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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Journal of comparative physiology 186 (2000), S. 193-203 
    ISSN: 1432-1351
    Keywords: Key wordsEristalis tenax ; Pollen ; Taste hairs ; Contact chemoreception ; Proline
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract The labellar gustatory system of the dronefly Eristalis tenax L. (Syrphidae; Diptera) that enables the fly to discriminate between pollen and nectar is investigated, and the triggering of pollen ingestion is examined. In behavioural preference tests, exhaustively extracted pollen of the sunflower Helianthus annuus is consumed in smaller amounts than untreated pollen, indicating that water-soluble substances are important for acceptance. Dry pollen is preferred over moist pollen in which the grains stick together, suggesting that mechanical properties of the pollen also play a role in its sensory assessment. Electrophysiological studies of the labellar taste hairs reveal that aqueous extracts of pollen (2% w/v) stimulate the salt receptor cell, but not the sugar receptor cell. The response of the water receptor cell remains the same as to pure water (or standard electrolyte, 10 mmol · l−1 KCl). Of the 20 amino acids tested, the salt cell is sensitive only to proline in a submillimolar range. Behavioural experiments support the electrophysiological findings. When KCl is applied at concentrations eliciting salt-cell spike frequencies equal to those produced by pollen extract (which is often accepted), the water receptor cell is inhibited and a pronounced rejection behaviour occurs. This rejection of concentrated salt solution in Eristalis is therefore mainly mediated by the inhibition of the water cell.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Journal of comparative physiology 178 (1996), S. 477-489 
    ISSN: 1432-1351
    Keywords: Bombus terrestris ; Innate colour preferences ; Colour difference ; Colour saturation Colour vision ; Colour perception
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract The innate preferences of inexperienced bumble bees, Bombus terrestris, for floral colour stimuli were studied using artificial flowers. The artificial flowers provided a colour pattern and consisted of a star-shaped corolla and of central colour patches similar to the “nectar guide” of natural flowers. The innate choice behaviour was assessed in terms of the number of approach flights from some distance towards the artificial flowers and the percentage of approach flights terminating in antennal contact with the floral guide. The colours of the floral guide, the corolla and the background were varied. It was shown that the innate flower colour preference in bumble bees has two components. 1. The frequency of approaches from a distance is correlated with the colour difference between the corolla and the background against which it is presented. If the corolla colour was constant but its background colour varied, the relative attractiveness of the corolla increased with its colour difference to the background. The colour difference assessment underlying this behaviour on a perceptual basis can be attained by means of colour opponent coding, a system well-established in Hymenoptera. 2. The frequency of antennal contacts with the floral guides relative to that of approach flights cannot be accounted for by colour opponent coding alone. Whether the approach flights are interrupted, or whether they end in an antennal contact with the “nectar guide” is strongly dependent on the direction (sign) of the colour difference, not only its magnitude. The choice behaviour requires a unique perceptual dimension, possibly that of colour saturation or that of hue perception comparable to components of colour perception in humans.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Journal of comparative physiology 174 (1994), S. 575-579 
    ISSN: 1432-1351
    Keywords: Proboscis extension ; Eristalis ; Wavelength ; specific behaviour ; Colour preference ; Pollen feeding
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract Freshly emerged, inexperienced imagos of the hoverfly Eristalis tenax L. extend their proboscis towards small, yellow colour stimuli, such as anther parts and artificial floral guides. The releasing of this behaviour, which is adapted to pollen feeding, was investigated in behavioural tests using white, UV-reflecting artificial flowers with four small screens illuminated with test stimuli serving as artificial floral guides. The releasing of the innate proboscis extension was tested using monochromatic test lights. Within an intensity range from approx. 5·1011 to approx. 1014 quanta · cm-2· s-1, the flies extended their proboscis only towards green and yellow test lights (approx. 520–600 nm). The inhibition of the innate proboscis extension was tested using mixed light stimuli composed of a yellow monochromatic reference light (560 nm, 1013 quanta·cm-2 -1) and of a monochromatic test light. When the reference light was mixed with ultraviolet or blue test lights, the releasing of the innate proboscis extension was strongly inhibited, whereas admixing green/yellow light slightly promoted it; admixing red light had no effect. The results indicate that the releasing of the innate proboscis extension is mediated by the photoreceptor type R8y. Other receptor types which could cause the inhibition of the proboscis reaction are discussed.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Entomologia experimentalis et applicata 80 (1996), S. 50-53 
    ISSN: 1570-7458
    Keywords: Diptera ; Syrphidae ; colour vision ; pollen surface ; contact chemoreception
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Type of Medium: Electronic Resource
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