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  • 1
    ISSN: 1432-1351
    Keywords: Comparative colour vision ; Opponent processes ; Colour computation ; Hymenoptera ; Colour discrimination behaviour
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Behavioural tests were carried out with 9 hymenopteran insect species, which ranked certain sets of coloured stimuli according to their subjective similarity to a previously memorized stimulus. Kendall's τ coefficient is employed for the analysis of correlation between these similarity rankings and the colour distance rankings predicted by various models of neural colour computation. The models are based on the measured spectral sensitivities of photoreceptor colour types and use a variety of simple colour coding systems to derive hypothetical colour distances. The correlation between the predictions of the models and the behavioural results serves as a measure for the likelihood of existence of a colour coding system. In all species, the similarity rankings can be best explained by assuming that colour is coded on a perceptual level by two colour opponent mechanisms. Brightness differences are ignored, indicating that an intensity-coding sub-system is not used in colour discrimination by the insects investigated. The weighting factors of the colour opponent mechanisms differ between species in detail, but not in the principles involved. It is thus possible to employ a standard measure of perceptual colour distance (colour hexagon distance) to predict the capacities of colour discrimination adequately in all the tested insects.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Journal of comparative physiology 151 (1983), S. 477-482 
    ISSN: 1432-1351
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Bees reared under UV-light are less sensitive to long wavelength light in phototaxis experiments than are control bees. Electroretinogram measurements indicate that selective reduction in spectral sensitivity is related to smaller lamina potentials to green light. Histological investigation of synapse frequency of green sensitive photoreceptor terminals reveal a decrease in number of synapses due to the selective wavelength deprivation.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Journal of comparative physiology 147 (1982), S. 365-369 
    ISSN: 1432-1351
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The spectral sensitivity of spontaneous phototactic behavior was tested in short wavelength deprived bees and in control bees kept outdoors. Tests were performed with a y-maze with one branch illuminated, the other dark. The relative sensitivities for the control group were: green to blue to UV = 1∶0.27∶2.14. Short wavelength deprived bees show a distinct decrease in their sensitivity to short wavelengths. The relation green to blue to UV here was 1∶0.22∶0.27. Forager bees from outdooors, short wavelength deprived for 10 days, showed a relation of green to blue to UV of 1∶0.26∶1.04. Electrophysiological investigation of the compound eye using electroretinogram recordings showed no difference between deprived and control animals.
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 1432-1351
    Keywords: Photoreceptors ; Spectral sensitivity ; Colour vision ; Hymenopterans
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Spectral sensitivity functions S(λ) of single photoreceptor cells in 43 different hymenopteran species were measured intracellularly with the fast spectral scan method. The distribution of maximal sensitivity values (λmax) shows 3 major peaks at 340 nm, 430 nm and 535 nm and a small peak at 600 nm. Predictions about the colour vision systems of the different hymenopteran species are derived from the spectral sensitivities by application of a receptor model of colour vision and a model of two colour opponent channels. Most of the species have a trichromatic colour vision system. Although the S(λ) functions are quite similar, the predicted colour discriminability curves differ in their relative height of best discriminability in the UV-blue or bluegreen area of the spectrum, indicating that relatively small differences in the S(λ) functions may have considerable effects on colour discriminability. Four of the hymenopteran insects tested contain an additional R-receptor with maximal sensitivity around 600 nm. The R-receptor of the solitary bee Callonychium petuniae is based on a pigment (P596) with a long λmax, whereas in the sawfly Tenthredo campestris the G-receptor appears to act as filter to a pigment (P570), shifting its λmax value to a longer wavelength and narrowing its bandwidth. Evolutionary and life history constraints (e.g. phylogenetic relatedness, social or solitary life, general or specialized feeding behaviour) appear to have no effect on the S(λ) functions. The only effect is found in UV receptors, for which λmax values at longer wavelengths are found in bees flying predominantly within the forest.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    Journal of comparative physiology 137 (1980), S. 215-231 
    ISSN: 1432-1351
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The properties of bee medulla and lobula neurons were investigated using intracellular recordings and light stimuli of different qualities. The intracellular injection of dye permitted the examination of the structure and position of neurons studied electrophysiologically. Examples of different coding mechanisms are given; transitional stages were also found. 1. Broad band neurons have response/intensity curves for different wavelengths in the same range of intensity; the absolute value of intensity for this range may be different for ON and OFF reactions. 2. Narrow band units show high sensitivity to only a small portion of the spectrum. The maximum sensitivity sometimes lies between the sensitivity maximum of different photoreceptors. 3. Intensity band neurons react to a small intensity range, and show no reaction to light of neighboring intensities. 4. Color specific mechanisms are evident in antagonistic reactions to different colors of the test light. In medullar neurons this component of reaction was phasic, in lobular neurons tonic. 5. Receptive fields of 1/3 of medulla neurons are smaller than 30°; those of lobula neurons are greater than 30°. 6. Some fibres show spatial antagonism: light elicits excitation in one part of the receptive field and inhibition in the other. Fields lack antagonistic center-surround structure. 7. Several neurons are sensitive to movement of a light stimulus. In the medulla these always had small receptive fields, in the lobula wide receptive fields. Directional selectivity occasionally occurred in the lobula.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Springer
    Journal of comparative physiology 170 (1992), S. 267-274 
    ISSN: 1432-1351
    Keywords: Honeybee ; Monopolar cells ; Spectral coding
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary 1. Monopolar cells of the first visual ganglion, the lamina, of the bee were recorded from and stained intracellularly. 2. Several different response types to pulses of spectral light were found. The most common response type hyperpolarized in a phasic-tonic fashion. The tonic hyperpolarizing response frequently decreased gradually, but in some cases increased with lasting illumination. Some cells also gave a transient response to light-OFF. In contrast, one stained and several unstained cells showed depolarizing responses. Five cells exhibited spiking responses under normal physiological conditions. 3. The V/log I-functions were steeper than those of the photoreceptors and, in some cases, had both rising and falling parts with increasing intensities. The spectral sensitivity obtained with the constant response method showed a peak in the green (510–535 nm) in most cells. A series of spectral flashes revealed an additional type with highest sensitivity in UV. Indirect evidence was found in one cell for spectral opponent processing. 4. Two morphological types of monopolar cells were stained. These correspond well to Ribi's (1976) L1 and L2 cells, with some differences in detail. The most frequently stained cell type closely resembles his L2 type. All 3 stained spiking cells were of this type.
    Type of Medium: Electronic Resource
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  • 7
    ISSN: 1432-234X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Long-term light deprivation of the royal pair of Neotermes jouteli during the phase of reproduction leads to a dramatic change in the organization within the compound eye. In a swarming alate, investigated with scanning and transmission electron microscopy, the eye consists of about 200 ommatidia. No differences between male and female eyes are observed. Each ommatidium is composed of a biconvex cornea, a cone of the eucone type, and a rhabdom which is located directly beneath the Semper cells. The rhabdom consists of eight rhabdomeres which are fused along the ommatidial axis. In the central part of the compound eye the rhabdom measures roughly 20 μm in length. Concealed life of the imagines causes a dismantling of the cone and the rhabdom until complete destruction. This is accompanied by an increase in the number of pigment granules and a decrease in the number of mitochondria.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    Springer
    Journal of chemical ecology 23 (1997), S. 2371-2381 
    ISSN: 1573-1561
    Keywords: Termites ; chemical communication ; exocrine gland ; pheromones ; feeding behavior ; feeding aggregation ; phagostimulant
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract The paired labial glands of the French subterranean termite Reticulitermes santonensis Feytaud are located in the thorax. In the head, the glandular ducts join with those of the water sacs. In feeding choice tests with two semicircles of moist filter paper as food, workers of R. santonensis preferred the semicircle treated with labial gland extract compared to the semicircle treated with water (control). The labial gland secretion carries a signal that stimulates gnawing and feeding by termite workers during food exploitation. The extract of the labial gland even elicited feeding behavior when applied without food (on glass plates). The content of the water sacs was not effective as a feeding stimulus and neither were different body parts except for the fat-body. Water sacs are thus not a reservoir for the labial gland secretion, but their contents may serve as a solvent or carrier for the phagostimulant signal. The signal is highly polar, heat-resistant, nonvolatile, and thus very persistent. There is evidence that the signal from the labial gland is not species specific. Instead, it might be part of a general strategy by termites to exploit food sources.
    Type of Medium: Electronic Resource
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