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Salzman S, Dahake A, Kandalaft W, Valencia-Montoya WA, Calonje M, Specht CD, Raguso RA. Cone humidity is a strong attractant in an obligate cycad pollination system. Curr Biol 2023; 33:1654-1664.e4. [PMID: 37015222 DOI: 10.1016/j.cub.2023.03.021] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2023] [Revised: 03/06/2023] [Accepted: 03/08/2023] [Indexed: 04/05/2023]
Abstract
Studies of pollination biology often focus on visual and olfactory aspects of attraction, with few studies addressing behavioral responses and morphological adaptation to primary metabolic attributes. As part of an in-depth study of obligate nursery pollination of cycads, we find that Rhopalotria furfuracea weevils show a strong physiological response and behavioral orientation to the cone humidity of the host plant Zamia furfuracea in an equally sensitive manner to their responses to Z. furfuracea-produced cone volatiles. Our results demonstrate that weevils can perceive fine-scale differences in relative humidity (RH) and that individuals exhibit a strong behavioral preference for higher RH in binary choice assays. Host plant Z. furfuracea produces a localized cloud of higher than ambient humidity around both pollen and ovulate cones, and R. furfuracea weevils preferentially land at the zone of maximum humidity on ovulate cones, i.e., the cracks between rows of megasporophylls that provide access to the ovules. Moreover, R. furfuracea weevils exhibit striking antennal morphological traits associated with RH perception, suggesting the importance of humidity sensing in the evolution of this insect lineage. Results from this study suggest that humidity functions in a signal-like fashion in this highly specialized pollination system and help to characterize a key pollination-mediating trait in an ancient plant lineage.
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Affiliation(s)
- Shayla Salzman
- Department of Neurobiology and Behavior, Cornell University, Ithaca, NY 14853, USA; School of Integrative Plant Science, Section of Plant Biology and the L.H. Bailey Hortorium, Cornell University, Ithaca, NY 14853, USA.
| | - Ajinkya Dahake
- Department of Neurobiology and Behavior, Cornell University, Ithaca, NY 14853, USA
| | - William Kandalaft
- Department of Neurobiology and Behavior, Cornell University, Ithaca, NY 14853, USA
| | - Wendy A Valencia-Montoya
- Department of Organismic and Evolutionary Biology and Museum of Comparative Zoology, Harvard University, Cambridge, MA 02138, USA
| | | | - Chelsea D Specht
- School of Integrative Plant Science, Section of Plant Biology and the L.H. Bailey Hortorium, Cornell University, Ithaca, NY 14853, USA
| | - Robert A Raguso
- Department of Neurobiology and Behavior, Cornell University, Ithaca, NY 14853, USA
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2
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Dahake A, Jain P, Vogt CC, Kandalaft W, Stroock AD, Raguso RA. A signal-like role for floral humidity in a nocturnal pollination system. Nat Commun 2022; 13:7773. [PMID: 36522313 PMCID: PMC9755274 DOI: 10.1038/s41467-022-35353-8] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2022] [Accepted: 11/29/2022] [Indexed: 12/23/2022] Open
Abstract
Previous studies have considered floral humidity to be an inadvertent consequence of nectar evaporation, which could be exploited as a cue by nectar-seeking pollinators. By contrast, our interdisciplinary study of a night-blooming flower, Datura wrightii, and its hawkmoth pollinator, Manduca sexta, reveals that floral relative humidity acts as a mutually beneficial signal in this system. The distinction between cue- and signal-based functions is illustrated by three experimental findings. First, floral humidity gradients in Datura are nearly ten-fold greater than those reported for other species, and result from active (stomatal conductance) rather than passive (nectar evaporation) processes. These humidity gradients are sustained in the face of wind and are reconstituted within seconds of moth visitation, implying substantial physiological costs to these desert plants. Second, the water balance costs in Datura are compensated through increased visitation by Manduca moths, with concomitant increases in pollen export. We show that moths are innately attracted to humid flowers, even when floral humidity and nectar rewards are experimentally decoupled. Moreover, moths can track minute changes in humidity via antennal hygrosensory sensilla but fail to do so when these sensilla are experimentally occluded. Third, their preference for humid flowers benefits hawkmoths by reducing the energetic costs of flower handling during nectar foraging. Taken together, these findings suggest that floral humidity may function as a signal mediating the final stages of floral choice by hawkmoths, complementing the attractive functions of visual and olfactory signals beyond the floral threshold in this nocturnal plant-pollinator system.
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Affiliation(s)
- Ajinkya Dahake
- grid.5386.8000000041936877XDepartment of Neurobiology and Behavior, Cornell University, Ithaca, NY 14853 USA
| | - Piyush Jain
- grid.5386.8000000041936877XSibley School of Mechanical and Aerospace Engineering, Cornell University, Ithaca, NY 14853 USA
| | - Caleb C. Vogt
- grid.5386.8000000041936877XDepartment of Neurobiology and Behavior, Cornell University, Ithaca, NY 14853 USA
| | - William Kandalaft
- grid.5386.8000000041936877XDepartment of Neurobiology and Behavior, Cornell University, Ithaca, NY 14853 USA
| | - Abraham D. Stroock
- grid.5386.8000000041936877XSmith School of Chemical and Biomolecular Engineering, Cornell University, Ithaca, NY 14853 USA
| | - Robert A. Raguso
- grid.5386.8000000041936877XDepartment of Neurobiology and Behavior, Cornell University, Ithaca, NY 14853 USA
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3
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Harrap MJM, Hempel de Ibarra N, Knowles HD, Whitney HM, Rands SA. Bumblebees can detect floral humidity. J Exp Biol 2021; 224:jeb240861. [PMID: 34161560 PMCID: PMC8246344 DOI: 10.1242/jeb.240861] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2020] [Accepted: 05/10/2021] [Indexed: 11/20/2022]
Abstract
Floral humidity, a region of elevated humidity in the headspace of the flower, occurs in many plant species and may add to their multimodal floral displays. So far, the ability to detect and respond to floral humidity cues has been only established for hawkmoths when they locate and extract nectar while hovering in front of some moth-pollinated flowers. To test whether floral humidity can be used by other more widespread generalist pollinators, we designed artificial flowers that presented biologically relevant levels of humidity similar to those shown by flowering plants. Bumblebees showed a spontaneous preference for flowers that produced higher floral humidity. Furthermore, learning experiments showed that bumblebees are able to use differences in floral humidity to distinguish between rewarding and non-rewarding flowers. Our results indicate that bumblebees are sensitive to different levels of floral humidity. In this way floral humidity can add to the information provided by flowers and could impact pollinator behaviour more significantly than previously thought.
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Affiliation(s)
- Michael J. M. Harrap
- School of Biological Sciences, University of Bristol, Bristol, BS8 1TQ, UK
- Centre for Research in Animal Behaviour, School of Psychology, University of Exeter, Exeter, EX4 4QG, UK
| | - Natalie Hempel de Ibarra
- Centre for Research in Animal Behaviour, School of Psychology, University of Exeter, Exeter, EX4 4QG, UK
| | - Henry D. Knowles
- School of Biological Sciences, University of Bristol, Bristol, BS8 1TQ, UK
- Natural Resources Wales, Maes Newydd, Llandarcy, Neath Port Talbot, SA10 6JQ, UK
| | - Heather M. Whitney
- School of Biological Sciences, University of Bristol, Bristol, BS8 1TQ, UK
| | - Sean A. Rands
- School of Biological Sciences, University of Bristol, Bristol, BS8 1TQ, UK
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4
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Independent processing of increments and decrements in odorant concentration by ON and OFF olfactory receptor neurons. J Comp Physiol A Neuroethol Sens Neural Behav Physiol 2018; 204:873-891. [PMID: 30251036 PMCID: PMC6208657 DOI: 10.1007/s00359-018-1289-6] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2017] [Revised: 09/11/2018] [Accepted: 09/14/2018] [Indexed: 12/21/2022]
Abstract
A salient feature of the insect olfactory system is its ability to detect and interpret simultaneously the identity and concentration of an odorant signal along with the temporal stimulus cues that are essential for accurate odorant tracking. The olfactory system of the cockroach utilizes two parallel pathways for encoding of odorant identity and the moment-to-moment succession of odorant concentrations as well as the rate at which concentration changes. This separation originates at the peripheral level of the ORNs (olfactory receptor neurons) which are localized in basiconic and trichoid sensilla. The graded activity of ORNs in the basiconic sensilla provides the variable for the combinatorial representation of odorant identity. The antagonistically responding ON and OFF ORNs in the trichoid sensilla transmit information about concentration increments and decrements with excitatory signals. Each ON and OFF ORN adjusts its gain for odorant concentration and its rate of change to the temporal dynamics of the odorant signal: as the rate of change diminishes, both ORNs improve their sensitivity for the rate of change at the expense of the sensitivity for the instantaneous concentration. This suggests that the ON and OFF ORNs are optimized to detect minute fluctuations or even creeping changes in odorant concentration.
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Tichy H, Hellwig M, Kallina W. Revisiting Theories of Humidity Transduction: A Focus on Electrophysiological Data. Front Physiol 2017; 8:650. [PMID: 28928673 PMCID: PMC5591946 DOI: 10.3389/fphys.2017.00650] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2017] [Accepted: 08/16/2017] [Indexed: 11/13/2022] Open
Abstract
Understanding the mechanism of humidity transduction calls for experimental data and a theory to interpret the data and design new experiments. A comprehensive theory of humidity transduction must start with agreement on what humidity parameters are measured by hygroreceptors and processed by the brain. Hygroreceptors have been found in cuticular sensilla of a broad range of insect species. Their structural features are far from uniform. Nevertheless, these sensilla always contain an antagonistic pair of a moist cell and a dry cell combined with a thermoreceptive cold cell. The strategy behind this arrangement remains unclear. Three main models of humidity transduction have been proposed. Hygroreceptors could operate as mechanical hygrometers, psychrometers or evaporation detectors. Each mode of action measures a different humidity parameter. Mechanical hygrometers measure the relative humidity, psychrometers indicate the wet-bulb temperature, and evaporimeters refer to the saturation deficit of the air. Here we assess the validity of the different functions by testing specific predictions drawn from each of the models. The effect of air temperature on the responses to humidity stimulation rules out the mechanical hygrometer function, but it supports the psychrometer function and highlights the action as evaporation rate detector. We suggest testing the effect of the flow rate of the air stream used for humidity stimulation. As the wind speed strongly affects the power of evaporation, experiments with changing saturation deficit at different flow rates would improve our knowledge on humidity transduction.
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Affiliation(s)
- Harald Tichy
- Department of Neurobiology, Faculty of Life Sciences, University of ViennaVienna, Austria
| | - Maria Hellwig
- Department of Neurobiology, Faculty of Life Sciences, University of ViennaVienna, Austria
| | - Wolfgang Kallina
- Department of Neurobiology, Faculty of Life Sciences, University of ViennaVienna, Austria
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6
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Tichy H, Kallina W. Sensitivity of honeybee hygroreceptors to slow humidity changes and temporal humidity variation detected in high resolution by mobile measurements. PLoS One 2014; 9:e99032. [PMID: 24901985 PMCID: PMC4047084 DOI: 10.1371/journal.pone.0099032] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2014] [Accepted: 05/09/2014] [Indexed: 12/04/2022] Open
Abstract
The moist cell and the dry cell on the antenna of the male honeybee were exposed to humidities slowly rising and falling at rates between –1.5%/s and +1.5%/s and at varying amplitudes in the 10 to 90% humidity range. The two cells respond to these slow humidity oscillations with oscillations in impulse frequency which depend not only on instantaneous humidity but also on the rate with which humidity changes. The impulse frequency of each cell was plotted as a function of these two parameters and regression planes were fitted to the data points of single oscillation periods. The regression slopes, which estimate sensitivity, rose with the amplitude of humidity oscillations. During large-amplitude oscillations, moist and dry cell sensitivity for instantaneous humidity and its rate of change was high. During small-amplitude oscillations, their sensitivity for both parameters was low, less exactly reflecting humidity fluctuations. Nothing is known about the spatial and temporal humidity variations a honeybee may encounter when flying through natural environments. Microclimatic parameters (absolute humidity, temperature, wind speed) were measured from an automobile traveling through different landscapes of Lower Austria. Landscape type affected extremes and mean values of humidity. Differences between peaks and troughs of humidity fluctuations were generally smaller in open grassy fields or deciduous forests than in edge habitats or forest openings. Overall, fluctuation amplitudes were small. In this part of the stimulus range, hygroreceptor sensitivity is not optimal for encoding instantaneous humidity and the rate of humidity change. It seems that honeybee's hygroreceptors are specialized for detecting large-amplitude fluctuations that are relevant for a specific behavior, namely, maintaining a sufficiently stable state of water balance. The results suggest that optimal sensitivity of both hygroreceptors is shaped not only by humidity oscillation amplitudes but also according to their impact on behavior.
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Affiliation(s)
- Harald Tichy
- Department of Neurobiology, Faculty of Life Sciences, University of Vienna, Vienna, Austria
- * E-mail:
| | - Wolfgang Kallina
- Department of Neurobiology, Faculty of Life Sciences, University of Vienna, Vienna, Austria
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7
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von Arx M. Floral humidity and other indicators of energy rewards in pollination biology. Commun Integr Biol 2013; 6:e22750. [PMID: 23802044 PMCID: PMC3689576 DOI: 10.4161/cib.22750] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2012] [Accepted: 11/01/2012] [Indexed: 01/09/2023] Open
Abstract
Floral traits that correlate with nectar availability or are linked functionally to nectar production carry the potential to enable remote assessment of energy rewards by pollinators. Such floral traits can be considered “honest” in the sense that they convey information about the quality or profitability of a flower to a pollinator. Recently a new sensory channel used in plant-pollinator interactions was identified. We demonstrated that evaporation of water from the nectar itself and the petals create local humidity gradients above Oenothera cespitosa (Onagraceae) flowers. Since these humidity gradients are directly linked to nectar volume, they convey reliable information about nectar rewards to hawkmoth pollinators (Sphingidae). Several studies document a variety of sensory cues that constitute honest signaling between plants and pollinators, and shed light on the central question of when the two parties should communicate honestly. In the following sections, I will comment on different honest signals mediating plant-pollinator interactions, with a special emphasis on our recent findings about floral humidity gradients.
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Affiliation(s)
- Martin von Arx
- Department of Neurobiology and Behavior; Cornell University; Ithaca, NY USA
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8
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Tichy H, Kallina W. The evaporative function of cockroach hygroreceptors. PLoS One 2013; 8:e53998. [PMID: 23342058 PMCID: PMC3546976 DOI: 10.1371/journal.pone.0053998] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/03/2012] [Accepted: 12/07/2012] [Indexed: 11/19/2022] Open
Abstract
Insect hygroreceptors associate as antagonistic pairs of a moist cell and a dry cell together with a cold cell in small cuticular sensilla on the antennae. The mechanisms by which the atmospheric humidity stimulates the hygroreceptive cells remain elusive. Three models for humidity transduction have been proposed in which hygroreceptors operate either as mechanical hygrometers, evaporation detectors or psychrometers. Mechanical hygrometers are assumed to respond to the relative humidity, evaporation detectors to the saturation deficit and psychrometers to the temperature depression (the difference between wet-bulb and dry-bulb temperatures). The models refer to different ways of expressing humidity. This also means, however, that at different temperatures these different types of hygroreceptors indicate very different humidity conditions. The present study tested the adequacy of the three models on the cockroach’s moist and dry cells by determining whether the specific predictions about the temperature-dependence of the humidity responses are indeed observed. While in previous studies stimulation consisted of rapid step-like humidity changes, here we changed humidity slowly and continuously up and down in a sinusoidal fashion. The low rates of change made it possible to measure instantaneous humidity values based on UV-absorption and to assign these values to the hygroreceptive sensillum. The moist cell fitted neither the mechanical hygrometer nor the evaporation detector model: the temperature dependence of its humidity responses could not be attributed to relative humidity or to saturation deficit, respectively. The psychrometer model, however, was verified by the close relationships of the moist cell’s response with the wet-bulb temperature and the dry cell’s response with the dry-bulb temperature. Thus, the hygroreceptors respond to evaporation and the resulting cooling due to the wetness or dryness of the air. The drier the ambient air (absolutely) and the higher the temperature, the greater the evaporative temperature depression and the power to desiccate.
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Affiliation(s)
- Harald Tichy
- Department of Neurobiology, Faculty of Life Sciences, University of Vienna, Vienna, Austria.
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9
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Floral humidity as a reliable sensory cue for profitability assessment by nectar-foraging hawkmoths. Proc Natl Acad Sci U S A 2012; 109:9471-6. [PMID: 22645365 DOI: 10.1073/pnas.1121624109] [Citation(s) in RCA: 89] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Most research on plant-pollinator communication has focused on sensory and behavioral responses to relatively static cues. Floral rewards such as nectar, however, are dynamic, and foraging animals will increase their energetic profit if they can make use of floral cues that more accurately indicate nectar availability. Here we document such a cue--transient humidity gradients--using the night blooming flowers of Oenothera cespitosa (Onagraceae). The headspace of newly opened flowers reaches levels of about 4% above ambient relative humidity due to additive evapotranspirational water loss through petals and water-saturated air from the nectar tube. Floral humidity plumes differ from ambient levels only during the first 30 min after anthesis (before nectar is depleted in wild populations), whereas other floral traits (scent, shape, and color) persist for 12-24 h. Manipulative experiments indicated that floral humidity gradients are mechanistically linked to nectar volume and therefore contain information about energy rewards to floral visitors. Behavioral assays with Hyles lineata (Sphingidae) and artificial flowers with appropriate humidity gradients suggest that these hawkmoth pollinators distinguish between subtle differences in relative humidity when other floral cues are held constant. Moths consistently approached and probed flowers with elevated humidity over those with ambient humidity levels. Because floral humidity gradients are largely produced by the evaporation of nectar itself, they represent condition-informative cues that facilitate remote sensing of floral profitability by discriminating foragers. In a xeric environment, this level of honest communication should be adaptive when plant reproductive success is pollinator limited, due to intense competition for the attention of a specialized pollinator.
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10
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Chown SL, Sørensen JG, Terblanche JS. Water loss in insects: an environmental change perspective. JOURNAL OF INSECT PHYSIOLOGY 2011; 57:1070-84. [PMID: 21640726 DOI: 10.1016/j.jinsphys.2011.05.004] [Citation(s) in RCA: 192] [Impact Index Per Article: 14.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/27/2011] [Revised: 05/06/2011] [Accepted: 05/06/2011] [Indexed: 05/15/2023]
Abstract
In the context of global environmental change much of the focus has been on changing temperatures. However, patterns of rainfall and water availability have also been changing and are expected to continue doing so. In consequence, understanding the responses of insects to water availability is important, especially because it has a pronounced influence on insect activity, distribution patterns, and species richness. Here we therefore provide a critical review of key questions that either are being or need to be addressed in this field. First, an overview of insect behavioural responses to changing humidity conditions and the mechanisms underlying sensing of humidity variation is provided. The primary sensors in insects belong to the temperature receptor protein superfamily of cation channels. Temperature-activated transient receptor potential ion channels, or thermoTRPs, respond to a diverse range of stimuli and may be a primary integrator of sensory information, such as environmental temperature and moisture. Next we touch briefly on the components of water loss, drawing attention to a new, universal model of the water costs of gas exchange and its implications for responses to a warming, and in places drying, world. We also provide an overview of new understanding of the role of the sub-elytral chamber for water conservation, and developments in understanding of the role of cuticular hydrocarbons in preventing water loss. Because of an increasing focus on the molecular basis of responses to dehydration stress we touch briefly on this area, drawing attention to the role of sugars, heat shock proteins, aquaporins, and LEA proteins. Next we consider phenotypic plasticity or acclimation responses in insect water balance after initial exposures to altered humidity, temperature or nutrition. Although beneficial acclimation has been demonstrated in several instances, this is not always the case. Laboratory studies show that responses to selection for enhanced ability to survive water stress do evolve and that genetic variation for traits underlying such responses does exist in many species. However, in others, especially tropical, typically narrowly distributed species, this appears not to be the case. Using the above information we then demonstrate that habitat alteration, climate change, biological invasions, pollution and overexploitation are likely to be having considerable effects on insect populations mediated through physiological responses (or the lack thereof) to water stress, and that these effects may often be non-intuitive.
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Affiliation(s)
- Steven L Chown
- Centre for Invasion Biology, Department of Botany and Zoology, Stellenbosch University, Private Bag X1, Matieland 7602, South Africa.
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11
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Kim AJ, Lazar AA, Slutskiy YB. System identification of Drosophila olfactory sensory neurons. J Comput Neurosci 2011; 30:143-61. [PMID: 20730480 PMCID: PMC3736744 DOI: 10.1007/s10827-010-0265-0] [Citation(s) in RCA: 49] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2010] [Revised: 07/18/2010] [Accepted: 07/26/2010] [Indexed: 10/19/2022]
Abstract
The lack of a deeper understanding of how olfactory sensory neurons (OSNs) encode odors has hindered the progress in understanding the olfactory signal processing in higher brain centers. Here we employ methods of system identification to investigate the encoding of time-varying odor stimuli and their representation for further processing in the spike domain by Drosophila OSNs. In order to apply system identification techniques, we built a novel low-turbulence odor delivery system that allowed us to deliver airborne stimuli in a precise and reproducible fashion. The system provides a 1% tolerance in stimulus reproducibility and an exact control of odor concentration and concentration gradient on a millisecond time scale. Using this novel setup, we recorded and analyzed the in-vivo response of OSNs to a wide range of time-varying odor waveforms. We report for the first time that across trials the response of OR59b OSNs is very precise and reproducible. Further, we empirically show that the response of an OSN depends not only on the concentration, but also on the rate of change of the odor concentration. Moreover, we demonstrate that a two-dimensional (2D) Encoding Manifold in a concentration-concentration gradient space provides a quantitative description of the neuron's response. We then use the white noise system identification methodology to construct one-dimensional (1D) and two-dimensional (2D) Linear-Nonlinear-Poisson (LNP) cascade models of the sensory neuron for a fixed mean odor concentration and fixed contrast. We show that in terms of predicting the intensity rate of the spike train, the 2D LNP model performs on par with the 1D LNP model, with a root mean-square error (RMSE) increase of about 5 to 10%. Surprisingly, we find that for a fixed contrast of the white noise odor waveforms, the nonlinear block of each of the two models changes with the mean input concentration. The shape of the nonlinearities of both the 1D and the 2D LNP model appears to be, for a fixed mean of the odor waveform, independent of the stimulus contrast. This suggests that white noise system identification of Or59b OSNs only depends on the first moment of the odor concentration. Finally, by comparing the 2D Encoding Manifold and the 2D LNP model, we demonstrate that the OSN identification results depend on the particular type of the employed test odor waveforms. This suggests an adaptive neural encoding model for Or59b OSNs that changes its nonlinearity in response to the odor concentration waveforms.
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Affiliation(s)
- Anmo J. Kim
- Department of Electrical Engineering, Columbia University, New York, NY, USA
| | - Aurel A. Lazar
- Department of Electrical Engineering, Columbia University, New York, NY, USA
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12
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Tichy H, Kallina W. Insect hygroreceptor responses to continuous changes in humidity and air pressure. J Neurophysiol 2010; 103:3274-86. [PMID: 20375249 DOI: 10.1152/jn.01043.2009] [Citation(s) in RCA: 48] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The most favored model of humidity transduction views the cuticular wall of insect hygroreceptive sensilla as a hygromechanical transducer. Hygroscopic swelling or shrinking alters the geometry of the wall, deforming the dendritic membranes of the moist and dry cells. The small size the sensilla and their position surrounded by elevated structures creates technical difficulties to mechanically stimulate them by direct contact. The present study investigated hygroreceptors on the antennae of the cockroach and the stick insect. Accurately controlled, homogeneous mechanical input was delivered by modulating air pressure. Both the moist and dry cells responded not only to changes in air pressure but also in the opposite direction, as observed during changes in air humidity. The moist cell's excitatory response to increasing humidity and increasing air pressure implies that swelling of the hygroscopic cuticle compresses the dendrites, and the dry cell's excitatory response to decreasing humidity and decreasing air pressure implies that shrinking of the hygroscopic cuticle expands the dendrites. The moist and dry cells of the stick insect are more sensitive to pressure changes than those of the cockroach, but the responses to air pressure are generally weaker than to humidity. Therefore the hygroreceptive sensilla differ in their physical properties and constitutions. Furthermore, the mechanical parameters associated with homogeneous changes in air pressure on the sensillum surface can only partially account for the responses of the moist and dry cells of both species to humidity stimulation.
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Affiliation(s)
- H Tichy
- Department of Neurobiology, University of Vienna, Althanstrasse 14, 1090 Vienna, Austria
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13
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Rebora M, Piersanti S, Almaas TJ, Gaino E. Hygroreceptors in the larva of Libellula depressa (Odonata: Libellulidae). JOURNAL OF INSECT PHYSIOLOGY 2007; 53:550-8. [PMID: 17433360 DOI: 10.1016/j.jinsphys.2007.02.006] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/15/2006] [Revised: 02/08/2007] [Accepted: 02/19/2007] [Indexed: 05/14/2023]
Abstract
Ultrastructural and electrophysiological (single-cell recordings) investigations were carried out on the coeloconic sensilla borne by the apical antenna of the larvae of Libellula depressa (Odonata: Libellulidae). These sensilla appear as pegs located in pits. One of them is a compound sensillum constituted of two fused pegs in a common pit and the other two are single pegs located in separated pits close to each other. Coeloconic sensilla show position and ultrastructural details very similar to those described in insect hygroreceptors. The electrophysiological recordings on the apical antennae of the last larval instar of L. depressa clearly show the presence of moist and dry cells responding antagonistically to humidity changes. This study gives the first evidence of hygroreceptors in dragonfly larvae and represents the first electrophysiological approach to larval sensilla of aquatic insects. The presence of hygroreceptors in L. depressa larvae is in agreement with the hygropositive response shown by these insects in laboratory and field behavioural experiments.
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Affiliation(s)
- Manuela Rebora
- Dipartimento di Biologia Cellulare e Ambientale, Via Elce di Sotto, 06123 Perugia, Italy.
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14
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Abstract
We present the first systematic study of the response of insect “cold cells” to a variation in the partial pressure of water vapor in ambient air. The cold cells on the antenna of the stick insect respond with an increase in activity when either the temperature or the partial pressure of water vapor is suddenly reduced. This double dependency does not in itself constitute bimodality because it could disappear with the proper choice of parameters involving temperature and humidity. In this study, we demonstrate that the evaporation of a small amount of water from the sensillum surface resulting from a drop in the water vapor pressure—leading to a transient drop in temperature and thus to a brief rise in impulse frequency—is the most plausible explanation for this bimodal response. We also show with an order-of-magnitude calculation that this mechanism is plausible and consistent with the amounts of water vapor potentially present on the sensillum. We hypothesize that a film of moisture collects on the hygroscopic sensillum surface at higher humidity and then tends to evaporate when humidity is lowered. The water might even be bound loosely within the cuticular wall, a situation conceivable in a sensillum that contains two hygroreceptive cells in addition to the cold cell.
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Affiliation(s)
- Harald Tichy
- Faculty of Life Sciences, Department of Neurobiology and Cognition Research, University of Vienna, Althanstrasse 14, 1090 Vienna, Austria.
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Yao CA, Ignell R, Carlson JR. Chemosensory coding by neurons in the coeloconic sensilla of the Drosophila antenna. J Neurosci 2006; 25:8359-67. [PMID: 16162917 PMCID: PMC6725686 DOI: 10.1523/jneurosci.2432-05.2005] [Citation(s) in RCA: 204] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Odor coding is based on the diverse sensitivities and response properties of olfactory receptor neurons (ORNs). In the Drosophila antenna, ORNs are housed in three major morphological types of sensilla. Although investigation of the Drosophila olfactory system has been expanding rapidly, the ORNs in one of these types, the coeloconic sensilla, have been essentially unexplored. We define four functional types of coeloconic sensilla through extracellular physiological recordings. Each type contains at least two neurons, with a total of at least seven distinct ORN classes that vary remarkably in their breadth of tuning. Analysis of 315 odorant-ORN combinations reveals how these neurons sample odor space via both excitation and inhibition. We identify a class of neurons that is narrowly tuned to small amines, and we find humidity detectors that define a cellular basis for hygroreception in Drosophila. The temporal dynamics of responses vary widely, enhancing the potential for complexity in the odor code. Molecular and genetic analysis shows that a broadly tuned ORN, antennal coeloconic 3B (ac3B), requires the odor receptor gene Or35a for its response in vivo. The activity of ac3B is not required for the response of the other ORN within that sensillum, ac3A. The functional analysis presented here, revealing a combination of highly specialized neurons and a broadly tuned ORN, along with the ancient origin of coeloconic sensilla, suggests that the specificities of these ORNs may reflect basic needs of an ancestral insect.
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Affiliation(s)
- C Andrea Yao
- Department of Molecular, Cellular, and Developmental Biology, Yale University, New Haven, Connecticut 06520-8103, USA
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Chown SL, Terblanche JS. Physiological Diversity in Insects: Ecological and Evolutionary Contexts. ADVANCES IN INSECT PHYSIOLOGY 2006; 33:50-152. [PMID: 19212462 PMCID: PMC2638997 DOI: 10.1016/s0065-2806(06)33002-0] [Citation(s) in RCA: 313] [Impact Index Per Article: 17.4] [Reference Citation Analysis] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/09/2023]
Affiliation(s)
- Steven L Chown
- Centre for Invasion Biology, Department of Botany and Zoology, Stellenbosch University, South Africa
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