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  • 1
    ISSN: 1432-1939
    Keywords: Key words Aphididae ; Honeydew ; Mutualism ; Ant attendance ; Sugar preferences
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The honeydew composition and production of four aphid species feeding on Tanacetum vulgare, and mutualistic relationships with the ant Lasius niger were studied. In honeydew of Metopeurum fuscoviride and Brachycaudus cardui, xylose, glucose, fructose, sucrose, maltose, melezitose, and raffinose were detected. The proportion of trisaccharides (melezitose, raffinose) ranged between 20% and 35%. No trisaccharides were found in honeydew of Aphis fabae, and honeydew of Macrosiphoniella tanacetaria consisted of only xylose, glucose and sucrose. M. fuscoviride produced by far the largest amounts of honeydew per time unit (880 μg/aphid per hour), followed by B. cardui (223 μg/aphid per hour), A. fabae (133 μg/aphid per hour) and M. tanacetaria (46 μg/aphid per hour). The qualitative and quantitative honeydew production of the aphid species corresponded well with the observed attendance by L. niger. L. niger workers preferred trisaccharides over disaccharides and monosaccharides when these sugars were offered in choice tests. The results are consistent with the ants' preference for M. fuscoviride, which produced the largest amount of honeydew including a considerable proportion of the trisaccharides melezitose and raffinose. The preference of L. niger for B. cardui over A. fabae, both producing similar amounts of honeydew, may be explained by the presence of trisaccharides and the higher total sugar concentration in B. cardui honeydew. M. tanacetaria, which produced only low quantities of honeydew with no trisaccharides was not attended at all by L. niger.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Experimental brain research 16 (1973), S. 354-370 
    ISSN: 1432-1106
    Keywords: Receptive field organisation ; Stimulus specificity ; Cat's superior colliculus
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary 1. The spatial organisation of the excitatory regions of 54 receptive fields from cells in the cat's superior colliculus was studied. Rectangular light bars, dark bars and single contrast borders were used as stimuli. Average response histograms were compiled of the spike discharges elicited from collicular units by these stimuli. 2. A cell would normally respond to the light edge as well as to the dark edge of a stimulus crossing its receptive field. It was possible to describe for a particular unit and a particular direction of stimulus movement the area within the excitatory region of the receptive field responsive to each edge of the rectangular stimuli. In a particular field, these areas were either superimposed (32 units) or spatially separated from one another (22 units). 3. In the receptive fields in which the areas responsive to different edges of a stimulus were spatially offset for stimulus movement in one direction, they also were offset for all other directions of stimulus movement. The direction of this offset changed characteristically with the direction of stimulus movement, revealing a radial symmetry in the organisation of the excitatory region of the receptive field. 4. For units with offset edge-responsive areas, this offset determined the width and contrast of the optimal stimulus for the unit. 5. Receptive fields with superimposed edge-responsive areas are also radially symmetric. The optimal stimuli for units with these receptive fields are either narrow dark slits or narrow light slits. 6. The significance of these properties of collicular cells for coding the position, size and contrast of fast moving stimuli is discussed.
    Type of Medium: Electronic Resource
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