandromorphs by excisingone imaginal disc from a male larva and replacing it with theantennal imaginal disc from a female donor. Most male gynandromorphshad an apparently normal female antenna and a feminised antennallobe. These gynandromorphs were tested for flight responsesin a wind tunnel towards tomato plants, a preferred host plantfor oviposition in M. sexta. Male gynandromorphs landed on hostplants as often as normal females, demonstrating that the presenceof the induced female-specific glomeruli was necessary and sufficientto produce female-like, odour-oriented behaviour, i.e. orientationtowards host plants. We also characterised the physiologicaland morphological properties of antennal lobe neurons of malegynandromorphs. We found that projection neurons with arborisationsin the induced female-specific glomeruli showed physiologicalresponses akin to those of female-specific projection neuronsin normal females. These results therefore indicate that ORCsconfer specific odour tuning to their glomerular targets and,furthermore, instruct odour-specific behaviour.
Journal of Experimental Biology 213, 1272-1280 (2010)
http://jeb.biologists.org/cgi/content/abstract/213/8/1272
http://jeb.biologists.org/cgi/content/abstract/213/8/1272
Insect Physiology
Genotype by temperature interactions in the metabolic rate of the Glanville fritillary butterfly
Kristjan Niitepõldkristjan.niitepold@helsinki.fi
Department of Biological and Environmental Sciences, University of Helsinki, FI-00014, Helsinki, Finland
Metabolic rate is a highly plastic trait. Here I examine factorsthat influence the metabolic rate of the Glanville fritillarybutterfly (Melitaea cinxia) in pupae and resting and flyingadults. Body mass and temperature had consistent positive effectson metabolic rate in pupae and resting adults but not in flyingadults. There was also a consistent nonlinear effect of thetime of the day, which was strongest in pupae and weakest inflying adults. Flight metabolic rate was strongly affected byan interaction between the phosphoglucose isomerase (Pgi) genotypeand temperature. Over a broad range of measurement temperatures,heterozygous individuals at a single nucleotide polymorphism(SNP) in Pgi had higher peak metabolic rate in flight, but athigh temperatures homozygous individuals performed better. Thetwo genotypes did not differ in resting metabolic rate, suggestingthat the heterozygotes do not pay an additional energetic costfor their higher flight capacity. Mass-independent resting andflight metabolic rates were at best weakly correlated at theindividual level, and therefore, unlike in many vertebrates,resting metabolic rate does not serve as a useful surrogateof the metabolic capacity of this butterfly
Journal of Experimental Biology 213, 1042-1048 (2010)
Insect Population ecology
Food stress sensitivity and flight performance across phosphoglucose isomerase enzyme genotypes in the sooty copper butterfly
Isabell Karl1, 2, Klaus Hubert Hoffmann2 and Klaus Fischer1 klaus.fischer@uni-greifswald.de
Zoological Institute and Museum, University of Greifswald, Johann-Sebastian-Bach-Str. 11/12, 17489 Greifswald, Germany
Department of Animal Ecology I, University of Bayreuth, P.O. Box 101 251, 95440 Bayreuth, Germany
Interest in genetic variation at allozyme loci, especially at phosphoglucose isomerase (PGI), has considerably increased over recent decades. In this study, we investigated variation in food stress sensitivity and flight performance, two traits closely linked to individual fitness, across PGI genotypes in the sooty copper butterfly Lycaena tityrus. PGI genotype significantly affected growth rate and pupal mass, but had no overall effect on development time or flight performance. A significant genotype × sex × feeding treatment interaction showed that females from the rarest genotypes showed the strongest increase in development time under food stress. At the same time, these females exhibited the weakest reduction in body mass compared to non food-stressed individuals, while the most common PGI genotypes showed the highest reduction (significant interaction between genotype and feeding treatment). Such results suggest that effects of food stress on pupal mass may not pose a particularly strong selective pressure in L. tityrus. Generally, sex-specific differences in and effects of food stress on life-history traits were as expected, with, e.g., males showing a more rapid development, lower pupal mass and better flight performance than females.
Insect Society
Beyond cuticular hydrocarbons: evidence of proteinaceous secretion specific to termite kings and queens
Robert Hanus1, Vladimír Vrkoslav2,*, Ivan Hrdý1, Josef Cva?ka2 and Jan Šobotník1 vrkoslav@uochb.cas.cz
1Infochemicals Research Team, Institute of Organic Chemistry and Biochemistry, Flemingovo n. 2, 166 10 Praha, Czech Republic
2Mass Spectrometry Research Team, Institute of Organic Chemistry and Biochemistry, Flemingovo n. 2, 166 10 Praha, Czech Republic
In 1959, P. Karlson and M. Lüscher introduced the term ‘pheromone’, broadly used nowadays for various chemicals involved in intraspecific communication. To demonstrate the term, they depicted the situation in termite societies, where king and queen inhibit the reproduction of nest-mates by an unknown chemical substance. Paradoxically, half a century later, neither the source nor the chemical identity of this ‘royal’ pheromone is known. In this study, we report for the first time the secretion of polar compounds of proteinaceous origin by functional reproductives in three termite species, Prorhinotermes simplex, Reticulitermes santonensis and Kalotermes flavicollis. Aqueous washes of functional reproductives contained sex-specific proteinaceous compounds, virtually absent in non-reproducing stages. Moreover, the presence of these compounds was clearly correlated with the age of reproductives and their reproductive status. We discuss the putative function of these substances in termite caste recognition and regulation.
Proc. R. Soc. B 7 April 2010 vol. 277 no. 1684 995-1002
Insect Review
The impacts of metals and metalloids on insect behavior
Department of Entomology, University of California, 900 University Avenue, Riverside, CA 92521, USA
In toxicology studies, the use of death as an endpoint often fails to capture the effects a pollutant has on disruptions of ecosystem services by changing an animal's behavior. Many toxicants can cause population extinctions of insect species at concentrations well below the EC25, EC50, or EC90 concentrations traditionally reported from short-term bioassays. A surprising number of species cannot detect metal and metalloid contamination, and do not always avoid food with significant metal concentrations. This frequently leads to modified ingestion, locomotor, and reproductive behaviors. For example, some species show a tendency to increase locomotor behaviors to escape from locations with elevated metal pollution, whereas other insects greatly decrease all movements unrelated to feeding. Still others exhibit behaviors resulting in increased susceptibility to predation, including a positive phototaxis causing immatures to move to exposed positions. For purposes of reproduction, the inability to avoid even moderately polluted sites when ovipositing can lead to egg loss and reduced fitness of offspring. Ultimately, impaired behaviors result in a general reduction in population sizes and species diversity at contaminated sites, the exceptions being those species tolerating contamination that become dominant. Regardless, ecosystem services, such as herbivory, detritus reduction, or food production for higher trophic levels, are disrupted. This review evaluates the effects of metal and metalloid pollution on insect behaviors in both terrestrial and aquatic systems reported in a diverse literature scattered across many scientific disciplines. Behaviors are grouped by ingestion, taxis, and oviposition. We conclude that understanding how insect behavior is modified is necessary to assess the full scope and importance of metal and metalloid contamination.
Insect Biology
Brood comb as a humidity buffer in honeybee nests
Michael B. Ellis1, Sue W. Nicolson1, Robin M. Crewe1 and Vincent Dietemann1, 2 vincent.dietemann@alp.admin.ch
(1) Department of Zoology and Entomology, University of Pretoria, Pretoria, 0002, South Africa
Adverse environmental conditions can be evaded, tolerated or modified in order for an organism to survive. During their development, some insect larvae spin cocoons which, in addition to protecting their occupants against predators, modify microclimatic conditions, thus facilitating thermoregulation or reducing evaporative water loss. Silk cocoons are spun by honeybee (Apis mellifera) larvae and subsequently incorporated into the cell walls of the wax combs in which they develop. The accumulation of this hygroscopic silk in the thousands of cells used for brood rearing may significantly affect nest homeostasis by buffering humidity fluctuations. This study investigates the extent to which the comb may influence homeostasis by quantifying the hygroscopic capacity of the cocoons spun by honeybee larvae. When comb containing cocoons was placed at high humidity, it absorbed 11% of its own mass in water within 4 days. Newly drawn comb composed of hydrophobic wax and devoid of cocoons absorbed only 3% of its own mass. Therefore, the accumulation of cocoons in the comb may increase brood survivorship by maintaining a high and stable humidity in the cells.
Edited by Xin-Cheng Zhao
2010-04-01
Insect Frontiers Apr 2010 Vol2 No 4 PDF
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