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  • 1
    Electronic Resource
    Electronic Resource
    Pigment movement during light and chromatic adaptation in the retinula cells ofFormica polyctena (Hymenoptera, Formicidae) (1973)
    Springer
    Journal of comparative physiology 86 (1973), S. 125-138 
    Details
    ISSN: 1432-1351
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Description / Table of Contents: Zusammenfassung Die Verteilung der Pigmentgranula in der distalen Region der Retinulazellen vonFormica polyctena wird nach Hell- und chromatischer Adaptation mit elektronenmikroskopischer Methode beschrieben. Im helladaptierten Zustand liegen die Pigmentgranula dicht am Rhabdom und reduzieren so den Lichtfluß innerhalb des Rhabdoms, während im dunkeladaptierten Zustand das Rhabdom von einem großen intrazellulären Vakuolenkranz umgeben ist. Die Intensitätsabhängigkeit unter natürlichen Beleuchtungsbedingungen (morgendliche Dämmerung) weist zum Zeitpunkt des Sonnenaufgangs ein Minimum auf. Wir führen dies auf einen zweiten Adaptationsmechanismus zurück, der infolge der chromatischen Veränderung des Himmelslichtes die Konzentration ungebleichten Sehpigments beeinflußt. Durch chromatische Adaptation mit Spektrallicht der Wellenlängen 337, 447, 591 nm wurde nachgewiesen, daß die beiden schmalen Zellen Nr. 1 und 5 UV-Rezeptoren, die 6 breiten Zellen Grünrezeptoren sind. Dieses Ergebnis steht im Einklang mit elektrophysiologischen und verhaltensphysiologischen Befunden, die beiFormica polyctena ein dichromatisches Parbensehsystem mit UV- und Grünrezeptoren nachgewiesen haben.
    Notes: Summary The distribution of pigment granules in the distal part of the retinula cells ofFromica polyctena is analysed with the electron microscope after light adaptation to natural illumination during sunrise and after selective chromatic adaptation. During the process of light adaptation the pigment granules in the retinula cells move radially towards the rhabdom attenuating the light flux within the light guide structure of the rhabdom. Under natural conditions of light adaptation during sunrise it is found that adaptation by pigment movement is a biphasic process. The pigment granules move closer towards the rhabdom during twilight but suddenly at dawn, they move outwards again and as the sun rises return to the light adapted position. This dramatic break in the pigment adaptation process is explained by postulating that a second adaptation mechanism exists, which regulates the concentration of unbleached photopigment as a result of the chromatic change of sky light during sunrise. Chromatic adaptation experiments with wavelengths 337 nm, 447 nm, and 591 nm at different intensities demonstrate 2 UV-receptors (cell Nos. 1 and 5) and 6 green-receptors (Nos. 2, 3, 4, 6, 7, 8) in each ommatidium.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00702533
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  • 2
    Electronic Resource
    Electronic Resource
    Structure and function of the fused rhabdom (1973)
    Springer
    Journal of comparative physiology 87 (1973), S. 99-135 
    Details
    ISSN: 1432-1351
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary This paper considers the functional significance of fused rhabdoms. Since all rhabdomeres are joined tightly together, the possibility of optical and electrical coupling between retinula cells is greatly enhanced. We study the extent and consequences of this coupling in order to understand the functional significance of fused rhabdoms. Our methods include both theory and intracellular recordings. The results are as follows: Optical Coupling. Because rhabdomeres of different spectral types are fused into a common light guide, the absorption properties of each influence the manner in which light is transmitted along the composite rhabdom structure. 1. Each rhabdomere acts as if it were an absorption filter in front of all others, i.e. rhabdomeres function as lateral absorption filters (Fig. 4). 2. As a consequence of this filtering, the shape of the spectral sensitivity curve for each retinula cell is approximately independent of the amount of light it absorbs, i.e. independent of the rhabdomere's length and concentration of photopigment (Fig. 7). This is in direct contrast to the retinula cells of fly that have spectral sensitivity curves which become progressively flatter as more light is absorbed (Snyder and Pask, 1973). In other words, the flattening of curves by self absorption is prevented by optical coupling. 3. Thus, one functional advantage of the fused rhabdom (due to optical coupling) is that each retinula cell can have a high absolute sensitivity while preserving its spectral identity (narrow spectral sensitivity curves). (Compare Fig. 5 to Fig. 6.) Thus the same receptors can operate in a high sensitivity and in a colour vision system (cf. vertebrate rods and cones).Since all spectral cell types are together in one rhabdom, the animal can have hue discrimination in a small field of view (fine grain colour vision). Thus an individual ommatidium has the potential for providing excellent spectral discrimination. 4. If two cells have photopigments with absorption maxima close together, the maxima of their spectral sensitivity curves are moved further apart (Fig. 8). 5. In the absence of electrical coupling polarization sensitivity (PS) can depend dramatically on wavelength. The spectral composition of the rhabdom, in addition to the direction of the microvilli, profoundly influences the polarization sensitivity vs. wavelength PS (λ) curves of individual retinula cells. This is shown theoretically for the worker bee rhabdom (Fig. 10) where (a) there is a pronounced difference in PS (λ) between cells with orthogonal microvilli and (b) green retinula cells show a large PS in the green while the UV cells show a much smaller PS in the UV (Fig. 13).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01352157
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  • 3
    Electronic Resource
    Electronic Resource
    Polarised light detection in the bee,Apis mellifera (1974)
    Springer
    Journal of comparative physiology 88 (1974), S. 247-270 
    Details
    ISSN: 1432-1351
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The ninth cell in each ommatidium is the only retinula cell that acts as a polarised light detector. The ninth cell is a short retinula cell which is found in the proximal third of the ommatidium. This conclusion is based on the following observations: (1) The most frequently found green sensitive cells have either no or very low sensitivity to polarised light. This is caused by electric coupling of cells with different microvilli orientations. The electric coupling was found to be independent of adaptation state. (2) There are two different types of UV receptors: the more frequently found UV cells also have a distinct spectral sensitivity at longer wavelengths (〉450 nm) and a small polarisation sensitivity. A very rarely recorded UV receptor type with no sensitivity to longer wavelengths (〉450 nm) has a high polarisation sensitivity (average PS = 5, maximal PS = 9). All recordings of these UV cells were made close to the basement membrane in the region of the 9th cell. (3) The short length of the 9th cell, its position in the proximal third of the ommatidium, and the orientation of the microvilli is theoretically consistent with it having a high polarisation sensitivity. To find evidence for the mechanisms underlying the integration of polarisation information coming from the 9th cells, we examined the microvilli orientation of these cells in neighbouring ommatidia in different eye regions. While the medio-ventral eye region contains only one population, with microvilli oriented at 45 ° to the vertical, the dorsal and medio-dorsal eye regions contain two populations lying at 120 ° or 60 ° to each other. The pattern of microvilli orientation is a mirror image in both eyes. This pattern enables an unambiguous determination of the polarisation plane in the dorsal and medio-dorsal eye part if there is a comparison of excitation in the 9th cells of neighbouring ommatidia and/or ommatidia in the two eyes sharing the same field of view. Our conclusions are consistent with v. Frisch's findings on the orientation to polarised light by the worker bee.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00697958
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  • 4
    Electronic Resource
    Electronic Resource
    Spectral sensitivity of monopolar cells in the bee lamina (1974)
    Springer
    Journal of comparative physiology 93 (1974), S. 337-346 
    Details
    ISSN: 1432-1351
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary 1. The intracellularly recorded response of the lamina monopolar cells (MC's) to retinal illumination is a triphasic hyperpolarisation (Fig. 1). Recordings stable enough to allow measurement of a whole series of intensity and spectral runs were obtained from 9 cells. 2. The gain between retinal input and MC output is calculated by comparison of normalised response/log intensity functions, and is found to be about 7 over most of the MC's dynamic range (Fig. 2, 3). 3. The spectral sensitivity of MC's has its maximum at 482 nm and a broad shoulder around 550 nm. Sensitivity is low (20%) in the UV. However, in some MC's there is an increase in sensitivity to the shortest wavelengths tested (316 nm). One MC (No. 7) responded to UV wavelengths at only high intensities and then with a depolarising potential. 4. The interpretation of the MC's spectral sensitivity function is that blue and green receptors supply excitatory inputs to the MC with about equal weighting. UV receptors may supply inhibitory inputs with less weight than those from the blue and green receptors. 5. These spectral sensitivity functions of dark adapted MC's are calculated for an intensity range which is near the threshold of the receptors. For an intensity range which lies around 50% response of the receptors the spectral sensitivity function of the MC's is flat between 300 and 600 nm (if there is no or only small inhibition by the UV receptors) or between 400 and 600 (if the UV inhibition increases strongly with intensity). It is discussed that the spectral response in light adapted MC's may be very different from those of dark adapted MC's.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00606801
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  • 5
    Electronic Resource
    Electronic Resource
    Neurobiology Learning from a fly's memory (2001)
    [s.l.] : Nature Publishing Group
    Nature 411 (2001), S. 433-434 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] Seminal work done over 100 years ago established the basics of memory and learning. But, then as now, studies of learning were hampered by the fact that it is difficult (if not impossible) to distinguish between the formation and the retrieval of memories. Yet it will be important to make this ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/35078184
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  • 6
    Electronic Resource
    Electronic Resource
    Representations of odours and odour mixtures visualized in the honeybee brain (1997)
    [s.l.] : Nature Publishing Group
    Nature 387 (1997), S. 285-288 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] Both the olfactory bulb and the antennal lobe have a glomerular structure with lateral connections between glomeruli, and process incoming signals from broadly tuned odorant receptors1'2'11'13. Recordings of glomerular output neurons in insects and vertebrates indicate distributed odour ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/387285a0
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  • 7
    Electronic Resource
    Electronic Resource
    The concepts of ‘sameness’ and ‘difference’ in an insect (2001)
    [s.l.] : Macmillian Magazines Ltd.
    Nature 410 (2001), S. 930-933 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] Insects process and learn information flexibly to adapt to their environment. The honeybee Apis mellifera constitutes a traditional model for studying learning and memory at behavioural, cellular and molecular levels. Earlier studies focused on elementary associative and non-associative forms ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/35073582
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  • 8
    Electronic Resource
    Electronic Resource
    Neurobiology Cognition by a mini brain (1999)
    [s.l.] : Macmillan Magazines Ltd.
    Nature 400 (1999), S. 718-719 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] We often expect little from small brains and cognitive miracles from big ones. But all brains were once small, in both evolution and development, reaching their respective levels of cognitive function only gradually. Elementary forms of cognition might, then, be present in small brains, and these ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/23371
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  • 9
    Electronic Resource
    Electronic Resource
    Odour coding is bilaterally symmetrical in the antennal lobes of honeybees (Apis mellifera) (1998)
    Oxford, UK : Blackwell Science Ltd
    European journal of neuroscience 10 (1998), S. 0 
    Details
    ISSN: 1460-9568
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: The primary olfactory neuropil, the antennal lobe (AL) in insects, is organized in glomeruli. Glomerular activity patterns are believed to represent the across-fibre pattern of the olfactory code. These patterns depend on an organized innervation from the afferent receptor cells, and interconnections of local interneurons. It is unclear how the complex organization of the AL is achieved ontogenetically. In this study, we measured the functional activity patterns elicited by stimulation with odours in the right and the left AL of the same honeybee (Apis mellifera) using optical imaging of the calcium-sensitive dye calcium green. We show here that these patterns are bilaterally symmetrical (n = 25 bees). This symmetry holds true for all odours tested, irrespective of their role as pheromones or as environmental odours, or whether they were pure substances or complex blends (n = 13 odours). Therefore, we exclude that activity dependent mechanisms local to one AL determine the functional glomerular activity. This identity is genetically predetermined. Alternatively, if activity dependent processes are involved, bilateral connections would have to shape symmetry, or, temporal constraints could lead to identical patterns on both sides due to their common history of odour exposure.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1460-9568.1998.00303.x
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  • 10
    Electronic Resource
    Electronic Resource
    Long- but not medium-term retention of olfactory memories in honeybees is impaired by actinomycin D and anisomycin (1998)
    Oxford, UK : Blackwell Science Ltd
    European journal of neuroscience 10 (1998), S. 0 
    Details
    ISSN: 1460-9568
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Although work in a wide variety of species and paradigms has demonstrated that long-term memory is sensitive to the blocking of protein synthesis, previous studies have suggested that the honeybee might represent an exception to this rule. Retention tested one day after training was not impaired by the inhibition of translation by cycloheximide. Using blockers of either transcription (actinomycin D) or translation (anisomycin), we present experiments that reconcile this unusual finding by testing over longer retention periods. Honeybees were conditioned to associate an odourant with a sucrose reward. Typically, this leads to stable retention over days. However, injection of either drug led to lower retention after 4 days, whereas retention after 2 or sometimes even 3 days was unaffected. This dissociates two forms of memory: a protein synthesis-independent, medium-term memory (up to 3 days) and a protein synthesis-dependent, long-term memory lasting for at least 4 days.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1460-9568.1998.00319.x
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