Olfactory control of insect behavior : neurobiological exploration of the moth's nervous system (original) (raw)
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Selectivity of odorant receptors in insects
Frontiers in Cellular Neuroscience, 2012
Insect olfactory receptors (ORs) detect chemicals, shape neuronal physiology, and regulate behavior. Although ORs have been categorized as "generalists" and "specialists" based on their ligand spectrum, both electrophysiological studies and recent pharmacological investigations show that ORs specifically recognize non-pheromonal compounds, and that our understanding of odorant-selectivity mirrors our knowledge of insect chemical ecology. As we are progressively becoming aware that ORs are activated through a variety of mechanisms, the molecular basis of odorant-selectivity and the corollary notion of broad-tuning need to be re-examined from a pharmacological and evolutionary perspective.
Frontiers in Physiology, 2016
Harmful insects include pests of crops and storage goods, and vectors of human and animal diseases. Throughout their history, humans have been fighting them using diverse methods. The fairly recent development of synthetic chemical insecticides promised efficient crop and health protection at a relatively low cost. However, the negative effects of those insecticides on human health and the environment, as well as the development of insect resistance, have been fueling the search for alternative control tools. New and promising alternative methods to fight harmful insects include the manipulation of their behavior using synthetic versions of "semiochemicals", which are natural volatile and non-volatile substances involved in the intra-and/or inter-specific communication between organisms. Synthetic semiochemicals can be used as trap baits to monitor the presence of insects, so that insecticide spraying can be planned rationally (i.e., only when and where insects are actually present). Other methods that use semiochemicals include insect annihilation by mass trapping, attract-and-kill techniques, behavioral disruption, and the use of repellents. In the last decades many investigations focused on the neural bases of insect's responses to semiochemicals. Those studies help understand how the olfactory system detects and processes information about odors, which could lead to the design of efficient control tools, including odor baits, repellents or ways to confound insects. Here we review our current knowledge about the neural mechanisms controlling olfactory responses to semiochemicals in harmful insects. We also discuss how this neuroethology approach can be used to design or improve pest/vector management strategies.
Plasticity and modulation of olfactory circuits in insects
Cell and Tissue Research, 2020
Olfactory circuits change structurally and physiologically during development and adult life. This allows insects to respond to olfactory cues in an appropriate and adaptive way according to their physiological and behavioral state, and to adapt to their specific abiotic and biotic natural environment. We highlight here findings on olfactory plasticity and modulation in various model and non-model insects with an emphasis on moths and social Hymenoptera. Different categories of plasticity occur in the olfactory systems of insects. One type relates to the reproductive or feeding state, as well as to adult age. Another type of plasticity is context-dependent and includes influences of the immediate sensory and abiotic environment, but also environmental conditions during postembryonic development, periods of adult behavioral maturation, and short- and long-term sensory experience. Finally, plasticity in olfactory circuits is linked to associative learning and memory formation. The vas...
The narrowing olfactory landscape of insect odorant receptors
Frontiers in Ecology and Evolution, 2015
The molecular basis of odorant detection and its corollary, the task of the odorant receptor, are fundamental to understanding olfactory coding and sensory ecology. Based on their molecular receptive range, olfactory receptors have been classified as pheromone and non-pheromone receptors, which are respectively activated by a single pheromone component ("specialist") or by multiple odorant ligands ("generalist"). This functional distinction is unique among ligand-gated ion channels and has shaped how we model olfactory coding both at the peripheral and central levels. Here, we revisit the long-standing combinatorial theory of olfaction and argue, based on physiological, pharmacological, evolutionary, and experimental grounds that the task of the odorant receptor is not different from that of neurotransmitter receptors localized in neuronal synapses.
Current views on the function and evolution of olfactory receptors in Lepidoptera
The sense of olfaction stimulates many vital behaviors in insects. At the molecular level, the interactions between an insect and its olfactory environment are mediated by two families of chemosensory receptors, the olfactory receptors and the ionotropic receptors. In this chapter, we review the current knowledge on olfactory receptors within the Lepidoptera. We expose the different strategies used for their identification, via genome and transcriptome sequencing, and describe the principles underpinning the different in vitro and in vivo assays developed for their functional characterization. While hundreds of sequences have been annotated as olfactory receptors, only a small number have been deorphanized and most of these are pheromone receptors. So far the data suggest a combinatorial model of odor coding as revealed in Drosophila. From an evolutionary point of view, several highly conserved clades of olfactory receptors can be defined within Lepidoptera, representing ancestral paralogous lineages, with functional divergence observed within some lineages. In the near future, we expect the characterization of large repertoires of Lepidoptera olfactory receptors, which will shed new light on how evolution has tuned olfaction in different species according to their individual needs and niches. Fig.1 Schemes of the olfactory system of an insect, from the morphological to the molecular level. A: Scheme of a Drosophila. Antennae are in red. B: Scheme of a Drosophila antenna, covered with olfactory sensilla (s, in red). C: Scheme of a basiconic sensillum. This cuticular outgrowth is filled with the sensillar lymph (in light blue) and drilled with pores. Underneath the sensillum cuticle (C, in deep blue), accessory cells (AC) are in green and olfactory receptor neurons (ORN) are in red. Upon activation by odorants, ORNs produce action potentials (AP, in black) which follow the axon to higher structures of the central nervous system of the insect. D: Scheme of the olfactory centers in the central nervous system of a Drosophila. An axon from an ORN is on the left (red arrow) and innervates an antennal lobe (AL, in red). Projection neurons in the AL innervate the mushroom bodies (MB, in blue) and the lateral horns of the protocerebron (LH, in green). E: Scheme of the molecular mechanisms of odorant reception. Once in the sensillar lymph, odorant molecules (in orange) are transported via odorant-binding proteins (OBP, in brown).
Electrophysiological Measurements from a Moth Olfactory System
Journal of Visualized Experiments, 2011
Insect olfactory systems provide unique opportunities for recording odorant-induced responses in the forms of electroantennograms (EAG) and single sensillum recordings (SSR), which are summed responses from all odorant receptor neurons (ORNs) located on the antenna and from those housed in individual sensilla, respectively. These approaches have been exploited for getting a better understanding of insect chemical communication. The identified stimuli can then be used as either attractants or repellents in management strategies for insect pests.
Molecular biology of insect olfaction:recent progress and conceptual models
Journal of Comparative Physiology A, 2005
Insects have an enormous impact on global public health as disease vectors and as agricultural enablers as well as pests and olfaction is an important sensory input to their behavior. As such it is of great value to understand the interplay of the molecular components of the olfactory system which, in addition to fostering a better understanding of insect neurobiology, may ultimately aid in devising novel intervention strategies to reduce disease transmission or crop damage. Since the first discovery of odorant receptors in vertebrates over a decade ago, much of our view on how the insect olfactory system might work has been derived from observations made in vertebrates and other invertebrates, such as lobsters or nematodes. Together with the advantages of a wide range of genetic tools, the identification of the first insect odorant receptors in Drosophila melanogaster in 1999 paved the way for rapid progress in unraveling the question of how olfactory signal transduction and processing occurs in the fruitfly. This review intends to summarize much of this progress and to point out some areas where advances can be expected in the near future.