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  • 1
    Electronic Resource
    Electronic Resource
    Electrically induced tentacle contraction in the suctorian protozoonTrichophrya collini (1989)
    Springer
    Protoplasma 148 (1989), S. 33-40 
    Details
    ISSN: 1615-6102
    Keywords: Contraction ; Electrical stimulation ; Microtubules ; Suctoria ; Trichophrya
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Extracellular electrical stimulation ofTrichophrya collini induces tentacle contraction. There is an inverse relationship between stimulus duration and voltage in producing a threshold response, and at a set voltage the response is graded depending upon duration of stimulus. With a threshold stimulus (6.3 V, 1,000 ms) the response is restricted to the anodal tentacles, and with increasing stimulus intensity or duration the response spreads to the cathodal and finally the intermediate tentacles. With a stimulus of 15 V, 1,000 ms the mean tentacle length is reduced to 28% of the control within 1.2 s. Recordings using intracellular microelectrodes give resting membrane potentials between −10mV and −40mV. Intracellular hyperpolarizing currents of 1nA and 2nA induce tentacle contraction to 50% and 25% of the control length respectively, but depolarizing currents do not induce contraction. SEM studies show that in the initial stages of contraction, only the central region of the tentacle shaft becomes shortened, but on full contraction shortening involves the whole of the shaft. TEM studies show that on contraction no depolymerization of tentacle axoneme microtubules occurs, but that the entire axoneme passes down into the body cytoplasm. These observations are discussed in relation to the possible mechanisms of tentacle contraction.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01403989
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  • 2
    Electronic Resource
    Electronic Resource
    Asexual reproduction in the suctorianDiscophrya collini (1982)
    Springer
    Protoplasma 111 (1982), S. 195-205 
    Details
    ISSN: 1615-6102
    Keywords: Discophrya ; Evaginative budding ; Microtubules ; Reproduction ; Suctoria
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Discophrya collini reproduces asexually through the formation of a ciliated swarmer by evaginative budding. This process is initiated by the repeated replication of a single subcortical kinetosome to form a kinetosome field. The epiplasm of the multilayered cortex covering this field becomes reduced in thickness and the whole cortex invaginates to produce an internal embryonic cavity. The kinetosomes become organised into rows, and each produces a cilium which projects into the cavity. On completion of the embryonic cavity its walls are extruded through the cavity opening to form an external ciliated swarmer connected to the parent by a thin bridge of cytoplasm. It is suggested that this evagination is induced by a rapid breakdown of supporting microtubules in the cavity wall and the subsequent hydrostatic pressure exerted by the body cytoplasm. The connecting bridge shows no specialised ultrastructural features and separation of swarmer from parent probably is achieved by the active movement of the swarmer. The cytoplasm of the swarmer is similar in structure to that of the adult cell but contains a number of primordia of tentacle axonemes. The infraciliature resembles that of other suctorian swarmers. On settling, the cilia of the swarmer are lost, at least some by resorption, a stalk may be secreted and the axoneme primordia are extended to form functional tentacles.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01281967
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Giant forms of the suctorian ciliateDiscophrya collini (1979)
    Springer
    Protoplasma 100 (1979), S. 125-137 
    Details
    ISSN: 1615-6102
    Keywords: Gigantism ; Macronucleus ; Overfeeding ; Suctoria
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Discophrya collini subjected to high levels of feeding onParamecium caudatum developed giant forms in culture. These take several forms: a single enlarged cell, a giant with attached normal cells or attached giants with normals. All the cells possess functional tentacles. The giant cells show qualitative and quantitative macronuclear changes and an abnormally thickened epiplasm containing membraneous profiles and other aberrant structures. These cells contain kinetosome fields and brood pouches identical to those found during normal swarmer production. It is suggested that the giant complexes are formed by the normal production of swarmers but a failure in their release from the adult, perhaps attributable to the abnormal epiplasm, results in their subsequent metamorphosisin situ. The abnormal epiplasm could be produced by the deposition of myelin body food residues from the cytoplasm. The initial induction of gigantism itself may be related to disruption of the normal growth-division cycle similar to that experienced during natural senescence. Possible mechanisms of this disruption and differences with other suctoria are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01283924
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    Paper (German National Licenses)
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