Biomedical subjects

Bill S Hansson

Publications and source records attributed to Bill S Hansson.

At least 19 recordsLinked to original sources

PubMed2026

A predator-derived odor specifically triggers avoidance in gregarious mated female Locusta migratoria.

BACKGROUND: Insects possess a highly specialized olfactory system. The migratory locust (Locusta migratoria), a major agricultural pest, is thought to emit odors that serve as aposematic signals to protect gregarious individuals from predation. However, whether locusts can detect the odors of their natural enemies to preemptively avoid predation remains unclear. RESULTS: Here, we show that gregarious mated female locusts exhibit strong avoidance behavior toward the odors of two avian predators, Numida meleagris and Anas platyrhynchos. Through volatile compound profiling, we identified 1-octen-3-ol, a key predator-released odor, which elicited significant aversive responses specifically in gregarious mated females; notably, virgin females showed no behavioral response to this odor. Through screening 82 olfactory receptors in L. migratoria, we identified two receptors, LmOR1 and LmOR17, that detect 1-octen-3-ol. A temporal expression study of LmOR1 and LmOR17 across different developmental stages of two locust phases using quantitative real-time polymerase chain reaction (qRT-PCR) showed that both genes are significantly more highly expressed in the gregarious mated females. Genome editing of these receptors revealed that knockout of LmOR1 significantly reduced both the electrophysiological response and the behavioral avoidance of 1-octen-3-ol, whereas knockout of LmOR17 had no effect. In our results we thus uncover a striking mating-state dependence of an innate avoidance behavior to a predator-derived odor, and further we identify LmOR1 as the major receptor mediating this olfactory-driven defense. CONCLUSION: Our findings provide crucial insights into the behavioral and olfactory mechanisms underlying insect-predator interactions, as well as the role of mating status in modulating defensive responses, offering potential olfactory targets for locust management. © 2026 Society of Chemical Industry.

Animals↗

PubMed2006

Olfactory shifts parallel superspecialism for toxic fruit in Drosophila melanogaster sibling, D. sechellia.

Olfaction in the fruit fly Drosophila melanogaster is increasingly understood, from ligand-receptor-neuron combinations to their axonal projection patterns into the antennal lobe . Drosophila thus offers an excellent opportunity to study the evolutionary and ecological dynamics of olfactory systems. We compared the structure and function of the generalist D. melanogaster with that of specialist D. sechellia, which oviposits exclusively on morinda fruit . Our analyses show that whereas the fruit's headspace was dominated by acids, antennae responded most strongly to hexanoates. D. sechellia exhibited an extraordinarily strong response to methyl hexanoate (MeHex). Behaviorally, D. sechellia was much more attracted to these morinda fruit volatiles than was D. melanogaster. The high sensitivity to MeHex was paralleled by a 2.5x-3 x overrepresentation of MeHex neurons on the antenna and a concordant 2.9 x increase in volume of the corresponding glomerulus as compared to D. melanogaster. In addition, the MeHex neuron exhibited an extreme sensitivity down to femtograms of its ligand. In contrast, no peripherally mediated shift was found paralleling D. sechellia's increased attraction to acids. These findings are a demonstration of evolution acting at several levels in the olfactory circuitry in mediating a fruit fly's unique preference for fruit toxic to its sibling species .

Adaptation, Physiological↗

PubMed2006

Unusual response characteristics of pheromone-specific olfactory receptor neurons in the Asian corn borer moth, Ostrinia furnacalis.

Male moth pheromone-detecting receptor neurons are known to be highly specific and very sensitive. We investigated physiological and behavioral responses to female sex pheromone components in male Ostrinia furnacalis moths (Lepidoptera: Crambidae). Using recordings from a cut-sensillum technique, trichoid sensilla could be grouped into four physiological types (1-4), according to the response of receptor neurons to the two major pheromone components, (E)-12- and (Z)-12-tetradecenyl acetate (E12- and Z12-14:OAc). These types could subsequently be characterized as four subtypes (A-D) depending on neural responses to pheromone components from various sister species of O. furnacalis, (Z)-9-, (E)-11- and (Z)-11-tetradecenyl acetate. The peripheral pheromone detection system of O. furnacalis is different to that of other moths. A large majority of the neurons investigated responded to both of the two principal pheromone components. Dose-response and cross-adaptation studies showed that olfactory receptor neurons with large amplitude action potentials responded equally well to E12- and Z12-14:OAc in sensillum types 1-3. Field experiments showed that O. furnacalis males are sensitive to ratios of E12- and Z12-14:OAc and that (Z)-9-tetradecenyl acetate acts as a behavioral antagonist. O. furnacalis males thus display an unusual coding system for odors involved in sexual communication, mainly built on less specific neurons, but still have the ability to detect and respond to the correct female blend. We hypothesize that the pheromone detection system of O. furnacalis consists of two parts, where one is devoted to high sensitivity to Delta12 isomers of tetradecenyl acetate, E12- and Z12-14:OAc and the other to highly specific responses to the E12- or Z12-14:OAc. The unusual feature is thus that a large part of the system is devoted to sensitivity and only a minor part to selectivity. This could be explained by the fact that no other moth species are known to use E12- and/or Z12-14:OAc and that no strong selective pressure to increase selectivity between the isomers has been determined.

Action Potentials↗

PubMed2005

Neuronal architecture of the mosquito deutocerebrum.

Mosquito behavior is heavily dependent on olfactory and mechanosensory cues, which are detected by receptor neurons on the antenna and on the palps. Recent progress in mosquito sensory genomics highlights the need for an up-to-date understanding of the neural architecture of the mosquito brain. Here we present a detailed description of the neural structure of the primary target of the majority of these neurons, the deutocerebrum, in the African malaria (Anopheles gambiae) and yellow fever (Aedes aegypti) mosquitoes. Special focus is made on the olfactory system, the antennal lobe (AL), where we present high-resolution three-dimensional models of the ALs of male and female Ae. aegypti. These models reveal a sexual dimorphism in the number of glomeruli, 49 and 50 glomeruli in male and female mosquitoes, respectively, and in the size of several of the identified glomeruli. The fine structure of receptor neuron terminations in the AL and the rest of the deutocerebrum is described, as are the arborizations of intrinsic deutocerebral neurons and neurons providing output to higher brain areas. In the AL a specific and very large center receiving input from the mechanosensory Johnston's organ is revealed as a multilobed structure receiving peripheral input according to a somatotopic pattern. Within the antennal nerve a specific neuropil containing early, bouton-like ramifications of receptor neurons is described. Within the glomerular array of the AL, neurons providing a possible feedback circuit to antennal receptor neurons are shown. With these results we provide a new resolution in mosquito deutocerebral architecture.

Aedes↗

PubMed2005

Antennal lobe projection destinations of Helicoverpa zea male olfactory receptor neurons responsive to heliothine sex pheromone components.

We used single sensillum recordings to define male Helicoverpa zea olfactory receptor neuron physiology followed by cobalt staining to trace the axons to destination glomeruli of the antennal lobe. Receptor neurons in type A sensilla that respond to the major pheromone component, (Z)-11-hexadecenal, projected axons to the cumulus of the macroglomerular complex (MGC). In approximately 40% of these sensilla a second receptor neuron was stained that projected consistently to a specific glomerulus residing in a previously unrecognized glomerular complex with six other glomeruli stationed immediately posterior to the MGC. Cobalt staining corroborated by calcium imaging showed that receptor neurons in type C sensilla sensitive to (Z)-9-hexadecenal projected to the dorsomedial posterior glomerulus of the MGC, whereas the co-compartmentalized antagonist-sensitive neurons projected to the dorsomedial anterior glomerulus. We also discovered that the olfactory receptor neurons in type B sensilla exhibit the same axonal projections as those in type C sensilla. Thus, it seems that type B sensilla are anatomically type C with regard to the projection destinations of the two receptor neurons, but physiologically one of the receptor neurons is now unresponsive to everything except (Z)-9-tetradecenal, and the other responds to none of the pheromone-related odorants tested.

Action Potentials↗

PubMed2005

Projection patterns of gustatory neurons in the suboesophageal ganglion and tritocerebrum of mosquitoes.

Mosquitoes are heavily dependent on gustatory information when feeding. Following the recent elucidation of the molecular basis of gustation in the malaria mosquito, we present a detailed study of primary central projections of gustatory receptor neurons into the brain in the malaria (Anopheles gambiae) and yellow fever (Aedes aegypti) mosquito. In the brain we provide a detailed map of the areas targeted and describe a number of intrinsic neural elements connecting primary taste areas to higher brain levels. The morphological features described are discussed and compared to earlier reports in other insects as, e.g., the fruitfly, Drosophila.

Animals↗

PubMed2005

Organization of Kenyon cells in subdivisions of the mushroom bodies of a lepidopteran insect.

The mushroom bodies are paired structures in the insect brain involved in complex functions such as memory formation, sensory integration, and context recognition. In many insects these centers are elaborate, sometimes comprising several hundred thousand neurons. The present account describes the mushroom bodies of Spodoptera littoralis, a moth extensively used for studies of olfactory processing and conditioning. The mushroom bodies of Spodoptera consist of only about 4,000 large-diameter Kenyon cells. However, these neurons are recognizably similar to morphological classes of Kenyon cells identified in honey bees, Drosophila, and cockroaches. The spodopteran mushroom body is equipped with three major divisions of its vertical and medial lobe, one of which, the gamma lobe, is supplied by clawed class II Kenyon cells as in other described taxa. Of special interest is the presence of a discrete tract (the Y tract) of axons leading from the calyx, separate from the pedunculus, that innervates lobelets above and beneath the medial lobe, close to the latter's origin from the pedunculus. This tract is comparable to tracts and resultant lobelets identified in cockroaches and termites. The article discusses possible functional roles of the spodopteran mushroom body against the background of olfactory behaviors described from this taxon and discusses the possible functional relevance of mushroom body structure, emphasizing similarities and dissimilarities with mushroom bodies of other species, in particular the fruit fly, Drosophila melanogaster.

Animals↗

PubMed2005

Responses to sex pheromone and plant odours by olfactory receptor neurons housed in sensilla auricillica of the codling moth, Cydia pomonella (Lepidoptera: Tortricidae).

Antennal olfactory receptor neurons located in a limited number of two types of sensilla auricillica, the rabbit-eared shoehorn and the regular shoehorn, located on the 5-30 flagellomere of the codling moth, Cydia pomonella, antenna were screened for selectivity to 11 plant compounds, the major sex pheromone component, three minor pheromone components and one behavioural antagonist. Both types of sensilla housed at least three neurons characterised by different action potential amplitudes. Neurons in both males and females responded to the plant compounds, ethyl (E,Z)-2,4-decadienoate, (+/-)-linalool, (E)-ss-farnesene, hexanol, (Z)-3-hexenyl acetate, 4,8-dimethyl-1,3,(E)7-nonatriene, nonanol, the major pheromone component codlemone [(E,E)-8,10-dodecadienol] and the minor pheromone component tetradecanol. Additionally, (E,E)-alpha-farnesene and (Z)-3-hexenol elicited responses specifically in female neurons, whereas (E,E)-farnesol elicited a specific response in a male neuron. Neurons responded to 1-3 odorants, with sometimes overlapping response spectra. A scanning electron microscopic study of the antennae of both sexes supported an earlier study, apart from that long s. trichodea were present in a wreath at the proximal margin of the flagellomere and in addition evenly distributed over the remaining surface, and a previously non-described sensillum type with external basiconic features was revealed, distributed on the proximal and medial region of the flagellomeres.

Action Potentials↗

PubMed2005

Interactions of mechanical stimuli and sex pheromone information in antennal lobe neurons of a male moth, Spodoptera littoralis.

Male moths respond to sex pheromone sources with up-wind flight behaviour. Localization of the odour source requires not only detection of the olfactory stimulus, but also other sensory input regarding, e.g. visual and mechanical stimuli. Thus, integration of different types of sensory input is necessary. It is, however, not known where in the central nervous system the integration of information regarding different sensory modalities takes place. Using intracellular recording and staining techniques, we investigated neurons in the antennal lobe of Spodoptera littoralis, during stimulation with a mechanical stimulus and a sex pheromone. Fifteen percent of all the neurons investigated responded to the mechanical stimulus and the majority of these neurons showed altered responses if the olfactory stimulus was added. A receptor neuron responding only to the wind stimulus was found to arborise in the antennal lobe. Most projection neurons responded with an enhanced action potential frequency to the combined stimulus. In local interneurons, enhancement, depression, or no change of the responses to the wind stimulus was found when the olfactory stimulus was added. The results suggest that neurons present in the antennal lobe integrate mechanosensory and olfactory input, possibly assisting the moths to orient during up-wind flight towards an odour source.

Action Potentials↗

PubMed2005

Insect-like olfactory adaptations in the terrestrial giant robber crab.

The robber crab (Birgus latro), also known as the coconut crab, is the world's largest land-living arthropod, with a weight reaching 4 kg and a length of over half a meter. Apart from the marine larval stage, this crab is fully terrestrial, and will actually drown if submerged in water. A transition from sea to land raises dramatically new demands on the sensory equipment of an animal. In olfaction, the stimulus changes from hydrophilic molecules in aqueous solution to mainly hydrophobic in the gaseous phase. The olfactory system of land crabs thus represents an excellent opportunity for investigating the effects of the transition from sea to land. Have land crabs come to the same solutions as other terrestrial animals, or is their olfactory sense characterized by unique innovations? Here, we show that the robber crab has evolved an olfactory sense with a high degree of resemblance to the insect system. The similarities extend to physiological, behavioral, and morphological characters. The insect nose of the robber crab is a striking example of convergent evolution and nicely illustrates how similar selection pressures result in similar adaptation.

Animals↗

PubMed2005

Spatio-temporal Ca2+ dynamics of moth olfactory projection neurones.

We studied the Ca2+ dynamics of odour-evoked glomerular patterns in the antennal lobe of the moth Spodoptera littoralis using optical imaging. Here we selectively stained a large population of antennal lobe output neurones, projection neurones, by retrograde filling with FURA-dextran from the inner antennocerebral tract in the protocerebrum. Different plant-associated odorants evoked distributed patterns of activated glomeruli that were odour dependent and repeatable. These patterns were, however, dynamic during the period of odour exposure. Temporal responses differed across glomeruli and were stimulus dependent. Next we examined how the correlations between patterns evoked by different odorants changed with time. Initially, responses to structurally similar compounds were highly correlated, whereas responses to structurally different compounds differed. Within the period of odour exposure (1 s) we found a significant reduction in similarity of responses evoked by different odours, irrespective of initial similarity, whereas trial-to-trial correlations remained high. Our results suggested an ability for coarse classification at the initial encounter with an odour source. With time, however, the discrimination ability increases and structurally similar odours can be distinguished.

Animals↗

PubMed2004

A simple mushroom body in an African scarabid beetle.

This account describes novel mushroom body organization in a coleopteran insect, the African fruit chafer Pachnoda marginata. Each of its prominent mushroom bodies possesses a pair of simple calyces comprising two populations of Kenyon cells, the dendrites of which are organized into a central and an annular zone. Kenyon cells of the central zone extend their dendrites downward and toward the perimeter of the calyx. Their axon-like processes in the pedunculus are densely packed to make up a distinctive shaft of neuropil. Toward the front of the brain, the shafts, one from each calyx, bifurcate to provide a pair of subdivisions in the medial and vertical lobes. Dendrites of Kenyon cells supplying the annular zone extend from the calyx perimeter toward its center. Axons from the annular zones of both calyces together provide a sleeve of axons that ensheaths the two shafts. Sleeve axons bifurcate to provide a second pair of divisions in each of the lobes. These arrangements provide each lobe with a discrete representation of the two Kenyon cell populations of the two calyces. Kenyon cells supplying the central zone have dendritic morphologies reminiscent of class II clawed Kenyon cells that supply the gamma lobes in other taxa. Kenyon cells supplying axons to the sleeve are suggestive of class III Kenyon cell morphologies described from cockroaches and termites. Elaborate intrinsic neurons, comparable to exotic intrinsic neurons in the honey bee gamma lobes, have processes that interact with shaft axons. The present observations suggest that mushroom bodies of Pachnoda represent either a basal organization entirely lacking class I Kenyon cells or an evolutionary modification in which there is no clear morphological distinction of class I and II Kenyon cells. In either case, cellular organization in Pachnoda's mushroom body is simple compared with that of other taxa.

Animals↗

PubMed2004

Odorant-evoked nitric oxide signals in the antennal lobe of Manduca sexta.

The gaseous signaling molecule nitric oxide (NO) can affect the activities of neurons and neural networks in many different systems. The strong expression of NO synthase (NOS) in the primary synaptic neuropil (the antennal lobe in insects and the olfactory bulb in vertebrates) of the olfactory system of most organisms, and the unique spheroidal geometry of olfactory glomeruli in those neuropils, have led to suggestions that NO signaling is important for processing olfactory information. No direct evidence exists, however, that NO signals are produced in olfactory glomeruli. We investigated the production of NO in the antennal lobe of the moth, Manduca sexta, by using immunocytochemistry and real-time optical imaging with a NO-sensitive fluorescent marker, diaminofluorescein diacetate. We confirmed that NOS was expressed in the axons of olfactory receptor neurons projecting to all glomeruli. Soluble guanylyl cyclase, the best characterized target of NO, was found in a subset of postsynaptic antennal lobe neurons that included projection neurons, a small number of GABA-immunoreactive neurons, and a serotonin-immunoreactive neuron. We found that odorant stimulation evoked NO signals that were reproducible and spatially focused. Different odorants evoked spatially distinct patterns of NO production. Increased concentrations of pheromone and plant odorants caused increases in peak signal intensity. Increased concentrations of plant odorants also evoked a dramatic increase in signal area. The results of these experiments show clearly that odorant stimulation can evoke NO production in the olfactory system. The NO signals produced are likely to play an important role in processing olfactory information.

Animals↗

PubMed2003

Spatial representation of odorant structure in the moth antennal lobe: a study of structure-response relationships at low doses.

How odorant structure and concentration are spatially represented within the primary olfactory integration center, the antennal lobe (AL) or olfactory bulb (OB) in invertebrates and vertebrates, respectively, is currently a topic of high interest. Here, we show the spatial representation of odorant structure in the antennal lobe of the moth Spodoptera littoralis by imaging calcium activity evoked by straight chain aliphatic alcohols and aldehydes at low doses. Activity patterns of a given odor were most similar to compounds with the same functional group, differing in chain length by only one carbon atom. A chain length dependency was present as the most activated glomerulus in the lobe shifted from a medial to a lateral position with increasing chain length of the molecule. Statistical analysis revealed that in both classes of chemicals the chain length of the molecule was represented in a similar way. No topographically fixed domains were observed for any of the classes. However, activity patterns evoked by lower chain length molecules were spatially more distinct than patterns evoked by higher chain length molecules. The number of activated glomeruli for both classes of chemicals increased with increasing chain length to reach a maximum at eight or nine C atoms followed by a decrease as the chain length further increased.

Alcohols↗

PubMed2003

Evolution of the olfactory code in the Drosophila melanogaster subgroup.

The Drosophila melanogaster subgroup has been the focus of numerous studies about evolution. We address the question of how the olfactory code has evolved among the nine sister species. By using in vivo electrophysiological measurements, so called single-cell recordings, we have established the ligand affinity of a defined subset of olfactory receptor neurons (ORNs) across all nine species. We show that the olfactory code as relayed by the investigated subset of ORNs is conserved to a striking degree. Distinct shifts in the code have occurred only within the simulans clade. However, these shifts are restricted to an altered tuning profile of the same single ORN type in all three of the simulans siblings and a more drastic change unique to D. sechellia, involving a complete loss of one sensillum type in favour of another. The alterations observed in D. sechellia may represent a novel host-specific adaptation to its sole host, morinda fruit (Morinda citrifolia). The overall high degree of similarity of the code within the subgroup is intriguing when considering the great variety in distributions as well as in habitat and host choice of the siblings, factors that could greatly affect the olfactory system.

Animals↗

PubMed2003

Attractiveness of fruit and flower odorants detected by olfactory receptor neurons in the fruit chafer Pachnoda marginata.

We studied the attraction of the African fruit chafer Pachnoda marginata Drury (Coleoptera: Scarabaeidae) to banana and 34 synthetic plant compounds previously shown to be detected by P. marginata olfactory receptor neurons. The behavioral studies were carried out in a two-choice olfactometer, where the attraction of beetles to lures and controls was monitored in 30-min intervals during whole days. Monitoring of the attraction over time gave additional information when comparing relative attractiveness of different compounds. Seventeen of the test compounds, primarily phenylic compounds, fruit esters, isovaleric acid, acetoin, and some floral or fruit terpenes, were attractive to P. marginata. Compounds showing no attractiveness included green leaf volatiles, lactones. and several alcohols, but also phenylic compounds and esters. One case of blend synergism was demonstrated, as well as some examples of sexual dimorphism in attraction. The significance of certain compounds and receptor neurons for olfactory-guided behavior of phytophagous scarabs is discussed.

Animals↗

PubMed2003

Dose-response characteristics of glomerular activity in the moth antennal lobe.

Odours are represented as unique combinations of activated glomeruli in the antennal lobes of insects. Receptor neurons arborizing in the glomeruli are not only qualitatively selective, but in addition respond to variations in stimulus concentration. As each glomerulus likely represents a single receptor neuron type, optical recordings of calcium changes in insect antennal lobes show how concentration variations affect a large population of afferents. We measured the glomerular responses in the moth Spodoptera littoralis to different concentrations of plant-related odorants. Localized calcium responses were shown to correspond to individual glomeruli. We found that the dynamic range of glomerular responses spanned 3-4 log units of concentration and the most strongly responding glomeruli often reached a plateau at high stimulus doses. Further, we showed that the single most active glomerulus was often not the same across concentrations. However, if the principal glomerulus moved, it was generally to an adjacent or proximal glomerulus. As concentration increased, a higher number of glomeruli became activated. Correlations of glomerular representations of the same compound at different doses decreased as the difference in concentration increased. Moreover, representations evoked by different odorants were more correlated at high than at low doses, which means that the uniqueness of activity patterns decreased with increasing concentration. Thus, if odours are coded as spatial patterns of glomerular activity, as has been suggested, these olfactory codes are not persistent across concentrations.

Acyclic Monoterpenes↗

PubMed2003

Extreme sensitivity in an olfactory system.

We recorded olfactory-induced cardiac responses to evaluate olfactory response thresholds to behaviourally relevant odours in a moth. Specific antennal receptor neurons enable insects to detect biologically meaningful odours such as sex pheromones and host-plant volatiles. The response threshold values demonstrated here are well below anything earlier reported in any organism. A heart response was triggered by less than six molecules of the most efficient odours hitting the antennae of the insect. The behavioural significance of this extreme sensitivity most likely lies in the creation of awareness and readiness to respond behaviourally at higher concentration levels.

Animals↗