Insect Nervous System Research Articles

Comparison of Sensory Structures Present on Larval Antennae and Mouthparts of Lepidopteran Crop Pests

Lepidopteran crop pests like Spodoptera litura (F.) (Lepidoptera: Noctuidae), Chilo partellus (Swinhoe) (Lepidoptera: Crambidae), Plutella xylostella (L.) (Lepidoptera: Plutellidae), and Maruca vitrata (F.) (Lepidoptera: Pyralidae) are the major constraints for crop production and productivity. They are polyphagous and feed on tobacco, millets, cruciferous crops, and leguminous crops, respectively. Sensory structures and sensory genes are the key players responsible for their preference for particular crop species. Sensory genes code for the chemoreceptors present in the dendritic membrane of the neuron, which interpret the signal perceived by the insect nervous system that is responsible for insect behavior. In this study, we examined the distribution and morphology of sensory structures present on larval antennae and mouthparts of 4 lepidopteran crop pest species using scanning electron microscopy. We found that the mouthparts of lepidopteran larvae all possess sensory structures and organs such as sensilla chaetica, sensilla basiconica, and sensilla styloconica involved in gustatory and olfactory functions. The only difference between species lies in the external appearance, position, distribution, and number of sensory organs. Sensilla chaetica alone were observed on the labrum and mandibles, whereas sensilla styloconica and sensilla chaetica were present on the labium. All 3 types of sensilla were observed on the maxilla of S. litura, C. partellus, P. xylostella, and M. vitrata with varied numbers and morphology. Mainly, sensilla basiconica were present on antennae and apical maxillary palps, which are involved in olfactory and gustatory functions, respectively. In addition, we compared the sensory gene odorant receptor co-receptor (Or83b), which is pivotal in olfactory reception, among the 4 lepidopteran species and found that Or83b is conserved, showing the ancestral relationship among the 4 species.

FluoRender: joint freehand segmentation and visualization for many-channel fluorescence data analysis

BackgroundImage segmentation and registration techniques have enabled biologists to place large amounts of volume data from fluorescence microscopy, morphed three-dimensionally, onto a common spatial frame. Existing tools built on volume visualization pipelines for single channel or red-green-blue (RGB) channels have become inadequate for the new challenges of fluorescence microscopy. For a three-dimensional atlas of the insect nervous system, hundreds of volume channels are rendered simultaneously, whereas fluorescence intensity values from each channel need to be preserved for versatile adjustment and analysis. Although several existing tools have incorporated support of multichannel data using various strategies, the lack of a flexible design has made true many-channel visualization and analysis unavailable. The most common practice for many-channel volume data presentation is still converting and rendering pseudosurfaces, which are inaccurate for both qualitative and quantitative evaluations.ResultsHere, we present an alternative design strategy that accommodates the visualization and analysis of about 100 volume channels, each of which can be interactively adjusted, selected, and segmented using freehand tools. Our multichannel visualization includes a multilevel streaming pipeline plus a triple-buffer compositing technique. Our method also preserves original fluorescence intensity values on graphics hardware, a crucial feature that allows graphics-processing-unit (GPU)-based processing for interactive data analysis, such as freehand segmentation. We have implemented the design strategies as a thorough restructuring of our original tool, FluoRender.ConclusionThe redesign of FluoRender not only maintains the existing multichannel capabilities for a greatly extended number of volume channels, but also enables new analysis functions for many-channel data from emerging biomedical-imaging techniques.

The effect of titanium dioxide nanoparticles and UV irradiation on photocatalytic degradation of Imidaclopride

ABSTRACTImidaclopride is an insecticide widely used for pest control in agriculture around the world. It acts on the central nervous system of insects, while posing lower toxicity to mammals. This is an organic material made of Pyridinium, Dihydroimidazol and Nitramide. This structure poses a threat to the environment and humans. Until now, different types of methods have been used for elimination of this organic pollution. Recently, advanced oxidation processes (AOPs) are presented as a proposed method to remove this organic pollution. Photocatalytic degradation is also used as an efficient method for destruction of organic structures. In this study, the effect of titanium dioxide (TiO2) nanoparticle as a photocatalyst activated by UV irradiation is investigated. The new design of the reactor was prepared with coaxial cylinders in which the inner cylinder is rotated at a constant speed. The reactor worked in two batch and continuous modes. The results show that the UV irradiation is more effective than activated TiO2 nanoparticle, as the designed reactor with UV irradiation eliminated Imidaclopride in less than 2 hours.

Neuroprotection and endocytosis: erythropoietin receptors in insect nervous systems.

Erythropoietin (Epo) plays a dual role as an erythropoiesis-stimulating hormone and a locally produced cytoprotectant in various vertebrate tissues. Splice variants and engineered derivatives of Epo that mediate neuroprotection but do not stimulate erythropoiesis suggest that alternative receptors, different from the 'classical' homodimeric receptor involved in haematopoiesis, mediate neuroprotective Epo functions. Previous studies on grasshoppers demonstrated neuroprotective and neuroregenerative effects of Epo that involved similar transduction pathways as in mammals. To advance the characterization of yet unidentified neuroprotective Epo receptors, we studied the neuroprotective potency of the human non-erythropoietic Epo splice variant EV-3 in primary cultured locust brain neurons. We demonstrate that EV-3, like Epo, protects locust neurons from hypoxia-induced apoptotic death through activation of the Janus kinase/signal transducer and activator of transcription transduction pathway. Using the fluorescent dye FM1-43 to quantify endocytotic activity we show that both Epo and EV-3 increase the number of fluorescently labelled endocytotic vesicles. This reveals that binding of Epo to its neuroprotective receptor induces endocytosis, as it has been described for the mammalian homodimeric Epo-receptor expressed by erythroid progenitors. Reduction in Epo-stimulated endocytotic activity following pre-exposure to EV-3 indicated that both Epo and its splice variant bind to the same receptor on locust neurons. The shared neuroprotective potency of Epo and EV-3 in insect and mammalian neurons, in the absence of erythropoietic effects of EV-3 in mammals, suggests a greater similarity of the unidentified nervous Epo receptors (or receptor complexes) across phyla than between mammalian haematopoietic and neuroprotective receptors. Insects may serve as suitable models to evaluate the specific protective mechanisms mediated by Epo and its variants in non-erythropoietic mammalian tissues.

Space for the Nervous Tissue: Instead of introduction

A university campus is not only a complex of living, education and auxiliary facilities. It is a certain style of life. It is developed to fulfill a certain task: knowledge preservation and generation. The system of preservation and processing of the society’s knowledge has functions similar to the nervous system. The stronger the society’s scientific and academic network is, the more intellectual, advanced, diverse and flexible is the society’s response to extrinsic stimuli. The nervous system of present day states is similar to the nervous system of insects – with ganglions and different sense organs. A university campus is an elaborate complex of “sense organs” (research laboratories) and “ganglions” (theoretic groups, seminars etc.). The nervous tissue is the most delicate and volatile of all tissues in the organism. Under nutritional deficiency, too strong or too light external effects, the nervous system fails. Its signals malfunction, and either neuralgia or anesthesia occurs. If disorders in the nervous system become more serious, they can lead to a complete paralysis. A university campus is to provide comfortable working conditions for scientists – preservers and generators of knowledge. Comfort is a special thing for them. The level of material needs among campus residents is usually not very high. Their food, clothing and housing requirements are rather modest. Certainly, the sense of security is necessary – any violation in the campus is very painful, like touching a naked nerve. But the most important and vital thing in the campus is a constant and intense flow of all kinds of information. The Internet, libraries, scientific conferences, symposiums and forums are necessary to the campus as the breath of life. It makes dying gasps without it. At the same time, all these “adventures of a thought” are outwardly almost undistinguished. Intensively thinking people look lazy and even inert. A true brainwork is not intension of the Thinker by Roden, but relaxation and meditative calm. (Isn’t it the reason why mental workers seem to be idlers in the eyes of administrators?...) In the Late Medieval and Renaissance eras, first universities adopted from monasteries the practice of creating the forms of life comfortable for the society’s “nervous system”. It is difficult to add something crucially new to this millenarian experience. Therefore, modern campuses (or modern elements of old campuses) are built on the same principles as in the 13th century. Cambridge, one of the oldest university complexes in Europe, can serve as a fine example of an effectively organized campus. Its image is less aristocratic and more applicable than the image of its eternal competitor – Oxford. But they are organized almost equally. Their financial and political independence protects them from economical fluctuations and governmental crises, like a skull protects brain from strokes and cold. The campuses’ interior is traditional, comfortable and calm. Their intellectual life is full of intense flows of new knowledge. What is the life like in the Cambridge campus? The article “On the English Land, on Another Planet… Interview with a resident of Cambridge” by Ekaterina Antipina contains an interview from the first person.

Bothriurus bonariensis scorpion venom activates voltage-dependent sodium channels in insect and mammalian nervous systems

Animal venoms have been widely recognized as a major source of biologically active molecules. Bothriurus bonariensis, popularly known as black scorpion, is the arthropod responsible for the highest number of accidents involving scorpion sting in Southern Brazil. Here we reported the first attempt to investigate the neurobiology of B. bonariensis venom (BBV) in the insect and mammalian nervous system. BBV (32 μg/g) induced a slow neuromuscular blockade in the in vivo cockroach nerve-muscle preparations (70 ± 4%, n = 6, p < 0.001), provoking repetitive twitches and significantly decreasing the frequency of spontaneous leg action potentials (SNCAPs) from 82 ± 3 min−1 to 36 ± 1.3 min−1 (n = 6, p < 0.05), without affecting the amplitude. When tested in primary cultures of rat hippocampal cells, BBV induced a massive increase of Ca2+ influx (250 ± 1% peak increase, n = 3, p < 0.0001). The disturbance of calcium homeostasis induced by BBV on the mammalian central nervous system was not accompanied by cellular death and was prevented by the co-treatment of the hippocampal cells with tetrodotoxin, a selective sodium channel blocker. The results suggest that the biological activity of BBV is mostly related to a modulation of sodium channels function. Our biological activity survey suggests that BBV may have a promising insecticidal and therapeutic potential.

Antagonist pharmacology of desensitizing and non-desensitizing nicotinic acetylcholine receptors in cockroach neurons

Two α-bungarotoxin-sensitive nicotinic acetylcholine (ACh) receptor subtypes in neurons of the American cockroach have been identified as desensitizing (nAChD) and selectively inhibitable with 100nM imidacloprid, and non-desensitizing (nAChN) and selectively inhibitable with 100pM methyllycaconitine. In this paper, the single-electrode voltage-clamp technique was used to measure concentration-response relations for the action of ACh and five antagonists on pharmacologically separated nAChD and nAChN receptors of acutely dissociated neurons from thoracic ganglia of the American cockroach. A dual bath and U-tube perfusion system was used to achieve rapid application of ACh in the continued presence of antagonists, which was essential to accurately measure inhibition by rapidly-reversible antagonists. ACh activated both receptors with an EC50 of 7μM and the antagonist potencies were (nAChD/nAChN in nM): dihydro-β-erythroidine: 1.0/5.6, d-tubocurarine: 1000/34, condelphine: 0.39/0.65, phencyclidine: 74/980 and mecamylamine 47/1150. While each of these antagonists displayed some subtype selectivity, none are selective enough to be used as subtype-selective tools. These results bring to a total of 16 the number of nicotinic compounds that have been measured on nAChD and nAChN currents. Characterization of these receptors is important for understanding the role of nAChRs in the insect nervous system and the mechanism of action of insecticides.

In vitro screening for inhibitor of cloned Drosophila melanogaster tyramine-β-hydroxylase and docking studies

Biogenic amines are common biologically active substances extended within the whole animal kingdom where they play vital roles as signal transducer as well as regulator of cell functions. One of these biogenic amines called octopamine (OA) is synthesized from tyramine (TA) by the catalysis of tyramine-β-hydroxylase (TβH) originated in the insect nervous system. Both TA and OA act as neurotransmitters, neurohormones and neuromodulators in the arthropod nervous system. Herein, the inhibitory activity of 1-arylimidazole-2(3H)-thiones (AITs) was tested on cloned Drosophila tyramine-β-hydroxylase (DmTβH) expressed in Bombyx mori strain. Radiolabelled 3H-TA was used to analyze the activity of AITs exhibited inhibitory effects on DmTβH, whose ID50 values range from 0.02 to 2511nM where DmTβH was inhibited in a dose-dependent manner at pH 7.6 and 25°C during a 30min of incubation. To understand the catalytic role of the TβH, a three dimensional structure of the TβH from Drosophila melanogaster was constructed by homology modeling using the Phyre2 web server with 100% confidence. The modeled three-dimensional structure of TβH was used to perform the docking study with AITs. This may give more insights to precise design of inhibitors for TβH to control insect’s population.

Monosaccharide profiling of silkworm (Bombyx mori L.) nervous system during development and aging

Glycoconjugates have various functions in differentiation, development, aging and in all aspects of normal functioning of organisms. The reason for increased research on this topic is that glycoconjugates locate mostly on the cell surface and play crucial biological roles in the nervous system including brain development, synaptic plasticity, learning, and memory. Considering their roles in the nervous system, information about their existence in the insect nervous system is rather sparse. Therefore, in order to detect monosaccharide content of N- and O-glycans, we carried out capLC-ESI-MS/MS analysis to determine the concentration changes of glucose, mannose, galactose, N-acetylglucosamine (GlcNAc), N-acetylgalactosamine (GalNAc), fucose, xylose, arabinose, and ribose monosaccharides in the nervous system of Bombyx mori during development and aging processes. In addition to LC-MS, lectin blotting was done to detect quantitative changes in N- and O-glycans. Developmental stages were selected as 3rd (the youngest sample), 5th (young) larval instar, motionless prepupa (the oldest sample), and pupa (adult development). Derivatization of monosaccharides was performed with a solution of PMP agent and analyzed with capLC-ESI-MS/MS. For lectin blotting, determination of glycan types was carried out with Galanthus nivalis agglutinin and Peanut agglutinin lectins. In all stages, the most abundant monosaccharide was glucose. Although all monosaccharides were present most abundantly in the youngest stage (3rd instar), they are generally reduced gradually during the aging process. It was observed that amounts of monosaccharides increased again in the pupa stage. According to lectin blotting, N- and O-linked glycoproteins expressions were different and there were some specific glycoprotein expression differences between stages. These findings suggest that the glycosylation state of proteins in the nervous system changes during development and aging in insects in a similar fashion to that reported for vertebrates.

Sucrose Sensitivity of Honey Bees Is Differently Affected by Dietary Protein and a Neonicotinoid Pesticide.

Over a decade, declines in honey bee colonies have raised worldwide concerns. Several potentially contributing factors have been investigated, e.g. parasites, diseases, and pesticides. Neonicotinoid pesticides have received much attention due to their intensive use in crop protection, and their adverse effects on many levels of honey bee physiology led the European Union to ban these compounds. Due to their neuronal target, a receptor expressed throughout the insect nervous system, studies have focused mainly on neuroscience and behaviour. Through the Geometric Framework of nutrition, we investigated effects of the neonicotinoid thiamethoxam on survival, food consumption and sucrose sensitivity of honey bees (Apis mellifera). Thiamethoxam did not affect protein and carbohydrate intake, but decreased responses to high concentrations of sucrose. Interestingly, when bees ate fixed unbalanced diets, dietary protein facilitated better sucrose detection. Both thiamethoxam and dietary protein influenced survival. These findings suggest that, in the presence of a pesticide and unbalanced food, honey bee health may be severely challenged. Consequences for foraging efficiency and colony activity, cornerstones of honey bee health, are also discussed.

Molecular characterization and expression profiles of nicotinic acetylcholine receptors in the rice striped stem borer, Chilo suppressalis (Lepidoptera: Crambidae).

Nicotinic acetylcholine receptors (nAChRs) are members of the cys-loop ligand-gated ion channel (cysLGIC) superfamily, mediating fast synaptic cholinergic transmission in the central nervous system in insects. Insect nAChRs are the molecular targets of economically important insecticides, such as neonicotinoids and spinosad. Identification and characterization of the nAChR gene family in the rice striped stem borer, Chilo suppressalis, could provide beneficial information about this important receptor gene family and contribute to the investigation of the molecular modes of insecticide action and resistance for current and future chemical control strategies. We searched our C. suppressalis transcriptome database using Bombyx mori nAChR sequences in local BLAST searches and obtained the putative nAChR subunit complementary DNAs (cDNAs) via reverse transcription polymerase chain reaction (RT-PCR) and rapid amplification of cDNA ends methods. Similar to B. mori, C. suppressalis possesses 12 nAChR subunits, including nine α-type and three β-type subunits. Quantitative RT-PCR analysis revealed the expression profiles of the nAChR subunits in various tissues, including the brain, subesophageal ganglion, thoracic ganglion, abdominal ganglion, hemocytes, fat body, foregut, midgut, hindgut and Malpighian tubules. Developmental expression analyses showed clear differential expression of nAChR subunits throughout the C. suppressalis life cycle. The identification of nAChR subunits in this study will provide a foundation for investigating the diverse roles played by nAChRs in C. suppressalis and for exploring specific target sites for chemicals that control agricultural pests while sparing beneficial species.

A CRISPR/Cas9 mediated point mutation in the alpha 6 subunit of the nicotinic acetylcholine receptor confers resistance to spinosad in Drosophila melanogaster

Spinosad, a widely used and economically important insecticide, targets the nicotinic acetylcholine receptor (nAChRs) of the insect nervous system. Several studies have associated loss of function mutations in the insect nAChR α6 subunit with resistance to spinosad, and in the process identified this particular subunit as the specific target site. More recently a single non-synonymous point mutation, that does not result in loss of function, was identified in spinosad resistant strains of three insect species that results in an amino acid substitution (G275E) of the nAChR α6 subunit. The causal role of this mutation has been called into question as, to date, functional evidence proving its involvement in resistance has been limited to the study of vertebrate receptors. Here we use the CRISPR/Cas9 gene editing platform to introduce the G275E mutation into the nAChR α6 subunit of Drosophila melanogaster. Reverse transcriptase-PCR and sequencing confirmed the presence of the mutation in Dα6 transcripts of mutant flies and verified that it does not disrupt the normal splicing of the two exons in close vicinity to the mutation site. A marked decrease in sensitivity to spinosad (66-fold) was observed in flies with the mutation compared to flies of the same genetic background minus the mutation, clearly demonstrating the functional role of this amino acid substitution in resistance to spinosad. Although the resistance levels observed are 4.7-fold lower than exhibited by a fly strain with a null mutation of Dα6, they are nevertheless predicated to be sufficient to result in resistance to spinosad at recommended field rates. Reciprocal crossings with susceptible fly strains followed by spinosad bioassays revealed G275E is inherited as an incompletely recessive trait, thus resembling the mode of inheritance described for this mutation in the western flower thrips, Frankliniella occidentalis. This study both resolves a debate on the functional significance of a target-site mutation and provides an example of how recent advances in genome editing can be harnessed to study insecticide resistance.

High-resolution Quantification of Odor-guided Behavior in Drosophila melanogaster Using the Flywalk Paradigm.

In their natural environment, insects such as the vinegar fly Drosophila melanogaster are bombarded with a huge amount of chemically distinct odorants. To complicate matters even further, the odors detected by the insect nervous system usually are not single compounds but mixtures whose composition and concentration ratios vary. This leads to an almost infinite amount of different olfactory stimuli which have to be evaluated by the nervous system. To understand which aspects of an odor stimulus determine its evaluation by the fly, it is therefore desirable to efficiently examine odor-guided behavior towards many odorants and odor mixtures. To directly correlate behavior to neuronal activity, behavior should be quantified in a comparable time frame and under identical stimulus conditions as in neurophysiological experiments. However, many currently used olfactory bioassays in Drosophila neuroethology are rather specialized either towards efficiency or towards resolution. Flywalk, an automated odor delivery and tracking system, bridges the gap between efficiency and resolution. It allows the determination of exactly when an odor packet stimulated a freely walking fly, and to determine the animal´s dynamic behavioral reaction.

Ivermectin modulation of pH-sensitive chloride channels in the silkworm larvae of Bombyx mori

The pH-sensitive chloride channels (pHCls) are expressed widely in the insect nervous system, but their physiological roles and pesticide sensitivity in Lepidoptera are poorly understood. Here, cDNAs of pHCl variants “A” and “B” were isolated from the head of silkworm (Bombyx mori) larvae and expressed in Xenopus laevis oocytes to characterize their functions and examine their pesticide sensitivity. Variant “A” possesses four entire transmembrane domains (TMs), while variant “B” lacks a part of the TM and the TM3–TM4 linker. Only the A variant formed a chloride channel in oocytes which was activated in response to an increase of pH in the extracellular solution. Neither fipronil nor γ-benzenehexachloride had a significant blocking effect on the A variant when tested at 10μM. By contrast, macrolide ivermectin activated it at acidic pH but blocked it at pH7.6 at concentrations higher than 300nM, indicating a likely contribution to in vivo toxicity.

Selective actions of Lynx proteins on different nicotinic acetylcholine receptors in the locust, Locusta migratoria manilensis.

Nicotinic acetylcholine receptors (nAChRs) are major neurotransmitter receptors and targets of neonicotinoid insecticides in the insect nervous system. The full function of nAChRs is often dependent on associated proteins, such as chaperones, regulators and modulators. Here, three Lynx (Ly-6/neurotoxin) proteins, Loc-lynx1, Loc-lynx2 and Loc-lynx3, were identified in the locust, Locusta migratoria manilensis. Co-expression with Lynx resulted in a dramatic increase in agonist-evoked macroscopic currents on nAChRs Locα1/β2 and Locα2/β2 in Xenopus oocytes, but no changes in agonist sensitivity. Loc-lynx1 and Loc-lynx3 only modulated nAChRs Locα1/β2 while Loc-lynx2 modulated Locα2/β2 specifically. Meanwhile, Loc-lynx1 induced a more significant increase in currents evoked by imidacloprid and epibatidine than Loc-lynx3, and the effects of Loc-lynx1 on imidacloprid and epibatidine were significantly higher than those on acetylcholine. Among three lynx proteins, only Loc-lynx1 significantly increased [(3) H]epibatidine binding on Locα1/β2. The results indicated that Loc-lynx1 had different modulation patterns in nAChRs compared to Loc-lynx2 and Loc-lynx3. Taken together, these findings indicated that three Lynx proteins were nAChR modulators and had selective activities in different nAChRs. Lynx proteins might display their selectivities from three aspects: nAChR subtypes, various agonists and different modulation patterns. Insect Lynx (Ly-6/neurotoxin) proteins act as the allosteric modulators on insect nicotinic acetylcholine receptors (nAChRs), the important targets of insecticides. We found that insect lynx proteins showed their selectivities from at least three aspects: nAChR subtypes, various agonists and different modulation patterns.

A multilevel multimodal circuit enhances action selection in Drosophila

Natural events present multiple types of sensory cues, each detected by a specialized sensory modality. Combining information from several modalities is essential for the selection of appropriate actions. Key to understanding multimodal computations is determining the structural patterns of multimodal convergence and how these patterns contribute to behaviour. Modalities could converge early, late or at multiple levels in the sensory processing hierarchy. Here we show that combining mechanosensory and nociceptive cues synergistically enhances the selection of the fastest mode of escape locomotion in Drosophila larvae. In an electron microscopy volume that spans the entire insect nervous system, we reconstructed the multisensory circuit supporting the synergy, spanning multiple levels of the sensory processing hierarchy. The wiring diagram revealed a complex multilevel multimodal convergence architecture. Using behavioural and physiological studies, we identified functionally connected circuit nodes that trigger the fastest locomotor mode, and others that facilitate it, and we provide evidence that multiple levels of multimodal integration contribute to escape mode selection. We propose that the multilevel multimodal convergence architecture may be a general feature of multisensory circuits enabling complex input-output functions and selective tuning to ecologically relevant combinations of cues.

Odourant dominance in olfactory mixture processing: what makes a strong odourant?

The question of how animals process stimulus mixtures remains controversial as opposing views propose that mixtures are processed analytically, as the sum of their elements, or holistically, as unique entities different from their elements. Overshadowing is a widespread phenomenon that can help decide between these alternatives. In overshadowing, an individual trained with a binary mixture learns one element better at the expense of the other. Although element salience (learning success) has been suggested as a main explanation for overshadowing, the mechanisms underlying this phenomenon remain unclear. We studied olfactory overshadowing in honeybees to uncover the mechanisms underlying olfactory-mixture processing. We provide, to our knowledge, the most comprehensive dataset on overshadowing to date based on 90 experimental groups involving more than 2700 bees trained either with six odourants or with their resulting 15 binary mixtures. We found that bees process olfactory mixtures analytically and that salience alone cannot predict overshadowing. After normalizing learning success, we found that an unexpected feature, the generalization profile of an odourant, was determinant for overshadowing. Odourants that induced less generalization enhanced their distinctiveness and became dominant in the mixture. Our study thus uncovers features that determine odourant dominance within olfactory mixtures and allows the referring of this phenomenon to differences in neural activity both at the receptor and the central level in the insect nervous system.

Neuroscience: Dragonflies predict and plan their hunts.

An analysis reveals that the dragonfly's impressive ability to catch its prey arises from internal calculations about its own movements and those of its target — the first example of such predictions in invertebrates. See Article p.333 Primates and other vertebrates use internal models to control and predict the consequences of their movements, but invertebrates were thought to rely mostly on reflexes. In a study using motion capture to track the head and body movements of dragonflies catching flying prey, Anthony Leonardo and colleagues demonstrate a complexity of behaviour not previously seen in an insect. Approaching from below, the dragonfly's head locks onto its target while its body manoeuvres to align to the prey's flight path and reduce the distance to the prey. Rather than generating these steering movements reactively, by responding only to changes in prey motion, dragonflies using both reactive and predictive control. These predictions account for the motion of the prey and the dragonfly's own body, and are consistent with generation by internal models. The experimental accessibility of the insect nervous system, combined with the load-carrying capacity of the dragonfly, opens these general principles of motor control to detailed mechanistic dissection.

Modulation of dopaminergic neurotransmission induced by sublethal Doses of the organophosphate trichlorfon in cockroaches

Organophosphate (OP) insecticides have been used indiscriminately, based on their high dissipation rates and low residual levels in the environment. Despite the toxicity of OPs to beneficial insects is principally devoted to the acetylcholinesterase (AChE) inhibition, the physiological mechanisms underlying this activity remain poorly understood. Here we showed the pharmacological pathways that might be involved in severe alterations in the insect locomotion and grooming behaviors following sublethal administration of the OP Trichlorfon (Tn) (0.25, 0.5 and 1µM) in Phoetalia pallida. Tn inhibited the acetylcholinesterase activity (46±6, 38±3 and 24±6nmol NADPH/min/mg protein, n=3, p<0.05), respectively. Tn (1µM) also increased the walking maintenance of animals (46±5s; n=27; p<0.05). Tn caused a high increase in the time spent for this behavior (344±18s/30min, 388±18s/30min and 228±12s/30min, n=29–30, p<0.05, respectively). The previous treatment of the animals with different cholinergic modulators showed that pirenzepine>atropine>oxotremorine>d-tubocurarine>tropicamide>methoctramine induced a decrease on Tn (0.5µM)-induced grooming increase, respectively in order of potency. Metoclopramide (0.4µM), a DA-D2 selective inhibitor decreased the Tn-induced grooming activity (158±12s/30min; n=29; p<0.05). Nevertheless, the effect of the selective DA-D1 receptor blocker SCH 23390 (1.85µM) on the Tn (0.5µM)-induced grooming increase was significative and more intense than that of metoclopramide (54±6s/30min; n=30; p<0.05). Taken together the results suggest that a cross-talking between cholinergic M1/M3 and dopaminergic D1 receptors at the insect nervous system may play a role in the OP-mediated behavioral alterations.

Octopamine-like immunoreactive neurons in the brain and subesophageal ganglion of the parasitic wasps Nasonia vitripennis and N. giraulti.

Octopamine is an important neuromodulator in the insect nervous system, influencing memory formation, sensory perception and motor control. In this study, we compare the distribution of octopamine-like immunoreactive neurons in two parasitic wasp species of the Nasonia genus, N. vitripennis and N. giraulti. These two species were previously described as differing in their learning and memory formation, which raised the question as to whether morphological differences in octopaminergic neurons underpinned these variations. Immunohistochemistry in combination with confocal laser scanning microscopy was used to reveal and compare the somata and major projections of the octopaminergic neurons in these wasps. The brains of both species showed similar staining patterns, with six different neuron clusters being identified in the brain and five different clusters in the subesophageal ganglion. Of those clusters found in the subesophageal ganglion, three contained unpaired neurons, whereas the other three consisted in paired neurons. The overall pattern of octopaminergic neurons in both species was similar, with no differences in the numbers or projections of the ventral unpaired median (VUM) neurons, which are known to be involved in memory formation in insects. In one other cluster in the brain, located in-between the optic lobe and the antennal lobe, we detected more neurons in N. vitripennis compared with N. giraulti. Combining our results with findings made previously in other Hymenopteran species, we discuss possible functions and some of the ultimate factors influencing the evolution of the octopaminergic system in the insect brain.