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  • 1
    Electronic Resource
    Electronic Resource
    Video camera-computer tracking of nematodeCaenorhabditis elegans to record behavioral responses (1985)
    Springer
    Journal of chemical ecology 11 (1985), S. 1239-1247 
    Details
    ISSN: 1573-1561
    Keywords: Caenorhabditis elegans ; nematode ; chemotaxis ; video camera ; microcomputer ; tracking ; carbon dioxide ; oxygen ; klinokinesis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract A new method is used to analyze responses to changes in the concentration of two chemical stimuli. Nematodes are allowed to move around on the surface of a thin layer of agar across which a stream of air blows to carry volatile stimuli. Darkfield illumination provides high-contrast images of the worms which are acquired by a video camera and fed to a microcomputer which is programed to simultaneously track and record the movements and changes in direction of as many as 25 animals. The results are reported in real time. The worms respond to an increase in CO2 concentration by decreasing the number moving and increasing the number of changes of direction. Both responses adapt to steady-state levels in about half a minute. This suggests that they respond by changing the probability of initiating a reversal bout. This observation adds a repellent to the class of stimuli thatC. elegans reponds to by klinokinesis. The resonses to changes in oxygen concentration are somewhat different. Movements and changes in direction both decrease when the oxygen concentration falls and increase when the concentration rises. No adaptation is seen within the one-minute time span observed. This observation provides further evidence that the response to oxygen differs from the response to other chemicals and may be sensed internally. These observations demonstrate that computer tracking is a sensitive method of analyzing animal behavior. It is further demonstrated that a significant response can be detected to a relatively weak stimulus in less than 5 min.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01024112
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  • 2
    Electronic Resource
    Electronic Resource
    Laser microbeam studies of role of amphid receptors in chemosensory behavior of nematodeCaenorhabditis elegans (1986)
    Springer
    Journal of chemical ecology 12 (1986), S. 1339-1347 
    Details
    ISSN: 1573-1561
    Keywords: Caenorhabditis elegans ; nematode ; chemotaxis ; chemoreception ; amphid ; laser microbeam
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract Amphid sensilla, historically considered the primary chemosensory structures of nematodes, were found to be necessary for the detection of only one of the six chemical stimuli that were tested. Only the attraction to cAMP was eliminated by damaging the two lateral lips, which bear the amphid sensilla. The inner labial sensilla, one of which occurs on each of the six lips, are probably the primary receptor structures for the other chemical stimuli. Damaging all six lips, which should destroy all anterior chemosensory input, not only eliminted the attraction to sodium and chloride ions, but reversed the nematodes' response to them. Nematodes with all six lips destroyed showed reversal behavior when exposed to these attractants. Nematodes with damage to all six lips appeared to recover much of their normal chemosensory function within 24 hr after treatment.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01012353
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  • 3
    Electronic Resource
    Electronic Resource
    Theoretical range over which bacteria and nematodes locate plant roots using carbon dioxide (1987)
    Springer
    Journal of chemical ecology 13 (1987), S. 1617-1624 
    Details
    ISSN: 1573-1561
    Keywords: Theory ; chemotaxis ; rhizosphere ; soil ; klinokinesis ; klinotaxis ; nematode ; bacteria ; carbon dioxide ; root
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract A theory used to estimate the smallest relative chemical gradient that is potentially detectable is given approximately byG〉(DCR ν 2t3)−1/2 whereD is the diffusion constant andC the concentration of the stimulus chemical,R is the effective radius of the receptor,ν the velocity of the organism, andt the time period within which the organism measures the concentration. Of these factors, time has the strongest influence. Combining this result with available information on gradients of carbon dioxide around roots and behavior of bacteria and nematodes leads to several conclusions. Bacteria can potentially detect carbon dioxide gradients in the layer of water in contact with the root but not further away. In contrast, plant-parasitic nematodes can potentially detect gradients one meter from a single long root fiber and over 2 m from a plant root mass using klinokinesis. A direct approach using klinotaxis can start a few centimeters from a single root fiber and half a meter from a root mass. These differences are due to differences in the time available to measure the concentrations. Increasing the length of a bacterium could increase its ability to detect gradients by reducing its rotational diffusion. Collimating stimuli that serve to maintain a straight path may provide a means of improving chemotaxis by permitting concentration to be measured for longer times during klinokinesis. More accurate predictions can be made when more precise data are available. The analysis is applicable to a wide variety of other organisms and stimuli.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00980204
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  • 4
    Electronic Resource
    Electronic Resource
    Repellent of root-knot nematodes from exudate of host roots (1989)
    Springer
    Journal of chemical ecology 15 (1989), S. 2445-2455 
    Details
    ISSN: 1573-1561
    Keywords: Root-knot nematode ; Meloidogyne incognita ; root exudate ; bioassay ; chromatography ; repellent ; chemotaxis ; tomato
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract A chemotaxis assay was developed to measure attraction or repulsion of infective juveniles of the root-knot nematodeMeloidogyne incognita to exudates of host roots. The assay was sufficiently sensitive to measure the repellent activity of a 25-μl sample of 7 mM NaCl. In tests of root exudate collected in a variety of ways from a variety of plants, avoidance responses were usually found but attraction was not. Extraction of the exudate from tomato with various organic solvents revealed that the repellent activity was highly polar. On Sephadex G-15 chromatography this exudate separated into two clearly defined peaks with apparent molecular weights of about 500 and 1000 daltons. The faster running peak (larger apparent size) contained much more activity than the other peak. Subsequent analysis of material from the larger peak via HPLC on a C18 column revealed a single peak of repellent activity. None of the chemical fractionations uncovered reproducible attractant activity.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01020375
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  • 5
    Electronic Resource
    Electronic Resource
    Responses of plant-parasitic nematodeMeloidogyne incognita to carbon dioxide determined by video camera-computer tracking (1987)
    Springer
    Journal of chemical ecology 13 (1987), S. 873-888 
    Details
    ISSN: 1573-1561
    Keywords: Meloidogyne incognita ; nematode ; carbon dioxide ; chemotaxis ; video camera ; microcomputer ; tracking ; soil
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract A computer tracking system was used to quantify the responses of infective second-stage juveniles of the plant-parasitic nematodeMeloidogyne incognita to carbon dioxide. A sudden increase in concentration caused an increase in the rate of locomotion and a decrease in the frequency of changes of direction. The threshold was about 0.01 % vol CO2/vol gas when the baseline concentration was very low and 0.05% CO2 when the baseline concentration was 1% CO2. The latter value represents a relative change of 5%. Concentrations above 10% CO2 caused a general decrease in movement. In a second type of experiment, a constant concentration gradient of CO2 was established, and the net movement of the nematodes along the gradient was determined. At low concentrations, the threshold was about 0.02% CO2/cm. At higher concentrations, the threshold gradient was below 0.01% CO2/cm or a relative gradient of less than 1% change/cm. At all concentrations to which nematodes responded they were attracted. The degree of orientation was estimated to be approximately 10% under most conditions. The rate of migration under the most favorable conditions was about 0.7 cm/hr. Three possible functions of the response are discussed: attraction to roots, movement toward optimal depth in soil, and as a collimating stimulus.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01020167
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  • 6
    Electronic Resource
    Electronic Resource
    Computer tracking as a behavioral GC detector: Nematode responses to vapor of host roots (1992)
    Springer
    Journal of chemical ecology 18 (1992), S. 585-592 
    Details
    ISSN: 1573-1561
    Keywords: Root-knot nematode ; Meloidogyne incognita ; root vapor ; bioassay ; gas chromatography ; chemotaxis ; tomato ; carbon dioxide ; oxygen
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract A computer tracking system previously developed for studying the behavioral responses of nematodes to volatile stimuli was modified so that the effluent of a gas chromatograph passed over the nematodes while their behavior was analyzed. Since the behavior of several hundred nematodes can be analyzed simultaneously, this technique has the potential to provide a sensitive assay for behaviorally active fractions from the GC. This potential was tested with infective juveniles of the root-knot nematodeMeloidogyne incognita and vapor from the roots of host tomato plants. Direct injection of 1 ml of vapor led to reproducible responses at times corresponding to nitrogen plus oxygen elution and to carbon dioxide elution. Experiments with pure gases demonstrated responses to oxygen and to carbon dioxide. Attempts were made to find less volatile and less active components by pulling large volumes of vapor through a trap of Tenax GC and subsequently eluting them onto the GC. This approach did not lead to the detection of other activities. We conclude that, other than carbon dioxide, there are no volatile stimuli released from host roots in effective quantities.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00987821
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